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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
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 is arguably somewhat useful 67Of course, if you want lots of policy (this can arguably be somewhat
64in many cases) and you want to force your users to the one and only event 68useful) and you want to force your users to use the one and only event
65model your module forces on them, you should I<not> use this module. 69model, you should I<not> use this module.
66 70
67 71
68=head1 DESCRIPTION 72=head1 DESCRIPTION
69 73
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<Tk>, L<AnyEvent::Impl::Perl>, 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 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 152As long as the I/O watcher exists it will keep the file descriptor or a
124a socket you can have one r + one w, not any more (limitation comes from 153copy of it alive/open.
125Tk - if you are sure you are not using Tk this limitation is gone).
126 154
127Filehandles will be kept alive, so as long as the watcher exists, the 155It is not allowed to close a file handle as long as any watcher is active
128filehandle exists, too. 156on the underlying file descriptor.
157
158Some event loops issue spurious readyness notifications, so you should
159always use non-blocking calls when reading/writing from/to your file
160handles.
129 161
130Example: 162Example:
131 163
132 # wait for readability of STDIN, then read a line and disable the watcher 164 # 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 { 165 my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
139=head2 TIME WATCHERS 171=head2 TIME WATCHERS
140 172
141You can create a time watcher by calling the C<< AnyEvent->timer >> 173You can create a time watcher by calling the C<< AnyEvent->timer >>
142method with the following mandatory arguments: 174method with the following mandatory arguments:
143 175
144C<after> after how many seconds (fractions are supported) should the timer 176C<after> specifies after how many seconds (fractional values are
145activate. C<cb> the callback to invoke. 177supported) should the timer activate. C<cb> the callback to invoke in that
178case.
146 179
147The timer callback will be invoked at most once: if you want a repeating 180The 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 181timer you have to create a new watcher (this is a limitation by both Tk
149and Glib). 182and Glib).
150 183
156 }); 189 });
157 190
158 # to cancel the timer: 191 # to cancel the timer:
159 undef $w; 192 undef $w;
160 193
194Example 2:
195
196 # fire an event after 0.5 seconds, then roughly every second
197 my $w;
198
199 my $cb = sub {
200 # cancel the old timer while creating a new one
201 $w = AnyEvent->timer (after => 1, cb => $cb);
202 };
203
204 # start the "loop" by creating the first watcher
205 $w = AnyEvent->timer (after => 0.5, cb => $cb);
206
207=head3 TIMING ISSUES
208
209There are two ways to handle timers: based on real time (relative, "fire
210in 10 seconds") and based on wallclock time (absolute, "fire at 12
211o'clock").
212
213While most event loops expect timers to specified in a relative way, they
214use absolute time internally. This makes a difference when your clock
215"jumps", for example, when ntp decides to set your clock backwards from
216the wrong date of 2014-01-01 to 2008-01-01, a watcher that is supposed to
217fire "after" a second might actually take six years to finally fire.
218
219AnyEvent cannot compensate for this. The only event loop that is conscious
220about these issues is L<EV>, which offers both relative (ev_timer, based
221on true relative time) and absolute (ev_periodic, based on wallclock time)
222timers.
223
224AnyEvent always prefers relative timers, if available, matching the
225AnyEvent API.
226
227=head2 SIGNAL WATCHERS
228
229You can watch for signals using a signal watcher, C<signal> is the signal
230I<name> without any C<SIG> prefix, C<cb> is the Perl callback to
231be invoked whenever a signal occurs.
232
233Multiple signal occurances can be clumped together into one callback
234invocation, and callback invocation will be synchronous. synchronous means
235that it might take a while until the signal gets handled by the process,
236but it is guarenteed not to interrupt any other callbacks.
237
238The main advantage of using these watchers is that you can share a signal
239between multiple watchers.
240
241This watcher might use C<%SIG>, so programs overwriting those signals
242directly will likely not work correctly.
243
244Example: exit on SIGINT
245
246 my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
247
248=head2 CHILD PROCESS WATCHERS
249
250You can also watch on a child process exit and catch its exit status.
251
252The child process is specified by the C<pid> argument (if set to C<0>, it
253watches for any child process exit). The watcher will trigger as often
254as status change for the child are received. This works by installing a
255signal handler for C<SIGCHLD>. The callback will be called with the pid
256and exit status (as returned by waitpid).
257
258Example: wait for pid 1333
259
260 my $w = AnyEvent->child (
261 pid => 1333,
262 cb => sub {
263 my ($pid, $status) = @_;
264 warn "pid $pid exited with status $status";
265 },
266 );
267
161=head2 CONDITION WATCHERS 268=head2 CONDITION VARIABLES
162 269
163Condition watchers can be created by calling the C<< AnyEvent->condvar >> 270Condition variables can be created by calling the C<< AnyEvent->condvar >>
164method without any arguments. 271method without any arguments.
165 272
166A condition watcher watches for a condition - precisely that the C<< 273A condition variable waits for a condition - precisely that the C<<
167->broadcast >> method has been called. 274->broadcast >> method has been called.
168 275
276They are very useful to signal that a condition has been fulfilled, for
277example, if you write a module that does asynchronous http requests,
278then a condition variable would be the ideal candidate to signal the
279availability of results.
280
281You can also use condition variables to block your main program until
282an event occurs - for example, you could C<< ->wait >> in your main
283program until the user clicks the Quit button in your app, which would C<<
284->broadcast >> the "quit" event.
285
169Note that condition watchers recurse into the event loop - if you have 286Note that condition variables recurse into the event loop - if you have
170two watchers that call C<< ->wait >> in a round-robbin fashion, you 287two 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 288lose. Therefore, condition variables are good to export to your caller, but
172you should avoid making a blocking wait, at least in callbacks, as this 289you should avoid making a blocking wait yourself, at least in callbacks,
173usually asks for trouble. 290as this asks for trouble.
174 291
175The watcher has only two methods: 292This object has two methods:
176 293
177=over 4 294=over 4
178 295
179=item $cv->wait 296=item $cv->wait
180 297
181Wait (blocking if necessary) until the C<< ->broadcast >> method has been 298Wait (blocking if necessary) until the C<< ->broadcast >> method has been
182called on c<$cv>, while servicing other watchers normally. 299called on c<$cv>, while servicing other watchers normally.
183 300
184Not all event models support a blocking wait - some die in that case, so
185if you are using this from a module, never require a blocking wait, but
186let the caller decide wether the call will block or not (for example,
187by coupling condition variables with some kind of request results and
188supporting callbacks so the caller knows that getting the result will not
189block, while still suppporting blockign waits if the caller so desires).
190
191You can only wait once on a condition - additional calls will return 301You can only wait once on a condition - additional calls will return
192immediately. 302immediately.
193 303
304Not all event models support a blocking wait - some die in that case
305(programs might want to do that to stay interactive), so I<if you are
306using this from a module, never require a blocking wait>, but let the
307caller decide whether the call will block or not (for example, by coupling
308condition variables with some kind of request results and supporting
309callbacks so the caller knows that getting the result will not block,
310while still suppporting blocking waits if the caller so desires).
311
312Another reason I<never> to C<< ->wait >> in a module is that you cannot
313sensibly have two C<< ->wait >>'s in parallel, as that would require
314multiple interpreters or coroutines/threads, none of which C<AnyEvent>
315can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and
316L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
317from different coroutines, however).
318
194=item $cv->broadcast 319=item $cv->broadcast
195 320
196Flag the condition as ready - a running C<< ->wait >> and all further 321Flag the condition as ready - a running C<< ->wait >> and all further
197calls to C<wait> will return after this method has been called. If nobody 322calls to C<wait> will (eventually) return after this method has been
198is waiting the broadcast will be remembered.. 323called. If nobody is waiting the broadcast will be remembered..
324
325=back
199 326
200Example: 327Example:
201 328
202 # wait till the result is ready 329 # wait till the result is ready
203 my $result_ready = AnyEvent->condvar; 330 my $result_ready = AnyEvent->condvar;
204 331
205 # do something such as adding a timer 332 # do something such as adding a timer
206 # or socket watcher the calls $result_ready->broadcast 333 # or socket watcher the calls $result_ready->broadcast
207 # when the "result" is ready. 334 # when the "result" is ready.
335 # in this case, we simply use a timer:
336 my $w = AnyEvent->timer (
337 after => 1,
338 cb => sub { $result_ready->broadcast },
339 );
208 340
341 # this "blocks" (while handling events) till the watcher
342 # calls broadcast
209 $result_ready->wait; 343 $result_ready->wait;
210 344
211=back 345=head1 GLOBAL VARIABLES AND FUNCTIONS
212
213=head2 SIGNAL WATCHERS
214
215You can listen for signals using a signal watcher, C<signal> is the signal
216I<name> without any C<SIG> prefix. Multiple signals events can be clumped
217together into one callback invocation, and callback invocation might or
218might not be asynchronous.
219
220These watchers might use C<%SIG>, so programs overwriting those signals
221directly will likely not work correctly.
222
223Example: exit on SIGINT
224
225 my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
226
227=head2 CHILD PROCESS WATCHERS
228
229You can also listen for the status of a child process specified by the
230C<pid> argument (or any child if the pid argument is 0). The watcher will
231trigger as often as status change for the child are received. This works
232by installing a signal handler for C<SIGCHLD>. The callback will be called with
233the pid and exit status (as returned by waitpid).
234
235Example: wait for pid 1333
236
237 my $w = AnyEvent->child (pid => 1333, cb => sub { warn "exit status $?" });
238
239=head1 GLOBALS
240 346
241=over 4 347=over 4
242 348
243=item $AnyEvent::MODEL 349=item $AnyEvent::MODEL
244 350
249AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>). 355AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).
250 356
251The known classes so far are: 357The known classes so far are:
252 358
253 AnyEvent::Impl::CoroEV based on Coro::EV, best choice. 359 AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
254 AnyEvent::Impl::EV based on EV (an interface to libev, also best choice).
255 AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice. 360 AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
361 AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
256 AnyEvent::Impl::Event based on Event, also second best choice :) 362 AnyEvent::Impl::Event based on Event, second best choice.
257 AnyEvent::Impl::Glib based on Glib, second-best choice. 363 AnyEvent::Impl::Glib based on Glib, third-best choice.
258 AnyEvent::Impl::Tk based on Tk, very bad choice. 364 AnyEvent::Impl::Tk based on Tk, very bad choice.
259 AnyEvent::Impl::Perl pure-perl implementation, inefficient. 365 AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
366 AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
367 AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
368 AnyEvent::Impl::POE based on POE, not generic enough for full support.
369
370There is no support for WxWidgets, as WxWidgets has no support for
371watching file handles. However, you can use WxWidgets through the
372POE Adaptor, as POE has a Wx backend that simply polls 20 times per
373second, which was considered to be too horrible to even consider for
374AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
375it's adaptor.
376
377AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
378autodetecting them.
260 379
261=item AnyEvent::detect 380=item AnyEvent::detect
262 381
263Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model if 382Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
264necessary. You should only call this function right before you would have 383if necessary. You should only call this function right before you would
265created an AnyEvent watcher anyway, that is, very late at runtime. 384have created an AnyEvent watcher anyway, that is, as late as possible at
385runtime.
266 386
267=back 387=back
268 388
269=head1 WHAT TO DO IN A MODULE 389=head1 WHAT TO DO IN A MODULE
270 390
271As a module author, you should "use AnyEvent" and call AnyEvent methods 391As a module author, you should C<use AnyEvent> and call AnyEvent methods
272freely, but you should not load a specific event module or rely on it. 392freely, but you should not load a specific event module or rely on it.
273 393
274Be careful when you create watchers in the module body - Anyevent will 394Be careful when you create watchers in the module body - AnyEvent will
275decide which event module to use as soon as the first method is called, so 395decide which event module to use as soon as the first method is called, so
276by calling AnyEvent in your module body you force the user of your module 396by calling AnyEvent in your module body you force the user of your module
277to load the event module first. 397to load the event module first.
278 398
399Never call C<< ->wait >> on a condition variable unless you I<know> that
400the C<< ->broadcast >> method has been called on it already. This is
401because it will stall the whole program, and the whole point of using
402events is to stay interactive.
403
404It is fine, however, to call C<< ->wait >> when the user of your module
405requests it (i.e. if you create a http request object ad have a method
406called C<results> that returns the results, it should call C<< ->wait >>
407freely, as the user of your module knows what she is doing. always).
408
279=head1 WHAT TO DO IN THE MAIN PROGRAM 409=head1 WHAT TO DO IN THE MAIN PROGRAM
280 410
281There will always be a single main program - the only place that should 411There will always be a single main program - the only place that should
282dictate which event model to use. 412dictate which event model to use.
283 413
284If it doesn't care, it can just "use AnyEvent" and use it itself, or not 414If it doesn't care, it can just "use AnyEvent" and use it itself, or not
285do anything special and let AnyEvent decide which implementation to chose. 415do anything special (it does not need to be event-based) and let AnyEvent
416decide which implementation to chose if some module relies on it.
286 417
287If the main program relies on a specific event model (for example, in Gtk2 418If the main program relies on a specific event model. For example, in
288programs you have to rely on either Glib or Glib::Event), you should load 419Gtk2 programs you have to rely on the Glib module. You should load the
289it before loading AnyEvent or any module that uses it, generally, as early 420event module before loading AnyEvent or any module that uses it: generally
290as possible. The reason is that modules might create watchers when they 421speaking, you should load it as early as possible. The reason is that
291are loaded, and AnyEvent will decide on the event model to use as soon as 422modules might create watchers when they are loaded, and AnyEvent will
292it creates watchers, and it might chose the wrong one unless you load the 423decide on the event model to use as soon as it creates watchers, and it
293correct one yourself. 424might chose the wrong one unless you load the correct one yourself.
294 425
295You can chose to use a rather inefficient pure-perl implementation by 426You can chose to use a rather inefficient pure-perl implementation by
296loading the C<AnyEvent::Impl::Perl> module, but letting AnyEvent chose is 427loading the C<AnyEvent::Impl::Perl> module, which gives you similar
297generally better. 428behaviour everywhere, but letting AnyEvent chose is generally better.
298 429
299=cut 430=cut
300 431
301package AnyEvent; 432package AnyEvent;
302 433
303no warnings; 434no warnings;
304use strict; 435use strict;
305 436
306use Carp; 437use Carp;
307 438
308our $VERSION = '3.0'; 439our $VERSION = '3.3';
309our $MODEL; 440our $MODEL;
310 441
311our $AUTOLOAD; 442our $AUTOLOAD;
312our @ISA; 443our @ISA;
313 444
315 446
316our @REGISTRY; 447our @REGISTRY;
317 448
318my @models = ( 449my @models = (
319 [Coro::EV:: => AnyEvent::Impl::CoroEV::], 450 [Coro::EV:: => AnyEvent::Impl::CoroEV::],
451 [Coro::Event:: => AnyEvent::Impl::CoroEvent::],
320 [EV:: => AnyEvent::Impl::EV::], 452 [EV:: => AnyEvent::Impl::EV::],
321 [Coro::Event:: => AnyEvent::Impl::CoroEvent::],
322 [Event:: => AnyEvent::Impl::Event::], 453 [Event:: => AnyEvent::Impl::Event::],
323 [Glib:: => AnyEvent::Impl::Glib::], 454 [Glib:: => AnyEvent::Impl::Glib::],
324 [Tk:: => AnyEvent::Impl::Tk::], 455 [Tk:: => AnyEvent::Impl::Tk::],
456 [Wx:: => AnyEvent::Impl::POE::],
457 [Prima:: => AnyEvent::Impl::POE::],
325 [AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::], 458 [AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
459 # everything below here will not be autoprobed as the pureperl backend should work everywhere
460 [Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
461 [Qt:: => AnyEvent::Impl::Qt::], # requires special main program
462 [POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
326); 463);
327 464
328our %method = map +($_ => 1), qw(io timer condvar broadcast wait signal one_event DESTROY); 465our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY);
329 466
330sub detect() { 467sub detect() {
331 unless ($MODEL) { 468 unless ($MODEL) {
332 no strict 'refs'; 469 no strict 'refs';
333 470
471 if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
472 my $model = "AnyEvent::Impl::$1";
473 if (eval "require $model") {
474 $MODEL = $model;
475 warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;
476 } else {
477 warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;
478 }
479 }
480
334 # check for already loaded models 481 # check for already loaded models
482 unless ($MODEL) {
335 for (@REGISTRY, @models) { 483 for (@REGISTRY, @models) {
336 my ($package, $model) = @$_; 484 my ($package, $model) = @$_;
337 if (${"$package\::VERSION"} > 0) { 485 if (${"$package\::VERSION"} > 0) {
338 if (eval "require $model") { 486 if (eval "require $model") {
339 $MODEL = $model; 487 $MODEL = $model;
340 warn "AnyEvent: found model '$model', using it.\n" if $verbose > 1; 488 warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;
341 last; 489 last;
490 }
342 } 491 }
343 } 492 }
344 }
345 493
346 unless ($MODEL) { 494 unless ($MODEL) {
347 # try to load a model 495 # try to load a model
348 496
349 for (@REGISTRY, @models) { 497 for (@REGISTRY, @models) {
350 my ($package, $model) = @$_; 498 my ($package, $model) = @$_;
351 if (eval "require $package" 499 if (eval "require $package"
352 and ${"$package\::VERSION"} > 0 500 and ${"$package\::VERSION"} > 0
353 and eval "require $model") { 501 and eval "require $model") {
354 $MODEL = $model; 502 $MODEL = $model;
355 warn "AnyEvent: autoprobed and loaded model '$model', using it.\n" if $verbose > 1; 503 warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;
356 last; 504 last;
505 }
357 } 506 }
507
508 $MODEL
509 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.";
358 } 510 }
359
360 $MODEL
361 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.";
362 } 511 }
363 512
364 unshift @ISA, $MODEL; 513 unshift @ISA, $MODEL;
365 push @{"$MODEL\::ISA"}, "AnyEvent::Base"; 514 push @{"$MODEL\::ISA"}, "AnyEvent::Base";
366 } 515 }
477 undef $CHLD_W unless keys %PID_CB; 626 undef $CHLD_W unless keys %PID_CB;
478} 627}
479 628
480=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE 629=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
481 630
631This is an advanced topic that you do not normally need to use AnyEvent in
632a module. This section is only of use to event loop authors who want to
633provide AnyEvent compatibility.
634
482If you need to support another event library which isn't directly 635If you need to support another event library which isn't directly
483supported by AnyEvent, you can supply your own interface to it by 636supported by AnyEvent, you can supply your own interface to it by
484pushing, before the first watcher gets created, the package name of 637pushing, before the first watcher gets created, the package name of
485the event module and the package name of the interface to use onto 638the event module and the package name of the interface to use onto
486C<@AnyEvent::REGISTRY>. You can do that before and even without loading 639C<@AnyEvent::REGISTRY>. You can do that before and even without loading
487AnyEvent. 640AnyEvent, so it is reasonably cheap.
488 641
489Example: 642Example:
490 643
491 push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::]; 644 push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];
492 645
493This tells AnyEvent to (literally) use the C<urxvt::anyevent::> 646This tells AnyEvent to (literally) use the C<urxvt::anyevent::>
494package/class when it finds the C<urxvt> package/module is loaded. When 647package/class when it finds the C<urxvt> package/module is already loaded.
648
495AnyEvent is loaded and asked to find a suitable event model, it will 649When AnyEvent is loaded and asked to find a suitable event model, it
496first check for the presence of urxvt. 650will first check for the presence of urxvt by trying to C<use> the
651C<urxvt::anyevent> module.
497 652
498The class should provide implementations for all watcher types (see 653The class should provide implementations for all watcher types. See
499L<AnyEvent::Impl::Event> (source code), L<AnyEvent::Impl::Glib> 654L<AnyEvent::Impl::EV> (source code), L<AnyEvent::Impl::Glib> (Source code)
500(Source code) and so on for actual examples, use C<perldoc -m 655and so on for actual examples. Use C<perldoc -m AnyEvent::Impl::Glib> to
501AnyEvent::Impl::Glib> to see the sources). 656see the sources.
502 657
658If you don't provide C<signal> and C<child> watchers than AnyEvent will
659provide suitable (hopefully) replacements.
660
503The above isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt) 661The above example isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt)
504uses the above line as-is. An interface isn't included in AnyEvent 662terminal emulator uses the above line as-is. An interface isn't included
505because it doesn't make sense outside the embedded interpreter inside 663in AnyEvent because it doesn't make sense outside the embedded interpreter
506I<rxvt-unicode>, and it is updated and maintained as part of the 664inside I<rxvt-unicode>, and it is updated and maintained as part of the
507I<rxvt-unicode> distribution. 665I<rxvt-unicode> distribution.
508 666
509I<rxvt-unicode> also cheats a bit by not providing blocking access to 667I<rxvt-unicode> also cheats a bit by not providing blocking access to
510condition variables: code blocking while waiting for a condition will 668condition variables: code blocking while waiting for a condition will
511C<die>. This still works with most modules/usages, and blocking calls must 669C<die>. This still works with most modules/usages, and blocking calls must
512not be in an interactive application, so it makes sense. 670not be done in an interactive application, so it makes sense.
513 671
514=head1 ENVIRONMENT VARIABLES 672=head1 ENVIRONMENT VARIABLES
515 673
516The following environment variables are used by this module: 674The following environment variables are used by this module:
517 675
518C<PERL_ANYEVENT_VERBOSE> when set to C<2> or higher, reports which event 676=over 4
519model gets used.
520 677
678=item C<PERL_ANYEVENT_VERBOSE>
679
680By default, AnyEvent will be completely silent except in fatal
681conditions. You can set this environment variable to make AnyEvent more
682talkative.
683
684When set to C<1> or higher, causes AnyEvent to warn about unexpected
685conditions, such as not being able to load the event model specified by
686C<PERL_ANYEVENT_MODEL>.
687
688When set to C<2> or higher, cause AnyEvent to report to STDERR which event
689model it chooses.
690
691=item C<PERL_ANYEVENT_MODEL>
692
693This can be used to specify the event model to be used by AnyEvent, before
694autodetection and -probing kicks in. It must be a string consisting
695entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
696and the resulting module name is loaded and if the load was successful,
697used as event model. If it fails to load AnyEvent will proceed with
698autodetection and -probing.
699
700This functionality might change in future versions.
701
702For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
703could start your program like this:
704
705 PERL_ANYEVENT_MODEL=Perl perl ...
706
707=back
708
521=head1 EXAMPLE 709=head1 EXAMPLE PROGRAM
522 710
523The following program uses an io watcher to read data from stdin, a timer 711The following program uses an I/O watcher to read data from STDIN, a timer
524to display a message once per second, and a condvar to exit the program 712to display a message once per second, and a condition variable to quit the
525when the user enters quit: 713program when the user enters quit:
526 714
527 use AnyEvent; 715 use AnyEvent;
528 716
529 my $cv = AnyEvent->condvar; 717 my $cv = AnyEvent->condvar;
530 718
531 my $io_watcher = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub { 719 my $io_watcher = AnyEvent->io (
720 fh => \*STDIN,
721 poll => 'r',
722 cb => sub {
532 warn "io event <$_[0]>\n"; # will always output <r> 723 warn "io event <$_[0]>\n"; # will always output <r>
533 chomp (my $input = <STDIN>); # read a line 724 chomp (my $input = <STDIN>); # read a line
534 warn "read: $input\n"; # output what has been read 725 warn "read: $input\n"; # output what has been read
535 $cv->broadcast if $input =~ /^q/i; # quit program if /^q/i 726 $cv->broadcast if $input =~ /^q/i; # quit program if /^q/i
727 },
536 }); 728 );
537 729
538 my $time_watcher; # can only be used once 730 my $time_watcher; # can only be used once
539 731
540 sub new_timer { 732 sub new_timer {
541 $timer = AnyEvent->timer (after => 1, cb => sub { 733 $timer = AnyEvent->timer (after => 1, cb => sub {
623 $txn->{finished}->wait; 815 $txn->{finished}->wait;
624 return $txn->{result}; 816 return $txn->{result};
625 817
626The actual code goes further and collects all errors (C<die>s, exceptions) 818The actual code goes further and collects all errors (C<die>s, exceptions)
627that occured during request processing. The C<result> method detects 819that occured during request processing. The C<result> method detects
628wether an exception as thrown (it is stored inside the $txn object) 820whether an exception as thrown (it is stored inside the $txn object)
629and just throws the exception, which means connection errors and other 821and just throws the exception, which means connection errors and other
630problems get reported tot he code that tries to use the result, not in a 822problems get reported tot he code that tries to use the result, not in a
631random callback. 823random callback.
632 824
633All of this enables the following usage styles: 825All of this enables the following usage styles:
634 826
6351. Blocking: 8271. Blocking:
636 828
637 my $data = $fcp->client_get ($url); 829 my $data = $fcp->client_get ($url);
638 830
6392. Blocking, but parallelizing: 8312. Blocking, but running in parallel:
640 832
641 my @datas = map $_->result, 833 my @datas = map $_->result,
642 map $fcp->txn_client_get ($_), 834 map $fcp->txn_client_get ($_),
643 @urls; 835 @urls;
644 836
645Both blocking examples work without the module user having to know 837Both blocking examples work without the module user having to know
646anything about events. 838anything about events.
647 839
6483a. Event-based in a main program, using any support Event module: 8403a. Event-based in a main program, using any supported event module:
649 841
650 use Event; 842 use EV;
651 843
652 $fcp->txn_client_get ($url)->cb (sub { 844 $fcp->txn_client_get ($url)->cb (sub {
653 my $txn = shift; 845 my $txn = shift;
654 my $data = $txn->result; 846 my $data = $txn->result;
655 ... 847 ...
656 }); 848 });
657 849
658 Event::loop; 850 EV::loop;
659 851
6603b. The module user could use AnyEvent, too: 8523b. The module user could use AnyEvent, too:
661 853
662 use AnyEvent; 854 use AnyEvent;
663 855
668 $quit->broadcast; 860 $quit->broadcast;
669 }); 861 });
670 862
671 $quit->wait; 863 $quit->wait;
672 864
865
866=head1 BENCHMARK
867
868To give you an idea of the performance and overheads that AnyEvent adds
869over the event loops themselves (and to give you an impression of the
870speed of various event loops), here is a benchmark of various supported
871event models natively and with anyevent. The benchmark creates a lot of
872timers (with a zero timeout) and I/O watchers (watching STDOUT, a pty, to
873become writable, which it is), lets them fire exactly once and destroys
874them again.
875
876Rewriting the benchmark to use many different sockets instead of using
877the same filehandle for all I/O watchers results in a much longer runtime
878(socket creation is expensive), but qualitatively the same figures, so it
879was not used.
880
881=head2 Explanation of the columns
882
883I<watcher> is the number of event watchers created/destroyed. Since
884different event models feature vastly different performances, each event
885loop was given a number of watchers so that overall runtime is acceptable
886and similar between tested event loop (and keep them from crashing): Glib
887would probably take thousands of years if asked to process the same number
888of watchers as EV in this benchmark.
889
890I<bytes> is the number of bytes (as measured by the resident set size,
891RSS) consumed by each watcher. This method of measuring captures both C
892and Perl-based overheads.
893
894I<create> is the time, in microseconds (millionths of seconds), that it
895takes to create a single watcher. The callback is a closure shared between
896all watchers, to avoid adding memory overhead. That means closure creation
897and memory usage is not included in the figures.
898
899I<invoke> is the time, in microseconds, used to invoke a simple
900callback. The callback simply counts down a Perl variable and after it was
901invoked "watcher" times, it would C<< ->broadcast >> a condvar once to
902signal the end of this phase.
903
904I<destroy> is the time, in microseconds, that it takes to destroy a single
905watcher.
906
907=head2 Results
908
909 name watchers bytes create invoke destroy comment
910 EV/EV 400000 244 0.56 0.46 0.31 EV native interface
911 EV/Any 100000 610 3.52 0.91 0.75 EV + AnyEvent watchers
912 CoroEV/Any 100000 610 3.49 0.92 0.75 coroutines + Coro::Signal
913 Perl/Any 100000 513 4.91 0.92 1.15 pure perl implementation
914 Event/Event 16000 523 28.05 21.38 0.86 Event native interface
915 Event/Any 16000 943 34.43 20.48 1.39 Event + AnyEvent watchers
916 Glib/Any 16000 1357 96.99 12.55 55.51 quadratic behaviour
917 Tk/Any 2000 1855 27.01 66.61 14.03 SEGV with >> 2000 watchers
918 POE/Event 2000 6644 108.15 768.19 14.33 via POE::Loop::Event
919 POE/Select 2000 6343 94.69 807.65 562.69 via POE::Loop::Select
920
921=head2 Discussion
922
923The benchmark does I<not> measure scalability of the event loop very
924well. For example, a select-based event loop (such as the pure perl one)
925can never compete with an event loop that uses epoll when the number of
926file descriptors grows high. In this benchmark, all events become ready at
927the same time, so select/poll-based implementations get an unnatural speed
928boost.
929
930C<EV> is the sole leader regarding speed and memory use, which are both
931maximal/minimal, respectively. Even when going through AnyEvent, there are
932only two event loops that use slightly less memory (the C<Event> module
933natively and the pure perl backend), and no faster event models, not even
934C<Event> natively.
935
936The pure perl implementation is hit in a few sweet spots (both the
937zero timeout and the use of a single fd hit optimisations in the perl
938interpreter and the backend itself, and all watchers become ready at the
939same time). Nevertheless this shows that it adds very little overhead in
940itself. Like any select-based backend its performance becomes really bad
941with lots of file descriptors (and few of them active), of course, but
942this was not subject of this benchmark.
943
944The C<Event> module has a relatively high setup and callback invocation cost,
945but overall scores on the third place.
946
947C<Glib>'s memory usage is quite a bit bit higher, but it features a
948faster callback invocation and overall ends up in the same class as
949C<Event>. However, Glib scales extremely badly, doubling the number of
950watchers increases the processing time by more than a factor of four,
951making it completely unusable when using larger numbers of watchers
952(note that only a single file descriptor was used in the benchmark, so
953inefficiencies of C<poll> do not account for this).
954
955The C<Tk> adaptor works relatively well. The fact that it crashes with
956more than 2000 watchers is a big setback, however, as correctness takes
957precedence over speed. Nevertheless, its performance is surprising, as the
958file descriptor is dup()ed for each watcher. This shows that the dup()
959employed by some adaptors is not a big performance issue (it does incur a
960hidden memory cost inside the kernel, though, that is not reflected in the
961figures above).
962
963C<POE>, regardless of underlying event loop (wether using its pure perl
964select-based backend or the Event module) shows abysmal performance and
965memory usage: Watchers use almost 30 times as much memory as EV watchers,
966and 10 times as much memory as both Event or EV via AnyEvent. Watcher
967invocation is almost 900 times slower than with AnyEvent's pure perl
968implementation. The design of the POE adaptor class in AnyEvent can not
969really account for this, as session creation overhead is small compared
970to execution of the state machine, which is coded pretty optimally within
971L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow.
972
973=head2 Summary
974
975Using EV through AnyEvent is faster than any other event loop, but most
976event loops have acceptable performance with or without AnyEvent.
977
978The overhead AnyEvent adds is usually much smaller than the overhead of
979the actual event loop, only with extremely fast event loops such as the EV
980adds AnyEvent significant overhead.
981
982And you should simply avoid POE like the plague if you want performance or
983reasonable memory usage.
984
985
986=head1 FORK
987
988Most event libraries are not fork-safe. The ones who are usually are
989because they are so inefficient. Only L<EV> is fully fork-aware.
990
991If you have to fork, you must either do so I<before> creating your first
992watcher OR you must not use AnyEvent at all in the child.
993
994
995=head1 SECURITY CONSIDERATIONS
996
997AnyEvent can be forced to load any event model via
998$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to
999execute arbitrary code or directly gain access, it can easily be used to
1000make the program hang or malfunction in subtle ways, as AnyEvent watchers
1001will not be active when the program uses a different event model than
1002specified in the variable.
1003
1004You can make AnyEvent completely ignore this variable by deleting it
1005before the first watcher gets created, e.g. with a C<BEGIN> block:
1006
1007 BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1008
1009 use AnyEvent;
1010
1011
673=head1 SEE ALSO 1012=head1 SEE ALSO
674 1013
675Event modules: L<Coro::Event>, L<Coro>, L<Event>, L<Glib::Event>, L<Glib>. 1014Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,
1015L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,
1016L<Event::Lib>, L<Qt>, L<POE>.
676 1017
1018Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,
677Implementations: L<AnyEvent::Impl::Coro>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>. 1019L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,
1020L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,
1021L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>.
678 1022
679Nontrivial usage example: L<Net::FCP>. 1023Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.
680 1024
681=head1 1025
1026=head1 AUTHOR
1027
1028 Marc Lehmann <schmorp@schmorp.de>
1029 http://home.schmorp.de/
682 1030
683=cut 1031=cut
684 1032
6851 10331
686 1034

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