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Revision 1.41 by root, Mon Apr 7 19:23:59 2008 UTC vs.
Revision 1.59 by root, Thu Apr 24 08:38:13 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
213use absolute time internally. This makes a difference when your clock
214"jumps", for example, when ntp decides to set your clock backwards from
215the wrong date of 2014-01-01 to 2008-01-01, a watcher that is supposed to
216fire "after" a second might actually take six 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, based
220on true relative time) and absolute (ev_periodic, based on wallclock time)
221timers.
222
223AnyEvent always prefers relative timers, if available, matching the
224AnyEvent API.
225
226=head2 SIGNAL WATCHERS
227
228You can watch for signals using a signal watcher, C<signal> is the signal
229I<name> without any C<SIG> prefix, C<cb> is the Perl callback to
230be invoked whenever a signal occurs.
231
232Multiple signal occurances can be clumped together into one callback
233invocation, and callback invocation will be synchronous. synchronous means
234that it might take a while until the signal gets handled by the process,
235but it is guarenteed not to interrupt any other callbacks.
236
237The main advantage of using these watchers is that you can share a signal
238between multiple watchers.
239
240This watcher might use C<%SIG>, so programs overwriting those signals
241directly will likely not work correctly.
242
243Example: exit on SIGINT
244
245 my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
246
247=head2 CHILD PROCESS WATCHERS
248
249You can also watch on a child process exit and catch its exit status.
250
251The child process is specified by the C<pid> argument (if set to C<0>, it
252watches for any child process exit). The watcher will trigger as often
253as status change for the child are received. This works by installing a
254signal handler for C<SIGCHLD>. The callback will be called with the pid
255and exit status (as returned by waitpid).
256
257Example: wait for pid 1333
258
259 my $w = AnyEvent->child (
260 pid => 1333,
261 cb => sub {
262 my ($pid, $status) = @_;
263 warn "pid $pid exited with status $status";
264 },
265 );
266
158=head2 CONDITION WATCHERS 267=head2 CONDITION VARIABLES
159 268
160Condition watchers can be created by calling the C<< AnyEvent->condvar >> 269Condition variables can be created by calling the C<< AnyEvent->condvar >>
161method without any arguments. 270method without any arguments.
162 271
163A condition watcher watches for a condition - precisely that the C<< 272A condition variable waits for a condition - precisely that the C<<
164->broadcast >> method has been called. 273->broadcast >> method has been called.
165 274
275They are very useful to signal that a condition has been fulfilled, for
276example, if you write a module that does asynchronous http requests,
277then a condition variable would be the ideal candidate to signal the
278availability of results.
279
280You can also use condition variables to block your main program until
281an event occurs - for example, you could C<< ->wait >> in your main
282program until the user clicks the Quit button in your app, which would C<<
283->broadcast >> the "quit" event.
284
166Note that condition watchers recurse into the event loop - if you have 285Note that condition variables recurse into the event loop - if you have
167two watchers that call C<< ->wait >> in a round-robbin fashion, you 286two 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 287lose. Therefore, condition variables are good to export to your caller, but
169you should avoid making a blocking wait, at least in callbacks, as this 288you should avoid making a blocking wait yourself, at least in callbacks,
170usually asks for trouble. 289as this asks for trouble.
171 290
172The watcher has only two methods: 291This object has two methods:
173 292
174=over 4 293=over 4
175 294
176=item $cv->wait 295=item $cv->wait
177 296
178Wait (blocking if necessary) until the C<< ->broadcast >> method has been 297Wait (blocking if necessary) until the C<< ->broadcast >> method has been
179called on c<$cv>, while servicing other watchers normally. 298called on c<$cv>, while servicing other watchers normally.
180 299
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 300You can only wait once on a condition - additional calls will return
189immediately. 301immediately.
190 302
303Not all event models support a blocking wait - some die in that case
304(programs might want to do that to stay interactive), so I<if you are
305using this from a module, never require a blocking wait>, but let the
306caller decide whether the call will block or not (for example, by coupling
307condition variables with some kind of request results and supporting
308callbacks so the caller knows that getting the result will not block,
309while still suppporting blocking waits if the caller so desires).
310
311Another reason I<never> to C<< ->wait >> in a module is that you cannot
312sensibly have two C<< ->wait >>'s in parallel, as that would require
313multiple interpreters or coroutines/threads, none of which C<AnyEvent>
314can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and
315L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
316from different coroutines, however).
317
191=item $cv->broadcast 318=item $cv->broadcast
192 319
193Flag the condition as ready - a running C<< ->wait >> and all further 320Flag 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 321calls to C<wait> will (eventually) return after this method has been
195is waiting the broadcast will be remembered.. 322called. If nobody is waiting the broadcast will be remembered..
323
324=back
196 325
197Example: 326Example:
198 327
199 # wait till the result is ready 328 # wait till the result is ready
200 my $result_ready = AnyEvent->condvar; 329 my $result_ready = AnyEvent->condvar;
201 330
202 # do something such as adding a timer 331 # do something such as adding a timer
203 # or socket watcher the calls $result_ready->broadcast 332 # or socket watcher the calls $result_ready->broadcast
204 # when the "result" is ready. 333 # when the "result" is ready.
334 # in this case, we simply use a timer:
335 my $w = AnyEvent->timer (
336 after => 1,
337 cb => sub { $result_ready->broadcast },
338 );
205 339
340 # this "blocks" (while handling events) till the watcher
341 # calls broadcast
206 $result_ready->wait; 342 $result_ready->wait;
207 343
208=back 344=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
237 345
238=over 4 346=over 4
239 347
240=item $AnyEvent::MODEL 348=item $AnyEvent::MODEL
241 349
… …
246AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>). 354AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).
247 355
248The known classes so far are: 356The known classes so far are:
249 357
250 AnyEvent::Impl::CoroEV based on Coro::EV, best choice. 358 AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
251 AnyEvent::Impl::EV based on EV (an interface to libev, also best choice).
252 AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice. 359 AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
360 AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
253 AnyEvent::Impl::Event based on Event, also second best choice :) 361 AnyEvent::Impl::Event based on Event, second best choice.
254 AnyEvent::Impl::Glib based on Glib, second-best choice. 362 AnyEvent::Impl::Glib based on Glib, third-best choice.
255 AnyEvent::Impl::Tk based on Tk, very bad choice. 363 AnyEvent::Impl::Tk based on Tk, very bad choice.
256 AnyEvent::Impl::Perl pure-perl implementation, inefficient. 364 AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
365 AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
366 AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
257 367
258=item AnyEvent::detect 368=item AnyEvent::detect
259 369
260Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model if 370Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
261necessary. You should only call this function right before you would have 371if necessary. You should only call this function right before you would
262created an AnyEvent watcher anyway, that is, very late at runtime. 372have created an AnyEvent watcher anyway, that is, as late as possible at
373runtime.
263 374
264=back 375=back
265 376
266=head1 WHAT TO DO IN A MODULE 377=head1 WHAT TO DO IN A MODULE
267 378
268As a module author, you should "use AnyEvent" and call AnyEvent methods 379As 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. 380freely, but you should not load a specific event module or rely on it.
270 381
271Be careful when you create watchers in the module body - Anyevent will 382Be 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 383decide 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 384by calling AnyEvent in your module body you force the user of your module
274to load the event module first. 385to load the event module first.
275 386
387Never call C<< ->wait >> on a condition variable unless you I<know> that
388the C<< ->broadcast >> method has been called on it already. This is
389because it will stall the whole program, and the whole point of using
390events is to stay interactive.
391
392It is fine, however, to call C<< ->wait >> when the user of your module
393requests it (i.e. if you create a http request object ad have a method
394called C<results> that returns the results, it should call C<< ->wait >>
395freely, as the user of your module knows what she is doing. always).
396
276=head1 WHAT TO DO IN THE MAIN PROGRAM 397=head1 WHAT TO DO IN THE MAIN PROGRAM
277 398
278There will always be a single main program - the only place that should 399There will always be a single main program - the only place that should
279dictate which event model to use. 400dictate which event model to use.
280 401
281If it doesn't care, it can just "use AnyEvent" and use it itself, or not 402If 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. 403do anything special (it does not need to be event-based) and let AnyEvent
404decide which implementation to chose if some module relies on it.
283 405
284If the main program relies on a specific event model (for example, in Gtk2 406If 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 407Gtk2 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 408event module before loading AnyEvent or any module that uses it: generally
287as possible. The reason is that modules might create watchers when they 409speaking, 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 410modules might create watchers when they are loaded, and AnyEvent will
289it creates watchers, and it might chose the wrong one unless you load the 411decide on the event model to use as soon as it creates watchers, and it
290correct one yourself. 412might chose the wrong one unless you load the correct one yourself.
291 413
292You can chose to use a rather inefficient pure-perl implementation by 414You can chose to use a rather inefficient pure-perl implementation by
293loading the C<AnyEvent::Impl::Perl> module, but letting AnyEvent chose is 415loading the C<AnyEvent::Impl::Perl> module, which gives you similar
294generally better. 416behaviour everywhere, but letting AnyEvent chose is generally better.
295 417
296=cut 418=cut
297 419
298package AnyEvent; 420package AnyEvent;
299 421
300no warnings; 422no warnings;
301use strict; 423use strict;
302 424
303use Carp; 425use Carp;
304 426
305our $VERSION = '3.0'; 427our $VERSION = '3.2';
306our $MODEL; 428our $MODEL;
307 429
308our $AUTOLOAD; 430our $AUTOLOAD;
309our @ISA; 431our @ISA;
310 432
… …
312 434
313our @REGISTRY; 435our @REGISTRY;
314 436
315my @models = ( 437my @models = (
316 [Coro::EV:: => AnyEvent::Impl::CoroEV::], 438 [Coro::EV:: => AnyEvent::Impl::CoroEV::],
439 [Coro::Event:: => AnyEvent::Impl::CoroEvent::],
317 [EV:: => AnyEvent::Impl::EV::], 440 [EV:: => AnyEvent::Impl::EV::],
318 [Coro::Event:: => AnyEvent::Impl::CoroEvent::],
319 [Event:: => AnyEvent::Impl::Event::], 441 [Event:: => AnyEvent::Impl::Event::],
320 [Glib:: => AnyEvent::Impl::Glib::], 442 [Glib:: => AnyEvent::Impl::Glib::],
321 [Tk:: => AnyEvent::Impl::Tk::], 443 [Tk:: => AnyEvent::Impl::Tk::],
322 [AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::], 444 [AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
323); 445);
446my @models_detect = (
447 [Qt:: => AnyEvent::Impl::Qt::], # requires special main program
448 [Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
449);
324 450
325our %method = map +($_ => 1), qw(io timer condvar broadcast wait signal one_event DESTROY); 451our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY);
326 452
327sub detect() { 453sub detect() {
328 unless ($MODEL) { 454 unless ($MODEL) {
329 no strict 'refs'; 455 no strict 'refs';
330 456
457 if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
458 my $model = "AnyEvent::Impl::$1";
459 if (eval "require $model") {
460 $MODEL = $model;
461 warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;
462 }
463 }
464
331 # check for already loaded models 465 # check for already loaded models
466 unless ($MODEL) {
332 for (@REGISTRY, @models) { 467 for (@REGISTRY, @models, @models_detect) {
333 my ($package, $model) = @$_; 468 my ($package, $model) = @$_;
334 if (${"$package\::VERSION"} > 0) { 469 if (${"$package\::VERSION"} > 0) {
335 if (eval "require $model") { 470 if (eval "require $model") {
336 $MODEL = $model; 471 $MODEL = $model;
337 warn "AnyEvent: found model '$model', using it.\n" if $verbose > 1; 472 warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;
338 last; 473 last;
474 }
339 } 475 }
340 } 476 }
341 }
342 477
343 unless ($MODEL) { 478 unless ($MODEL) {
344 # try to load a model 479 # try to load a model
345 480
346 for (@REGISTRY, @models) { 481 for (@REGISTRY, @models) {
347 my ($package, $model) = @$_; 482 my ($package, $model) = @$_;
348 if (eval "require $package" 483 if (eval "require $package"
349 and ${"$package\::VERSION"} > 0 484 and ${"$package\::VERSION"} > 0
350 and eval "require $model") { 485 and eval "require $model") {
351 $MODEL = $model; 486 $MODEL = $model;
352 warn "AnyEvent: autoprobed and loaded model '$model', using it.\n" if $verbose > 1; 487 warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;
353 last; 488 last;
489 }
354 } 490 }
491
492 $MODEL
493 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 } 494 }
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 } 495 }
360 496
361 unshift @ISA, $MODEL; 497 unshift @ISA, $MODEL;
362 push @{"$MODEL\::ISA"}, "AnyEvent::Base"; 498 push @{"$MODEL\::ISA"}, "AnyEvent::Base";
363 } 499 }
… …
474 undef $CHLD_W unless keys %PID_CB; 610 undef $CHLD_W unless keys %PID_CB;
475} 611}
476 612
477=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE 613=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
478 614
615This is an advanced topic that you do not normally need to use AnyEvent in
616a module. This section is only of use to event loop authors who want to
617provide AnyEvent compatibility.
618
479If you need to support another event library which isn't directly 619If you need to support another event library which isn't directly
480supported by AnyEvent, you can supply your own interface to it by 620supported by AnyEvent, you can supply your own interface to it by
481pushing, before the first watcher gets created, the package name of 621pushing, before the first watcher gets created, the package name of
482the event module and the package name of the interface to use onto 622the event module and the package name of the interface to use onto
483C<@AnyEvent::REGISTRY>. You can do that before and even without loading 623C<@AnyEvent::REGISTRY>. You can do that before and even without loading
484AnyEvent. 624AnyEvent, so it is reasonably cheap.
485 625
486Example: 626Example:
487 627
488 push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::]; 628 push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];
489 629
490This tells AnyEvent to (literally) use the C<urxvt::anyevent::> 630This tells AnyEvent to (literally) use the C<urxvt::anyevent::>
491package/class when it finds the C<urxvt> package/module is loaded. When 631package/class when it finds the C<urxvt> package/module is already loaded.
632
492AnyEvent is loaded and asked to find a suitable event model, it will 633When AnyEvent is loaded and asked to find a suitable event model, it
493first check for the presence of urxvt. 634will first check for the presence of urxvt by trying to C<use> the
635C<urxvt::anyevent> module.
494 636
495The class should provide implementations for all watcher types (see 637The class should provide implementations for all watcher types. See
496L<AnyEvent::Impl::Event> (source code), L<AnyEvent::Impl::Glib> 638L<AnyEvent::Impl::EV> (source code), L<AnyEvent::Impl::Glib> (Source code)
497(Source code) and so on for actual examples, use C<perldoc -m 639and so on for actual examples. Use C<perldoc -m AnyEvent::Impl::Glib> to
498AnyEvent::Impl::Glib> to see the sources). 640see the sources.
499 641
642If you don't provide C<signal> and C<child> watchers than AnyEvent will
643provide suitable (hopefully) replacements.
644
500The above isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt) 645The 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 646terminal emulator uses the above line as-is. An interface isn't included
502because it doesn't make sense outside the embedded interpreter inside 647in AnyEvent because it doesn't make sense outside the embedded interpreter
503I<rxvt-unicode>, and it is updated and maintained as part of the 648inside I<rxvt-unicode>, and it is updated and maintained as part of the
504I<rxvt-unicode> distribution. 649I<rxvt-unicode> distribution.
505 650
506I<rxvt-unicode> also cheats a bit by not providing blocking access to 651I<rxvt-unicode> also cheats a bit by not providing blocking access to
507condition variables: code blocking while waiting for a condition will 652condition variables: code blocking while waiting for a condition will
508C<die>. This still works with most modules/usages, and blocking calls must 653C<die>. This still works with most modules/usages, and blocking calls must
509not be in an interactive application, so it makes sense. 654not be done in an interactive application, so it makes sense.
510 655
511=head1 ENVIRONMENT VARIABLES 656=head1 ENVIRONMENT VARIABLES
512 657
513The following environment variables are used by this module: 658The following environment variables are used by this module:
514 659
515C<PERL_ANYEVENT_VERBOSE> when set to C<2> or higher, reports which event 660=over 4
516model gets used.
517 661
662=item C<PERL_ANYEVENT_VERBOSE>
663
664When set to C<2> or higher, cause AnyEvent to report to STDERR which event
665model it chooses.
666
667=item C<PERL_ANYEVENT_MODEL>
668
669This can be used to specify the event model to be used by AnyEvent, before
670autodetection and -probing kicks in. It must be a string consisting
671entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
672and the resulting module name is loaded and if the load was successful,
673used as event model. If it fails to load AnyEvent will proceed with
674autodetection and -probing.
675
676This functionality might change in future versions.
677
678For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
679could start your program like this:
680
681 PERL_ANYEVENT_MODEL=Perl perl ...
682
683=back
684
518=head1 EXAMPLE 685=head1 EXAMPLE PROGRAM
519 686
520The following program uses an io watcher to read data from stdin, a timer 687The 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 688to display a message once per second, and a condition variable to quit the
522when the user enters quit: 689program when the user enters quit:
523 690
524 use AnyEvent; 691 use AnyEvent;
525 692
526 my $cv = AnyEvent->condvar; 693 my $cv = AnyEvent->condvar;
527 694
528 my $io_watcher = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub { 695 my $io_watcher = AnyEvent->io (
696 fh => \*STDIN,
697 poll => 'r',
698 cb => sub {
529 warn "io event <$_[0]>\n"; # will always output <r> 699 warn "io event <$_[0]>\n"; # will always output <r>
530 chomp (my $input = <STDIN>); # read a line 700 chomp (my $input = <STDIN>); # read a line
531 warn "read: $input\n"; # output what has been read 701 warn "read: $input\n"; # output what has been read
532 $cv->broadcast if $input =~ /^q/i; # quit program if /^q/i 702 $cv->broadcast if $input =~ /^q/i; # quit program if /^q/i
703 },
533 }); 704 );
534 705
535 my $time_watcher; # can only be used once 706 my $time_watcher; # can only be used once
536 707
537 sub new_timer { 708 sub new_timer {
538 $timer = AnyEvent->timer (after => 1, cb => sub { 709 $timer = AnyEvent->timer (after => 1, cb => sub {
… …
620 $txn->{finished}->wait; 791 $txn->{finished}->wait;
621 return $txn->{result}; 792 return $txn->{result};
622 793
623The actual code goes further and collects all errors (C<die>s, exceptions) 794The actual code goes further and collects all errors (C<die>s, exceptions)
624that occured during request processing. The C<result> method detects 795that occured during request processing. The C<result> method detects
625wether an exception as thrown (it is stored inside the $txn object) 796whether an exception as thrown (it is stored inside the $txn object)
626and just throws the exception, which means connection errors and other 797and 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 798problems get reported tot he code that tries to use the result, not in a
628random callback. 799random callback.
629 800
630All of this enables the following usage styles: 801All of this enables the following usage styles:
631 802
6321. Blocking: 8031. Blocking:
633 804
634 my $data = $fcp->client_get ($url); 805 my $data = $fcp->client_get ($url);
635 806
6362. Blocking, but parallelizing: 8072. Blocking, but running in parallel:
637 808
638 my @datas = map $_->result, 809 my @datas = map $_->result,
639 map $fcp->txn_client_get ($_), 810 map $fcp->txn_client_get ($_),
640 @urls; 811 @urls;
641 812
642Both blocking examples work without the module user having to know 813Both blocking examples work without the module user having to know
643anything about events. 814anything about events.
644 815
6453a. Event-based in a main program, using any support Event module: 8163a. Event-based in a main program, using any supported event module:
646 817
647 use Event; 818 use EV;
648 819
649 $fcp->txn_client_get ($url)->cb (sub { 820 $fcp->txn_client_get ($url)->cb (sub {
650 my $txn = shift; 821 my $txn = shift;
651 my $data = $txn->result; 822 my $data = $txn->result;
652 ... 823 ...
653 }); 824 });
654 825
655 Event::loop; 826 EV::loop;
656 827
6573b. The module user could use AnyEvent, too: 8283b. The module user could use AnyEvent, too:
658 829
659 use AnyEvent; 830 use AnyEvent;
660 831
… …
665 $quit->broadcast; 836 $quit->broadcast;
666 }); 837 });
667 838
668 $quit->wait; 839 $quit->wait;
669 840
841=head1 FORK
842
843Most event libraries are not fork-safe. The ones who are usually are
844because they are so inefficient. Only L<EV> is fully fork-aware.
845
846If you have to fork, you must either do so I<before> creating your first
847watcher OR you must not use AnyEvent at all in the child.
848
849=head1 SECURITY CONSIDERATIONS
850
851AnyEvent can be forced to load any event model via
852$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to
853execute arbitrary code or directly gain access, it can easily be used to
854make the program hang or malfunction in subtle ways, as AnyEvent watchers
855will not be active when the program uses a different event model than
856specified in the variable.
857
858You can make AnyEvent completely ignore this variable by deleting it
859before the first watcher gets created, e.g. with a C<BEGIN> block:
860
861 BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
862
863 use AnyEvent;
864
670=head1 SEE ALSO 865=head1 SEE ALSO
671 866
672Event modules: L<Coro::Event>, L<Coro>, L<Event>, L<Glib::Event>, L<Glib>. 867Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,
868L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,
869L<Event::Lib>, L<Qt>.
673 870
871Implementations: 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>. 872L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,
873L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,
874L<AnyEvent::Impl::Qt>.
675 875
676Nontrivial usage example: L<Net::FCP>. 876Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.
677 877
678=head1 878=head1 AUTHOR
879
880 Marc Lehmann <schmorp@schmorp.de>
881 http://home.schmorp.de/
679 882
680=cut 883=cut
681 884
6821 8851
683 886

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