ViewVC Help
View File | Revision Log | Show Annotations | Download File
/cvs/AnyEvent/README
(Generate patch)

Comparing AnyEvent/README (file contents):
Revision 1.41 by root, Fri Jun 26 06:33:17 2009 UTC vs.
Revision 1.50 by root, Sat Aug 1 09:14:54 2009 UTC

1NAME 1NAME
2 AnyEvent - provide framework for multiple event loops 2 AnyEvent - the DBI of event loop programming
3 3
4 EV, Event, Glib, Tk, Perl, Event::Lib, Qt and POE are various supported 4 EV, Event, Glib, Tk, Perl, Event::Lib, Irssi, rxvt-unicode, IO::Async,
5 event loops. 5 Qt and POE are various supported event loops/environments.
6 6
7SYNOPSIS 7SYNOPSIS
8 use AnyEvent; 8 use AnyEvent;
9 9
10 # file descriptor readable 10 # file descriptor readable
… …
37 37
38INTRODUCTION/TUTORIAL 38INTRODUCTION/TUTORIAL
39 This manpage is mainly a reference manual. If you are interested in a 39 This manpage is mainly a reference manual. If you are interested in a
40 tutorial or some gentle introduction, have a look at the AnyEvent::Intro 40 tutorial or some gentle introduction, have a look at the AnyEvent::Intro
41 manpage. 41 manpage.
42
43SUPPORT
44 There is a mailinglist for discussing all things AnyEvent, and an IRC
45 channel, too.
46
47 See the AnyEvent project page at the Schmorpforge Ta-Sa Software
48 Repository, at <http://anyevent.schmorp.de>, for more info.
42 49
43WHY YOU SHOULD USE THIS MODULE (OR NOT) 50WHY YOU SHOULD USE THIS MODULE (OR NOT)
44 Glib, POE, IO::Async, Event... CPAN offers event models by the dozen 51 Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
45 nowadays. So what is different about AnyEvent? 52 nowadays. So what is different about AnyEvent?
46 53
… …
166 Note that "my $w; $w =" combination. This is necessary because in Perl, 173 Note that "my $w; $w =" combination. This is necessary because in Perl,
167 my variables are only visible after the statement in which they are 174 my variables are only visible after the statement in which they are
168 declared. 175 declared.
169 176
170 I/O WATCHERS 177 I/O WATCHERS
178 $w = AnyEvent->io (
179 fh => <filehandle_or_fileno>,
180 poll => <"r" or "w">,
181 cb => <callback>,
182 );
183
171 You can create an I/O watcher by calling the "AnyEvent->io" method with 184 You can create an I/O watcher by calling the "AnyEvent->io" method with
172 the following mandatory key-value pairs as arguments: 185 the following mandatory key-value pairs as arguments:
173 186
174 "fh" is the Perl *file handle* (*not* file descriptor) to watch for 187 "fh" is the Perl *file handle* (or a naked file descriptor) to watch for
175 events (AnyEvent might or might not keep a reference to this file 188 events (AnyEvent might or might not keep a reference to this file
176 handle). Note that only file handles pointing to things for which 189 handle). Note that only file handles pointing to things for which
177 non-blocking operation makes sense are allowed. This includes sockets, 190 non-blocking operation makes sense are allowed. This includes sockets,
178 most character devices, pipes, fifos and so on, but not for example 191 most character devices, pipes, fifos and so on, but not for example
179 files or block devices. 192 files or block devices.
… …
203 warn "read: $input\n"; 216 warn "read: $input\n";
204 undef $w; 217 undef $w;
205 }); 218 });
206 219
207 TIME WATCHERS 220 TIME WATCHERS
221 $w = AnyEvent->timer (after => <seconds>, cb => <callback>);
222
223 $w = AnyEvent->timer (
224 after => <fractional_seconds>,
225 interval => <fractional_seconds>,
226 cb => <callback>,
227 );
228
208 You can create a time watcher by calling the "AnyEvent->timer" method 229 You can create a time watcher by calling the "AnyEvent->timer" method
209 with the following mandatory arguments: 230 with the following mandatory arguments:
210 231
211 "after" specifies after how many seconds (fractional values are 232 "after" specifies after how many seconds (fractional values are
212 supported) the callback should be invoked. "cb" is the callback to 233 supported) the callback should be invoked. "cb" is the callback to
… …
336 the event loop's idea of "current time". 357 the event loop's idea of "current time".
337 358
338 Note that updating the time *might* cause some events to be handled. 359 Note that updating the time *might* cause some events to be handled.
339 360
340 SIGNAL WATCHERS 361 SIGNAL WATCHERS
362 $w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
363
341 You can watch for signals using a signal watcher, "signal" is the signal 364 You can watch for signals using a signal watcher, "signal" is the signal
342 *name* in uppercase and without any "SIG" prefix, "cb" is the Perl 365 *name* in uppercase and without any "SIG" prefix, "cb" is the Perl
343 callback to be invoked whenever a signal occurs. 366 callback to be invoked whenever a signal occurs.
344 367
345 Although the callback might get passed parameters, their value and 368 Although the callback might get passed parameters, their value and
… …
350 invocation, and callback invocation will be synchronous. Synchronous 373 invocation, and callback invocation will be synchronous. Synchronous
351 means that it might take a while until the signal gets handled by the 374 means that it might take a while until the signal gets handled by the
352 process, but it is guaranteed not to interrupt any other callbacks. 375 process, but it is guaranteed not to interrupt any other callbacks.
353 376
354 The main advantage of using these watchers is that you can share a 377 The main advantage of using these watchers is that you can share a
355 signal between multiple watchers. 378 signal between multiple watchers, and AnyEvent will ensure that signals
379 will not interrupt your program at bad times.
356 380
357 This watcher might use %SIG, so programs overwriting those signals 381 This watcher might use %SIG (depending on the event loop used), so
358 directly will likely not work correctly. 382 programs overwriting those signals directly will likely not work
383 correctly.
359 384
360 Example: exit on SIGINT 385 Example: exit on SIGINT
361 386
362 my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 }); 387 my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
363 388
389 Signal Races, Delays and Workarounds
390 Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
391 callbacks to signals in a generic way, which is a pity, as you cannot do
392 race-free signal handling in perl, requiring C libraries for this.
393 AnyEvent will try to do it's best, which means in some cases, signals
394 will be delayed. The maximum time a signal might be delayed is specified
395 in $AnyEvent::MAX_SIGNAL_LATENCY (default: 10 seconds). This variable
396 can be changed only before the first signal watcher is created, and
397 should be left alone otherwise. This variable determines how often
398 AnyEvent polls for signals (in case a wake-up was missed). Higher values
399 will cause fewer spurious wake-ups, which is better for power and CPU
400 saving.
401
402 All these problems can be avoided by installing the optional
403 Async::Interrupt module, which works with most event loops. It will not
404 work with inherently broken event loops such as Event or Event::Lib (and
405 not with POE currently, as POE does it's own workaround with one-second
406 latency). For those, you just have to suffer the delays.
407
364 CHILD PROCESS WATCHERS 408 CHILD PROCESS WATCHERS
409 $w = AnyEvent->child (pid => <process id>, cb => <callback>);
410
365 You can also watch on a child process exit and catch its exit status. 411 You can also watch on a child process exit and catch its exit status.
366 412
367 The child process is specified by the "pid" argument (if set to 0, it 413 The child process is specified by the "pid" argument (one some backends,
368 watches for any child process exit). The watcher will triggered only 414 using 0 watches for any child process exit, on others this will croak).
369 when the child process has finished and an exit status is available, not 415 The watcher will be triggered only when the child process has finished
370 on any trace events (stopped/continued). 416 and an exit status is available, not on any trace events
417 (stopped/continued).
371 418
372 The callback will be called with the pid and exit status (as returned by 419 The callback will be called with the pid and exit status (as returned by
373 waitpid), so unlike other watcher types, you *can* rely on child watcher 420 waitpid), so unlike other watcher types, you *can* rely on child watcher
374 callback arguments. 421 callback arguments.
375 422
… …
390 of when you start the watcher. 437 of when you start the watcher.
391 438
392 This means you cannot create a child watcher as the very first thing in 439 This means you cannot create a child watcher as the very first thing in
393 an AnyEvent program, you *have* to create at least one watcher before 440 an AnyEvent program, you *have* to create at least one watcher before
394 you "fork" the child (alternatively, you can call "AnyEvent::detect"). 441 you "fork" the child (alternatively, you can call "AnyEvent::detect").
442
443 As most event loops do not support waiting for child events, they will
444 be emulated by AnyEvent in most cases, in which the latency and race
445 problems mentioned in the description of signal watchers apply.
395 446
396 Example: fork a process and wait for it 447 Example: fork a process and wait for it
397 448
398 my $done = AnyEvent->condvar; 449 my $done = AnyEvent->condvar;
399 450
… …
410 461
411 # do something else, then wait for process exit 462 # do something else, then wait for process exit
412 $done->recv; 463 $done->recv;
413 464
414 IDLE WATCHERS 465 IDLE WATCHERS
466 $w = AnyEvent->idle (cb => <callback>);
467
415 Sometimes there is a need to do something, but it is not so important to 468 Sometimes there is a need to do something, but it is not so important to
416 do it instantly, but only when there is nothing better to do. This 469 do it instantly, but only when there is nothing better to do. This
417 "nothing better to do" is usually defined to be "no other events need 470 "nothing better to do" is usually defined to be "no other events need
418 attention by the event loop". 471 attention by the event loop".
419 472
… …
444 } 497 }
445 }); 498 });
446 }); 499 });
447 500
448 CONDITION VARIABLES 501 CONDITION VARIABLES
502 $cv = AnyEvent->condvar;
503
504 $cv->send (<list>);
505 my @res = $cv->recv;
506
449 If you are familiar with some event loops you will know that all of them 507 If you are familiar with some event loops you will know that all of them
450 require you to run some blocking "loop", "run" or similar function that 508 require you to run some blocking "loop", "run" or similar function that
451 will actively watch for new events and call your callbacks. 509 will actively watch for new events and call your callbacks.
452 510
453 AnyEvent is different, it expects somebody else to run the event loop 511 AnyEvent is slightly different: it expects somebody else to run the
454 and will only block when necessary (usually when told by the user). 512 event loop and will only block when necessary (usually when told by the
513 user).
455 514
456 The instrument to do that is called a "condition variable", so called 515 The instrument to do that is called a "condition variable", so called
457 because they represent a condition that must become true. 516 because they represent a condition that must become true.
458 517
518 Now is probably a good time to look at the examples further below.
519
459 Condition variables can be created by calling the "AnyEvent->condvar" 520 Condition variables can be created by calling the "AnyEvent->condvar"
460 method, usually without arguments. The only argument pair allowed is 521 method, usually without arguments. The only argument pair allowed is
461
462 "cb", which specifies a callback to be called when the condition 522 "cb", which specifies a callback to be called when the condition
463 variable becomes true, with the condition variable as the first argument 523 variable becomes true, with the condition variable as the first argument
464 (but not the results). 524 (but not the results).
465 525
466 After creation, the condition variable is "false" until it becomes 526 After creation, the condition variable is "false" until it becomes
… …
471 Condition variables are similar to callbacks, except that you can 531 Condition variables are similar to callbacks, except that you can
472 optionally wait for them. They can also be called merge points - points 532 optionally wait for them. They can also be called merge points - points
473 in time where multiple outstanding events have been processed. And yet 533 in time where multiple outstanding events have been processed. And yet
474 another way to call them is transactions - each condition variable can 534 another way to call them is transactions - each condition variable can
475 be used to represent a transaction, which finishes at some point and 535 be used to represent a transaction, which finishes at some point and
476 delivers a result. 536 delivers a result. And yet some people know them as "futures" - a
537 promise to compute/deliver something that you can wait for.
477 538
478 Condition variables are very useful to signal that something has 539 Condition variables are very useful to signal that something has
479 finished, for example, if you write a module that does asynchronous http 540 finished, for example, if you write a module that does asynchronous http
480 requests, then a condition variable would be the ideal candidate to 541 requests, then a condition variable would be the ideal candidate to
481 signal the availability of results. The user can either act when the 542 signal the availability of results. The user can either act when the
… …
515 after => 1, 576 after => 1,
516 cb => sub { $result_ready->send }, 577 cb => sub { $result_ready->send },
517 ); 578 );
518 579
519 # this "blocks" (while handling events) till the callback 580 # this "blocks" (while handling events) till the callback
520 # calls send 581 # calls -<send
521 $result_ready->recv; 582 $result_ready->recv;
522 583
523 Example: wait for a timer, but take advantage of the fact that condition 584 Example: wait for a timer, but take advantage of the fact that condition
524 variables are also code references. 585 variables are also callable directly.
525 586
526 my $done = AnyEvent->condvar; 587 my $done = AnyEvent->condvar;
527 my $delay = AnyEvent->timer (after => 5, cb => $done); 588 my $delay = AnyEvent->timer (after => 5, cb => $done);
528 $done->recv; 589 $done->recv;
529 590
… …
535 596
536 ... 597 ...
537 598
538 my @info = $couchdb->info->recv; 599 my @info = $couchdb->info->recv;
539 600
540 And this is how you would just ste a callback to be called whenever the 601 And this is how you would just set a callback to be called whenever the
541 results are available: 602 results are available:
542 603
543 $couchdb->info->cb (sub { 604 $couchdb->info->cb (sub {
544 my @info = $_[0]->recv; 605 my @info = $_[0]->recv;
545 }); 606 });
… …
560 621
561 Any arguments passed to the "send" call will be returned by all 622 Any arguments passed to the "send" call will be returned by all
562 future "->recv" calls. 623 future "->recv" calls.
563 624
564 Condition variables are overloaded so one can call them directly (as 625 Condition variables are overloaded so one can call them directly (as
565 a code reference). Calling them directly is the same as calling 626 if they were a code reference). Calling them directly is the same as
566 "send". Note, however, that many C-based event loops do not handle 627 calling "send".
567 overloading, so as tempting as it may be, passing a condition
568 variable instead of a callback does not work. Both the pure perl and
569 EV loops support overloading, however, as well as all functions that
570 use perl to invoke a callback (as in AnyEvent::Socket and
571 AnyEvent::DNS for example).
572 628
573 $cv->croak ($error) 629 $cv->croak ($error)
574 Similar to send, but causes all call's to "->recv" to invoke 630 Similar to send, but causes all call's to "->recv" to invoke
575 "Carp::croak" with the given error message/object/scalar. 631 "Carp::croak" with the given error message/object/scalar.
576 632
577 This can be used to signal any errors to the condition variable 633 This can be used to signal any errors to the condition variable
578 user/consumer. 634 user/consumer. Doing it this way instead of calling "croak" directly
635 delays the error detetcion, but has the overwhelmign advantage that
636 it diagnoses the error at the place where the result is expected,
637 and not deep in some event clalback without connection to the actual
638 code causing the problem.
579 639
580 $cv->begin ([group callback]) 640 $cv->begin ([group callback])
581 $cv->end 641 $cv->end
582 These two methods are EXPERIMENTAL and MIGHT CHANGE.
583
584 These two methods can be used to combine many transactions/events 642 These two methods can be used to combine many transactions/events
585 into one. For example, a function that pings many hosts in parallel 643 into one. For example, a function that pings many hosts in parallel
586 might want to use a condition variable for the whole process. 644 might want to use a condition variable for the whole process.
587 645
588 Every call to "->begin" will increment a counter, and every call to 646 Every call to "->begin" will increment a counter, and every call to
589 "->end" will decrement it. If the counter reaches 0 in "->end", the 647 "->end" will decrement it. If the counter reaches 0 in "->end", the
590 (last) callback passed to "begin" will be executed. That callback is 648 (last) callback passed to "begin" will be executed. That callback is
591 *supposed* to call "->send", but that is not required. If no 649 *supposed* to call "->send", but that is not required. If no
592 callback was set, "send" will be called without any arguments. 650 callback was set, "send" will be called without any arguments.
593 651
594 Let's clarify this with the ping example: 652 You can think of "$cv->send" giving you an OR condition (one call
653 sends), while "$cv->begin" and "$cv->end" giving you an AND
654 condition (all "begin" calls must be "end"'ed before the condvar
655 sends).
656
657 Let's start with a simple example: you have two I/O watchers (for
658 example, STDOUT and STDERR for a program), and you want to wait for
659 both streams to close before activating a condvar:
660
661 my $cv = AnyEvent->condvar;
662
663 $cv->begin; # first watcher
664 my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
665 defined sysread $fh1, my $buf, 4096
666 or $cv->end;
667 });
668
669 $cv->begin; # second watcher
670 my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
671 defined sysread $fh2, my $buf, 4096
672 or $cv->end;
673 });
674
675 $cv->recv;
676
677 This works because for every event source (EOF on file handle),
678 there is one call to "begin", so the condvar waits for all calls to
679 "end" before sending.
680
681 The ping example mentioned above is slightly more complicated, as
682 the there are results to be passwd back, and the number of tasks
683 that are begung can potentially be zero:
595 684
596 my $cv = AnyEvent->condvar; 685 my $cv = AnyEvent->condvar;
597 686
598 my %result; 687 my %result;
599 $cv->begin (sub { $cv->send (\%result) }); 688 $cv->begin (sub { $cv->send (\%result) });
… …
619 the loop, which serves two important purposes: first, it sets the 708 the loop, which serves two important purposes: first, it sets the
620 callback to be called once the counter reaches 0, and second, it 709 callback to be called once the counter reaches 0, and second, it
621 ensures that "send" is called even when "no" hosts are being pinged 710 ensures that "send" is called even when "no" hosts are being pinged
622 (the loop doesn't execute once). 711 (the loop doesn't execute once).
623 712
624 This is the general pattern when you "fan out" into multiple 713 This is the general pattern when you "fan out" into multiple (but
625 subrequests: use an outer "begin"/"end" pair to set the callback and 714 potentially none) subrequests: use an outer "begin"/"end" pair to
626 ensure "end" is called at least once, and then, for each subrequest 715 set the callback and ensure "end" is called at least once, and then,
627 you start, call "begin" and for each subrequest you finish, call 716 for each subrequest you start, call "begin" and for each subrequest
628 "end". 717 you finish, call "end".
629 718
630 METHODS FOR CONSUMERS 719 METHODS FOR CONSUMERS
631 These methods should only be used by the consuming side, i.e. the code 720 These methods should only be used by the consuming side, i.e. the code
632 awaits the condition. 721 awaits the condition.
633 722
… …
642 function will call "croak". 731 function will call "croak".
643 732
644 In list context, all parameters passed to "send" will be returned, 733 In list context, all parameters passed to "send" will be returned,
645 in scalar context only the first one will be returned. 734 in scalar context only the first one will be returned.
646 735
736 Note that doing a blocking wait in a callback is not supported by
737 any event loop, that is, recursive invocation of a blocking "->recv"
738 is not allowed, and the "recv" call will "croak" if such a condition
739 is detected. This condition can be slightly loosened by using
740 Coro::AnyEvent, which allows you to do a blocking "->recv" from any
741 thread that doesn't run the event loop itself.
742
647 Not all event models support a blocking wait - some die in that case 743 Not all event models support a blocking wait - some die in that case
648 (programs might want to do that to stay interactive), so *if you are 744 (programs might want to do that to stay interactive), so *if you are
649 using this from a module, never require a blocking wait*, but let 745 using this from a module, never require a blocking wait*. Instead,
650 the caller decide whether the call will block or not (for example, 746 let the caller decide whether the call will block or not (for
651 by coupling condition variables with some kind of request results 747 example, by coupling condition variables with some kind of request
652 and supporting callbacks so the caller knows that getting the result 748 results and supporting callbacks so the caller knows that getting
653 will not block, while still supporting blocking waits if the caller 749 the result will not block, while still supporting blocking waits if
654 so desires). 750 the caller so desires).
655
656 Another reason *never* to "->recv" in a module is that you cannot
657 sensibly have two "->recv"'s in parallel, as that would require
658 multiple interpreters or coroutines/threads, none of which
659 "AnyEvent" can supply.
660
661 The Coro module, however, *can* and *does* supply coroutines and, in
662 fact, Coro::AnyEvent replaces AnyEvent's condvars by coroutine-safe
663 versions and also integrates coroutines into AnyEvent, making
664 blocking "->recv" calls perfectly safe as long as they are done from
665 another coroutine (one that doesn't run the event loop).
666 751
667 You can ensure that "-recv" never blocks by setting a callback and 752 You can ensure that "-recv" never blocks by setting a callback and
668 only calling "->recv" from within that callback (or at a later 753 only calling "->recv" from within that callback (or at a later
669 time). This will work even when the event loop does not support 754 time). This will work even when the event loop does not support
670 blocking waits otherwise. 755 blocking waits otherwise.
… …
675 760
676 $cb = $cv->cb ($cb->($cv)) 761 $cb = $cv->cb ($cb->($cv))
677 This is a mutator function that returns the callback set and 762 This is a mutator function that returns the callback set and
678 optionally replaces it before doing so. 763 optionally replaces it before doing so.
679 764
680 The callback will be called when the condition becomes "true", i.e. 765 The callback will be called when the condition becomes (or already
681 when "send" or "croak" are called, with the only argument being the 766 was) "true", i.e. when "send" or "croak" are called (or were
682 condition variable itself. Calling "recv" inside the callback or at 767 called), with the only argument being the condition variable itself.
768 Calling "recv" inside the callback or at any later time is
683 any later time is guaranteed not to block. 769 guaranteed not to block.
770
771SUPPORTED EVENT LOOPS/BACKENDS
772 The available backend classes are (every class has its own manpage):
773
774 Backends that are autoprobed when no other event loop can be found.
775 EV is the preferred backend when no other event loop seems to be in
776 use. If EV is not installed, then AnyEvent will try Event, and,
777 failing that, will fall back to its own pure-perl implementation,
778 which is available everywhere as it comes with AnyEvent itself.
779
780 AnyEvent::Impl::EV based on EV (interface to libev, best choice).
781 AnyEvent::Impl::Event based on Event, very stable, few glitches.
782 AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
783
784 Backends that are transparently being picked up when they are used.
785 These will be used when they are currently loaded when the first
786 watcher is created, in which case it is assumed that the application
787 is using them. This means that AnyEvent will automatically pick the
788 right backend when the main program loads an event module before
789 anything starts to create watchers. Nothing special needs to be done
790 by the main program.
791
792 AnyEvent::Impl::Glib based on Glib, slow but very stable.
793 AnyEvent::Impl::Tk based on Tk, very broken.
794 AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
795 AnyEvent::Impl::POE based on POE, very slow, some limitations.
796 AnyEvent::Impl::Irssi used when running within irssi.
797
798 Backends with special needs.
799 Qt requires the Qt::Application to be instantiated first, but will
800 otherwise be picked up automatically. As long as the main program
801 instantiates the application before any AnyEvent watchers are
802 created, everything should just work.
803
804 AnyEvent::Impl::Qt based on Qt.
805
806 Support for IO::Async can only be partial, as it is too broken and
807 architecturally limited to even support the AnyEvent API. It also is
808 the only event loop that needs the loop to be set explicitly, so it
809 can only be used by a main program knowing about AnyEvent. See
810 AnyEvent::Impl::Async for the gory details.
811
812 AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
813
814 Event loops that are indirectly supported via other backends.
815 Some event loops can be supported via other modules:
816
817 There is no direct support for WxWidgets (Wx) or Prima.
818
819 WxWidgets has no support for watching file handles. However, you can
820 use WxWidgets through the POE adaptor, as POE has a Wx backend that
821 simply polls 20 times per second, which was considered to be too
822 horrible to even consider for AnyEvent.
823
824 Prima is not supported as nobody seems to be using it, but it has a
825 POE backend, so it can be supported through POE.
826
827 AnyEvent knows about both Prima and Wx, however, and will try to
828 load POE when detecting them, in the hope that POE will pick them
829 up, in which case everything will be automatic.
684 830
685GLOBAL VARIABLES AND FUNCTIONS 831GLOBAL VARIABLES AND FUNCTIONS
832 These are not normally required to use AnyEvent, but can be useful to
833 write AnyEvent extension modules.
834
686 $AnyEvent::MODEL 835 $AnyEvent::MODEL
687 Contains "undef" until the first watcher is being created. Then it 836 Contains "undef" until the first watcher is being created, before
837 the backend has been autodetected.
838
688 contains the event model that is being used, which is the name of 839 Afterwards it contains the event model that is being used, which is
689 the Perl class implementing the model. This class is usually one of 840 the name of the Perl class implementing the model. This class is
690 the "AnyEvent::Impl:xxx" modules, but can be any other class in the 841 usually one of the "AnyEvent::Impl:xxx" modules, but can be any
691 case AnyEvent has been extended at runtime (e.g. in *rxvt-unicode*). 842 other class in the case AnyEvent has been extended at runtime (e.g.
692 843 in *rxvt-unicode* it will be "urxvt::anyevent").
693 The known classes so far are:
694
695 AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
696 AnyEvent::Impl::Event based on Event, second best choice.
697 AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
698 AnyEvent::Impl::Glib based on Glib, third-best choice.
699 AnyEvent::Impl::Tk based on Tk, very bad choice.
700 AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
701 AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
702 AnyEvent::Impl::POE based on POE, not generic enough for full support.
703
704 # warning, support for IO::Async is only partial, as it is too broken
705 # and limited toe ven support the AnyEvent API. See AnyEvent::Impl::Async.
706 AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed (see its docs).
707
708 There is no support for WxWidgets, as WxWidgets has no support for
709 watching file handles. However, you can use WxWidgets through the
710 POE Adaptor, as POE has a Wx backend that simply polls 20 times per
711 second, which was considered to be too horrible to even consider for
712 AnyEvent. Likewise, other POE backends can be used by AnyEvent by
713 using it's adaptor.
714
715 AnyEvent knows about Prima and Wx and will try to use POE when
716 autodetecting them.
717 844
718 AnyEvent::detect 845 AnyEvent::detect
719 Returns $AnyEvent::MODEL, forcing autodetection of the event model 846 Returns $AnyEvent::MODEL, forcing autodetection of the event model
720 if necessary. You should only call this function right before you 847 if necessary. You should only call this function right before you
721 would have created an AnyEvent watcher anyway, that is, as late as 848 would have created an AnyEvent watcher anyway, that is, as late as
722 possible at runtime. 849 possible at runtime, and not e.g. while initialising of your module.
850
851 If you need to do some initialisation before AnyEvent watchers are
852 created, use "post_detect".
723 853
724 $guard = AnyEvent::post_detect { BLOCK } 854 $guard = AnyEvent::post_detect { BLOCK }
725 Arranges for the code block to be executed as soon as the event 855 Arranges for the code block to be executed as soon as the event
726 model is autodetected (or immediately if this has already happened). 856 model is autodetected (or immediately if this has already happened).
727 857
858 The block will be executed *after* the actual backend has been
859 detected ($AnyEvent::MODEL is set), but *before* any watchers have
860 been created, so it is possible to e.g. patch @AnyEvent::ISA or do
861 other initialisations - see the sources of AnyEvent::Strict or
862 AnyEvent::AIO to see how this is used.
863
864 The most common usage is to create some global watchers, without
865 forcing event module detection too early, for example, AnyEvent::AIO
866 creates and installs the global IO::AIO watcher in a "post_detect"
867 block to avoid autodetecting the event module at load time.
868
728 If called in scalar or list context, then it creates and returns an 869 If called in scalar or list context, then it creates and returns an
729 object that automatically removes the callback again when it is 870 object that automatically removes the callback again when it is
871 destroyed (or "undef" when the hook was immediately executed). See
730 destroyed. See Coro::BDB for a case where this is useful. 872 AnyEvent::AIO for a case where this is useful.
873
874 Example: Create a watcher for the IO::AIO module and store it in
875 $WATCHER. Only do so after the event loop is initialised, though.
876
877 our WATCHER;
878
879 my $guard = AnyEvent::post_detect {
880 $WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
881 };
882
883 # the ||= is important in case post_detect immediately runs the block,
884 # as to not clobber the newly-created watcher. assigning both watcher and
885 # post_detect guard to the same variable has the advantage of users being
886 # able to just C<undef $WATCHER> if the watcher causes them grief.
887
888 $WATCHER ||= $guard;
731 889
732 @AnyEvent::post_detect 890 @AnyEvent::post_detect
733 If there are any code references in this array (you can "push" to it 891 If there are any code references in this array (you can "push" to it
734 before or after loading AnyEvent), then they will called directly 892 before or after loading AnyEvent), then they will called directly
735 after the event loop has been chosen. 893 after the event loop has been chosen.
736 894
737 You should check $AnyEvent::MODEL before adding to this array, 895 You should check $AnyEvent::MODEL before adding to this array,
738 though: if it contains a true value then the event loop has already 896 though: if it is defined then the event loop has already been
739 been detected, and the array will be ignored. 897 detected, and the array will be ignored.
740 898
741 Best use "AnyEvent::post_detect { BLOCK }" instead. 899 Best use "AnyEvent::post_detect { BLOCK }" when your application
900 allows it,as it takes care of these details.
901
902 This variable is mainly useful for modules that can do something
903 useful when AnyEvent is used and thus want to know when it is
904 initialised, but do not need to even load it by default. This array
905 provides the means to hook into AnyEvent passively, without loading
906 it.
742 907
743WHAT TO DO IN A MODULE 908WHAT TO DO IN A MODULE
744 As a module author, you should "use AnyEvent" and call AnyEvent methods 909 As a module author, you should "use AnyEvent" and call AnyEvent methods
745 freely, but you should not load a specific event module or rely on it. 910 freely, but you should not load a specific event module or rely on it.
746 911
… …
797 variable somewhere, waiting for it, and sending it when the program 962 variable somewhere, waiting for it, and sending it when the program
798 should exit cleanly. 963 should exit cleanly.
799 964
800OTHER MODULES 965OTHER MODULES
801 The following is a non-exhaustive list of additional modules that use 966 The following is a non-exhaustive list of additional modules that use
802 AnyEvent and can therefore be mixed easily with other AnyEvent modules 967 AnyEvent as a client and can therefore be mixed easily with other
803 in the same program. Some of the modules come with AnyEvent, some are 968 AnyEvent modules and other event loops in the same program. Some of the
804 available via CPAN. 969 modules come with AnyEvent, most are available via CPAN.
805 970
806 AnyEvent::Util 971 AnyEvent::Util
807 Contains various utility functions that replace often-used but 972 Contains various utility functions that replace often-used but
808 blocking functions such as "inet_aton" by event-/callback-based 973 blocking functions such as "inet_aton" by event-/callback-based
809 versions. 974 versions.
… …
815 more. 980 more.
816 981
817 AnyEvent::Handle 982 AnyEvent::Handle
818 Provide read and write buffers, manages watchers for reads and 983 Provide read and write buffers, manages watchers for reads and
819 writes, supports raw and formatted I/O, I/O queued and fully 984 writes, supports raw and formatted I/O, I/O queued and fully
820 transparent and non-blocking SSL/TLS. 985 transparent and non-blocking SSL/TLS (via AnyEvent::TLS.
821 986
822 AnyEvent::DNS 987 AnyEvent::DNS
823 Provides rich asynchronous DNS resolver capabilities. 988 Provides rich asynchronous DNS resolver capabilities.
824 989
825 AnyEvent::HTTP 990 AnyEvent::HTTP
… …
846 1011
847 AnyEvent::GPSD 1012 AnyEvent::GPSD
848 A non-blocking interface to gpsd, a daemon delivering GPS 1013 A non-blocking interface to gpsd, a daemon delivering GPS
849 information. 1014 information.
850 1015
1016 AnyEvent::IRC
1017 AnyEvent based IRC client module family (replacing the older
1018 Net::IRC3).
1019
1020 AnyEvent::XMPP
1021 AnyEvent based XMPP (Jabber protocol) module family (replacing the
1022 older Net::XMPP2>.
1023
851 AnyEvent::IGS 1024 AnyEvent::IGS
852 A non-blocking interface to the Internet Go Server protocol (used by 1025 A non-blocking interface to the Internet Go Server protocol (used by
853 App::IGS). 1026 App::IGS).
854 1027
855 AnyEvent::IRC
856 AnyEvent based IRC client module family (replacing the older
857 Net::IRC3).
858
859 Net::XMPP2
860 AnyEvent based XMPP (Jabber protocol) module family.
861
862 Net::FCP 1028 Net::FCP
863 AnyEvent-based implementation of the Freenet Client Protocol, 1029 AnyEvent-based implementation of the Freenet Client Protocol,
864 birthplace of AnyEvent. 1030 birthplace of AnyEvent.
865 1031
866 Event::ExecFlow 1032 Event::ExecFlow
867 High level API for event-based execution flow control. 1033 High level API for event-based execution flow control.
868 1034
869 Coro 1035 Coro
870 Has special support for AnyEvent via Coro::AnyEvent. 1036 Has special support for AnyEvent via Coro::AnyEvent.
871
872 IO::Lambda
873 The lambda approach to I/O - don't ask, look there. Can use
874 AnyEvent.
875 1037
876ERROR AND EXCEPTION HANDLING 1038ERROR AND EXCEPTION HANDLING
877 In general, AnyEvent does not do any error handling - it relies on the 1039 In general, AnyEvent does not do any error handling - it relies on the
878 caller to do that if required. The AnyEvent::Strict module (see also the 1040 caller to do that if required. The AnyEvent::Strict module (see also the
879 "PERL_ANYEVENT_STRICT" environment variable, below) provides strict 1041 "PERL_ANYEVENT_STRICT" environment variable, below) provides strict
… …
907 by "PERL_ANYEVENT_MODEL". 1069 by "PERL_ANYEVENT_MODEL".
908 1070
909 When set to 2 or higher, cause AnyEvent to report to STDERR which 1071 When set to 2 or higher, cause AnyEvent to report to STDERR which
910 event model it chooses. 1072 event model it chooses.
911 1073
1074 When set to 8 or higher, then AnyEvent will report extra information
1075 on which optional modules it loads and how it implements certain
1076 features.
1077
912 "PERL_ANYEVENT_STRICT" 1078 "PERL_ANYEVENT_STRICT"
913 AnyEvent does not do much argument checking by default, as thorough 1079 AnyEvent does not do much argument checking by default, as thorough
914 argument checking is very costly. Setting this variable to a true 1080 argument checking is very costly. Setting this variable to a true
915 value will cause AnyEvent to load "AnyEvent::Strict" and then to 1081 value will cause AnyEvent to load "AnyEvent::Strict" and then to
916 thoroughly check the arguments passed to most method calls. If it 1082 thoroughly check the arguments passed to most method calls. If it
917 finds any problems, it will croak. 1083 finds any problems, it will croak.
918 1084
919 In other words, enables "strict" mode. 1085 In other words, enables "strict" mode.
920 1086
921 Unlike "use strict", it is definitely recommended to keep it off in 1087 Unlike "use strict" (or it's modern cousin, "use common::sense", it
922 production. Keeping "PERL_ANYEVENT_STRICT=1" in your environment 1088 is definitely recommended to keep it off in production. Keeping
1089 "PERL_ANYEVENT_STRICT=1" in your environment while developing
923 while developing programs can be very useful, however. 1090 programs can be very useful, however.
924 1091
925 "PERL_ANYEVENT_MODEL" 1092 "PERL_ANYEVENT_MODEL"
926 This can be used to specify the event model to be used by AnyEvent, 1093 This can be used to specify the event model to be used by AnyEvent,
927 before auto detection and -probing kicks in. It must be a string 1094 before auto detection and -probing kicks in. It must be a string
928 consisting entirely of ASCII letters. The string "AnyEvent::Impl::" 1095 consisting entirely of ASCII letters. The string "AnyEvent::Impl::"
… …
969 EDNS0 in its DNS requests. 1136 EDNS0 in its DNS requests.
970 1137
971 "PERL_ANYEVENT_MAX_FORKS" 1138 "PERL_ANYEVENT_MAX_FORKS"
972 The maximum number of child processes that 1139 The maximum number of child processes that
973 "AnyEvent::Util::fork_call" will create in parallel. 1140 "AnyEvent::Util::fork_call" will create in parallel.
1141
1142 "PERL_ANYEVENT_MAX_OUTSTANDING_DNS"
1143 The default value for the "max_outstanding" parameter for the
1144 default DNS resolver - this is the maximum number of parallel DNS
1145 requests that are sent to the DNS server.
1146
1147 "PERL_ANYEVENT_RESOLV_CONF"
1148 The file to use instead of /etc/resolv.conf (or OS-specific
1149 configuration) in the default resolver. When set to the empty
1150 string, no default config will be used.
1151
1152 "PERL_ANYEVENT_CA_FILE", "PERL_ANYEVENT_CA_PATH".
1153 When neither "ca_file" nor "ca_path" was specified during
1154 AnyEvent::TLS context creation, and either of these environment
1155 variables exist, they will be used to specify CA certificate
1156 locations instead of a system-dependent default.
1157
1158 "PERL_ANYEVENT_AVOID_GUARD" and "PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT"
1159 When these are set to 1, then the respective modules are not loaded.
1160 Mostly good for testing AnyEvent itself.
974 1161
975SUPPLYING YOUR OWN EVENT MODEL INTERFACE 1162SUPPLYING YOUR OWN EVENT MODEL INTERFACE
976 This is an advanced topic that you do not normally need to use AnyEvent 1163 This is an advanced topic that you do not normally need to use AnyEvent
977 in a module. This section is only of use to event loop authors who want 1164 in a module. This section is only of use to event loop authors who want
978 to provide AnyEvent compatibility. 1165 to provide AnyEvent compatibility.
… …
1483 SIGCHLD 1670 SIGCHLD
1484 A handler for "SIGCHLD" is installed by AnyEvent's child watcher 1671 A handler for "SIGCHLD" is installed by AnyEvent's child watcher
1485 emulation for event loops that do not support them natively. Also, 1672 emulation for event loops that do not support them natively. Also,
1486 some event loops install a similar handler. 1673 some event loops install a similar handler.
1487 1674
1488 If, when AnyEvent is loaded, SIGCHLD is set to IGNORE, then AnyEvent 1675 Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE,
1489 will reset it to default, to avoid losing child exit statuses. 1676 then AnyEvent will reset it to default, to avoid losing child exit
1677 statuses.
1490 1678
1491 SIGPIPE 1679 SIGPIPE
1492 A no-op handler is installed for "SIGPIPE" when $SIG{PIPE} is 1680 A no-op handler is installed for "SIGPIPE" when $SIG{PIPE} is
1493 "undef" when AnyEvent gets loaded. 1681 "undef" when AnyEvent gets loaded.
1494 1682
… …
1502 it is that this way, the handler will be restored to defaults on 1690 it is that this way, the handler will be restored to defaults on
1503 exec. 1691 exec.
1504 1692
1505 Feel free to install your own handler, or reset it to defaults. 1693 Feel free to install your own handler, or reset it to defaults.
1506 1694
1695RECOMMENDED/OPTIONAL MODULES
1696 One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
1697 it's built-in modules) are required to use it.
1698
1699 That does not mean that AnyEvent won't take advantage of some additional
1700 modules if they are installed.
1701
1702 This section epxlains which additional modules will be used, and how
1703 they affect AnyEvent's operetion.
1704
1705 Async::Interrupt
1706 This slightly arcane module is used to implement fast signal
1707 handling: To my knowledge, there is no way to do completely
1708 race-free and quick signal handling in pure perl. To ensure that
1709 signals still get delivered, AnyEvent will start an interval timer
1710 to wake up perl (and catch the signals) with some delay (default is
1711 10 seconds, look for $AnyEvent::MAX_SIGNAL_LATENCY).
1712
1713 If this module is available, then it will be used to implement
1714 signal catching, which means that signals will not be delayed, and
1715 the event loop will not be interrupted regularly, which is more
1716 efficient (And good for battery life on laptops).
1717
1718 This affects not just the pure-perl event loop, but also other event
1719 loops that have no signal handling on their own (e.g. Glib, Tk, Qt).
1720
1721 Some event loops (POE, Event, Event::Lib) offer signal watchers
1722 natively, and either employ their own workarounds (POE) or use
1723 AnyEvent's workaround (using $AnyEvent::MAX_SIGNAL_LATENCY).
1724 Installing Async::Interrupt does nothing for those backends.
1725
1726 EV This module isn't really "optional", as it is simply one of the
1727 backend event loops that AnyEvent can use. However, it is simply the
1728 best event loop available in terms of features, speed and stability:
1729 It supports the AnyEvent API optimally, implements all the watcher
1730 types in XS, does automatic timer adjustments even when no monotonic
1731 clock is available, can take avdantage of advanced kernel interfaces
1732 such as "epoll" and "kqueue", and is the fastest backend *by far*.
1733 You can even embed Glib/Gtk2 in it (or vice versa, see EV::Glib and
1734 Glib::EV).
1735
1736 Guard
1737 The guard module, when used, will be used to implement
1738 "AnyEvent::Util::guard". This speeds up guards considerably (and
1739 uses a lot less memory), but otherwise doesn't affect guard
1740 operation much. It is purely used for performance.
1741
1742 JSON and JSON::XS
1743 This module is required when you want to read or write JSON data via
1744 AnyEvent::Handle. It is also written in pure-perl, but can take
1745 advantage of the ultra-high-speed JSON::XS module when it is
1746 installed.
1747
1748 In fact, AnyEvent::Handle will use JSON::XS by default if it is
1749 installed.
1750
1751 Net::SSLeay
1752 Implementing TLS/SSL in Perl is certainly interesting, but not very
1753 worthwhile: If this module is installed, then AnyEvent::Handle (with
1754 the help of AnyEvent::TLS), gains the ability to do TLS/SSL.
1755
1756 Time::HiRes
1757 This module is part of perl since release 5.008. It will be used
1758 when the chosen event library does not come with a timing source on
1759 it's own. The pure-perl event loop (AnyEvent::Impl::Perl) will
1760 additionally use it to try to use a monotonic clock for timing
1761 stability.
1762
1507FORK 1763FORK
1508 Most event libraries are not fork-safe. The ones who are usually are 1764 Most event libraries are not fork-safe. The ones who are usually are
1509 because they rely on inefficient but fork-safe "select" or "poll" calls. 1765 because they rely on inefficient but fork-safe "select" or "poll" calls.
1510 Only EV is fully fork-aware. 1766 Only EV is fully fork-aware.
1511 1767
1512 If you have to fork, you must either do so *before* creating your first 1768 If you have to fork, you must either do so *before* creating your first
1513 watcher OR you must not use AnyEvent at all in the child. 1769 watcher OR you must not use AnyEvent at all in the child OR you must do
1770 something completely out of the scope of AnyEvent.
1514 1771
1515SECURITY CONSIDERATIONS 1772SECURITY CONSIDERATIONS
1516 AnyEvent can be forced to load any event model via 1773 AnyEvent can be forced to load any event model via
1517 $ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used 1774 $ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used
1518 to execute arbitrary code or directly gain access, it can easily be used 1775 to execute arbitrary code or directly gain access, it can easily be used
… …
1549 Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk, 1806 Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk,
1550 Event::Lib, Qt, POE. 1807 Event::Lib, Qt, POE.
1551 1808
1552 Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event, 1809 Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,
1553 AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl, 1810 AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,
1554 AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE. 1811 AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE,
1812 AnyEvent::Impl::IOAsync, Anyevent::Impl::Irssi.
1555 1813
1556 Non-blocking file handles, sockets, TCP clients and servers: 1814 Non-blocking file handles, sockets, TCP clients and servers:
1557 AnyEvent::Handle, AnyEvent::Socket. 1815 AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS.
1558 1816
1559 Asynchronous DNS: AnyEvent::DNS. 1817 Asynchronous DNS: AnyEvent::DNS.
1560 1818
1561 Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event, 1819 Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,
1562 1820
1563 Nontrivial usage examples: Net::FCP, Net::XMPP2, AnyEvent::DNS. 1821 Nontrivial usage examples: AnyEvent::GPSD, AnyEvent::XMPP,
1822 AnyEvent::HTTP.
1564 1823
1565AUTHOR 1824AUTHOR
1566 Marc Lehmann <schmorp@schmorp.de> 1825 Marc Lehmann <schmorp@schmorp.de>
1567 http://home.schmorp.de/ 1826 http://home.schmorp.de/
1568 1827

Diff Legend

– Removed lines
+ Added lines
< Changed lines
> Changed lines