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Revision 1.61 by root, Fri Apr 25 01:55:25 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
5EV, Event, Coro::EV, Coro::Event, Glib, Tk, Perl - various supported event loops 5EV, Event, Coro::EV, Coro::Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event loops
6 6
7=head1 SYNOPSIS 7=head1 SYNOPSIS
8 8
9 use AnyEvent; 9 use AnyEvent;
10 10
… …
14 14
15 my $w = AnyEvent->timer (after => $seconds, cb => sub { 15 my $w = AnyEvent->timer (after => $seconds, cb => sub {
16 ... 16 ...
17 }); 17 });
18 18
19 my $w = AnyEvent->condvar; # stores wether a condition was flagged 19 my $w = AnyEvent->condvar; # stores whether a condition was flagged
20 $w->wait; # enters "main loop" till $condvar gets ->broadcast 20 $w->wait; # enters "main loop" till $condvar gets ->broadcast
21 $w->broadcast; # wake up current and all future wait's 21 $w->broadcast; # wake up current and all future wait's
22 22
23=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT) 23=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
24 24
… …
29policy> and AnyEvent is I<small and efficient>. 29policy> and AnyEvent is I<small and efficient>.
30 30
31First and foremost, I<AnyEvent is not an event model> itself, it only 31First and foremost, I<AnyEvent is not an event model> itself, it only
32interfaces to whatever event model the main program happens to use in a 32interfaces to whatever event model the main program happens to use in a
33pragmatic way. For event models and certain classes of immortals alike, 33pragmatic way. For event models and certain classes of immortals alike,
34the statement "there can only be one" is a bitter reality, and AnyEvent 34the statement "there can only be one" is a bitter reality: In general,
35helps hiding the differences. 35only one event loop can be active at the same time in a process. AnyEvent
36helps hiding the differences between those event loops.
36 37
37The goal of AnyEvent is to offer module authors the ability to do event 38The goal of AnyEvent is to offer module authors the ability to do event
38programming (waiting for I/O or timer events) without subscribing to a 39programming (waiting for I/O or timer events) without subscribing to a
39religion, a way of living, and most importantly: without forcing your 40religion, a way of living, and most importantly: without forcing your
40module users into the same thing by forcing them to use the same event 41module users into the same thing by forcing them to use the same event
41model you use. 42model you use.
42 43
43For modules like POE or IO::Async (which is actually doing all I/O 44For modules like POE or IO::Async (which is a total misnomer as it is
44I<synchronously>...), using them in your module is like joining a 45actually doing all I/O I<synchronously>...), using them in your module is
45cult: After you joined, you are dependent on them and you cannot use 46like joining a cult: After you joined, you are dependent on them and you
46anything else, as it is simply incompatible to everything that isn't 47cannot use anything else, as it is simply incompatible to everything that
47itself. 48isn't itself. What's worse, all the potential users of your module are
49I<also> forced to use the same event loop you use.
48 50
49AnyEvent + POE works fine. AnyEvent + Glib works fine. AnyEvent + Tk 51AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
50works fine etc. etc. but none of these work together with the rest: POE 52fine. AnyEvent + Tk works fine etc. etc. but none of these work together
51+ IO::Async? no go. Tk + Event? no go. If your module uses one of 53with the rest: POE + IO::Async? no go. Tk + Event? no go. Again: if
52those, every user of your module has to use it, too. If your module 54your module uses one of those, every user of your module has to use it,
53uses AnyEvent, it works transparently with all event models it supports 55too. But if your module uses AnyEvent, it works transparently with all
54(including stuff like POE and IO::Async). 56event models it supports (including stuff like POE and IO::Async, as long
57as those use one of the supported event loops. It is trivial to add new
58event loops to AnyEvent, too, so it is future-proof).
55 59
56In addition of being free of having to use I<the one and only true event 60In addition to being free of having to use I<the one and only true event
57model>, AnyEvent also is free of bloat and policy: with POE or similar 61model>, AnyEvent also is free of bloat and policy: with POE or similar
58modules, you get an enourmous amount of code and strict rules you have 62modules, you get an enourmous amount of code and strict rules you have to
59to follow. AnyEvent, on the other hand, is lean and to the point by only 63follow. AnyEvent, on the other hand, is lean and up to the point, by only
60offering the functionality that is useful, in as thin as a wrapper as 64offering the functionality that is necessary, in as thin as a wrapper as
61technically possible. 65technically possible.
62 66
63Of course, if you want lots of policy (this can arguably be somewhat 67Of course, if you want lots of policy (this can arguably be somewhat
64useful) and you want to force your users to use the one and only event 68useful) and you want to force your users to use the one and only event
65model, you should I<not> use this module. 69model, you should I<not> use this module.
… …
70L<AnyEvent> provides an identical interface to multiple event loops. This 74L<AnyEvent> provides an identical interface to multiple event loops. This
71allows module authors to utilise an event loop without forcing module 75allows module authors to utilise an event loop without forcing module
72users to use the same event loop (as only a single event loop can coexist 76users to use the same event loop (as only a single event loop can coexist
73peacefully at any one time). 77peacefully at any one time).
74 78
75The interface itself is vaguely similar but not identical to the Event 79The interface itself is vaguely similar, but not identical to the L<Event>
76module. 80module.
77 81
78On the first call of any method, the module tries to detect the currently 82During the first call of any watcher-creation method, the module tries
79loaded event loop by probing wether any of the following modules is 83to detect the currently loaded event loop by probing whether one of the
80loaded: L<Coro::EV>, L<Coro::Event>, L<EV>, L<Event>, L<Glib>, L<Tk>. The 84following modules is already loaded: L<Coro::EV>, L<Coro::Event>, L<EV>,
85L<Event>, L<Glib>, L<Tk>, L<AnyEvent::Impl::Perl>, L<Event::Lib>, L<Qt>,
81first one found is used. If none are found, the module tries to load these 86L<POE>. The first one found is used. If none are found, the module tries
82modules in the order given. The first one that could be successfully 87to load these modules (excluding Event::Lib, Qt and POE as the pure perl
83loaded will be used. If still none could be found, AnyEvent will fall back 88adaptor should always succeed) in the order given. The first one that can
84to a pure-perl event loop, which is also not very efficient. 89be successfully loaded will be used. If, after this, still none could be
90found, AnyEvent will fall back to a pure-perl event loop, which is not
91very efficient, but should work everywhere.
85 92
86Because AnyEvent first checks for modules that are already loaded, loading 93Because AnyEvent first checks for modules that are already loaded, loading
87an Event model explicitly before first using AnyEvent will likely make 94an event model explicitly before first using AnyEvent will likely make
88that model the default. For example: 95that model the default. For example:
89 96
90 use Tk; 97 use Tk;
91 use AnyEvent; 98 use AnyEvent;
92 99
93 # .. AnyEvent will likely default to Tk 100 # .. AnyEvent will likely default to Tk
101
102The I<likely> means that, if any module loads another event model and
103starts using it, all bets are off. Maybe you should tell their authors to
104use AnyEvent so their modules work together with others seamlessly...
94 105
95The pure-perl implementation of AnyEvent is called 106The pure-perl implementation of AnyEvent is called
96C<AnyEvent::Impl::Perl>. Like other event modules you can load it 107C<AnyEvent::Impl::Perl>. Like other event modules you can load it
97explicitly. 108explicitly.
98 109
… …
101AnyEvent has the central concept of a I<watcher>, which is an object that 112AnyEvent has the central concept of a I<watcher>, which is an object that
102stores relevant data for each kind of event you are waiting for, such as 113stores relevant data for each kind of event you are waiting for, such as
103the callback to call, the filehandle to watch, etc. 114the callback to call, the filehandle to watch, etc.
104 115
105These watchers are normal Perl objects with normal Perl lifetime. After 116These watchers are normal Perl objects with normal Perl lifetime. After
106creating a watcher it will immediately "watch" for events and invoke 117creating a watcher it will immediately "watch" for events and invoke the
118callback when the event occurs (of course, only when the event model
119is in control).
120
107the callback. To disable the watcher you have to destroy it (e.g. by 121To disable the watcher you have to destroy it (e.g. by setting the
108setting the variable that stores it to C<undef> or otherwise deleting all 122variable you store it in to C<undef> or otherwise deleting all references
109references to it). 123to it).
110 124
111All watchers are created by calling a method on the C<AnyEvent> class. 125All watchers are created by calling a method on the C<AnyEvent> class.
112 126
127Many watchers either are used with "recursion" (repeating timers for
128example), or need to refer to their watcher object in other ways.
129
130An any way to achieve that is this pattern:
131
132 my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
133 # you can use $w here, for example to undef it
134 undef $w;
135 });
136
137Note that C<my $w; $w => combination. This is necessary because in Perl,
138my variables are only visible after the statement in which they are
139declared.
140
113=head2 IO WATCHERS 141=head2 IO WATCHERS
114 142
115You can create I/O watcher by calling the C<< AnyEvent->io >> method with 143You can create an I/O watcher by calling the C<< AnyEvent->io >> method
116the following mandatory arguments: 144with the following mandatory key-value pairs as arguments:
117 145
118C<fh> the Perl I<filehandle> (not filedescriptor) to watch for 146C<fh> the Perl I<file handle> (I<not> file descriptor) to watch for
119events. C<poll> must be a string that is either C<r> or C<w>, that creates 147events. C<poll> must be a string that is either C<r> or C<w>, which
120a watcher waiting for "r"eadable or "w"ritable events. C<cb> the callback 148creates a watcher waiting for "r"eadable or "w"ritable events,
121to invoke everytime the filehandle becomes ready. 149respectively. C<cb> is the callback to invoke each time the file handle
150becomes ready.
122 151
123Filehandles will be kept alive, so as long as the watcher exists, the 152As long as the I/O watcher exists it will keep the file descriptor or a
124filehandle exists, too. 153copy of it alive/open.
154
155It is not allowed to close a file handle as long as any watcher is active
156on the underlying file descriptor.
157
158Some event loops issue spurious readyness notifications, so you should
159always use non-blocking calls when reading/writing from/to your file
160handles.
125 161
126Example: 162Example:
127 163
128 # wait for readability of STDIN, then read a line and disable the watcher 164 # wait for readability of STDIN, then read a line and disable the watcher
129 my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub { 165 my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
… …
135=head2 TIME WATCHERS 171=head2 TIME WATCHERS
136 172
137You can create a time watcher by calling the C<< AnyEvent->timer >> 173You can create a time watcher by calling the C<< AnyEvent->timer >>
138method with the following mandatory arguments: 174method with the following mandatory arguments:
139 175
140C<after> after how many seconds (fractions are supported) should the timer 176C<after> specifies after how many seconds (fractional values are
141activate. C<cb> the callback to invoke. 177supported) should the timer activate. C<cb> the callback to invoke in that
178case.
142 179
143The timer callback will be invoked at most once: if you want a repeating 180The timer callback will be invoked at most once: if you want a repeating
144timer you have to create a new watcher (this is a limitation by both Tk 181timer you have to create a new watcher (this is a limitation by both Tk
145and Glib). 182and Glib).
146 183
… …
152 }); 189 });
153 190
154 # to cancel the timer: 191 # to cancel the timer:
155 undef $w; 192 undef $w;
156 193
194Example 2:
195
196 # fire an event after 0.5 seconds, then roughly every second
197 my $w;
198
199 my $cb = sub {
200 # cancel the old timer while creating a new one
201 $w = AnyEvent->timer (after => 1, cb => $cb);
202 };
203
204 # start the "loop" by creating the first watcher
205 $w = AnyEvent->timer (after => 0.5, cb => $cb);
206
207=head3 TIMING ISSUES
208
209There are two ways to handle timers: based on real time (relative, "fire
210in 10 seconds") and based on wallclock time (absolute, "fire at 12
211o'clock").
212
213While most event loops expect timers to specified in a relative way, they
214use absolute time internally. This makes a difference when your clock
215"jumps", for example, when ntp decides to set your clock backwards from
216the wrong date of 2014-01-01 to 2008-01-01, a watcher that is supposed to
217fire "after" a second might actually take six years to finally fire.
218
219AnyEvent cannot compensate for this. The only event loop that is conscious
220about these issues is L<EV>, which offers both relative (ev_timer, based
221on true relative time) and absolute (ev_periodic, based on wallclock time)
222timers.
223
224AnyEvent always prefers relative timers, if available, matching the
225AnyEvent API.
226
227=head2 SIGNAL WATCHERS
228
229You can watch for signals using a signal watcher, C<signal> is the signal
230I<name> without any C<SIG> prefix, C<cb> is the Perl callback to
231be invoked whenever a signal occurs.
232
233Multiple signal occurances can be clumped together into one callback
234invocation, and callback invocation will be synchronous. synchronous means
235that it might take a while until the signal gets handled by the process,
236but it is guarenteed not to interrupt any other callbacks.
237
238The main advantage of using these watchers is that you can share a signal
239between multiple watchers.
240
241This watcher might use C<%SIG>, so programs overwriting those signals
242directly will likely not work correctly.
243
244Example: exit on SIGINT
245
246 my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
247
248=head2 CHILD PROCESS WATCHERS
249
250You can also watch on a child process exit and catch its exit status.
251
252The child process is specified by the C<pid> argument (if set to C<0>, it
253watches for any child process exit). The watcher will trigger as often
254as status change for the child are received. This works by installing a
255signal handler for C<SIGCHLD>. The callback will be called with the pid
256and exit status (as returned by waitpid).
257
258Example: wait for pid 1333
259
260 my $w = AnyEvent->child (
261 pid => 1333,
262 cb => sub {
263 my ($pid, $status) = @_;
264 warn "pid $pid exited with status $status";
265 },
266 );
267
157=head2 CONDITION WATCHERS 268=head2 CONDITION VARIABLES
158 269
159Condition watchers can be created by calling the C<< AnyEvent->condvar >> 270Condition variables can be created by calling the C<< AnyEvent->condvar >>
160method without any arguments. 271method without any arguments.
161 272
162A condition watcher watches for a condition - precisely that the C<< 273A condition variable waits for a condition - precisely that the C<<
163->broadcast >> method has been called. 274->broadcast >> method has been called.
164 275
276They are very useful to signal that a condition has been fulfilled, for
277example, if you write a module that does asynchronous http requests,
278then a condition variable would be the ideal candidate to signal the
279availability of results.
280
281You can also use condition variables to block your main program until
282an event occurs - for example, you could C<< ->wait >> in your main
283program until the user clicks the Quit button in your app, which would C<<
284->broadcast >> the "quit" event.
285
165Note that condition watchers recurse into the event loop - if you have 286Note that condition variables recurse into the event loop - if you have
166two watchers that call C<< ->wait >> in a round-robbin fashion, you 287two pirces of code that call C<< ->wait >> in a round-robbin fashion, you
167lose. Therefore, condition watchers are good to export to your caller, but 288lose. Therefore, condition variables are good to export to your caller, but
168you should avoid making a blocking wait, at least in callbacks, as this 289you should avoid making a blocking wait yourself, at least in callbacks,
169usually asks for trouble. 290as this asks for trouble.
170 291
171The watcher has only two methods: 292This object has two methods:
172 293
173=over 4 294=over 4
174 295
175=item $cv->wait 296=item $cv->wait
176 297
… …
179 300
180You can only wait once on a condition - additional calls will return 301You can only wait once on a condition - additional calls will return
181immediately. 302immediately.
182 303
183Not all event models support a blocking wait - some die in that case 304Not all event models support a blocking wait - some die in that case
184(programs might want to do that so they stay interactive), so I<if you 305(programs might want to do that to stay interactive), so I<if you are
185are using this from a module, never require a blocking wait>, but let the 306using this from a module, never require a blocking wait>, but let the
186caller decide wether the call will block or not (for example, by coupling 307caller decide whether the call will block or not (for example, by coupling
187condition variables with some kind of request results and supporting 308condition variables with some kind of request results and supporting
188callbacks so the caller knows that getting the result will not block, 309callbacks so the caller knows that getting the result will not block,
189while still suppporting blocking waits if the caller so desires). 310while still suppporting blocking waits if the caller so desires).
190 311
191Another reason I<never> to C<< ->wait >> in a module is that you cannot 312Another reason I<never> to C<< ->wait >> in a module is that you cannot
192sensibly have two C<< ->wait >>'s in parallel, as that would require 313sensibly have two C<< ->wait >>'s in parallel, as that would require
193multiple interpreters or coroutines/threads, none of which C<AnyEvent> 314multiple interpreters or coroutines/threads, none of which C<AnyEvent>
194can supply (the coroutine-aware backends C<Coro::EV> and C<Coro::Event> 315can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and
195explicitly support concurrent C<< ->wait >>'s from different coroutines, 316L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
196however). 317from different coroutines, however).
197 318
198=item $cv->broadcast 319=item $cv->broadcast
199 320
200Flag the condition as ready - a running C<< ->wait >> and all further 321Flag the condition as ready - a running C<< ->wait >> and all further
201calls to C<wait> will return after this method has been called. If nobody 322calls to C<wait> will (eventually) return after this method has been
202is waiting the broadcast will be remembered.. 323called. If nobody is waiting the broadcast will be remembered..
324
325=back
203 326
204Example: 327Example:
205 328
206 # wait till the result is ready 329 # wait till the result is ready
207 my $result_ready = AnyEvent->condvar; 330 my $result_ready = AnyEvent->condvar;
208 331
209 # do something such as adding a timer 332 # do something such as adding a timer
210 # or socket watcher the calls $result_ready->broadcast 333 # or socket watcher the calls $result_ready->broadcast
211 # when the "result" is ready. 334 # when the "result" is ready.
335 # in this case, we simply use a timer:
336 my $w = AnyEvent->timer (
337 after => 1,
338 cb => sub { $result_ready->broadcast },
339 );
212 340
341 # this "blocks" (while handling events) till the watcher
342 # calls broadcast
213 $result_ready->wait; 343 $result_ready->wait;
214 344
215=back 345=head1 GLOBAL VARIABLES AND FUNCTIONS
216
217=head2 SIGNAL WATCHERS
218
219You can listen for signals using a signal watcher, C<signal> is the signal
220I<name> without any C<SIG> prefix. Multiple signals events can be clumped
221together into one callback invocation, and callback invocation might or
222might not be asynchronous.
223
224These watchers might use C<%SIG>, so programs overwriting those signals
225directly will likely not work correctly.
226
227Example: exit on SIGINT
228
229 my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
230
231=head2 CHILD PROCESS WATCHERS
232
233You can also listen for the status of a child process specified by the
234C<pid> argument (or any child if the pid argument is 0). The watcher will
235trigger as often as status change for the child are received. This works
236by installing a signal handler for C<SIGCHLD>. The callback will be called with
237the pid and exit status (as returned by waitpid).
238
239Example: wait for pid 1333
240
241 my $w = AnyEvent->child (pid => 1333, cb => sub { warn "exit status $?" });
242
243=head1 GLOBALS
244 346
245=over 4 347=over 4
246 348
247=item $AnyEvent::MODEL 349=item $AnyEvent::MODEL
248 350
… …
254 356
255The known classes so far are: 357The known classes so far are:
256 358
257 AnyEvent::Impl::CoroEV based on Coro::EV, best choice. 359 AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
258 AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice. 360 AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
259 AnyEvent::Impl::EV based on EV (an interface to libev, also best choice). 361 AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
260 AnyEvent::Impl::Event based on Event, also second best choice :) 362 AnyEvent::Impl::Event based on Event, second best choice.
261 AnyEvent::Impl::Glib based on Glib, third-best choice. 363 AnyEvent::Impl::Glib based on Glib, third-best choice.
262 AnyEvent::Impl::Tk based on Tk, very bad choice. 364 AnyEvent::Impl::Tk based on Tk, very bad choice.
263 AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable. 365 AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
366 AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
367 AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
368 AnyEvent::Impl::POE based on POE, not generic enough for full support.
369
370There is no support for WxWidgets, as WxWidgets has no support for
371watching file handles. However, you can use WxWidgets through the
372POE Adaptor, as POE has a Wx backend that simply polls 20 times per
373second, which was considered to be too horrible to even consider for
374AnyEvent. Likewise, other POE backends can be used by Anyevent by using
375it's adaptor.
264 376
265=item AnyEvent::detect 377=item AnyEvent::detect
266 378
267Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model if 379Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
268necessary. You should only call this function right before you would have 380if necessary. You should only call this function right before you would
269created an AnyEvent watcher anyway, that is, very late at runtime. 381have created an AnyEvent watcher anyway, that is, as late as possible at
382runtime.
270 383
271=back 384=back
272 385
273=head1 WHAT TO DO IN A MODULE 386=head1 WHAT TO DO IN A MODULE
274 387
275As a module author, you should "use AnyEvent" and call AnyEvent methods 388As a module author, you should C<use AnyEvent> and call AnyEvent methods
276freely, but you should not load a specific event module or rely on it. 389freely, but you should not load a specific event module or rely on it.
277 390
278Be careful when you create watchers in the module body - Anyevent will 391Be careful when you create watchers in the module body - AnyEvent will
279decide which event module to use as soon as the first method is called, so 392decide which event module to use as soon as the first method is called, so
280by calling AnyEvent in your module body you force the user of your module 393by calling AnyEvent in your module body you force the user of your module
281to load the event module first. 394to load the event module first.
282 395
396Never call C<< ->wait >> on a condition variable unless you I<know> that
397the C<< ->broadcast >> method has been called on it already. This is
398because it will stall the whole program, and the whole point of using
399events is to stay interactive.
400
401It is fine, however, to call C<< ->wait >> when the user of your module
402requests it (i.e. if you create a http request object ad have a method
403called C<results> that returns the results, it should call C<< ->wait >>
404freely, as the user of your module knows what she is doing. always).
405
283=head1 WHAT TO DO IN THE MAIN PROGRAM 406=head1 WHAT TO DO IN THE MAIN PROGRAM
284 407
285There will always be a single main program - the only place that should 408There will always be a single main program - the only place that should
286dictate which event model to use. 409dictate which event model to use.
287 410
288If it doesn't care, it can just "use AnyEvent" and use it itself, or not 411If it doesn't care, it can just "use AnyEvent" and use it itself, or not
289do anything special and let AnyEvent decide which implementation to chose. 412do anything special (it does not need to be event-based) and let AnyEvent
413decide which implementation to chose if some module relies on it.
290 414
291If the main program relies on a specific event model (for example, in Gtk2 415If the main program relies on a specific event model. For example, in
292programs you have to rely on either Glib or Glib::Event), you should load 416Gtk2 programs you have to rely on the Glib module. You should load the
293it before loading AnyEvent or any module that uses it, generally, as early 417event module before loading AnyEvent or any module that uses it: generally
294as possible. The reason is that modules might create watchers when they 418speaking, you should load it as early as possible. The reason is that
295are loaded, and AnyEvent will decide on the event model to use as soon as 419modules might create watchers when they are loaded, and AnyEvent will
296it creates watchers, and it might chose the wrong one unless you load the 420decide on the event model to use as soon as it creates watchers, and it
297correct one yourself. 421might chose the wrong one unless you load the correct one yourself.
298 422
299You can chose to use a rather inefficient pure-perl implementation by 423You can chose to use a rather inefficient pure-perl implementation by
300loading the C<AnyEvent::Impl::Perl> module, but letting AnyEvent chose is 424loading the C<AnyEvent::Impl::Perl> module, which gives you similar
301generally better. 425behaviour everywhere, but letting AnyEvent chose is generally better.
302 426
303=cut 427=cut
304 428
305package AnyEvent; 429package AnyEvent;
306 430
307no warnings; 431no warnings;
308use strict; 432use strict;
309 433
310use Carp; 434use Carp;
311 435
312our $VERSION = '3.0'; 436our $VERSION = '3.2';
313our $MODEL; 437our $MODEL;
314 438
315our $AUTOLOAD; 439our $AUTOLOAD;
316our @ISA; 440our @ISA;
317 441
… …
325 [EV:: => AnyEvent::Impl::EV::], 449 [EV:: => AnyEvent::Impl::EV::],
326 [Event:: => AnyEvent::Impl::Event::], 450 [Event:: => AnyEvent::Impl::Event::],
327 [Glib:: => AnyEvent::Impl::Glib::], 451 [Glib:: => AnyEvent::Impl::Glib::],
328 [Tk:: => AnyEvent::Impl::Tk::], 452 [Tk:: => AnyEvent::Impl::Tk::],
329 [AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::], 453 [AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
454 # everything below here will not be autoprobed as the pureperl backend should work everywhere
455 [Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
456 [Qt:: => AnyEvent::Impl::Qt::], # requires special main program
457 [POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
330); 458);
331 459
332our %method = map +($_ => 1), qw(io timer condvar broadcast wait signal one_event DESTROY); 460our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY);
333 461
334sub detect() { 462sub detect() {
335 unless ($MODEL) { 463 unless ($MODEL) {
336 no strict 'refs'; 464 no strict 'refs';
337 465
466 if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
467 my $model = "AnyEvent::Impl::$1";
468 if (eval "require $model") {
469 $MODEL = $model;
470 warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;
471 } else {
472 warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;
473 }
474 }
475
338 # check for already loaded models 476 # check for already loaded models
477 unless ($MODEL) {
339 for (@REGISTRY, @models) { 478 for (@REGISTRY, @models) {
340 my ($package, $model) = @$_; 479 my ($package, $model) = @$_;
341 if (${"$package\::VERSION"} > 0) { 480 if (${"$package\::VERSION"} > 0) {
342 if (eval "require $model") { 481 if (eval "require $model") {
343 $MODEL = $model; 482 $MODEL = $model;
344 warn "AnyEvent: found model '$model', using it.\n" if $verbose > 1; 483 warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;
345 last; 484 last;
485 }
346 } 486 }
347 } 487 }
348 }
349 488
350 unless ($MODEL) { 489 unless ($MODEL) {
351 # try to load a model 490 # try to load a model
352 491
353 for (@REGISTRY, @models) { 492 for (@REGISTRY, @models) {
354 my ($package, $model) = @$_; 493 my ($package, $model) = @$_;
355 if (eval "require $package" 494 if (eval "require $package"
356 and ${"$package\::VERSION"} > 0 495 and ${"$package\::VERSION"} > 0
357 and eval "require $model") { 496 and eval "require $model") {
358 $MODEL = $model; 497 $MODEL = $model;
359 warn "AnyEvent: autoprobed and loaded model '$model', using it.\n" if $verbose > 1; 498 warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;
360 last; 499 last;
500 }
361 } 501 }
502
503 $MODEL
504 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.";
362 } 505 }
363
364 $MODEL
365 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.";
366 } 506 }
367 507
368 unshift @ISA, $MODEL; 508 unshift @ISA, $MODEL;
369 push @{"$MODEL\::ISA"}, "AnyEvent::Base"; 509 push @{"$MODEL\::ISA"}, "AnyEvent::Base";
370 } 510 }
… …
481 undef $CHLD_W unless keys %PID_CB; 621 undef $CHLD_W unless keys %PID_CB;
482} 622}
483 623
484=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE 624=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
485 625
626This is an advanced topic that you do not normally need to use AnyEvent in
627a module. This section is only of use to event loop authors who want to
628provide AnyEvent compatibility.
629
486If you need to support another event library which isn't directly 630If you need to support another event library which isn't directly
487supported by AnyEvent, you can supply your own interface to it by 631supported by AnyEvent, you can supply your own interface to it by
488pushing, before the first watcher gets created, the package name of 632pushing, before the first watcher gets created, the package name of
489the event module and the package name of the interface to use onto 633the event module and the package name of the interface to use onto
490C<@AnyEvent::REGISTRY>. You can do that before and even without loading 634C<@AnyEvent::REGISTRY>. You can do that before and even without loading
491AnyEvent. 635AnyEvent, so it is reasonably cheap.
492 636
493Example: 637Example:
494 638
495 push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::]; 639 push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];
496 640
497This tells AnyEvent to (literally) use the C<urxvt::anyevent::> 641This tells AnyEvent to (literally) use the C<urxvt::anyevent::>
498package/class when it finds the C<urxvt> package/module is loaded. When 642package/class when it finds the C<urxvt> package/module is already loaded.
643
499AnyEvent is loaded and asked to find a suitable event model, it will 644When AnyEvent is loaded and asked to find a suitable event model, it
500first check for the presence of urxvt. 645will first check for the presence of urxvt by trying to C<use> the
646C<urxvt::anyevent> module.
501 647
502The class should provide implementations for all watcher types (see 648The class should provide implementations for all watcher types. See
503L<AnyEvent::Impl::Event> (source code), L<AnyEvent::Impl::Glib> 649L<AnyEvent::Impl::EV> (source code), L<AnyEvent::Impl::Glib> (Source code)
504(Source code) and so on for actual examples, use C<perldoc -m 650and so on for actual examples. Use C<perldoc -m AnyEvent::Impl::Glib> to
505AnyEvent::Impl::Glib> to see the sources). 651see the sources.
506 652
653If you don't provide C<signal> and C<child> watchers than AnyEvent will
654provide suitable (hopefully) replacements.
655
507The above isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt) 656The above example isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt)
508uses the above line as-is. An interface isn't included in AnyEvent 657terminal emulator uses the above line as-is. An interface isn't included
509because it doesn't make sense outside the embedded interpreter inside 658in AnyEvent because it doesn't make sense outside the embedded interpreter
510I<rxvt-unicode>, and it is updated and maintained as part of the 659inside I<rxvt-unicode>, and it is updated and maintained as part of the
511I<rxvt-unicode> distribution. 660I<rxvt-unicode> distribution.
512 661
513I<rxvt-unicode> also cheats a bit by not providing blocking access to 662I<rxvt-unicode> also cheats a bit by not providing blocking access to
514condition variables: code blocking while waiting for a condition will 663condition variables: code blocking while waiting for a condition will
515C<die>. This still works with most modules/usages, and blocking calls must 664C<die>. This still works with most modules/usages, and blocking calls must
516not be in an interactive application, so it makes sense. 665not be done in an interactive application, so it makes sense.
517 666
518=head1 ENVIRONMENT VARIABLES 667=head1 ENVIRONMENT VARIABLES
519 668
520The following environment variables are used by this module: 669The following environment variables are used by this module:
521 670
522C<PERL_ANYEVENT_VERBOSE> when set to C<2> or higher, reports which event 671=over 4
523model gets used.
524 672
673=item C<PERL_ANYEVENT_VERBOSE>
674
675By default, AnyEvent will be completely silent except in fatal
676conditions. You can set this environment variable to make AnyEvent more
677talkative.
678
679When set to C<1> or higher, causes AnyEvent to warn about unexpected
680conditions, such as not being able to load the event model specified by
681C<PERL_ANYEVENT_MODEL>.
682
683When set to C<2> or higher, cause AnyEvent to report to STDERR which event
684model it chooses.
685
686=item C<PERL_ANYEVENT_MODEL>
687
688This can be used to specify the event model to be used by AnyEvent, before
689autodetection and -probing kicks in. It must be a string consisting
690entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
691and the resulting module name is loaded and if the load was successful,
692used as event model. If it fails to load AnyEvent will proceed with
693autodetection and -probing.
694
695This functionality might change in future versions.
696
697For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
698could start your program like this:
699
700 PERL_ANYEVENT_MODEL=Perl perl ...
701
702=back
703
525=head1 EXAMPLE 704=head1 EXAMPLE PROGRAM
526 705
527The following program uses an io watcher to read data from stdin, a timer 706The following program uses an IO watcher to read data from STDIN, a timer
528to display a message once per second, and a condvar to exit the program 707to display a message once per second, and a condition variable to quit the
529when the user enters quit: 708program when the user enters quit:
530 709
531 use AnyEvent; 710 use AnyEvent;
532 711
533 my $cv = AnyEvent->condvar; 712 my $cv = AnyEvent->condvar;
534 713
535 my $io_watcher = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub { 714 my $io_watcher = AnyEvent->io (
715 fh => \*STDIN,
716 poll => 'r',
717 cb => sub {
536 warn "io event <$_[0]>\n"; # will always output <r> 718 warn "io event <$_[0]>\n"; # will always output <r>
537 chomp (my $input = <STDIN>); # read a line 719 chomp (my $input = <STDIN>); # read a line
538 warn "read: $input\n"; # output what has been read 720 warn "read: $input\n"; # output what has been read
539 $cv->broadcast if $input =~ /^q/i; # quit program if /^q/i 721 $cv->broadcast if $input =~ /^q/i; # quit program if /^q/i
722 },
540 }); 723 );
541 724
542 my $time_watcher; # can only be used once 725 my $time_watcher; # can only be used once
543 726
544 sub new_timer { 727 sub new_timer {
545 $timer = AnyEvent->timer (after => 1, cb => sub { 728 $timer = AnyEvent->timer (after => 1, cb => sub {
… …
627 $txn->{finished}->wait; 810 $txn->{finished}->wait;
628 return $txn->{result}; 811 return $txn->{result};
629 812
630The actual code goes further and collects all errors (C<die>s, exceptions) 813The actual code goes further and collects all errors (C<die>s, exceptions)
631that occured during request processing. The C<result> method detects 814that occured during request processing. The C<result> method detects
632wether an exception as thrown (it is stored inside the $txn object) 815whether an exception as thrown (it is stored inside the $txn object)
633and just throws the exception, which means connection errors and other 816and just throws the exception, which means connection errors and other
634problems get reported tot he code that tries to use the result, not in a 817problems get reported tot he code that tries to use the result, not in a
635random callback. 818random callback.
636 819
637All of this enables the following usage styles: 820All of this enables the following usage styles:
… …
672 $quit->broadcast; 855 $quit->broadcast;
673 }); 856 });
674 857
675 $quit->wait; 858 $quit->wait;
676 859
860=head1 FORK
861
862Most event libraries are not fork-safe. The ones who are usually are
863because they are so inefficient. Only L<EV> is fully fork-aware.
864
865If you have to fork, you must either do so I<before> creating your first
866watcher OR you must not use AnyEvent at all in the child.
867
868=head1 SECURITY CONSIDERATIONS
869
870AnyEvent can be forced to load any event model via
871$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to
872execute arbitrary code or directly gain access, it can easily be used to
873make the program hang or malfunction in subtle ways, as AnyEvent watchers
874will not be active when the program uses a different event model than
875specified in the variable.
876
877You can make AnyEvent completely ignore this variable by deleting it
878before the first watcher gets created, e.g. with a C<BEGIN> block:
879
880 BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
881
882 use AnyEvent;
883
677=head1 SEE ALSO 884=head1 SEE ALSO
678 885
679Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>, 886Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,
680L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>. 887L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,
888L<Event::Lib>, L<Qt>, L<POE>.
681 889
682Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>, 890Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,
891L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,
892L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,
683L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, 893L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>.
684L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>.
685 894
686Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>. 895Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.
687 896
688=head1 897=head1 AUTHOR
898
899 Marc Lehmann <schmorp@schmorp.de>
900 http://home.schmorp.de/
689 901
690=cut 902=cut
691 903
6921 9041
693 905

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