1 |
=head1 NAME |
2 |
|
3 |
AnyEvent - provide framework for multiple event loops |
4 |
|
5 |
EV, Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event loops |
6 |
|
7 |
=head1 SYNOPSIS |
8 |
|
9 |
use AnyEvent; |
10 |
|
11 |
my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub { |
12 |
... |
13 |
}); |
14 |
|
15 |
my $w = AnyEvent->timer (after => $seconds, cb => sub { |
16 |
... |
17 |
}); |
18 |
|
19 |
my $w = AnyEvent->condvar; # stores whether a condition was flagged |
20 |
$w->send; # wake up current and all future recv's |
21 |
$w->recv; # enters "main loop" till $condvar gets ->send |
22 |
|
23 |
=head1 INTRODUCTION/TUTORIAL |
24 |
|
25 |
This manpage is mainly a reference manual. If you are interested |
26 |
in a tutorial or some gentle introduction, have a look at the |
27 |
L<AnyEvent::Intro> manpage. |
28 |
|
29 |
=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT) |
30 |
|
31 |
Glib, POE, IO::Async, Event... CPAN offers event models by the dozen |
32 |
nowadays. So what is different about AnyEvent? |
33 |
|
34 |
Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of |
35 |
policy> and AnyEvent is I<small and efficient>. |
36 |
|
37 |
First and foremost, I<AnyEvent is not an event model> itself, it only |
38 |
interfaces to whatever event model the main program happens to use in a |
39 |
pragmatic way. For event models and certain classes of immortals alike, |
40 |
the statement "there can only be one" is a bitter reality: In general, |
41 |
only one event loop can be active at the same time in a process. AnyEvent |
42 |
helps hiding the differences between those event loops. |
43 |
|
44 |
The goal of AnyEvent is to offer module authors the ability to do event |
45 |
programming (waiting for I/O or timer events) without subscribing to a |
46 |
religion, a way of living, and most importantly: without forcing your |
47 |
module users into the same thing by forcing them to use the same event |
48 |
model you use. |
49 |
|
50 |
For modules like POE or IO::Async (which is a total misnomer as it is |
51 |
actually doing all I/O I<synchronously>...), using them in your module is |
52 |
like joining a cult: After you joined, you are dependent on them and you |
53 |
cannot use anything else, as it is simply incompatible to everything that |
54 |
isn't itself. What's worse, all the potential users of your module are |
55 |
I<also> forced to use the same event loop you use. |
56 |
|
57 |
AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works |
58 |
fine. AnyEvent + Tk works fine etc. etc. but none of these work together |
59 |
with the rest: POE + IO::Async? No go. Tk + Event? No go. Again: if |
60 |
your module uses one of those, every user of your module has to use it, |
61 |
too. But if your module uses AnyEvent, it works transparently with all |
62 |
event models it supports (including stuff like POE and IO::Async, as long |
63 |
as those use one of the supported event loops. It is trivial to add new |
64 |
event loops to AnyEvent, too, so it is future-proof). |
65 |
|
66 |
In addition to being free of having to use I<the one and only true event |
67 |
model>, AnyEvent also is free of bloat and policy: with POE or similar |
68 |
modules, you get an enormous amount of code and strict rules you have to |
69 |
follow. AnyEvent, on the other hand, is lean and up to the point, by only |
70 |
offering the functionality that is necessary, in as thin as a wrapper as |
71 |
technically possible. |
72 |
|
73 |
Of course, AnyEvent comes with a big (and fully optional!) toolbox |
74 |
of useful functionality, such as an asynchronous DNS resolver, 100% |
75 |
non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms |
76 |
such as Windows) and lots of real-world knowledge and workarounds for |
77 |
platform bugs and differences. |
78 |
|
79 |
Now, if you I<do want> lots of policy (this can arguably be somewhat |
80 |
useful) and you want to force your users to use the one and only event |
81 |
model, you should I<not> use this module. |
82 |
|
83 |
=head1 DESCRIPTION |
84 |
|
85 |
L<AnyEvent> provides an identical interface to multiple event loops. This |
86 |
allows module authors to utilise an event loop without forcing module |
87 |
users to use the same event loop (as only a single event loop can coexist |
88 |
peacefully at any one time). |
89 |
|
90 |
The interface itself is vaguely similar, but not identical to the L<Event> |
91 |
module. |
92 |
|
93 |
During the first call of any watcher-creation method, the module tries |
94 |
to detect the currently loaded event loop by probing whether one of the |
95 |
following modules is already loaded: L<EV>, |
96 |
L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>, |
97 |
L<POE>. The first one found is used. If none are found, the module tries |
98 |
to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl |
99 |
adaptor should always succeed) in the order given. The first one that can |
100 |
be successfully loaded will be used. If, after this, still none could be |
101 |
found, AnyEvent will fall back to a pure-perl event loop, which is not |
102 |
very efficient, but should work everywhere. |
103 |
|
104 |
Because AnyEvent first checks for modules that are already loaded, loading |
105 |
an event model explicitly before first using AnyEvent will likely make |
106 |
that model the default. For example: |
107 |
|
108 |
use Tk; |
109 |
use AnyEvent; |
110 |
|
111 |
# .. AnyEvent will likely default to Tk |
112 |
|
113 |
The I<likely> means that, if any module loads another event model and |
114 |
starts using it, all bets are off. Maybe you should tell their authors to |
115 |
use AnyEvent so their modules work together with others seamlessly... |
116 |
|
117 |
The pure-perl implementation of AnyEvent is called |
118 |
C<AnyEvent::Impl::Perl>. Like other event modules you can load it |
119 |
explicitly and enjoy the high availability of that event loop :) |
120 |
|
121 |
=head1 WATCHERS |
122 |
|
123 |
AnyEvent has the central concept of a I<watcher>, which is an object that |
124 |
stores relevant data for each kind of event you are waiting for, such as |
125 |
the callback to call, the file handle to watch, etc. |
126 |
|
127 |
These watchers are normal Perl objects with normal Perl lifetime. After |
128 |
creating a watcher it will immediately "watch" for events and invoke the |
129 |
callback when the event occurs (of course, only when the event model |
130 |
is in control). |
131 |
|
132 |
To disable the watcher you have to destroy it (e.g. by setting the |
133 |
variable you store it in to C<undef> or otherwise deleting all references |
134 |
to it). |
135 |
|
136 |
All watchers are created by calling a method on the C<AnyEvent> class. |
137 |
|
138 |
Many watchers either are used with "recursion" (repeating timers for |
139 |
example), or need to refer to their watcher object in other ways. |
140 |
|
141 |
An any way to achieve that is this pattern: |
142 |
|
143 |
my $w; $w = AnyEvent->type (arg => value ..., cb => sub { |
144 |
# you can use $w here, for example to undef it |
145 |
undef $w; |
146 |
}); |
147 |
|
148 |
Note that C<my $w; $w => combination. This is necessary because in Perl, |
149 |
my variables are only visible after the statement in which they are |
150 |
declared. |
151 |
|
152 |
=head2 I/O WATCHERS |
153 |
|
154 |
You can create an I/O watcher by calling the C<< AnyEvent->io >> method |
155 |
with the following mandatory key-value pairs as arguments: |
156 |
|
157 |
C<fh> the Perl I<file handle> (I<not> file descriptor) to watch |
158 |
for events. C<poll> must be a string that is either C<r> or C<w>, |
159 |
which creates a watcher waiting for "r"eadable or "w"ritable events, |
160 |
respectively. C<cb> is the callback to invoke each time the file handle |
161 |
becomes ready. |
162 |
|
163 |
Although the callback might get passed parameters, their value and |
164 |
presence is undefined and you cannot rely on them. Portable AnyEvent |
165 |
callbacks cannot use arguments passed to I/O watcher callbacks. |
166 |
|
167 |
The I/O watcher might use the underlying file descriptor or a copy of it. |
168 |
You must not close a file handle as long as any watcher is active on the |
169 |
underlying file descriptor. |
170 |
|
171 |
Some event loops issue spurious readyness notifications, so you should |
172 |
always use non-blocking calls when reading/writing from/to your file |
173 |
handles. |
174 |
|
175 |
Example: |
176 |
|
177 |
# wait for readability of STDIN, then read a line and disable the watcher |
178 |
my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub { |
179 |
chomp (my $input = <STDIN>); |
180 |
warn "read: $input\n"; |
181 |
undef $w; |
182 |
}); |
183 |
|
184 |
=head2 TIME WATCHERS |
185 |
|
186 |
You can create a time watcher by calling the C<< AnyEvent->timer >> |
187 |
method with the following mandatory arguments: |
188 |
|
189 |
C<after> specifies after how many seconds (fractional values are |
190 |
supported) the callback should be invoked. C<cb> is the callback to invoke |
191 |
in that case. |
192 |
|
193 |
Although the callback might get passed parameters, their value and |
194 |
presence is undefined and you cannot rely on them. Portable AnyEvent |
195 |
callbacks cannot use arguments passed to time watcher callbacks. |
196 |
|
197 |
The timer callback will be invoked at most once: if you want a repeating |
198 |
timer you have to create a new watcher (this is a limitation by both Tk |
199 |
and Glib). |
200 |
|
201 |
Example: |
202 |
|
203 |
# fire an event after 7.7 seconds |
204 |
my $w = AnyEvent->timer (after => 7.7, cb => sub { |
205 |
warn "timeout\n"; |
206 |
}); |
207 |
|
208 |
# to cancel the timer: |
209 |
undef $w; |
210 |
|
211 |
Example 2: |
212 |
|
213 |
# fire an event after 0.5 seconds, then roughly every second |
214 |
my $w; |
215 |
|
216 |
my $cb = sub { |
217 |
# cancel the old timer while creating a new one |
218 |
$w = AnyEvent->timer (after => 1, cb => $cb); |
219 |
}; |
220 |
|
221 |
# start the "loop" by creating the first watcher |
222 |
$w = AnyEvent->timer (after => 0.5, cb => $cb); |
223 |
|
224 |
=head3 TIMING ISSUES |
225 |
|
226 |
There are two ways to handle timers: based on real time (relative, "fire |
227 |
in 10 seconds") and based on wallclock time (absolute, "fire at 12 |
228 |
o'clock"). |
229 |
|
230 |
While most event loops expect timers to specified in a relative way, they |
231 |
use absolute time internally. This makes a difference when your clock |
232 |
"jumps", for example, when ntp decides to set your clock backwards from |
233 |
the wrong date of 2014-01-01 to 2008-01-01, a watcher that is supposed to |
234 |
fire "after" a second might actually take six years to finally fire. |
235 |
|
236 |
AnyEvent cannot compensate for this. The only event loop that is conscious |
237 |
about these issues is L<EV>, which offers both relative (ev_timer, based |
238 |
on true relative time) and absolute (ev_periodic, based on wallclock time) |
239 |
timers. |
240 |
|
241 |
AnyEvent always prefers relative timers, if available, matching the |
242 |
AnyEvent API. |
243 |
|
244 |
AnyEvent has two additional methods that return the "current time": |
245 |
|
246 |
=over 4 |
247 |
|
248 |
=item AnyEvent->time |
249 |
|
250 |
This returns the "current wallclock time" as a fractional number of |
251 |
seconds since the Epoch (the same thing as C<time> or C<Time::HiRes::time> |
252 |
return, and the result is guaranteed to be compatible with those). |
253 |
|
254 |
It progresses independently of any event loop processing, i.e. each call |
255 |
will check the system clock, which usually gets updated frequently. |
256 |
|
257 |
=item AnyEvent->now |
258 |
|
259 |
This also returns the "current wallclock time", but unlike C<time>, above, |
260 |
this value might change only once per event loop iteration, depending on |
261 |
the event loop (most return the same time as C<time>, above). This is the |
262 |
time that AnyEvent's timers get scheduled against. |
263 |
|
264 |
I<In almost all cases (in all cases if you don't care), this is the |
265 |
function to call when you want to know the current time.> |
266 |
|
267 |
This function is also often faster then C<< AnyEvent->time >>, and |
268 |
thus the preferred method if you want some timestamp (for example, |
269 |
L<AnyEvent::Handle> uses this to update it's activity timeouts). |
270 |
|
271 |
The rest of this section is only of relevance if you try to be very exact |
272 |
with your timing, you can skip it without bad conscience. |
273 |
|
274 |
For a practical example of when these times differ, consider L<Event::Lib> |
275 |
and L<EV> and the following set-up: |
276 |
|
277 |
The event loop is running and has just invoked one of your callback at |
278 |
time=500 (assume no other callbacks delay processing). In your callback, |
279 |
you wait a second by executing C<sleep 1> (blocking the process for a |
280 |
second) and then (at time=501) you create a relative timer that fires |
281 |
after three seconds. |
282 |
|
283 |
With L<Event::Lib>, C<< AnyEvent->time >> and C<< AnyEvent->now >> will |
284 |
both return C<501>, because that is the current time, and the timer will |
285 |
be scheduled to fire at time=504 (C<501> + C<3>). |
286 |
|
287 |
With L<EV>, C<< AnyEvent->time >> returns C<501> (as that is the current |
288 |
time), but C<< AnyEvent->now >> returns C<500>, as that is the time the |
289 |
last event processing phase started. With L<EV>, your timer gets scheduled |
290 |
to run at time=503 (C<500> + C<3>). |
291 |
|
292 |
In one sense, L<Event::Lib> is more exact, as it uses the current time |
293 |
regardless of any delays introduced by event processing. However, most |
294 |
callbacks do not expect large delays in processing, so this causes a |
295 |
higher drift (and a lot more system calls to get the current time). |
296 |
|
297 |
In another sense, L<EV> is more exact, as your timer will be scheduled at |
298 |
the same time, regardless of how long event processing actually took. |
299 |
|
300 |
In either case, if you care (and in most cases, you don't), then you |
301 |
can get whatever behaviour you want with any event loop, by taking the |
302 |
difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into |
303 |
account. |
304 |
|
305 |
=back |
306 |
|
307 |
=head2 SIGNAL WATCHERS |
308 |
|
309 |
You can watch for signals using a signal watcher, C<signal> is the signal |
310 |
I<name> without any C<SIG> prefix, C<cb> is the Perl callback to |
311 |
be invoked whenever a signal occurs. |
312 |
|
313 |
Although the callback might get passed parameters, their value and |
314 |
presence is undefined and you cannot rely on them. Portable AnyEvent |
315 |
callbacks cannot use arguments passed to signal watcher callbacks. |
316 |
|
317 |
Multiple signal occurrences can be clumped together into one callback |
318 |
invocation, and callback invocation will be synchronous. Synchronous means |
319 |
that it might take a while until the signal gets handled by the process, |
320 |
but it is guaranteed not to interrupt any other callbacks. |
321 |
|
322 |
The main advantage of using these watchers is that you can share a signal |
323 |
between multiple watchers. |
324 |
|
325 |
This watcher might use C<%SIG>, so programs overwriting those signals |
326 |
directly will likely not work correctly. |
327 |
|
328 |
Example: exit on SIGINT |
329 |
|
330 |
my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 }); |
331 |
|
332 |
=head2 CHILD PROCESS WATCHERS |
333 |
|
334 |
You can also watch on a child process exit and catch its exit status. |
335 |
|
336 |
The child process is specified by the C<pid> argument (if set to C<0>, it |
337 |
watches for any child process exit). The watcher will trigger as often |
338 |
as status change for the child are received. This works by installing a |
339 |
signal handler for C<SIGCHLD>. The callback will be called with the pid |
340 |
and exit status (as returned by waitpid), so unlike other watcher types, |
341 |
you I<can> rely on child watcher callback arguments. |
342 |
|
343 |
There is a slight catch to child watchers, however: you usually start them |
344 |
I<after> the child process was created, and this means the process could |
345 |
have exited already (and no SIGCHLD will be sent anymore). |
346 |
|
347 |
Not all event models handle this correctly (POE doesn't), but even for |
348 |
event models that I<do> handle this correctly, they usually need to be |
349 |
loaded before the process exits (i.e. before you fork in the first place). |
350 |
|
351 |
This means you cannot create a child watcher as the very first thing in an |
352 |
AnyEvent program, you I<have> to create at least one watcher before you |
353 |
C<fork> the child (alternatively, you can call C<AnyEvent::detect>). |
354 |
|
355 |
Example: fork a process and wait for it |
356 |
|
357 |
my $done = AnyEvent->condvar; |
358 |
|
359 |
my $pid = fork or exit 5; |
360 |
|
361 |
my $w = AnyEvent->child ( |
362 |
pid => $pid, |
363 |
cb => sub { |
364 |
my ($pid, $status) = @_; |
365 |
warn "pid $pid exited with status $status"; |
366 |
$done->send; |
367 |
}, |
368 |
); |
369 |
|
370 |
# do something else, then wait for process exit |
371 |
$done->recv; |
372 |
|
373 |
=head2 CONDITION VARIABLES |
374 |
|
375 |
If you are familiar with some event loops you will know that all of them |
376 |
require you to run some blocking "loop", "run" or similar function that |
377 |
will actively watch for new events and call your callbacks. |
378 |
|
379 |
AnyEvent is different, it expects somebody else to run the event loop and |
380 |
will only block when necessary (usually when told by the user). |
381 |
|
382 |
The instrument to do that is called a "condition variable", so called |
383 |
because they represent a condition that must become true. |
384 |
|
385 |
Condition variables can be created by calling the C<< AnyEvent->condvar |
386 |
>> method, usually without arguments. The only argument pair allowed is |
387 |
C<cb>, which specifies a callback to be called when the condition variable |
388 |
becomes true. |
389 |
|
390 |
After creation, the condition variable is "false" until it becomes "true" |
391 |
by calling the C<send> method (or calling the condition variable as if it |
392 |
were a callback, read about the caveats in the description for the C<< |
393 |
->send >> method). |
394 |
|
395 |
Condition variables are similar to callbacks, except that you can |
396 |
optionally wait for them. They can also be called merge points - points |
397 |
in time where multiple outstanding events have been processed. And yet |
398 |
another way to call them is transactions - each condition variable can be |
399 |
used to represent a transaction, which finishes at some point and delivers |
400 |
a result. |
401 |
|
402 |
Condition variables are very useful to signal that something has finished, |
403 |
for example, if you write a module that does asynchronous http requests, |
404 |
then a condition variable would be the ideal candidate to signal the |
405 |
availability of results. The user can either act when the callback is |
406 |
called or can synchronously C<< ->recv >> for the results. |
407 |
|
408 |
You can also use them to simulate traditional event loops - for example, |
409 |
you can block your main program until an event occurs - for example, you |
410 |
could C<< ->recv >> in your main program until the user clicks the Quit |
411 |
button of your app, which would C<< ->send >> the "quit" event. |
412 |
|
413 |
Note that condition variables recurse into the event loop - if you have |
414 |
two pieces of code that call C<< ->recv >> in a round-robin fashion, you |
415 |
lose. Therefore, condition variables are good to export to your caller, but |
416 |
you should avoid making a blocking wait yourself, at least in callbacks, |
417 |
as this asks for trouble. |
418 |
|
419 |
Condition variables are represented by hash refs in perl, and the keys |
420 |
used by AnyEvent itself are all named C<_ae_XXX> to make subclassing |
421 |
easy (it is often useful to build your own transaction class on top of |
422 |
AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call |
423 |
it's C<new> method in your own C<new> method. |
424 |
|
425 |
There are two "sides" to a condition variable - the "producer side" which |
426 |
eventually calls C<< -> send >>, and the "consumer side", which waits |
427 |
for the send to occur. |
428 |
|
429 |
Example: wait for a timer. |
430 |
|
431 |
# wait till the result is ready |
432 |
my $result_ready = AnyEvent->condvar; |
433 |
|
434 |
# do something such as adding a timer |
435 |
# or socket watcher the calls $result_ready->send |
436 |
# when the "result" is ready. |
437 |
# in this case, we simply use a timer: |
438 |
my $w = AnyEvent->timer ( |
439 |
after => 1, |
440 |
cb => sub { $result_ready->send }, |
441 |
); |
442 |
|
443 |
# this "blocks" (while handling events) till the callback |
444 |
# calls send |
445 |
$result_ready->recv; |
446 |
|
447 |
Example: wait for a timer, but take advantage of the fact that |
448 |
condition variables are also code references. |
449 |
|
450 |
my $done = AnyEvent->condvar; |
451 |
my $delay = AnyEvent->timer (after => 5, cb => $done); |
452 |
$done->recv; |
453 |
|
454 |
=head3 METHODS FOR PRODUCERS |
455 |
|
456 |
These methods should only be used by the producing side, i.e. the |
457 |
code/module that eventually sends the signal. Note that it is also |
458 |
the producer side which creates the condvar in most cases, but it isn't |
459 |
uncommon for the consumer to create it as well. |
460 |
|
461 |
=over 4 |
462 |
|
463 |
=item $cv->send (...) |
464 |
|
465 |
Flag the condition as ready - a running C<< ->recv >> and all further |
466 |
calls to C<recv> will (eventually) return after this method has been |
467 |
called. If nobody is waiting the send will be remembered. |
468 |
|
469 |
If a callback has been set on the condition variable, it is called |
470 |
immediately from within send. |
471 |
|
472 |
Any arguments passed to the C<send> call will be returned by all |
473 |
future C<< ->recv >> calls. |
474 |
|
475 |
Condition variables are overloaded so one can call them directly |
476 |
(as a code reference). Calling them directly is the same as calling |
477 |
C<send>. Note, however, that many C-based event loops do not handle |
478 |
overloading, so as tempting as it may be, passing a condition variable |
479 |
instead of a callback does not work. Both the pure perl and EV loops |
480 |
support overloading, however, as well as all functions that use perl to |
481 |
invoke a callback (as in L<AnyEvent::Socket> and L<AnyEvent::DNS> for |
482 |
example). |
483 |
|
484 |
=item $cv->croak ($error) |
485 |
|
486 |
Similar to send, but causes all call's to C<< ->recv >> to invoke |
487 |
C<Carp::croak> with the given error message/object/scalar. |
488 |
|
489 |
This can be used to signal any errors to the condition variable |
490 |
user/consumer. |
491 |
|
492 |
=item $cv->begin ([group callback]) |
493 |
|
494 |
=item $cv->end |
495 |
|
496 |
These two methods are EXPERIMENTAL and MIGHT CHANGE. |
497 |
|
498 |
These two methods can be used to combine many transactions/events into |
499 |
one. For example, a function that pings many hosts in parallel might want |
500 |
to use a condition variable for the whole process. |
501 |
|
502 |
Every call to C<< ->begin >> will increment a counter, and every call to |
503 |
C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end |
504 |
>>, the (last) callback passed to C<begin> will be executed. That callback |
505 |
is I<supposed> to call C<< ->send >>, but that is not required. If no |
506 |
callback was set, C<send> will be called without any arguments. |
507 |
|
508 |
Let's clarify this with the ping example: |
509 |
|
510 |
my $cv = AnyEvent->condvar; |
511 |
|
512 |
my %result; |
513 |
$cv->begin (sub { $cv->send (\%result) }); |
514 |
|
515 |
for my $host (@list_of_hosts) { |
516 |
$cv->begin; |
517 |
ping_host_then_call_callback $host, sub { |
518 |
$result{$host} = ...; |
519 |
$cv->end; |
520 |
}; |
521 |
} |
522 |
|
523 |
$cv->end; |
524 |
|
525 |
This code fragment supposedly pings a number of hosts and calls |
526 |
C<send> after results for all then have have been gathered - in any |
527 |
order. To achieve this, the code issues a call to C<begin> when it starts |
528 |
each ping request and calls C<end> when it has received some result for |
529 |
it. Since C<begin> and C<end> only maintain a counter, the order in which |
530 |
results arrive is not relevant. |
531 |
|
532 |
There is an additional bracketing call to C<begin> and C<end> outside the |
533 |
loop, which serves two important purposes: first, it sets the callback |
534 |
to be called once the counter reaches C<0>, and second, it ensures that |
535 |
C<send> is called even when C<no> hosts are being pinged (the loop |
536 |
doesn't execute once). |
537 |
|
538 |
This is the general pattern when you "fan out" into multiple subrequests: |
539 |
use an outer C<begin>/C<end> pair to set the callback and ensure C<end> |
540 |
is called at least once, and then, for each subrequest you start, call |
541 |
C<begin> and for each subrequest you finish, call C<end>. |
542 |
|
543 |
=back |
544 |
|
545 |
=head3 METHODS FOR CONSUMERS |
546 |
|
547 |
These methods should only be used by the consuming side, i.e. the |
548 |
code awaits the condition. |
549 |
|
550 |
=over 4 |
551 |
|
552 |
=item $cv->recv |
553 |
|
554 |
Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak |
555 |
>> methods have been called on c<$cv>, while servicing other watchers |
556 |
normally. |
557 |
|
558 |
You can only wait once on a condition - additional calls are valid but |
559 |
will return immediately. |
560 |
|
561 |
If an error condition has been set by calling C<< ->croak >>, then this |
562 |
function will call C<croak>. |
563 |
|
564 |
In list context, all parameters passed to C<send> will be returned, |
565 |
in scalar context only the first one will be returned. |
566 |
|
567 |
Not all event models support a blocking wait - some die in that case |
568 |
(programs might want to do that to stay interactive), so I<if you are |
569 |
using this from a module, never require a blocking wait>, but let the |
570 |
caller decide whether the call will block or not (for example, by coupling |
571 |
condition variables with some kind of request results and supporting |
572 |
callbacks so the caller knows that getting the result will not block, |
573 |
while still supporting blocking waits if the caller so desires). |
574 |
|
575 |
Another reason I<never> to C<< ->recv >> in a module is that you cannot |
576 |
sensibly have two C<< ->recv >>'s in parallel, as that would require |
577 |
multiple interpreters or coroutines/threads, none of which C<AnyEvent> |
578 |
can supply. |
579 |
|
580 |
The L<Coro> module, however, I<can> and I<does> supply coroutines and, in |
581 |
fact, L<Coro::AnyEvent> replaces AnyEvent's condvars by coroutine-safe |
582 |
versions and also integrates coroutines into AnyEvent, making blocking |
583 |
C<< ->recv >> calls perfectly safe as long as they are done from another |
584 |
coroutine (one that doesn't run the event loop). |
585 |
|
586 |
You can ensure that C<< -recv >> never blocks by setting a callback and |
587 |
only calling C<< ->recv >> from within that callback (or at a later |
588 |
time). This will work even when the event loop does not support blocking |
589 |
waits otherwise. |
590 |
|
591 |
=item $bool = $cv->ready |
592 |
|
593 |
Returns true when the condition is "true", i.e. whether C<send> or |
594 |
C<croak> have been called. |
595 |
|
596 |
=item $cb = $cv->cb ([new callback]) |
597 |
|
598 |
This is a mutator function that returns the callback set and optionally |
599 |
replaces it before doing so. |
600 |
|
601 |
The callback will be called when the condition becomes "true", i.e. when |
602 |
C<send> or C<croak> are called, with the only argument being the condition |
603 |
variable itself. Calling C<recv> inside the callback or at any later time |
604 |
is guaranteed not to block. |
605 |
|
606 |
=back |
607 |
|
608 |
=head1 GLOBAL VARIABLES AND FUNCTIONS |
609 |
|
610 |
=over 4 |
611 |
|
612 |
=item $AnyEvent::MODEL |
613 |
|
614 |
Contains C<undef> until the first watcher is being created. Then it |
615 |
contains the event model that is being used, which is the name of the |
616 |
Perl class implementing the model. This class is usually one of the |
617 |
C<AnyEvent::Impl:xxx> modules, but can be any other class in the case |
618 |
AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>). |
619 |
|
620 |
The known classes so far are: |
621 |
|
622 |
AnyEvent::Impl::EV based on EV (an interface to libev, best choice). |
623 |
AnyEvent::Impl::Event based on Event, second best choice. |
624 |
AnyEvent::Impl::Perl pure-perl implementation, fast and portable. |
625 |
AnyEvent::Impl::Glib based on Glib, third-best choice. |
626 |
AnyEvent::Impl::Tk based on Tk, very bad choice. |
627 |
AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs). |
628 |
AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse. |
629 |
AnyEvent::Impl::POE based on POE, not generic enough for full support. |
630 |
|
631 |
There is no support for WxWidgets, as WxWidgets has no support for |
632 |
watching file handles. However, you can use WxWidgets through the |
633 |
POE Adaptor, as POE has a Wx backend that simply polls 20 times per |
634 |
second, which was considered to be too horrible to even consider for |
635 |
AnyEvent. Likewise, other POE backends can be used by AnyEvent by using |
636 |
it's adaptor. |
637 |
|
638 |
AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when |
639 |
autodetecting them. |
640 |
|
641 |
=item AnyEvent::detect |
642 |
|
643 |
Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model |
644 |
if necessary. You should only call this function right before you would |
645 |
have created an AnyEvent watcher anyway, that is, as late as possible at |
646 |
runtime. |
647 |
|
648 |
=item $guard = AnyEvent::post_detect { BLOCK } |
649 |
|
650 |
Arranges for the code block to be executed as soon as the event model is |
651 |
autodetected (or immediately if this has already happened). |
652 |
|
653 |
If called in scalar or list context, then it creates and returns an object |
654 |
that automatically removes the callback again when it is destroyed. See |
655 |
L<Coro::BDB> for a case where this is useful. |
656 |
|
657 |
=item @AnyEvent::post_detect |
658 |
|
659 |
If there are any code references in this array (you can C<push> to it |
660 |
before or after loading AnyEvent), then they will called directly after |
661 |
the event loop has been chosen. |
662 |
|
663 |
You should check C<$AnyEvent::MODEL> before adding to this array, though: |
664 |
if it contains a true value then the event loop has already been detected, |
665 |
and the array will be ignored. |
666 |
|
667 |
Best use C<AnyEvent::post_detect { BLOCK }> instead. |
668 |
|
669 |
=back |
670 |
|
671 |
=head1 WHAT TO DO IN A MODULE |
672 |
|
673 |
As a module author, you should C<use AnyEvent> and call AnyEvent methods |
674 |
freely, but you should not load a specific event module or rely on it. |
675 |
|
676 |
Be careful when you create watchers in the module body - AnyEvent will |
677 |
decide which event module to use as soon as the first method is called, so |
678 |
by calling AnyEvent in your module body you force the user of your module |
679 |
to load the event module first. |
680 |
|
681 |
Never call C<< ->recv >> on a condition variable unless you I<know> that |
682 |
the C<< ->send >> method has been called on it already. This is |
683 |
because it will stall the whole program, and the whole point of using |
684 |
events is to stay interactive. |
685 |
|
686 |
It is fine, however, to call C<< ->recv >> when the user of your module |
687 |
requests it (i.e. if you create a http request object ad have a method |
688 |
called C<results> that returns the results, it should call C<< ->recv >> |
689 |
freely, as the user of your module knows what she is doing. always). |
690 |
|
691 |
=head1 WHAT TO DO IN THE MAIN PROGRAM |
692 |
|
693 |
There will always be a single main program - the only place that should |
694 |
dictate which event model to use. |
695 |
|
696 |
If it doesn't care, it can just "use AnyEvent" and use it itself, or not |
697 |
do anything special (it does not need to be event-based) and let AnyEvent |
698 |
decide which implementation to chose if some module relies on it. |
699 |
|
700 |
If the main program relies on a specific event model - for example, in |
701 |
Gtk2 programs you have to rely on the Glib module - you should load the |
702 |
event module before loading AnyEvent or any module that uses it: generally |
703 |
speaking, you should load it as early as possible. The reason is that |
704 |
modules might create watchers when they are loaded, and AnyEvent will |
705 |
decide on the event model to use as soon as it creates watchers, and it |
706 |
might chose the wrong one unless you load the correct one yourself. |
707 |
|
708 |
You can chose to use a pure-perl implementation by loading the |
709 |
C<AnyEvent::Impl::Perl> module, which gives you similar behaviour |
710 |
everywhere, but letting AnyEvent chose the model is generally better. |
711 |
|
712 |
=head2 MAINLOOP EMULATION |
713 |
|
714 |
Sometimes (often for short test scripts, or even standalone programs who |
715 |
only want to use AnyEvent), you do not want to run a specific event loop. |
716 |
|
717 |
In that case, you can use a condition variable like this: |
718 |
|
719 |
AnyEvent->condvar->recv; |
720 |
|
721 |
This has the effect of entering the event loop and looping forever. |
722 |
|
723 |
Note that usually your program has some exit condition, in which case |
724 |
it is better to use the "traditional" approach of storing a condition |
725 |
variable somewhere, waiting for it, and sending it when the program should |
726 |
exit cleanly. |
727 |
|
728 |
|
729 |
=head1 OTHER MODULES |
730 |
|
731 |
The following is a non-exhaustive list of additional modules that use |
732 |
AnyEvent and can therefore be mixed easily with other AnyEvent modules |
733 |
in the same program. Some of the modules come with AnyEvent, some are |
734 |
available via CPAN. |
735 |
|
736 |
=over 4 |
737 |
|
738 |
=item L<AnyEvent::Util> |
739 |
|
740 |
Contains various utility functions that replace often-used but blocking |
741 |
functions such as C<inet_aton> by event-/callback-based versions. |
742 |
|
743 |
=item L<AnyEvent::Handle> |
744 |
|
745 |
Provide read and write buffers and manages watchers for reads and writes. |
746 |
|
747 |
=item L<AnyEvent::Socket> |
748 |
|
749 |
Provides various utility functions for (internet protocol) sockets, |
750 |
addresses and name resolution. Also functions to create non-blocking tcp |
751 |
connections or tcp servers, with IPv6 and SRV record support and more. |
752 |
|
753 |
=item L<AnyEvent::DNS> |
754 |
|
755 |
Provides rich asynchronous DNS resolver capabilities. |
756 |
|
757 |
=item L<AnyEvent::HTTPD> |
758 |
|
759 |
Provides a simple web application server framework. |
760 |
|
761 |
=item L<AnyEvent::FastPing> |
762 |
|
763 |
The fastest ping in the west. |
764 |
|
765 |
=item L<Net::IRC3> |
766 |
|
767 |
AnyEvent based IRC client module family. |
768 |
|
769 |
=item L<Net::XMPP2> |
770 |
|
771 |
AnyEvent based XMPP (Jabber protocol) module family. |
772 |
|
773 |
=item L<Net::FCP> |
774 |
|
775 |
AnyEvent-based implementation of the Freenet Client Protocol, birthplace |
776 |
of AnyEvent. |
777 |
|
778 |
=item L<Event::ExecFlow> |
779 |
|
780 |
High level API for event-based execution flow control. |
781 |
|
782 |
=item L<Coro> |
783 |
|
784 |
Has special support for AnyEvent via L<Coro::AnyEvent>. |
785 |
|
786 |
=item L<AnyEvent::AIO>, L<IO::AIO> |
787 |
|
788 |
Truly asynchronous I/O, should be in the toolbox of every event |
789 |
programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent |
790 |
together. |
791 |
|
792 |
=item L<AnyEvent::BDB>, L<BDB> |
793 |
|
794 |
Truly asynchronous Berkeley DB access. AnyEvent::AIO transparently fuses |
795 |
IO::AIO and AnyEvent together. |
796 |
|
797 |
=item L<IO::Lambda> |
798 |
|
799 |
The lambda approach to I/O - don't ask, look there. Can use AnyEvent. |
800 |
|
801 |
=back |
802 |
|
803 |
=cut |
804 |
|
805 |
package AnyEvent; |
806 |
|
807 |
no warnings; |
808 |
use strict; |
809 |
|
810 |
use Carp; |
811 |
|
812 |
our $VERSION = 4.11; |
813 |
our $MODEL; |
814 |
|
815 |
our $AUTOLOAD; |
816 |
our @ISA; |
817 |
|
818 |
our @REGISTRY; |
819 |
|
820 |
our $WIN32; |
821 |
|
822 |
BEGIN { |
823 |
my $win32 = ! ! ($^O =~ /mswin32/i); |
824 |
eval "sub WIN32(){ $win32 }"; |
825 |
} |
826 |
|
827 |
our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1; |
828 |
|
829 |
our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred |
830 |
|
831 |
{ |
832 |
my $idx; |
833 |
$PROTOCOL{$_} = ++$idx |
834 |
for reverse split /\s*,\s*/, |
835 |
$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6"; |
836 |
} |
837 |
|
838 |
my @models = ( |
839 |
[EV:: => AnyEvent::Impl::EV::], |
840 |
[Event:: => AnyEvent::Impl::Event::], |
841 |
[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::], |
842 |
# everything below here will not be autoprobed |
843 |
# as the pureperl backend should work everywhere |
844 |
# and is usually faster |
845 |
[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles |
846 |
[Glib:: => AnyEvent::Impl::Glib::], # becomes extremely slow with many watchers |
847 |
[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy |
848 |
[Qt:: => AnyEvent::Impl::Qt::], # requires special main program |
849 |
[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza |
850 |
[Wx:: => AnyEvent::Impl::POE::], |
851 |
[Prima:: => AnyEvent::Impl::POE::], |
852 |
); |
853 |
|
854 |
our %method = map +($_ => 1), qw(io timer time now signal child condvar one_event DESTROY); |
855 |
|
856 |
our @post_detect; |
857 |
|
858 |
sub post_detect(&) { |
859 |
my ($cb) = @_; |
860 |
|
861 |
if ($MODEL) { |
862 |
$cb->(); |
863 |
|
864 |
1 |
865 |
} else { |
866 |
push @post_detect, $cb; |
867 |
|
868 |
defined wantarray |
869 |
? bless \$cb, "AnyEvent::Util::PostDetect" |
870 |
: () |
871 |
} |
872 |
} |
873 |
|
874 |
sub AnyEvent::Util::PostDetect::DESTROY { |
875 |
@post_detect = grep $_ != ${$_[0]}, @post_detect; |
876 |
} |
877 |
|
878 |
sub detect() { |
879 |
unless ($MODEL) { |
880 |
no strict 'refs'; |
881 |
local $SIG{__DIE__}; |
882 |
|
883 |
if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) { |
884 |
my $model = "AnyEvent::Impl::$1"; |
885 |
if (eval "require $model") { |
886 |
$MODEL = $model; |
887 |
warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1; |
888 |
} else { |
889 |
warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose; |
890 |
} |
891 |
} |
892 |
|
893 |
# check for already loaded models |
894 |
unless ($MODEL) { |
895 |
for (@REGISTRY, @models) { |
896 |
my ($package, $model) = @$_; |
897 |
if (${"$package\::VERSION"} > 0) { |
898 |
if (eval "require $model") { |
899 |
$MODEL = $model; |
900 |
warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1; |
901 |
last; |
902 |
} |
903 |
} |
904 |
} |
905 |
|
906 |
unless ($MODEL) { |
907 |
# try to load a model |
908 |
|
909 |
for (@REGISTRY, @models) { |
910 |
my ($package, $model) = @$_; |
911 |
if (eval "require $package" |
912 |
and ${"$package\::VERSION"} > 0 |
913 |
and eval "require $model") { |
914 |
$MODEL = $model; |
915 |
warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1; |
916 |
last; |
917 |
} |
918 |
} |
919 |
|
920 |
$MODEL |
921 |
or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib."; |
922 |
} |
923 |
} |
924 |
|
925 |
unshift @ISA, $MODEL; |
926 |
push @{"$MODEL\::ISA"}, "AnyEvent::Base"; |
927 |
|
928 |
(shift @post_detect)->() while @post_detect; |
929 |
} |
930 |
|
931 |
$MODEL |
932 |
} |
933 |
|
934 |
sub AUTOLOAD { |
935 |
(my $func = $AUTOLOAD) =~ s/.*://; |
936 |
|
937 |
$method{$func} |
938 |
or croak "$func: not a valid method for AnyEvent objects"; |
939 |
|
940 |
detect unless $MODEL; |
941 |
|
942 |
my $class = shift; |
943 |
$class->$func (@_); |
944 |
} |
945 |
|
946 |
package AnyEvent::Base; |
947 |
|
948 |
# default implementation for now and time |
949 |
|
950 |
use Time::HiRes (); |
951 |
|
952 |
sub time { Time::HiRes::time } |
953 |
sub now { Time::HiRes::time } |
954 |
|
955 |
# default implementation for ->condvar |
956 |
|
957 |
sub condvar { |
958 |
bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, AnyEvent::CondVar:: |
959 |
} |
960 |
|
961 |
# default implementation for ->signal |
962 |
|
963 |
our %SIG_CB; |
964 |
|
965 |
sub signal { |
966 |
my (undef, %arg) = @_; |
967 |
|
968 |
my $signal = uc $arg{signal} |
969 |
or Carp::croak "required option 'signal' is missing"; |
970 |
|
971 |
$SIG_CB{$signal}{$arg{cb}} = $arg{cb}; |
972 |
$SIG{$signal} ||= sub { |
973 |
$_->() for values %{ $SIG_CB{$signal} || {} }; |
974 |
}; |
975 |
|
976 |
bless [$signal, $arg{cb}], "AnyEvent::Base::Signal" |
977 |
} |
978 |
|
979 |
sub AnyEvent::Base::Signal::DESTROY { |
980 |
my ($signal, $cb) = @{$_[0]}; |
981 |
|
982 |
delete $SIG_CB{$signal}{$cb}; |
983 |
|
984 |
$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} }; |
985 |
} |
986 |
|
987 |
# default implementation for ->child |
988 |
|
989 |
our %PID_CB; |
990 |
our $CHLD_W; |
991 |
our $CHLD_DELAY_W; |
992 |
our $PID_IDLE; |
993 |
our $WNOHANG; |
994 |
|
995 |
sub _child_wait { |
996 |
while (0 < (my $pid = waitpid -1, $WNOHANG)) { |
997 |
$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }), |
998 |
(values %{ $PID_CB{0} || {} }); |
999 |
} |
1000 |
|
1001 |
undef $PID_IDLE; |
1002 |
} |
1003 |
|
1004 |
sub _sigchld { |
1005 |
# make sure we deliver these changes "synchronous" with the event loop. |
1006 |
$CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub { |
1007 |
undef $CHLD_DELAY_W; |
1008 |
&_child_wait; |
1009 |
}); |
1010 |
} |
1011 |
|
1012 |
sub child { |
1013 |
my (undef, %arg) = @_; |
1014 |
|
1015 |
defined (my $pid = $arg{pid} + 0) |
1016 |
or Carp::croak "required option 'pid' is missing"; |
1017 |
|
1018 |
$PID_CB{$pid}{$arg{cb}} = $arg{cb}; |
1019 |
|
1020 |
unless ($WNOHANG) { |
1021 |
$WNOHANG = eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1; |
1022 |
} |
1023 |
|
1024 |
unless ($CHLD_W) { |
1025 |
$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld); |
1026 |
# child could be a zombie already, so make at least one round |
1027 |
&_sigchld; |
1028 |
} |
1029 |
|
1030 |
bless [$pid, $arg{cb}], "AnyEvent::Base::Child" |
1031 |
} |
1032 |
|
1033 |
sub AnyEvent::Base::Child::DESTROY { |
1034 |
my ($pid, $cb) = @{$_[0]}; |
1035 |
|
1036 |
delete $PID_CB{$pid}{$cb}; |
1037 |
delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} }; |
1038 |
|
1039 |
undef $CHLD_W unless keys %PID_CB; |
1040 |
} |
1041 |
|
1042 |
package AnyEvent::CondVar; |
1043 |
|
1044 |
our @ISA = AnyEvent::CondVar::Base::; |
1045 |
|
1046 |
package AnyEvent::CondVar::Base; |
1047 |
|
1048 |
use overload |
1049 |
'&{}' => sub { my $self = shift; sub { $self->send (@_) } }, |
1050 |
fallback => 1; |
1051 |
|
1052 |
sub _send { |
1053 |
# nop |
1054 |
} |
1055 |
|
1056 |
sub send { |
1057 |
my $cv = shift; |
1058 |
$cv->{_ae_sent} = [@_]; |
1059 |
(delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb}; |
1060 |
$cv->_send; |
1061 |
} |
1062 |
|
1063 |
sub croak { |
1064 |
$_[0]{_ae_croak} = $_[1]; |
1065 |
$_[0]->send; |
1066 |
} |
1067 |
|
1068 |
sub ready { |
1069 |
$_[0]{_ae_sent} |
1070 |
} |
1071 |
|
1072 |
sub _wait { |
1073 |
AnyEvent->one_event while !$_[0]{_ae_sent}; |
1074 |
} |
1075 |
|
1076 |
sub recv { |
1077 |
$_[0]->_wait; |
1078 |
|
1079 |
Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak}; |
1080 |
wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0] |
1081 |
} |
1082 |
|
1083 |
sub cb { |
1084 |
$_[0]{_ae_cb} = $_[1] if @_ > 1; |
1085 |
$_[0]{_ae_cb} |
1086 |
} |
1087 |
|
1088 |
sub begin { |
1089 |
++$_[0]{_ae_counter}; |
1090 |
$_[0]{_ae_end_cb} = $_[1] if @_ > 1; |
1091 |
} |
1092 |
|
1093 |
sub end { |
1094 |
return if --$_[0]{_ae_counter}; |
1095 |
&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } }; |
1096 |
} |
1097 |
|
1098 |
# undocumented/compatibility with pre-3.4 |
1099 |
*broadcast = \&send; |
1100 |
*wait = \&_wait; |
1101 |
|
1102 |
=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE |
1103 |
|
1104 |
This is an advanced topic that you do not normally need to use AnyEvent in |
1105 |
a module. This section is only of use to event loop authors who want to |
1106 |
provide AnyEvent compatibility. |
1107 |
|
1108 |
If you need to support another event library which isn't directly |
1109 |
supported by AnyEvent, you can supply your own interface to it by |
1110 |
pushing, before the first watcher gets created, the package name of |
1111 |
the event module and the package name of the interface to use onto |
1112 |
C<@AnyEvent::REGISTRY>. You can do that before and even without loading |
1113 |
AnyEvent, so it is reasonably cheap. |
1114 |
|
1115 |
Example: |
1116 |
|
1117 |
push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::]; |
1118 |
|
1119 |
This tells AnyEvent to (literally) use the C<urxvt::anyevent::> |
1120 |
package/class when it finds the C<urxvt> package/module is already loaded. |
1121 |
|
1122 |
When AnyEvent is loaded and asked to find a suitable event model, it |
1123 |
will first check for the presence of urxvt by trying to C<use> the |
1124 |
C<urxvt::anyevent> module. |
1125 |
|
1126 |
The class should provide implementations for all watcher types. See |
1127 |
L<AnyEvent::Impl::EV> (source code), L<AnyEvent::Impl::Glib> (Source code) |
1128 |
and so on for actual examples. Use C<perldoc -m AnyEvent::Impl::Glib> to |
1129 |
see the sources. |
1130 |
|
1131 |
If you don't provide C<signal> and C<child> watchers than AnyEvent will |
1132 |
provide suitable (hopefully) replacements. |
1133 |
|
1134 |
The above example isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt) |
1135 |
terminal emulator uses the above line as-is. An interface isn't included |
1136 |
in AnyEvent because it doesn't make sense outside the embedded interpreter |
1137 |
inside I<rxvt-unicode>, and it is updated and maintained as part of the |
1138 |
I<rxvt-unicode> distribution. |
1139 |
|
1140 |
I<rxvt-unicode> also cheats a bit by not providing blocking access to |
1141 |
condition variables: code blocking while waiting for a condition will |
1142 |
C<die>. This still works with most modules/usages, and blocking calls must |
1143 |
not be done in an interactive application, so it makes sense. |
1144 |
|
1145 |
=head1 ENVIRONMENT VARIABLES |
1146 |
|
1147 |
The following environment variables are used by this module: |
1148 |
|
1149 |
=over 4 |
1150 |
|
1151 |
=item C<PERL_ANYEVENT_VERBOSE> |
1152 |
|
1153 |
By default, AnyEvent will be completely silent except in fatal |
1154 |
conditions. You can set this environment variable to make AnyEvent more |
1155 |
talkative. |
1156 |
|
1157 |
When set to C<1> or higher, causes AnyEvent to warn about unexpected |
1158 |
conditions, such as not being able to load the event model specified by |
1159 |
C<PERL_ANYEVENT_MODEL>. |
1160 |
|
1161 |
When set to C<2> or higher, cause AnyEvent to report to STDERR which event |
1162 |
model it chooses. |
1163 |
|
1164 |
=item C<PERL_ANYEVENT_MODEL> |
1165 |
|
1166 |
This can be used to specify the event model to be used by AnyEvent, before |
1167 |
auto detection and -probing kicks in. It must be a string consisting |
1168 |
entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended |
1169 |
and the resulting module name is loaded and if the load was successful, |
1170 |
used as event model. If it fails to load AnyEvent will proceed with |
1171 |
auto detection and -probing. |
1172 |
|
1173 |
This functionality might change in future versions. |
1174 |
|
1175 |
For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you |
1176 |
could start your program like this: |
1177 |
|
1178 |
PERL_ANYEVENT_MODEL=Perl perl ... |
1179 |
|
1180 |
=item C<PERL_ANYEVENT_PROTOCOLS> |
1181 |
|
1182 |
Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences |
1183 |
for IPv4 or IPv6. The default is unspecified (and might change, or be the result |
1184 |
of auto probing). |
1185 |
|
1186 |
Must be set to a comma-separated list of protocols or address families, |
1187 |
current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be |
1188 |
used, and preference will be given to protocols mentioned earlier in the |
1189 |
list. |
1190 |
|
1191 |
This variable can effectively be used for denial-of-service attacks |
1192 |
against local programs (e.g. when setuid), although the impact is likely |
1193 |
small, as the program has to handle connection errors already- |
1194 |
|
1195 |
Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6, |
1196 |
but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4> |
1197 |
- only support IPv4, never try to resolve or contact IPv6 |
1198 |
addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or |
1199 |
IPv6, but prefer IPv6 over IPv4. |
1200 |
|
1201 |
=item C<PERL_ANYEVENT_EDNS0> |
1202 |
|
1203 |
Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension |
1204 |
for DNS. This extension is generally useful to reduce DNS traffic, but |
1205 |
some (broken) firewalls drop such DNS packets, which is why it is off by |
1206 |
default. |
1207 |
|
1208 |
Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce |
1209 |
EDNS0 in its DNS requests. |
1210 |
|
1211 |
=item C<PERL_ANYEVENT_MAX_FORKS> |
1212 |
|
1213 |
The maximum number of child processes that C<AnyEvent::Util::fork_call> |
1214 |
will create in parallel. |
1215 |
|
1216 |
=back |
1217 |
|
1218 |
=head1 EXAMPLE PROGRAM |
1219 |
|
1220 |
The following program uses an I/O watcher to read data from STDIN, a timer |
1221 |
to display a message once per second, and a condition variable to quit the |
1222 |
program when the user enters quit: |
1223 |
|
1224 |
use AnyEvent; |
1225 |
|
1226 |
my $cv = AnyEvent->condvar; |
1227 |
|
1228 |
my $io_watcher = AnyEvent->io ( |
1229 |
fh => \*STDIN, |
1230 |
poll => 'r', |
1231 |
cb => sub { |
1232 |
warn "io event <$_[0]>\n"; # will always output <r> |
1233 |
chomp (my $input = <STDIN>); # read a line |
1234 |
warn "read: $input\n"; # output what has been read |
1235 |
$cv->send if $input =~ /^q/i; # quit program if /^q/i |
1236 |
}, |
1237 |
); |
1238 |
|
1239 |
my $time_watcher; # can only be used once |
1240 |
|
1241 |
sub new_timer { |
1242 |
$timer = AnyEvent->timer (after => 1, cb => sub { |
1243 |
warn "timeout\n"; # print 'timeout' about every second |
1244 |
&new_timer; # and restart the time |
1245 |
}); |
1246 |
} |
1247 |
|
1248 |
new_timer; # create first timer |
1249 |
|
1250 |
$cv->recv; # wait until user enters /^q/i |
1251 |
|
1252 |
=head1 REAL-WORLD EXAMPLE |
1253 |
|
1254 |
Consider the L<Net::FCP> module. It features (among others) the following |
1255 |
API calls, which are to freenet what HTTP GET requests are to http: |
1256 |
|
1257 |
my $data = $fcp->client_get ($url); # blocks |
1258 |
|
1259 |
my $transaction = $fcp->txn_client_get ($url); # does not block |
1260 |
$transaction->cb ( sub { ... } ); # set optional result callback |
1261 |
my $data = $transaction->result; # possibly blocks |
1262 |
|
1263 |
The C<client_get> method works like C<LWP::Simple::get>: it requests the |
1264 |
given URL and waits till the data has arrived. It is defined to be: |
1265 |
|
1266 |
sub client_get { $_[0]->txn_client_get ($_[1])->result } |
1267 |
|
1268 |
And in fact is automatically generated. This is the blocking API of |
1269 |
L<Net::FCP>, and it works as simple as in any other, similar, module. |
1270 |
|
1271 |
More complicated is C<txn_client_get>: It only creates a transaction |
1272 |
(completion, result, ...) object and initiates the transaction. |
1273 |
|
1274 |
my $txn = bless { }, Net::FCP::Txn::; |
1275 |
|
1276 |
It also creates a condition variable that is used to signal the completion |
1277 |
of the request: |
1278 |
|
1279 |
$txn->{finished} = AnyAvent->condvar; |
1280 |
|
1281 |
It then creates a socket in non-blocking mode. |
1282 |
|
1283 |
socket $txn->{fh}, ...; |
1284 |
fcntl $txn->{fh}, F_SETFL, O_NONBLOCK; |
1285 |
connect $txn->{fh}, ... |
1286 |
and !$!{EWOULDBLOCK} |
1287 |
and !$!{EINPROGRESS} |
1288 |
and Carp::croak "unable to connect: $!\n"; |
1289 |
|
1290 |
Then it creates a write-watcher which gets called whenever an error occurs |
1291 |
or the connection succeeds: |
1292 |
|
1293 |
$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'w', cb => sub { $txn->fh_ready_w }); |
1294 |
|
1295 |
And returns this transaction object. The C<fh_ready_w> callback gets |
1296 |
called as soon as the event loop detects that the socket is ready for |
1297 |
writing. |
1298 |
|
1299 |
The C<fh_ready_w> method makes the socket blocking again, writes the |
1300 |
request data and replaces the watcher by a read watcher (waiting for reply |
1301 |
data). The actual code is more complicated, but that doesn't matter for |
1302 |
this example: |
1303 |
|
1304 |
fcntl $txn->{fh}, F_SETFL, 0; |
1305 |
syswrite $txn->{fh}, $txn->{request} |
1306 |
or die "connection or write error"; |
1307 |
$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r }); |
1308 |
|
1309 |
Again, C<fh_ready_r> waits till all data has arrived, and then stores the |
1310 |
result and signals any possible waiters that the request has finished: |
1311 |
|
1312 |
sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf}; |
1313 |
|
1314 |
if (end-of-file or data complete) { |
1315 |
$txn->{result} = $txn->{buf}; |
1316 |
$txn->{finished}->send; |
1317 |
$txb->{cb}->($txn) of $txn->{cb}; # also call callback |
1318 |
} |
1319 |
|
1320 |
The C<result> method, finally, just waits for the finished signal (if the |
1321 |
request was already finished, it doesn't wait, of course, and returns the |
1322 |
data: |
1323 |
|
1324 |
$txn->{finished}->recv; |
1325 |
return $txn->{result}; |
1326 |
|
1327 |
The actual code goes further and collects all errors (C<die>s, exceptions) |
1328 |
that occurred during request processing. The C<result> method detects |
1329 |
whether an exception as thrown (it is stored inside the $txn object) |
1330 |
and just throws the exception, which means connection errors and other |
1331 |
problems get reported tot he code that tries to use the result, not in a |
1332 |
random callback. |
1333 |
|
1334 |
All of this enables the following usage styles: |
1335 |
|
1336 |
1. Blocking: |
1337 |
|
1338 |
my $data = $fcp->client_get ($url); |
1339 |
|
1340 |
2. Blocking, but running in parallel: |
1341 |
|
1342 |
my @datas = map $_->result, |
1343 |
map $fcp->txn_client_get ($_), |
1344 |
@urls; |
1345 |
|
1346 |
Both blocking examples work without the module user having to know |
1347 |
anything about events. |
1348 |
|
1349 |
3a. Event-based in a main program, using any supported event module: |
1350 |
|
1351 |
use EV; |
1352 |
|
1353 |
$fcp->txn_client_get ($url)->cb (sub { |
1354 |
my $txn = shift; |
1355 |
my $data = $txn->result; |
1356 |
... |
1357 |
}); |
1358 |
|
1359 |
EV::loop; |
1360 |
|
1361 |
3b. The module user could use AnyEvent, too: |
1362 |
|
1363 |
use AnyEvent; |
1364 |
|
1365 |
my $quit = AnyEvent->condvar; |
1366 |
|
1367 |
$fcp->txn_client_get ($url)->cb (sub { |
1368 |
... |
1369 |
$quit->send; |
1370 |
}); |
1371 |
|
1372 |
$quit->recv; |
1373 |
|
1374 |
|
1375 |
=head1 BENCHMARKS |
1376 |
|
1377 |
To give you an idea of the performance and overheads that AnyEvent adds |
1378 |
over the event loops themselves and to give you an impression of the speed |
1379 |
of various event loops I prepared some benchmarks. |
1380 |
|
1381 |
=head2 BENCHMARKING ANYEVENT OVERHEAD |
1382 |
|
1383 |
Here is a benchmark of various supported event models used natively and |
1384 |
through AnyEvent. The benchmark creates a lot of timers (with a zero |
1385 |
timeout) and I/O watchers (watching STDOUT, a pty, to become writable, |
1386 |
which it is), lets them fire exactly once and destroys them again. |
1387 |
|
1388 |
Source code for this benchmark is found as F<eg/bench> in the AnyEvent |
1389 |
distribution. |
1390 |
|
1391 |
=head3 Explanation of the columns |
1392 |
|
1393 |
I<watcher> is the number of event watchers created/destroyed. Since |
1394 |
different event models feature vastly different performances, each event |
1395 |
loop was given a number of watchers so that overall runtime is acceptable |
1396 |
and similar between tested event loop (and keep them from crashing): Glib |
1397 |
would probably take thousands of years if asked to process the same number |
1398 |
of watchers as EV in this benchmark. |
1399 |
|
1400 |
I<bytes> is the number of bytes (as measured by the resident set size, |
1401 |
RSS) consumed by each watcher. This method of measuring captures both C |
1402 |
and Perl-based overheads. |
1403 |
|
1404 |
I<create> is the time, in microseconds (millionths of seconds), that it |
1405 |
takes to create a single watcher. The callback is a closure shared between |
1406 |
all watchers, to avoid adding memory overhead. That means closure creation |
1407 |
and memory usage is not included in the figures. |
1408 |
|
1409 |
I<invoke> is the time, in microseconds, used to invoke a simple |
1410 |
callback. The callback simply counts down a Perl variable and after it was |
1411 |
invoked "watcher" times, it would C<< ->send >> a condvar once to |
1412 |
signal the end of this phase. |
1413 |
|
1414 |
I<destroy> is the time, in microseconds, that it takes to destroy a single |
1415 |
watcher. |
1416 |
|
1417 |
=head3 Results |
1418 |
|
1419 |
name watchers bytes create invoke destroy comment |
1420 |
EV/EV 400000 244 0.56 0.46 0.31 EV native interface |
1421 |
EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers |
1422 |
CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal |
1423 |
Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation |
1424 |
Event/Event 16000 516 31.88 31.30 0.85 Event native interface |
1425 |
Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers |
1426 |
Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour |
1427 |
Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers |
1428 |
POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event |
1429 |
POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select |
1430 |
|
1431 |
=head3 Discussion |
1432 |
|
1433 |
The benchmark does I<not> measure scalability of the event loop very |
1434 |
well. For example, a select-based event loop (such as the pure perl one) |
1435 |
can never compete with an event loop that uses epoll when the number of |
1436 |
file descriptors grows high. In this benchmark, all events become ready at |
1437 |
the same time, so select/poll-based implementations get an unnatural speed |
1438 |
boost. |
1439 |
|
1440 |
Also, note that the number of watchers usually has a nonlinear effect on |
1441 |
overall speed, that is, creating twice as many watchers doesn't take twice |
1442 |
the time - usually it takes longer. This puts event loops tested with a |
1443 |
higher number of watchers at a disadvantage. |
1444 |
|
1445 |
To put the range of results into perspective, consider that on the |
1446 |
benchmark machine, handling an event takes roughly 1600 CPU cycles with |
1447 |
EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU |
1448 |
cycles with POE. |
1449 |
|
1450 |
C<EV> is the sole leader regarding speed and memory use, which are both |
1451 |
maximal/minimal, respectively. Even when going through AnyEvent, it uses |
1452 |
far less memory than any other event loop and is still faster than Event |
1453 |
natively. |
1454 |
|
1455 |
The pure perl implementation is hit in a few sweet spots (both the |
1456 |
constant timeout and the use of a single fd hit optimisations in the perl |
1457 |
interpreter and the backend itself). Nevertheless this shows that it |
1458 |
adds very little overhead in itself. Like any select-based backend its |
1459 |
performance becomes really bad with lots of file descriptors (and few of |
1460 |
them active), of course, but this was not subject of this benchmark. |
1461 |
|
1462 |
The C<Event> module has a relatively high setup and callback invocation |
1463 |
cost, but overall scores in on the third place. |
1464 |
|
1465 |
C<Glib>'s memory usage is quite a bit higher, but it features a |
1466 |
faster callback invocation and overall ends up in the same class as |
1467 |
C<Event>. However, Glib scales extremely badly, doubling the number of |
1468 |
watchers increases the processing time by more than a factor of four, |
1469 |
making it completely unusable when using larger numbers of watchers |
1470 |
(note that only a single file descriptor was used in the benchmark, so |
1471 |
inefficiencies of C<poll> do not account for this). |
1472 |
|
1473 |
The C<Tk> adaptor works relatively well. The fact that it crashes with |
1474 |
more than 2000 watchers is a big setback, however, as correctness takes |
1475 |
precedence over speed. Nevertheless, its performance is surprising, as the |
1476 |
file descriptor is dup()ed for each watcher. This shows that the dup() |
1477 |
employed by some adaptors is not a big performance issue (it does incur a |
1478 |
hidden memory cost inside the kernel which is not reflected in the figures |
1479 |
above). |
1480 |
|
1481 |
C<POE>, regardless of underlying event loop (whether using its pure perl |
1482 |
select-based backend or the Event module, the POE-EV backend couldn't |
1483 |
be tested because it wasn't working) shows abysmal performance and |
1484 |
memory usage with AnyEvent: Watchers use almost 30 times as much memory |
1485 |
as EV watchers, and 10 times as much memory as Event (the high memory |
1486 |
requirements are caused by requiring a session for each watcher). Watcher |
1487 |
invocation speed is almost 900 times slower than with AnyEvent's pure perl |
1488 |
implementation. |
1489 |
|
1490 |
The design of the POE adaptor class in AnyEvent can not really account |
1491 |
for the performance issues, though, as session creation overhead is |
1492 |
small compared to execution of the state machine, which is coded pretty |
1493 |
optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that |
1494 |
using multiple sessions is not a good approach, especially regarding |
1495 |
memory usage, even the author of POE could not come up with a faster |
1496 |
design). |
1497 |
|
1498 |
=head3 Summary |
1499 |
|
1500 |
=over 4 |
1501 |
|
1502 |
=item * Using EV through AnyEvent is faster than any other event loop |
1503 |
(even when used without AnyEvent), but most event loops have acceptable |
1504 |
performance with or without AnyEvent. |
1505 |
|
1506 |
=item * The overhead AnyEvent adds is usually much smaller than the overhead of |
1507 |
the actual event loop, only with extremely fast event loops such as EV |
1508 |
adds AnyEvent significant overhead. |
1509 |
|
1510 |
=item * You should avoid POE like the plague if you want performance or |
1511 |
reasonable memory usage. |
1512 |
|
1513 |
=back |
1514 |
|
1515 |
=head2 BENCHMARKING THE LARGE SERVER CASE |
1516 |
|
1517 |
This benchmark actually benchmarks the event loop itself. It works by |
1518 |
creating a number of "servers": each server consists of a socket pair, a |
1519 |
timeout watcher that gets reset on activity (but never fires), and an I/O |
1520 |
watcher waiting for input on one side of the socket. Each time the socket |
1521 |
watcher reads a byte it will write that byte to a random other "server". |
1522 |
|
1523 |
The effect is that there will be a lot of I/O watchers, only part of which |
1524 |
are active at any one point (so there is a constant number of active |
1525 |
fds for each loop iteration, but which fds these are is random). The |
1526 |
timeout is reset each time something is read because that reflects how |
1527 |
most timeouts work (and puts extra pressure on the event loops). |
1528 |
|
1529 |
In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100 |
1530 |
(1%) are active. This mirrors the activity of large servers with many |
1531 |
connections, most of which are idle at any one point in time. |
1532 |
|
1533 |
Source code for this benchmark is found as F<eg/bench2> in the AnyEvent |
1534 |
distribution. |
1535 |
|
1536 |
=head3 Explanation of the columns |
1537 |
|
1538 |
I<sockets> is the number of sockets, and twice the number of "servers" (as |
1539 |
each server has a read and write socket end). |
1540 |
|
1541 |
I<create> is the time it takes to create a socket pair (which is |
1542 |
nontrivial) and two watchers: an I/O watcher and a timeout watcher. |
1543 |
|
1544 |
I<request>, the most important value, is the time it takes to handle a |
1545 |
single "request", that is, reading the token from the pipe and forwarding |
1546 |
it to another server. This includes deleting the old timeout and creating |
1547 |
a new one that moves the timeout into the future. |
1548 |
|
1549 |
=head3 Results |
1550 |
|
1551 |
name sockets create request |
1552 |
EV 20000 69.01 11.16 |
1553 |
Perl 20000 73.32 35.87 |
1554 |
Event 20000 212.62 257.32 |
1555 |
Glib 20000 651.16 1896.30 |
1556 |
POE 20000 349.67 12317.24 uses POE::Loop::Event |
1557 |
|
1558 |
=head3 Discussion |
1559 |
|
1560 |
This benchmark I<does> measure scalability and overall performance of the |
1561 |
particular event loop. |
1562 |
|
1563 |
EV is again fastest. Since it is using epoll on my system, the setup time |
1564 |
is relatively high, though. |
1565 |
|
1566 |
Perl surprisingly comes second. It is much faster than the C-based event |
1567 |
loops Event and Glib. |
1568 |
|
1569 |
Event suffers from high setup time as well (look at its code and you will |
1570 |
understand why). Callback invocation also has a high overhead compared to |
1571 |
the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event |
1572 |
uses select or poll in basically all documented configurations. |
1573 |
|
1574 |
Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It |
1575 |
clearly fails to perform with many filehandles or in busy servers. |
1576 |
|
1577 |
POE is still completely out of the picture, taking over 1000 times as long |
1578 |
as EV, and over 100 times as long as the Perl implementation, even though |
1579 |
it uses a C-based event loop in this case. |
1580 |
|
1581 |
=head3 Summary |
1582 |
|
1583 |
=over 4 |
1584 |
|
1585 |
=item * The pure perl implementation performs extremely well. |
1586 |
|
1587 |
=item * Avoid Glib or POE in large projects where performance matters. |
1588 |
|
1589 |
=back |
1590 |
|
1591 |
=head2 BENCHMARKING SMALL SERVERS |
1592 |
|
1593 |
While event loops should scale (and select-based ones do not...) even to |
1594 |
large servers, most programs we (or I :) actually write have only a few |
1595 |
I/O watchers. |
1596 |
|
1597 |
In this benchmark, I use the same benchmark program as in the large server |
1598 |
case, but it uses only eight "servers", of which three are active at any |
1599 |
one time. This should reflect performance for a small server relatively |
1600 |
well. |
1601 |
|
1602 |
The columns are identical to the previous table. |
1603 |
|
1604 |
=head3 Results |
1605 |
|
1606 |
name sockets create request |
1607 |
EV 16 20.00 6.54 |
1608 |
Perl 16 25.75 12.62 |
1609 |
Event 16 81.27 35.86 |
1610 |
Glib 16 32.63 15.48 |
1611 |
POE 16 261.87 276.28 uses POE::Loop::Event |
1612 |
|
1613 |
=head3 Discussion |
1614 |
|
1615 |
The benchmark tries to test the performance of a typical small |
1616 |
server. While knowing how various event loops perform is interesting, keep |
1617 |
in mind that their overhead in this case is usually not as important, due |
1618 |
to the small absolute number of watchers (that is, you need efficiency and |
1619 |
speed most when you have lots of watchers, not when you only have a few of |
1620 |
them). |
1621 |
|
1622 |
EV is again fastest. |
1623 |
|
1624 |
Perl again comes second. It is noticeably faster than the C-based event |
1625 |
loops Event and Glib, although the difference is too small to really |
1626 |
matter. |
1627 |
|
1628 |
POE also performs much better in this case, but is is still far behind the |
1629 |
others. |
1630 |
|
1631 |
=head3 Summary |
1632 |
|
1633 |
=over 4 |
1634 |
|
1635 |
=item * C-based event loops perform very well with small number of |
1636 |
watchers, as the management overhead dominates. |
1637 |
|
1638 |
=back |
1639 |
|
1640 |
|
1641 |
=head1 FORK |
1642 |
|
1643 |
Most event libraries are not fork-safe. The ones who are usually are |
1644 |
because they rely on inefficient but fork-safe C<select> or C<poll> |
1645 |
calls. Only L<EV> is fully fork-aware. |
1646 |
|
1647 |
If you have to fork, you must either do so I<before> creating your first |
1648 |
watcher OR you must not use AnyEvent at all in the child. |
1649 |
|
1650 |
|
1651 |
=head1 SECURITY CONSIDERATIONS |
1652 |
|
1653 |
AnyEvent can be forced to load any event model via |
1654 |
$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to |
1655 |
execute arbitrary code or directly gain access, it can easily be used to |
1656 |
make the program hang or malfunction in subtle ways, as AnyEvent watchers |
1657 |
will not be active when the program uses a different event model than |
1658 |
specified in the variable. |
1659 |
|
1660 |
You can make AnyEvent completely ignore this variable by deleting it |
1661 |
before the first watcher gets created, e.g. with a C<BEGIN> block: |
1662 |
|
1663 |
BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} } |
1664 |
|
1665 |
use AnyEvent; |
1666 |
|
1667 |
Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can |
1668 |
be used to probe what backend is used and gain other information (which is |
1669 |
probably even less useful to an attacker than PERL_ANYEVENT_MODEL). |
1670 |
|
1671 |
|
1672 |
=head1 SEE ALSO |
1673 |
|
1674 |
Utility functions: L<AnyEvent::Util>. |
1675 |
|
1676 |
Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>, |
1677 |
L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>. |
1678 |
|
1679 |
Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>, |
1680 |
L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, |
1681 |
L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>, |
1682 |
L<AnyEvent::Impl::POE>. |
1683 |
|
1684 |
Non-blocking file handles, sockets, TCP clients and |
1685 |
servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>. |
1686 |
|
1687 |
Asynchronous DNS: L<AnyEvent::DNS>. |
1688 |
|
1689 |
Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>, |
1690 |
|
1691 |
Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>, L<AnyEvent::DNS>. |
1692 |
|
1693 |
|
1694 |
=head1 AUTHOR |
1695 |
|
1696 |
Marc Lehmann <schmorp@schmorp.de> |
1697 |
http://home.schmorp.de/ |
1698 |
|
1699 |
=cut |
1700 |
|
1701 |
1 |
1702 |
|