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Revision 1.57 by root, Thu Apr 24 03:19:28 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 - 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
77loaded: L<Coro::Event>, L<Event>, L<Glib>, L<Tk>. The first one found is 84the following modules is already loaded: L<Coro::EV>, L<Coro::Event>,
85L<EV>, L<Event>, L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>. The first one
78used. If none is found, the module tries to load these modules in the 86found is used. If none are found, the module tries to load these modules
79order given. The first one that could be successfully loaded will be 87(excluding Event::Lib and Qt) in the order given. The first one that can
80used. If still none could be found, AnyEvent will fall back to a pure-perl 88be successfully loaded will be used. If, after this, still none could be
81event loop, which is also not very efficient. 89found, AnyEvent will fall back to a pure-perl event loop, which is not
90very efficient, but should work everywhere.
82 91
83Because AnyEvent first checks for modules that are already loaded, loading 92Because AnyEvent first checks for modules that are already loaded, loading
84an Event model explicitly before first using AnyEvent will likely make 93an event model explicitly before first using AnyEvent will likely make
85that model the default. For example: 94that model the default. For example:
86 95
87 use Tk; 96 use Tk;
88 use AnyEvent; 97 use AnyEvent;
89 98
90 # .. AnyEvent will likely default to Tk 99 # .. AnyEvent will likely default to Tk
100
101The I<likely> means that, if any module loads another event model and
102starts using it, all bets are off. Maybe you should tell their authors to
103use AnyEvent so their modules work together with others seamlessly...
91 104
92The pure-perl implementation of AnyEvent is called 105The pure-perl implementation of AnyEvent is called
93C<AnyEvent::Impl::Perl>. Like other event modules you can load it 106C<AnyEvent::Impl::Perl>. Like other event modules you can load it
94explicitly. 107explicitly.
95 108
… …
98AnyEvent has the central concept of a I<watcher>, which is an object that 111AnyEvent 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 112stores relevant data for each kind of event you are waiting for, such as
100the callback to call, the filehandle to watch, etc. 113the callback to call, the filehandle to watch, etc.
101 114
102These watchers are normal Perl objects with normal Perl lifetime. After 115These watchers are normal Perl objects with normal Perl lifetime. After
103creating a watcher it will immediately "watch" for events and invoke 116creating a watcher it will immediately "watch" for events and invoke the
117callback when the event occurs (of course, only when the event model
118is in control).
119
104the callback. To disable the watcher you have to destroy it (e.g. by 120To 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 121variable you store it in to C<undef> or otherwise deleting all references
106references to it). 122to it).
107 123
108All watchers are created by calling a method on the C<AnyEvent> class. 124All watchers are created by calling a method on the C<AnyEvent> class.
109 125
126Many watchers either are used with "recursion" (repeating timers for
127example), or need to refer to their watcher object in other ways.
128
129An any way to achieve that is this pattern:
130
131 my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
132 # you can use $w here, for example to undef it
133 undef $w;
134 });
135
136Note that C<my $w; $w => combination. This is necessary because in Perl,
137my variables are only visible after the statement in which they are
138declared.
139
110=head2 IO WATCHERS 140=head2 IO WATCHERS
111 141
112You can create I/O watcher by calling the C<< AnyEvent->io >> method with 142You can create an I/O watcher by calling the C<< AnyEvent->io >> method
113the following mandatory arguments: 143with the following mandatory key-value pairs as arguments:
114 144
115C<fh> the Perl I<filehandle> (not filedescriptor) to watch for 145C<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 146events. 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 147creates a watcher waiting for "r"eadable or "w"ritable events,
118to invoke everytime the filehandle becomes ready. 148respectively. C<cb> is the callback to invoke each time the file handle
149becomes ready.
119 150
120Only one io watcher per C<fh> and C<poll> combination is allowed (i.e. on 151As long as the I/O watcher exists it will keep the file descriptor or a
121a socket you can have one r + one w, not any more (limitation comes from 152copy of it alive/open.
122Tk - if you are sure you are not using Tk this limitation is gone).
123 153
124Filehandles will be kept alive, so as long as the watcher exists, the 154It is not allowed to close a file handle as long as any watcher is active
125filehandle exists, too. 155on the underlying file descriptor.
156
157Some event loops issue spurious readyness notifications, so you should
158always use non-blocking calls when reading/writing from/to your file
159handles.
126 160
127Example: 161Example:
128 162
129 # wait for readability of STDIN, then read a line and disable the watcher 163 # 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 { 164 my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
… …
136=head2 TIME WATCHERS 170=head2 TIME WATCHERS
137 171
138You can create a time watcher by calling the C<< AnyEvent->timer >> 172You can create a time watcher by calling the C<< AnyEvent->timer >>
139method with the following mandatory arguments: 173method with the following mandatory arguments:
140 174
141C<after> after how many seconds (fractions are supported) should the timer 175C<after> specifies after how many seconds (fractional values are
142activate. C<cb> the callback to invoke. 176supported) should the timer activate. C<cb> the callback to invoke in that
177case.
143 178
144The timer callback will be invoked at most once: if you want a repeating 179The 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 180timer you have to create a new watcher (this is a limitation by both Tk
146and Glib). 181and Glib).
147 182
… …
153 }); 188 });
154 189
155 # to cancel the timer: 190 # to cancel the timer:
156 undef $w; 191 undef $w;
157 192
193Example 2:
194
195 # fire an event after 0.5 seconds, then roughly every second
196 my $w;
197
198 my $cb = sub {
199 # cancel the old timer while creating a new one
200 $w = AnyEvent->timer (after => 1, cb => $cb);
201 };
202
203 # start the "loop" by creating the first watcher
204 $w = AnyEvent->timer (after => 0.5, cb => $cb);
205
206=head3 TIMING ISSUES
207
208There are two ways to handle timers: based on real time (relative, "fire
209in 10 seconds") and based on wallclock time (absolute, "fire at 12
210o'clock").
211
212While most event loops expect timers to specified in a relative way, they use
213absolute time internally. This makes a difference when your clock "jumps",
214for example, when ntp decides to set your clock backwards from the wrong 2014-01-01 to
2152008-01-01, a watcher that you created to fire "after" a second might actually take
216six years to finally fire.
217
218AnyEvent cannot compensate for this. The only event loop that is conscious
219about these issues is L<EV>, which offers both relative (ev_timer) and
220absolute (ev_periodic) timers.
221
222AnyEvent always prefers relative timers, if available, matching the
223AnyEvent API.
224
225=head2 SIGNAL WATCHERS
226
227You can watch for signals using a signal watcher, C<signal> is the signal
228I<name> without any C<SIG> prefix, C<cb> is the Perl callback to
229be invoked whenever a signal occurs.
230
231Multiple signals occurances can be clumped together into one callback
232invocation, and callback invocation will be synchronous. synchronous means
233that it might take a while until the signal gets handled by the process,
234but it is guarenteed not to interrupt any other callbacks.
235
236The main advantage of using these watchers is that you can share a signal
237between multiple watchers.
238
239This watcher might use C<%SIG>, so programs overwriting those signals
240directly will likely not work correctly.
241
242Example: exit on SIGINT
243
244 my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
245
246=head2 CHILD PROCESS WATCHERS
247
248You can also watch on a child process exit and catch its exit status.
249
250The child process is specified by the C<pid> argument (if set to C<0>, it
251watches for any child process exit). The watcher will trigger as often
252as status change for the child are received. This works by installing a
253signal handler for C<SIGCHLD>. The callback will be called with the pid
254and exit status (as returned by waitpid).
255
256Example: wait for pid 1333
257
258 my $w = AnyEvent->child (
259 pid => 1333,
260 cb => sub {
261 my ($pid, $status) = @_;
262 warn "pid $pid exited with status $status";
263 },
264 );
265
158=head2 CONDITION WATCHERS 266=head2 CONDITION VARIABLES
159 267
160Condition watchers can be created by calling the C<< AnyEvent->condvar >> 268Condition variables can be created by calling the C<< AnyEvent->condvar >>
161method without any arguments. 269method without any arguments.
162 270
163A condition watcher watches for a condition - precisely that the C<< 271A condition variable waits for a condition - precisely that the C<<
164->broadcast >> method has been called. 272->broadcast >> method has been called.
165 273
274They are very useful to signal that a condition has been fulfilled, for
275example, if you write a module that does asynchronous http requests,
276then a condition variable would be the ideal candidate to signal the
277availability of results.
278
279You can also use condition variables to block your main program until
280an event occurs - for example, you could C<< ->wait >> in your main
281program until the user clicks the Quit button in your app, which would C<<
282->broadcast >> the "quit" event.
283
166Note that condition watchers recurse into the event loop - if you have 284Note that condition variables recurse into the event loop - if you have
167two watchers that call C<< ->wait >> in a round-robbin fashion, you 285two 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 286lose. Therefore, condition variables are good to export to your caller, but
169you should avoid making a blocking wait, at least in callbacks, as this 287you should avoid making a blocking wait yourself, at least in callbacks,
170usually asks for trouble. 288as this asks for trouble.
171 289
172The watcher has only two methods: 290This object has two methods:
173 291
174=over 4 292=over 4
175 293
176=item $cv->wait 294=item $cv->wait
177 295
178Wait (blocking if necessary) until the C<< ->broadcast >> method has been 296Wait (blocking if necessary) until the C<< ->broadcast >> method has been
179called on c<$cv>, while servicing other watchers normally. 297called on c<$cv>, while servicing other watchers normally.
180 298
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 299You can only wait once on a condition - additional calls will return
189immediately. 300immediately.
190 301
302Not all event models support a blocking wait - some die in that case
303(programs might want to do that to stay interactive), so I<if you are
304using this from a module, never require a blocking wait>, but let the
305caller decide whether the call will block or not (for example, by coupling
306condition variables with some kind of request results and supporting
307callbacks so the caller knows that getting the result will not block,
308while still suppporting blocking waits if the caller so desires).
309
310Another reason I<never> to C<< ->wait >> in a module is that you cannot
311sensibly have two C<< ->wait >>'s in parallel, as that would require
312multiple interpreters or coroutines/threads, none of which C<AnyEvent>
313can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and
314L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
315from different coroutines, however).
316
191=item $cv->broadcast 317=item $cv->broadcast
192 318
193Flag the condition as ready - a running C<< ->wait >> and all further 319Flag 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 320calls to C<wait> will (eventually) return after this method has been
195is waiting the broadcast will be remembered.. 321called. If nobody is waiting the broadcast will be remembered..
322
323=back
196 324
197Example: 325Example:
198 326
199 # wait till the result is ready 327 # wait till the result is ready
200 my $result_ready = AnyEvent->condvar; 328 my $result_ready = AnyEvent->condvar;
201 329
202 # do something such as adding a timer 330 # do something such as adding a timer
203 # or socket watcher the calls $result_ready->broadcast 331 # or socket watcher the calls $result_ready->broadcast
204 # when the "result" is ready. 332 # when the "result" is ready.
333 # in this case, we simply use a timer:
334 my $w = AnyEvent->timer (
335 after => 1,
336 cb => sub { $result_ready->broadcast },
337 );
205 338
339 # this "blocks" (while handling events) till the watcher
340 # calls broadcast
206 $result_ready->wait; 341 $result_ready->wait;
207 342
208=back 343=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
237 344
238=over 4 345=over 4
239 346
240=item $AnyEvent::MODEL 347=item $AnyEvent::MODEL
241 348
… …
246AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>). 353AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).
247 354
248The known classes so far are: 355The known classes so far are:
249 356
250 AnyEvent::Impl::CoroEV based on Coro::EV, best choice. 357 AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
251 AnyEvent::Impl::EV based on EV (an interface to libev, also best choice).
252 AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice. 358 AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
359 AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
253 AnyEvent::Impl::Event based on Event, also second best choice :) 360 AnyEvent::Impl::Event based on Event, second best choice.
254 AnyEvent::Impl::Glib based on Glib, second-best choice. 361 AnyEvent::Impl::Glib based on Glib, third-best choice.
255 AnyEvent::Impl::Tk based on Tk, very bad choice. 362 AnyEvent::Impl::Tk based on Tk, very bad choice.
256 AnyEvent::Impl::Perl pure-perl implementation, inefficient. 363 AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
364 AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
365 AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
257 366
258=item AnyEvent::detect 367=item AnyEvent::detect
259 368
260Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model if 369Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
261necessary. You should only call this function right before you would have 370if necessary. You should only call this function right before you would
262created an AnyEvent watcher anyway, that is, very late at runtime. 371have created an AnyEvent watcher anyway, that is, as late as possible at
372runtime.
263 373
264=back 374=back
265 375
266=head1 WHAT TO DO IN A MODULE 376=head1 WHAT TO DO IN A MODULE
267 377
268As a module author, you should "use AnyEvent" and call AnyEvent methods 378As 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. 379freely, but you should not load a specific event module or rely on it.
270 380
271Be careful when you create watchers in the module body - Anyevent will 381Be 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 382decide 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 383by calling AnyEvent in your module body you force the user of your module
274to load the event module first. 384to load the event module first.
275 385
386Never call C<< ->wait >> on a condition variable unless you I<know> that
387the C<< ->broadcast >> method has been called on it already. This is
388because it will stall the whole program, and the whole point of using
389events is to stay interactive.
390
391It is fine, however, to call C<< ->wait >> when the user of your module
392requests it (i.e. if you create a http request object ad have a method
393called C<results> that returns the results, it should call C<< ->wait >>
394freely, as the user of your module knows what she is doing. always).
395
276=head1 WHAT TO DO IN THE MAIN PROGRAM 396=head1 WHAT TO DO IN THE MAIN PROGRAM
277 397
278There will always be a single main program - the only place that should 398There will always be a single main program - the only place that should
279dictate which event model to use. 399dictate which event model to use.
280 400
281If it doesn't care, it can just "use AnyEvent" and use it itself, or not 401If 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. 402do anything special (it does not need to be event-based) and let AnyEvent
403decide which implementation to chose if some module relies on it.
283 404
284If the main program relies on a specific event model (for example, in Gtk2 405If 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 406Gtk2 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 407event module before loading AnyEvent or any module that uses it: generally
287as possible. The reason is that modules might create watchers when they 408speaking, 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 409modules might create watchers when they are loaded, and AnyEvent will
289it creates watchers, and it might chose the wrong one unless you load the 410decide on the event model to use as soon as it creates watchers, and it
290correct one yourself. 411might chose the wrong one unless you load the correct one yourself.
291 412
292You can chose to use a rather inefficient pure-perl implementation by 413You can chose to use a rather inefficient pure-perl implementation by
293loading the C<AnyEvent::Impl::Perl> module, but letting AnyEvent chose is 414loading the C<AnyEvent::Impl::Perl> module, which gives you similar
294generally better. 415behaviour everywhere, but letting AnyEvent chose is generally better.
295 416
296=cut 417=cut
297 418
298package AnyEvent; 419package AnyEvent;
299 420
300no warnings; 421no warnings;
301use strict; 422use strict;
302 423
303use Carp; 424use Carp;
304 425
305our $VERSION = '3.0'; 426our $VERSION = '3.12';
306our $MODEL; 427our $MODEL;
307 428
308our $AUTOLOAD; 429our $AUTOLOAD;
309our @ISA; 430our @ISA;
310 431
… …
312 433
313our @REGISTRY; 434our @REGISTRY;
314 435
315my @models = ( 436my @models = (
316 [Coro::EV:: => AnyEvent::Impl::CoroEV::], 437 [Coro::EV:: => AnyEvent::Impl::CoroEV::],
438 [Coro::Event:: => AnyEvent::Impl::CoroEvent::],
317 [EV:: => AnyEvent::Impl::EV::], 439 [EV:: => AnyEvent::Impl::EV::],
318 [Coro::Event:: => AnyEvent::Impl::CoroEvent::],
319 [Event:: => AnyEvent::Impl::Event::], 440 [Event:: => AnyEvent::Impl::Event::],
320 [Glib:: => AnyEvent::Impl::Glib::], 441 [Glib:: => AnyEvent::Impl::Glib::],
321 [Tk:: => AnyEvent::Impl::Tk::], 442 [Tk:: => AnyEvent::Impl::Tk::],
322 [AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::], 443 [AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
323); 444);
445my @models_detect = (
446 [Qt:: => AnyEvent::Impl::Qt::], # requires special main program
447 [Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
448);
324 449
325our %method = map +($_ => 1), qw(io timer condvar broadcast wait signal one_event DESTROY); 450our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY);
326 451
327sub detect() { 452sub detect() {
328 unless ($MODEL) { 453 unless ($MODEL) {
329 no strict 'refs'; 454 no strict 'refs';
330 455
456 if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
457 my $model = "AnyEvent::Impl::$1";
458 if (eval "require $model") {
459 $MODEL = $model;
460 warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;
461 }
462 }
463
331 # check for already loaded models 464 # check for already loaded models
465 unless ($MODEL) {
332 for (@REGISTRY, @models) { 466 for (@REGISTRY, @models, @models_detect) {
333 my ($package, $model) = @$_; 467 my ($package, $model) = @$_;
334 if (${"$package\::VERSION"} > 0) { 468 if (${"$package\::VERSION"} > 0) {
335 if (eval "require $model") { 469 if (eval "require $model") {
336 $MODEL = $model; 470 $MODEL = $model;
337 warn "AnyEvent: found model '$model', using it.\n" if $verbose > 1; 471 warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;
338 last; 472 last;
473 }
339 } 474 }
340 } 475 }
341 }
342 476
343 unless ($MODEL) { 477 unless ($MODEL) {
344 # try to load a model 478 # try to load a model
345 479
346 for (@REGISTRY, @models) { 480 for (@REGISTRY, @models) {
347 my ($package, $model) = @$_; 481 my ($package, $model) = @$_;
348 if (eval "require $package" 482 if (eval "require $package"
349 and ${"$package\::VERSION"} > 0 483 and ${"$package\::VERSION"} > 0
350 and eval "require $model") { 484 and eval "require $model") {
351 $MODEL = $model; 485 $MODEL = $model;
352 warn "AnyEvent: autoprobed and loaded model '$model', using it.\n" if $verbose > 1; 486 warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;
353 last; 487 last;
488 }
354 } 489 }
490
491 $MODEL
492 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 } 493 }
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 } 494 }
360 495
361 unshift @ISA, $MODEL; 496 unshift @ISA, $MODEL;
362 push @{"$MODEL\::ISA"}, "AnyEvent::Base"; 497 push @{"$MODEL\::ISA"}, "AnyEvent::Base";
363 } 498 }
… …
474 undef $CHLD_W unless keys %PID_CB; 609 undef $CHLD_W unless keys %PID_CB;
475} 610}
476 611
477=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE 612=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
478 613
614This is an advanced topic that you do not normally need to use AnyEvent in
615a module. This section is only of use to event loop authors who want to
616provide AnyEvent compatibility.
617
479If you need to support another event library which isn't directly 618If you need to support another event library which isn't directly
480supported by AnyEvent, you can supply your own interface to it by 619supported by AnyEvent, you can supply your own interface to it by
481pushing, before the first watcher gets created, the package name of 620pushing, before the first watcher gets created, the package name of
482the event module and the package name of the interface to use onto 621the event module and the package name of the interface to use onto
483C<@AnyEvent::REGISTRY>. You can do that before and even without loading 622C<@AnyEvent::REGISTRY>. You can do that before and even without loading
484AnyEvent. 623AnyEvent, so it is reasonably cheap.
485 624
486Example: 625Example:
487 626
488 push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::]; 627 push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];
489 628
490This tells AnyEvent to (literally) use the C<urxvt::anyevent::> 629This tells AnyEvent to (literally) use the C<urxvt::anyevent::>
491package/class when it finds the C<urxvt> package/module is loaded. When 630package/class when it finds the C<urxvt> package/module is already loaded.
631
492AnyEvent is loaded and asked to find a suitable event model, it will 632When AnyEvent is loaded and asked to find a suitable event model, it
493first check for the presence of urxvt. 633will first check for the presence of urxvt by trying to C<use> the
634C<urxvt::anyevent> module.
494 635
495The class should provide implementations for all watcher types (see 636The class should provide implementations for all watcher types. See
496L<AnyEvent::Impl::Event> (source code), L<AnyEvent::Impl::Glib> 637L<AnyEvent::Impl::EV> (source code), L<AnyEvent::Impl::Glib> (Source code)
497(Source code) and so on for actual examples, use C<perldoc -m 638and so on for actual examples. Use C<perldoc -m AnyEvent::Impl::Glib> to
498AnyEvent::Impl::Glib> to see the sources). 639see the sources.
499 640
641If you don't provide C<signal> and C<child> watchers than AnyEvent will
642provide suitable (hopefully) replacements.
643
500The above isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt) 644The 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 645terminal emulator uses the above line as-is. An interface isn't included
502because it doesn't make sense outside the embedded interpreter inside 646in AnyEvent because it doesn't make sense outside the embedded interpreter
503I<rxvt-unicode>, and it is updated and maintained as part of the 647inside I<rxvt-unicode>, and it is updated and maintained as part of the
504I<rxvt-unicode> distribution. 648I<rxvt-unicode> distribution.
505 649
506I<rxvt-unicode> also cheats a bit by not providing blocking access to 650I<rxvt-unicode> also cheats a bit by not providing blocking access to
507condition variables: code blocking while waiting for a condition will 651condition variables: code blocking while waiting for a condition will
508C<die>. This still works with most modules/usages, and blocking calls must 652C<die>. This still works with most modules/usages, and blocking calls must
509not be in an interactive application, so it makes sense. 653not be done in an interactive application, so it makes sense.
510 654
511=head1 ENVIRONMENT VARIABLES 655=head1 ENVIRONMENT VARIABLES
512 656
513The following environment variables are used by this module: 657The following environment variables are used by this module:
514 658
515C<PERL_ANYEVENT_VERBOSE> when set to C<2> or higher, reports which event 659=over 4
516model gets used.
517 660
661=item C<PERL_ANYEVENT_VERBOSE>
662
663When set to C<2> or higher, cause AnyEvent to report to STDERR which event
664model it chooses.
665
666=item C<PERL_ANYEVENT_MODEL>
667
668This can be used to specify the event model to be used by AnyEvent, before
669autodetection and -probing kicks in. It must be a string consisting
670entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
671and the resulting module name is loaded and if the load was successful,
672used as event model. If it fails to load AnyEvent will proceed with
673autodetection and -probing.
674
675This functionality might change in future versions.
676
677For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
678could start your program like this:
679
680 PERL_ANYEVENT_MODEL=Perl perl ...
681
682=back
683
518=head1 EXAMPLE 684=head1 EXAMPLE PROGRAM
519 685
520The following program uses an io watcher to read data from stdin, a timer 686The 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 687to display a message once per second, and a condition variable to quit the
522when the user enters quit: 688program when the user enters quit:
523 689
524 use AnyEvent; 690 use AnyEvent;
525 691
526 my $cv = AnyEvent->condvar; 692 my $cv = AnyEvent->condvar;
527 693
528 my $io_watcher = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub { 694 my $io_watcher = AnyEvent->io (
695 fh => \*STDIN,
696 poll => 'r',
697 cb => sub {
529 warn "io event <$_[0]>\n"; # will always output <r> 698 warn "io event <$_[0]>\n"; # will always output <r>
530 chomp (my $input = <STDIN>); # read a line 699 chomp (my $input = <STDIN>); # read a line
531 warn "read: $input\n"; # output what has been read 700 warn "read: $input\n"; # output what has been read
532 $cv->broadcast if $input =~ /^q/i; # quit program if /^q/i 701 $cv->broadcast if $input =~ /^q/i; # quit program if /^q/i
702 },
533 }); 703 );
534 704
535 my $time_watcher; # can only be used once 705 my $time_watcher; # can only be used once
536 706
537 sub new_timer { 707 sub new_timer {
538 $timer = AnyEvent->timer (after => 1, cb => sub { 708 $timer = AnyEvent->timer (after => 1, cb => sub {
… …
620 $txn->{finished}->wait; 790 $txn->{finished}->wait;
621 return $txn->{result}; 791 return $txn->{result};
622 792
623The actual code goes further and collects all errors (C<die>s, exceptions) 793The actual code goes further and collects all errors (C<die>s, exceptions)
624that occured during request processing. The C<result> method detects 794that occured during request processing. The C<result> method detects
625wether an exception as thrown (it is stored inside the $txn object) 795whether an exception as thrown (it is stored inside the $txn object)
626and just throws the exception, which means connection errors and other 796and 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 797problems get reported tot he code that tries to use the result, not in a
628random callback. 798random callback.
629 799
630All of this enables the following usage styles: 800All of this enables the following usage styles:
631 801
6321. Blocking: 8021. Blocking:
633 803
634 my $data = $fcp->client_get ($url); 804 my $data = $fcp->client_get ($url);
635 805
6362. Blocking, but parallelizing: 8062. Blocking, but running in parallel:
637 807
638 my @datas = map $_->result, 808 my @datas = map $_->result,
639 map $fcp->txn_client_get ($_), 809 map $fcp->txn_client_get ($_),
640 @urls; 810 @urls;
641 811
642Both blocking examples work without the module user having to know 812Both blocking examples work without the module user having to know
643anything about events. 813anything about events.
644 814
6453a. Event-based in a main program, using any support Event module: 8153a. Event-based in a main program, using any supported event module:
646 816
647 use Event; 817 use EV;
648 818
649 $fcp->txn_client_get ($url)->cb (sub { 819 $fcp->txn_client_get ($url)->cb (sub {
650 my $txn = shift; 820 my $txn = shift;
651 my $data = $txn->result; 821 my $data = $txn->result;
652 ... 822 ...
653 }); 823 });
654 824
655 Event::loop; 825 EV::loop;
656 826
6573b. The module user could use AnyEvent, too: 8273b. The module user could use AnyEvent, too:
658 828
659 use AnyEvent; 829 use AnyEvent;
660 830
… …
665 $quit->broadcast; 835 $quit->broadcast;
666 }); 836 });
667 837
668 $quit->wait; 838 $quit->wait;
669 839
840=head1 FORK
841
842Most event libraries are not fork-safe. The ones who are usually are
843because they are so inefficient. Only L<EV> is fully fork-aware.
844
845If you have to fork, you must either do so I<before> creating your first
846watcher OR you must not use AnyEvent at all in the child.
847
848=head1 SECURITY CONSIDERATIONS
849
850AnyEvent can be forced to load any event model via
851$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to
852execute arbitrary code or directly gain access, it can easily be used to
853make the program hang or malfunction in subtle ways, as AnyEvent watchers
854will not be active when the program uses a different event model than
855specified in the variable.
856
857You can make AnyEvent completely ignore this variable by deleting it
858before the first watcher gets created, e.g. with a C<BEGIN> block:
859
860 BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
861
862 use AnyEvent;
863
670=head1 SEE ALSO 864=head1 SEE ALSO
671 865
672Event modules: L<Coro::Event>, L<Coro>, L<Event>, L<Glib::Event>, L<Glib>. 866Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,
867L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,
868L<Event::Lib>, L<Qt>.
673 869
870Implementations: 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>. 871L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,
872L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,
873L<AnyEvent::Impl::Qt>.
675 874
676Nontrivial usage example: L<Net::FCP>. 875Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.
677 876
678=head1 877=head1 AUTHOR
878
879 Marc Lehmann <schmorp@schmorp.de>
880 http://home.schmorp.de/
679 881
680=cut 882=cut
681 883
6821 8841
683 885

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