1 |
=head1 NAME |
2 |
|
3 |
AnyEvent - the DBI of event loop programming |
4 |
|
5 |
EV, Event, Glib, Tk, Perl, Event::Lib, Irssi, rxvt-unicode, IO::Async, Qt |
6 |
and POE are various supported event loops/environments. |
7 |
|
8 |
=head1 SYNOPSIS |
9 |
|
10 |
use AnyEvent; |
11 |
|
12 |
# if you prefer function calls, look at the AE manpage for |
13 |
# an alternative API. |
14 |
|
15 |
# file handle or descriptor readable |
16 |
my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... }); |
17 |
|
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# one-shot or repeating timers |
19 |
my $w = AnyEvent->timer (after => $seconds, cb => sub { ... }); |
20 |
my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...); |
21 |
|
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print AnyEvent->now; # prints current event loop time |
23 |
print AnyEvent->time; # think Time::HiRes::time or simply CORE::time. |
24 |
|
25 |
# POSIX signal |
26 |
my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... }); |
27 |
|
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# child process exit |
29 |
my $w = AnyEvent->child (pid => $pid, cb => sub { |
30 |
my ($pid, $status) = @_; |
31 |
... |
32 |
}); |
33 |
|
34 |
# called when event loop idle (if applicable) |
35 |
my $w = AnyEvent->idle (cb => sub { ... }); |
36 |
|
37 |
my $w = AnyEvent->condvar; # stores whether a condition was flagged |
38 |
$w->send; # wake up current and all future recv's |
39 |
$w->recv; # enters "main loop" till $condvar gets ->send |
40 |
# use a condvar in callback mode: |
41 |
$w->cb (sub { $_[0]->recv }); |
42 |
|
43 |
=head1 INTRODUCTION/TUTORIAL |
44 |
|
45 |
This manpage is mainly a reference manual. If you are interested |
46 |
in a tutorial or some gentle introduction, have a look at the |
47 |
L<AnyEvent::Intro> manpage. |
48 |
|
49 |
=head1 SUPPORT |
50 |
|
51 |
An FAQ document is available as L<AnyEvent::FAQ>. |
52 |
|
53 |
There also is a mailinglist for discussing all things AnyEvent, and an IRC |
54 |
channel, too. |
55 |
|
56 |
See the AnyEvent project page at the B<Schmorpforge Ta-Sa Software |
57 |
Repository>, at L<http://anyevent.schmorp.de>, for more info. |
58 |
|
59 |
=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT) |
60 |
|
61 |
Glib, POE, IO::Async, Event... CPAN offers event models by the dozen |
62 |
nowadays. So what is different about AnyEvent? |
63 |
|
64 |
Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of |
65 |
policy> and AnyEvent is I<small and efficient>. |
66 |
|
67 |
First and foremost, I<AnyEvent is not an event model> itself, it only |
68 |
interfaces to whatever event model the main program happens to use, in a |
69 |
pragmatic way. For event models and certain classes of immortals alike, |
70 |
the statement "there can only be one" is a bitter reality: In general, |
71 |
only one event loop can be active at the same time in a process. AnyEvent |
72 |
cannot change this, but it can hide the differences between those event |
73 |
loops. |
74 |
|
75 |
The goal of AnyEvent is to offer module authors the ability to do event |
76 |
programming (waiting for I/O or timer events) without subscribing to a |
77 |
religion, a way of living, and most importantly: without forcing your |
78 |
module users into the same thing by forcing them to use the same event |
79 |
model you use. |
80 |
|
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For modules like POE or IO::Async (which is a total misnomer as it is |
82 |
actually doing all I/O I<synchronously>...), using them in your module is |
83 |
like joining a cult: After you join, you are dependent on them and you |
84 |
cannot use anything else, as they are simply incompatible to everything |
85 |
that isn't them. What's worse, all the potential users of your |
86 |
module are I<also> forced to use the same event loop you use. |
87 |
|
88 |
AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works |
89 |
fine. AnyEvent + Tk works fine etc. etc. but none of these work together |
90 |
with the rest: POE + EV? No go. Tk + Event? No go. Again: if your module |
91 |
uses one of those, every user of your module has to use it, too. But if |
92 |
your module uses AnyEvent, it works transparently with all event models it |
93 |
supports (including stuff like IO::Async, as long as those use one of the |
94 |
supported event loops. It is easy to add new event loops to AnyEvent, too, |
95 |
so it is future-proof). |
96 |
|
97 |
In addition to being free of having to use I<the one and only true event |
98 |
model>, AnyEvent also is free of bloat and policy: with POE or similar |
99 |
modules, you get an enormous amount of code and strict rules you have to |
100 |
follow. AnyEvent, on the other hand, is lean and to the point, by only |
101 |
offering the functionality that is necessary, in as thin as a wrapper as |
102 |
technically possible. |
103 |
|
104 |
Of course, AnyEvent comes with a big (and fully optional!) toolbox |
105 |
of useful functionality, such as an asynchronous DNS resolver, 100% |
106 |
non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms |
107 |
such as Windows) and lots of real-world knowledge and workarounds for |
108 |
platform bugs and differences. |
109 |
|
110 |
Now, if you I<do want> lots of policy (this can arguably be somewhat |
111 |
useful) and you want to force your users to use the one and only event |
112 |
model, you should I<not> use this module. |
113 |
|
114 |
=head1 DESCRIPTION |
115 |
|
116 |
L<AnyEvent> provides a uniform interface to various event loops. This |
117 |
allows module authors to use event loop functionality without forcing |
118 |
module users to use a specific event loop implementation (since more |
119 |
than one event loop cannot coexist peacefully). |
120 |
|
121 |
The interface itself is vaguely similar, but not identical to the L<Event> |
122 |
module. |
123 |
|
124 |
During the first call of any watcher-creation method, the module tries |
125 |
to detect the currently loaded event loop by probing whether one of the |
126 |
following modules is already loaded: L<EV>, L<AnyEvent::Loop>, |
127 |
L<Event>, L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>. The first one |
128 |
found is used. If none are detected, the module tries to load the first |
129 |
four modules in the order given; but note that if L<EV> is not |
130 |
available, the pure-perl L<AnyEvent::Loop> should always work, so |
131 |
the other two are not normally tried. |
132 |
|
133 |
Because AnyEvent first checks for modules that are already loaded, loading |
134 |
an event model explicitly before first using AnyEvent will likely make |
135 |
that model the default. For example: |
136 |
|
137 |
use Tk; |
138 |
use AnyEvent; |
139 |
|
140 |
# .. AnyEvent will likely default to Tk |
141 |
|
142 |
The I<likely> means that, if any module loads another event model and |
143 |
starts using it, all bets are off - this case should be very rare though, |
144 |
as very few modules hardcode event loops without announcing this very |
145 |
loudly. |
146 |
|
147 |
The pure-perl implementation of AnyEvent is called C<AnyEvent::Loop>. Like |
148 |
other event modules you can load it explicitly and enjoy the high |
149 |
availability of that event loop :) |
150 |
|
151 |
=head1 WATCHERS |
152 |
|
153 |
AnyEvent has the central concept of a I<watcher>, which is an object that |
154 |
stores relevant data for each kind of event you are waiting for, such as |
155 |
the callback to call, the file handle to watch, etc. |
156 |
|
157 |
These watchers are normal Perl objects with normal Perl lifetime. After |
158 |
creating a watcher it will immediately "watch" for events and invoke the |
159 |
callback when the event occurs (of course, only when the event model |
160 |
is in control). |
161 |
|
162 |
Note that B<callbacks must not permanently change global variables> |
163 |
potentially in use by the event loop (such as C<$_> or C<$[>) and that B<< |
164 |
callbacks must not C<die> >>. The former is good programming practice in |
165 |
Perl and the latter stems from the fact that exception handling differs |
166 |
widely between event loops. |
167 |
|
168 |
To disable a watcher you have to destroy it (e.g. by setting the |
169 |
variable you store it in to C<undef> or otherwise deleting all references |
170 |
to it). |
171 |
|
172 |
All watchers are created by calling a method on the C<AnyEvent> class. |
173 |
|
174 |
Many watchers either are used with "recursion" (repeating timers for |
175 |
example), or need to refer to their watcher object in other ways. |
176 |
|
177 |
One way to achieve that is this pattern: |
178 |
|
179 |
my $w; $w = AnyEvent->type (arg => value ..., cb => sub { |
180 |
# you can use $w here, for example to undef it |
181 |
undef $w; |
182 |
}); |
183 |
|
184 |
Note that C<my $w; $w => combination. This is necessary because in Perl, |
185 |
my variables are only visible after the statement in which they are |
186 |
declared. |
187 |
|
188 |
=head2 I/O WATCHERS |
189 |
|
190 |
$w = AnyEvent->io ( |
191 |
fh => <filehandle_or_fileno>, |
192 |
poll => <"r" or "w">, |
193 |
cb => <callback>, |
194 |
); |
195 |
|
196 |
You can create an I/O watcher by calling the C<< AnyEvent->io >> method |
197 |
with the following mandatory key-value pairs as arguments: |
198 |
|
199 |
C<fh> is the Perl I<file handle> (or a naked file descriptor) to watch |
200 |
for events (AnyEvent might or might not keep a reference to this file |
201 |
handle). Note that only file handles pointing to things for which |
202 |
non-blocking operation makes sense are allowed. This includes sockets, |
203 |
most character devices, pipes, fifos and so on, but not for example files |
204 |
or block devices. |
205 |
|
206 |
C<poll> must be a string that is either C<r> or C<w>, which creates a |
207 |
watcher waiting for "r"eadable or "w"ritable events, respectively. |
208 |
|
209 |
C<cb> is the callback to invoke each time the file handle becomes ready. |
210 |
|
211 |
Although the callback might get passed parameters, their value and |
212 |
presence is undefined and you cannot rely on them. Portable AnyEvent |
213 |
callbacks cannot use arguments passed to I/O watcher callbacks. |
214 |
|
215 |
The I/O watcher might use the underlying file descriptor or a copy of it. |
216 |
You must not close a file handle as long as any watcher is active on the |
217 |
underlying file descriptor. |
218 |
|
219 |
Some event loops issue spurious readiness notifications, so you should |
220 |
always use non-blocking calls when reading/writing from/to your file |
221 |
handles. |
222 |
|
223 |
Example: wait for readability of STDIN, then read a line and disable the |
224 |
watcher. |
225 |
|
226 |
my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub { |
227 |
chomp (my $input = <STDIN>); |
228 |
warn "read: $input\n"; |
229 |
undef $w; |
230 |
}); |
231 |
|
232 |
=head2 TIME WATCHERS |
233 |
|
234 |
$w = AnyEvent->timer (after => <seconds>, cb => <callback>); |
235 |
|
236 |
$w = AnyEvent->timer ( |
237 |
after => <fractional_seconds>, |
238 |
interval => <fractional_seconds>, |
239 |
cb => <callback>, |
240 |
); |
241 |
|
242 |
You can create a time watcher by calling the C<< AnyEvent->timer >> |
243 |
method with the following mandatory arguments: |
244 |
|
245 |
C<after> specifies after how many seconds (fractional values are |
246 |
supported) the callback should be invoked. C<cb> is the callback to invoke |
247 |
in that case. |
248 |
|
249 |
Although the callback might get passed parameters, their value and |
250 |
presence is undefined and you cannot rely on them. Portable AnyEvent |
251 |
callbacks cannot use arguments passed to time watcher callbacks. |
252 |
|
253 |
The callback will normally be invoked only once. If you specify another |
254 |
parameter, C<interval>, as a strictly positive number (> 0), then the |
255 |
callback will be invoked regularly at that interval (in fractional |
256 |
seconds) after the first invocation. If C<interval> is specified with a |
257 |
false value, then it is treated as if it were not specified at all. |
258 |
|
259 |
The callback will be rescheduled before invoking the callback, but no |
260 |
attempt is made to avoid timer drift in most backends, so the interval is |
261 |
only approximate. |
262 |
|
263 |
Example: fire an event after 7.7 seconds. |
264 |
|
265 |
my $w = AnyEvent->timer (after => 7.7, cb => sub { |
266 |
warn "timeout\n"; |
267 |
}); |
268 |
|
269 |
# to cancel the timer: |
270 |
undef $w; |
271 |
|
272 |
Example 2: fire an event after 0.5 seconds, then roughly every second. |
273 |
|
274 |
my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub { |
275 |
warn "timeout\n"; |
276 |
}; |
277 |
|
278 |
=head3 TIMING ISSUES |
279 |
|
280 |
There are two ways to handle timers: based on real time (relative, "fire |
281 |
in 10 seconds") and based on wallclock time (absolute, "fire at 12 |
282 |
o'clock"). |
283 |
|
284 |
While most event loops expect timers to specified in a relative way, they |
285 |
use absolute time internally. This makes a difference when your clock |
286 |
"jumps", for example, when ntp decides to set your clock backwards from |
287 |
the wrong date of 2014-01-01 to 2008-01-01, a watcher that is supposed to |
288 |
fire "after a second" might actually take six years to finally fire. |
289 |
|
290 |
AnyEvent cannot compensate for this. The only event loop that is conscious |
291 |
of these issues is L<EV>, which offers both relative (ev_timer, based |
292 |
on true relative time) and absolute (ev_periodic, based on wallclock time) |
293 |
timers. |
294 |
|
295 |
AnyEvent always prefers relative timers, if available, matching the |
296 |
AnyEvent API. |
297 |
|
298 |
AnyEvent has two additional methods that return the "current time": |
299 |
|
300 |
=over 4 |
301 |
|
302 |
=item AnyEvent->time |
303 |
|
304 |
This returns the "current wallclock time" as a fractional number of |
305 |
seconds since the Epoch (the same thing as C<time> or C<Time::HiRes::time> |
306 |
return, and the result is guaranteed to be compatible with those). |
307 |
|
308 |
It progresses independently of any event loop processing, i.e. each call |
309 |
will check the system clock, which usually gets updated frequently. |
310 |
|
311 |
=item AnyEvent->now |
312 |
|
313 |
This also returns the "current wallclock time", but unlike C<time>, above, |
314 |
this value might change only once per event loop iteration, depending on |
315 |
the event loop (most return the same time as C<time>, above). This is the |
316 |
time that AnyEvent's timers get scheduled against. |
317 |
|
318 |
I<In almost all cases (in all cases if you don't care), this is the |
319 |
function to call when you want to know the current time.> |
320 |
|
321 |
This function is also often faster then C<< AnyEvent->time >>, and |
322 |
thus the preferred method if you want some timestamp (for example, |
323 |
L<AnyEvent::Handle> uses this to update its activity timeouts). |
324 |
|
325 |
The rest of this section is only of relevance if you try to be very exact |
326 |
with your timing; you can skip it without a bad conscience. |
327 |
|
328 |
For a practical example of when these times differ, consider L<Event::Lib> |
329 |
and L<EV> and the following set-up: |
330 |
|
331 |
The event loop is running and has just invoked one of your callbacks at |
332 |
time=500 (assume no other callbacks delay processing). In your callback, |
333 |
you wait a second by executing C<sleep 1> (blocking the process for a |
334 |
second) and then (at time=501) you create a relative timer that fires |
335 |
after three seconds. |
336 |
|
337 |
With L<Event::Lib>, C<< AnyEvent->time >> and C<< AnyEvent->now >> will |
338 |
both return C<501>, because that is the current time, and the timer will |
339 |
be scheduled to fire at time=504 (C<501> + C<3>). |
340 |
|
341 |
With L<EV>, C<< AnyEvent->time >> returns C<501> (as that is the current |
342 |
time), but C<< AnyEvent->now >> returns C<500>, as that is the time the |
343 |
last event processing phase started. With L<EV>, your timer gets scheduled |
344 |
to run at time=503 (C<500> + C<3>). |
345 |
|
346 |
In one sense, L<Event::Lib> is more exact, as it uses the current time |
347 |
regardless of any delays introduced by event processing. However, most |
348 |
callbacks do not expect large delays in processing, so this causes a |
349 |
higher drift (and a lot more system calls to get the current time). |
350 |
|
351 |
In another sense, L<EV> is more exact, as your timer will be scheduled at |
352 |
the same time, regardless of how long event processing actually took. |
353 |
|
354 |
In either case, if you care (and in most cases, you don't), then you |
355 |
can get whatever behaviour you want with any event loop, by taking the |
356 |
difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into |
357 |
account. |
358 |
|
359 |
=item AnyEvent->now_update |
360 |
|
361 |
Some event loops (such as L<EV> or L<AnyEvent::Loop>) cache the current |
362 |
time for each loop iteration (see the discussion of L<< AnyEvent->now >>, |
363 |
above). |
364 |
|
365 |
When a callback runs for a long time (or when the process sleeps), then |
366 |
this "current" time will differ substantially from the real time, which |
367 |
might affect timers and time-outs. |
368 |
|
369 |
When this is the case, you can call this method, which will update the |
370 |
event loop's idea of "current time". |
371 |
|
372 |
A typical example would be a script in a web server (e.g. C<mod_perl>) - |
373 |
when mod_perl executes the script, then the event loop will have the wrong |
374 |
idea about the "current time" (being potentially far in the past, when the |
375 |
script ran the last time). In that case you should arrange a call to C<< |
376 |
AnyEvent->now_update >> each time the web server process wakes up again |
377 |
(e.g. at the start of your script, or in a handler). |
378 |
|
379 |
Note that updating the time I<might> cause some events to be handled. |
380 |
|
381 |
=back |
382 |
|
383 |
=head2 SIGNAL WATCHERS |
384 |
|
385 |
$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>); |
386 |
|
387 |
You can watch for signals using a signal watcher, C<signal> is the signal |
388 |
I<name> in uppercase and without any C<SIG> prefix, C<cb> is the Perl |
389 |
callback to be invoked whenever a signal occurs. |
390 |
|
391 |
Although the callback might get passed parameters, their value and |
392 |
presence is undefined and you cannot rely on them. Portable AnyEvent |
393 |
callbacks cannot use arguments passed to signal watcher callbacks. |
394 |
|
395 |
Multiple signal occurrences can be clumped together into one callback |
396 |
invocation, and callback invocation will be synchronous. Synchronous means |
397 |
that it might take a while until the signal gets handled by the process, |
398 |
but it is guaranteed not to interrupt any other callbacks. |
399 |
|
400 |
The main advantage of using these watchers is that you can share a signal |
401 |
between multiple watchers, and AnyEvent will ensure that signals will not |
402 |
interrupt your program at bad times. |
403 |
|
404 |
This watcher might use C<%SIG> (depending on the event loop used), |
405 |
so programs overwriting those signals directly will likely not work |
406 |
correctly. |
407 |
|
408 |
Example: exit on SIGINT |
409 |
|
410 |
my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 }); |
411 |
|
412 |
=head3 Restart Behaviour |
413 |
|
414 |
While restart behaviour is up to the event loop implementation, most will |
415 |
not restart syscalls (that includes L<Async::Interrupt> and AnyEvent's |
416 |
pure perl implementation). |
417 |
|
418 |
=head3 Safe/Unsafe Signals |
419 |
|
420 |
Perl signals can be either "safe" (synchronous to opcode handling) or |
421 |
"unsafe" (asynchronous) - the former might get delayed indefinitely, the |
422 |
latter might corrupt your memory. |
423 |
|
424 |
AnyEvent signal handlers are, in addition, synchronous to the event loop, |
425 |
i.e. they will not interrupt your running perl program but will only be |
426 |
called as part of the normal event handling (just like timer, I/O etc. |
427 |
callbacks, too). |
428 |
|
429 |
=head3 Signal Races, Delays and Workarounds |
430 |
|
431 |
Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching |
432 |
callbacks to signals in a generic way, which is a pity, as you cannot |
433 |
do race-free signal handling in perl, requiring C libraries for |
434 |
this. AnyEvent will try to do its best, which means in some cases, |
435 |
signals will be delayed. The maximum time a signal might be delayed is |
436 |
specified in C<$AnyEvent::MAX_SIGNAL_LATENCY> (default: 10 seconds). This |
437 |
variable can be changed only before the first signal watcher is created, |
438 |
and should be left alone otherwise. This variable determines how often |
439 |
AnyEvent polls for signals (in case a wake-up was missed). Higher values |
440 |
will cause fewer spurious wake-ups, which is better for power and CPU |
441 |
saving. |
442 |
|
443 |
All these problems can be avoided by installing the optional |
444 |
L<Async::Interrupt> module, which works with most event loops. It will not |
445 |
work with inherently broken event loops such as L<Event> or L<Event::Lib> |
446 |
(and not with L<POE> currently, as POE does its own workaround with |
447 |
one-second latency). For those, you just have to suffer the delays. |
448 |
|
449 |
=head2 CHILD PROCESS WATCHERS |
450 |
|
451 |
$w = AnyEvent->child (pid => <process id>, cb => <callback>); |
452 |
|
453 |
You can also watch for a child process exit and catch its exit status. |
454 |
|
455 |
The child process is specified by the C<pid> argument (on some backends, |
456 |
using C<0> watches for any child process exit, on others this will |
457 |
croak). The watcher will be triggered only when the child process has |
458 |
finished and an exit status is available, not on any trace events |
459 |
(stopped/continued). |
460 |
|
461 |
The callback will be called with the pid and exit status (as returned by |
462 |
waitpid), so unlike other watcher types, you I<can> rely on child watcher |
463 |
callback arguments. |
464 |
|
465 |
This watcher type works by installing a signal handler for C<SIGCHLD>, |
466 |
and since it cannot be shared, nothing else should use SIGCHLD or reap |
467 |
random child processes (waiting for specific child processes, e.g. inside |
468 |
C<system>, is just fine). |
469 |
|
470 |
There is a slight catch to child watchers, however: you usually start them |
471 |
I<after> the child process was created, and this means the process could |
472 |
have exited already (and no SIGCHLD will be sent anymore). |
473 |
|
474 |
Not all event models handle this correctly (neither POE nor IO::Async do, |
475 |
see their AnyEvent::Impl manpages for details), but even for event models |
476 |
that I<do> handle this correctly, they usually need to be loaded before |
477 |
the process exits (i.e. before you fork in the first place). AnyEvent's |
478 |
pure perl event loop handles all cases correctly regardless of when you |
479 |
start the watcher. |
480 |
|
481 |
This means you cannot create a child watcher as the very first |
482 |
thing in an AnyEvent program, you I<have> to create at least one |
483 |
watcher before you C<fork> the child (alternatively, you can call |
484 |
C<AnyEvent::detect>). |
485 |
|
486 |
As most event loops do not support waiting for child events, they will be |
487 |
emulated by AnyEvent in most cases, in which case the latency and race |
488 |
problems mentioned in the description of signal watchers apply. |
489 |
|
490 |
Example: fork a process and wait for it |
491 |
|
492 |
my $done = AnyEvent->condvar; |
493 |
|
494 |
my $pid = fork or exit 5; |
495 |
|
496 |
my $w = AnyEvent->child ( |
497 |
pid => $pid, |
498 |
cb => sub { |
499 |
my ($pid, $status) = @_; |
500 |
warn "pid $pid exited with status $status"; |
501 |
$done->send; |
502 |
}, |
503 |
); |
504 |
|
505 |
# do something else, then wait for process exit |
506 |
$done->recv; |
507 |
|
508 |
=head2 IDLE WATCHERS |
509 |
|
510 |
$w = AnyEvent->idle (cb => <callback>); |
511 |
|
512 |
This will repeatedly invoke the callback after the process becomes idle, |
513 |
until either the watcher is destroyed or new events have been detected. |
514 |
|
515 |
Idle watchers are useful when there is a need to do something, but it |
516 |
is not so important (or wise) to do it instantly. The callback will be |
517 |
invoked only when there is "nothing better to do", which is usually |
518 |
defined as "all outstanding events have been handled and no new events |
519 |
have been detected". That means that idle watchers ideally get invoked |
520 |
when the event loop has just polled for new events but none have been |
521 |
detected. Instead of blocking to wait for more events, the idle watchers |
522 |
will be invoked. |
523 |
|
524 |
Unfortunately, most event loops do not really support idle watchers (only |
525 |
EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent |
526 |
will simply call the callback "from time to time". |
527 |
|
528 |
Example: read lines from STDIN, but only process them when the |
529 |
program is otherwise idle: |
530 |
|
531 |
my @lines; # read data |
532 |
my $idle_w; |
533 |
my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub { |
534 |
push @lines, scalar <STDIN>; |
535 |
|
536 |
# start an idle watcher, if not already done |
537 |
$idle_w ||= AnyEvent->idle (cb => sub { |
538 |
# handle only one line, when there are lines left |
539 |
if (my $line = shift @lines) { |
540 |
print "handled when idle: $line"; |
541 |
} else { |
542 |
# otherwise disable the idle watcher again |
543 |
undef $idle_w; |
544 |
} |
545 |
}); |
546 |
}); |
547 |
|
548 |
=head2 CONDITION VARIABLES |
549 |
|
550 |
$cv = AnyEvent->condvar; |
551 |
|
552 |
$cv->send (<list>); |
553 |
my @res = $cv->recv; |
554 |
|
555 |
If you are familiar with some event loops you will know that all of them |
556 |
require you to run some blocking "loop", "run" or similar function that |
557 |
will actively watch for new events and call your callbacks. |
558 |
|
559 |
AnyEvent is slightly different: it expects somebody else to run the event |
560 |
loop and will only block when necessary (usually when told by the user). |
561 |
|
562 |
The tool to do that is called a "condition variable", so called because |
563 |
they represent a condition that must become true. |
564 |
|
565 |
Now is probably a good time to look at the examples further below. |
566 |
|
567 |
Condition variables can be created by calling the C<< AnyEvent->condvar |
568 |
>> method, usually without arguments. The only argument pair allowed is |
569 |
C<cb>, which specifies a callback to be called when the condition variable |
570 |
becomes true, with the condition variable as the first argument (but not |
571 |
the results). |
572 |
|
573 |
After creation, the condition variable is "false" until it becomes "true" |
574 |
by calling the C<send> method (or calling the condition variable as if it |
575 |
were a callback, read about the caveats in the description for the C<< |
576 |
->send >> method). |
577 |
|
578 |
Since condition variables are the most complex part of the AnyEvent API, here are |
579 |
some different mental models of what they are - pick the ones you can connect to: |
580 |
|
581 |
=over 4 |
582 |
|
583 |
=item * Condition variables are like callbacks - you can call them (and pass them instead |
584 |
of callbacks). Unlike callbacks however, you can also wait for them to be called. |
585 |
|
586 |
=item * Condition variables are signals - one side can emit or send them, |
587 |
the other side can wait for them, or install a handler that is called when |
588 |
the signal fires. |
589 |
|
590 |
=item * Condition variables are like "Merge Points" - points in your program |
591 |
where you merge multiple independent results/control flows into one. |
592 |
|
593 |
=item * Condition variables represent a transaction - functions that start |
594 |
some kind of transaction can return them, leaving the caller the choice |
595 |
between waiting in a blocking fashion, or setting a callback. |
596 |
|
597 |
=item * Condition variables represent future values, or promises to deliver |
598 |
some result, long before the result is available. |
599 |
|
600 |
=back |
601 |
|
602 |
Condition variables are very useful to signal that something has finished, |
603 |
for example, if you write a module that does asynchronous http requests, |
604 |
then a condition variable would be the ideal candidate to signal the |
605 |
availability of results. The user can either act when the callback is |
606 |
called or can synchronously C<< ->recv >> for the results. |
607 |
|
608 |
You can also use them to simulate traditional event loops - for example, |
609 |
you can block your main program until an event occurs - for example, you |
610 |
could C<< ->recv >> in your main program until the user clicks the Quit |
611 |
button of your app, which would C<< ->send >> the "quit" event. |
612 |
|
613 |
Note that condition variables recurse into the event loop - if you have |
614 |
two pieces of code that call C<< ->recv >> in a round-robin fashion, you |
615 |
lose. Therefore, condition variables are good to export to your caller, but |
616 |
you should avoid making a blocking wait yourself, at least in callbacks, |
617 |
as this asks for trouble. |
618 |
|
619 |
Condition variables are represented by hash refs in perl, and the keys |
620 |
used by AnyEvent itself are all named C<_ae_XXX> to make subclassing |
621 |
easy (it is often useful to build your own transaction class on top of |
622 |
AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call |
623 |
its C<new> method in your own C<new> method. |
624 |
|
625 |
There are two "sides" to a condition variable - the "producer side" which |
626 |
eventually calls C<< -> send >>, and the "consumer side", which waits |
627 |
for the send to occur. |
628 |
|
629 |
Example: wait for a timer. |
630 |
|
631 |
# condition: "wait till the timer is fired" |
632 |
my $timer_fired = AnyEvent->condvar; |
633 |
|
634 |
# create the timer - we could wait for, say |
635 |
# a handle becomign ready, or even an |
636 |
# AnyEvent::HTTP request to finish, but |
637 |
# in this case, we simply use a timer: |
638 |
my $w = AnyEvent->timer ( |
639 |
after => 1, |
640 |
cb => sub { $timer_fired->send }, |
641 |
); |
642 |
|
643 |
# this "blocks" (while handling events) till the callback |
644 |
# calls ->send |
645 |
$timer_fired->recv; |
646 |
|
647 |
Example: wait for a timer, but take advantage of the fact that condition |
648 |
variables are also callable directly. |
649 |
|
650 |
my $done = AnyEvent->condvar; |
651 |
my $delay = AnyEvent->timer (after => 5, cb => $done); |
652 |
$done->recv; |
653 |
|
654 |
Example: Imagine an API that returns a condvar and doesn't support |
655 |
callbacks. This is how you make a synchronous call, for example from |
656 |
the main program: |
657 |
|
658 |
use AnyEvent::CouchDB; |
659 |
|
660 |
... |
661 |
|
662 |
my @info = $couchdb->info->recv; |
663 |
|
664 |
And this is how you would just set a callback to be called whenever the |
665 |
results are available: |
666 |
|
667 |
$couchdb->info->cb (sub { |
668 |
my @info = $_[0]->recv; |
669 |
}); |
670 |
|
671 |
=head3 METHODS FOR PRODUCERS |
672 |
|
673 |
These methods should only be used by the producing side, i.e. the |
674 |
code/module that eventually sends the signal. Note that it is also |
675 |
the producer side which creates the condvar in most cases, but it isn't |
676 |
uncommon for the consumer to create it as well. |
677 |
|
678 |
=over 4 |
679 |
|
680 |
=item $cv->send (...) |
681 |
|
682 |
Flag the condition as ready - a running C<< ->recv >> and all further |
683 |
calls to C<recv> will (eventually) return after this method has been |
684 |
called. If nobody is waiting the send will be remembered. |
685 |
|
686 |
If a callback has been set on the condition variable, it is called |
687 |
immediately from within send. |
688 |
|
689 |
Any arguments passed to the C<send> call will be returned by all |
690 |
future C<< ->recv >> calls. |
691 |
|
692 |
Condition variables are overloaded so one can call them directly (as if |
693 |
they were a code reference). Calling them directly is the same as calling |
694 |
C<send>. |
695 |
|
696 |
=item $cv->croak ($error) |
697 |
|
698 |
Similar to send, but causes all calls to C<< ->recv >> to invoke |
699 |
C<Carp::croak> with the given error message/object/scalar. |
700 |
|
701 |
This can be used to signal any errors to the condition variable |
702 |
user/consumer. Doing it this way instead of calling C<croak> directly |
703 |
delays the error detection, but has the overwhelming advantage that it |
704 |
diagnoses the error at the place where the result is expected, and not |
705 |
deep in some event callback with no connection to the actual code causing |
706 |
the problem. |
707 |
|
708 |
=item $cv->begin ([group callback]) |
709 |
|
710 |
=item $cv->end |
711 |
|
712 |
These two methods can be used to combine many transactions/events into |
713 |
one. For example, a function that pings many hosts in parallel might want |
714 |
to use a condition variable for the whole process. |
715 |
|
716 |
Every call to C<< ->begin >> will increment a counter, and every call to |
717 |
C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end |
718 |
>>, the (last) callback passed to C<begin> will be executed, passing the |
719 |
condvar as first argument. That callback is I<supposed> to call C<< ->send |
720 |
>>, but that is not required. If no group callback was set, C<send> will |
721 |
be called without any arguments. |
722 |
|
723 |
You can think of C<< $cv->send >> giving you an OR condition (one call |
724 |
sends), while C<< $cv->begin >> and C<< $cv->end >> giving you an AND |
725 |
condition (all C<begin> calls must be C<end>'ed before the condvar sends). |
726 |
|
727 |
Let's start with a simple example: you have two I/O watchers (for example, |
728 |
STDOUT and STDERR for a program), and you want to wait for both streams to |
729 |
close before activating a condvar: |
730 |
|
731 |
my $cv = AnyEvent->condvar; |
732 |
|
733 |
$cv->begin; # first watcher |
734 |
my $w1 = AnyEvent->io (fh => $fh1, cb => sub { |
735 |
defined sysread $fh1, my $buf, 4096 |
736 |
or $cv->end; |
737 |
}); |
738 |
|
739 |
$cv->begin; # second watcher |
740 |
my $w2 = AnyEvent->io (fh => $fh2, cb => sub { |
741 |
defined sysread $fh2, my $buf, 4096 |
742 |
or $cv->end; |
743 |
}); |
744 |
|
745 |
$cv->recv; |
746 |
|
747 |
This works because for every event source (EOF on file handle), there is |
748 |
one call to C<begin>, so the condvar waits for all calls to C<end> before |
749 |
sending. |
750 |
|
751 |
The ping example mentioned above is slightly more complicated, as the |
752 |
there are results to be passwd back, and the number of tasks that are |
753 |
begun can potentially be zero: |
754 |
|
755 |
my $cv = AnyEvent->condvar; |
756 |
|
757 |
my %result; |
758 |
$cv->begin (sub { shift->send (\%result) }); |
759 |
|
760 |
for my $host (@list_of_hosts) { |
761 |
$cv->begin; |
762 |
ping_host_then_call_callback $host, sub { |
763 |
$result{$host} = ...; |
764 |
$cv->end; |
765 |
}; |
766 |
} |
767 |
|
768 |
$cv->end; |
769 |
|
770 |
This code fragment supposedly pings a number of hosts and calls |
771 |
C<send> after results for all then have have been gathered - in any |
772 |
order. To achieve this, the code issues a call to C<begin> when it starts |
773 |
each ping request and calls C<end> when it has received some result for |
774 |
it. Since C<begin> and C<end> only maintain a counter, the order in which |
775 |
results arrive is not relevant. |
776 |
|
777 |
There is an additional bracketing call to C<begin> and C<end> outside the |
778 |
loop, which serves two important purposes: first, it sets the callback |
779 |
to be called once the counter reaches C<0>, and second, it ensures that |
780 |
C<send> is called even when C<no> hosts are being pinged (the loop |
781 |
doesn't execute once). |
782 |
|
783 |
This is the general pattern when you "fan out" into multiple (but |
784 |
potentially zero) subrequests: use an outer C<begin>/C<end> pair to set |
785 |
the callback and ensure C<end> is called at least once, and then, for each |
786 |
subrequest you start, call C<begin> and for each subrequest you finish, |
787 |
call C<end>. |
788 |
|
789 |
=back |
790 |
|
791 |
=head3 METHODS FOR CONSUMERS |
792 |
|
793 |
These methods should only be used by the consuming side, i.e. the |
794 |
code awaits the condition. |
795 |
|
796 |
=over 4 |
797 |
|
798 |
=item $cv->recv |
799 |
|
800 |
Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak |
801 |
>> methods have been called on C<$cv>, while servicing other watchers |
802 |
normally. |
803 |
|
804 |
You can only wait once on a condition - additional calls are valid but |
805 |
will return immediately. |
806 |
|
807 |
If an error condition has been set by calling C<< ->croak >>, then this |
808 |
function will call C<croak>. |
809 |
|
810 |
In list context, all parameters passed to C<send> will be returned, |
811 |
in scalar context only the first one will be returned. |
812 |
|
813 |
Note that doing a blocking wait in a callback is not supported by any |
814 |
event loop, that is, recursive invocation of a blocking C<< ->recv |
815 |
>> is not allowed, and the C<recv> call will C<croak> if such a |
816 |
condition is detected. This condition can be slightly loosened by using |
817 |
L<Coro::AnyEvent>, which allows you to do a blocking C<< ->recv >> from |
818 |
any thread that doesn't run the event loop itself. |
819 |
|
820 |
Not all event models support a blocking wait - some die in that case |
821 |
(programs might want to do that to stay interactive), so I<if you are |
822 |
using this from a module, never require a blocking wait>. Instead, let the |
823 |
caller decide whether the call will block or not (for example, by coupling |
824 |
condition variables with some kind of request results and supporting |
825 |
callbacks so the caller knows that getting the result will not block, |
826 |
while still supporting blocking waits if the caller so desires). |
827 |
|
828 |
You can ensure that C<< ->recv >> never blocks by setting a callback and |
829 |
only calling C<< ->recv >> from within that callback (or at a later |
830 |
time). This will work even when the event loop does not support blocking |
831 |
waits otherwise. |
832 |
|
833 |
=item $bool = $cv->ready |
834 |
|
835 |
Returns true when the condition is "true", i.e. whether C<send> or |
836 |
C<croak> have been called. |
837 |
|
838 |
=item $cb = $cv->cb ($cb->($cv)) |
839 |
|
840 |
This is a mutator function that returns the callback set and optionally |
841 |
replaces it before doing so. |
842 |
|
843 |
The callback will be called when the condition becomes "true", i.e. when |
844 |
C<send> or C<croak> are called, with the only argument being the |
845 |
condition variable itself. If the condition is already true, the |
846 |
callback is called immediately when it is set. Calling C<recv> inside |
847 |
the callback or at any later time is guaranteed not to block. |
848 |
|
849 |
=back |
850 |
|
851 |
=head1 SUPPORTED EVENT LOOPS/BACKENDS |
852 |
|
853 |
The available backend classes are (every class has its own manpage): |
854 |
|
855 |
=over 4 |
856 |
|
857 |
=item Backends that are autoprobed when no other event loop can be found. |
858 |
|
859 |
EV is the preferred backend when no other event loop seems to be in |
860 |
use. If EV is not installed, then AnyEvent will fall back to its own |
861 |
pure-perl implementation, which is available everywhere as it comes with |
862 |
AnyEvent itself. |
863 |
|
864 |
AnyEvent::Impl::EV based on EV (interface to libev, best choice). |
865 |
AnyEvent::Impl::Perl pure-perl AnyEvent::Loop, fast and portable. |
866 |
|
867 |
=item Backends that are transparently being picked up when they are used. |
868 |
|
869 |
These will be used if they are already loaded when the first watcher |
870 |
is created, in which case it is assumed that the application is using |
871 |
them. This means that AnyEvent will automatically pick the right backend |
872 |
when the main program loads an event module before anything starts to |
873 |
create watchers. Nothing special needs to be done by the main program. |
874 |
|
875 |
AnyEvent::Impl::Event based on Event, very stable, few glitches. |
876 |
AnyEvent::Impl::Glib based on Glib, slow but very stable. |
877 |
AnyEvent::Impl::Tk based on Tk, very broken. |
878 |
AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse. |
879 |
AnyEvent::Impl::POE based on POE, very slow, some limitations. |
880 |
AnyEvent::Impl::Irssi used when running within irssi. |
881 |
AnyEvent::Impl::IOAsync based on IO::Async. |
882 |
AnyEvent::Impl::Cocoa based on Cocoa::EventLoop. |
883 |
AnyEvent::Impl::FLTK based on FLTK. |
884 |
|
885 |
=item Backends with special needs. |
886 |
|
887 |
Qt requires the Qt::Application to be instantiated first, but will |
888 |
otherwise be picked up automatically. As long as the main program |
889 |
instantiates the application before any AnyEvent watchers are created, |
890 |
everything should just work. |
891 |
|
892 |
AnyEvent::Impl::Qt based on Qt. |
893 |
|
894 |
=item Event loops that are indirectly supported via other backends. |
895 |
|
896 |
Some event loops can be supported via other modules: |
897 |
|
898 |
There is no direct support for WxWidgets (L<Wx>) or L<Prima>. |
899 |
|
900 |
B<WxWidgets> has no support for watching file handles. However, you can |
901 |
use WxWidgets through the POE adaptor, as POE has a Wx backend that simply |
902 |
polls 20 times per second, which was considered to be too horrible to even |
903 |
consider for AnyEvent. |
904 |
|
905 |
B<Prima> is not supported as nobody seems to be using it, but it has a POE |
906 |
backend, so it can be supported through POE. |
907 |
|
908 |
AnyEvent knows about both L<Prima> and L<Wx>, however, and will try to |
909 |
load L<POE> when detecting them, in the hope that POE will pick them up, |
910 |
in which case everything will be automatic. |
911 |
|
912 |
=back |
913 |
|
914 |
=head1 GLOBAL VARIABLES AND FUNCTIONS |
915 |
|
916 |
These are not normally required to use AnyEvent, but can be useful to |
917 |
write AnyEvent extension modules. |
918 |
|
919 |
=over 4 |
920 |
|
921 |
=item $AnyEvent::MODEL |
922 |
|
923 |
Contains C<undef> until the first watcher is being created, before the |
924 |
backend has been autodetected. |
925 |
|
926 |
Afterwards it contains the event model that is being used, which is the |
927 |
name of the Perl class implementing the model. This class is usually one |
928 |
of the C<AnyEvent::Impl::xxx> modules, but can be any other class in the |
929 |
case AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode> it |
930 |
will be C<urxvt::anyevent>). |
931 |
|
932 |
=item AnyEvent::detect |
933 |
|
934 |
Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model |
935 |
if necessary. You should only call this function right before you would |
936 |
have created an AnyEvent watcher anyway, that is, as late as possible at |
937 |
runtime, and not e.g. during initialisation of your module. |
938 |
|
939 |
If you need to do some initialisation before AnyEvent watchers are |
940 |
created, use C<post_detect>. |
941 |
|
942 |
=item $guard = AnyEvent::post_detect { BLOCK } |
943 |
|
944 |
Arranges for the code block to be executed as soon as the event model is |
945 |
autodetected (or immediately if that has already happened). |
946 |
|
947 |
The block will be executed I<after> the actual backend has been detected |
948 |
(C<$AnyEvent::MODEL> is set), but I<before> any watchers have been |
949 |
created, so it is possible to e.g. patch C<@AnyEvent::ISA> or do |
950 |
other initialisations - see the sources of L<AnyEvent::Strict> or |
951 |
L<AnyEvent::AIO> to see how this is used. |
952 |
|
953 |
The most common usage is to create some global watchers, without forcing |
954 |
event module detection too early, for example, L<AnyEvent::AIO> creates |
955 |
and installs the global L<IO::AIO> watcher in a C<post_detect> block to |
956 |
avoid autodetecting the event module at load time. |
957 |
|
958 |
If called in scalar or list context, then it creates and returns an object |
959 |
that automatically removes the callback again when it is destroyed (or |
960 |
C<undef> when the hook was immediately executed). See L<AnyEvent::AIO> for |
961 |
a case where this is useful. |
962 |
|
963 |
Example: Create a watcher for the IO::AIO module and store it in |
964 |
C<$WATCHER>, but do so only do so after the event loop is initialised. |
965 |
|
966 |
our WATCHER; |
967 |
|
968 |
my $guard = AnyEvent::post_detect { |
969 |
$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb); |
970 |
}; |
971 |
|
972 |
# the ||= is important in case post_detect immediately runs the block, |
973 |
# as to not clobber the newly-created watcher. assigning both watcher and |
974 |
# post_detect guard to the same variable has the advantage of users being |
975 |
# able to just C<undef $WATCHER> if the watcher causes them grief. |
976 |
|
977 |
$WATCHER ||= $guard; |
978 |
|
979 |
=item @AnyEvent::post_detect |
980 |
|
981 |
If there are any code references in this array (you can C<push> to it |
982 |
before or after loading AnyEvent), then they will be called directly |
983 |
after the event loop has been chosen. |
984 |
|
985 |
You should check C<$AnyEvent::MODEL> before adding to this array, though: |
986 |
if it is defined then the event loop has already been detected, and the |
987 |
array will be ignored. |
988 |
|
989 |
Best use C<AnyEvent::post_detect { BLOCK }> when your application allows |
990 |
it, as it takes care of these details. |
991 |
|
992 |
This variable is mainly useful for modules that can do something useful |
993 |
when AnyEvent is used and thus want to know when it is initialised, but do |
994 |
not need to even load it by default. This array provides the means to hook |
995 |
into AnyEvent passively, without loading it. |
996 |
|
997 |
Example: To load Coro::AnyEvent whenever Coro and AnyEvent are used |
998 |
together, you could put this into Coro (this is the actual code used by |
999 |
Coro to accomplish this): |
1000 |
|
1001 |
if (defined $AnyEvent::MODEL) { |
1002 |
# AnyEvent already initialised, so load Coro::AnyEvent |
1003 |
require Coro::AnyEvent; |
1004 |
} else { |
1005 |
# AnyEvent not yet initialised, so make sure to load Coro::AnyEvent |
1006 |
# as soon as it is |
1007 |
push @AnyEvent::post_detect, sub { require Coro::AnyEvent }; |
1008 |
} |
1009 |
|
1010 |
=item AnyEvent::postpone { BLOCK } |
1011 |
|
1012 |
Arranges for the block to be executed as soon as possible, but not before |
1013 |
the call itself returns. In practise, the block will be executed just |
1014 |
before the event loop polls for new events, or shortly afterwards. |
1015 |
|
1016 |
This function never returns anything (to make the C<return postpone { ... |
1017 |
}> idiom more useful. |
1018 |
|
1019 |
To understand the usefulness of this function, consider a function that |
1020 |
asynchronously does something for you and returns some transaction |
1021 |
object or guard to let you cancel the operation. For example, |
1022 |
C<AnyEvent::Socket::tcp_connect>: |
1023 |
|
1024 |
# start a conenction attempt unless one is active |
1025 |
$self->{connect_guard} ||= AnyEvent::Socket::tcp_connect "www.example.net", 80, sub { |
1026 |
delete $self->{connect_guard}; |
1027 |
... |
1028 |
}; |
1029 |
|
1030 |
Imagine that this function could instantly call the callback, for |
1031 |
example, because it detects an obvious error such as a negative port |
1032 |
number. Invoking the callback before the function returns causes problems |
1033 |
however: the callback will be called and will try to delete the guard |
1034 |
object. But since the function hasn't returned yet, there is nothing to |
1035 |
delete. When the function eventually returns it will assign the guard |
1036 |
object to C<< $self->{connect_guard} >>, where it will likely never be |
1037 |
deleted, so the program thinks it is still trying to connect. |
1038 |
|
1039 |
This is where C<AnyEvent::postpone> should be used. Instead of calling the |
1040 |
callback directly on error: |
1041 |
|
1042 |
$cb->(undef), return # signal error to callback, BAD! |
1043 |
if $some_error_condition; |
1044 |
|
1045 |
It should use C<postpone>: |
1046 |
|
1047 |
AnyEvent::postpone { $cb->(undef) }, return # signal error to callback, later |
1048 |
if $some_error_condition; |
1049 |
|
1050 |
=back |
1051 |
|
1052 |
=head1 WHAT TO DO IN A MODULE |
1053 |
|
1054 |
As a module author, you should C<use AnyEvent> and call AnyEvent methods |
1055 |
freely, but you should not load a specific event module or rely on it. |
1056 |
|
1057 |
Be careful when you create watchers in the module body - AnyEvent will |
1058 |
decide which event module to use as soon as the first method is called, so |
1059 |
by calling AnyEvent in your module body you force the user of your module |
1060 |
to load the event module first. |
1061 |
|
1062 |
Never call C<< ->recv >> on a condition variable unless you I<know> that |
1063 |
the C<< ->send >> method has been called on it already. This is |
1064 |
because it will stall the whole program, and the whole point of using |
1065 |
events is to stay interactive. |
1066 |
|
1067 |
It is fine, however, to call C<< ->recv >> when the user of your module |
1068 |
requests it (i.e. if you create a http request object ad have a method |
1069 |
called C<results> that returns the results, it may call C<< ->recv >> |
1070 |
freely, as the user of your module knows what she is doing. Always). |
1071 |
|
1072 |
=head1 WHAT TO DO IN THE MAIN PROGRAM |
1073 |
|
1074 |
There will always be a single main program - the only place that should |
1075 |
dictate which event model to use. |
1076 |
|
1077 |
If the program is not event-based, it need not do anything special, even |
1078 |
when it depends on a module that uses an AnyEvent. If the program itself |
1079 |
uses AnyEvent, but does not care which event loop is used, all it needs |
1080 |
to do is C<use AnyEvent>. In either case, AnyEvent will choose the best |
1081 |
available loop implementation. |
1082 |
|
1083 |
If the main program relies on a specific event model - for example, in |
1084 |
Gtk2 programs you have to rely on the Glib module - you should load the |
1085 |
event module before loading AnyEvent or any module that uses it: generally |
1086 |
speaking, you should load it as early as possible. The reason is that |
1087 |
modules might create watchers when they are loaded, and AnyEvent will |
1088 |
decide on the event model to use as soon as it creates watchers, and it |
1089 |
might choose the wrong one unless you load the correct one yourself. |
1090 |
|
1091 |
You can chose to use a pure-perl implementation by loading the |
1092 |
C<AnyEvent::Loop> module, which gives you similar behaviour |
1093 |
everywhere, but letting AnyEvent chose the model is generally better. |
1094 |
|
1095 |
=head2 MAINLOOP EMULATION |
1096 |
|
1097 |
Sometimes (often for short test scripts, or even standalone programs who |
1098 |
only want to use AnyEvent), you do not want to run a specific event loop. |
1099 |
|
1100 |
In that case, you can use a condition variable like this: |
1101 |
|
1102 |
AnyEvent->condvar->recv; |
1103 |
|
1104 |
This has the effect of entering the event loop and looping forever. |
1105 |
|
1106 |
Note that usually your program has some exit condition, in which case |
1107 |
it is better to use the "traditional" approach of storing a condition |
1108 |
variable somewhere, waiting for it, and sending it when the program should |
1109 |
exit cleanly. |
1110 |
|
1111 |
|
1112 |
=head1 OTHER MODULES |
1113 |
|
1114 |
The following is a non-exhaustive list of additional modules that use |
1115 |
AnyEvent as a client and can therefore be mixed easily with other AnyEvent |
1116 |
modules and other event loops in the same program. Some of the modules |
1117 |
come as part of AnyEvent, the others are available via CPAN. |
1118 |
|
1119 |
=over 4 |
1120 |
|
1121 |
=item L<AnyEvent::Util> |
1122 |
|
1123 |
Contains various utility functions that replace often-used blocking |
1124 |
functions such as C<inet_aton> with event/callback-based versions. |
1125 |
|
1126 |
=item L<AnyEvent::Socket> |
1127 |
|
1128 |
Provides various utility functions for (internet protocol) sockets, |
1129 |
addresses and name resolution. Also functions to create non-blocking tcp |
1130 |
connections or tcp servers, with IPv6 and SRV record support and more. |
1131 |
|
1132 |
=item L<AnyEvent::Handle> |
1133 |
|
1134 |
Provide read and write buffers, manages watchers for reads and writes, |
1135 |
supports raw and formatted I/O, I/O queued and fully transparent and |
1136 |
non-blocking SSL/TLS (via L<AnyEvent::TLS>). |
1137 |
|
1138 |
=item L<AnyEvent::DNS> |
1139 |
|
1140 |
Provides rich asynchronous DNS resolver capabilities. |
1141 |
|
1142 |
=item L<AnyEvent::HTTP>, L<AnyEvent::IRC>, L<AnyEvent::XMPP>, L<AnyEvent::GPSD>, L<AnyEvent::IGS>, L<AnyEvent::FCP> |
1143 |
|
1144 |
Implement event-based interfaces to the protocols of the same name (for |
1145 |
the curious, IGS is the International Go Server and FCP is the Freenet |
1146 |
Client Protocol). |
1147 |
|
1148 |
=item L<AnyEvent::Handle::UDP> |
1149 |
|
1150 |
Here be danger! |
1151 |
|
1152 |
As Pauli would put it, "Not only is it not right, it's not even wrong!" - |
1153 |
there are so many things wrong with AnyEvent::Handle::UDP, most notably |
1154 |
its use of a stream-based API with a protocol that isn't streamable, that |
1155 |
the only way to improve it is to delete it. |
1156 |
|
1157 |
It features data corruption (but typically only under load) and general |
1158 |
confusion. On top, the author is not only clueless about UDP but also |
1159 |
fact-resistant - some gems of his understanding: "connect doesn't work |
1160 |
with UDP", "UDP packets are not IP packets", "UDP only has datagrams, not |
1161 |
packets", "I don't need to implement proper error checking as UDP doesn't |
1162 |
support error checking" and so on - he doesn't even understand what's |
1163 |
wrong with his module when it is explained to him. |
1164 |
|
1165 |
=item L<AnyEvent::DBI> |
1166 |
|
1167 |
Executes L<DBI> requests asynchronously in a proxy process for you, |
1168 |
notifying you in an event-based way when the operation is finished. |
1169 |
|
1170 |
=item L<AnyEvent::AIO> |
1171 |
|
1172 |
Truly asynchronous (as opposed to non-blocking) I/O, should be in the |
1173 |
toolbox of every event programmer. AnyEvent::AIO transparently fuses |
1174 |
L<IO::AIO> and AnyEvent together, giving AnyEvent access to event-based |
1175 |
file I/O, and much more. |
1176 |
|
1177 |
=item L<AnyEvent::HTTPD> |
1178 |
|
1179 |
A simple embedded webserver. |
1180 |
|
1181 |
=item L<AnyEvent::FastPing> |
1182 |
|
1183 |
The fastest ping in the west. |
1184 |
|
1185 |
=item L<Coro> |
1186 |
|
1187 |
Has special support for AnyEvent via L<Coro::AnyEvent>. |
1188 |
|
1189 |
=back |
1190 |
|
1191 |
=cut |
1192 |
|
1193 |
package AnyEvent; |
1194 |
|
1195 |
# basically a tuned-down version of common::sense |
1196 |
sub common_sense { |
1197 |
# from common:.sense 3.4 |
1198 |
${^WARNING_BITS} ^= ${^WARNING_BITS} ^ "\x3c\x3f\x33\x00\x0f\xf0\x0f\xc0\xf0\xfc\x33\x00"; |
1199 |
# use strict vars subs - NO UTF-8, as Util.pm doesn't like this atm. (uts46data.pl) |
1200 |
$^H |= 0x00000600; |
1201 |
} |
1202 |
|
1203 |
BEGIN { AnyEvent::common_sense } |
1204 |
|
1205 |
use Carp (); |
1206 |
|
1207 |
our $VERSION = '5.34'; |
1208 |
our $MODEL; |
1209 |
|
1210 |
our $AUTOLOAD; |
1211 |
our @ISA; |
1212 |
|
1213 |
our @REGISTRY; |
1214 |
|
1215 |
our $VERBOSE; |
1216 |
|
1217 |
BEGIN { |
1218 |
require "AnyEvent/constants.pl"; |
1219 |
|
1220 |
eval "sub TAINT (){" . (${^TAINT}*1) . "}"; |
1221 |
|
1222 |
delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV} |
1223 |
if ${^TAINT}; |
1224 |
|
1225 |
$VERBOSE = $ENV{PERL_ANYEVENT_VERBOSE}*1; |
1226 |
|
1227 |
} |
1228 |
|
1229 |
our $MAX_SIGNAL_LATENCY = 10; |
1230 |
|
1231 |
our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred |
1232 |
|
1233 |
{ |
1234 |
my $idx; |
1235 |
$PROTOCOL{$_} = ++$idx |
1236 |
for reverse split /\s*,\s*/, |
1237 |
$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6"; |
1238 |
} |
1239 |
|
1240 |
our @post_detect; |
1241 |
|
1242 |
sub post_detect(&) { |
1243 |
my ($cb) = @_; |
1244 |
|
1245 |
push @post_detect, $cb; |
1246 |
|
1247 |
defined wantarray |
1248 |
? bless \$cb, "AnyEvent::Util::postdetect" |
1249 |
: () |
1250 |
} |
1251 |
|
1252 |
sub AnyEvent::Util::postdetect::DESTROY { |
1253 |
@post_detect = grep $_ != ${$_[0]}, @post_detect; |
1254 |
} |
1255 |
|
1256 |
our $POSTPONE_W; |
1257 |
our @POSTPONE; |
1258 |
|
1259 |
sub _postpone_exec { |
1260 |
undef $POSTPONE_W; |
1261 |
|
1262 |
&{ shift @POSTPONE } |
1263 |
while @POSTPONE; |
1264 |
} |
1265 |
|
1266 |
sub postpone(&) { |
1267 |
push @POSTPONE, shift; |
1268 |
|
1269 |
$POSTPONE_W ||= AE::timer (0, 0, \&_postpone_exec); |
1270 |
|
1271 |
() |
1272 |
} |
1273 |
|
1274 |
our @models = ( |
1275 |
[EV:: => AnyEvent::Impl::EV:: , 1], |
1276 |
[AnyEvent::Loop:: => AnyEvent::Impl::Perl:: , 1], |
1277 |
# everything below here will not (normally) be autoprobed |
1278 |
# as the pure perl backend should work everywhere |
1279 |
# and is usually faster |
1280 |
[Event:: => AnyEvent::Impl::Event::, 1], |
1281 |
[Glib:: => AnyEvent::Impl::Glib:: , 1], # becomes extremely slow with many watchers |
1282 |
[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy |
1283 |
[Irssi:: => AnyEvent::Impl::Irssi::], # Irssi has a bogus "Event" package |
1284 |
[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles |
1285 |
[Qt:: => AnyEvent::Impl::Qt::], # requires special main program |
1286 |
[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza |
1287 |
[Wx:: => AnyEvent::Impl::POE::], |
1288 |
[Prima:: => AnyEvent::Impl::POE::], |
1289 |
[IO::Async::Loop:: => AnyEvent::Impl::IOAsync::], # a bitch to autodetect |
1290 |
[Cocoa::EventLoop:: => AnyEvent::Impl::Cocoa::], |
1291 |
[FLTK:: => AnyEvent::Impl::FLTK::], |
1292 |
); |
1293 |
|
1294 |
our %method = map +($_ => 1), |
1295 |
qw(io timer time now now_update signal child idle condvar DESTROY); |
1296 |
|
1297 |
sub detect() { |
1298 |
# free some memory |
1299 |
*detect = sub () { $MODEL }; |
1300 |
|
1301 |
local $!; # for good measure |
1302 |
local $SIG{__DIE__}; |
1303 |
|
1304 |
if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z0-9:]+)$/) { |
1305 |
my $model = $1; |
1306 |
$model = "AnyEvent::Impl::$model" unless $model =~ s/::$//; |
1307 |
if (eval "require $model") { |
1308 |
$MODEL = $model; |
1309 |
warn "AnyEvent: loaded model '$model' (forced by \$ENV{PERL_ANYEVENT_MODEL}), using it.\n" if $VERBOSE >= 2; |
1310 |
} else { |
1311 |
warn "AnyEvent: unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@" if $VERBOSE; |
1312 |
} |
1313 |
} |
1314 |
|
1315 |
# check for already loaded models |
1316 |
unless ($MODEL) { |
1317 |
for (@REGISTRY, @models) { |
1318 |
my ($package, $model) = @$_; |
1319 |
if (${"$package\::VERSION"} > 0) { |
1320 |
if (eval "require $model") { |
1321 |
$MODEL = $model; |
1322 |
warn "AnyEvent: autodetected model '$model', using it.\n" if $VERBOSE >= 2; |
1323 |
last; |
1324 |
} |
1325 |
} |
1326 |
} |
1327 |
|
1328 |
unless ($MODEL) { |
1329 |
# try to autoload a model |
1330 |
for (@REGISTRY, @models) { |
1331 |
my ($package, $model, $autoload) = @$_; |
1332 |
if ( |
1333 |
$autoload |
1334 |
and eval "require $package" |
1335 |
and ${"$package\::VERSION"} > 0 |
1336 |
and eval "require $model" |
1337 |
) { |
1338 |
$MODEL = $model; |
1339 |
warn "AnyEvent: autoloaded model '$model', using it.\n" if $VERBOSE >= 2; |
1340 |
last; |
1341 |
} |
1342 |
} |
1343 |
|
1344 |
$MODEL |
1345 |
or die "AnyEvent: backend autodetection failed - did you properly install AnyEvent?\n"; |
1346 |
} |
1347 |
} |
1348 |
|
1349 |
# free memory only needed for probing |
1350 |
undef @models; |
1351 |
undef @REGISTRY; |
1352 |
|
1353 |
push @{"$MODEL\::ISA"}, "AnyEvent::Base"; |
1354 |
unshift @ISA, $MODEL; |
1355 |
|
1356 |
# now nuke some methods that are overridden by the backend. |
1357 |
# SUPER usage is not allowed in these. |
1358 |
for (qw(time signal child idle)) { |
1359 |
undef &{"AnyEvent::Base::$_"} |
1360 |
if defined &{"$MODEL\::$_"}; |
1361 |
} |
1362 |
|
1363 |
if ($ENV{PERL_ANYEVENT_STRICT}) { |
1364 |
eval { require AnyEvent::Strict }; |
1365 |
warn "AnyEvent: cannot load AnyEvent::Strict: $@" |
1366 |
if $@ && $VERBOSE; |
1367 |
} |
1368 |
|
1369 |
(shift @post_detect)->() while @post_detect; |
1370 |
undef @post_detect; |
1371 |
|
1372 |
*post_detect = sub(&) { |
1373 |
shift->(); |
1374 |
|
1375 |
undef |
1376 |
}; |
1377 |
|
1378 |
# recover a few more bytes |
1379 |
postpone { |
1380 |
undef &AUTOLOAD; |
1381 |
}; |
1382 |
|
1383 |
$MODEL |
1384 |
} |
1385 |
|
1386 |
our %method = map +($_ => 1), |
1387 |
qw(io timer time now now_update signal child idle condvar DESTROY); |
1388 |
|
1389 |
sub AUTOLOAD { |
1390 |
(my $func = $AUTOLOAD) =~ s/.*://; |
1391 |
|
1392 |
$method{$func} |
1393 |
or Carp::croak "$func: not a valid AnyEvent class method"; |
1394 |
|
1395 |
# free some memory |
1396 |
undef %method; |
1397 |
|
1398 |
detect; |
1399 |
|
1400 |
my $class = shift; |
1401 |
$class->$func (@_); |
1402 |
} |
1403 |
|
1404 |
# utility function to dup a filehandle. this is used by many backends |
1405 |
# to support binding more than one watcher per filehandle (they usually |
1406 |
# allow only one watcher per fd, so we dup it to get a different one). |
1407 |
sub _dupfh($$;$$) { |
1408 |
my ($poll, $fh, $r, $w) = @_; |
1409 |
|
1410 |
# cygwin requires the fh mode to be matching, unix doesn't |
1411 |
my ($rw, $mode) = $poll eq "r" ? ($r, "<&") : ($w, ">&"); |
1412 |
|
1413 |
open my $fh2, $mode, $fh |
1414 |
or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,"; |
1415 |
|
1416 |
# we assume CLOEXEC is already set by perl in all important cases |
1417 |
|
1418 |
($fh2, $rw) |
1419 |
} |
1420 |
|
1421 |
=head1 SIMPLIFIED AE API |
1422 |
|
1423 |
Starting with version 5.0, AnyEvent officially supports a second, much |
1424 |
simpler, API that is designed to reduce the calling, typing and memory |
1425 |
overhead by using function call syntax and a fixed number of parameters. |
1426 |
|
1427 |
See the L<AE> manpage for details. |
1428 |
|
1429 |
=cut |
1430 |
|
1431 |
package AE; |
1432 |
|
1433 |
our $VERSION = $AnyEvent::VERSION; |
1434 |
|
1435 |
|
1436 |
sub _reset() { |
1437 |
eval q{ |
1438 |
# fall back to the main API by default - backends and AnyEvent::Base |
1439 |
# implementations can overwrite these. |
1440 |
|
1441 |
sub io($$$) { |
1442 |
AnyEvent->io (fh => $_[0], poll => $_[1] ? "w" : "r", cb => $_[2]) |
1443 |
} |
1444 |
|
1445 |
sub timer($$$) { |
1446 |
AnyEvent->timer (after => $_[0], interval => $_[1], cb => $_[2]) |
1447 |
} |
1448 |
|
1449 |
sub signal($$) { |
1450 |
AnyEvent->signal (signal => $_[0], cb => $_[1]) |
1451 |
} |
1452 |
|
1453 |
sub child($$) { |
1454 |
AnyEvent->child (pid => $_[0], cb => $_[1]) |
1455 |
} |
1456 |
|
1457 |
sub idle($) { |
1458 |
AnyEvent->idle (cb => $_[0]) |
1459 |
} |
1460 |
|
1461 |
sub cv(;&) { |
1462 |
AnyEvent->condvar (@_ ? (cb => $_[0]) : ()) |
1463 |
} |
1464 |
|
1465 |
sub now() { |
1466 |
AnyEvent->now |
1467 |
} |
1468 |
|
1469 |
sub now_update() { |
1470 |
AnyEvent->now_update |
1471 |
} |
1472 |
|
1473 |
sub time() { |
1474 |
AnyEvent->time |
1475 |
} |
1476 |
|
1477 |
*postpone = \&AnyEvent::postpone; |
1478 |
}; |
1479 |
die if $@; |
1480 |
} |
1481 |
|
1482 |
BEGIN { _reset } |
1483 |
|
1484 |
package AnyEvent::Base; |
1485 |
|
1486 |
# default implementations for many methods |
1487 |
|
1488 |
sub time { |
1489 |
eval q{ # poor man's autoloading {} |
1490 |
# probe for availability of Time::HiRes |
1491 |
if (eval "use Time::HiRes (); Time::HiRes::time (); 1") { |
1492 |
warn "AnyEvent: using Time::HiRes for sub-second timing accuracy.\n" if $VERBOSE >= 8; |
1493 |
*AE::time = \&Time::HiRes::time; |
1494 |
# if (eval "use POSIX (); (POSIX::times())... |
1495 |
} else { |
1496 |
warn "AnyEvent: using built-in time(), WARNING, no sub-second resolution!\n" if $VERBOSE; |
1497 |
*AE::time = sub (){ time }; # epic fail |
1498 |
} |
1499 |
|
1500 |
*time = sub { AE::time }; # different prototypes |
1501 |
}; |
1502 |
die if $@; |
1503 |
|
1504 |
&time |
1505 |
} |
1506 |
|
1507 |
*now = \&time; |
1508 |
|
1509 |
sub now_update { } |
1510 |
|
1511 |
sub _poll { |
1512 |
Carp::croak "$AnyEvent::MODEL does not support blocking waits. Caught"; |
1513 |
} |
1514 |
|
1515 |
# default implementation for ->condvar |
1516 |
# in fact, the default should not be overwritten |
1517 |
|
1518 |
sub condvar { |
1519 |
eval q{ # poor man's autoloading {} |
1520 |
*condvar = sub { |
1521 |
bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar" |
1522 |
}; |
1523 |
|
1524 |
*AE::cv = sub (;&) { |
1525 |
bless { @_ ? (_ae_cb => shift) : () }, "AnyEvent::CondVar" |
1526 |
}; |
1527 |
}; |
1528 |
die if $@; |
1529 |
|
1530 |
&condvar |
1531 |
} |
1532 |
|
1533 |
# default implementation for ->signal |
1534 |
|
1535 |
our $HAVE_ASYNC_INTERRUPT; |
1536 |
|
1537 |
sub _have_async_interrupt() { |
1538 |
$HAVE_ASYNC_INTERRUPT = 1*(!$ENV{PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT} |
1539 |
&& eval "use Async::Interrupt 1.02 (); 1") |
1540 |
unless defined $HAVE_ASYNC_INTERRUPT; |
1541 |
|
1542 |
$HAVE_ASYNC_INTERRUPT |
1543 |
} |
1544 |
|
1545 |
our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO); |
1546 |
our (%SIG_ASY, %SIG_ASY_W); |
1547 |
our ($SIG_COUNT, $SIG_TW); |
1548 |
|
1549 |
# install a dummy wakeup watcher to reduce signal catching latency |
1550 |
# used by Impls |
1551 |
sub _sig_add() { |
1552 |
unless ($SIG_COUNT++) { |
1553 |
# try to align timer on a full-second boundary, if possible |
1554 |
my $NOW = AE::now; |
1555 |
|
1556 |
$SIG_TW = AE::timer |
1557 |
$MAX_SIGNAL_LATENCY - ($NOW - int $NOW), |
1558 |
$MAX_SIGNAL_LATENCY, |
1559 |
sub { } # just for the PERL_ASYNC_CHECK |
1560 |
; |
1561 |
} |
1562 |
} |
1563 |
|
1564 |
sub _sig_del { |
1565 |
undef $SIG_TW |
1566 |
unless --$SIG_COUNT; |
1567 |
} |
1568 |
|
1569 |
our $_sig_name_init; $_sig_name_init = sub { |
1570 |
eval q{ # poor man's autoloading {} |
1571 |
undef $_sig_name_init; |
1572 |
|
1573 |
if (_have_async_interrupt) { |
1574 |
*sig2num = \&Async::Interrupt::sig2num; |
1575 |
*sig2name = \&Async::Interrupt::sig2name; |
1576 |
} else { |
1577 |
require Config; |
1578 |
|
1579 |
my %signame2num; |
1580 |
@signame2num{ split ' ', $Config::Config{sig_name} } |
1581 |
= split ' ', $Config::Config{sig_num}; |
1582 |
|
1583 |
my @signum2name; |
1584 |
@signum2name[values %signame2num] = keys %signame2num; |
1585 |
|
1586 |
*sig2num = sub($) { |
1587 |
$_[0] > 0 ? shift : $signame2num{+shift} |
1588 |
}; |
1589 |
*sig2name = sub ($) { |
1590 |
$_[0] > 0 ? $signum2name[+shift] : shift |
1591 |
}; |
1592 |
} |
1593 |
}; |
1594 |
die if $@; |
1595 |
}; |
1596 |
|
1597 |
sub sig2num ($) { &$_sig_name_init; &sig2num } |
1598 |
sub sig2name($) { &$_sig_name_init; &sig2name } |
1599 |
|
1600 |
sub signal { |
1601 |
eval q{ # poor man's autoloading {} |
1602 |
# probe for availability of Async::Interrupt |
1603 |
if (_have_async_interrupt) { |
1604 |
warn "AnyEvent: using Async::Interrupt for race-free signal handling.\n" if $VERBOSE >= 8; |
1605 |
|
1606 |
$SIGPIPE_R = new Async::Interrupt::EventPipe; |
1607 |
$SIG_IO = AE::io $SIGPIPE_R->fileno, 0, \&_signal_exec; |
1608 |
|
1609 |
} else { |
1610 |
warn "AnyEvent: using emulated perl signal handling with latency timer.\n" if $VERBOSE >= 8; |
1611 |
|
1612 |
if (AnyEvent::WIN32) { |
1613 |
require AnyEvent::Util; |
1614 |
|
1615 |
($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe (); |
1616 |
AnyEvent::Util::fh_nonblocking ($SIGPIPE_R, 1) if $SIGPIPE_R; |
1617 |
AnyEvent::Util::fh_nonblocking ($SIGPIPE_W, 1) if $SIGPIPE_W; # just in case |
1618 |
} else { |
1619 |
pipe $SIGPIPE_R, $SIGPIPE_W; |
1620 |
fcntl $SIGPIPE_R, AnyEvent::F_SETFL, AnyEvent::O_NONBLOCK if $SIGPIPE_R; |
1621 |
fcntl $SIGPIPE_W, AnyEvent::F_SETFL, AnyEvent::O_NONBLOCK if $SIGPIPE_W; # just in case |
1622 |
|
1623 |
# not strictly required, as $^F is normally 2, but let's make sure... |
1624 |
fcntl $SIGPIPE_R, AnyEvent::F_SETFD, AnyEvent::FD_CLOEXEC; |
1625 |
fcntl $SIGPIPE_W, AnyEvent::F_SETFD, AnyEvent::FD_CLOEXEC; |
1626 |
} |
1627 |
|
1628 |
$SIGPIPE_R |
1629 |
or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n"; |
1630 |
|
1631 |
$SIG_IO = AE::io $SIGPIPE_R, 0, \&_signal_exec; |
1632 |
} |
1633 |
|
1634 |
*signal = $HAVE_ASYNC_INTERRUPT |
1635 |
? sub { |
1636 |
my (undef, %arg) = @_; |
1637 |
|
1638 |
# async::interrupt |
1639 |
my $signal = sig2num $arg{signal}; |
1640 |
$SIG_CB{$signal}{$arg{cb}} = $arg{cb}; |
1641 |
|
1642 |
$SIG_ASY{$signal} ||= new Async::Interrupt |
1643 |
cb => sub { undef $SIG_EV{$signal} }, |
1644 |
signal => $signal, |
1645 |
pipe => [$SIGPIPE_R->filenos], |
1646 |
pipe_autodrain => 0, |
1647 |
; |
1648 |
|
1649 |
bless [$signal, $arg{cb}], "AnyEvent::Base::signal" |
1650 |
} |
1651 |
: sub { |
1652 |
my (undef, %arg) = @_; |
1653 |
|
1654 |
# pure perl |
1655 |
my $signal = sig2name $arg{signal}; |
1656 |
$SIG_CB{$signal}{$arg{cb}} = $arg{cb}; |
1657 |
|
1658 |
$SIG{$signal} ||= sub { |
1659 |
local $!; |
1660 |
syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV; |
1661 |
undef $SIG_EV{$signal}; |
1662 |
}; |
1663 |
|
1664 |
# can't do signal processing without introducing races in pure perl, |
1665 |
# so limit the signal latency. |
1666 |
_sig_add; |
1667 |
|
1668 |
bless [$signal, $arg{cb}], "AnyEvent::Base::signal" |
1669 |
} |
1670 |
; |
1671 |
|
1672 |
*AnyEvent::Base::signal::DESTROY = sub { |
1673 |
my ($signal, $cb) = @{$_[0]}; |
1674 |
|
1675 |
_sig_del; |
1676 |
|
1677 |
delete $SIG_CB{$signal}{$cb}; |
1678 |
|
1679 |
$HAVE_ASYNC_INTERRUPT |
1680 |
? delete $SIG_ASY{$signal} |
1681 |
: # delete doesn't work with older perls - they then |
1682 |
# print weird messages, or just unconditionally exit |
1683 |
# instead of getting the default action. |
1684 |
undef $SIG{$signal} |
1685 |
unless keys %{ $SIG_CB{$signal} }; |
1686 |
}; |
1687 |
|
1688 |
*_signal_exec = sub { |
1689 |
$HAVE_ASYNC_INTERRUPT |
1690 |
? $SIGPIPE_R->drain |
1691 |
: sysread $SIGPIPE_R, (my $dummy), 9; |
1692 |
|
1693 |
while (%SIG_EV) { |
1694 |
for (keys %SIG_EV) { |
1695 |
delete $SIG_EV{$_}; |
1696 |
&$_ for values %{ $SIG_CB{$_} || {} }; |
1697 |
} |
1698 |
} |
1699 |
}; |
1700 |
}; |
1701 |
die if $@; |
1702 |
|
1703 |
&signal |
1704 |
} |
1705 |
|
1706 |
# default implementation for ->child |
1707 |
|
1708 |
our %PID_CB; |
1709 |
our $CHLD_W; |
1710 |
our $CHLD_DELAY_W; |
1711 |
|
1712 |
# used by many Impl's |
1713 |
sub _emit_childstatus($$) { |
1714 |
my (undef, $rpid, $rstatus) = @_; |
1715 |
|
1716 |
$_->($rpid, $rstatus) |
1717 |
for values %{ $PID_CB{$rpid} || {} }, |
1718 |
values %{ $PID_CB{0} || {} }; |
1719 |
} |
1720 |
|
1721 |
sub child { |
1722 |
eval q{ # poor man's autoloading {} |
1723 |
*_sigchld = sub { |
1724 |
my $pid; |
1725 |
|
1726 |
AnyEvent->_emit_childstatus ($pid, $?) |
1727 |
while ($pid = waitpid -1, WNOHANG) > 0; |
1728 |
}; |
1729 |
|
1730 |
*child = sub { |
1731 |
my (undef, %arg) = @_; |
1732 |
|
1733 |
my $pid = $arg{pid}; |
1734 |
my $cb = $arg{cb}; |
1735 |
|
1736 |
$PID_CB{$pid}{$cb+0} = $cb; |
1737 |
|
1738 |
unless ($CHLD_W) { |
1739 |
$CHLD_W = AE::signal CHLD => \&_sigchld; |
1740 |
# child could be a zombie already, so make at least one round |
1741 |
&_sigchld; |
1742 |
} |
1743 |
|
1744 |
bless [$pid, $cb+0], "AnyEvent::Base::child" |
1745 |
}; |
1746 |
|
1747 |
*AnyEvent::Base::child::DESTROY = sub { |
1748 |
my ($pid, $icb) = @{$_[0]}; |
1749 |
|
1750 |
delete $PID_CB{$pid}{$icb}; |
1751 |
delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} }; |
1752 |
|
1753 |
undef $CHLD_W unless keys %PID_CB; |
1754 |
}; |
1755 |
}; |
1756 |
die if $@; |
1757 |
|
1758 |
&child |
1759 |
} |
1760 |
|
1761 |
# idle emulation is done by simply using a timer, regardless |
1762 |
# of whether the process is idle or not, and not letting |
1763 |
# the callback use more than 50% of the time. |
1764 |
sub idle { |
1765 |
eval q{ # poor man's autoloading {} |
1766 |
*idle = sub { |
1767 |
my (undef, %arg) = @_; |
1768 |
|
1769 |
my ($cb, $w, $rcb) = $arg{cb}; |
1770 |
|
1771 |
$rcb = sub { |
1772 |
if ($cb) { |
1773 |
$w = _time; |
1774 |
&$cb; |
1775 |
$w = _time - $w; |
1776 |
|
1777 |
# never use more then 50% of the time for the idle watcher, |
1778 |
# within some limits |
1779 |
$w = 0.0001 if $w < 0.0001; |
1780 |
$w = 5 if $w > 5; |
1781 |
|
1782 |
$w = AE::timer $w, 0, $rcb; |
1783 |
} else { |
1784 |
# clean up... |
1785 |
undef $w; |
1786 |
undef $rcb; |
1787 |
} |
1788 |
}; |
1789 |
|
1790 |
$w = AE::timer 0.05, 0, $rcb; |
1791 |
|
1792 |
bless \\$cb, "AnyEvent::Base::idle" |
1793 |
}; |
1794 |
|
1795 |
*AnyEvent::Base::idle::DESTROY = sub { |
1796 |
undef $${$_[0]}; |
1797 |
}; |
1798 |
}; |
1799 |
die if $@; |
1800 |
|
1801 |
&idle |
1802 |
} |
1803 |
|
1804 |
package AnyEvent::CondVar; |
1805 |
|
1806 |
our @ISA = AnyEvent::CondVar::Base::; |
1807 |
|
1808 |
# only to be used for subclassing |
1809 |
sub new { |
1810 |
my $class = shift; |
1811 |
bless AnyEvent->condvar (@_), $class |
1812 |
} |
1813 |
|
1814 |
package AnyEvent::CondVar::Base; |
1815 |
|
1816 |
#use overload |
1817 |
# '&{}' => sub { my $self = shift; sub { $self->send (@_) } }, |
1818 |
# fallback => 1; |
1819 |
|
1820 |
# save 300+ kilobytes by dirtily hardcoding overloading |
1821 |
${"AnyEvent::CondVar::Base::OVERLOAD"}{dummy}++; # Register with magic by touching. |
1822 |
*{'AnyEvent::CondVar::Base::()'} = sub { }; # "Make it findable via fetchmethod." |
1823 |
*{'AnyEvent::CondVar::Base::(&{}'} = sub { my $self = shift; sub { $self->send (@_) } }; # &{} |
1824 |
${'AnyEvent::CondVar::Base::()'} = 1; # fallback |
1825 |
|
1826 |
our $WAITING; |
1827 |
|
1828 |
sub _send { |
1829 |
# nop |
1830 |
} |
1831 |
|
1832 |
sub _wait { |
1833 |
AnyEvent->_poll until $_[0]{_ae_sent}; |
1834 |
} |
1835 |
|
1836 |
sub send { |
1837 |
my $cv = shift; |
1838 |
$cv->{_ae_sent} = [@_]; |
1839 |
(delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb}; |
1840 |
$cv->_send; |
1841 |
} |
1842 |
|
1843 |
sub croak { |
1844 |
$_[0]{_ae_croak} = $_[1]; |
1845 |
$_[0]->send; |
1846 |
} |
1847 |
|
1848 |
sub ready { |
1849 |
$_[0]{_ae_sent} |
1850 |
} |
1851 |
|
1852 |
sub recv { |
1853 |
unless ($_[0]{_ae_sent}) { |
1854 |
$WAITING |
1855 |
and Carp::croak "AnyEvent::CondVar: recursive blocking wait attempted"; |
1856 |
|
1857 |
local $WAITING = 1; |
1858 |
$_[0]->_wait; |
1859 |
} |
1860 |
|
1861 |
$_[0]{_ae_croak} |
1862 |
and Carp::croak $_[0]{_ae_croak}; |
1863 |
|
1864 |
wantarray |
1865 |
? @{ $_[0]{_ae_sent} } |
1866 |
: $_[0]{_ae_sent}[0] |
1867 |
} |
1868 |
|
1869 |
sub cb { |
1870 |
my $cv = shift; |
1871 |
|
1872 |
@_ |
1873 |
and $cv->{_ae_cb} = shift |
1874 |
and $cv->{_ae_sent} |
1875 |
and (delete $cv->{_ae_cb})->($cv); |
1876 |
|
1877 |
$cv->{_ae_cb} |
1878 |
} |
1879 |
|
1880 |
sub begin { |
1881 |
++$_[0]{_ae_counter}; |
1882 |
$_[0]{_ae_end_cb} = $_[1] if @_ > 1; |
1883 |
} |
1884 |
|
1885 |
sub end { |
1886 |
return if --$_[0]{_ae_counter}; |
1887 |
&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } }; |
1888 |
} |
1889 |
|
1890 |
# undocumented/compatibility with pre-3.4 |
1891 |
*broadcast = \&send; |
1892 |
*wait = \&recv; |
1893 |
|
1894 |
=head1 ERROR AND EXCEPTION HANDLING |
1895 |
|
1896 |
In general, AnyEvent does not do any error handling - it relies on the |
1897 |
caller to do that if required. The L<AnyEvent::Strict> module (see also |
1898 |
the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict |
1899 |
checking of all AnyEvent methods, however, which is highly useful during |
1900 |
development. |
1901 |
|
1902 |
As for exception handling (i.e. runtime errors and exceptions thrown while |
1903 |
executing a callback), this is not only highly event-loop specific, but |
1904 |
also not in any way wrapped by this module, as this is the job of the main |
1905 |
program. |
1906 |
|
1907 |
The pure perl event loop simply re-throws the exception (usually |
1908 |
within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<< |
1909 |
$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and |
1910 |
so on. |
1911 |
|
1912 |
=head1 ENVIRONMENT VARIABLES |
1913 |
|
1914 |
The following environment variables are used by this module or its |
1915 |
submodules. |
1916 |
|
1917 |
Note that AnyEvent will remove I<all> environment variables starting with |
1918 |
C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is |
1919 |
enabled. |
1920 |
|
1921 |
=over 4 |
1922 |
|
1923 |
=item C<PERL_ANYEVENT_VERBOSE> |
1924 |
|
1925 |
By default, AnyEvent will be completely silent except in fatal |
1926 |
conditions. You can set this environment variable to make AnyEvent more |
1927 |
talkative. |
1928 |
|
1929 |
When set to C<1> or higher, causes AnyEvent to warn about unexpected |
1930 |
conditions, such as not being able to load the event model specified by |
1931 |
C<PERL_ANYEVENT_MODEL>. |
1932 |
|
1933 |
When set to C<2> or higher, cause AnyEvent to report to STDERR which event |
1934 |
model it chooses. |
1935 |
|
1936 |
When set to C<8> or higher, then AnyEvent will report extra information on |
1937 |
which optional modules it loads and how it implements certain features. |
1938 |
|
1939 |
=item C<PERL_ANYEVENT_STRICT> |
1940 |
|
1941 |
AnyEvent does not do much argument checking by default, as thorough |
1942 |
argument checking is very costly. Setting this variable to a true value |
1943 |
will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly |
1944 |
check the arguments passed to most method calls. If it finds any problems, |
1945 |
it will croak. |
1946 |
|
1947 |
In other words, enables "strict" mode. |
1948 |
|
1949 |
Unlike C<use strict> (or its modern cousin, C<< use L<common::sense> |
1950 |
>>, it is definitely recommended to keep it off in production. Keeping |
1951 |
C<PERL_ANYEVENT_STRICT=1> in your environment while developing programs |
1952 |
can be very useful, however. |
1953 |
|
1954 |
=item C<PERL_ANYEVENT_MODEL> |
1955 |
|
1956 |
This can be used to specify the event model to be used by AnyEvent, before |
1957 |
auto detection and -probing kicks in. |
1958 |
|
1959 |
It normally is a string consisting entirely of ASCII letters (e.g. C<EV> |
1960 |
or C<IOAsync>). The string C<AnyEvent::Impl::> gets prepended and the |
1961 |
resulting module name is loaded and - if the load was successful - used as |
1962 |
event model backend. If it fails to load then AnyEvent will proceed with |
1963 |
auto detection and -probing. |
1964 |
|
1965 |
If the string ends with C<::> instead (e.g. C<AnyEvent::Impl::EV::>) then |
1966 |
nothing gets prepended and the module name is used as-is (hint: C<::> at |
1967 |
the end of a string designates a module name and quotes it appropriately). |
1968 |
|
1969 |
For example, to force the pure perl model (L<AnyEvent::Loop::Perl>) you |
1970 |
could start your program like this: |
1971 |
|
1972 |
PERL_ANYEVENT_MODEL=Perl perl ... |
1973 |
|
1974 |
=item C<PERL_ANYEVENT_PROTOCOLS> |
1975 |
|
1976 |
Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences |
1977 |
for IPv4 or IPv6. The default is unspecified (and might change, or be the result |
1978 |
of auto probing). |
1979 |
|
1980 |
Must be set to a comma-separated list of protocols or address families, |
1981 |
current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be |
1982 |
used, and preference will be given to protocols mentioned earlier in the |
1983 |
list. |
1984 |
|
1985 |
This variable can effectively be used for denial-of-service attacks |
1986 |
against local programs (e.g. when setuid), although the impact is likely |
1987 |
small, as the program has to handle conenction and other failures anyways. |
1988 |
|
1989 |
Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6, |
1990 |
but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4> |
1991 |
- only support IPv4, never try to resolve or contact IPv6 |
1992 |
addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or |
1993 |
IPv6, but prefer IPv6 over IPv4. |
1994 |
|
1995 |
=item C<PERL_ANYEVENT_EDNS0> |
1996 |
|
1997 |
Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension |
1998 |
for DNS. This extension is generally useful to reduce DNS traffic, but |
1999 |
some (broken) firewalls drop such DNS packets, which is why it is off by |
2000 |
default. |
2001 |
|
2002 |
Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce |
2003 |
EDNS0 in its DNS requests. |
2004 |
|
2005 |
=item C<PERL_ANYEVENT_MAX_FORKS> |
2006 |
|
2007 |
The maximum number of child processes that C<AnyEvent::Util::fork_call> |
2008 |
will create in parallel. |
2009 |
|
2010 |
=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS> |
2011 |
|
2012 |
The default value for the C<max_outstanding> parameter for the default DNS |
2013 |
resolver - this is the maximum number of parallel DNS requests that are |
2014 |
sent to the DNS server. |
2015 |
|
2016 |
=item C<PERL_ANYEVENT_RESOLV_CONF> |
2017 |
|
2018 |
The file to use instead of F</etc/resolv.conf> (or OS-specific |
2019 |
configuration) in the default resolver. When set to the empty string, no |
2020 |
default config will be used. |
2021 |
|
2022 |
=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>. |
2023 |
|
2024 |
When neither C<ca_file> nor C<ca_path> was specified during |
2025 |
L<AnyEvent::TLS> context creation, and either of these environment |
2026 |
variables exist, they will be used to specify CA certificate locations |
2027 |
instead of a system-dependent default. |
2028 |
|
2029 |
=item C<PERL_ANYEVENT_AVOID_GUARD> and C<PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT> |
2030 |
|
2031 |
When these are set to C<1>, then the respective modules are not |
2032 |
loaded. Mostly good for testing AnyEvent itself. |
2033 |
|
2034 |
=back |
2035 |
|
2036 |
=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE |
2037 |
|
2038 |
This is an advanced topic that you do not normally need to use AnyEvent in |
2039 |
a module. This section is only of use to event loop authors who want to |
2040 |
provide AnyEvent compatibility. |
2041 |
|
2042 |
If you need to support another event library which isn't directly |
2043 |
supported by AnyEvent, you can supply your own interface to it by |
2044 |
pushing, before the first watcher gets created, the package name of |
2045 |
the event module and the package name of the interface to use onto |
2046 |
C<@AnyEvent::REGISTRY>. You can do that before and even without loading |
2047 |
AnyEvent, so it is reasonably cheap. |
2048 |
|
2049 |
Example: |
2050 |
|
2051 |
push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::]; |
2052 |
|
2053 |
This tells AnyEvent to (literally) use the C<urxvt::anyevent::> |
2054 |
package/class when it finds the C<urxvt> package/module is already loaded. |
2055 |
|
2056 |
When AnyEvent is loaded and asked to find a suitable event model, it |
2057 |
will first check for the presence of urxvt by trying to C<use> the |
2058 |
C<urxvt::anyevent> module. |
2059 |
|
2060 |
The class should provide implementations for all watcher types. See |
2061 |
L<AnyEvent::Impl::EV> (source code), L<AnyEvent::Impl::Glib> (Source code) |
2062 |
and so on for actual examples. Use C<perldoc -m AnyEvent::Impl::Glib> to |
2063 |
see the sources. |
2064 |
|
2065 |
If you don't provide C<signal> and C<child> watchers than AnyEvent will |
2066 |
provide suitable (hopefully) replacements. |
2067 |
|
2068 |
The above example isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt) |
2069 |
terminal emulator uses the above line as-is. An interface isn't included |
2070 |
in AnyEvent because it doesn't make sense outside the embedded interpreter |
2071 |
inside I<rxvt-unicode>, and it is updated and maintained as part of the |
2072 |
I<rxvt-unicode> distribution. |
2073 |
|
2074 |
I<rxvt-unicode> also cheats a bit by not providing blocking access to |
2075 |
condition variables: code blocking while waiting for a condition will |
2076 |
C<die>. This still works with most modules/usages, and blocking calls must |
2077 |
not be done in an interactive application, so it makes sense. |
2078 |
|
2079 |
=head1 EXAMPLE PROGRAM |
2080 |
|
2081 |
The following program uses an I/O watcher to read data from STDIN, a timer |
2082 |
to display a message once per second, and a condition variable to quit the |
2083 |
program when the user enters quit: |
2084 |
|
2085 |
use AnyEvent; |
2086 |
|
2087 |
my $cv = AnyEvent->condvar; |
2088 |
|
2089 |
my $io_watcher = AnyEvent->io ( |
2090 |
fh => \*STDIN, |
2091 |
poll => 'r', |
2092 |
cb => sub { |
2093 |
warn "io event <$_[0]>\n"; # will always output <r> |
2094 |
chomp (my $input = <STDIN>); # read a line |
2095 |
warn "read: $input\n"; # output what has been read |
2096 |
$cv->send if $input =~ /^q/i; # quit program if /^q/i |
2097 |
}, |
2098 |
); |
2099 |
|
2100 |
my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub { |
2101 |
warn "timeout\n"; # print 'timeout' at most every second |
2102 |
}); |
2103 |
|
2104 |
$cv->recv; # wait until user enters /^q/i |
2105 |
|
2106 |
=head1 REAL-WORLD EXAMPLE |
2107 |
|
2108 |
Consider the L<Net::FCP> module. It features (among others) the following |
2109 |
API calls, which are to freenet what HTTP GET requests are to http: |
2110 |
|
2111 |
my $data = $fcp->client_get ($url); # blocks |
2112 |
|
2113 |
my $transaction = $fcp->txn_client_get ($url); # does not block |
2114 |
$transaction->cb ( sub { ... } ); # set optional result callback |
2115 |
my $data = $transaction->result; # possibly blocks |
2116 |
|
2117 |
The C<client_get> method works like C<LWP::Simple::get>: it requests the |
2118 |
given URL and waits till the data has arrived. It is defined to be: |
2119 |
|
2120 |
sub client_get { $_[0]->txn_client_get ($_[1])->result } |
2121 |
|
2122 |
And in fact is automatically generated. This is the blocking API of |
2123 |
L<Net::FCP>, and it works as simple as in any other, similar, module. |
2124 |
|
2125 |
More complicated is C<txn_client_get>: It only creates a transaction |
2126 |
(completion, result, ...) object and initiates the transaction. |
2127 |
|
2128 |
my $txn = bless { }, Net::FCP::Txn::; |
2129 |
|
2130 |
It also creates a condition variable that is used to signal the completion |
2131 |
of the request: |
2132 |
|
2133 |
$txn->{finished} = AnyAvent->condvar; |
2134 |
|
2135 |
It then creates a socket in non-blocking mode. |
2136 |
|
2137 |
socket $txn->{fh}, ...; |
2138 |
fcntl $txn->{fh}, F_SETFL, O_NONBLOCK; |
2139 |
connect $txn->{fh}, ... |
2140 |
and !$!{EWOULDBLOCK} |
2141 |
and !$!{EINPROGRESS} |
2142 |
and Carp::croak "unable to connect: $!\n"; |
2143 |
|
2144 |
Then it creates a write-watcher which gets called whenever an error occurs |
2145 |
or the connection succeeds: |
2146 |
|
2147 |
$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'w', cb => sub { $txn->fh_ready_w }); |
2148 |
|
2149 |
And returns this transaction object. The C<fh_ready_w> callback gets |
2150 |
called as soon as the event loop detects that the socket is ready for |
2151 |
writing. |
2152 |
|
2153 |
The C<fh_ready_w> method makes the socket blocking again, writes the |
2154 |
request data and replaces the watcher by a read watcher (waiting for reply |
2155 |
data). The actual code is more complicated, but that doesn't matter for |
2156 |
this example: |
2157 |
|
2158 |
fcntl $txn->{fh}, F_SETFL, 0; |
2159 |
syswrite $txn->{fh}, $txn->{request} |
2160 |
or die "connection or write error"; |
2161 |
$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r }); |
2162 |
|
2163 |
Again, C<fh_ready_r> waits till all data has arrived, and then stores the |
2164 |
result and signals any possible waiters that the request has finished: |
2165 |
|
2166 |
sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf}; |
2167 |
|
2168 |
if (end-of-file or data complete) { |
2169 |
$txn->{result} = $txn->{buf}; |
2170 |
$txn->{finished}->send; |
2171 |
$txb->{cb}->($txn) of $txn->{cb}; # also call callback |
2172 |
} |
2173 |
|
2174 |
The C<result> method, finally, just waits for the finished signal (if the |
2175 |
request was already finished, it doesn't wait, of course, and returns the |
2176 |
data: |
2177 |
|
2178 |
$txn->{finished}->recv; |
2179 |
return $txn->{result}; |
2180 |
|
2181 |
The actual code goes further and collects all errors (C<die>s, exceptions) |
2182 |
that occurred during request processing. The C<result> method detects |
2183 |
whether an exception as thrown (it is stored inside the $txn object) |
2184 |
and just throws the exception, which means connection errors and other |
2185 |
problems get reported to the code that tries to use the result, not in a |
2186 |
random callback. |
2187 |
|
2188 |
All of this enables the following usage styles: |
2189 |
|
2190 |
1. Blocking: |
2191 |
|
2192 |
my $data = $fcp->client_get ($url); |
2193 |
|
2194 |
2. Blocking, but running in parallel: |
2195 |
|
2196 |
my @datas = map $_->result, |
2197 |
map $fcp->txn_client_get ($_), |
2198 |
@urls; |
2199 |
|
2200 |
Both blocking examples work without the module user having to know |
2201 |
anything about events. |
2202 |
|
2203 |
3a. Event-based in a main program, using any supported event module: |
2204 |
|
2205 |
use EV; |
2206 |
|
2207 |
$fcp->txn_client_get ($url)->cb (sub { |
2208 |
my $txn = shift; |
2209 |
my $data = $txn->result; |
2210 |
... |
2211 |
}); |
2212 |
|
2213 |
EV::loop; |
2214 |
|
2215 |
3b. The module user could use AnyEvent, too: |
2216 |
|
2217 |
use AnyEvent; |
2218 |
|
2219 |
my $quit = AnyEvent->condvar; |
2220 |
|
2221 |
$fcp->txn_client_get ($url)->cb (sub { |
2222 |
... |
2223 |
$quit->send; |
2224 |
}); |
2225 |
|
2226 |
$quit->recv; |
2227 |
|
2228 |
|
2229 |
=head1 BENCHMARKS |
2230 |
|
2231 |
To give you an idea of the performance and overheads that AnyEvent adds |
2232 |
over the event loops themselves and to give you an impression of the speed |
2233 |
of various event loops I prepared some benchmarks. |
2234 |
|
2235 |
=head2 BENCHMARKING ANYEVENT OVERHEAD |
2236 |
|
2237 |
Here is a benchmark of various supported event models used natively and |
2238 |
through AnyEvent. The benchmark creates a lot of timers (with a zero |
2239 |
timeout) and I/O watchers (watching STDOUT, a pty, to become writable, |
2240 |
which it is), lets them fire exactly once and destroys them again. |
2241 |
|
2242 |
Source code for this benchmark is found as F<eg/bench> in the AnyEvent |
2243 |
distribution. It uses the L<AE> interface, which makes a real difference |
2244 |
for the EV and Perl backends only. |
2245 |
|
2246 |
=head3 Explanation of the columns |
2247 |
|
2248 |
I<watcher> is the number of event watchers created/destroyed. Since |
2249 |
different event models feature vastly different performances, each event |
2250 |
loop was given a number of watchers so that overall runtime is acceptable |
2251 |
and similar between tested event loop (and keep them from crashing): Glib |
2252 |
would probably take thousands of years if asked to process the same number |
2253 |
of watchers as EV in this benchmark. |
2254 |
|
2255 |
I<bytes> is the number of bytes (as measured by the resident set size, |
2256 |
RSS) consumed by each watcher. This method of measuring captures both C |
2257 |
and Perl-based overheads. |
2258 |
|
2259 |
I<create> is the time, in microseconds (millionths of seconds), that it |
2260 |
takes to create a single watcher. The callback is a closure shared between |
2261 |
all watchers, to avoid adding memory overhead. That means closure creation |
2262 |
and memory usage is not included in the figures. |
2263 |
|
2264 |
I<invoke> is the time, in microseconds, used to invoke a simple |
2265 |
callback. The callback simply counts down a Perl variable and after it was |
2266 |
invoked "watcher" times, it would C<< ->send >> a condvar once to |
2267 |
signal the end of this phase. |
2268 |
|
2269 |
I<destroy> is the time, in microseconds, that it takes to destroy a single |
2270 |
watcher. |
2271 |
|
2272 |
=head3 Results |
2273 |
|
2274 |
name watchers bytes create invoke destroy comment |
2275 |
EV/EV 100000 223 0.47 0.43 0.27 EV native interface |
2276 |
EV/Any 100000 223 0.48 0.42 0.26 EV + AnyEvent watchers |
2277 |
Coro::EV/Any 100000 223 0.47 0.42 0.26 coroutines + Coro::Signal |
2278 |
Perl/Any 100000 431 2.70 0.74 0.92 pure perl implementation |
2279 |
Event/Event 16000 516 31.16 31.84 0.82 Event native interface |
2280 |
Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers |
2281 |
IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll |
2282 |
IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll |
2283 |
Glib/Any 16000 1118 89.00 12.57 51.17 quadratic behaviour |
2284 |
Tk/Any 2000 1346 20.96 10.75 8.00 SEGV with >> 2000 watchers |
2285 |
POE/Any 2000 6951 108.97 795.32 14.24 via POE::Loop::Event |
2286 |
POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select |
2287 |
|
2288 |
=head3 Discussion |
2289 |
|
2290 |
The benchmark does I<not> measure scalability of the event loop very |
2291 |
well. For example, a select-based event loop (such as the pure perl one) |
2292 |
can never compete with an event loop that uses epoll when the number of |
2293 |
file descriptors grows high. In this benchmark, all events become ready at |
2294 |
the same time, so select/poll-based implementations get an unnatural speed |
2295 |
boost. |
2296 |
|
2297 |
Also, note that the number of watchers usually has a nonlinear effect on |
2298 |
overall speed, that is, creating twice as many watchers doesn't take twice |
2299 |
the time - usually it takes longer. This puts event loops tested with a |
2300 |
higher number of watchers at a disadvantage. |
2301 |
|
2302 |
To put the range of results into perspective, consider that on the |
2303 |
benchmark machine, handling an event takes roughly 1600 CPU cycles with |
2304 |
EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU |
2305 |
cycles with POE. |
2306 |
|
2307 |
C<EV> is the sole leader regarding speed and memory use, which are both |
2308 |
maximal/minimal, respectively. When using the L<AE> API there is zero |
2309 |
overhead (when going through the AnyEvent API create is about 5-6 times |
2310 |
slower, with other times being equal, so still uses far less memory than |
2311 |
any other event loop and is still faster than Event natively). |
2312 |
|
2313 |
The pure perl implementation is hit in a few sweet spots (both the |
2314 |
constant timeout and the use of a single fd hit optimisations in the perl |
2315 |
interpreter and the backend itself). Nevertheless this shows that it |
2316 |
adds very little overhead in itself. Like any select-based backend its |
2317 |
performance becomes really bad with lots of file descriptors (and few of |
2318 |
them active), of course, but this was not subject of this benchmark. |
2319 |
|
2320 |
The C<Event> module has a relatively high setup and callback invocation |
2321 |
cost, but overall scores in on the third place. |
2322 |
|
2323 |
C<IO::Async> performs admirably well, about on par with C<Event>, even |
2324 |
when using its pure perl backend. |
2325 |
|
2326 |
C<Glib>'s memory usage is quite a bit higher, but it features a |
2327 |
faster callback invocation and overall ends up in the same class as |
2328 |
C<Event>. However, Glib scales extremely badly, doubling the number of |
2329 |
watchers increases the processing time by more than a factor of four, |
2330 |
making it completely unusable when using larger numbers of watchers |
2331 |
(note that only a single file descriptor was used in the benchmark, so |
2332 |
inefficiencies of C<poll> do not account for this). |
2333 |
|
2334 |
The C<Tk> adaptor works relatively well. The fact that it crashes with |
2335 |
more than 2000 watchers is a big setback, however, as correctness takes |
2336 |
precedence over speed. Nevertheless, its performance is surprising, as the |
2337 |
file descriptor is dup()ed for each watcher. This shows that the dup() |
2338 |
employed by some adaptors is not a big performance issue (it does incur a |
2339 |
hidden memory cost inside the kernel which is not reflected in the figures |
2340 |
above). |
2341 |
|
2342 |
C<POE>, regardless of underlying event loop (whether using its pure perl |
2343 |
select-based backend or the Event module, the POE-EV backend couldn't |
2344 |
be tested because it wasn't working) shows abysmal performance and |
2345 |
memory usage with AnyEvent: Watchers use almost 30 times as much memory |
2346 |
as EV watchers, and 10 times as much memory as Event (the high memory |
2347 |
requirements are caused by requiring a session for each watcher). Watcher |
2348 |
invocation speed is almost 900 times slower than with AnyEvent's pure perl |
2349 |
implementation. |
2350 |
|
2351 |
The design of the POE adaptor class in AnyEvent can not really account |
2352 |
for the performance issues, though, as session creation overhead is |
2353 |
small compared to execution of the state machine, which is coded pretty |
2354 |
optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that |
2355 |
using multiple sessions is not a good approach, especially regarding |
2356 |
memory usage, even the author of POE could not come up with a faster |
2357 |
design). |
2358 |
|
2359 |
=head3 Summary |
2360 |
|
2361 |
=over 4 |
2362 |
|
2363 |
=item * Using EV through AnyEvent is faster than any other event loop |
2364 |
(even when used without AnyEvent), but most event loops have acceptable |
2365 |
performance with or without AnyEvent. |
2366 |
|
2367 |
=item * The overhead AnyEvent adds is usually much smaller than the overhead of |
2368 |
the actual event loop, only with extremely fast event loops such as EV |
2369 |
adds AnyEvent significant overhead. |
2370 |
|
2371 |
=item * You should avoid POE like the plague if you want performance or |
2372 |
reasonable memory usage. |
2373 |
|
2374 |
=back |
2375 |
|
2376 |
=head2 BENCHMARKING THE LARGE SERVER CASE |
2377 |
|
2378 |
This benchmark actually benchmarks the event loop itself. It works by |
2379 |
creating a number of "servers": each server consists of a socket pair, a |
2380 |
timeout watcher that gets reset on activity (but never fires), and an I/O |
2381 |
watcher waiting for input on one side of the socket. Each time the socket |
2382 |
watcher reads a byte it will write that byte to a random other "server". |
2383 |
|
2384 |
The effect is that there will be a lot of I/O watchers, only part of which |
2385 |
are active at any one point (so there is a constant number of active |
2386 |
fds for each loop iteration, but which fds these are is random). The |
2387 |
timeout is reset each time something is read because that reflects how |
2388 |
most timeouts work (and puts extra pressure on the event loops). |
2389 |
|
2390 |
In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100 |
2391 |
(1%) are active. This mirrors the activity of large servers with many |
2392 |
connections, most of which are idle at any one point in time. |
2393 |
|
2394 |
Source code for this benchmark is found as F<eg/bench2> in the AnyEvent |
2395 |
distribution. It uses the L<AE> interface, which makes a real difference |
2396 |
for the EV and Perl backends only. |
2397 |
|
2398 |
=head3 Explanation of the columns |
2399 |
|
2400 |
I<sockets> is the number of sockets, and twice the number of "servers" (as |
2401 |
each server has a read and write socket end). |
2402 |
|
2403 |
I<create> is the time it takes to create a socket pair (which is |
2404 |
nontrivial) and two watchers: an I/O watcher and a timeout watcher. |
2405 |
|
2406 |
I<request>, the most important value, is the time it takes to handle a |
2407 |
single "request", that is, reading the token from the pipe and forwarding |
2408 |
it to another server. This includes deleting the old timeout and creating |
2409 |
a new one that moves the timeout into the future. |
2410 |
|
2411 |
=head3 Results |
2412 |
|
2413 |
name sockets create request |
2414 |
EV 20000 62.66 7.99 |
2415 |
Perl 20000 68.32 32.64 |
2416 |
IOAsync 20000 174.06 101.15 epoll |
2417 |
IOAsync 20000 174.67 610.84 poll |
2418 |
Event 20000 202.69 242.91 |
2419 |
Glib 20000 557.01 1689.52 |
2420 |
POE 20000 341.54 12086.32 uses POE::Loop::Event |
2421 |
|
2422 |
=head3 Discussion |
2423 |
|
2424 |
This benchmark I<does> measure scalability and overall performance of the |
2425 |
particular event loop. |
2426 |
|
2427 |
EV is again fastest. Since it is using epoll on my system, the setup time |
2428 |
is relatively high, though. |
2429 |
|
2430 |
Perl surprisingly comes second. It is much faster than the C-based event |
2431 |
loops Event and Glib. |
2432 |
|
2433 |
IO::Async performs very well when using its epoll backend, and still quite |
2434 |
good compared to Glib when using its pure perl backend. |
2435 |
|
2436 |
Event suffers from high setup time as well (look at its code and you will |
2437 |
understand why). Callback invocation also has a high overhead compared to |
2438 |
the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event |
2439 |
uses select or poll in basically all documented configurations. |
2440 |
|
2441 |
Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It |
2442 |
clearly fails to perform with many filehandles or in busy servers. |
2443 |
|
2444 |
POE is still completely out of the picture, taking over 1000 times as long |
2445 |
as EV, and over 100 times as long as the Perl implementation, even though |
2446 |
it uses a C-based event loop in this case. |
2447 |
|
2448 |
=head3 Summary |
2449 |
|
2450 |
=over 4 |
2451 |
|
2452 |
=item * The pure perl implementation performs extremely well. |
2453 |
|
2454 |
=item * Avoid Glib or POE in large projects where performance matters. |
2455 |
|
2456 |
=back |
2457 |
|
2458 |
=head2 BENCHMARKING SMALL SERVERS |
2459 |
|
2460 |
While event loops should scale (and select-based ones do not...) even to |
2461 |
large servers, most programs we (or I :) actually write have only a few |
2462 |
I/O watchers. |
2463 |
|
2464 |
In this benchmark, I use the same benchmark program as in the large server |
2465 |
case, but it uses only eight "servers", of which three are active at any |
2466 |
one time. This should reflect performance for a small server relatively |
2467 |
well. |
2468 |
|
2469 |
The columns are identical to the previous table. |
2470 |
|
2471 |
=head3 Results |
2472 |
|
2473 |
name sockets create request |
2474 |
EV 16 20.00 6.54 |
2475 |
Perl 16 25.75 12.62 |
2476 |
Event 16 81.27 35.86 |
2477 |
Glib 16 32.63 15.48 |
2478 |
POE 16 261.87 276.28 uses POE::Loop::Event |
2479 |
|
2480 |
=head3 Discussion |
2481 |
|
2482 |
The benchmark tries to test the performance of a typical small |
2483 |
server. While knowing how various event loops perform is interesting, keep |
2484 |
in mind that their overhead in this case is usually not as important, due |
2485 |
to the small absolute number of watchers (that is, you need efficiency and |
2486 |
speed most when you have lots of watchers, not when you only have a few of |
2487 |
them). |
2488 |
|
2489 |
EV is again fastest. |
2490 |
|
2491 |
Perl again comes second. It is noticeably faster than the C-based event |
2492 |
loops Event and Glib, although the difference is too small to really |
2493 |
matter. |
2494 |
|
2495 |
POE also performs much better in this case, but is is still far behind the |
2496 |
others. |
2497 |
|
2498 |
=head3 Summary |
2499 |
|
2500 |
=over 4 |
2501 |
|
2502 |
=item * C-based event loops perform very well with small number of |
2503 |
watchers, as the management overhead dominates. |
2504 |
|
2505 |
=back |
2506 |
|
2507 |
=head2 THE IO::Lambda BENCHMARK |
2508 |
|
2509 |
Recently I was told about the benchmark in the IO::Lambda manpage, which |
2510 |
could be misinterpreted to make AnyEvent look bad. In fact, the benchmark |
2511 |
simply compares IO::Lambda with POE, and IO::Lambda looks better (which |
2512 |
shouldn't come as a surprise to anybody). As such, the benchmark is |
2513 |
fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't |
2514 |
very optimal. But how would AnyEvent compare when used without the extra |
2515 |
baggage? To explore this, I wrote the equivalent benchmark for AnyEvent. |
2516 |
|
2517 |
The benchmark itself creates an echo-server, and then, for 500 times, |
2518 |
connects to the echo server, sends a line, waits for the reply, and then |
2519 |
creates the next connection. This is a rather bad benchmark, as it doesn't |
2520 |
test the efficiency of the framework or much non-blocking I/O, but it is a |
2521 |
benchmark nevertheless. |
2522 |
|
2523 |
name runtime |
2524 |
Lambda/select 0.330 sec |
2525 |
+ optimized 0.122 sec |
2526 |
Lambda/AnyEvent 0.327 sec |
2527 |
+ optimized 0.138 sec |
2528 |
Raw sockets/select 0.077 sec |
2529 |
POE/select, components 0.662 sec |
2530 |
POE/select, raw sockets 0.226 sec |
2531 |
POE/select, optimized 0.404 sec |
2532 |
|
2533 |
AnyEvent/select/nb 0.085 sec |
2534 |
AnyEvent/EV/nb 0.068 sec |
2535 |
+state machine 0.134 sec |
2536 |
|
2537 |
The benchmark is also a bit unfair (my fault): the IO::Lambda/POE |
2538 |
benchmarks actually make blocking connects and use 100% blocking I/O, |
2539 |
defeating the purpose of an event-based solution. All of the newly |
2540 |
written AnyEvent benchmarks use 100% non-blocking connects (using |
2541 |
AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS |
2542 |
resolver), so AnyEvent is at a disadvantage here, as non-blocking connects |
2543 |
generally require a lot more bookkeeping and event handling than blocking |
2544 |
connects (which involve a single syscall only). |
2545 |
|
2546 |
The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which |
2547 |
offers similar expressive power as POE and IO::Lambda, using conventional |
2548 |
Perl syntax. This means that both the echo server and the client are 100% |
2549 |
non-blocking, further placing it at a disadvantage. |
2550 |
|
2551 |
As you can see, the AnyEvent + EV combination even beats the |
2552 |
hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl |
2553 |
backend easily beats IO::Lambda and POE. |
2554 |
|
2555 |
And even the 100% non-blocking version written using the high-level (and |
2556 |
slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda |
2557 |
higher level ("unoptimised") abstractions by a large margin, even though |
2558 |
it does all of DNS, tcp-connect and socket I/O in a non-blocking way. |
2559 |
|
2560 |
The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and |
2561 |
F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are |
2562 |
part of the IO::Lambda distribution and were used without any changes. |
2563 |
|
2564 |
|
2565 |
=head1 SIGNALS |
2566 |
|
2567 |
AnyEvent currently installs handlers for these signals: |
2568 |
|
2569 |
=over 4 |
2570 |
|
2571 |
=item SIGCHLD |
2572 |
|
2573 |
A handler for C<SIGCHLD> is installed by AnyEvent's child watcher |
2574 |
emulation for event loops that do not support them natively. Also, some |
2575 |
event loops install a similar handler. |
2576 |
|
2577 |
Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, then |
2578 |
AnyEvent will reset it to default, to avoid losing child exit statuses. |
2579 |
|
2580 |
=item SIGPIPE |
2581 |
|
2582 |
A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef> |
2583 |
when AnyEvent gets loaded. |
2584 |
|
2585 |
The rationale for this is that AnyEvent users usually do not really depend |
2586 |
on SIGPIPE delivery (which is purely an optimisation for shell use, or |
2587 |
badly-written programs), but C<SIGPIPE> can cause spurious and rare |
2588 |
program exits as a lot of people do not expect C<SIGPIPE> when writing to |
2589 |
some random socket. |
2590 |
|
2591 |
The rationale for installing a no-op handler as opposed to ignoring it is |
2592 |
that this way, the handler will be restored to defaults on exec. |
2593 |
|
2594 |
Feel free to install your own handler, or reset it to defaults. |
2595 |
|
2596 |
=back |
2597 |
|
2598 |
=cut |
2599 |
|
2600 |
undef $SIG{CHLD} |
2601 |
if $SIG{CHLD} eq 'IGNORE'; |
2602 |
|
2603 |
$SIG{PIPE} = sub { } |
2604 |
unless defined $SIG{PIPE}; |
2605 |
|
2606 |
=head1 RECOMMENDED/OPTIONAL MODULES |
2607 |
|
2608 |
One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and |
2609 |
its built-in modules) are required to use it. |
2610 |
|
2611 |
That does not mean that AnyEvent won't take advantage of some additional |
2612 |
modules if they are installed. |
2613 |
|
2614 |
This section explains which additional modules will be used, and how they |
2615 |
affect AnyEvent's operation. |
2616 |
|
2617 |
=over 4 |
2618 |
|
2619 |
=item L<Async::Interrupt> |
2620 |
|
2621 |
This slightly arcane module is used to implement fast signal handling: To |
2622 |
my knowledge, there is no way to do completely race-free and quick |
2623 |
signal handling in pure perl. To ensure that signals still get |
2624 |
delivered, AnyEvent will start an interval timer to wake up perl (and |
2625 |
catch the signals) with some delay (default is 10 seconds, look for |
2626 |
C<$AnyEvent::MAX_SIGNAL_LATENCY>). |
2627 |
|
2628 |
If this module is available, then it will be used to implement signal |
2629 |
catching, which means that signals will not be delayed, and the event loop |
2630 |
will not be interrupted regularly, which is more efficient (and good for |
2631 |
battery life on laptops). |
2632 |
|
2633 |
This affects not just the pure-perl event loop, but also other event loops |
2634 |
that have no signal handling on their own (e.g. Glib, Tk, Qt). |
2635 |
|
2636 |
Some event loops (POE, Event, Event::Lib) offer signal watchers natively, |
2637 |
and either employ their own workarounds (POE) or use AnyEvent's workaround |
2638 |
(using C<$AnyEvent::MAX_SIGNAL_LATENCY>). Installing L<Async::Interrupt> |
2639 |
does nothing for those backends. |
2640 |
|
2641 |
=item L<EV> |
2642 |
|
2643 |
This module isn't really "optional", as it is simply one of the backend |
2644 |
event loops that AnyEvent can use. However, it is simply the best event |
2645 |
loop available in terms of features, speed and stability: It supports |
2646 |
the AnyEvent API optimally, implements all the watcher types in XS, does |
2647 |
automatic timer adjustments even when no monotonic clock is available, |
2648 |
can take avdantage of advanced kernel interfaces such as C<epoll> and |
2649 |
C<kqueue>, and is the fastest backend I<by far>. You can even embed |
2650 |
L<Glib>/L<Gtk2> in it (or vice versa, see L<EV::Glib> and L<Glib::EV>). |
2651 |
|
2652 |
If you only use backends that rely on another event loop (e.g. C<Tk>), |
2653 |
then this module will do nothing for you. |
2654 |
|
2655 |
=item L<Guard> |
2656 |
|
2657 |
The guard module, when used, will be used to implement |
2658 |
C<AnyEvent::Util::guard>. This speeds up guards considerably (and uses a |
2659 |
lot less memory), but otherwise doesn't affect guard operation much. It is |
2660 |
purely used for performance. |
2661 |
|
2662 |
=item L<JSON> and L<JSON::XS> |
2663 |
|
2664 |
One of these modules is required when you want to read or write JSON data |
2665 |
via L<AnyEvent::Handle>. L<JSON> is also written in pure-perl, but can take |
2666 |
advantage of the ultra-high-speed L<JSON::XS> module when it is installed. |
2667 |
|
2668 |
=item L<Net::SSLeay> |
2669 |
|
2670 |
Implementing TLS/SSL in Perl is certainly interesting, but not very |
2671 |
worthwhile: If this module is installed, then L<AnyEvent::Handle> (with |
2672 |
the help of L<AnyEvent::TLS>), gains the ability to do TLS/SSL. |
2673 |
|
2674 |
=item L<Time::HiRes> |
2675 |
|
2676 |
This module is part of perl since release 5.008. It will be used when the |
2677 |
chosen event library does not come with a timing source of its own. The |
2678 |
pure-perl event loop (L<AnyEvent::Loop>) will additionally load it to |
2679 |
try to use a monotonic clock for timing stability. |
2680 |
|
2681 |
=back |
2682 |
|
2683 |
|
2684 |
=head1 FORK |
2685 |
|
2686 |
Most event libraries are not fork-safe. The ones who are usually are |
2687 |
because they rely on inefficient but fork-safe C<select> or C<poll> calls |
2688 |
- higher performance APIs such as BSD's kqueue or the dreaded Linux epoll |
2689 |
are usually badly thought-out hacks that are incompatible with fork in |
2690 |
one way or another. Only L<EV> is fully fork-aware and ensures that you |
2691 |
continue event-processing in both parent and child (or both, if you know |
2692 |
what you are doing). |
2693 |
|
2694 |
This means that, in general, you cannot fork and do event processing in |
2695 |
the child if the event library was initialised before the fork (which |
2696 |
usually happens when the first AnyEvent watcher is created, or the library |
2697 |
is loaded). |
2698 |
|
2699 |
If you have to fork, you must either do so I<before> creating your first |
2700 |
watcher OR you must not use AnyEvent at all in the child OR you must do |
2701 |
something completely out of the scope of AnyEvent. |
2702 |
|
2703 |
The problem of doing event processing in the parent I<and> the child |
2704 |
is much more complicated: even for backends that I<are> fork-aware or |
2705 |
fork-safe, their behaviour is not usually what you want: fork clones all |
2706 |
watchers, that means all timers, I/O watchers etc. are active in both |
2707 |
parent and child, which is almost never what you want. USing C<exec> |
2708 |
to start worker children from some kind of manage rprocess is usually |
2709 |
preferred, because it is much easier and cleaner, at the expense of having |
2710 |
to have another binary. |
2711 |
|
2712 |
|
2713 |
=head1 SECURITY CONSIDERATIONS |
2714 |
|
2715 |
AnyEvent can be forced to load any event model via |
2716 |
$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to |
2717 |
execute arbitrary code or directly gain access, it can easily be used to |
2718 |
make the program hang or malfunction in subtle ways, as AnyEvent watchers |
2719 |
will not be active when the program uses a different event model than |
2720 |
specified in the variable. |
2721 |
|
2722 |
You can make AnyEvent completely ignore this variable by deleting it |
2723 |
before the first watcher gets created, e.g. with a C<BEGIN> block: |
2724 |
|
2725 |
BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} } |
2726 |
|
2727 |
use AnyEvent; |
2728 |
|
2729 |
Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can |
2730 |
be used to probe what backend is used and gain other information (which is |
2731 |
probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and |
2732 |
$ENV{PERL_ANYEVENT_STRICT}. |
2733 |
|
2734 |
Note that AnyEvent will remove I<all> environment variables starting with |
2735 |
C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is |
2736 |
enabled. |
2737 |
|
2738 |
|
2739 |
=head1 BUGS |
2740 |
|
2741 |
Perl 5.8 has numerous memleaks that sometimes hit this module and are hard |
2742 |
to work around. If you suffer from memleaks, first upgrade to Perl 5.10 |
2743 |
and check wether the leaks still show up. (Perl 5.10.0 has other annoying |
2744 |
memleaks, such as leaking on C<map> and C<grep> but it is usually not as |
2745 |
pronounced). |
2746 |
|
2747 |
|
2748 |
=head1 SEE ALSO |
2749 |
|
2750 |
Tutorial/Introduction: L<AnyEvent::Intro>. |
2751 |
|
2752 |
FAQ: L<AnyEvent::FAQ>. |
2753 |
|
2754 |
Utility functions: L<AnyEvent::Util>. |
2755 |
|
2756 |
Event modules: L<AnyEvent::Loop>, L<EV>, L<EV::Glib>, L<Glib::EV>, |
2757 |
L<Event>, L<Glib::Event>, L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>. |
2758 |
|
2759 |
Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>, |
2760 |
L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, |
2761 |
L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>, |
2762 |
L<AnyEvent::Impl::POE>, L<AnyEvent::Impl::IOAsync>, L<Anyevent::Impl::Irssi>. |
2763 |
|
2764 |
Non-blocking file handles, sockets, TCP clients and |
2765 |
servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>. |
2766 |
|
2767 |
Asynchronous DNS: L<AnyEvent::DNS>. |
2768 |
|
2769 |
Thread support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>. |
2770 |
|
2771 |
Nontrivial usage examples: L<AnyEvent::GPSD>, L<AnyEvent::IRC>, |
2772 |
L<AnyEvent::HTTP>. |
2773 |
|
2774 |
|
2775 |
=head1 AUTHOR |
2776 |
|
2777 |
Marc Lehmann <schmorp@schmorp.de> |
2778 |
http://home.schmorp.de/ |
2779 |
|
2780 |
=cut |
2781 |
|
2782 |
1 |
2783 |
|