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5 Qt and POE are various supported event loops/environments. 5 Qt and POE are various supported event loops/environments.
6 6
7SYNOPSIS 7SYNOPSIS
8 use AnyEvent; 8 use AnyEvent;
9 9
10 # if you prefer function calls, look at the L<AE> manpage for 10 # if you prefer function calls, look at the AE manpage for
11 # an alternative API. 11 # an alternative API.
12 12
13 # file handle or descriptor readable 13 # file handle or descriptor readable
14 my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... }); 14 my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... });
15 15
16 # one-shot or repeating timers 16 # one-shot or repeating timers
17 my $w = AnyEvent->timer (after => $seconds, cb => sub { ... }); 17 my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
18 my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ... 18 my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...);
19 19
20 print AnyEvent->now; # prints current event loop time 20 print AnyEvent->now; # prints current event loop time
21 print AnyEvent->time; # think Time::HiRes::time or simply CORE::time. 21 print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
22 22
23 # POSIX signal 23 # POSIX signal
42 This manpage is mainly a reference manual. If you are interested in a 42 This manpage is mainly a reference manual. If you are interested in a
43 tutorial or some gentle introduction, have a look at the AnyEvent::Intro 43 tutorial or some gentle introduction, have a look at the AnyEvent::Intro
44 manpage. 44 manpage.
45 45
46SUPPORT 46SUPPORT
47 An FAQ document is available as AnyEvent::FAQ.
48
47 There is a mailinglist for discussing all things AnyEvent, and an IRC 49 There also is a mailinglist for discussing all things AnyEvent, and an
48 channel, too. 50 IRC channel, too.
49 51
50 See the AnyEvent project page at the Schmorpforge Ta-Sa Software 52 See the AnyEvent project page at the Schmorpforge Ta-Sa Software
51 Repository, at <http://anyevent.schmorp.de>, for more info. 53 Repository, at <http://anyevent.schmorp.de>, for more info.
52 54
53WHY YOU SHOULD USE THIS MODULE (OR NOT) 55WHY YOU SHOULD USE THIS MODULE (OR NOT)
71 module users into the same thing by forcing them to use the same event 73 module users into the same thing by forcing them to use the same event
72 model you use. 74 model you use.
73 75
74 For modules like POE or IO::Async (which is a total misnomer as it is 76 For modules like POE or IO::Async (which is a total misnomer as it is
75 actually doing all I/O *synchronously*...), using them in your module is 77 actually doing all I/O *synchronously*...), using them in your module is
76 like joining a cult: After you joined, you are dependent on them and you 78 like joining a cult: After you join, you are dependent on them and you
77 cannot use anything else, as they are simply incompatible to everything 79 cannot use anything else, as they are simply incompatible to everything
78 that isn't them. What's worse, all the potential users of your module 80 that isn't them. What's worse, all the potential users of your module
79 are *also* forced to use the same event loop you use. 81 are *also* forced to use the same event loop you use.
80 82
81 AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works 83 AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
82 fine. AnyEvent + Tk works fine etc. etc. but none of these work together 84 fine. AnyEvent + Tk works fine etc. etc. but none of these work together
83 with the rest: POE + IO::Async? No go. Tk + Event? No go. Again: if your 85 with the rest: POE + EV? No go. Tk + Event? No go. Again: if your module
84 module uses one of those, every user of your module has to use it, too. 86 uses one of those, every user of your module has to use it, too. But if
85 But if your module uses AnyEvent, it works transparently with all event 87 your module uses AnyEvent, it works transparently with all event models
86 models it supports (including stuff like IO::Async, as long as those use 88 it supports (including stuff like IO::Async, as long as those use one of
87 one of the supported event loops. It is trivial to add new event loops 89 the supported event loops. It is easy to add new event loops to
88 to AnyEvent, too, so it is future-proof). 90 AnyEvent, too, so it is future-proof).
89 91
90 In addition to being free of having to use *the one and only true event 92 In addition to being free of having to use *the one and only true event
91 model*, AnyEvent also is free of bloat and policy: with POE or similar 93 model*, AnyEvent also is free of bloat and policy: with POE or similar
92 modules, you get an enormous amount of code and strict rules you have to 94 modules, you get an enormous amount of code and strict rules you have to
93 follow. AnyEvent, on the other hand, is lean and up to the point, by 95 follow. AnyEvent, on the other hand, is lean and to the point, by only
94 only offering the functionality that is necessary, in as thin as a 96 offering the functionality that is necessary, in as thin as a wrapper as
95 wrapper as technically possible. 97 technically possible.
96 98
97 Of course, AnyEvent comes with a big (and fully optional!) toolbox of 99 Of course, AnyEvent comes with a big (and fully optional!) toolbox of
98 useful functionality, such as an asynchronous DNS resolver, 100% 100 useful functionality, such as an asynchronous DNS resolver, 100%
99 non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms 101 non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms
100 such as Windows) and lots of real-world knowledge and workarounds for 102 such as Windows) and lots of real-world knowledge and workarounds for
103 Now, if you *do want* lots of policy (this can arguably be somewhat 105 Now, if you *do want* lots of policy (this can arguably be somewhat
104 useful) and you want to force your users to use the one and only event 106 useful) and you want to force your users to use the one and only event
105 model, you should *not* use this module. 107 model, you should *not* use this module.
106 108
107DESCRIPTION 109DESCRIPTION
108 AnyEvent provides an identical interface to multiple event loops. This 110 AnyEvent provides a uniform interface to various event loops. This
109 allows module authors to utilise an event loop without forcing module 111 allows module authors to use event loop functionality without forcing
110 users to use the same event loop (as only a single event loop can 112 module users to use a specific event loop implementation (since more
111 coexist peacefully at any one time). 113 than one event loop cannot coexist peacefully).
112 114
113 The interface itself is vaguely similar, but not identical to the Event 115 The interface itself is vaguely similar, but not identical to the Event
114 module. 116 module.
115 117
116 During the first call of any watcher-creation method, the module tries 118 During the first call of any watcher-creation method, the module tries
117 to detect the currently loaded event loop by probing whether one of the 119 to detect the currently loaded event loop by probing whether one of the
118 following modules is already loaded: EV, Event, Glib, 120 following modules is already loaded: EV, AnyEvent::Impl::Perl, Event,
119 AnyEvent::Impl::Perl, Tk, Event::Lib, Qt, POE. The first one found is 121 Glib, Tk, Event::Lib, Qt, POE. The first one found is used. If none are
120 used. If none are found, the module tries to load these modules 122 detected, the module tries to load the first four modules in the order
121 (excluding Tk, Event::Lib, Qt and POE as the pure perl adaptor should 123 given; but note that if EV is not available, the pure-perl
122 always succeed) in the order given. The first one that can be 124 AnyEvent::Impl::Perl should always work, so the other two are not
123 successfully loaded will be used. If, after this, still none could be 125 normally tried.
124 found, AnyEvent will fall back to a pure-perl event loop, which is not
125 very efficient, but should work everywhere.
126 126
127 Because AnyEvent first checks for modules that are already loaded, 127 Because AnyEvent first checks for modules that are already loaded,
128 loading an event model explicitly before first using AnyEvent will 128 loading an event model explicitly before first using AnyEvent will
129 likely make that model the default. For example: 129 likely make that model the default. For example:
130 130
132 use AnyEvent; 132 use AnyEvent;
133 133
134 # .. AnyEvent will likely default to Tk 134 # .. AnyEvent will likely default to Tk
135 135
136 The *likely* means that, if any module loads another event model and 136 The *likely* means that, if any module loads another event model and
137 starts using it, all bets are off. Maybe you should tell their authors 137 starts using it, all bets are off - this case should be very rare
138 to use AnyEvent so their modules work together with others seamlessly... 138 though, as very few modules hardcode event loops without announcing this
139 very loudly.
139 140
140 The pure-perl implementation of AnyEvent is called 141 The pure-perl implementation of AnyEvent is called
141 "AnyEvent::Impl::Perl". Like other event modules you can load it 142 "AnyEvent::Impl::Perl". Like other event modules you can load it
142 explicitly and enjoy the high availability of that event loop :) 143 explicitly and enjoy the high availability of that event loop :)
143 144
151 callback when the event occurs (of course, only when the event model is 152 callback when the event occurs (of course, only when the event model is
152 in control). 153 in control).
153 154
154 Note that callbacks must not permanently change global variables 155 Note that callbacks must not permanently change global variables
155 potentially in use by the event loop (such as $_ or $[) and that 156 potentially in use by the event loop (such as $_ or $[) and that
156 callbacks must not "die". The former is good programming practise in 157 callbacks must not "die". The former is good programming practice in
157 Perl and the latter stems from the fact that exception handling differs 158 Perl and the latter stems from the fact that exception handling differs
158 widely between event loops. 159 widely between event loops.
159 160
160 To disable the watcher you have to destroy it (e.g. by setting the 161 To disable a watcher you have to destroy it (e.g. by setting the
161 variable you store it in to "undef" or otherwise deleting all references 162 variable you store it in to "undef" or otherwise deleting all references
162 to it). 163 to it).
163 164
164 All watchers are created by calling a method on the "AnyEvent" class. 165 All watchers are created by calling a method on the "AnyEvent" class.
165 166
166 Many watchers either are used with "recursion" (repeating timers for 167 Many watchers either are used with "recursion" (repeating timers for
167 example), or need to refer to their watcher object in other ways. 168 example), or need to refer to their watcher object in other ways.
168 169
169 An any way to achieve that is this pattern: 170 One way to achieve that is this pattern:
170 171
171 my $w; $w = AnyEvent->type (arg => value ..., cb => sub { 172 my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
172 # you can use $w here, for example to undef it 173 # you can use $w here, for example to undef it
173 undef $w; 174 undef $w;
174 }); 175 });
205 206
206 The I/O watcher might use the underlying file descriptor or a copy of 207 The I/O watcher might use the underlying file descriptor or a copy of
207 it. You must not close a file handle as long as any watcher is active on 208 it. You must not close a file handle as long as any watcher is active on
208 the underlying file descriptor. 209 the underlying file descriptor.
209 210
210 Some event loops issue spurious readyness notifications, so you should 211 Some event loops issue spurious readiness notifications, so you should
211 always use non-blocking calls when reading/writing from/to your file 212 always use non-blocking calls when reading/writing from/to your file
212 handles. 213 handles.
213 214
214 Example: wait for readability of STDIN, then read a line and disable the 215 Example: wait for readability of STDIN, then read a line and disable the
215 watcher. 216 watcher.
238 239
239 Although the callback might get passed parameters, their value and 240 Although the callback might get passed parameters, their value and
240 presence is undefined and you cannot rely on them. Portable AnyEvent 241 presence is undefined and you cannot rely on them. Portable AnyEvent
241 callbacks cannot use arguments passed to time watcher callbacks. 242 callbacks cannot use arguments passed to time watcher callbacks.
242 243
243 The callback will normally be invoked once only. If you specify another 244 The callback will normally be invoked only once. If you specify another
244 parameter, "interval", as a strictly positive number (> 0), then the 245 parameter, "interval", as a strictly positive number (> 0), then the
245 callback will be invoked regularly at that interval (in fractional 246 callback will be invoked regularly at that interval (in fractional
246 seconds) after the first invocation. If "interval" is specified with a 247 seconds) after the first invocation. If "interval" is specified with a
247 false value, then it is treated as if it were missing. 248 false value, then it is treated as if it were not specified at all.
248 249
249 The callback will be rescheduled before invoking the callback, but no 250 The callback will be rescheduled before invoking the callback, but no
250 attempt is done to avoid timer drift in most backends, so the interval 251 attempt is made to avoid timer drift in most backends, so the interval
251 is only approximate. 252 is only approximate.
252 253
253 Example: fire an event after 7.7 seconds. 254 Example: fire an event after 7.7 seconds.
254 255
255 my $w = AnyEvent->timer (after => 7.7, cb => sub { 256 my $w = AnyEvent->timer (after => 7.7, cb => sub {
272 273
273 While most event loops expect timers to specified in a relative way, 274 While most event loops expect timers to specified in a relative way,
274 they use absolute time internally. This makes a difference when your 275 they use absolute time internally. This makes a difference when your
275 clock "jumps", for example, when ntp decides to set your clock backwards 276 clock "jumps", for example, when ntp decides to set your clock backwards
276 from the wrong date of 2014-01-01 to 2008-01-01, a watcher that is 277 from the wrong date of 2014-01-01 to 2008-01-01, a watcher that is
277 supposed to fire "after" a second might actually take six years to 278 supposed to fire "after a second" might actually take six years to
278 finally fire. 279 finally fire.
279 280
280 AnyEvent cannot compensate for this. The only event loop that is 281 AnyEvent cannot compensate for this. The only event loop that is
281 conscious about these issues is EV, which offers both relative 282 conscious of these issues is EV, which offers both relative (ev_timer,
282 (ev_timer, based on true relative time) and absolute (ev_periodic, based 283 based on true relative time) and absolute (ev_periodic, based on
283 on wallclock time) timers. 284 wallclock time) timers.
284 285
285 AnyEvent always prefers relative timers, if available, matching the 286 AnyEvent always prefers relative timers, if available, matching the
286 AnyEvent API. 287 AnyEvent API.
287 288
288 AnyEvent has two additional methods that return the "current time": 289 AnyEvent has two additional methods that return the "current time":
307 *In almost all cases (in all cases if you don't care), this is the 308 *In almost all cases (in all cases if you don't care), this is the
308 function to call when you want to know the current time.* 309 function to call when you want to know the current time.*
309 310
310 This function is also often faster then "AnyEvent->time", and thus 311 This function is also often faster then "AnyEvent->time", and thus
311 the preferred method if you want some timestamp (for example, 312 the preferred method if you want some timestamp (for example,
312 AnyEvent::Handle uses this to update it's activity timeouts). 313 AnyEvent::Handle uses this to update its activity timeouts).
313 314
314 The rest of this section is only of relevance if you try to be very 315 The rest of this section is only of relevance if you try to be very
315 exact with your timing, you can skip it without bad conscience. 316 exact with your timing; you can skip it without a bad conscience.
316 317
317 For a practical example of when these times differ, consider 318 For a practical example of when these times differ, consider
318 Event::Lib and EV and the following set-up: 319 Event::Lib and EV and the following set-up:
319 320
320 The event loop is running and has just invoked one of your callback 321 The event loop is running and has just invoked one of your callbacks
321 at time=500 (assume no other callbacks delay processing). In your 322 at time=500 (assume no other callbacks delay processing). In your
322 callback, you wait a second by executing "sleep 1" (blocking the 323 callback, you wait a second by executing "sleep 1" (blocking the
323 process for a second) and then (at time=501) you create a relative 324 process for a second) and then (at time=501) you create a relative
324 timer that fires after three seconds. 325 timer that fires after three seconds.
325 326
414 415
415 Signal Races, Delays and Workarounds 416 Signal Races, Delays and Workarounds
416 Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching 417 Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
417 callbacks to signals in a generic way, which is a pity, as you cannot do 418 callbacks to signals in a generic way, which is a pity, as you cannot do
418 race-free signal handling in perl, requiring C libraries for this. 419 race-free signal handling in perl, requiring C libraries for this.
419 AnyEvent will try to do it's best, which means in some cases, signals 420 AnyEvent will try to do its best, which means in some cases, signals
420 will be delayed. The maximum time a signal might be delayed is specified 421 will be delayed. The maximum time a signal might be delayed is specified
421 in $AnyEvent::MAX_SIGNAL_LATENCY (default: 10 seconds). This variable 422 in $AnyEvent::MAX_SIGNAL_LATENCY (default: 10 seconds). This variable
422 can be changed only before the first signal watcher is created, and 423 can be changed only before the first signal watcher is created, and
423 should be left alone otherwise. This variable determines how often 424 should be left alone otherwise. This variable determines how often
424 AnyEvent polls for signals (in case a wake-up was missed). Higher values 425 AnyEvent polls for signals (in case a wake-up was missed). Higher values
426 saving. 427 saving.
427 428
428 All these problems can be avoided by installing the optional 429 All these problems can be avoided by installing the optional
429 Async::Interrupt module, which works with most event loops. It will not 430 Async::Interrupt module, which works with most event loops. It will not
430 work with inherently broken event loops such as Event or Event::Lib (and 431 work with inherently broken event loops such as Event or Event::Lib (and
431 not with POE currently, as POE does it's own workaround with one-second 432 not with POE currently, as POE does its own workaround with one-second
432 latency). For those, you just have to suffer the delays. 433 latency). For those, you just have to suffer the delays.
433 434
434 CHILD PROCESS WATCHERS 435 CHILD PROCESS WATCHERS
435 $w = AnyEvent->child (pid => <process id>, cb => <callback>); 436 $w = AnyEvent->child (pid => <process id>, cb => <callback>);
436 437
437 You can also watch on a child process exit and catch its exit status. 438 You can also watch for a child process exit and catch its exit status.
438 439
439 The child process is specified by the "pid" argument (one some backends, 440 The child process is specified by the "pid" argument (on some backends,
440 using 0 watches for any child process exit, on others this will croak). 441 using 0 watches for any child process exit, on others this will croak).
441 The watcher will be triggered only when the child process has finished 442 The watcher will be triggered only when the child process has finished
442 and an exit status is available, not on any trace events 443 and an exit status is available, not on any trace events
443 (stopped/continued). 444 (stopped/continued).
444 445
489 $done->recv; 490 $done->recv;
490 491
491 IDLE WATCHERS 492 IDLE WATCHERS
492 $w = AnyEvent->idle (cb => <callback>); 493 $w = AnyEvent->idle (cb => <callback>);
493 494
494 Repeatedly invoke the callback after the process becomes idle, until 495 This will repeatedly invoke the callback after the process becomes idle,
495 either the watcher is destroyed or new events have been detected. 496 until either the watcher is destroyed or new events have been detected.
496 497
497 Idle watchers are useful when there is a need to do something, but it is 498 Idle watchers are useful when there is a need to do something, but it is
498 not so important (or wise) to do it instantly. The callback will be 499 not so important (or wise) to do it instantly. The callback will be
499 invoked only when there is "nothing better to do", which is usually 500 invoked only when there is "nothing better to do", which is usually
500 defined as "all outstanding events have been handled and no new events 501 defined as "all outstanding events have been handled and no new events
539 540
540 AnyEvent is slightly different: it expects somebody else to run the 541 AnyEvent is slightly different: it expects somebody else to run the
541 event loop and will only block when necessary (usually when told by the 542 event loop and will only block when necessary (usually when told by the
542 user). 543 user).
543 544
544 The instrument to do that is called a "condition variable", so called 545 The tool to do that is called a "condition variable", so called because
545 because they represent a condition that must become true. 546 they represent a condition that must become true.
546 547
547 Now is probably a good time to look at the examples further below. 548 Now is probably a good time to look at the examples further below.
548 549
549 Condition variables can be created by calling the "AnyEvent->condvar" 550 Condition variables can be created by calling the "AnyEvent->condvar"
550 method, usually without arguments. The only argument pair allowed is 551 method, usually without arguments. The only argument pair allowed is
555 After creation, the condition variable is "false" until it becomes 556 After creation, the condition variable is "false" until it becomes
556 "true" by calling the "send" method (or calling the condition variable 557 "true" by calling the "send" method (or calling the condition variable
557 as if it were a callback, read about the caveats in the description for 558 as if it were a callback, read about the caveats in the description for
558 the "->send" method). 559 the "->send" method).
559 560
560 Condition variables are similar to callbacks, except that you can 561 Since condition variables are the most complex part of the AnyEvent API,
561 optionally wait for them. They can also be called merge points - points 562 here are some different mental models of what they are - pick the ones
562 in time where multiple outstanding events have been processed. And yet 563 you can connect to:
563 another way to call them is transactions - each condition variable can 564
564 be used to represent a transaction, which finishes at some point and 565 * Condition variables are like callbacks - you can call them (and pass
565 delivers a result. And yet some people know them as "futures" - a 566 them instead of callbacks). Unlike callbacks however, you can also
566 promise to compute/deliver something that you can wait for. 567 wait for them to be called.
568
569 * Condition variables are signals - one side can emit or send them,
570 the other side can wait for them, or install a handler that is
571 called when the signal fires.
572
573 * Condition variables are like "Merge Points" - points in your program
574 where you merge multiple independent results/control flows into one.
575
576 * Condition variables represent a transaction - functions that start
577 some kind of transaction can return them, leaving the caller the
578 choice between waiting in a blocking fashion, or setting a callback.
579
580 * Condition variables represent future values, or promises to deliver
581 some result, long before the result is available.
567 582
568 Condition variables are very useful to signal that something has 583 Condition variables are very useful to signal that something has
569 finished, for example, if you write a module that does asynchronous http 584 finished, for example, if you write a module that does asynchronous http
570 requests, then a condition variable would be the ideal candidate to 585 requests, then a condition variable would be the ideal candidate to
571 signal the availability of results. The user can either act when the 586 signal the availability of results. The user can either act when the
584 599
585 Condition variables are represented by hash refs in perl, and the keys 600 Condition variables are represented by hash refs in perl, and the keys
586 used by AnyEvent itself are all named "_ae_XXX" to make subclassing easy 601 used by AnyEvent itself are all named "_ae_XXX" to make subclassing easy
587 (it is often useful to build your own transaction class on top of 602 (it is often useful to build your own transaction class on top of
588 AnyEvent). To subclass, use "AnyEvent::CondVar" as base class and call 603 AnyEvent). To subclass, use "AnyEvent::CondVar" as base class and call
589 it's "new" method in your own "new" method. 604 its "new" method in your own "new" method.
590 605
591 There are two "sides" to a condition variable - the "producer side" 606 There are two "sides" to a condition variable - the "producer side"
592 which eventually calls "-> send", and the "consumer side", which waits 607 which eventually calls "-> send", and the "consumer side", which waits
593 for the send to occur. 608 for the send to occur.
594 609
654 Condition variables are overloaded so one can call them directly (as 669 Condition variables are overloaded so one can call them directly (as
655 if they were a code reference). Calling them directly is the same as 670 if they were a code reference). Calling them directly is the same as
656 calling "send". 671 calling "send".
657 672
658 $cv->croak ($error) 673 $cv->croak ($error)
659 Similar to send, but causes all call's to "->recv" to invoke 674 Similar to send, but causes all calls to "->recv" to invoke
660 "Carp::croak" with the given error message/object/scalar. 675 "Carp::croak" with the given error message/object/scalar.
661 676
662 This can be used to signal any errors to the condition variable 677 This can be used to signal any errors to the condition variable
663 user/consumer. Doing it this way instead of calling "croak" directly 678 user/consumer. Doing it this way instead of calling "croak" directly
664 delays the error detetcion, but has the overwhelmign advantage that 679 delays the error detection, but has the overwhelming advantage that
665 it diagnoses the error at the place where the result is expected, 680 it diagnoses the error at the place where the result is expected,
666 and not deep in some event clalback without connection to the actual 681 and not deep in some event callback with no connection to the actual
667 code causing the problem. 682 code causing the problem.
668 683
669 $cv->begin ([group callback]) 684 $cv->begin ([group callback])
670 $cv->end 685 $cv->end
671 These two methods can be used to combine many transactions/events 686 These two methods can be used to combine many transactions/events
708 there is one call to "begin", so the condvar waits for all calls to 723 there is one call to "begin", so the condvar waits for all calls to
709 "end" before sending. 724 "end" before sending.
710 725
711 The ping example mentioned above is slightly more complicated, as 726 The ping example mentioned above is slightly more complicated, as
712 the there are results to be passwd back, and the number of tasks 727 the there are results to be passwd back, and the number of tasks
713 that are begung can potentially be zero: 728 that are begun can potentially be zero:
714 729
715 my $cv = AnyEvent->condvar; 730 my $cv = AnyEvent->condvar;
716 731
717 my %result; 732 my %result;
718 $cv->begin (sub { shift->send (\%result) }); 733 $cv->begin (sub { shift->send (\%result) });
739 callback to be called once the counter reaches 0, and second, it 754 callback to be called once the counter reaches 0, and second, it
740 ensures that "send" is called even when "no" hosts are being pinged 755 ensures that "send" is called even when "no" hosts are being pinged
741 (the loop doesn't execute once). 756 (the loop doesn't execute once).
742 757
743 This is the general pattern when you "fan out" into multiple (but 758 This is the general pattern when you "fan out" into multiple (but
744 potentially none) subrequests: use an outer "begin"/"end" pair to 759 potentially zero) subrequests: use an outer "begin"/"end" pair to
745 set the callback and ensure "end" is called at least once, and then, 760 set the callback and ensure "end" is called at least once, and then,
746 for each subrequest you start, call "begin" and for each subrequest 761 for each subrequest you start, call "begin" and for each subrequest
747 you finish, call "end". 762 you finish, call "end".
748 763
749 METHODS FOR CONSUMERS 764 METHODS FOR CONSUMERS
750 These methods should only be used by the consuming side, i.e. the code 765 These methods should only be used by the consuming side, i.e. the code
751 awaits the condition. 766 awaits the condition.
752 767
753 $cv->recv 768 $cv->recv
754 Wait (blocking if necessary) until the "->send" or "->croak" methods 769 Wait (blocking if necessary) until the "->send" or "->croak" methods
755 have been called on c<$cv>, while servicing other watchers normally. 770 have been called on $cv, while servicing other watchers normally.
756 771
757 You can only wait once on a condition - additional calls are valid 772 You can only wait once on a condition - additional calls are valid
758 but will return immediately. 773 but will return immediately.
759 774
760 If an error condition has been set by calling "->croak", then this 775 If an error condition has been set by calling "->croak", then this
777 example, by coupling condition variables with some kind of request 792 example, by coupling condition variables with some kind of request
778 results and supporting callbacks so the caller knows that getting 793 results and supporting callbacks so the caller knows that getting
779 the result will not block, while still supporting blocking waits if 794 the result will not block, while still supporting blocking waits if
780 the caller so desires). 795 the caller so desires).
781 796
782 You can ensure that "-recv" never blocks by setting a callback and 797 You can ensure that "->recv" never blocks by setting a callback and
783 only calling "->recv" from within that callback (or at a later 798 only calling "->recv" from within that callback (or at a later
784 time). This will work even when the event loop does not support 799 time). This will work even when the event loop does not support
785 blocking waits otherwise. 800 blocking waits otherwise.
786 801
787 $bool = $cv->ready 802 $bool = $cv->ready
790 805
791 $cb = $cv->cb ($cb->($cv)) 806 $cb = $cv->cb ($cb->($cv))
792 This is a mutator function that returns the callback set and 807 This is a mutator function that returns the callback set and
793 optionally replaces it before doing so. 808 optionally replaces it before doing so.
794 809
795 The callback will be called when the condition becomes (or already 810 The callback will be called when the condition becomes "true", i.e.
796 was) "true", i.e. when "send" or "croak" are called (or were 811 when "send" or "croak" are called, with the only argument being the
797 called), with the only argument being the condition variable itself. 812 condition variable itself. If the condition is already true, the
798 Calling "recv" inside the callback or at any later time is 813 callback is called immediately when it is set. Calling "recv" inside
799 guaranteed not to block. 814 the callback or at any later time is guaranteed not to block.
800 815
801SUPPORTED EVENT LOOPS/BACKENDS 816SUPPORTED EVENT LOOPS/BACKENDS
802 The available backend classes are (every class has its own manpage): 817 The available backend classes are (every class has its own manpage):
803 818
804 Backends that are autoprobed when no other event loop can be found. 819 Backends that are autoprobed when no other event loop can be found.
809 824
810 AnyEvent::Impl::EV based on EV (interface to libev, best choice). 825 AnyEvent::Impl::EV based on EV (interface to libev, best choice).
811 AnyEvent::Impl::Perl pure-perl implementation, fast and portable. 826 AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
812 827
813 Backends that are transparently being picked up when they are used. 828 Backends that are transparently being picked up when they are used.
814 These will be used when they are currently loaded when the first 829 These will be used if they are already loaded when the first watcher
815 watcher is created, in which case it is assumed that the application 830 is created, in which case it is assumed that the application is
816 is using them. This means that AnyEvent will automatically pick the 831 using them. This means that AnyEvent will automatically pick the
817 right backend when the main program loads an event module before 832 right backend when the main program loads an event module before
818 anything starts to create watchers. Nothing special needs to be done 833 anything starts to create watchers. Nothing special needs to be done
819 by the main program. 834 by the main program.
820 835
821 AnyEvent::Impl::Event based on Event, very stable, few glitches. 836 AnyEvent::Impl::Event based on Event, very stable, few glitches.
822 AnyEvent::Impl::Glib based on Glib, slow but very stable. 837 AnyEvent::Impl::Glib based on Glib, slow but very stable.
823 AnyEvent::Impl::Tk based on Tk, very broken. 838 AnyEvent::Impl::Tk based on Tk, very broken.
824 AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse. 839 AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
825 AnyEvent::Impl::POE based on POE, very slow, some limitations. 840 AnyEvent::Impl::POE based on POE, very slow, some limitations.
826 AnyEvent::Impl::Irssi used when running within irssi. 841 AnyEvent::Impl::Irssi used when running within irssi.
842 AnyEvent::Impl::IOAsync based on IO::Async.
843 AnyEvent::Impl::Cocoa based on Cocoa::EventLoop.
827 844
828 Backends with special needs. 845 Backends with special needs.
829 Qt requires the Qt::Application to be instantiated first, but will 846 Qt requires the Qt::Application to be instantiated first, but will
830 otherwise be picked up automatically. As long as the main program 847 otherwise be picked up automatically. As long as the main program
831 instantiates the application before any AnyEvent watchers are 848 instantiates the application before any AnyEvent watchers are
832 created, everything should just work. 849 created, everything should just work.
833 850
834 AnyEvent::Impl::Qt based on Qt. 851 AnyEvent::Impl::Qt based on Qt.
835 852
836 Support for IO::Async can only be partial, as it is too broken and
837 architecturally limited to even support the AnyEvent API. It also is
838 the only event loop that needs the loop to be set explicitly, so it
839 can only be used by a main program knowing about AnyEvent. See
840 AnyEvent::Impl::Async for the gory details.
841
842 AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
843
844 Event loops that are indirectly supported via other backends. 853 Event loops that are indirectly supported via other backends.
845 Some event loops can be supported via other modules: 854 Some event loops can be supported via other modules:
846 855
847 There is no direct support for WxWidgets (Wx) or Prima. 856 There is no direct support for WxWidgets (Wx) or Prima.
848 857
866 Contains "undef" until the first watcher is being created, before 875 Contains "undef" until the first watcher is being created, before
867 the backend has been autodetected. 876 the backend has been autodetected.
868 877
869 Afterwards it contains the event model that is being used, which is 878 Afterwards it contains the event model that is being used, which is
870 the name of the Perl class implementing the model. This class is 879 the name of the Perl class implementing the model. This class is
871 usually one of the "AnyEvent::Impl:xxx" modules, but can be any 880 usually one of the "AnyEvent::Impl::xxx" modules, but can be any
872 other class in the case AnyEvent has been extended at runtime (e.g. 881 other class in the case AnyEvent has been extended at runtime (e.g.
873 in *rxvt-unicode* it will be "urxvt::anyevent"). 882 in *rxvt-unicode* it will be "urxvt::anyevent").
874 883
875 AnyEvent::detect 884 AnyEvent::detect
876 Returns $AnyEvent::MODEL, forcing autodetection of the event model 885 Returns $AnyEvent::MODEL, forcing autodetection of the event model
877 if necessary. You should only call this function right before you 886 if necessary. You should only call this function right before you
878 would have created an AnyEvent watcher anyway, that is, as late as 887 would have created an AnyEvent watcher anyway, that is, as late as
879 possible at runtime, and not e.g. while initialising of your module. 888 possible at runtime, and not e.g. during initialisation of your
889 module.
880 890
881 If you need to do some initialisation before AnyEvent watchers are 891 If you need to do some initialisation before AnyEvent watchers are
882 created, use "post_detect". 892 created, use "post_detect".
883 893
884 $guard = AnyEvent::post_detect { BLOCK } 894 $guard = AnyEvent::post_detect { BLOCK }
885 Arranges for the code block to be executed as soon as the event 895 Arranges for the code block to be executed as soon as the event
886 model is autodetected (or immediately if this has already happened). 896 model is autodetected (or immediately if that has already happened).
887 897
888 The block will be executed *after* the actual backend has been 898 The block will be executed *after* the actual backend has been
889 detected ($AnyEvent::MODEL is set), but *before* any watchers have 899 detected ($AnyEvent::MODEL is set), but *before* any watchers have
890 been created, so it is possible to e.g. patch @AnyEvent::ISA or do 900 been created, so it is possible to e.g. patch @AnyEvent::ISA or do
891 other initialisations - see the sources of AnyEvent::Strict or 901 other initialisations - see the sources of AnyEvent::Strict or
900 object that automatically removes the callback again when it is 910 object that automatically removes the callback again when it is
901 destroyed (or "undef" when the hook was immediately executed). See 911 destroyed (or "undef" when the hook was immediately executed). See
902 AnyEvent::AIO for a case where this is useful. 912 AnyEvent::AIO for a case where this is useful.
903 913
904 Example: Create a watcher for the IO::AIO module and store it in 914 Example: Create a watcher for the IO::AIO module and store it in
905 $WATCHER. Only do so after the event loop is initialised, though. 915 $WATCHER, but do so only do so after the event loop is initialised.
906 916
907 our WATCHER; 917 our WATCHER;
908 918
909 my $guard = AnyEvent::post_detect { 919 my $guard = AnyEvent::post_detect {
910 $WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb); 920 $WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
917 927
918 $WATCHER ||= $guard; 928 $WATCHER ||= $guard;
919 929
920 @AnyEvent::post_detect 930 @AnyEvent::post_detect
921 If there are any code references in this array (you can "push" to it 931 If there are any code references in this array (you can "push" to it
922 before or after loading AnyEvent), then they will called directly 932 before or after loading AnyEvent), then they will be called directly
923 after the event loop has been chosen. 933 after the event loop has been chosen.
924 934
925 You should check $AnyEvent::MODEL before adding to this array, 935 You should check $AnyEvent::MODEL before adding to this array,
926 though: if it is defined then the event loop has already been 936 though: if it is defined then the event loop has already been
927 detected, and the array will be ignored. 937 detected, and the array will be ignored.
962 stall the whole program, and the whole point of using events is to stay 972 stall the whole program, and the whole point of using events is to stay
963 interactive. 973 interactive.
964 974
965 It is fine, however, to call "->recv" when the user of your module 975 It is fine, however, to call "->recv" when the user of your module
966 requests it (i.e. if you create a http request object ad have a method 976 requests it (i.e. if you create a http request object ad have a method
967 called "results" that returns the results, it should call "->recv" 977 called "results" that returns the results, it may call "->recv" freely,
968 freely, as the user of your module knows what she is doing. always). 978 as the user of your module knows what she is doing. Always).
969 979
970WHAT TO DO IN THE MAIN PROGRAM 980WHAT TO DO IN THE MAIN PROGRAM
971 There will always be a single main program - the only place that should 981 There will always be a single main program - the only place that should
972 dictate which event model to use. 982 dictate which event model to use.
973 983
974 If it doesn't care, it can just "use AnyEvent" and use it itself, or not 984 If the program is not event-based, it need not do anything special, even
975 do anything special (it does not need to be event-based) and let 985 when it depends on a module that uses an AnyEvent. If the program itself
976 AnyEvent decide which implementation to chose if some module relies on 986 uses AnyEvent, but does not care which event loop is used, all it needs
977 it. 987 to do is "use AnyEvent". In either case, AnyEvent will choose the best
988 available loop implementation.
978 989
979 If the main program relies on a specific event model - for example, in 990 If the main program relies on a specific event model - for example, in
980 Gtk2 programs you have to rely on the Glib module - you should load the 991 Gtk2 programs you have to rely on the Glib module - you should load the
981 event module before loading AnyEvent or any module that uses it: 992 event module before loading AnyEvent or any module that uses it:
982 generally speaking, you should load it as early as possible. The reason 993 generally speaking, you should load it as early as possible. The reason
983 is that modules might create watchers when they are loaded, and AnyEvent 994 is that modules might create watchers when they are loaded, and AnyEvent
984 will decide on the event model to use as soon as it creates watchers, 995 will decide on the event model to use as soon as it creates watchers,
985 and it might chose the wrong one unless you load the correct one 996 and it might choose the wrong one unless you load the correct one
986 yourself. 997 yourself.
987 998
988 You can chose to use a pure-perl implementation by loading the 999 You can chose to use a pure-perl implementation by loading the
989 "AnyEvent::Impl::Perl" module, which gives you similar behaviour 1000 "AnyEvent::Impl::Perl" module, which gives you similar behaviour
990 everywhere, but letting AnyEvent chose the model is generally better. 1001 everywhere, but letting AnyEvent chose the model is generally better.
1007 1018
1008OTHER MODULES 1019OTHER MODULES
1009 The following is a non-exhaustive list of additional modules that use 1020 The following is a non-exhaustive list of additional modules that use
1010 AnyEvent as a client and can therefore be mixed easily with other 1021 AnyEvent as a client and can therefore be mixed easily with other
1011 AnyEvent modules and other event loops in the same program. Some of the 1022 AnyEvent modules and other event loops in the same program. Some of the
1012 modules come with AnyEvent, most are available via CPAN. 1023 modules come as part of AnyEvent, the others are available via CPAN.
1013 1024
1014 AnyEvent::Util 1025 AnyEvent::Util
1015 Contains various utility functions that replace often-used but 1026 Contains various utility functions that replace often-used blocking
1016 blocking functions such as "inet_aton" by event-/callback-based 1027 functions such as "inet_aton" with event/callback-based versions.
1017 versions.
1018 1028
1019 AnyEvent::Socket 1029 AnyEvent::Socket
1020 Provides various utility functions for (internet protocol) sockets, 1030 Provides various utility functions for (internet protocol) sockets,
1021 addresses and name resolution. Also functions to create non-blocking 1031 addresses and name resolution. Also functions to create non-blocking
1022 tcp connections or tcp servers, with IPv6 and SRV record support and 1032 tcp connections or tcp servers, with IPv6 and SRV record support and
1023 more. 1033 more.
1024 1034
1025 AnyEvent::Handle 1035 AnyEvent::Handle
1026 Provide read and write buffers, manages watchers for reads and 1036 Provide read and write buffers, manages watchers for reads and
1027 writes, supports raw and formatted I/O, I/O queued and fully 1037 writes, supports raw and formatted I/O, I/O queued and fully
1028 transparent and non-blocking SSL/TLS (via AnyEvent::TLS. 1038 transparent and non-blocking SSL/TLS (via AnyEvent::TLS).
1029 1039
1030 AnyEvent::DNS 1040 AnyEvent::DNS
1031 Provides rich asynchronous DNS resolver capabilities. 1041 Provides rich asynchronous DNS resolver capabilities.
1032 1042
1043 AnyEvent::HTTP, AnyEvent::IRC, AnyEvent::XMPP, AnyEvent::GPSD,
1044 AnyEvent::IGS, AnyEvent::FCP
1045 Implement event-based interfaces to the protocols of the same name
1046 (for the curious, IGS is the International Go Server and FCP is the
1047 Freenet Client Protocol).
1048
1049 AnyEvent::Handle::UDP
1050 Here be danger!
1051
1052 As Pauli would put it, "Not only is it not right, it's not even
1053 wrong!" - there are so many things wrong with AnyEvent::Handle::UDP,
1054 most notably its use of a stream-based API with a protocol that
1055 isn't streamable, that the only way to improve it is to delete it.
1056
1057 It features data corruption (but typically only under load) and
1058 general confusion. On top, the author is not only clueless about UDP
1059 but also fact-resistant - some gems of his understanding: "connect
1060 doesn't work with UDP", "UDP packets are not IP packets", "UDP only
1061 has datagrams, not packets", "I don't need to implement proper error
1062 checking as UDP doesn't support error checking" and so on - he
1063 doesn't even understand what's wrong with his module when it is
1064 explained to him.
1065
1033 AnyEvent::HTTP 1066 AnyEvent::DBI
1034 A simple-to-use HTTP library that is capable of making a lot of 1067 Executes DBI requests asynchronously in a proxy process for you,
1035 concurrent HTTP requests. 1068 notifying you in an event-based way when the operation is finished.
1069
1070 AnyEvent::AIO
1071 Truly asynchronous (as opposed to non-blocking) I/O, should be in
1072 the toolbox of every event programmer. AnyEvent::AIO transparently
1073 fuses IO::AIO and AnyEvent together, giving AnyEvent access to
1074 event-based file I/O, and much more.
1036 1075
1037 AnyEvent::HTTPD 1076 AnyEvent::HTTPD
1038 Provides a simple web application server framework. 1077 A simple embedded webserver.
1039 1078
1040 AnyEvent::FastPing 1079 AnyEvent::FastPing
1041 The fastest ping in the west. 1080 The fastest ping in the west.
1042
1043 AnyEvent::DBI
1044 Executes DBI requests asynchronously in a proxy process.
1045
1046 AnyEvent::AIO
1047 Truly asynchronous I/O, should be in the toolbox of every event
1048 programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent
1049 together.
1050
1051 AnyEvent::BDB
1052 Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently
1053 fuses BDB and AnyEvent together.
1054
1055 AnyEvent::GPSD
1056 A non-blocking interface to gpsd, a daemon delivering GPS
1057 information.
1058
1059 AnyEvent::IRC
1060 AnyEvent based IRC client module family (replacing the older
1061 Net::IRC3).
1062
1063 AnyEvent::XMPP
1064 AnyEvent based XMPP (Jabber protocol) module family (replacing the
1065 older Net::XMPP2>.
1066
1067 AnyEvent::IGS
1068 A non-blocking interface to the Internet Go Server protocol (used by
1069 App::IGS).
1070
1071 Net::FCP
1072 AnyEvent-based implementation of the Freenet Client Protocol,
1073 birthplace of AnyEvent.
1074
1075 Event::ExecFlow
1076 High level API for event-based execution flow control.
1077 1081
1078 Coro 1082 Coro
1079 Has special support for AnyEvent via Coro::AnyEvent. 1083 Has special support for AnyEvent via Coro::AnyEvent.
1080 1084
1081SIMPLIFIED AE API 1085SIMPLIFIED AE API
1132 thoroughly check the arguments passed to most method calls. If it 1136 thoroughly check the arguments passed to most method calls. If it
1133 finds any problems, it will croak. 1137 finds any problems, it will croak.
1134 1138
1135 In other words, enables "strict" mode. 1139 In other words, enables "strict" mode.
1136 1140
1137 Unlike "use strict" (or it's modern cousin, "use common::sense", it 1141 Unlike "use strict" (or its modern cousin, "use common::sense", it
1138 is definitely recommended to keep it off in production. Keeping 1142 is definitely recommended to keep it off in production. Keeping
1139 "PERL_ANYEVENT_STRICT=1" in your environment while developing 1143 "PERL_ANYEVENT_STRICT=1" in your environment while developing
1140 programs can be very useful, however. 1144 programs can be very useful, however.
1141 1145
1142 "PERL_ANYEVENT_MODEL" 1146 "PERL_ANYEVENT_MODEL"
1738 1742
1739 Feel free to install your own handler, or reset it to defaults. 1743 Feel free to install your own handler, or reset it to defaults.
1740 1744
1741RECOMMENDED/OPTIONAL MODULES 1745RECOMMENDED/OPTIONAL MODULES
1742 One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and 1746 One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
1743 it's built-in modules) are required to use it. 1747 its built-in modules) are required to use it.
1744 1748
1745 That does not mean that AnyEvent won't take advantage of some additional 1749 That does not mean that AnyEvent won't take advantage of some additional
1746 modules if they are installed. 1750 modules if they are installed.
1747 1751
1748 This section explains which additional modules will be used, and how 1752 This section explains which additional modules will be used, and how
1799 worthwhile: If this module is installed, then AnyEvent::Handle (with 1803 worthwhile: If this module is installed, then AnyEvent::Handle (with
1800 the help of AnyEvent::TLS), gains the ability to do TLS/SSL. 1804 the help of AnyEvent::TLS), gains the ability to do TLS/SSL.
1801 1805
1802 Time::HiRes 1806 Time::HiRes
1803 This module is part of perl since release 5.008. It will be used 1807 This module is part of perl since release 5.008. It will be used
1804 when the chosen event library does not come with a timing source on 1808 when the chosen event library does not come with a timing source of
1805 it's own. The pure-perl event loop (AnyEvent::Impl::Perl) will 1809 its own. The pure-perl event loop (AnyEvent::Impl::Perl) will
1806 additionally use it to try to use a monotonic clock for timing 1810 additionally use it to try to use a monotonic clock for timing
1807 stability. 1811 stability.
1808 1812
1809FORK 1813FORK
1810 Most event libraries are not fork-safe. The ones who are usually are 1814 Most event libraries are not fork-safe. The ones who are usually are
1863 5.10 and check wether the leaks still show up. (Perl 5.10.0 has other 1867 5.10 and check wether the leaks still show up. (Perl 5.10.0 has other
1864 annoying memleaks, such as leaking on "map" and "grep" but it is usually 1868 annoying memleaks, such as leaking on "map" and "grep" but it is usually
1865 not as pronounced). 1869 not as pronounced).
1866 1870
1867SEE ALSO 1871SEE ALSO
1872 Tutorial/Introduction: AnyEvent::Intro.
1873
1874 FAQ: AnyEvent::FAQ.
1875
1868 Utility functions: AnyEvent::Util. 1876 Utility functions: AnyEvent::Util.
1869 1877
1870 Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk, 1878 Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk,
1871 Event::Lib, Qt, POE. 1879 Event::Lib, Qt, POE.
1872 1880
1878 Non-blocking file handles, sockets, TCP clients and servers: 1886 Non-blocking file handles, sockets, TCP clients and servers:
1879 AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS. 1887 AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS.
1880 1888
1881 Asynchronous DNS: AnyEvent::DNS. 1889 Asynchronous DNS: AnyEvent::DNS.
1882 1890
1883 Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event, 1891 Thread support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event.
1884 1892
1885 Nontrivial usage examples: AnyEvent::GPSD, AnyEvent::XMPP, 1893 Nontrivial usage examples: AnyEvent::GPSD, AnyEvent::IRC,
1886 AnyEvent::HTTP. 1894 AnyEvent::HTTP.
1887 1895
1888AUTHOR 1896AUTHOR
1889 Marc Lehmann <schmorp@schmorp.de> 1897 Marc Lehmann <schmorp@schmorp.de>
1890 http://home.schmorp.de/ 1898 http://home.schmorp.de/

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