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Revision 1.47 by root, Mon Apr 14 16:09:33 2008 UTC vs.
Revision 1.84 by root, Fri Apr 25 13:48:42 2008 UTC

1=head1 NAME 1=head1 NAME
2 2
3AnyEvent - provide framework for multiple event loops 3AnyEvent - provide framework for multiple event loops
4 4
5Event, Coro, Glib, Tk, Perl - various supported event loops 5EV, Event, Coro::EV, Coro::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
14 14
15 my $w = AnyEvent->timer (after => $seconds, cb => sub { 15 my $w = AnyEvent->timer (after => $seconds, cb => sub {
16 ... 16 ...
17 }); 17 });
18 18
19 my $w = AnyEvent->condvar; # stores wether a condition was flagged 19 my $w = AnyEvent->condvar; # stores whether a condition was flagged
20 $w->wait; # enters "main loop" till $condvar gets ->broadcast 20 $w->wait; # enters "main loop" till $condvar gets ->broadcast
21 $w->broadcast; # wake up current and all future wait's 21 $w->broadcast; # wake up current and all future wait's
22 22
23=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT) 23=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
24 24
29policy> and AnyEvent is I<small and efficient>. 29policy> and AnyEvent is I<small and efficient>.
30 30
31First and foremost, I<AnyEvent is not an event model> itself, it only 31First 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 32interfaces to whatever event model the main program happens to use in a
33pragmatic way. For event models and certain classes of immortals alike, 33pragmatic way. For event models and certain classes of immortals alike,
34the statement "there can only be one" is a bitter reality, and AnyEvent 34the statement "there can only be one" is a bitter reality: In general,
35helps hiding the differences. 35only one event loop can be active at the same time in a process. AnyEvent
36helps hiding the differences between those event loops.
36 37
37The goal of AnyEvent is to offer module authors the ability to do event 38The goal of AnyEvent is to offer module authors the ability to do event
38programming (waiting for I/O or timer events) without subscribing to a 39programming (waiting for I/O or timer events) without subscribing to a
39religion, a way of living, and most importantly: without forcing your 40religion, a way of living, and most importantly: without forcing your
40module users into the same thing by forcing them to use the same event 41module users into the same thing by forcing them to use the same event
41model you use. 42model you use.
42 43
43For modules like POE or IO::Async (which is actually doing all I/O 44For modules like POE or IO::Async (which is a total misnomer as it is
44I<synchronously>...), using them in your module is like joining a 45actually doing all I/O I<synchronously>...), using them in your module is
45cult: After you joined, you are dependent on them and you cannot use 46like joining a cult: After you joined, you are dependent on them and you
46anything else, as it is simply incompatible to everything that isn't 47cannot use anything else, as it is simply incompatible to everything that
47itself. 48isn't itself. What's worse, all the potential users of your module are
49I<also> forced to use the same event loop you use.
48 50
49AnyEvent + POE works fine. AnyEvent + Glib works fine. AnyEvent + Tk 51AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
50works fine etc. etc. but none of these work together with the rest: POE 52fine. AnyEvent + Tk works fine etc. etc. but none of these work together
51+ IO::Async? no go. Tk + Event? no go. If your module uses one of 53with the rest: POE + IO::Async? no go. Tk + Event? no go. Again: if
52those, every user of your module has to use it, too. If your module 54your module uses one of those, every user of your module has to use it,
53uses AnyEvent, it works transparently with all event models it supports 55too. But if your module uses AnyEvent, it works transparently with all
54(including stuff like POE and IO::Async). 56event models it supports (including stuff like POE and IO::Async, as long
57as those use one of the supported event loops. It is trivial to add new
58event loops to AnyEvent, too, so it is future-proof).
55 59
56In addition of being free of having to use I<the one and only true event 60In addition to being free of having to use I<the one and only true event
57model>, AnyEvent also is free of bloat and policy: with POE or similar 61model>, AnyEvent also is free of bloat and policy: with POE or similar
58modules, you get an enourmous amount of code and strict rules you have 62modules, you get an enourmous amount of code and strict rules you have to
59to follow. AnyEvent, on the other hand, is lean and to the point by only 63follow. AnyEvent, on the other hand, is lean and up to the point, by only
60offering the functionality that is useful, in as thin as a wrapper as 64offering the functionality that is necessary, in as thin as a wrapper as
61technically possible. 65technically possible.
62 66
63Of course, if you want lots of policy (this can arguably be somewhat 67Of course, if you want lots of policy (this can arguably be somewhat
64useful) and you want to force your users to use the one and only event 68useful) and you want to force your users to use the one and only event
65model, you should I<not> use this module. 69model, you should I<not> use this module.
70L<AnyEvent> provides an identical interface to multiple event loops. This 74L<AnyEvent> provides an identical interface to multiple event loops. This
71allows module authors to utilise an event loop without forcing module 75allows module authors to utilise an event loop without forcing module
72users to use the same event loop (as only a single event loop can coexist 76users to use the same event loop (as only a single event loop can coexist
73peacefully at any one time). 77peacefully at any one time).
74 78
75The interface itself is vaguely similar but not identical to the Event 79The interface itself is vaguely similar, but not identical to the L<Event>
76module. 80module.
77 81
78On the first call of any method, the module tries to detect the currently 82During the first call of any watcher-creation method, the module tries
79loaded event loop by probing wether any of the following modules is 83to detect the currently loaded event loop by probing whether one of the
80loaded: L<Coro::Event>, L<Event>, L<Glib>, L<Tk>. The first one found is 84following modules is already loaded: L<Coro::EV>, L<Coro::Event>, L<EV>,
81used. If none is found, the module tries to load these modules in the 85L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>,
82order given. The first one that could be successfully loaded will be 86L<POE>. The first one found is used. If none are found, the module tries
83used. If still none could be found, AnyEvent will fall back to a pure-perl 87to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl
84event loop, which is also not very efficient. 88adaptor should always succeed) in the order given. The first one that can
89be successfully loaded will be used. If, after this, still none could be
90found, AnyEvent will fall back to a pure-perl event loop, which is not
91very efficient, but should work everywhere.
85 92
86Because AnyEvent first checks for modules that are already loaded, loading 93Because AnyEvent first checks for modules that are already loaded, loading
87an Event model explicitly before first using AnyEvent will likely make 94an event model explicitly before first using AnyEvent will likely make
88that model the default. For example: 95that model the default. For example:
89 96
90 use Tk; 97 use Tk;
91 use AnyEvent; 98 use AnyEvent;
92 99
93 # .. AnyEvent will likely default to Tk 100 # .. AnyEvent will likely default to Tk
101
102The I<likely> means that, if any module loads another event model and
103starts using it, all bets are off. Maybe you should tell their authors to
104use AnyEvent so their modules work together with others seamlessly...
94 105
95The pure-perl implementation of AnyEvent is called 106The pure-perl implementation of AnyEvent is called
96C<AnyEvent::Impl::Perl>. Like other event modules you can load it 107C<AnyEvent::Impl::Perl>. Like other event modules you can load it
97explicitly. 108explicitly.
98 109
101AnyEvent has the central concept of a I<watcher>, which is an object that 112AnyEvent has the central concept of a I<watcher>, which is an object that
102stores relevant data for each kind of event you are waiting for, such as 113stores relevant data for each kind of event you are waiting for, such as
103the callback to call, the filehandle to watch, etc. 114the callback to call, the filehandle to watch, etc.
104 115
105These watchers are normal Perl objects with normal Perl lifetime. After 116These watchers are normal Perl objects with normal Perl lifetime. After
106creating a watcher it will immediately "watch" for events and invoke 117creating a watcher it will immediately "watch" for events and invoke the
118callback when the event occurs (of course, only when the event model
119is in control).
120
107the callback. To disable the watcher you have to destroy it (e.g. by 121To disable the watcher you have to destroy it (e.g. by setting the
108setting the variable that stores it to C<undef> or otherwise deleting all 122variable you store it in to C<undef> or otherwise deleting all references
109references to it). 123to it).
110 124
111All watchers are created by calling a method on the C<AnyEvent> class. 125All watchers are created by calling a method on the C<AnyEvent> class.
112 126
127Many watchers either are used with "recursion" (repeating timers for
128example), or need to refer to their watcher object in other ways.
129
130An any way to achieve that is this pattern:
131
132 my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
133 # you can use $w here, for example to undef it
134 undef $w;
135 });
136
137Note that C<my $w; $w => combination. This is necessary because in Perl,
138my variables are only visible after the statement in which they are
139declared.
140
113=head2 IO WATCHERS 141=head2 I/O WATCHERS
114 142
115You can create I/O watcher by calling the C<< AnyEvent->io >> method with 143You can create an I/O watcher by calling the C<< AnyEvent->io >> method
116the following mandatory arguments: 144with the following mandatory key-value pairs as arguments:
117 145
118C<fh> the Perl I<filehandle> (not filedescriptor) to watch for 146C<fh> the Perl I<file handle> (I<not> file descriptor) to watch for
119events. C<poll> must be a string that is either C<r> or C<w>, that creates 147events. C<poll> must be a string that is either C<r> or C<w>, which
120a watcher waiting for "r"eadable or "w"ritable events. C<cb> the callback 148creates a watcher waiting for "r"eadable or "w"ritable events,
121to invoke everytime the filehandle becomes ready. 149respectively. C<cb> is the callback to invoke each time the file handle
150becomes ready.
122 151
123Only one io watcher per C<fh> and C<poll> combination is allowed (i.e. on 152The I/O watcher might use the underlying file descriptor or a copy of it.
124a socket you can have one r + one w, not any more (limitation comes from 153You must not close a file handle as long as any watcher is active on the
125Tk - if you are sure you are not using Tk this limitation is gone). 154underlying file descriptor.
126 155
127Filehandles will be kept alive, so as long as the watcher exists, the 156Some event loops issue spurious readyness notifications, so you should
128filehandle exists, too. 157always use non-blocking calls when reading/writing from/to your file
158handles.
159
160Although the callback might get passed parameters, their value and
161presence is undefined and you cannot rely on them. Portable AnyEvent
162callbacks cannot use arguments passed to I/O watcher callbacks.
129 163
130Example: 164Example:
131 165
132 # wait for readability of STDIN, then read a line and disable the watcher 166 # wait for readability of STDIN, then read a line and disable the watcher
133 my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub { 167 my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
139=head2 TIME WATCHERS 173=head2 TIME WATCHERS
140 174
141You can create a time watcher by calling the C<< AnyEvent->timer >> 175You can create a time watcher by calling the C<< AnyEvent->timer >>
142method with the following mandatory arguments: 176method with the following mandatory arguments:
143 177
144C<after> after how many seconds (fractions are supported) should the timer 178C<after> specifies after how many seconds (fractional values are
145activate. C<cb> the callback to invoke. 179supported) should the timer activate. C<cb> the callback to invoke in that
180case.
146 181
147The timer callback will be invoked at most once: if you want a repeating 182The timer callback will be invoked at most once: if you want a repeating
148timer you have to create a new watcher (this is a limitation by both Tk 183timer you have to create a new watcher (this is a limitation by both Tk
149and Glib). 184and Glib).
185
186Although the callback might get passed parameters, their value and
187presence is undefined and you cannot rely on them. Portable AnyEvent
188callbacks cannot use arguments passed to time watcher callbacks.
150 189
151Example: 190Example:
152 191
153 # fire an event after 7.7 seconds 192 # fire an event after 7.7 seconds
154 my $w = AnyEvent->timer (after => 7.7, cb => sub { 193 my $w = AnyEvent->timer (after => 7.7, cb => sub {
156 }); 195 });
157 196
158 # to cancel the timer: 197 # to cancel the timer:
159 undef $w; 198 undef $w;
160 199
200Example 2:
201
202 # fire an event after 0.5 seconds, then roughly every second
203 my $w;
204
205 my $cb = sub {
206 # cancel the old timer while creating a new one
207 $w = AnyEvent->timer (after => 1, cb => $cb);
208 };
209
210 # start the "loop" by creating the first watcher
211 $w = AnyEvent->timer (after => 0.5, cb => $cb);
212
213=head3 TIMING ISSUES
214
215There are two ways to handle timers: based on real time (relative, "fire
216in 10 seconds") and based on wallclock time (absolute, "fire at 12
217o'clock").
218
219While most event loops expect timers to specified in a relative way, they
220use absolute time internally. This makes a difference when your clock
221"jumps", for example, when ntp decides to set your clock backwards from
222the wrong date of 2014-01-01 to 2008-01-01, a watcher that is supposed to
223fire "after" a second might actually take six years to finally fire.
224
225AnyEvent cannot compensate for this. The only event loop that is conscious
226about these issues is L<EV>, which offers both relative (ev_timer, based
227on true relative time) and absolute (ev_periodic, based on wallclock time)
228timers.
229
230AnyEvent always prefers relative timers, if available, matching the
231AnyEvent API.
232
233=head2 SIGNAL WATCHERS
234
235You can watch for signals using a signal watcher, C<signal> is the signal
236I<name> without any C<SIG> prefix, C<cb> is the Perl callback to
237be invoked whenever a signal occurs.
238
239Multiple signal occurances can be clumped together into one callback
240invocation, and callback invocation will be synchronous. synchronous means
241that it might take a while until the signal gets handled by the process,
242but it is guarenteed not to interrupt any other callbacks.
243
244The main advantage of using these watchers is that you can share a signal
245between multiple watchers.
246
247This watcher might use C<%SIG>, so programs overwriting those signals
248directly will likely not work correctly.
249
250Example: exit on SIGINT
251
252 my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
253
254=head2 CHILD PROCESS WATCHERS
255
256You can also watch on a child process exit and catch its exit status.
257
258The child process is specified by the C<pid> argument (if set to C<0>, it
259watches for any child process exit). The watcher will trigger as often
260as status change for the child are received. This works by installing a
261signal handler for C<SIGCHLD>. The callback will be called with the pid
262and exit status (as returned by waitpid).
263
264There is a slight catch to child watchers, however: you usually start them
265I<after> the child process was created, and this means the process could
266have exited already (and no SIGCHLD will be sent anymore).
267
268Not all event models handle this correctly (POE doesn't), but even for
269event models that I<do> handle this correctly, they usually need to be
270loaded before the process exits (i.e. before you fork in the first place).
271
272This means you cannot create a child watcher as the very first thing in an
273AnyEvent program, you I<have> to create at least one watcher before you
274C<fork> the child (alternatively, you can call C<AnyEvent::detect>).
275
276Example: fork a process and wait for it
277
278 my $done = AnyEvent->condvar;
279
280 AnyEvent::detect; # force event module to be initialised
281
282 my $pid = fork or exit 5;
283
284 my $w = AnyEvent->child (
285 pid => $pid,
286 cb => sub {
287 my ($pid, $status) = @_;
288 warn "pid $pid exited with status $status";
289 $done->broadcast;
290 },
291 );
292
293 # do something else, then wait for process exit
294 $done->wait;
295
161=head2 CONDITION WATCHERS 296=head2 CONDITION VARIABLES
162 297
163Condition watchers can be created by calling the C<< AnyEvent->condvar >> 298Condition variables can be created by calling the C<< AnyEvent->condvar >>
164method without any arguments. 299method without any arguments.
165 300
166A condition watcher watches for a condition - precisely that the C<< 301A condition variable waits for a condition - precisely that the C<<
167->broadcast >> method has been called. 302->broadcast >> method has been called.
168 303
304They are very useful to signal that a condition has been fulfilled, for
305example, if you write a module that does asynchronous http requests,
306then a condition variable would be the ideal candidate to signal the
307availability of results.
308
309You can also use condition variables to block your main program until
310an event occurs - for example, you could C<< ->wait >> in your main
311program until the user clicks the Quit button in your app, which would C<<
312->broadcast >> the "quit" event.
313
169Note that condition watchers recurse into the event loop - if you have 314Note that condition variables recurse into the event loop - if you have
170two watchers that call C<< ->wait >> in a round-robbin fashion, you 315two pirces of code that call C<< ->wait >> in a round-robbin fashion, you
171lose. Therefore, condition watchers are good to export to your caller, but 316lose. Therefore, condition variables are good to export to your caller, but
172you should avoid making a blocking wait, at least in callbacks, as this 317you should avoid making a blocking wait yourself, at least in callbacks,
173usually asks for trouble. 318as this asks for trouble.
174 319
175The watcher has only two methods: 320This object has two methods:
176 321
177=over 4 322=over 4
178 323
179=item $cv->wait 324=item $cv->wait
180 325
183 328
184You can only wait once on a condition - additional calls will return 329You can only wait once on a condition - additional calls will return
185immediately. 330immediately.
186 331
187Not all event models support a blocking wait - some die in that case 332Not all event models support a blocking wait - some die in that case
188(programs might want to do that so they stay interactive), so I<if you 333(programs might want to do that to stay interactive), so I<if you are
189are using this from a module, never require a blocking wait>, but let the 334using this from a module, never require a blocking wait>, but let the
190caller decide wether the call will block or not (for example, by coupling 335caller decide whether the call will block or not (for example, by coupling
191condition variables with some kind of request results and supporting 336condition variables with some kind of request results and supporting
192callbacks so the caller knows that getting the result will not block, 337callbacks so the caller knows that getting the result will not block,
193while still suppporting blocking waits if the caller so desires). 338while still suppporting blocking waits if the caller so desires).
194 339
195Another reason I<never> to C<< ->wait >> in a module is that you cannot 340Another reason I<never> to C<< ->wait >> in a module is that you cannot
196sensibly have two C<< ->wait >>'s in parallel, as that would require 341sensibly have two C<< ->wait >>'s in parallel, as that would require
197multiple interpreters or coroutines/threads, none of which C<AnyEvent> 342multiple interpreters or coroutines/threads, none of which C<AnyEvent>
198can supply (the coroutine-aware backends C<Coro::EV> and C<Coro::Event> 343can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and
199explicitly support concurrent C<< ->wait >>'s from different coroutines, 344L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
200however). 345from different coroutines, however).
201 346
202=item $cv->broadcast 347=item $cv->broadcast
203 348
204Flag the condition as ready - a running C<< ->wait >> and all further 349Flag the condition as ready - a running C<< ->wait >> and all further
205calls to C<wait> will return after this method has been called. If nobody 350calls to C<wait> will (eventually) return after this method has been
206is waiting the broadcast will be remembered.. 351called. If nobody is waiting the broadcast will be remembered..
352
353=back
207 354
208Example: 355Example:
209 356
210 # wait till the result is ready 357 # wait till the result is ready
211 my $result_ready = AnyEvent->condvar; 358 my $result_ready = AnyEvent->condvar;
212 359
213 # do something such as adding a timer 360 # do something such as adding a timer
214 # or socket watcher the calls $result_ready->broadcast 361 # or socket watcher the calls $result_ready->broadcast
215 # when the "result" is ready. 362 # when the "result" is ready.
363 # in this case, we simply use a timer:
364 my $w = AnyEvent->timer (
365 after => 1,
366 cb => sub { $result_ready->broadcast },
367 );
216 368
369 # this "blocks" (while handling events) till the watcher
370 # calls broadcast
217 $result_ready->wait; 371 $result_ready->wait;
218 372
219=back 373=head1 GLOBAL VARIABLES AND FUNCTIONS
220
221=head2 SIGNAL WATCHERS
222
223You can listen for signals using a signal watcher, C<signal> is the signal
224I<name> without any C<SIG> prefix. Multiple signals events can be clumped
225together into one callback invocation, and callback invocation might or
226might not be asynchronous.
227
228These watchers might use C<%SIG>, so programs overwriting those signals
229directly will likely not work correctly.
230
231Example: exit on SIGINT
232
233 my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
234
235=head2 CHILD PROCESS WATCHERS
236
237You can also listen for the status of a child process specified by the
238C<pid> argument (or any child if the pid argument is 0). The watcher will
239trigger as often as status change for the child are received. This works
240by installing a signal handler for C<SIGCHLD>. The callback will be called with
241the pid and exit status (as returned by waitpid).
242
243Example: wait for pid 1333
244
245 my $w = AnyEvent->child (pid => 1333, cb => sub { warn "exit status $?" });
246
247=head1 GLOBALS
248 374
249=over 4 375=over 4
250 376
251=item $AnyEvent::MODEL 377=item $AnyEvent::MODEL
252 378
257AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>). 383AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).
258 384
259The known classes so far are: 385The known classes so far are:
260 386
261 AnyEvent::Impl::CoroEV based on Coro::EV, best choice. 387 AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
262 AnyEvent::Impl::EV based on EV (an interface to libev, also best choice).
263 AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice. 388 AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
389 AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
264 AnyEvent::Impl::Event based on Event, also second best choice :) 390 AnyEvent::Impl::Event based on Event, second best choice.
265 AnyEvent::Impl::Glib based on Glib, second-best choice. 391 AnyEvent::Impl::Glib based on Glib, third-best choice.
392 AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
266 AnyEvent::Impl::Tk based on Tk, very bad choice. 393 AnyEvent::Impl::Tk based on Tk, very bad choice.
267 AnyEvent::Impl::Perl pure-perl implementation, inefficient. 394 AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
395 AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
396 AnyEvent::Impl::POE based on POE, not generic enough for full support.
397
398There is no support for WxWidgets, as WxWidgets has no support for
399watching file handles. However, you can use WxWidgets through the
400POE Adaptor, as POE has a Wx backend that simply polls 20 times per
401second, which was considered to be too horrible to even consider for
402AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
403it's adaptor.
404
405AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
406autodetecting them.
268 407
269=item AnyEvent::detect 408=item AnyEvent::detect
270 409
271Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model if 410Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
272necessary. You should only call this function right before you would have 411if necessary. You should only call this function right before you would
273created an AnyEvent watcher anyway, that is, very late at runtime. 412have created an AnyEvent watcher anyway, that is, as late as possible at
413runtime.
274 414
275=back 415=back
276 416
277=head1 WHAT TO DO IN A MODULE 417=head1 WHAT TO DO IN A MODULE
278 418
279As a module author, you should "use AnyEvent" and call AnyEvent methods 419As a module author, you should C<use AnyEvent> and call AnyEvent methods
280freely, but you should not load a specific event module or rely on it. 420freely, but you should not load a specific event module or rely on it.
281 421
282Be careful when you create watchers in the module body - Anyevent will 422Be careful when you create watchers in the module body - AnyEvent will
283decide which event module to use as soon as the first method is called, so 423decide which event module to use as soon as the first method is called, so
284by calling AnyEvent in your module body you force the user of your module 424by calling AnyEvent in your module body you force the user of your module
285to load the event module first. 425to load the event module first.
286 426
427Never call C<< ->wait >> on a condition variable unless you I<know> that
428the C<< ->broadcast >> method has been called on it already. This is
429because it will stall the whole program, and the whole point of using
430events is to stay interactive.
431
432It is fine, however, to call C<< ->wait >> when the user of your module
433requests it (i.e. if you create a http request object ad have a method
434called C<results> that returns the results, it should call C<< ->wait >>
435freely, as the user of your module knows what she is doing. always).
436
287=head1 WHAT TO DO IN THE MAIN PROGRAM 437=head1 WHAT TO DO IN THE MAIN PROGRAM
288 438
289There will always be a single main program - the only place that should 439There will always be a single main program - the only place that should
290dictate which event model to use. 440dictate which event model to use.
291 441
292If it doesn't care, it can just "use AnyEvent" and use it itself, or not 442If it doesn't care, it can just "use AnyEvent" and use it itself, or not
293do anything special and let AnyEvent decide which implementation to chose. 443do anything special (it does not need to be event-based) and let AnyEvent
444decide which implementation to chose if some module relies on it.
294 445
295If the main program relies on a specific event model (for example, in Gtk2 446If the main program relies on a specific event model. For example, in
296programs you have to rely on either Glib or Glib::Event), you should load 447Gtk2 programs you have to rely on the Glib module. You should load the
297it before loading AnyEvent or any module that uses it, generally, as early 448event module before loading AnyEvent or any module that uses it: generally
298as possible. The reason is that modules might create watchers when they 449speaking, you should load it as early as possible. The reason is that
299are loaded, and AnyEvent will decide on the event model to use as soon as 450modules might create watchers when they are loaded, and AnyEvent will
300it creates watchers, and it might chose the wrong one unless you load the 451decide on the event model to use as soon as it creates watchers, and it
301correct one yourself. 452might chose the wrong one unless you load the correct one yourself.
302 453
303You can chose to use a rather inefficient pure-perl implementation by 454You can chose to use a rather inefficient pure-perl implementation by
304loading the C<AnyEvent::Impl::Perl> module, but letting AnyEvent chose is 455loading the C<AnyEvent::Impl::Perl> module, which gives you similar
305generally better. 456behaviour everywhere, but letting AnyEvent chose is generally better.
306 457
307=cut 458=cut
308 459
309package AnyEvent; 460package AnyEvent;
310 461
311no warnings; 462no warnings;
312use strict; 463use strict;
313 464
314use Carp; 465use Carp;
315 466
316our $VERSION = '3.0'; 467our $VERSION = '3.3';
317our $MODEL; 468our $MODEL;
318 469
319our $AUTOLOAD; 470our $AUTOLOAD;
320our @ISA; 471our @ISA;
321 472
323 474
324our @REGISTRY; 475our @REGISTRY;
325 476
326my @models = ( 477my @models = (
327 [Coro::EV:: => AnyEvent::Impl::CoroEV::], 478 [Coro::EV:: => AnyEvent::Impl::CoroEV::],
479 [Coro::Event:: => AnyEvent::Impl::CoroEvent::],
328 [EV:: => AnyEvent::Impl::EV::], 480 [EV:: => AnyEvent::Impl::EV::],
329 [Coro::Event:: => AnyEvent::Impl::CoroEvent::],
330 [Event:: => AnyEvent::Impl::Event::], 481 [Event:: => AnyEvent::Impl::Event::],
331 [Glib:: => AnyEvent::Impl::Glib::], 482 [Glib:: => AnyEvent::Impl::Glib::],
332 [Tk:: => AnyEvent::Impl::Tk::], 483 [Tk:: => AnyEvent::Impl::Tk::],
484 [Wx:: => AnyEvent::Impl::POE::],
485 [Prima:: => AnyEvent::Impl::POE::],
333 [AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::], 486 [AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
487 # everything below here will not be autoprobed as the pureperl backend should work everywhere
488 [Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
489 [Qt:: => AnyEvent::Impl::Qt::], # requires special main program
490 [POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
334); 491);
335 492
336our %method = map +($_ => 1), qw(io timer condvar broadcast wait signal one_event DESTROY); 493our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY);
337 494
338sub detect() { 495sub detect() {
339 unless ($MODEL) { 496 unless ($MODEL) {
340 no strict 'refs'; 497 no strict 'refs';
341 498
499 if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
500 my $model = "AnyEvent::Impl::$1";
501 if (eval "require $model") {
502 $MODEL = $model;
503 warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;
504 } else {
505 warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;
506 }
507 }
508
342 # check for already loaded models 509 # check for already loaded models
510 unless ($MODEL) {
343 for (@REGISTRY, @models) { 511 for (@REGISTRY, @models) {
344 my ($package, $model) = @$_; 512 my ($package, $model) = @$_;
345 if (${"$package\::VERSION"} > 0) { 513 if (${"$package\::VERSION"} > 0) {
346 if (eval "require $model") { 514 if (eval "require $model") {
347 $MODEL = $model; 515 $MODEL = $model;
348 warn "AnyEvent: found model '$model', using it.\n" if $verbose > 1; 516 warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;
349 last; 517 last;
518 }
350 } 519 }
351 } 520 }
352 }
353 521
354 unless ($MODEL) { 522 unless ($MODEL) {
355 # try to load a model 523 # try to load a model
356 524
357 for (@REGISTRY, @models) { 525 for (@REGISTRY, @models) {
358 my ($package, $model) = @$_; 526 my ($package, $model) = @$_;
359 if (eval "require $package" 527 if (eval "require $package"
360 and ${"$package\::VERSION"} > 0 528 and ${"$package\::VERSION"} > 0
361 and eval "require $model") { 529 and eval "require $model") {
362 $MODEL = $model; 530 $MODEL = $model;
363 warn "AnyEvent: autoprobed and loaded model '$model', using it.\n" if $verbose > 1; 531 warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;
364 last; 532 last;
533 }
365 } 534 }
535
536 $MODEL
537 or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV (or Coro+EV), Event (or Coro+Event) or Glib.";
366 } 538 }
367
368 $MODEL
369 or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV (or Coro+EV), Event (or Coro+Event), Glib or Tk.";
370 } 539 }
371 540
372 unshift @ISA, $MODEL; 541 unshift @ISA, $MODEL;
373 push @{"$MODEL\::ISA"}, "AnyEvent::Base"; 542 push @{"$MODEL\::ISA"}, "AnyEvent::Base";
374 } 543 }
485 undef $CHLD_W unless keys %PID_CB; 654 undef $CHLD_W unless keys %PID_CB;
486} 655}
487 656
488=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE 657=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
489 658
659This is an advanced topic that you do not normally need to use AnyEvent in
660a module. This section is only of use to event loop authors who want to
661provide AnyEvent compatibility.
662
490If you need to support another event library which isn't directly 663If you need to support another event library which isn't directly
491supported by AnyEvent, you can supply your own interface to it by 664supported by AnyEvent, you can supply your own interface to it by
492pushing, before the first watcher gets created, the package name of 665pushing, before the first watcher gets created, the package name of
493the event module and the package name of the interface to use onto 666the event module and the package name of the interface to use onto
494C<@AnyEvent::REGISTRY>. You can do that before and even without loading 667C<@AnyEvent::REGISTRY>. You can do that before and even without loading
495AnyEvent. 668AnyEvent, so it is reasonably cheap.
496 669
497Example: 670Example:
498 671
499 push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::]; 672 push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];
500 673
501This tells AnyEvent to (literally) use the C<urxvt::anyevent::> 674This tells AnyEvent to (literally) use the C<urxvt::anyevent::>
502package/class when it finds the C<urxvt> package/module is loaded. When 675package/class when it finds the C<urxvt> package/module is already loaded.
676
503AnyEvent is loaded and asked to find a suitable event model, it will 677When AnyEvent is loaded and asked to find a suitable event model, it
504first check for the presence of urxvt. 678will first check for the presence of urxvt by trying to C<use> the
679C<urxvt::anyevent> module.
505 680
506The class should provide implementations for all watcher types (see 681The class should provide implementations for all watcher types. See
507L<AnyEvent::Impl::Event> (source code), L<AnyEvent::Impl::Glib> 682L<AnyEvent::Impl::EV> (source code), L<AnyEvent::Impl::Glib> (Source code)
508(Source code) and so on for actual examples, use C<perldoc -m 683and so on for actual examples. Use C<perldoc -m AnyEvent::Impl::Glib> to
509AnyEvent::Impl::Glib> to see the sources). 684see the sources.
510 685
686If you don't provide C<signal> and C<child> watchers than AnyEvent will
687provide suitable (hopefully) replacements.
688
511The above isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt) 689The above example isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt)
512uses the above line as-is. An interface isn't included in AnyEvent 690terminal emulator uses the above line as-is. An interface isn't included
513because it doesn't make sense outside the embedded interpreter inside 691in AnyEvent because it doesn't make sense outside the embedded interpreter
514I<rxvt-unicode>, and it is updated and maintained as part of the 692inside I<rxvt-unicode>, and it is updated and maintained as part of the
515I<rxvt-unicode> distribution. 693I<rxvt-unicode> distribution.
516 694
517I<rxvt-unicode> also cheats a bit by not providing blocking access to 695I<rxvt-unicode> also cheats a bit by not providing blocking access to
518condition variables: code blocking while waiting for a condition will 696condition variables: code blocking while waiting for a condition will
519C<die>. This still works with most modules/usages, and blocking calls must 697C<die>. This still works with most modules/usages, and blocking calls must
520not be in an interactive application, so it makes sense. 698not be done in an interactive application, so it makes sense.
521 699
522=head1 ENVIRONMENT VARIABLES 700=head1 ENVIRONMENT VARIABLES
523 701
524The following environment variables are used by this module: 702The following environment variables are used by this module:
525 703
526C<PERL_ANYEVENT_VERBOSE> when set to C<2> or higher, reports which event 704=over 4
527model gets used.
528 705
706=item C<PERL_ANYEVENT_VERBOSE>
707
708By default, AnyEvent will be completely silent except in fatal
709conditions. You can set this environment variable to make AnyEvent more
710talkative.
711
712When set to C<1> or higher, causes AnyEvent to warn about unexpected
713conditions, such as not being able to load the event model specified by
714C<PERL_ANYEVENT_MODEL>.
715
716When set to C<2> or higher, cause AnyEvent to report to STDERR which event
717model it chooses.
718
719=item C<PERL_ANYEVENT_MODEL>
720
721This can be used to specify the event model to be used by AnyEvent, before
722autodetection and -probing kicks in. It must be a string consisting
723entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
724and the resulting module name is loaded and if the load was successful,
725used as event model. If it fails to load AnyEvent will proceed with
726autodetection and -probing.
727
728This functionality might change in future versions.
729
730For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
731could start your program like this:
732
733 PERL_ANYEVENT_MODEL=Perl perl ...
734
735=back
736
529=head1 EXAMPLE 737=head1 EXAMPLE PROGRAM
530 738
531The following program uses an io watcher to read data from stdin, a timer 739The following program uses an I/O watcher to read data from STDIN, a timer
532to display a message once per second, and a condvar to exit the program 740to display a message once per second, and a condition variable to quit the
533when the user enters quit: 741program when the user enters quit:
534 742
535 use AnyEvent; 743 use AnyEvent;
536 744
537 my $cv = AnyEvent->condvar; 745 my $cv = AnyEvent->condvar;
538 746
539 my $io_watcher = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub { 747 my $io_watcher = AnyEvent->io (
748 fh => \*STDIN,
749 poll => 'r',
750 cb => sub {
540 warn "io event <$_[0]>\n"; # will always output <r> 751 warn "io event <$_[0]>\n"; # will always output <r>
541 chomp (my $input = <STDIN>); # read a line 752 chomp (my $input = <STDIN>); # read a line
542 warn "read: $input\n"; # output what has been read 753 warn "read: $input\n"; # output what has been read
543 $cv->broadcast if $input =~ /^q/i; # quit program if /^q/i 754 $cv->broadcast if $input =~ /^q/i; # quit program if /^q/i
755 },
544 }); 756 );
545 757
546 my $time_watcher; # can only be used once 758 my $time_watcher; # can only be used once
547 759
548 sub new_timer { 760 sub new_timer {
549 $timer = AnyEvent->timer (after => 1, cb => sub { 761 $timer = AnyEvent->timer (after => 1, cb => sub {
631 $txn->{finished}->wait; 843 $txn->{finished}->wait;
632 return $txn->{result}; 844 return $txn->{result};
633 845
634The actual code goes further and collects all errors (C<die>s, exceptions) 846The actual code goes further and collects all errors (C<die>s, exceptions)
635that occured during request processing. The C<result> method detects 847that occured during request processing. The C<result> method detects
636wether an exception as thrown (it is stored inside the $txn object) 848whether an exception as thrown (it is stored inside the $txn object)
637and just throws the exception, which means connection errors and other 849and just throws the exception, which means connection errors and other
638problems get reported tot he code that tries to use the result, not in a 850problems get reported tot he code that tries to use the result, not in a
639random callback. 851random callback.
640 852
641All of this enables the following usage styles: 853All of this enables the following usage styles:
642 854
6431. Blocking: 8551. Blocking:
644 856
645 my $data = $fcp->client_get ($url); 857 my $data = $fcp->client_get ($url);
646 858
6472. Blocking, but parallelizing: 8592. Blocking, but running in parallel:
648 860
649 my @datas = map $_->result, 861 my @datas = map $_->result,
650 map $fcp->txn_client_get ($_), 862 map $fcp->txn_client_get ($_),
651 @urls; 863 @urls;
652 864
653Both blocking examples work without the module user having to know 865Both blocking examples work without the module user having to know
654anything about events. 866anything about events.
655 867
6563a. Event-based in a main program, using any support Event module: 8683a. Event-based in a main program, using any supported event module:
657 869
658 use Event; 870 use EV;
659 871
660 $fcp->txn_client_get ($url)->cb (sub { 872 $fcp->txn_client_get ($url)->cb (sub {
661 my $txn = shift; 873 my $txn = shift;
662 my $data = $txn->result; 874 my $data = $txn->result;
663 ... 875 ...
664 }); 876 });
665 877
666 Event::loop; 878 EV::loop;
667 879
6683b. The module user could use AnyEvent, too: 8803b. The module user could use AnyEvent, too:
669 881
670 use AnyEvent; 882 use AnyEvent;
671 883
676 $quit->broadcast; 888 $quit->broadcast;
677 }); 889 });
678 890
679 $quit->wait; 891 $quit->wait;
680 892
893
894=head1 BENCHMARK
895
896To give you an idea of the performance and overheads that AnyEvent adds
897over the event loops themselves (and to give you an impression of the
898speed of various event loops), here is a benchmark of various supported
899event models natively and with anyevent. The benchmark creates a lot of
900timers (with a zero timeout) and I/O watchers (watching STDOUT, a pty, to
901become writable, which it is), lets them fire exactly once and destroys
902them again.
903
904Rewriting the benchmark to use many different sockets instead of using
905the same filehandle for all I/O watchers results in a much longer runtime
906(socket creation is expensive), but qualitatively the same figures, so it
907was not used.
908
909=head2 Explanation of the columns
910
911I<watcher> is the number of event watchers created/destroyed. Since
912different event models feature vastly different performances, each event
913loop was given a number of watchers so that overall runtime is acceptable
914and similar between tested event loop (and keep them from crashing): Glib
915would probably take thousands of years if asked to process the same number
916of watchers as EV in this benchmark.
917
918I<bytes> is the number of bytes (as measured by the resident set size,
919RSS) consumed by each watcher. This method of measuring captures both C
920and Perl-based overheads.
921
922I<create> is the time, in microseconds (millionths of seconds), that it
923takes to create a single watcher. The callback is a closure shared between
924all watchers, to avoid adding memory overhead. That means closure creation
925and memory usage is not included in the figures.
926
927I<invoke> is the time, in microseconds, used to invoke a simple
928callback. The callback simply counts down a Perl variable and after it was
929invoked "watcher" times, it would C<< ->broadcast >> a condvar once to
930signal the end of this phase.
931
932I<destroy> is the time, in microseconds, that it takes to destroy a single
933watcher.
934
935=head2 Results
936
937 name watchers bytes create invoke destroy comment
938 EV/EV 400000 244 0.56 0.46 0.31 EV native interface
939 EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers
940 CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal
941 Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation
942 Event/Event 16000 516 31.88 31.30 0.85 Event native interface
943 Event/Any 16000 936 39.17 33.63 1.43 Event + AnyEvent watchers
944 Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour
945 Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers
946 POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event
947 POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select
948
949=head2 Discussion
950
951The benchmark does I<not> measure scalability of the event loop very
952well. For example, a select-based event loop (such as the pure perl one)
953can never compete with an event loop that uses epoll when the number of
954file descriptors grows high. In this benchmark, all events become ready at
955the same time, so select/poll-based implementations get an unnatural speed
956boost.
957
958C<EV> is the sole leader regarding speed and memory use, which are both
959maximal/minimal, respectively. Even when going through AnyEvent, it uses
960far less memory than any other event loop and is still faster than Event
961natively.
962
963The pure perl implementation is hit in a few sweet spots (both the
964zero timeout and the use of a single fd hit optimisations in the perl
965interpreter and the backend itself, and all watchers become ready at the
966same time). Nevertheless this shows that it adds very little overhead in
967itself. Like any select-based backend its performance becomes really bad
968with lots of file descriptors (and few of them active), of course, but
969this was not subject of this benchmark.
970
971The C<Event> module has a relatively high setup and callback invocation cost,
972but overall scores on the third place.
973
974C<Glib>'s memory usage is quite a bit bit higher, but it features a
975faster callback invocation and overall ends up in the same class as
976C<Event>. However, Glib scales extremely badly, doubling the number of
977watchers increases the processing time by more than a factor of four,
978making it completely unusable when using larger numbers of watchers
979(note that only a single file descriptor was used in the benchmark, so
980inefficiencies of C<poll> do not account for this).
981
982The C<Tk> adaptor works relatively well. The fact that it crashes with
983more than 2000 watchers is a big setback, however, as correctness takes
984precedence over speed. Nevertheless, its performance is surprising, as the
985file descriptor is dup()ed for each watcher. This shows that the dup()
986employed by some adaptors is not a big performance issue (it does incur a
987hidden memory cost inside the kernel, though, that is not reflected in the
988figures above).
989
990C<POE>, regardless of underlying event loop (wether using its pure perl
991select-based backend or the Event module) shows abysmal performance and
992memory usage: Watchers use almost 30 times as much memory as EV watchers,
993and 10 times as much memory as both Event or EV via AnyEvent. Watcher
994invocation is almost 900 times slower than with AnyEvent's pure perl
995implementation. The design of the POE adaptor class in AnyEvent can not
996really account for this, as session creation overhead is small compared
997to execution of the state machine, which is coded pretty optimally within
998L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow.
999
1000=head2 Summary
1001
1002Using EV through AnyEvent is faster than any other event loop, but most
1003event loops have acceptable performance with or without AnyEvent.
1004
1005The overhead AnyEvent adds is usually much smaller than the overhead of
1006the actual event loop, only with extremely fast event loops such as the EV
1007adds AnyEvent significant overhead.
1008
1009And you should simply avoid POE like the plague if you want performance or
1010reasonable memory usage.
1011
1012
1013=head1 FORK
1014
1015Most event libraries are not fork-safe. The ones who are usually are
1016because they are so inefficient. Only L<EV> is fully fork-aware.
1017
1018If you have to fork, you must either do so I<before> creating your first
1019watcher OR you must not use AnyEvent at all in the child.
1020
1021
1022=head1 SECURITY CONSIDERATIONS
1023
1024AnyEvent can be forced to load any event model via
1025$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to
1026execute arbitrary code or directly gain access, it can easily be used to
1027make the program hang or malfunction in subtle ways, as AnyEvent watchers
1028will not be active when the program uses a different event model than
1029specified in the variable.
1030
1031You can make AnyEvent completely ignore this variable by deleting it
1032before the first watcher gets created, e.g. with a C<BEGIN> block:
1033
1034 BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1035
1036 use AnyEvent;
1037
1038
681=head1 SEE ALSO 1039=head1 SEE ALSO
682 1040
683Event modules: L<Coro::Event>, L<Coro>, L<Event>, L<Glib::Event>, L<Glib>. 1041Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,
1042L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,
1043L<Event::Lib>, L<Qt>, L<POE>.
684 1044
1045Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,
685Implementations: L<AnyEvent::Impl::Coro>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>. 1046L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,
1047L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,
1048L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>.
686 1049
687Nontrivial usage example: L<Net::FCP>. 1050Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.
688 1051
689=head1 1052
1053=head1 AUTHOR
1054
1055 Marc Lehmann <schmorp@schmorp.de>
1056 http://home.schmorp.de/
690 1057
691=cut 1058=cut
692 1059
6931 10601
694 1061

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