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Revision 1.55 by root, Wed Apr 23 11:25:42 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 - 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 23=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
24 24
25Glib, POE, IO::Async, Event... CPAN offers event models by the dozen 25Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
26nowadays. So what is different about AnyEvent? 26nowadays. So what is different about AnyEvent?
27 27
28Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of 28Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of
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 (the latter of which is actually 44For modules like POE or IO::Async (which is a total misnomer as it is
44named confusingly, as it does neither do I/O nor does it do anything 45actually doing all I/O I<synchronously>...), using them in your module is
45asynchronously...), using them in your module is like joining a
46cult: 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
47anything else, as it is simply incompatible to everything that isn't 47cannot use anything else, as it is simply incompatible to everything that
48itself. 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.
49 50
50AnyEvent + POE works fine. AnyEvent + Glib works fine. AnyEvent + Tk 51AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
51works 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
52+ 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
53those, 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,
54uses AnyEvent, it works transparently with all event models it supports 55too. But if your module uses AnyEvent, it works transparently with all
55(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).
56 59
57In 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
58model>, 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
59modules, 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
60to 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
61offering 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
62technically possible. 65technically possible.
66
67Of course, if you want lots of policy (this can arguably be somewhat
68useful) and you want to force your users to use the one and only event
69model, you should I<not> use this module.
63 70
64 71
65=head1 DESCRIPTION 72=head1 DESCRIPTION
66 73
67L<AnyEvent> provides an identical interface to multiple event loops. This 74L<AnyEvent> provides an identical interface to multiple event loops. This
68allows module authors to utilise an event loop without forcing module 75allows module authors to utilise an event loop without forcing module
69users 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
70peacefully at any one time). 77peacefully at any one time).
71 78
72The interface itself is vaguely similar but not identical to the Event 79The interface itself is vaguely similar, but not identical to the L<Event>
73module. 80module.
74 81
75On 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
76loaded event loop by probing wether any of the following modules is 83to detect the currently loaded event loop by probing whether one of the
77loaded: 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>,
78used. If none is found, the module tries to load these modules in the 85L<Event>, L<Glib>, L<Tk>. The first one found is used. If none are found,
79order given. The first one that could be successfully loaded will be 86the module tries to load these modules in the stated order. The first one
80used. If still none could be found, AnyEvent will fall back to a pure-perl 87that can be successfully loaded will be used. If, after this, still none
81event loop, which is also not very efficient. 88could be found, AnyEvent will fall back to a pure-perl event loop, which
89is not very efficient, but should work everywhere.
82 90
83Because AnyEvent first checks for modules that are already loaded, loading 91Because AnyEvent first checks for modules that are already loaded, loading
84an Event model explicitly before first using AnyEvent will likely make 92an event model explicitly before first using AnyEvent will likely make
85that model the default. For example: 93that model the default. For example:
86 94
87 use Tk; 95 use Tk;
88 use AnyEvent; 96 use AnyEvent;
89 97
90 # .. AnyEvent will likely default to Tk 98 # .. AnyEvent will likely default to Tk
99
100The I<likely> means that, if any module loads another event model and
101starts using it, all bets are off. Maybe you should tell their authors to
102use AnyEvent so their modules work together with others seamlessly...
91 103
92The pure-perl implementation of AnyEvent is called 104The pure-perl implementation of AnyEvent is called
93C<AnyEvent::Impl::Perl>. Like other event modules you can load it 105C<AnyEvent::Impl::Perl>. Like other event modules you can load it
94explicitly. 106explicitly.
95 107
… …
98AnyEvent has the central concept of a I<watcher>, which is an object that 110AnyEvent has the central concept of a I<watcher>, which is an object that
99stores relevant data for each kind of event you are waiting for, such as 111stores relevant data for each kind of event you are waiting for, such as
100the callback to call, the filehandle to watch, etc. 112the callback to call, the filehandle to watch, etc.
101 113
102These watchers are normal Perl objects with normal Perl lifetime. After 114These watchers are normal Perl objects with normal Perl lifetime. After
103creating a watcher it will immediately "watch" for events and invoke 115creating a watcher it will immediately "watch" for events and invoke the
116callback when the event occurs (of course, only when the event model
117is in control).
118
104the callback. To disable the watcher you have to destroy it (e.g. by 119To disable the watcher you have to destroy it (e.g. by setting the
105setting the variable that stores it to C<undef> or otherwise deleting all 120variable you store it in to C<undef> or otherwise deleting all references
106references to it). 121to it).
107 122
108All watchers are created by calling a method on the C<AnyEvent> class. 123All watchers are created by calling a method on the C<AnyEvent> class.
109 124
125Many watchers either are used with "recursion" (repeating timers for
126example), or need to refer to their watcher object in other ways.
127
128An any way to achieve that is this pattern:
129
130 my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
131 # you can use $w here, for example to undef it
132 undef $w;
133 });
134
135Note that C<my $w; $w => combination. This is necessary because in Perl,
136my variables are only visible after the statement in which they are
137declared.
138
110=head2 IO WATCHERS 139=head2 IO WATCHERS
111 140
112You can create I/O watcher by calling the C<< AnyEvent->io >> method with 141You can create an I/O watcher by calling the C<< AnyEvent->io >> method
113the following mandatory arguments: 142with the following mandatory key-value pairs as arguments:
114 143
115C<fh> the Perl I<filehandle> (not filedescriptor) to watch for 144C<fh> the Perl I<file handle> (I<not> file descriptor) to watch for
116events. C<poll> must be a string that is either C<r> or C<w>, that creates 145events. C<poll> must be a string that is either C<r> or C<w>, which
117a watcher waiting for "r"eadable or "w"ritable events. C<cb> the callback 146creates a watcher waiting for "r"eadable or "w"ritable events,
118to invoke everytime the filehandle becomes ready. 147respectively. C<cb> is the callback to invoke each time the file handle
148becomes ready.
119 149
120Only one io watcher per C<fh> and C<poll> combination is allowed (i.e. on
121a socket you can have one r + one w, not any more (limitation comes from
122Tk - if you are sure you are not using Tk this limitation is gone).
123
124Filehandles will be kept alive, so as long as the watcher exists, the 150File handles will be kept alive, so as long as the watcher exists, the
125filehandle exists, too. 151file handle exists, too.
152
153It is not allowed to close a file handle as long as any watcher is active
154on the underlying file descriptor.
155
156Some event loops issue spurious readyness notifications, so you should
157always use non-blocking calls when reading/writing from/to your file
158handles.
126 159
127Example: 160Example:
128 161
129 # wait for readability of STDIN, then read a line and disable the watcher 162 # wait for readability of STDIN, then read a line and disable the watcher
130 my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub { 163 my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
… …
136=head2 TIME WATCHERS 169=head2 TIME WATCHERS
137 170
138You can create a time watcher by calling the C<< AnyEvent->timer >> 171You can create a time watcher by calling the C<< AnyEvent->timer >>
139method with the following mandatory arguments: 172method with the following mandatory arguments:
140 173
141C<after> after how many seconds (fractions are supported) should the timer 174C<after> specifies after how many seconds (fractional values are
142activate. C<cb> the callback to invoke. 175supported) should the timer activate. C<cb> the callback to invoke in that
176case.
143 177
144The timer callback will be invoked at most once: if you want a repeating 178The timer callback will be invoked at most once: if you want a repeating
145timer you have to create a new watcher (this is a limitation by both Tk 179timer you have to create a new watcher (this is a limitation by both Tk
146and Glib). 180and Glib).
147 181
… …
153 }); 187 });
154 188
155 # to cancel the timer: 189 # to cancel the timer:
156 undef $w; 190 undef $w;
157 191
192Example 2:
193
194 # fire an event after 0.5 seconds, then roughly every second
195 my $w;
196
197 my $cb = sub {
198 # cancel the old timer while creating a new one
199 $w = AnyEvent->timer (after => 1, cb => $cb);
200 };
201
202 # start the "loop" by creating the first watcher
203 $w = AnyEvent->timer (after => 0.5, cb => $cb);
204
205=head3 TIMING ISSUES
206
207There are two ways to handle timers: based on real time (relative, "fire
208in 10 seconds") and based on wallclock time (absolute, "fire at 12
209o'clock").
210
211While most event loops expect timers to specified in a relative way, they use
212absolute time internally. This makes a difference when your clock "jumps",
213for example, when ntp decides to set your clock backwards from the wrong 2014-01-01 to
2142008-01-01, a watcher that you created to fire "after" a second might actually take
215six years to finally fire.
216
217AnyEvent cannot compensate for this. The only event loop that is conscious
218about these issues is L<EV>, which offers both relative (ev_timer) and
219absolute (ev_periodic) timers.
220
221AnyEvent always prefers relative timers, if available, matching the
222AnyEvent API.
223
224=head2 SIGNAL WATCHERS
225
226You can watch for signals using a signal watcher, C<signal> is the signal
227I<name> without any C<SIG> prefix, C<cb> is the Perl callback to
228be invoked whenever a signal occurs.
229
230Multiple signals occurances can be clumped together into one callback
231invocation, and callback invocation will be synchronous. synchronous means
232that it might take a while until the signal gets handled by the process,
233but it is guarenteed not to interrupt any other callbacks.
234
235The main advantage of using these watchers is that you can share a signal
236between multiple watchers.
237
238This watcher might use C<%SIG>, so programs overwriting those signals
239directly will likely not work correctly.
240
241Example: exit on SIGINT
242
243 my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
244
245=head2 CHILD PROCESS WATCHERS
246
247You can also watch on a child process exit and catch its exit status.
248
249The child process is specified by the C<pid> argument (if set to C<0>, it
250watches for any child process exit). The watcher will trigger as often
251as status change for the child are received. This works by installing a
252signal handler for C<SIGCHLD>. The callback will be called with the pid
253and exit status (as returned by waitpid).
254
255Example: wait for pid 1333
256
257 my $w = AnyEvent->child (
258 pid => 1333,
259 cb => sub {
260 my ($pid, $status) = @_;
261 warn "pid $pid exited with status $status";
262 },
263 );
264
158=head2 CONDITION WATCHERS 265=head2 CONDITION VARIABLES
159 266
160Condition watchers can be created by calling the C<< AnyEvent->condvar >> 267Condition variables can be created by calling the C<< AnyEvent->condvar >>
161method without any arguments. 268method without any arguments.
162 269
163A condition watcher watches for a condition - precisely that the C<< 270A condition variable waits for a condition - precisely that the C<<
164->broadcast >> method has been called. 271->broadcast >> method has been called.
165 272
273They are very useful to signal that a condition has been fulfilled, for
274example, if you write a module that does asynchronous http requests,
275then a condition variable would be the ideal candidate to signal the
276availability of results.
277
278You can also use condition variables to block your main program until
279an event occurs - for example, you could C<< ->wait >> in your main
280program until the user clicks the Quit button in your app, which would C<<
281->broadcast >> the "quit" event.
282
166Note that condition watchers recurse into the event loop - if you have 283Note that condition variables recurse into the event loop - if you have
167two watchers that call C<< ->wait >> in a round-robbin fashion, you 284two pirces of code that call C<< ->wait >> in a round-robbin fashion, you
168lose. Therefore, condition watchers are good to export to your caller, but 285lose. Therefore, condition variables are good to export to your caller, but
169you should avoid making a blocking wait, at least in callbacks, as this 286you should avoid making a blocking wait yourself, at least in callbacks,
170usually asks for trouble. 287as this asks for trouble.
171 288
172The watcher has only two methods: 289This object has two methods:
173 290
174=over 4 291=over 4
175 292
176=item $cv->wait 293=item $cv->wait
177 294
178Wait (blocking if necessary) until the C<< ->broadcast >> method has been 295Wait (blocking if necessary) until the C<< ->broadcast >> method has been
179called on c<$cv>, while servicing other watchers normally. 296called on c<$cv>, while servicing other watchers normally.
180 297
181Not all event models support a blocking wait - some die in that case, so
182if you are using this from a module, never require a blocking wait, but
183let the caller decide wether the call will block or not (for example,
184by coupling condition variables with some kind of request results and
185supporting callbacks so the caller knows that getting the result will not
186block, while still suppporting blockign waits if the caller so desires).
187
188You can only wait once on a condition - additional calls will return 298You can only wait once on a condition - additional calls will return
189immediately. 299immediately.
190 300
301Not all event models support a blocking wait - some die in that case
302(programs might want to do that to stay interactive), so I<if you are
303using this from a module, never require a blocking wait>, but let the
304caller decide whether the call will block or not (for example, by coupling
305condition variables with some kind of request results and supporting
306callbacks so the caller knows that getting the result will not block,
307while still suppporting blocking waits if the caller so desires).
308
309Another reason I<never> to C<< ->wait >> in a module is that you cannot
310sensibly have two C<< ->wait >>'s in parallel, as that would require
311multiple interpreters or coroutines/threads, none of which C<AnyEvent>
312can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and
313L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
314from different coroutines, however).
315
191=item $cv->broadcast 316=item $cv->broadcast
192 317
193Flag the condition as ready - a running C<< ->wait >> and all further 318Flag the condition as ready - a running C<< ->wait >> and all further
194calls to C<wait> will return after this method has been called. If nobody 319calls to C<wait> will (eventually) return after this method has been
195is waiting the broadcast will be remembered.. 320called. If nobody is waiting the broadcast will be remembered..
321
322=back
196 323
197Example: 324Example:
198 325
199 # wait till the result is ready 326 # wait till the result is ready
200 my $result_ready = AnyEvent->condvar; 327 my $result_ready = AnyEvent->condvar;
201 328
202 # do something such as adding a timer 329 # do something such as adding a timer
203 # or socket watcher the calls $result_ready->broadcast 330 # or socket watcher the calls $result_ready->broadcast
204 # when the "result" is ready. 331 # when the "result" is ready.
332 # in this case, we simply use a timer:
333 my $w = AnyEvent->timer (
334 after => 1,
335 cb => sub { $result_ready->broadcast },
336 );
205 337
338 # this "blocks" (while handling events) till the watcher
339 # calls broadcast
206 $result_ready->wait; 340 $result_ready->wait;
207 341
208=back 342=head1 GLOBAL VARIABLES AND FUNCTIONS
209
210=head2 SIGNAL WATCHERS
211
212You can listen for signals using a signal watcher, C<signal> is the signal
213I<name> without any C<SIG> prefix. Multiple signals events can be clumped
214together into one callback invocation, and callback invocation might or
215might not be asynchronous.
216
217These watchers might use C<%SIG>, so programs overwriting those signals
218directly will likely not work correctly.
219
220Example: exit on SIGINT
221
222 my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
223
224=head2 CHILD PROCESS WATCHERS
225
226You can also listen for the status of a child process specified by the
227C<pid> argument (or any child if the pid argument is 0). The watcher will
228trigger as often as status change for the child are received. This works
229by installing a signal handler for C<SIGCHLD>. The callback will be called with
230the pid and exit status (as returned by waitpid).
231
232Example: wait for pid 1333
233
234 my $w = AnyEvent->child (pid => 1333, cb => sub { warn "exit status $?" });
235
236=head1 GLOBALS
237 343
238=over 4 344=over 4
239 345
240=item $AnyEvent::MODEL 346=item $AnyEvent::MODEL
241 347
… …
246AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>). 352AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).
247 353
248The known classes so far are: 354The known classes so far are:
249 355
250 AnyEvent::Impl::CoroEV based on Coro::EV, best choice. 356 AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
357 AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
251 AnyEvent::Impl::EV based on EV (an interface to libev, also best choice). 358 AnyEvent::Impl::EV based on EV (an interface to libev, also best choice).
252 AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
253 AnyEvent::Impl::Event based on Event, also second best choice :) 359 AnyEvent::Impl::Event based on Event, also second best choice :)
254 AnyEvent::Impl::Glib based on Glib, second-best choice. 360 AnyEvent::Impl::Glib based on Glib, third-best choice.
255 AnyEvent::Impl::Tk based on Tk, very bad choice. 361 AnyEvent::Impl::Tk based on Tk, very bad choice.
256 AnyEvent::Impl::Perl pure-perl implementation, inefficient. 362 AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
363 AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
257 364
258=item AnyEvent::detect 365=item AnyEvent::detect
259 366
260Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model if 367Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
261necessary. You should only call this function right before you would have 368if necessary. You should only call this function right before you would
262created an AnyEvent watcher anyway, that is, very late at runtime. 369have created an AnyEvent watcher anyway, that is, as late as possible at
370runtime.
263 371
264=back 372=back
265 373
266=head1 WHAT TO DO IN A MODULE 374=head1 WHAT TO DO IN A MODULE
267 375
268As a module author, you should "use AnyEvent" and call AnyEvent methods 376As a module author, you should C<use AnyEvent> and call AnyEvent methods
269freely, but you should not load a specific event module or rely on it. 377freely, but you should not load a specific event module or rely on it.
270 378
271Be careful when you create watchers in the module body - Anyevent will 379Be careful when you create watchers in the module body - AnyEvent will
272decide which event module to use as soon as the first method is called, so 380decide which event module to use as soon as the first method is called, so
273by calling AnyEvent in your module body you force the user of your module 381by calling AnyEvent in your module body you force the user of your module
274to load the event module first. 382to load the event module first.
275 383
384Never call C<< ->wait >> on a condition variable unless you I<know> that
385the C<< ->broadcast >> method has been called on it already. This is
386because it will stall the whole program, and the whole point of using
387events is to stay interactive.
388
389It is fine, however, to call C<< ->wait >> when the user of your module
390requests it (i.e. if you create a http request object ad have a method
391called C<results> that returns the results, it should call C<< ->wait >>
392freely, as the user of your module knows what she is doing. always).
393
276=head1 WHAT TO DO IN THE MAIN PROGRAM 394=head1 WHAT TO DO IN THE MAIN PROGRAM
277 395
278There will always be a single main program - the only place that should 396There will always be a single main program - the only place that should
279dictate which event model to use. 397dictate which event model to use.
280 398
281If it doesn't care, it can just "use AnyEvent" and use it itself, or not 399If it doesn't care, it can just "use AnyEvent" and use it itself, or not
282do anything special and let AnyEvent decide which implementation to chose. 400do anything special (it does not need to be event-based) and let AnyEvent
401decide which implementation to chose if some module relies on it.
283 402
284If the main program relies on a specific event model (for example, in Gtk2 403If the main program relies on a specific event model. For example, in
285programs you have to rely on either Glib or Glib::Event), you should load 404Gtk2 programs you have to rely on the Glib module. You should load the
286it before loading AnyEvent or any module that uses it, generally, as early 405event module before loading AnyEvent or any module that uses it: generally
287as possible. The reason is that modules might create watchers when they 406speaking, you should load it as early as possible. The reason is that
288are loaded, and AnyEvent will decide on the event model to use as soon as 407modules might create watchers when they are loaded, and AnyEvent will
289it creates watchers, and it might chose the wrong one unless you load the 408decide on the event model to use as soon as it creates watchers, and it
290correct one yourself. 409might chose the wrong one unless you load the correct one yourself.
291 410
292You can chose to use a rather inefficient pure-perl implementation by 411You can chose to use a rather inefficient pure-perl implementation by
293loading the C<AnyEvent::Impl::Perl> module, but letting AnyEvent chose is 412loading the C<AnyEvent::Impl::Perl> module, which gives you similar
294generally better. 413behaviour everywhere, but letting AnyEvent chose is generally better.
295 414
296=cut 415=cut
297 416
298package AnyEvent; 417package AnyEvent;
299 418
300no warnings; 419no warnings;
301use strict; 420use strict;
302 421
303use Carp; 422use Carp;
304 423
305our $VERSION = '3.0'; 424our $VERSION = '3.12';
306our $MODEL; 425our $MODEL;
307 426
308our $AUTOLOAD; 427our $AUTOLOAD;
309our @ISA; 428our @ISA;
310 429
… …
312 431
313our @REGISTRY; 432our @REGISTRY;
314 433
315my @models = ( 434my @models = (
316 [Coro::EV:: => AnyEvent::Impl::CoroEV::], 435 [Coro::EV:: => AnyEvent::Impl::CoroEV::],
436 [Coro::Event:: => AnyEvent::Impl::CoroEvent::],
317 [EV:: => AnyEvent::Impl::EV::], 437 [EV:: => AnyEvent::Impl::EV::],
318 [Coro::Event:: => AnyEvent::Impl::CoroEvent::],
319 [Event:: => AnyEvent::Impl::Event::], 438 [Event:: => AnyEvent::Impl::Event::],
320 [Glib:: => AnyEvent::Impl::Glib::], 439 [Glib:: => AnyEvent::Impl::Glib::],
321 [Tk:: => AnyEvent::Impl::Tk::], 440 [Tk:: => AnyEvent::Impl::Tk::],
322 [AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::], 441 [AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
442 [Event::Lib:: => AnyEvent::Impl::EventLib::],
323); 443);
324 444
325our %method = map +($_ => 1), qw(io timer condvar broadcast wait signal one_event DESTROY); 445our %method = map +($_ => 1), qw(io timer condvar broadcast wait signal one_event DESTROY);
326 446
327sub detect() { 447sub detect() {
328 unless ($MODEL) { 448 unless ($MODEL) {
329 no strict 'refs'; 449 no strict 'refs';
330 450
451 if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
452 my $model = "AnyEvent::Impl::$1";
453 if (eval "require $model") {
454 $MODEL = $model;
455 warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;
456 }
457 }
458
331 # check for already loaded models 459 # check for already loaded models
460 unless ($MODEL) {
332 for (@REGISTRY, @models) { 461 for (@REGISTRY, @models) {
333 my ($package, $model) = @$_; 462 my ($package, $model) = @$_;
334 if (${"$package\::VERSION"} > 0) { 463 if (${"$package\::VERSION"} > 0) {
335 if (eval "require $model") { 464 if (eval "require $model") {
336 $MODEL = $model; 465 $MODEL = $model;
337 warn "AnyEvent: found model '$model', using it.\n" if $verbose > 1; 466 warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;
338 last; 467 last;
468 }
339 } 469 }
340 } 470 }
341 }
342 471
343 unless ($MODEL) { 472 unless ($MODEL) {
344 # try to load a model 473 # try to load a model
345 474
346 for (@REGISTRY, @models) { 475 for (@REGISTRY, @models) {
347 my ($package, $model) = @$_; 476 my ($package, $model) = @$_;
348 if (eval "require $package" 477 if (eval "require $package"
349 and ${"$package\::VERSION"} > 0 478 and ${"$package\::VERSION"} > 0
350 and eval "require $model") { 479 and eval "require $model") {
351 $MODEL = $model; 480 $MODEL = $model;
352 warn "AnyEvent: autoprobed and loaded model '$model', using it.\n" if $verbose > 1; 481 warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;
353 last; 482 last;
483 }
354 } 484 }
485
486 $MODEL
487 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.";
355 } 488 }
356
357 $MODEL
358 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.";
359 } 489 }
360 490
361 unshift @ISA, $MODEL; 491 unshift @ISA, $MODEL;
362 push @{"$MODEL\::ISA"}, "AnyEvent::Base"; 492 push @{"$MODEL\::ISA"}, "AnyEvent::Base";
363 } 493 }
… …
474 undef $CHLD_W unless keys %PID_CB; 604 undef $CHLD_W unless keys %PID_CB;
475} 605}
476 606
477=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE 607=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
478 608
609This is an advanced topic that you do not normally need to use AnyEvent in
610a module. This section is only of use to event loop authors who want to
611provide AnyEvent compatibility.
612
479If you need to support another event library which isn't directly 613If you need to support another event library which isn't directly
480supported by AnyEvent, you can supply your own interface to it by 614supported by AnyEvent, you can supply your own interface to it by
481pushing, before the first watcher gets created, the package name of 615pushing, before the first watcher gets created, the package name of
482the event module and the package name of the interface to use onto 616the event module and the package name of the interface to use onto
483C<@AnyEvent::REGISTRY>. You can do that before and even without loading 617C<@AnyEvent::REGISTRY>. You can do that before and even without loading
484AnyEvent. 618AnyEvent, so it is reasonably cheap.
485 619
486Example: 620Example:
487 621
488 push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::]; 622 push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];
489 623
490This tells AnyEvent to (literally) use the C<urxvt::anyevent::> 624This tells AnyEvent to (literally) use the C<urxvt::anyevent::>
491package/class when it finds the C<urxvt> package/module is loaded. When 625package/class when it finds the C<urxvt> package/module is already loaded.
626
492AnyEvent is loaded and asked to find a suitable event model, it will 627When AnyEvent is loaded and asked to find a suitable event model, it
493first check for the presence of urxvt. 628will first check for the presence of urxvt by trying to C<use> the
629C<urxvt::anyevent> module.
494 630
495The class should provide implementations for all watcher types (see 631The class should provide implementations for all watcher types. See
496L<AnyEvent::Impl::Event> (source code), L<AnyEvent::Impl::Glib> 632L<AnyEvent::Impl::EV> (source code), L<AnyEvent::Impl::Glib> (Source code)
497(Source code) and so on for actual examples, use C<perldoc -m 633and so on for actual examples. Use C<perldoc -m AnyEvent::Impl::Glib> to
498AnyEvent::Impl::Glib> to see the sources). 634see the sources.
499 635
636If you don't provide C<signal> and C<child> watchers than AnyEvent will
637provide suitable (hopefully) replacements.
638
500The above isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt) 639The above example isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt)
501uses the above line as-is. An interface isn't included in AnyEvent 640terminal emulator uses the above line as-is. An interface isn't included
502because it doesn't make sense outside the embedded interpreter inside 641in AnyEvent because it doesn't make sense outside the embedded interpreter
503I<rxvt-unicode>, and it is updated and maintained as part of the 642inside I<rxvt-unicode>, and it is updated and maintained as part of the
504I<rxvt-unicode> distribution. 643I<rxvt-unicode> distribution.
505 644
506I<rxvt-unicode> also cheats a bit by not providing blocking access to 645I<rxvt-unicode> also cheats a bit by not providing blocking access to
507condition variables: code blocking while waiting for a condition will 646condition variables: code blocking while waiting for a condition will
508C<die>. This still works with most modules/usages, and blocking calls must 647C<die>. This still works with most modules/usages, and blocking calls must
509not be in an interactive application, so it makes sense. 648not be done in an interactive application, so it makes sense.
510 649
511=head1 ENVIRONMENT VARIABLES 650=head1 ENVIRONMENT VARIABLES
512 651
513The following environment variables are used by this module: 652The following environment variables are used by this module:
514 653
515C<PERL_ANYEVENT_VERBOSE> when set to C<2> or higher, reports which event 654=over 4
516model gets used.
517 655
656=item C<PERL_ANYEVENT_VERBOSE>
657
658When set to C<2> or higher, cause AnyEvent to report to STDERR which event
659model it chooses.
660
661=item C<PERL_ANYEVENT_MODEL>
662
663This can be used to specify the event model to be used by AnyEvent, before
664autodetection and -probing kicks in. It must be a string consisting
665entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
666and the resulting module name is loaded and if the load was successful,
667used as event model. If it fails to load AnyEvent will proceed with
668autodetection and -probing.
669
670This functionality might change in future versions.
671
672For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
673could start your program like this:
674
675 PERL_ANYEVENT_MODEL=Perl perl ...
676
677=back
678
518=head1 EXAMPLE 679=head1 EXAMPLE PROGRAM
519 680
520The following program uses an io watcher to read data from stdin, a timer 681The following program uses an IO watcher to read data from STDIN, a timer
521to display a message once per second, and a condvar to exit the program 682to display a message once per second, and a condition variable to quit the
522when the user enters quit: 683program when the user enters quit:
523 684
524 use AnyEvent; 685 use AnyEvent;
525 686
526 my $cv = AnyEvent->condvar; 687 my $cv = AnyEvent->condvar;
527 688
528 my $io_watcher = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub { 689 my $io_watcher = AnyEvent->io (
690 fh => \*STDIN,
691 poll => 'r',
692 cb => sub {
529 warn "io event <$_[0]>\n"; # will always output <r> 693 warn "io event <$_[0]>\n"; # will always output <r>
530 chomp (my $input = <STDIN>); # read a line 694 chomp (my $input = <STDIN>); # read a line
531 warn "read: $input\n"; # output what has been read 695 warn "read: $input\n"; # output what has been read
532 $cv->broadcast if $input =~ /^q/i; # quit program if /^q/i 696 $cv->broadcast if $input =~ /^q/i; # quit program if /^q/i
697 },
533 }); 698 );
534 699
535 my $time_watcher; # can only be used once 700 my $time_watcher; # can only be used once
536 701
537 sub new_timer { 702 sub new_timer {
538 $timer = AnyEvent->timer (after => 1, cb => sub { 703 $timer = AnyEvent->timer (after => 1, cb => sub {
… …
620 $txn->{finished}->wait; 785 $txn->{finished}->wait;
621 return $txn->{result}; 786 return $txn->{result};
622 787
623The actual code goes further and collects all errors (C<die>s, exceptions) 788The actual code goes further and collects all errors (C<die>s, exceptions)
624that occured during request processing. The C<result> method detects 789that occured during request processing. The C<result> method detects
625wether an exception as thrown (it is stored inside the $txn object) 790whether an exception as thrown (it is stored inside the $txn object)
626and just throws the exception, which means connection errors and other 791and just throws the exception, which means connection errors and other
627problems get reported tot he code that tries to use the result, not in a 792problems get reported tot he code that tries to use the result, not in a
628random callback. 793random callback.
629 794
630All of this enables the following usage styles: 795All of this enables the following usage styles:
631 796
6321. Blocking: 7971. Blocking:
633 798
634 my $data = $fcp->client_get ($url); 799 my $data = $fcp->client_get ($url);
635 800
6362. Blocking, but parallelizing: 8012. Blocking, but running in parallel:
637 802
638 my @datas = map $_->result, 803 my @datas = map $_->result,
639 map $fcp->txn_client_get ($_), 804 map $fcp->txn_client_get ($_),
640 @urls; 805 @urls;
641 806
642Both blocking examples work without the module user having to know 807Both blocking examples work without the module user having to know
643anything about events. 808anything about events.
644 809
6453a. Event-based in a main program, using any support Event module: 8103a. Event-based in a main program, using any supported event module:
646 811
647 use Event; 812 use EV;
648 813
649 $fcp->txn_client_get ($url)->cb (sub { 814 $fcp->txn_client_get ($url)->cb (sub {
650 my $txn = shift; 815 my $txn = shift;
651 my $data = $txn->result; 816 my $data = $txn->result;
652 ... 817 ...
653 }); 818 });
654 819
655 Event::loop; 820 EV::loop;
656 821
6573b. The module user could use AnyEvent, too: 8223b. The module user could use AnyEvent, too:
658 823
659 use AnyEvent; 824 use AnyEvent;
660 825
… …
665 $quit->broadcast; 830 $quit->broadcast;
666 }); 831 });
667 832
668 $quit->wait; 833 $quit->wait;
669 834
835=head1 FORK
836
837Most event libraries are not fork-safe. The ones who are usually are
838because they are so inefficient. Only L<EV> is fully fork-aware.
839
840If you have to fork, you must either do so I<before> creating your first
841watcher OR you must not use AnyEvent at all in the child.
842
843=head1 SECURITY CONSIDERATIONS
844
845AnyEvent can be forced to load any event model via
846$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to
847execute arbitrary code or directly gain access, it can easily be used to
848make the program hang or malfunction in subtle ways, as AnyEvent watchers
849will not be active when the program uses a different event model than
850specified in the variable.
851
852You can make AnyEvent completely ignore this variable by deleting it
853before the first watcher gets created, e.g. with a C<BEGIN> block:
854
855 BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
856
857 use AnyEvent;
858
670=head1 SEE ALSO 859=head1 SEE ALSO
671 860
672Event modules: L<Coro::Event>, L<Coro>, L<Event>, L<Glib::Event>, L<Glib>. 861Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,
862L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,
863L<Event::Lib>.
673 864
865Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,
674Implementations: L<AnyEvent::Impl::Coro>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>. 866L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,
867L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>.
675 868
676Nontrivial usage example: L<Net::FCP>. 869Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.
677 870
678=head1 871=head1 AUTHOR
872
873 Marc Lehmann <schmorp@schmorp.de>
874 http://home.schmorp.de/
679 875
680=cut 876=cut
681 877
6821 8781
683 879

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