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1NAME 1NAME
2 AnyEvent - provide framework for multiple event loops 2 AnyEvent - provide framework for multiple event loops
3 3
4 Event, Coro, Glib, Tk - various supported event loops 4 EV, Event, Coro::EV, Coro::Event, Glib, Tk, Perl, Event::Lib, Qt -
5 various supported event loops
5 6
6SYNOPSIS 7SYNOPSIS
7 use AnyEvent; 8 use AnyEvent;
8 9
9 my $w = AnyEvent->io (fh => ..., poll => "[rw]+", cb => sub { 10 my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub {
10 my ($poll_got) = @_;
11 ... 11 ...
12 }); 12 });
13
14 - only one io watcher per $fh and $poll type is allowed (i.e. on a
15 socket you can have one r + one w or one rw watcher, not any more.
16
17 - AnyEvent will keep filehandles alive, so as long as the watcher
18 exists, the filehandle exists.
19 13
20 my $w = AnyEvent->timer (after => $seconds, cb => sub { 14 my $w = AnyEvent->timer (after => $seconds, cb => sub {
21 ... 15 ...
22 }); 16 });
23 17
24 - io and time watchers get canceled whenever $w is destroyed, so keep a 18 my $w = AnyEvent->condvar; # stores whether a condition was flagged
25 copy
26
27 - timers can only be used once and must be recreated for repeated
28 operation
29
30 my $w = AnyEvent->condvar; # kind of main loop replacement
31 $w->wait; # enters main loop till $condvar gets ->broadcast 19 $w->wait; # enters "main loop" till $condvar gets ->broadcast
32 $w->broadcast; # wake up current and all future wait's 20 $w->broadcast; # wake up current and all future wait's
33 21
34 - condvars are used to give blocking behaviour when neccessary. Create a 22WHY YOU SHOULD USE THIS MODULE (OR NOT)
35 condvar for any "request" or "event" your module might create, 23 Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
36 "->broadcast" it when the event happens and provide a function that 24 nowadays. So what is different about AnyEvent?
37 calls "->wait" for it. See the examples below. 25
26 Executive Summary: AnyEvent is *compatible*, AnyEvent is *free of
27 policy* and AnyEvent is *small and efficient*.
28
29 First and foremost, *AnyEvent is not an event model* itself, it only
30 interfaces to whatever event model the main program happens to use in a
31 pragmatic way. For event models and certain classes of immortals alike,
32 the statement "there can only be one" is a bitter reality: In general,
33 only one event loop can be active at the same time in a process.
34 AnyEvent helps hiding the differences between those event loops.
35
36 The goal of AnyEvent is to offer module authors the ability to do event
37 programming (waiting for I/O or timer events) without subscribing to a
38 religion, a way of living, and most importantly: without forcing your
39 module users into the same thing by forcing them to use the same event
40 model you use.
41
42 For modules like POE or IO::Async (which is a total misnomer as it is
43 actually doing all I/O *synchronously*...), using them in your module is
44 like joining a cult: After you joined, you are dependent on them and you
45 cannot use anything else, as it is simply incompatible to everything
46 that isn't itself. What's worse, all the potential users of your module
47 are *also* forced to use the same event loop you use.
48
49 AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
50 fine. AnyEvent + Tk works fine etc. etc. but none of these work together
51 with the rest: POE + IO::Async? no go. Tk + Event? no go. Again: if your
52 module uses one of those, every user of your module has to use it, too.
53 But if your module uses AnyEvent, it works transparently with all event
54 models it supports (including stuff like POE and IO::Async, as long as
55 those use one of the supported event loops. It is trivial to add new
56 event loops to AnyEvent, too, so it is future-proof).
57
58 In addition to being free of having to use *the one and only true event
59 model*, AnyEvent also is free of bloat and policy: with POE or similar
60 modules, you get an enourmous amount of code and strict rules you have
61 to follow. AnyEvent, on the other hand, is lean and up to the point, by
62 only offering the functionality that is necessary, in as thin as a
63 wrapper as technically possible.
64
65 Of course, if you want lots of policy (this can arguably be somewhat
66 useful) and you want to force your users to use the one and only event
67 model, you should *not* use this module.
38 68
39DESCRIPTION 69DESCRIPTION
40 AnyEvent provides an identical interface to multiple event loops. This 70 AnyEvent provides an identical interface to multiple event loops. This
41 allows module authors to utilizy an event loop without forcing module 71 allows module authors to utilise an event loop without forcing module
42 users to use the same event loop (as only a single event loop can 72 users to use the same event loop (as only a single event loop can
43 coexist peacefully at any one time). 73 coexist peacefully at any one time).
44 74
45 The interface itself is vaguely similar but not identical to the Event 75 The interface itself is vaguely similar, but not identical to the Event
46 module. 76 module.
47 77
48 On the first call of any method, the module tries to detect the 78 During the first call of any watcher-creation method, the module tries
49 currently loaded event loop by probing wether any of the following 79 to detect the currently loaded event loop by probing whether one of the
50 modules is loaded: Coro::Event, Event, Glib, Tk. The first one found is 80 following modules is already loaded: Coro::EV, Coro::Event, EV, Event,
51 used. If none is found, the module tries to load these modules in the 81 Glib, Tk, Event::Lib, Qt. The first one found is used. If none are
82 found, the module tries to load these modules (excluding Event::Lib and
52 order given. The first one that could be successfully loaded will be 83 Qt) in the order given. The first one that can be successfully loaded
53 used. If still none could be found, it will issue an error. 84 will be used. If, after this, still none could be found, AnyEvent will
85 fall back to a pure-perl event loop, which is not very efficient, but
86 should work everywhere.
54 87
55EXAMPLE 88 Because AnyEvent first checks for modules that are already loaded,
56 The following program uses an io watcher to read data from stdin, a 89 loading an event model explicitly before first using AnyEvent will
57 timer to display a message once per second, and a condvar to exit the 90 likely make that model the default. For example:
58 program when the user enters quit:
59 91
92 use Tk;
60 use AnyEvent; 93 use AnyEvent;
61 94
95 # .. AnyEvent will likely default to Tk
96
97 The *likely* means that, if any module loads another event model and
98 starts using it, all bets are off. Maybe you should tell their authors
99 to use AnyEvent so their modules work together with others seamlessly...
100
101 The pure-perl implementation of AnyEvent is called
102 "AnyEvent::Impl::Perl". Like other event modules you can load it
103 explicitly.
104
105WATCHERS
106 AnyEvent has the central concept of a *watcher*, which is an object that
107 stores relevant data for each kind of event you are waiting for, such as
108 the callback to call, the filehandle to watch, etc.
109
110 These watchers are normal Perl objects with normal Perl lifetime. After
111 creating a watcher it will immediately "watch" for events and invoke the
112 callback when the event occurs (of course, only when the event model is
113 in control).
114
115 To disable the watcher you have to destroy it (e.g. by setting the
116 variable you store it in to "undef" or otherwise deleting all references
117 to it).
118
119 All watchers are created by calling a method on the "AnyEvent" class.
120
121 Many watchers either are used with "recursion" (repeating timers for
122 example), or need to refer to their watcher object in other ways.
123
124 An any way to achieve that is this pattern:
125
126 my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
127 # you can use $w here, for example to undef it
128 undef $w;
129 });
130
131 Note that "my $w; $w =" combination. This is necessary because in Perl,
132 my variables are only visible after the statement in which they are
133 declared.
134
135 IO WATCHERS
136 You can create an I/O watcher by calling the "AnyEvent->io" method with
137 the following mandatory key-value pairs as arguments:
138
139 "fh" the Perl *file handle* (*not* file descriptor) to watch for events.
140 "poll" must be a string that is either "r" or "w", which creates a
141 watcher waiting for "r"eadable or "w"ritable events, respectively. "cb"
142 is the callback to invoke each time the file handle becomes ready.
143
144 As long as the I/O watcher exists it will keep the file descriptor or a
145 copy of it alive/open.
146
147 It is not allowed to close a file handle as long as any watcher is
148 active on the underlying file descriptor.
149
150 Some event loops issue spurious readyness notifications, so you should
151 always use non-blocking calls when reading/writing from/to your file
152 handles.
153
154 Example:
155
156 # wait for readability of STDIN, then read a line and disable the watcher
157 my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
158 chomp (my $input = <STDIN>);
159 warn "read: $input\n";
160 undef $w;
161 });
162
163 TIME WATCHERS
164 You can create a time watcher by calling the "AnyEvent->timer" method
165 with the following mandatory arguments:
166
167 "after" specifies after how many seconds (fractional values are
168 supported) should the timer activate. "cb" the callback to invoke in
169 that case.
170
171 The timer callback will be invoked at most once: if you want a repeating
172 timer you have to create a new watcher (this is a limitation by both Tk
173 and Glib).
174
175 Example:
176
177 # fire an event after 7.7 seconds
178 my $w = AnyEvent->timer (after => 7.7, cb => sub {
179 warn "timeout\n";
180 });
181
182 # to cancel the timer:
183 undef $w;
184
185 Example 2:
186
187 # fire an event after 0.5 seconds, then roughly every second
188 my $w;
189
190 my $cb = sub {
191 # cancel the old timer while creating a new one
192 $w = AnyEvent->timer (after => 1, cb => $cb);
193 };
194
195 # start the "loop" by creating the first watcher
196 $w = AnyEvent->timer (after => 0.5, cb => $cb);
197
198 TIMING ISSUES
199 There are two ways to handle timers: based on real time (relative, "fire
200 in 10 seconds") and based on wallclock time (absolute, "fire at 12
201 o'clock").
202
203 While most event loops expect timers to specified in a relative way,
204 they use absolute time internally. This makes a difference when your
205 clock "jumps", for example, when ntp decides to set your clock backwards
206 from the wrong date of 2014-01-01 to 2008-01-01, a watcher that is
207 supposed to fire "after" a second might actually take six years to
208 finally fire.
209
210 AnyEvent cannot compensate for this. The only event loop that is
211 conscious about these issues is EV, which offers both relative
212 (ev_timer, based on true relative time) and absolute (ev_periodic, based
213 on wallclock time) timers.
214
215 AnyEvent always prefers relative timers, if available, matching the
216 AnyEvent API.
217
218 SIGNAL WATCHERS
219 You can watch for signals using a signal watcher, "signal" is the signal
220 *name* without any "SIG" prefix, "cb" is the Perl callback to be invoked
221 whenever a signal occurs.
222
223 Multiple signal occurances can be clumped together into one callback
224 invocation, and callback invocation will be synchronous. synchronous
225 means that it might take a while until the signal gets handled by the
226 process, but it is guarenteed not to interrupt any other callbacks.
227
228 The main advantage of using these watchers is that you can share a
229 signal between multiple watchers.
230
231 This watcher might use %SIG, so programs overwriting those signals
232 directly will likely not work correctly.
233
234 Example: exit on SIGINT
235
236 my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
237
238 CHILD PROCESS WATCHERS
239 You can also watch on a child process exit and catch its exit status.
240
241 The child process is specified by the "pid" argument (if set to 0, it
242 watches for any child process exit). The watcher will trigger as often
243 as status change for the child are received. This works by installing a
244 signal handler for "SIGCHLD". The callback will be called with the pid
245 and exit status (as returned by waitpid).
246
247 Example: wait for pid 1333
248
249 my $w = AnyEvent->child (
250 pid => 1333,
251 cb => sub {
252 my ($pid, $status) = @_;
253 warn "pid $pid exited with status $status";
254 },
255 );
256
257 CONDITION VARIABLES
258 Condition variables can be created by calling the "AnyEvent->condvar"
259 method without any arguments.
260
261 A condition variable waits for a condition - precisely that the
262 "->broadcast" method has been called.
263
264 They are very useful to signal that a condition has been fulfilled, for
265 example, if you write a module that does asynchronous http requests,
266 then a condition variable would be the ideal candidate to signal the
267 availability of results.
268
269 You can also use condition variables to block your main program until an
270 event occurs - for example, you could "->wait" in your main program
271 until the user clicks the Quit button in your app, which would
272 "->broadcast" the "quit" event.
273
274 Note that condition variables recurse into the event loop - if you have
275 two pirces of code that call "->wait" in a round-robbin fashion, you
276 lose. Therefore, condition variables are good to export to your caller,
277 but you should avoid making a blocking wait yourself, at least in
278 callbacks, as this asks for trouble.
279
280 This object has two methods:
281
282 $cv->wait
283 Wait (blocking if necessary) until the "->broadcast" method has been
284 called on c<$cv>, while servicing other watchers normally.
285
286 You can only wait once on a condition - additional calls will return
287 immediately.
288
289 Not all event models support a blocking wait - some die in that case
290 (programs might want to do that to stay interactive), so *if you are
291 using this from a module, never require a blocking wait*, but let
292 the caller decide whether the call will block or not (for example,
293 by coupling condition variables with some kind of request results
294 and supporting callbacks so the caller knows that getting the result
295 will not block, while still suppporting blocking waits if the caller
296 so desires).
297
298 Another reason *never* to "->wait" in a module is that you cannot
299 sensibly have two "->wait"'s in parallel, as that would require
300 multiple interpreters or coroutines/threads, none of which
301 "AnyEvent" can supply (the coroutine-aware backends
302 AnyEvent::Impl::CoroEV and AnyEvent::Impl::CoroEvent explicitly
303 support concurrent "->wait"'s from different coroutines, however).
304
305 $cv->broadcast
306 Flag the condition as ready - a running "->wait" and all further
307 calls to "wait" will (eventually) return after this method has been
308 called. If nobody is waiting the broadcast will be remembered..
309
310 Example:
311
312 # wait till the result is ready
313 my $result_ready = AnyEvent->condvar;
314
315 # do something such as adding a timer
316 # or socket watcher the calls $result_ready->broadcast
317 # when the "result" is ready.
318 # in this case, we simply use a timer:
319 my $w = AnyEvent->timer (
320 after => 1,
321 cb => sub { $result_ready->broadcast },
322 );
323
324 # this "blocks" (while handling events) till the watcher
325 # calls broadcast
326 $result_ready->wait;
327
328GLOBAL VARIABLES AND FUNCTIONS
329 $AnyEvent::MODEL
330 Contains "undef" until the first watcher is being created. Then it
331 contains the event model that is being used, which is the name of
332 the Perl class implementing the model. This class is usually one of
333 the "AnyEvent::Impl:xxx" modules, but can be any other class in the
334 case AnyEvent has been extended at runtime (e.g. in *rxvt-unicode*).
335
336 The known classes so far are:
337
338 AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
339 AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
340 AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
341 AnyEvent::Impl::Event based on Event, second best choice.
342 AnyEvent::Impl::Glib based on Glib, third-best choice.
343 AnyEvent::Impl::Tk based on Tk, very bad choice.
344 AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
345 AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
346 AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
347
348 AnyEvent::detect
349 Returns $AnyEvent::MODEL, forcing autodetection of the event model
350 if necessary. You should only call this function right before you
351 would have created an AnyEvent watcher anyway, that is, as late as
352 possible at runtime.
353
354WHAT TO DO IN A MODULE
355 As a module author, you should "use AnyEvent" and call AnyEvent methods
356 freely, but you should not load a specific event module or rely on it.
357
358 Be careful when you create watchers in the module body - AnyEvent will
359 decide which event module to use as soon as the first method is called,
360 so by calling AnyEvent in your module body you force the user of your
361 module to load the event module first.
362
363 Never call "->wait" on a condition variable unless you *know* that the
364 "->broadcast" method has been called on it already. This is because it
365 will stall the whole program, and the whole point of using events is to
366 stay interactive.
367
368 It is fine, however, to call "->wait" when the user of your module
369 requests it (i.e. if you create a http request object ad have a method
370 called "results" that returns the results, it should call "->wait"
371 freely, as the user of your module knows what she is doing. always).
372
373WHAT TO DO IN THE MAIN PROGRAM
374 There will always be a single main program - the only place that should
375 dictate which event model to use.
376
377 If it doesn't care, it can just "use AnyEvent" and use it itself, or not
378 do anything special (it does not need to be event-based) and let
379 AnyEvent decide which implementation to chose if some module relies on
380 it.
381
382 If the main program relies on a specific event model. For example, in
383 Gtk2 programs you have to rely on the Glib module. You should load the
384 event module before loading AnyEvent or any module that uses it:
385 generally speaking, you should load it as early as possible. The reason
386 is that modules might create watchers when they are loaded, and AnyEvent
387 will decide on the event model to use as soon as it creates watchers,
388 and it might chose the wrong one unless you load the correct one
389 yourself.
390
391 You can chose to use a rather inefficient pure-perl implementation by
392 loading the "AnyEvent::Impl::Perl" module, which gives you similar
393 behaviour everywhere, but letting AnyEvent chose is generally better.
394
395SUPPLYING YOUR OWN EVENT MODEL INTERFACE
396 This is an advanced topic that you do not normally need to use AnyEvent
397 in a module. This section is only of use to event loop authors who want
398 to provide AnyEvent compatibility.
399
400 If you need to support another event library which isn't directly
401 supported by AnyEvent, you can supply your own interface to it by
402 pushing, before the first watcher gets created, the package name of the
403 event module and the package name of the interface to use onto
404 @AnyEvent::REGISTRY. You can do that before and even without loading
405 AnyEvent, so it is reasonably cheap.
406
407 Example:
408
409 push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];
410
411 This tells AnyEvent to (literally) use the "urxvt::anyevent::"
412 package/class when it finds the "urxvt" package/module is already
413 loaded.
414
415 When AnyEvent is loaded and asked to find a suitable event model, it
416 will first check for the presence of urxvt by trying to "use" the
417 "urxvt::anyevent" module.
418
419 The class should provide implementations for all watcher types. See
420 AnyEvent::Impl::EV (source code), AnyEvent::Impl::Glib (Source code) and
421 so on for actual examples. Use "perldoc -m AnyEvent::Impl::Glib" to see
422 the sources.
423
424 If you don't provide "signal" and "child" watchers than AnyEvent will
425 provide suitable (hopefully) replacements.
426
427 The above example isn't fictitious, the *rxvt-unicode* (a.k.a. urxvt)
428 terminal emulator uses the above line as-is. An interface isn't included
429 in AnyEvent because it doesn't make sense outside the embedded
430 interpreter inside *rxvt-unicode*, and it is updated and maintained as
431 part of the *rxvt-unicode* distribution.
432
433 *rxvt-unicode* also cheats a bit by not providing blocking access to
434 condition variables: code blocking while waiting for a condition will
435 "die". This still works with most modules/usages, and blocking calls
436 must not be done in an interactive application, so it makes sense.
437
438ENVIRONMENT VARIABLES
439 The following environment variables are used by this module:
440
441 "PERL_ANYEVENT_VERBOSE"
442 When set to 2 or higher, cause AnyEvent to report to STDERR which
443 event model it chooses.
444
445 "PERL_ANYEVENT_MODEL"
446 This can be used to specify the event model to be used by AnyEvent,
447 before autodetection and -probing kicks in. It must be a string
448 consisting entirely of ASCII letters. The string "AnyEvent::Impl::"
449 gets prepended and the resulting module name is loaded and if the
450 load was successful, used as event model. If it fails to load
451 AnyEvent will proceed with autodetection and -probing.
452
453 This functionality might change in future versions.
454
455 For example, to force the pure perl model (AnyEvent::Impl::Perl) you
456 could start your program like this:
457
458 PERL_ANYEVENT_MODEL=Perl perl ...
459
460EXAMPLE PROGRAM
461 The following program uses an IO watcher to read data from STDIN, a
462 timer to display a message once per second, and a condition variable to
463 quit the program when the user enters quit:
464
465 use AnyEvent;
466
62 my $cv = AnyEvent->condvar; 467 my $cv = AnyEvent->condvar;
63 468
64 my $io_watcher = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub { 469 my $io_watcher = AnyEvent->io (
470 fh => \*STDIN,
471 poll => 'r',
472 cb => sub {
65 warn "io event <$_[0]>\n"; # will always output <r> 473 warn "io event <$_[0]>\n"; # will always output <r>
66 chomp (my $input = <STDIN>); # read a line 474 chomp (my $input = <STDIN>); # read a line
67 warn "read: $input\n"; # output what has been read 475 warn "read: $input\n"; # output what has been read
68 $cv->broadcast if $input =~ /^q/i; # quit program if /^q/i 476 $cv->broadcast if $input =~ /^q/i; # quit program if /^q/i
477 },
69 }); 478 );
70 479
71 my $time_watcher; # can only be used once 480 my $time_watcher; # can only be used once
72 481
73 sub new_timer { 482 sub new_timer {
74 $timer = AnyEvent->timer (after => 1, cb => sub { 483 $timer = AnyEvent->timer (after => 1, cb => sub {
… …
116 connect $txn->{fh}, ... 525 connect $txn->{fh}, ...
117 and !$!{EWOULDBLOCK} 526 and !$!{EWOULDBLOCK}
118 and !$!{EINPROGRESS} 527 and !$!{EINPROGRESS}
119 and Carp::croak "unable to connect: $!\n"; 528 and Carp::croak "unable to connect: $!\n";
120 529
121 Then it creates a write-watcher which gets called wehnever an error 530 Then it creates a write-watcher which gets called whenever an error
122 occurs or the connection succeeds: 531 occurs or the connection succeeds:
123 532
124 $txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'w', cb => sub { $txn->fh_ready_w }); 533 $txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'w', cb => sub { $txn->fh_ready_w });
125 534
126 And returns this transaction object. The "fh_ready_w" callback gets 535 And returns this transaction object. The "fh_ready_w" callback gets
… …
143 sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf}; 552 sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
144 553
145 if (end-of-file or data complete) { 554 if (end-of-file or data complete) {
146 $txn->{result} = $txn->{buf}; 555 $txn->{result} = $txn->{buf};
147 $txn->{finished}->broadcast; 556 $txn->{finished}->broadcast;
557 $txb->{cb}->($txn) of $txn->{cb}; # also call callback
148 } 558 }
149 559
150 The "result" method, finally, just waits for the finished signal (if the 560 The "result" method, finally, just waits for the finished signal (if the
151 request was already finished, it doesn't wait, of course, and returns 561 request was already finished, it doesn't wait, of course, and returns
152 the data: 562 the data:
153 563
154 $txn->{finished}->wait; 564 $txn->{finished}->wait;
155 return $txn->{buf}; 565 return $txn->{result};
156 566
157 The actual code goes further and collects all errors ("die"s, 567 The actual code goes further and collects all errors ("die"s,
158 exceptions) that occured during request processing. The "result" method 568 exceptions) that occured during request processing. The "result" method
159 detects wether an exception as thrown (it is stored inside the $txn 569 detects whether an exception as thrown (it is stored inside the $txn
160 object) and just throws the exception, which means connection errors and 570 object) and just throws the exception, which means connection errors and
161 other problems get reported tot he code that tries to use the result, 571 other problems get reported tot he code that tries to use the result,
162 not in a random callback. 572 not in a random callback.
163 573
164 All of this enables the following usage styles: 574 All of this enables the following usage styles:
165 575
166 1. Blocking: 576 1. Blocking:
167 577
168 my $data = $fcp->client_get ($url); 578 my $data = $fcp->client_get ($url);
169 579
170 2. Blocking, but parallelizing: 580 2. Blocking, but running in parallel:
171 581
172 my @datas = map $_->result, 582 my @datas = map $_->result,
173 map $fcp->txn_client_get ($_), 583 map $fcp->txn_client_get ($_),
174 @urls; 584 @urls;
175 585
176 Both blocking examples work without the module user having to know 586 Both blocking examples work without the module user having to know
177 anything about events. 587 anything about events.
178 588
179 3a. Event-based in a main program, using any support Event module: 589 3a. Event-based in a main program, using any supported event module:
180 590
181 use Event; 591 use EV;
182 592
183 $fcp->txn_client_get ($url)->cb (sub { 593 $fcp->txn_client_get ($url)->cb (sub {
184 my $txn = shift; 594 my $txn = shift;
185 my $data = $txn->result; 595 my $data = $txn->result;
186 ... 596 ...
187 }); 597 });
188 598
189 Event::loop; 599 EV::loop;
190 600
191 3b. The module user could use AnyEvent, too: 601 3b. The module user could use AnyEvent, too:
192 602
193 use AnyEvent; 603 use AnyEvent;
194 604
… …
199 $quit->broadcast; 609 $quit->broadcast;
200 }); 610 });
201 611
202 $quit->wait; 612 $quit->wait;
203 613
614FORK
615 Most event libraries are not fork-safe. The ones who are usually are
616 because they are so inefficient. Only EV is fully fork-aware.
617
618 If you have to fork, you must either do so *before* creating your first
619 watcher OR you must not use AnyEvent at all in the child.
620
621SECURITY CONSIDERATIONS
622 AnyEvent can be forced to load any event model via
623 $ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used
624 to execute arbitrary code or directly gain access, it can easily be used
625 to make the program hang or malfunction in subtle ways, as AnyEvent
626 watchers will not be active when the program uses a different event
627 model than specified in the variable.
628
629 You can make AnyEvent completely ignore this variable by deleting it
630 before the first watcher gets created, e.g. with a "BEGIN" block:
631
632 BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
633
634 use AnyEvent;
635
204SEE ALSO 636SEE ALSO
205 Event modules: Coro::Event, Coro, Event, Glib::Event, Glib. 637 Event modules: Coro::EV, EV, EV::Glib, Glib::EV, Coro::Event, Event,
638 Glib::Event, Glib, Coro, Tk, Event::Lib, Qt.
206 639
207 Implementations: AnyEvent::Impl::Coro, AnyEvent::Impl::Event, 640 Implementations: AnyEvent::Impl::CoroEV, AnyEvent::Impl::EV,
208 AnyEvent::Impl::Glib, AnyEvent::Impl::Tk. 641 AnyEvent::Impl::CoroEvent, AnyEvent::Impl::Event, AnyEvent::Impl::Glib,
642 AnyEvent::Impl::Tk, AnyEvent::Impl::Perl, AnyEvent::Impl::EventLib,
643 AnyEvent::Impl::Qt.
209 644
210 Nontrivial usage example: Net::FCP. 645 Nontrivial usage examples: Net::FCP, Net::XMPP2.
211 646
647AUTHOR
648 Marc Lehmann <schmorp@schmorp.de>
649 http://home.schmorp.de/
212 650

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