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1=head1 => NAME 1=head1 NAME
2 2
3AnyEvent - provide framework for multiple event loops 3AnyEvent - provide framework for multiple event loops
4 4
5EV, Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event loops 5EV, Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event loops
6 6
7=head1 SYNOPSIS 7=head1 SYNOPSIS
8 8
9 use AnyEvent; 9 use AnyEvent;
10 10
11 my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub { 11 my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub { ... });
12 ...
13 });
14 12
15 my $w = AnyEvent->timer (after => $seconds, cb => sub { 13 my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
14 my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...
15
16 print AnyEvent->now; # prints current event loop time
17 print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
18
19 my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });
20
21 my $w = AnyEvent->child (pid => $pid, cb => sub {
22 my ($pid, $status) = @_;
16 ... 23 ...
17 }); 24 });
18 25
19 my $w = AnyEvent->condvar; # stores whether a condition was flagged 26 my $w = AnyEvent->condvar; # stores whether a condition was flagged
20 $w->send; # wake up current and all future recv's 27 $w->send; # wake up current and all future recv's
21 $w->recv; # enters "main loop" till $condvar gets ->send 28 $w->recv; # enters "main loop" till $condvar gets ->send
29 # use a condvar in callback mode:
30 $w->cb (sub { $_[0]->recv });
31
32=head1 INTRODUCTION/TUTORIAL
33
34This manpage is mainly a reference manual. If you are interested
35in a tutorial or some gentle introduction, have a look at the
36L<AnyEvent::Intro> manpage.
22 37
23=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT) 38=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
24 39
25Glib, POE, IO::Async, Event... CPAN offers event models by the dozen 40Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
26nowadays. So what is different about AnyEvent? 41nowadays. So what is different about AnyEvent?
27 42
28Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of 43Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of
29policy> and AnyEvent is I<small and efficient>. 44policy> and AnyEvent is I<small and efficient>.
30 45
31First and foremost, I<AnyEvent is not an event model> itself, it only 46First and foremost, I<AnyEvent is not an event model> itself, it only
32interfaces to whatever event model the main program happens to use in a 47interfaces to whatever event model the main program happens to use, in a
33pragmatic way. For event models and certain classes of immortals alike, 48pragmatic way. For event models and certain classes of immortals alike,
34the statement "there can only be one" is a bitter reality: In general, 49the statement "there can only be one" is a bitter reality: In general,
35only one event loop can be active at the same time in a process. AnyEvent 50only one event loop can be active at the same time in a process. AnyEvent
36helps hiding the differences between those event loops. 51cannot change this, but it can hide the differences between those event
52loops.
37 53
38The goal of AnyEvent is to offer module authors the ability to do event 54The goal of AnyEvent is to offer module authors the ability to do event
39programming (waiting for I/O or timer events) without subscribing to a 55programming (waiting for I/O or timer events) without subscribing to a
40religion, a way of living, and most importantly: without forcing your 56religion, a way of living, and most importantly: without forcing your
41module users into the same thing by forcing them to use the same event 57module users into the same thing by forcing them to use the same event
42model you use. 58model you use.
43 59
44For modules like POE or IO::Async (which is a total misnomer as it is 60For modules like POE or IO::Async (which is a total misnomer as it is
45actually doing all I/O I<synchronously>...), using them in your module is 61actually doing all I/O I<synchronously>...), using them in your module is
46like joining a cult: After you joined, you are dependent on them and you 62like joining a cult: After you joined, you are dependent on them and you
47cannot use anything else, as it is simply incompatible to everything that 63cannot use anything else, as they are simply incompatible to everything
48isn't itself. What's worse, all the potential users of your module are 64that isn't them. What's worse, all the potential users of your
49I<also> forced to use the same event loop you use. 65module are I<also> forced to use the same event loop you use.
50 66
51AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works 67AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
52fine. AnyEvent + Tk works fine etc. etc. but none of these work together 68fine. AnyEvent + Tk works fine etc. etc. but none of these work together
53with the rest: POE + IO::Async? no go. Tk + Event? no go. Again: if 69with the rest: POE + IO::Async? No go. Tk + Event? No go. Again: if
54your module uses one of those, every user of your module has to use it, 70your module uses one of those, every user of your module has to use it,
55too. But if your module uses AnyEvent, it works transparently with all 71too. But if your module uses AnyEvent, it works transparently with all
56event models it supports (including stuff like POE and IO::Async, as long 72event models it supports (including stuff like IO::Async, as long as those
57as those use one of the supported event loops. It is trivial to add new 73use one of the supported event loops. It is trivial to add new event loops
58event loops to AnyEvent, too, so it is future-proof). 74to AnyEvent, too, so it is future-proof).
59 75
60In addition to being free of having to use I<the one and only true event 76In addition to being free of having to use I<the one and only true event
61model>, AnyEvent also is free of bloat and policy: with POE or similar 77model>, AnyEvent also is free of bloat and policy: with POE or similar
62modules, you get an enourmous amount of code and strict rules you have to 78modules, you get an enormous amount of code and strict rules you have to
63follow. AnyEvent, on the other hand, is lean and up to the point, by only 79follow. AnyEvent, on the other hand, is lean and up to the point, by only
64offering the functionality that is necessary, in as thin as a wrapper as 80offering the functionality that is necessary, in as thin as a wrapper as
65technically possible. 81technically possible.
66 82
83Of course, AnyEvent comes with a big (and fully optional!) toolbox
84of useful functionality, such as an asynchronous DNS resolver, 100%
85non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms
86such as Windows) and lots of real-world knowledge and workarounds for
87platform bugs and differences.
88
67Of course, if you want lots of policy (this can arguably be somewhat 89Now, if you I<do want> lots of policy (this can arguably be somewhat
68useful) and you want to force your users to use the one and only event 90useful) and you want to force your users to use the one and only event
69model, you should I<not> use this module. 91model, you should I<not> use this module.
70 92
71=head1 DESCRIPTION 93=head1 DESCRIPTION
72 94
102starts using it, all bets are off. Maybe you should tell their authors to 124starts using it, all bets are off. Maybe you should tell their authors to
103use AnyEvent so their modules work together with others seamlessly... 125use AnyEvent so their modules work together with others seamlessly...
104 126
105The pure-perl implementation of AnyEvent is called 127The pure-perl implementation of AnyEvent is called
106C<AnyEvent::Impl::Perl>. Like other event modules you can load it 128C<AnyEvent::Impl::Perl>. Like other event modules you can load it
107explicitly. 129explicitly and enjoy the high availability of that event loop :)
108 130
109=head1 WATCHERS 131=head1 WATCHERS
110 132
111AnyEvent has the central concept of a I<watcher>, which is an object that 133AnyEvent has the central concept of a I<watcher>, which is an object that
112stores relevant data for each kind of event you are waiting for, such as 134stores relevant data for each kind of event you are waiting for, such as
113the callback to call, the filehandle to watch, etc. 135the callback to call, the file handle to watch, etc.
114 136
115These watchers are normal Perl objects with normal Perl lifetime. After 137These watchers are normal Perl objects with normal Perl lifetime. After
116creating a watcher it will immediately "watch" for events and invoke the 138creating a watcher it will immediately "watch" for events and invoke the
117callback when the event occurs (of course, only when the event model 139callback when the event occurs (of course, only when the event model
118is in control). 140is in control).
119 141
142Note that B<callbacks must not permanently change global variables>
143potentially in use by the event loop (such as C<$_> or C<$[>) and that B<<
144callbacks must not C<die> >>. The former is good programming practise in
145Perl and the latter stems from the fact that exception handling differs
146widely between event loops.
147
120To disable the watcher you have to destroy it (e.g. by setting the 148To disable the watcher you have to destroy it (e.g. by setting the
121variable you store it in to C<undef> or otherwise deleting all references 149variable you store it in to C<undef> or otherwise deleting all references
122to it). 150to it).
123 151
124All watchers are created by calling a method on the C<AnyEvent> class. 152All watchers are created by calling a method on the C<AnyEvent> class.
126Many watchers either are used with "recursion" (repeating timers for 154Many watchers either are used with "recursion" (repeating timers for
127example), or need to refer to their watcher object in other ways. 155example), or need to refer to their watcher object in other ways.
128 156
129An any way to achieve that is this pattern: 157An any way to achieve that is this pattern:
130 158
131 my $w; $w = AnyEvent->type (arg => value ..., cb => sub { 159 my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
132 # you can use $w here, for example to undef it 160 # you can use $w here, for example to undef it
133 undef $w; 161 undef $w;
134 }); 162 });
135 163
136Note that C<my $w; $w => combination. This is necessary because in Perl, 164Note that C<my $w; $w => combination. This is necessary because in Perl,
137my variables are only visible after the statement in which they are 165my variables are only visible after the statement in which they are
138declared. 166declared.
139 167
140=head2 I/O WATCHERS 168=head2 I/O WATCHERS
141 169
142You can create an I/O watcher by calling the C<< AnyEvent->io >> method 170You can create an I/O watcher by calling the C<< AnyEvent->io >> method
143with the following mandatory key-value pairs as arguments: 171with the following mandatory key-value pairs as arguments:
144 172
145C<fh> the Perl I<file handle> (I<not> file descriptor) to watch 173C<fh> is the Perl I<file handle> (I<not> file descriptor) to watch
174for events (AnyEvent might or might not keep a reference to this file
175handle). Note that only file handles pointing to things for which
176non-blocking operation makes sense are allowed. This includes sockets,
177most character devices, pipes, fifos and so on, but not for example files
178or block devices.
179
146for events. C<poll> must be a string that is either C<r> or C<w>, 180C<poll> must be a string that is either C<r> or C<w>, which creates a
147which creates a watcher waiting for "r"eadable or "w"ritable events, 181watcher waiting for "r"eadable or "w"ritable events, respectively.
182
148respectively. C<cb> is the callback to invoke each time the file handle 183C<cb> is the callback to invoke each time the file handle becomes ready.
149becomes ready.
150 184
151Although the callback might get passed parameters, their value and 185Although the callback might get passed parameters, their value and
152presence is undefined and you cannot rely on them. Portable AnyEvent 186presence is undefined and you cannot rely on them. Portable AnyEvent
153callbacks cannot use arguments passed to I/O watcher callbacks. 187callbacks cannot use arguments passed to I/O watcher callbacks.
154 188
158 192
159Some event loops issue spurious readyness notifications, so you should 193Some event loops issue spurious readyness notifications, so you should
160always use non-blocking calls when reading/writing from/to your file 194always use non-blocking calls when reading/writing from/to your file
161handles. 195handles.
162 196
163Example:
164
165 # wait for readability of STDIN, then read a line and disable the watcher 197Example: wait for readability of STDIN, then read a line and disable the
198watcher.
199
166 my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub { 200 my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
167 chomp (my $input = <STDIN>); 201 chomp (my $input = <STDIN>);
168 warn "read: $input\n"; 202 warn "read: $input\n";
169 undef $w; 203 undef $w;
170 }); 204 });
180 214
181Although the callback might get passed parameters, their value and 215Although the callback might get passed parameters, their value and
182presence is undefined and you cannot rely on them. Portable AnyEvent 216presence is undefined and you cannot rely on them. Portable AnyEvent
183callbacks cannot use arguments passed to time watcher callbacks. 217callbacks cannot use arguments passed to time watcher callbacks.
184 218
185The timer callback will be invoked at most once: if you want a repeating 219The callback will normally be invoked once only. If you specify another
186timer you have to create a new watcher (this is a limitation by both Tk 220parameter, C<interval>, as a strictly positive number (> 0), then the
187and Glib). 221callback will be invoked regularly at that interval (in fractional
222seconds) after the first invocation. If C<interval> is specified with a
223false value, then it is treated as if it were missing.
188 224
189Example: 225The callback will be rescheduled before invoking the callback, but no
226attempt is done to avoid timer drift in most backends, so the interval is
227only approximate.
190 228
191 # fire an event after 7.7 seconds 229Example: fire an event after 7.7 seconds.
230
192 my $w = AnyEvent->timer (after => 7.7, cb => sub { 231 my $w = AnyEvent->timer (after => 7.7, cb => sub {
193 warn "timeout\n"; 232 warn "timeout\n";
194 }); 233 });
195 234
196 # to cancel the timer: 235 # to cancel the timer:
197 undef $w; 236 undef $w;
198 237
199Example 2:
200
201 # fire an event after 0.5 seconds, then roughly every second 238Example 2: fire an event after 0.5 seconds, then roughly every second.
202 my $w;
203 239
204 my $cb = sub {
205 # cancel the old timer while creating a new one
206 $w = AnyEvent->timer (after => 1, cb => $cb); 240 my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
241 warn "timeout\n";
207 }; 242 };
208
209 # start the "loop" by creating the first watcher
210 $w = AnyEvent->timer (after => 0.5, cb => $cb);
211 243
212=head3 TIMING ISSUES 244=head3 TIMING ISSUES
213 245
214There are two ways to handle timers: based on real time (relative, "fire 246There are two ways to handle timers: based on real time (relative, "fire
215in 10 seconds") and based on wallclock time (absolute, "fire at 12 247in 10 seconds") and based on wallclock time (absolute, "fire at 12
227timers. 259timers.
228 260
229AnyEvent always prefers relative timers, if available, matching the 261AnyEvent always prefers relative timers, if available, matching the
230AnyEvent API. 262AnyEvent API.
231 263
264AnyEvent has two additional methods that return the "current time":
265
266=over 4
267
268=item AnyEvent->time
269
270This returns the "current wallclock time" as a fractional number of
271seconds since the Epoch (the same thing as C<time> or C<Time::HiRes::time>
272return, and the result is guaranteed to be compatible with those).
273
274It progresses independently of any event loop processing, i.e. each call
275will check the system clock, which usually gets updated frequently.
276
277=item AnyEvent->now
278
279This also returns the "current wallclock time", but unlike C<time>, above,
280this value might change only once per event loop iteration, depending on
281the event loop (most return the same time as C<time>, above). This is the
282time that AnyEvent's timers get scheduled against.
283
284I<In almost all cases (in all cases if you don't care), this is the
285function to call when you want to know the current time.>
286
287This function is also often faster then C<< AnyEvent->time >>, and
288thus the preferred method if you want some timestamp (for example,
289L<AnyEvent::Handle> uses this to update it's activity timeouts).
290
291The rest of this section is only of relevance if you try to be very exact
292with your timing, you can skip it without bad conscience.
293
294For a practical example of when these times differ, consider L<Event::Lib>
295and L<EV> and the following set-up:
296
297The event loop is running and has just invoked one of your callback at
298time=500 (assume no other callbacks delay processing). In your callback,
299you wait a second by executing C<sleep 1> (blocking the process for a
300second) and then (at time=501) you create a relative timer that fires
301after three seconds.
302
303With L<Event::Lib>, C<< AnyEvent->time >> and C<< AnyEvent->now >> will
304both return C<501>, because that is the current time, and the timer will
305be scheduled to fire at time=504 (C<501> + C<3>).
306
307With L<EV>, C<< AnyEvent->time >> returns C<501> (as that is the current
308time), but C<< AnyEvent->now >> returns C<500>, as that is the time the
309last event processing phase started. With L<EV>, your timer gets scheduled
310to run at time=503 (C<500> + C<3>).
311
312In one sense, L<Event::Lib> is more exact, as it uses the current time
313regardless of any delays introduced by event processing. However, most
314callbacks do not expect large delays in processing, so this causes a
315higher drift (and a lot more system calls to get the current time).
316
317In another sense, L<EV> is more exact, as your timer will be scheduled at
318the same time, regardless of how long event processing actually took.
319
320In either case, if you care (and in most cases, you don't), then you
321can get whatever behaviour you want with any event loop, by taking the
322difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
323account.
324
325=item AnyEvent->now_update
326
327Some event loops (such as L<EV> or L<AnyEvent::Impl::Perl>) cache
328the current time for each loop iteration (see the discussion of L<<
329AnyEvent->now >>, above).
330
331When a callback runs for a long time (or when the process sleeps), then
332this "current" time will differ substantially from the real time, which
333might affect timers and time-outs.
334
335When this is the case, you can call this method, which will update the
336event loop's idea of "current time".
337
338Note that updating the time I<might> cause some events to be handled.
339
340=back
341
232=head2 SIGNAL WATCHERS 342=head2 SIGNAL WATCHERS
233 343
234You can watch for signals using a signal watcher, C<signal> is the signal 344You can watch for signals using a signal watcher, C<signal> is the signal
235I<name> without any C<SIG> prefix, C<cb> is the Perl callback to 345I<name> in uppercase and without any C<SIG> prefix, C<cb> is the Perl
236be invoked whenever a signal occurs. 346callback to be invoked whenever a signal occurs.
237 347
238Although the callback might get passed parameters, their value and 348Although the callback might get passed parameters, their value and
239presence is undefined and you cannot rely on them. Portable AnyEvent 349presence is undefined and you cannot rely on them. Portable AnyEvent
240callbacks cannot use arguments passed to signal watcher callbacks. 350callbacks cannot use arguments passed to signal watcher callbacks.
241 351
242Multiple signal occurances can be clumped together into one callback 352Multiple signal occurrences can be clumped together into one callback
243invocation, and callback invocation will be synchronous. synchronous means 353invocation, and callback invocation will be synchronous. Synchronous means
244that it might take a while until the signal gets handled by the process, 354that it might take a while until the signal gets handled by the process,
245but it is guarenteed not to interrupt any other callbacks. 355but it is guaranteed not to interrupt any other callbacks.
246 356
247The main advantage of using these watchers is that you can share a signal 357The main advantage of using these watchers is that you can share a signal
248between multiple watchers. 358between multiple watchers.
249 359
250This watcher might use C<%SIG>, so programs overwriting those signals 360This watcher might use C<%SIG>, so programs overwriting those signals
257=head2 CHILD PROCESS WATCHERS 367=head2 CHILD PROCESS WATCHERS
258 368
259You can also watch on a child process exit and catch its exit status. 369You can also watch on a child process exit and catch its exit status.
260 370
261The child process is specified by the C<pid> argument (if set to C<0>, it 371The child process is specified by the C<pid> argument (if set to C<0>, it
262watches for any child process exit). The watcher will trigger as often 372watches for any child process exit). The watcher will triggered only when
263as status change for the child are received. This works by installing a 373the child process has finished and an exit status is available, not on
264signal handler for C<SIGCHLD>. The callback will be called with the pid 374any trace events (stopped/continued).
265and exit status (as returned by waitpid), so unlike other watcher types, 375
266you I<can> rely on child watcher callback arguments. 376The callback will be called with the pid and exit status (as returned by
377waitpid), so unlike other watcher types, you I<can> rely on child watcher
378callback arguments.
379
380This watcher type works by installing a signal handler for C<SIGCHLD>,
381and since it cannot be shared, nothing else should use SIGCHLD or reap
382random child processes (waiting for specific child processes, e.g. inside
383C<system>, is just fine).
267 384
268There is a slight catch to child watchers, however: you usually start them 385There is a slight catch to child watchers, however: you usually start them
269I<after> the child process was created, and this means the process could 386I<after> the child process was created, and this means the process could
270have exited already (and no SIGCHLD will be sent anymore). 387have exited already (and no SIGCHLD will be sent anymore).
271 388
277AnyEvent program, you I<have> to create at least one watcher before you 394AnyEvent program, you I<have> to create at least one watcher before you
278C<fork> the child (alternatively, you can call C<AnyEvent::detect>). 395C<fork> the child (alternatively, you can call C<AnyEvent::detect>).
279 396
280Example: fork a process and wait for it 397Example: fork a process and wait for it
281 398
282 my $done = AnyEvent->condvar; 399 my $done = AnyEvent->condvar;
283 400
284 my $pid = fork or exit 5; 401 my $pid = fork or exit 5;
285 402
286 my $w = AnyEvent->child ( 403 my $w = AnyEvent->child (
287 pid => $pid, 404 pid => $pid,
288 cb => sub { 405 cb => sub {
289 my ($pid, $status) = @_; 406 my ($pid, $status) = @_;
290 warn "pid $pid exited with status $status"; 407 warn "pid $pid exited with status $status";
291 $done->send; 408 $done->send;
292 }, 409 },
293 ); 410 );
294 411
295 # do something else, then wait for process exit 412 # do something else, then wait for process exit
296 $done->recv; 413 $done->recv;
297 414
298=head2 CONDITION VARIABLES 415=head2 CONDITION VARIABLES
299 416
300If you are familiar with some event loops you will know that all of them 417If you are familiar with some event loops you will know that all of them
301require you to run some blocking "loop", "run" or similar function that 418require you to run some blocking "loop", "run" or similar function that
307The instrument to do that is called a "condition variable", so called 424The instrument to do that is called a "condition variable", so called
308because they represent a condition that must become true. 425because they represent a condition that must become true.
309 426
310Condition variables can be created by calling the C<< AnyEvent->condvar 427Condition variables can be created by calling the C<< AnyEvent->condvar
311>> method, usually without arguments. The only argument pair allowed is 428>> method, usually without arguments. The only argument pair allowed is
429
312C<cb>, which specifies a callback to be called when the condition variable 430C<cb>, which specifies a callback to be called when the condition variable
313becomes true. 431becomes true, with the condition variable as the first argument (but not
432the results).
314 433
315After creation, the conditon variable is "false" until it becomes "true" 434After creation, the condition variable is "false" until it becomes "true"
316by calling the C<send> method. 435by calling the C<send> method (or calling the condition variable as if it
436were a callback, read about the caveats in the description for the C<<
437->send >> method).
317 438
318Condition variables are similar to callbacks, except that you can 439Condition variables are similar to callbacks, except that you can
319optionally wait for them. They can also be called merge points - points 440optionally wait for them. They can also be called merge points - points
320in time where multiple outstandign events have been processed. And yet 441in time where multiple outstanding events have been processed. And yet
321another way to call them is transations - each condition variable can be 442another way to call them is transactions - each condition variable can be
322used to represent a transaction, which finishes at some point and delivers 443used to represent a transaction, which finishes at some point and delivers
323a result. 444a result.
324 445
325Condition variables are very useful to signal that something has finished, 446Condition variables are very useful to signal that something has finished,
326for example, if you write a module that does asynchronous http requests, 447for example, if you write a module that does asynchronous http requests,
332you can block your main program until an event occurs - for example, you 453you can block your main program until an event occurs - for example, you
333could C<< ->recv >> in your main program until the user clicks the Quit 454could C<< ->recv >> in your main program until the user clicks the Quit
334button of your app, which would C<< ->send >> the "quit" event. 455button of your app, which would C<< ->send >> the "quit" event.
335 456
336Note that condition variables recurse into the event loop - if you have 457Note that condition variables recurse into the event loop - if you have
337two pieces of code that call C<< ->recv >> in a round-robbin fashion, you 458two pieces of code that call C<< ->recv >> in a round-robin fashion, you
338lose. Therefore, condition variables are good to export to your caller, but 459lose. Therefore, condition variables are good to export to your caller, but
339you should avoid making a blocking wait yourself, at least in callbacks, 460you should avoid making a blocking wait yourself, at least in callbacks,
340as this asks for trouble. 461as this asks for trouble.
341 462
342Condition variables are represented by hash refs in perl, and the keys 463Condition variables are represented by hash refs in perl, and the keys
347 468
348There are two "sides" to a condition variable - the "producer side" which 469There are two "sides" to a condition variable - the "producer side" which
349eventually calls C<< -> send >>, and the "consumer side", which waits 470eventually calls C<< -> send >>, and the "consumer side", which waits
350for the send to occur. 471for the send to occur.
351 472
352Example: 473Example: wait for a timer.
353 474
354 # wait till the result is ready 475 # wait till the result is ready
355 my $result_ready = AnyEvent->condvar; 476 my $result_ready = AnyEvent->condvar;
356 477
357 # do something such as adding a timer 478 # do something such as adding a timer
365 486
366 # this "blocks" (while handling events) till the callback 487 # this "blocks" (while handling events) till the callback
367 # calls send 488 # calls send
368 $result_ready->recv; 489 $result_ready->recv;
369 490
491Example: wait for a timer, but take advantage of the fact that
492condition variables are also code references.
493
494 my $done = AnyEvent->condvar;
495 my $delay = AnyEvent->timer (after => 5, cb => $done);
496 $done->recv;
497
498Example: Imagine an API that returns a condvar and doesn't support
499callbacks. This is how you make a synchronous call, for example from
500the main program:
501
502 use AnyEvent::CouchDB;
503
504 ...
505
506 my @info = $couchdb->info->recv;
507
508And this is how you would just ste a callback to be called whenever the
509results are available:
510
511 $couchdb->info->cb (sub {
512 my @info = $_[0]->recv;
513 });
514
370=head3 METHODS FOR PRODUCERS 515=head3 METHODS FOR PRODUCERS
371 516
372These methods should only be used by the producing side, i.e. the 517These methods should only be used by the producing side, i.e. the
373code/module that eventually sends the signal. Note that it is also 518code/module that eventually sends the signal. Note that it is also
374the producer side which creates the condvar in most cases, but it isn't 519the producer side which creates the condvar in most cases, but it isn't
385If a callback has been set on the condition variable, it is called 530If a callback has been set on the condition variable, it is called
386immediately from within send. 531immediately from within send.
387 532
388Any arguments passed to the C<send> call will be returned by all 533Any arguments passed to the C<send> call will be returned by all
389future C<< ->recv >> calls. 534future C<< ->recv >> calls.
535
536Condition variables are overloaded so one can call them directly
537(as a code reference). Calling them directly is the same as calling
538C<send>. Note, however, that many C-based event loops do not handle
539overloading, so as tempting as it may be, passing a condition variable
540instead of a callback does not work. Both the pure perl and EV loops
541support overloading, however, as well as all functions that use perl to
542invoke a callback (as in L<AnyEvent::Socket> and L<AnyEvent::DNS> for
543example).
390 544
391=item $cv->croak ($error) 545=item $cv->croak ($error)
392 546
393Similar to send, but causes all call's to C<< ->recv >> to invoke 547Similar to send, but causes all call's to C<< ->recv >> to invoke
394C<Carp::croak> with the given error message/object/scalar. 548C<Carp::croak> with the given error message/object/scalar.
443doesn't execute once). 597doesn't execute once).
444 598
445This is the general pattern when you "fan out" into multiple subrequests: 599This is the general pattern when you "fan out" into multiple subrequests:
446use an outer C<begin>/C<end> pair to set the callback and ensure C<end> 600use an outer C<begin>/C<end> pair to set the callback and ensure C<end>
447is called at least once, and then, for each subrequest you start, call 601is called at least once, and then, for each subrequest you start, call
448C<begin> and for eahc subrequest you finish, call C<end>. 602C<begin> and for each subrequest you finish, call C<end>.
449 603
450=back 604=back
451 605
452=head3 METHODS FOR CONSUMERS 606=head3 METHODS FOR CONSUMERS
453 607
475(programs might want to do that to stay interactive), so I<if you are 629(programs might want to do that to stay interactive), so I<if you are
476using this from a module, never require a blocking wait>, but let the 630using this from a module, never require a blocking wait>, but let the
477caller decide whether the call will block or not (for example, by coupling 631caller decide whether the call will block or not (for example, by coupling
478condition variables with some kind of request results and supporting 632condition variables with some kind of request results and supporting
479callbacks so the caller knows that getting the result will not block, 633callbacks so the caller knows that getting the result will not block,
480while still suppporting blocking waits if the caller so desires). 634while still supporting blocking waits if the caller so desires).
481 635
482Another reason I<never> to C<< ->recv >> in a module is that you cannot 636Another reason I<never> to C<< ->recv >> in a module is that you cannot
483sensibly have two C<< ->recv >>'s in parallel, as that would require 637sensibly have two C<< ->recv >>'s in parallel, as that would require
484multiple interpreters or coroutines/threads, none of which C<AnyEvent> 638multiple interpreters or coroutines/threads, none of which C<AnyEvent>
485can supply. 639can supply.
498=item $bool = $cv->ready 652=item $bool = $cv->ready
499 653
500Returns true when the condition is "true", i.e. whether C<send> or 654Returns true when the condition is "true", i.e. whether C<send> or
501C<croak> have been called. 655C<croak> have been called.
502 656
503=item $cb = $cv->cb ([new callback]) 657=item $cb = $cv->cb ($cb->($cv))
504 658
505This is a mutator function that returns the callback set and optionally 659This is a mutator function that returns the callback set and optionally
506replaces it before doing so. 660replaces it before doing so.
507 661
508The callback will be called when the condition becomes "true", i.e. when 662The callback will be called when the condition becomes "true", i.e. when
509C<send> or C<croak> are called. Calling C<recv> inside the callback 663C<send> or C<croak> are called, with the only argument being the condition
510or at any later time is guaranteed not to block. 664variable itself. Calling C<recv> inside the callback or at any later time
665is guaranteed not to block.
511 666
512=back 667=back
513 668
514=head1 GLOBAL VARIABLES AND FUNCTIONS 669=head1 GLOBAL VARIABLES AND FUNCTIONS
515 670
601 756
602If it doesn't care, it can just "use AnyEvent" and use it itself, or not 757If it doesn't care, it can just "use AnyEvent" and use it itself, or not
603do anything special (it does not need to be event-based) and let AnyEvent 758do anything special (it does not need to be event-based) and let AnyEvent
604decide which implementation to chose if some module relies on it. 759decide which implementation to chose if some module relies on it.
605 760
606If the main program relies on a specific event model. For example, in 761If the main program relies on a specific event model - for example, in
607Gtk2 programs you have to rely on the Glib module. You should load the 762Gtk2 programs you have to rely on the Glib module - you should load the
608event module before loading AnyEvent or any module that uses it: generally 763event module before loading AnyEvent or any module that uses it: generally
609speaking, you should load it as early as possible. The reason is that 764speaking, you should load it as early as possible. The reason is that
610modules might create watchers when they are loaded, and AnyEvent will 765modules might create watchers when they are loaded, and AnyEvent will
611decide on the event model to use as soon as it creates watchers, and it 766decide on the event model to use as soon as it creates watchers, and it
612might chose the wrong one unless you load the correct one yourself. 767might chose the wrong one unless you load the correct one yourself.
613 768
614You can chose to use a rather inefficient pure-perl implementation by 769You can chose to use a pure-perl implementation by loading the
615loading the C<AnyEvent::Impl::Perl> module, which gives you similar 770C<AnyEvent::Impl::Perl> module, which gives you similar behaviour
616behaviour everywhere, but letting AnyEvent chose is generally better. 771everywhere, but letting AnyEvent chose the model is generally better.
772
773=head2 MAINLOOP EMULATION
774
775Sometimes (often for short test scripts, or even standalone programs who
776only want to use AnyEvent), you do not want to run a specific event loop.
777
778In that case, you can use a condition variable like this:
779
780 AnyEvent->condvar->recv;
781
782This has the effect of entering the event loop and looping forever.
783
784Note that usually your program has some exit condition, in which case
785it is better to use the "traditional" approach of storing a condition
786variable somewhere, waiting for it, and sending it when the program should
787exit cleanly.
788
617 789
618=head1 OTHER MODULES 790=head1 OTHER MODULES
619 791
620The following is a non-exhaustive list of additional modules that use 792The following is a non-exhaustive list of additional modules that use
621AnyEvent and can therefore be mixed easily with other AnyEvent modules 793AnyEvent and can therefore be mixed easily with other AnyEvent modules
627=item L<AnyEvent::Util> 799=item L<AnyEvent::Util>
628 800
629Contains various utility functions that replace often-used but blocking 801Contains various utility functions that replace often-used but blocking
630functions such as C<inet_aton> by event-/callback-based versions. 802functions such as C<inet_aton> by event-/callback-based versions.
631 803
632=item L<AnyEvent::Handle>
633
634Provide read and write buffers and manages watchers for reads and writes.
635
636=item L<AnyEvent::Socket> 804=item L<AnyEvent::Socket>
637 805
638Provides various utility functions for (internet protocol) sockets, 806Provides various utility functions for (internet protocol) sockets,
639addresses and name resolution. Also functions to create non-blocking tcp 807addresses and name resolution. Also functions to create non-blocking tcp
640connections or tcp servers, with IPv6 and SRV record support and more. 808connections or tcp servers, with IPv6 and SRV record support and more.
641 809
810=item L<AnyEvent::Handle>
811
812Provide read and write buffers, manages watchers for reads and writes,
813supports raw and formatted I/O, I/O queued and fully transparent and
814non-blocking SSL/TLS.
815
816=item L<AnyEvent::DNS>
817
818Provides rich asynchronous DNS resolver capabilities.
819
820=item L<AnyEvent::HTTP>
821
822A simple-to-use HTTP library that is capable of making a lot of concurrent
823HTTP requests.
824
642=item L<AnyEvent::HTTPD> 825=item L<AnyEvent::HTTPD>
643 826
644Provides a simple web application server framework. 827Provides a simple web application server framework.
645 828
646=item L<AnyEvent::DNS>
647
648Provides rich asynchronous DNS resolver capabilities.
649
650=item L<AnyEvent::FastPing> 829=item L<AnyEvent::FastPing>
651 830
652The fastest ping in the west. 831The fastest ping in the west.
653 832
833=item L<AnyEvent::DBI>
834
835Executes L<DBI> requests asynchronously in a proxy process.
836
837=item L<AnyEvent::AIO>
838
839Truly asynchronous I/O, should be in the toolbox of every event
840programmer. AnyEvent::AIO transparently fuses L<IO::AIO> and AnyEvent
841together.
842
843=item L<AnyEvent::BDB>
844
845Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently fuses
846L<BDB> and AnyEvent together.
847
848=item L<AnyEvent::GPSD>
849
850A non-blocking interface to gpsd, a daemon delivering GPS information.
851
852=item L<AnyEvent::IGS>
853
854A non-blocking interface to the Internet Go Server protocol (used by
855L<App::IGS>).
856
654=item L<Net::IRC3> 857=item L<AnyEvent::IRC>
655 858
656AnyEvent based IRC client module family. 859AnyEvent based IRC client module family (replacing the older Net::IRC3).
657 860
658=item L<Net::XMPP2> 861=item L<Net::XMPP2>
659 862
660AnyEvent based XMPP (Jabber protocol) module family. 863AnyEvent based XMPP (Jabber protocol) module family.
661 864
670 873
671=item L<Coro> 874=item L<Coro>
672 875
673Has special support for AnyEvent via L<Coro::AnyEvent>. 876Has special support for AnyEvent via L<Coro::AnyEvent>.
674 877
675=item L<AnyEvent::AIO>, L<IO::AIO>
676
677Truly asynchronous I/O, should be in the toolbox of every event
678programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent
679together.
680
681=item L<AnyEvent::BDB>, L<BDB>
682
683Truly asynchronous Berkeley DB access. AnyEvent::AIO transparently fuses
684IO::AIO and AnyEvent together.
685
686=item L<IO::Lambda> 878=item L<IO::Lambda>
687 879
688The lambda approach to I/O - don't ask, look there. Can use AnyEvent. 880The lambda approach to I/O - don't ask, look there. Can use AnyEvent.
689 881
690=back 882=back
692=cut 884=cut
693 885
694package AnyEvent; 886package AnyEvent;
695 887
696no warnings; 888no warnings;
697use strict; 889use strict qw(vars subs);
698 890
699use Carp; 891use Carp;
700 892
701our $VERSION = '3.6'; 893our $VERSION = 4.351;
702our $MODEL; 894our $MODEL;
703 895
704our $AUTOLOAD; 896our $AUTOLOAD;
705our @ISA; 897our @ISA;
706 898
899our @REGISTRY;
900
901our $WIN32;
902
903BEGIN {
904 my $win32 = ! ! ($^O =~ /mswin32/i);
905 eval "sub WIN32(){ $win32 }";
906}
907
707our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1; 908our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
708 909
709our @REGISTRY; 910our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
710
711our %PROTOCOL; # (ipv4|ipv6) => (1|2)
712 911
713{ 912{
714 my $idx; 913 my $idx;
715 $PROTOCOL{$_} = ++$idx 914 $PROTOCOL{$_} = ++$idx
915 for reverse split /\s*,\s*/,
716 for split /\s*,\s*/, $ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6"; 916 $ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
717} 917}
718 918
719my @models = ( 919my @models = (
720 [EV:: => AnyEvent::Impl::EV::], 920 [EV:: => AnyEvent::Impl::EV::],
721 [Event:: => AnyEvent::Impl::Event::], 921 [Event:: => AnyEvent::Impl::Event::],
722 [Tk:: => AnyEvent::Impl::Tk::],
723 [Wx:: => AnyEvent::Impl::POE::],
724 [Prima:: => AnyEvent::Impl::POE::],
725 [AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::], 922 [AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
726 # everything below here will not be autoprobed as the pureperl backend should work everywhere 923 # everything below here will not be autoprobed
727 [Glib:: => AnyEvent::Impl::Glib::], 924 # as the pureperl backend should work everywhere
925 # and is usually faster
926 [Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
927 [Glib:: => AnyEvent::Impl::Glib::], # becomes extremely slow with many watchers
728 [Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy 928 [Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
729 [Qt:: => AnyEvent::Impl::Qt::], # requires special main program 929 [Qt:: => AnyEvent::Impl::Qt::], # requires special main program
730 [POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza 930 [POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
931 [Wx:: => AnyEvent::Impl::POE::],
932 [Prima:: => AnyEvent::Impl::POE::],
731); 933);
732 934
733our %method = map +($_ => 1), qw(io timer signal child condvar one_event DESTROY); 935our %method = map +($_ => 1),
936 qw(io timer time now now_update signal child condvar one_event DESTROY);
734 937
735our @post_detect; 938our @post_detect;
736 939
737sub post_detect(&) { 940sub post_detect(&) {
738 my ($cb) = @_; 941 my ($cb) = @_;
755} 958}
756 959
757sub detect() { 960sub detect() {
758 unless ($MODEL) { 961 unless ($MODEL) {
759 no strict 'refs'; 962 no strict 'refs';
963 local $SIG{__DIE__};
760 964
761 if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) { 965 if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
762 my $model = "AnyEvent::Impl::$1"; 966 my $model = "AnyEvent::Impl::$1";
763 if (eval "require $model") { 967 if (eval "require $model") {
764 $MODEL = $model; 968 $MODEL = $model;
794 last; 998 last;
795 } 999 }
796 } 1000 }
797 1001
798 $MODEL 1002 $MODEL
799 or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib."; 1003 or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.\n";
800 } 1004 }
801 } 1005 }
802 1006
1007 push @{"$MODEL\::ISA"}, "AnyEvent::Base";
1008
803 unshift @ISA, $MODEL; 1009 unshift @ISA, $MODEL;
804 push @{"$MODEL\::ISA"}, "AnyEvent::Base"; 1010
1011 require AnyEvent::Strict if $ENV{PERL_ANYEVENT_STRICT};
805 1012
806 (shift @post_detect)->() while @post_detect; 1013 (shift @post_detect)->() while @post_detect;
807 } 1014 }
808 1015
809 $MODEL 1016 $MODEL
819 1026
820 my $class = shift; 1027 my $class = shift;
821 $class->$func (@_); 1028 $class->$func (@_);
822} 1029}
823 1030
1031# utility function to dup a filehandle. this is used by many backends
1032# to support binding more than one watcher per filehandle (they usually
1033# allow only one watcher per fd, so we dup it to get a different one).
1034sub _dupfh($$$$) {
1035 my ($poll, $fh, $r, $w) = @_;
1036
1037 # cygwin requires the fh mode to be matching, unix doesn't
1038 my ($rw, $mode) = $poll eq "r" ? ($r, "<")
1039 : $poll eq "w" ? ($w, ">")
1040 : Carp::croak "AnyEvent->io requires poll set to either 'r' or 'w'";
1041
1042 open my $fh2, "$mode&" . fileno $fh
1043 or die "cannot dup() filehandle: $!,";
1044
1045 # we assume CLOEXEC is already set by perl in all important cases
1046
1047 ($fh2, $rw)
1048}
1049
824package AnyEvent::Base; 1050package AnyEvent::Base;
1051
1052# default implementations for many methods
1053
1054BEGIN {
1055 if (eval "use Time::HiRes (); time (); 1") {
1056 *_time = \&Time::HiRes::time;
1057 # if (eval "use POSIX (); (POSIX::times())...
1058 } else {
1059 *_time = sub { time }; # epic fail
1060 }
1061}
1062
1063sub time { _time }
1064sub now { _time }
1065sub now_update { }
825 1066
826# default implementation for ->condvar 1067# default implementation for ->condvar
827 1068
828sub condvar { 1069sub condvar {
829 bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, AnyEvent::CondVar:: 1070 bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, AnyEvent::CondVar::
830} 1071}
831 1072
832# default implementation for ->signal 1073# default implementation for ->signal
833 1074
834our %SIG_CB; 1075our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
1076
1077sub _signal_exec {
1078 sysread $SIGPIPE_R, my $dummy, 4;
1079
1080 while (%SIG_EV) {
1081 for (keys %SIG_EV) {
1082 delete $SIG_EV{$_};
1083 $_->() for values %{ $SIG_CB{$_} || {} };
1084 }
1085 }
1086}
835 1087
836sub signal { 1088sub signal {
837 my (undef, %arg) = @_; 1089 my (undef, %arg) = @_;
838 1090
1091 unless ($SIGPIPE_R) {
1092 require Fcntl;
1093
1094 if (AnyEvent::WIN32) {
1095 require AnyEvent::Util;
1096
1097 ($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
1098 AnyEvent::Util::fh_nonblocking ($SIGPIPE_R) if $SIGPIPE_R;
1099 AnyEvent::Util::fh_nonblocking ($SIGPIPE_W) if $SIGPIPE_W; # just in case
1100 } else {
1101 pipe $SIGPIPE_R, $SIGPIPE_W;
1102 fcntl $SIGPIPE_R, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_R;
1103 fcntl $SIGPIPE_W, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_W; # just in case
1104 }
1105
1106 $SIGPIPE_R
1107 or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
1108
1109 # not strictly required, as $^F is normally 2, but let's make sure...
1110 fcntl $SIGPIPE_R, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
1111 fcntl $SIGPIPE_W, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
1112
1113 $SIG_IO = AnyEvent->io (fh => $SIGPIPE_R, poll => "r", cb => \&_signal_exec);
1114 }
1115
839 my $signal = uc $arg{signal} 1116 my $signal = uc $arg{signal}
840 or Carp::croak "required option 'signal' is missing"; 1117 or Carp::croak "required option 'signal' is missing";
841 1118
842 $SIG_CB{$signal}{$arg{cb}} = $arg{cb}; 1119 $SIG_CB{$signal}{$arg{cb}} = $arg{cb};
843 $SIG{$signal} ||= sub { 1120 $SIG{$signal} ||= sub {
844 $_->() for values %{ $SIG_CB{$signal} || {} }; 1121 local $!;
1122 syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
1123 undef $SIG_EV{$signal};
845 }; 1124 };
846 1125
847 bless [$signal, $arg{cb}], "AnyEvent::Base::Signal" 1126 bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"
848} 1127}
849 1128
850sub AnyEvent::Base::Signal::DESTROY { 1129sub AnyEvent::Base::Signal::DESTROY {
851 my ($signal, $cb) = @{$_[0]}; 1130 my ($signal, $cb) = @{$_[0]};
852 1131
853 delete $SIG_CB{$signal}{$cb}; 1132 delete $SIG_CB{$signal}{$cb};
854 1133
855 $SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} }; 1134 delete $SIG{$signal} unless keys %{ $SIG_CB{$signal} };
856} 1135}
857 1136
858# default implementation for ->child 1137# default implementation for ->child
859 1138
860our %PID_CB; 1139our %PID_CB;
887 or Carp::croak "required option 'pid' is missing"; 1166 or Carp::croak "required option 'pid' is missing";
888 1167
889 $PID_CB{$pid}{$arg{cb}} = $arg{cb}; 1168 $PID_CB{$pid}{$arg{cb}} = $arg{cb};
890 1169
891 unless ($WNOHANG) { 1170 unless ($WNOHANG) {
892 $WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1; 1171 $WNOHANG = eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
893 } 1172 }
894 1173
895 unless ($CHLD_W) { 1174 unless ($CHLD_W) {
896 $CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld); 1175 $CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
897 # child could be a zombie already, so make at least one round 1176 # child could be a zombie already, so make at least one round
914 1193
915our @ISA = AnyEvent::CondVar::Base::; 1194our @ISA = AnyEvent::CondVar::Base::;
916 1195
917package AnyEvent::CondVar::Base; 1196package AnyEvent::CondVar::Base;
918 1197
1198use overload
1199 '&{}' => sub { my $self = shift; sub { $self->send (@_) } },
1200 fallback => 1;
1201
919sub _send { 1202sub _send {
920 # nop 1203 # nop
921} 1204}
922 1205
923sub send { 1206sub send {
963} 1246}
964 1247
965# undocumented/compatibility with pre-3.4 1248# undocumented/compatibility with pre-3.4
966*broadcast = \&send; 1249*broadcast = \&send;
967*wait = \&_wait; 1250*wait = \&_wait;
1251
1252=head1 ERROR AND EXCEPTION HANDLING
1253
1254In general, AnyEvent does not do any error handling - it relies on the
1255caller to do that if required. The L<AnyEvent::Strict> module (see also
1256the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
1257checking of all AnyEvent methods, however, which is highly useful during
1258development.
1259
1260As for exception handling (i.e. runtime errors and exceptions thrown while
1261executing a callback), this is not only highly event-loop specific, but
1262also not in any way wrapped by this module, as this is the job of the main
1263program.
1264
1265The pure perl event loop simply re-throws the exception (usually
1266within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
1267$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
1268so on.
1269
1270=head1 ENVIRONMENT VARIABLES
1271
1272The following environment variables are used by this module or its
1273submodules:
1274
1275=over 4
1276
1277=item C<PERL_ANYEVENT_VERBOSE>
1278
1279By default, AnyEvent will be completely silent except in fatal
1280conditions. You can set this environment variable to make AnyEvent more
1281talkative.
1282
1283When set to C<1> or higher, causes AnyEvent to warn about unexpected
1284conditions, such as not being able to load the event model specified by
1285C<PERL_ANYEVENT_MODEL>.
1286
1287When set to C<2> or higher, cause AnyEvent to report to STDERR which event
1288model it chooses.
1289
1290=item C<PERL_ANYEVENT_STRICT>
1291
1292AnyEvent does not do much argument checking by default, as thorough
1293argument checking is very costly. Setting this variable to a true value
1294will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
1295check the arguments passed to most method calls. If it finds any problems
1296it will croak.
1297
1298In other words, enables "strict" mode.
1299
1300Unlike C<use strict>, it is definitely recommended ot keep it off in
1301production. Keeping C<PERL_ANYEVENT_STRICT=1> in your environment while
1302developing programs can be very useful, however.
1303
1304=item C<PERL_ANYEVENT_MODEL>
1305
1306This can be used to specify the event model to be used by AnyEvent, before
1307auto detection and -probing kicks in. It must be a string consisting
1308entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
1309and the resulting module name is loaded and if the load was successful,
1310used as event model. If it fails to load AnyEvent will proceed with
1311auto detection and -probing.
1312
1313This functionality might change in future versions.
1314
1315For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
1316could start your program like this:
1317
1318 PERL_ANYEVENT_MODEL=Perl perl ...
1319
1320=item C<PERL_ANYEVENT_PROTOCOLS>
1321
1322Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
1323for IPv4 or IPv6. The default is unspecified (and might change, or be the result
1324of auto probing).
1325
1326Must be set to a comma-separated list of protocols or address families,
1327current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
1328used, and preference will be given to protocols mentioned earlier in the
1329list.
1330
1331This variable can effectively be used for denial-of-service attacks
1332against local programs (e.g. when setuid), although the impact is likely
1333small, as the program has to handle conenction and other failures anyways.
1334
1335Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
1336but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
1337- only support IPv4, never try to resolve or contact IPv6
1338addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
1339IPv6, but prefer IPv6 over IPv4.
1340
1341=item C<PERL_ANYEVENT_EDNS0>
1342
1343Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
1344for DNS. This extension is generally useful to reduce DNS traffic, but
1345some (broken) firewalls drop such DNS packets, which is why it is off by
1346default.
1347
1348Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
1349EDNS0 in its DNS requests.
1350
1351=item C<PERL_ANYEVENT_MAX_FORKS>
1352
1353The maximum number of child processes that C<AnyEvent::Util::fork_call>
1354will create in parallel.
1355
1356=back
968 1357
969=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE 1358=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
970 1359
971This is an advanced topic that you do not normally need to use AnyEvent in 1360This is an advanced topic that you do not normally need to use AnyEvent in
972a module. This section is only of use to event loop authors who want to 1361a module. This section is only of use to event loop authors who want to
1006 1395
1007I<rxvt-unicode> also cheats a bit by not providing blocking access to 1396I<rxvt-unicode> also cheats a bit by not providing blocking access to
1008condition variables: code blocking while waiting for a condition will 1397condition variables: code blocking while waiting for a condition will
1009C<die>. This still works with most modules/usages, and blocking calls must 1398C<die>. This still works with most modules/usages, and blocking calls must
1010not be done in an interactive application, so it makes sense. 1399not be done in an interactive application, so it makes sense.
1011
1012=head1 ENVIRONMENT VARIABLES
1013
1014The following environment variables are used by this module:
1015
1016=over 4
1017
1018=item C<PERL_ANYEVENT_VERBOSE>
1019
1020By default, AnyEvent will be completely silent except in fatal
1021conditions. You can set this environment variable to make AnyEvent more
1022talkative.
1023
1024When set to C<1> or higher, causes AnyEvent to warn about unexpected
1025conditions, such as not being able to load the event model specified by
1026C<PERL_ANYEVENT_MODEL>.
1027
1028When set to C<2> or higher, cause AnyEvent to report to STDERR which event
1029model it chooses.
1030
1031=item C<PERL_ANYEVENT_MODEL>
1032
1033This can be used to specify the event model to be used by AnyEvent, before
1034autodetection and -probing kicks in. It must be a string consisting
1035entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
1036and the resulting module name is loaded and if the load was successful,
1037used as event model. If it fails to load AnyEvent will proceed with
1038autodetection and -probing.
1039
1040This functionality might change in future versions.
1041
1042For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
1043could start your program like this:
1044
1045 PERL_ANYEVENT_MODEL=Perl perl ...
1046
1047=item C<PERL_ANYEVENT_PROTOCOLS>
1048
1049Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
1050for IPv4 or IPv6. The default is unspecified (and might change, or be the result
1051of autoprobing).
1052
1053Must be set to a comma-separated list of protocols or address families,
1054current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
1055used, and preference will be given to protocols mentioned earlier in the
1056list.
1057
1058This variable can effectively be used for denial-of-service attacks
1059against local programs (e.g. when setuid), although the impact is likely
1060small, as the program has to handle connection errors already-
1061
1062Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
1063but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
1064- only support IPv4, never try to resolve or contact IPv6
1065addressses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
1066IPv6, but prefer IPv6 over IPv4.
1067
1068=item C<PERL_ANYEVENT_EDNS0>
1069
1070Used by L<AnyEvent::DNS> to decide wether to use the EDNS0 extension
1071for DNS. This extension is generally useful to reduce DNS traffic, but
1072some (broken) firewalls drop such DNS packets, which is why it is off by
1073default.
1074
1075Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
1076EDNS0 in its DNS requests.
1077
1078=back
1079 1400
1080=head1 EXAMPLE PROGRAM 1401=head1 EXAMPLE PROGRAM
1081 1402
1082The following program uses an I/O watcher to read data from STDIN, a timer 1403The following program uses an I/O watcher to read data from STDIN, a timer
1083to display a message once per second, and a condition variable to quit the 1404to display a message once per second, and a condition variable to quit the
1167 syswrite $txn->{fh}, $txn->{request} 1488 syswrite $txn->{fh}, $txn->{request}
1168 or die "connection or write error"; 1489 or die "connection or write error";
1169 $txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r }); 1490 $txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
1170 1491
1171Again, C<fh_ready_r> waits till all data has arrived, and then stores the 1492Again, C<fh_ready_r> waits till all data has arrived, and then stores the
1172result and signals any possible waiters that the request ahs finished: 1493result and signals any possible waiters that the request has finished:
1173 1494
1174 sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf}; 1495 sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
1175 1496
1176 if (end-of-file or data complete) { 1497 if (end-of-file or data complete) {
1177 $txn->{result} = $txn->{buf}; 1498 $txn->{result} = $txn->{buf};
1185 1506
1186 $txn->{finished}->recv; 1507 $txn->{finished}->recv;
1187 return $txn->{result}; 1508 return $txn->{result};
1188 1509
1189The actual code goes further and collects all errors (C<die>s, exceptions) 1510The actual code goes further and collects all errors (C<die>s, exceptions)
1190that occured during request processing. The C<result> method detects 1511that occurred during request processing. The C<result> method detects
1191whether an exception as thrown (it is stored inside the $txn object) 1512whether an exception as thrown (it is stored inside the $txn object)
1192and just throws the exception, which means connection errors and other 1513and just throws the exception, which means connection errors and other
1193problems get reported tot he code that tries to use the result, not in a 1514problems get reported tot he code that tries to use the result, not in a
1194random callback. 1515random callback.
1195 1516
1241of various event loops I prepared some benchmarks. 1562of various event loops I prepared some benchmarks.
1242 1563
1243=head2 BENCHMARKING ANYEVENT OVERHEAD 1564=head2 BENCHMARKING ANYEVENT OVERHEAD
1244 1565
1245Here is a benchmark of various supported event models used natively and 1566Here is a benchmark of various supported event models used natively and
1246through anyevent. The benchmark creates a lot of timers (with a zero 1567through AnyEvent. The benchmark creates a lot of timers (with a zero
1247timeout) and I/O watchers (watching STDOUT, a pty, to become writable, 1568timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
1248which it is), lets them fire exactly once and destroys them again. 1569which it is), lets them fire exactly once and destroys them again.
1249 1570
1250Source code for this benchmark is found as F<eg/bench> in the AnyEvent 1571Source code for this benchmark is found as F<eg/bench> in the AnyEvent
1251distribution. 1572distribution.
1277watcher. 1598watcher.
1278 1599
1279=head3 Results 1600=head3 Results
1280 1601
1281 name watchers bytes create invoke destroy comment 1602 name watchers bytes create invoke destroy comment
1282 EV/EV 400000 244 0.56 0.46 0.31 EV native interface 1603 EV/EV 400000 224 0.47 0.35 0.27 EV native interface
1283 EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers 1604 EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers
1284 CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal 1605 CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal
1285 Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation 1606 Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation
1286 Event/Event 16000 516 31.88 31.30 0.85 Event native interface 1607 Event/Event 16000 517 32.20 31.80 0.81 Event native interface
1287 Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers 1608 Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers
1288 Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour 1609 Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour
1289 Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers 1610 Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers
1290 POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event 1611 POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event
1291 POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select 1612 POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select
1292 1613
1293=head3 Discussion 1614=head3 Discussion
1294 1615
1295The benchmark does I<not> measure scalability of the event loop very 1616The benchmark does I<not> measure scalability of the event loop very
1296well. For example, a select-based event loop (such as the pure perl one) 1617well. For example, a select-based event loop (such as the pure perl one)
1374 1695
1375=back 1696=back
1376 1697
1377=head2 BENCHMARKING THE LARGE SERVER CASE 1698=head2 BENCHMARKING THE LARGE SERVER CASE
1378 1699
1379This benchmark atcually benchmarks the event loop itself. It works by 1700This benchmark actually benchmarks the event loop itself. It works by
1380creating a number of "servers": each server consists of a socketpair, a 1701creating a number of "servers": each server consists of a socket pair, a
1381timeout watcher that gets reset on activity (but never fires), and an I/O 1702timeout watcher that gets reset on activity (but never fires), and an I/O
1382watcher waiting for input on one side of the socket. Each time the socket 1703watcher waiting for input on one side of the socket. Each time the socket
1383watcher reads a byte it will write that byte to a random other "server". 1704watcher reads a byte it will write that byte to a random other "server".
1384 1705
1385The effect is that there will be a lot of I/O watchers, only part of which 1706The effect is that there will be a lot of I/O watchers, only part of which
1386are active at any one point (so there is a constant number of active 1707are active at any one point (so there is a constant number of active
1387fds for each loop iterstaion, but which fds these are is random). The 1708fds for each loop iteration, but which fds these are is random). The
1388timeout is reset each time something is read because that reflects how 1709timeout is reset each time something is read because that reflects how
1389most timeouts work (and puts extra pressure on the event loops). 1710most timeouts work (and puts extra pressure on the event loops).
1390 1711
1391In this benchmark, we use 10000 socketpairs (20000 sockets), of which 100 1712In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
1392(1%) are active. This mirrors the activity of large servers with many 1713(1%) are active. This mirrors the activity of large servers with many
1393connections, most of which are idle at any one point in time. 1714connections, most of which are idle at any one point in time.
1394 1715
1395Source code for this benchmark is found as F<eg/bench2> in the AnyEvent 1716Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
1396distribution. 1717distribution.
1398=head3 Explanation of the columns 1719=head3 Explanation of the columns
1399 1720
1400I<sockets> is the number of sockets, and twice the number of "servers" (as 1721I<sockets> is the number of sockets, and twice the number of "servers" (as
1401each server has a read and write socket end). 1722each server has a read and write socket end).
1402 1723
1403I<create> is the time it takes to create a socketpair (which is 1724I<create> is the time it takes to create a socket pair (which is
1404nontrivial) and two watchers: an I/O watcher and a timeout watcher. 1725nontrivial) and two watchers: an I/O watcher and a timeout watcher.
1405 1726
1406I<request>, the most important value, is the time it takes to handle a 1727I<request>, the most important value, is the time it takes to handle a
1407single "request", that is, reading the token from the pipe and forwarding 1728single "request", that is, reading the token from the pipe and forwarding
1408it to another server. This includes deleting the old timeout and creating 1729it to another server. This includes deleting the old timeout and creating
1481speed most when you have lots of watchers, not when you only have a few of 1802speed most when you have lots of watchers, not when you only have a few of
1482them). 1803them).
1483 1804
1484EV is again fastest. 1805EV is again fastest.
1485 1806
1486Perl again comes second. It is noticably faster than the C-based event 1807Perl again comes second. It is noticeably faster than the C-based event
1487loops Event and Glib, although the difference is too small to really 1808loops Event and Glib, although the difference is too small to really
1488matter. 1809matter.
1489 1810
1490POE also performs much better in this case, but is is still far behind the 1811POE also performs much better in this case, but is is still far behind the
1491others. 1812others.
1496 1817
1497=item * C-based event loops perform very well with small number of 1818=item * C-based event loops perform very well with small number of
1498watchers, as the management overhead dominates. 1819watchers, as the management overhead dominates.
1499 1820
1500=back 1821=back
1822
1823
1824=head1 SIGNALS
1825
1826AnyEvent currently installs handlers for these signals:
1827
1828=over 4
1829
1830=item SIGCHLD
1831
1832A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
1833emulation for event loops that do not support them natively. Also, some
1834event loops install a similar handler.
1835
1836=item SIGPIPE
1837
1838A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
1839when AnyEvent gets loaded.
1840
1841The rationale for this is that AnyEvent users usually do not really depend
1842on SIGPIPE delivery (which is purely an optimisation for shell use, or
1843badly-written programs), but C<SIGPIPE> can cause spurious and rare
1844program exits as a lot of people do not expect C<SIGPIPE> when writing to
1845some random socket.
1846
1847The rationale for installing a no-op handler as opposed to ignoring it is
1848that this way, the handler will be restored to defaults on exec.
1849
1850Feel free to install your own handler, or reset it to defaults.
1851
1852=back
1853
1854=cut
1855
1856$SIG{PIPE} = sub { }
1857 unless defined $SIG{PIPE};
1501 1858
1502 1859
1503=head1 FORK 1860=head1 FORK
1504 1861
1505Most event libraries are not fork-safe. The ones who are usually are 1862Most event libraries are not fork-safe. The ones who are usually are
1520specified in the variable. 1877specified in the variable.
1521 1878
1522You can make AnyEvent completely ignore this variable by deleting it 1879You can make AnyEvent completely ignore this variable by deleting it
1523before the first watcher gets created, e.g. with a C<BEGIN> block: 1880before the first watcher gets created, e.g. with a C<BEGIN> block:
1524 1881
1525 BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} } 1882 BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1526 1883
1527 use AnyEvent; 1884 use AnyEvent;
1528 1885
1529Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can 1886Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
1530be used to probe what backend is used and gain other information (which is 1887be used to probe what backend is used and gain other information (which is
1531probably even less useful to an attacker than PERL_ANYEVENT_MODEL). 1888probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
1889$ENV{PERL_ANYEGENT_STRICT}.
1890
1891
1892=head1 BUGS
1893
1894Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
1895to work around. If you suffer from memleaks, first upgrade to Perl 5.10
1896and check wether the leaks still show up. (Perl 5.10.0 has other annoying
1897memleaks, such as leaking on C<map> and C<grep> but it is usually not as
1898pronounced).
1532 1899
1533 1900
1534=head1 SEE ALSO 1901=head1 SEE ALSO
1535 1902
1536Utility functions: L<AnyEvent::Util>. 1903Utility functions: L<AnyEvent::Util>.
1553Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>, L<AnyEvent::DNS>. 1920Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>, L<AnyEvent::DNS>.
1554 1921
1555 1922
1556=head1 AUTHOR 1923=head1 AUTHOR
1557 1924
1558 Marc Lehmann <schmorp@schmorp.de> 1925 Marc Lehmann <schmorp@schmorp.de>
1559 http://home.schmorp.de/ 1926 http://home.schmorp.de/
1560 1927
1561=cut 1928=cut
1562 1929
15631 19301
1564 1931

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