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1NAME 1NAME
2 AnyEvent - provide framework for multiple event loops 2 AnyEvent - events independent of event loop implementation
3 3
4 EV, Event, Glib, Tk, Perl, Event::Lib, Qt and POE are various supported 4 EV, Event, Glib, Tk, Perl, Event::Lib, Qt and POE are various supported
5 event loops. 5 event loops.
6 6
7SYNOPSIS 7SYNOPSIS
… …
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 Respository, 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
… …
169 176
170 I/O WATCHERS 177 I/O WATCHERS
171 You can create an I/O watcher by calling the "AnyEvent->io" method with 178 You can create an I/O watcher by calling the "AnyEvent->io" method with
172 the following mandatory key-value pairs as arguments: 179 the following mandatory key-value pairs as arguments:
173 180
174 "fh" is the Perl *file handle* (*not* file descriptor) to watch for 181 "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 182 events (AnyEvent might or might not keep a reference to this file
176 handle). Note that only file handles pointing to things for which 183 handle). Note that only file handles pointing to things for which
177 non-blocking operation makes sense are allowed. This includes sockets, 184 non-blocking operation makes sense are allowed. This includes sockets,
178 most character devices, pipes, fifos and so on, but not for example 185 most character devices, pipes, fifos and so on, but not for example
179 files or block devices. 186 files or block devices.
… …
350 invocation, and callback invocation will be synchronous. Synchronous 357 invocation, and callback invocation will be synchronous. Synchronous
351 means that it might take a while until the signal gets handled by the 358 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. 359 process, but it is guaranteed not to interrupt any other callbacks.
353 360
354 The main advantage of using these watchers is that you can share a 361 The main advantage of using these watchers is that you can share a
355 signal between multiple watchers. 362 signal between multiple watchers, and AnyEvent will ensure that signals
363 will not interrupt your program at bad times.
356 364
357 This watcher might use %SIG, so programs overwriting those signals 365 This watcher might use %SIG (depending on the event loop used), so
358 directly will likely not work correctly. 366 programs overwriting those signals directly will likely not work
367 correctly.
359 368
360 Example: exit on SIGINT 369 Example: exit on SIGINT
361 370
362 my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 }); 371 my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
372
373 Signal Races, Delays and Workarounds
374 Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
375 callbacks to signals in a generic way, which is a pity, as you cannot do
376 race-free signal handling in perl. AnyEvent will try to do it's best,
377 but in some cases, signals will be delayed. The maximum time a signal
378 might be delayed is specified in $AnyEvent::MAX_SIGNAL_LATENCY (default:
379 10 seconds). This variable can be changed only before the first signal
380 watcher is created, and should be left alone otherwise. Higher values
381 will cause fewer spurious wake-ups, which is better for power and CPU
382 saving. All these problems can be avoided by installing the optional
383 Async::Interrupt module. This will not work with inherently broken event
384 loops such as Event or Event::Lib (and not with POE currently, as POE
385 does it's own workaround with one-second latency). With those, you just
386 have to suffer the delays.
363 387
364 CHILD PROCESS WATCHERS 388 CHILD PROCESS WATCHERS
365 You can also watch on a child process exit and catch its exit status. 389 You can also watch on a child process exit and catch its exit status.
366 390
367 The child process is specified by the "pid" argument (if set to 0, it 391 The child process is specified by the "pid" argument (if set to 0, it
… …
390 of when you start the watcher. 414 of when you start the watcher.
391 415
392 This means you cannot create a child watcher as the very first thing in 416 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 417 an AnyEvent program, you *have* to create at least one watcher before
394 you "fork" the child (alternatively, you can call "AnyEvent::detect"). 418 you "fork" the child (alternatively, you can call "AnyEvent::detect").
419
420 As most event loops do not support waiting for child events, they will
421 be emulated by AnyEvent in most cases, in which the latency and race
422 problems mentioned in the description of signal watchers apply.
395 423
396 Example: fork a process and wait for it 424 Example: fork a process and wait for it
397 425
398 my $done = AnyEvent->condvar; 426 my $done = AnyEvent->condvar;
399 427
… …
448 CONDITION VARIABLES 476 CONDITION VARIABLES
449 If you are familiar with some event loops you will know that all of them 477 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 478 require you to run some blocking "loop", "run" or similar function that
451 will actively watch for new events and call your callbacks. 479 will actively watch for new events and call your callbacks.
452 480
453 AnyEvent is different, it expects somebody else to run the event loop 481 AnyEvent is slightly different: it expects somebody else to run the
454 and will only block when necessary (usually when told by the user). 482 event loop and will only block when necessary (usually when told by the
483 user).
455 484
456 The instrument to do that is called a "condition variable", so called 485 The instrument to do that is called a "condition variable", so called
457 because they represent a condition that must become true. 486 because they represent a condition that must become true.
458 487
488 Now is probably a good time to look at the examples further below.
489
459 Condition variables can be created by calling the "AnyEvent->condvar" 490 Condition variables can be created by calling the "AnyEvent->condvar"
460 method, usually without arguments. The only argument pair allowed is 491 method, usually without arguments. The only argument pair allowed is
461
462 "cb", which specifies a callback to be called when the condition 492 "cb", which specifies a callback to be called when the condition
463 variable becomes true, with the condition variable as the first argument 493 variable becomes true, with the condition variable as the first argument
464 (but not the results). 494 (but not the results).
465 495
466 After creation, the condition variable is "false" until it becomes 496 After creation, the condition variable is "false" until it becomes
… …
471 Condition variables are similar to callbacks, except that you can 501 Condition variables are similar to callbacks, except that you can
472 optionally wait for them. They can also be called merge points - points 502 optionally wait for them. They can also be called merge points - points
473 in time where multiple outstanding events have been processed. And yet 503 in time where multiple outstanding events have been processed. And yet
474 another way to call them is transactions - each condition variable can 504 another way to call them is transactions - each condition variable can
475 be used to represent a transaction, which finishes at some point and 505 be used to represent a transaction, which finishes at some point and
476 delivers a result. 506 delivers a result. And yet some people know them as "futures" - a
507 promise to compute/deliver something that you can wait for.
477 508
478 Condition variables are very useful to signal that something has 509 Condition variables are very useful to signal that something has
479 finished, for example, if you write a module that does asynchronous http 510 finished, for example, if you write a module that does asynchronous http
480 requests, then a condition variable would be the ideal candidate to 511 requests, then a condition variable would be the ideal candidate to
481 signal the availability of results. The user can either act when the 512 signal the availability of results. The user can either act when the
… …
515 after => 1, 546 after => 1,
516 cb => sub { $result_ready->send }, 547 cb => sub { $result_ready->send },
517 ); 548 );
518 549
519 # this "blocks" (while handling events) till the callback 550 # this "blocks" (while handling events) till the callback
520 # calls send 551 # calls -<send
521 $result_ready->recv; 552 $result_ready->recv;
522 553
523 Example: wait for a timer, but take advantage of the fact that condition 554 Example: wait for a timer, but take advantage of the fact that condition
524 variables are also code references. 555 variables are also callable directly.
525 556
526 my $done = AnyEvent->condvar; 557 my $done = AnyEvent->condvar;
527 my $delay = AnyEvent->timer (after => 5, cb => $done); 558 my $delay = AnyEvent->timer (after => 5, cb => $done);
528 $done->recv; 559 $done->recv;
529 560
… …
535 566
536 ... 567 ...
537 568
538 my @info = $couchdb->info->recv; 569 my @info = $couchdb->info->recv;
539 570
540 And this is how you would just ste a callback to be called whenever the 571 And this is how you would just set a callback to be called whenever the
541 results are available: 572 results are available:
542 573
543 $couchdb->info->cb (sub { 574 $couchdb->info->cb (sub {
544 my @info = $_[0]->recv; 575 my @info = $_[0]->recv;
545 }); 576 });
… …
560 591
561 Any arguments passed to the "send" call will be returned by all 592 Any arguments passed to the "send" call will be returned by all
562 future "->recv" calls. 593 future "->recv" calls.
563 594
564 Condition variables are overloaded so one can call them directly (as 595 Condition variables are overloaded so one can call them directly (as
565 a code reference). Calling them directly is the same as calling 596 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 597 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).
572 598
573 $cv->croak ($error) 599 $cv->croak ($error)
574 Similar to send, but causes all call's to "->recv" to invoke 600 Similar to send, but causes all call's to "->recv" to invoke
575 "Carp::croak" with the given error message/object/scalar. 601 "Carp::croak" with the given error message/object/scalar.
576 602
577 This can be used to signal any errors to the condition variable 603 This can be used to signal any errors to the condition variable
578 user/consumer. 604 user/consumer. Doing it this way instead of calling "croak" directly
605 delays the error detetcion, but has the overwhelmign advantage that
606 it diagnoses the error at the place where the result is expected,
607 and not deep in some event clalback without connection to the actual
608 code causing the problem.
579 609
580 $cv->begin ([group callback]) 610 $cv->begin ([group callback])
581 $cv->end 611 $cv->end
582 These two methods are EXPERIMENTAL and MIGHT CHANGE.
583
584 These two methods can be used to combine many transactions/events 612 These two methods can be used to combine many transactions/events
585 into one. For example, a function that pings many hosts in parallel 613 into one. For example, a function that pings many hosts in parallel
586 might want to use a condition variable for the whole process. 614 might want to use a condition variable for the whole process.
587 615
588 Every call to "->begin" will increment a counter, and every call to 616 Every call to "->begin" will increment a counter, and every call to
589 "->end" will decrement it. If the counter reaches 0 in "->end", the 617 "->end" will decrement it. If the counter reaches 0 in "->end", the
590 (last) callback passed to "begin" will be executed. That callback is 618 (last) callback passed to "begin" will be executed. That callback is
591 *supposed* to call "->send", but that is not required. If no 619 *supposed* to call "->send", but that is not required. If no
592 callback was set, "send" will be called without any arguments. 620 callback was set, "send" will be called without any arguments.
593 621
594 Let's clarify this with the ping example: 622 You can think of "$cv->send" giving you an OR condition (one call
623 sends), while "$cv->begin" and "$cv->end" giving you an AND
624 condition (all "begin" calls must be "end"'ed before the condvar
625 sends).
626
627 Let's start with a simple example: you have two I/O watchers (for
628 example, STDOUT and STDERR for a program), and you want to wait for
629 both streams to close before activating a condvar:
630
631 my $cv = AnyEvent->condvar;
632
633 $cv->begin; # first watcher
634 my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
635 defined sysread $fh1, my $buf, 4096
636 or $cv->end;
637 });
638
639 $cv->begin; # second watcher
640 my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
641 defined sysread $fh2, my $buf, 4096
642 or $cv->end;
643 });
644
645 $cv->recv;
646
647 This works because for every event source (EOF on file handle),
648 there is one call to "begin", so the condvar waits for all calls to
649 "end" before sending.
650
651 The ping example mentioned above is slightly more complicated, as
652 the there are results to be passwd back, and the number of tasks
653 that are begung can potentially be zero:
595 654
596 my $cv = AnyEvent->condvar; 655 my $cv = AnyEvent->condvar;
597 656
598 my %result; 657 my %result;
599 $cv->begin (sub { $cv->send (\%result) }); 658 $cv->begin (sub { $cv->send (\%result) });
… …
619 the loop, which serves two important purposes: first, it sets the 678 the loop, which serves two important purposes: first, it sets the
620 callback to be called once the counter reaches 0, and second, it 679 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 680 ensures that "send" is called even when "no" hosts are being pinged
622 (the loop doesn't execute once). 681 (the loop doesn't execute once).
623 682
624 This is the general pattern when you "fan out" into multiple 683 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 684 potentially none) subrequests: use an outer "begin"/"end" pair to
626 ensure "end" is called at least once, and then, for each subrequest 685 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 686 for each subrequest you start, call "begin" and for each subrequest
628 "end". 687 you finish, call "end".
629 688
630 METHODS FOR CONSUMERS 689 METHODS FOR CONSUMERS
631 These methods should only be used by the consuming side, i.e. the code 690 These methods should only be used by the consuming side, i.e. the code
632 awaits the condition. 691 awaits the condition.
633 692
… …
642 function will call "croak". 701 function will call "croak".
643 702
644 In list context, all parameters passed to "send" will be returned, 703 In list context, all parameters passed to "send" will be returned,
645 in scalar context only the first one will be returned. 704 in scalar context only the first one will be returned.
646 705
706 Note that doing a blocking wait in a callback is not supported by
707 any event loop, that is, recursive invocation of a blocking "->recv"
708 is not allowed, and the "recv" call will "croak" if such a condition
709 is detected. This condition can be slightly loosened by using
710 Coro::AnyEvent, which allows you to do a blocking "->recv" from any
711 thread that doesn't run the event loop itself.
712
647 Not all event models support a blocking wait - some die in that case 713 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 714 (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 715 using this from a module, never require a blocking wait*. Instead,
650 the caller decide whether the call will block or not (for example, 716 let the caller decide whether the call will block or not (for
651 by coupling condition variables with some kind of request results 717 example, by coupling condition variables with some kind of request
652 and supporting callbacks so the caller knows that getting the result 718 results and supporting callbacks so the caller knows that getting
653 will not block, while still supporting blocking waits if the caller 719 the result will not block, while still supporting blocking waits if
654 so desires). 720 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).
666 721
667 You can ensure that "-recv" never blocks by setting a callback and 722 You can ensure that "-recv" never blocks by setting a callback and
668 only calling "->recv" from within that callback (or at a later 723 only calling "->recv" from within that callback (or at a later
669 time). This will work even when the event loop does not support 724 time). This will work even when the event loop does not support
670 blocking waits otherwise. 725 blocking waits otherwise.
… …
680 The callback will be called when the condition becomes "true", i.e. 735 The callback will be called when the condition becomes "true", i.e.
681 when "send" or "croak" are called, with the only argument being the 736 when "send" or "croak" are called, with the only argument being the
682 condition variable itself. Calling "recv" inside the callback or at 737 condition variable itself. Calling "recv" inside the callback or at
683 any later time is guaranteed not to block. 738 any later time is guaranteed not to block.
684 739
740SUPPORTED EVENT LOOPS/BACKENDS
741 The available backend classes are (every class has its own manpage):
742
743 Backends that are autoprobed when no other event loop can be found.
744 EV is the preferred backend when no other event loop seems to be in
745 use. If EV is not installed, then AnyEvent will try Event, and,
746 failing that, will fall back to its own pure-perl implementation,
747 which is available everywhere as it comes with AnyEvent itself.
748
749 AnyEvent::Impl::EV based on EV (interface to libev, best choice).
750 AnyEvent::Impl::Event based on Event, very stable, few glitches.
751 AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
752
753 Backends that are transparently being picked up when they are used.
754 These will be used when they are currently loaded when the first
755 watcher is created, in which case it is assumed that the application
756 is using them. This means that AnyEvent will automatically pick the
757 right backend when the main program loads an event module before
758 anything starts to create watchers. Nothing special needs to be done
759 by the main program.
760
761 AnyEvent::Impl::Glib based on Glib, slow but very stable.
762 AnyEvent::Impl::Tk based on Tk, very broken.
763 AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
764 AnyEvent::Impl::POE based on POE, very slow, some limitations.
765
766 Backends with special needs.
767 Qt requires the Qt::Application to be instantiated first, but will
768 otherwise be picked up automatically. As long as the main program
769 instantiates the application before any AnyEvent watchers are
770 created, everything should just work.
771
772 AnyEvent::Impl::Qt based on Qt.
773
774 Support for IO::Async can only be partial, as it is too broken and
775 architecturally limited to even support the AnyEvent API. It also is
776 the only event loop that needs the loop to be set explicitly, so it
777 can only be used by a main program knowing about AnyEvent. See
778 AnyEvent::Impl::Async for the gory details.
779
780 AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
781
782 Event loops that are indirectly supported via other backends.
783 Some event loops can be supported via other modules:
784
785 There is no direct support for WxWidgets (Wx) or Prima.
786
787 WxWidgets has no support for watching file handles. However, you can
788 use WxWidgets through the POE adaptor, as POE has a Wx backend that
789 simply polls 20 times per second, which was considered to be too
790 horrible to even consider for AnyEvent.
791
792 Prima is not supported as nobody seems to be using it, but it has a
793 POE backend, so it can be supported through POE.
794
795 AnyEvent knows about both Prima and Wx, however, and will try to
796 load POE when detecting them, in the hope that POE will pick them
797 up, in which case everything will be automatic.
798
685GLOBAL VARIABLES AND FUNCTIONS 799GLOBAL VARIABLES AND FUNCTIONS
800 These are not normally required to use AnyEvent, but can be useful to
801 write AnyEvent extension modules.
802
686 $AnyEvent::MODEL 803 $AnyEvent::MODEL
687 Contains "undef" until the first watcher is being created. Then it 804 Contains "undef" until the first watcher is being created, before
805 the backend has been autodetected.
806
688 contains the event model that is being used, which is the name of 807 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 808 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 809 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*). 810 other class in the case AnyEvent has been extended at runtime (e.g.
692 811 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.
717 812
718 AnyEvent::detect 813 AnyEvent::detect
719 Returns $AnyEvent::MODEL, forcing autodetection of the event model 814 Returns $AnyEvent::MODEL, forcing autodetection of the event model
720 if necessary. You should only call this function right before you 815 if necessary. You should only call this function right before you
721 would have created an AnyEvent watcher anyway, that is, as late as 816 would have created an AnyEvent watcher anyway, that is, as late as
722 possible at runtime. 817 possible at runtime, and not e.g. while initialising of your module.
818
819 If you need to do some initialisation before AnyEvent watchers are
820 created, use "post_detect".
723 821
724 $guard = AnyEvent::post_detect { BLOCK } 822 $guard = AnyEvent::post_detect { BLOCK }
725 Arranges for the code block to be executed as soon as the event 823 Arranges for the code block to be executed as soon as the event
726 model is autodetected (or immediately if this has already happened). 824 model is autodetected (or immediately if this has already happened).
825
826 The block will be executed *after* the actual backend has been
827 detected ($AnyEvent::MODEL is set), but *before* any watchers have
828 been created, so it is possible to e.g. patch @AnyEvent::ISA or do
829 other initialisations - see the sources of AnyEvent::Strict or
830 AnyEvent::AIO to see how this is used.
831
832 The most common usage is to create some global watchers, without
833 forcing event module detection too early, for example, AnyEvent::AIO
834 creates and installs the global IO::AIO watcher in a "post_detect"
835 block to avoid autodetecting the event module at load time.
727 836
728 If called in scalar or list context, then it creates and returns an 837 If called in scalar or list context, then it creates and returns an
729 object that automatically removes the callback again when it is 838 object that automatically removes the callback again when it is
730 destroyed. See Coro::BDB for a case where this is useful. 839 destroyed. See Coro::BDB for a case where this is useful.
731 840
… …
733 If there are any code references in this array (you can "push" to it 842 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 843 before or after loading AnyEvent), then they will called directly
735 after the event loop has been chosen. 844 after the event loop has been chosen.
736 845
737 You should check $AnyEvent::MODEL before adding to this array, 846 You should check $AnyEvent::MODEL before adding to this array,
738 though: if it contains a true value then the event loop has already 847 though: if it is defined then the event loop has already been
739 been detected, and the array will be ignored. 848 detected, and the array will be ignored.
740 849
741 Best use "AnyEvent::post_detect { BLOCK }" instead. 850 Best use "AnyEvent::post_detect { BLOCK }" when your application
851 allows it,as it takes care of these details.
852
853 This variable is mainly useful for modules that can do something
854 useful when AnyEvent is used and thus want to know when it is
855 initialised, but do not need to even load it by default. This array
856 provides the means to hook into AnyEvent passively, without loading
857 it.
742 858
743WHAT TO DO IN A MODULE 859WHAT TO DO IN A MODULE
744 As a module author, you should "use AnyEvent" and call AnyEvent methods 860 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. 861 freely, but you should not load a specific event module or rely on it.
746 862
… …
797 variable somewhere, waiting for it, and sending it when the program 913 variable somewhere, waiting for it, and sending it when the program
798 should exit cleanly. 914 should exit cleanly.
799 915
800OTHER MODULES 916OTHER MODULES
801 The following is a non-exhaustive list of additional modules that use 917 The following is a non-exhaustive list of additional modules that use
802 AnyEvent and can therefore be mixed easily with other AnyEvent modules 918 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 919 AnyEvent modules and other event loops in the same program. Some of the
804 available via CPAN. 920 modules come with AnyEvent, most are available via CPAN.
805 921
806 AnyEvent::Util 922 AnyEvent::Util
807 Contains various utility functions that replace often-used but 923 Contains various utility functions that replace often-used but
808 blocking functions such as "inet_aton" by event-/callback-based 924 blocking functions such as "inet_aton" by event-/callback-based
809 versions. 925 versions.
… …
815 more. 931 more.
816 932
817 AnyEvent::Handle 933 AnyEvent::Handle
818 Provide read and write buffers, manages watchers for reads and 934 Provide read and write buffers, manages watchers for reads and
819 writes, supports raw and formatted I/O, I/O queued and fully 935 writes, supports raw and formatted I/O, I/O queued and fully
820 transparent and non-blocking SSL/TLS. 936 transparent and non-blocking SSL/TLS (via AnyEvent::TLS.
821 937
822 AnyEvent::DNS 938 AnyEvent::DNS
823 Provides rich asynchronous DNS resolver capabilities. 939 Provides rich asynchronous DNS resolver capabilities.
824 940
825 AnyEvent::HTTP 941 AnyEvent::HTTP
… …
846 962
847 AnyEvent::GPSD 963 AnyEvent::GPSD
848 A non-blocking interface to gpsd, a daemon delivering GPS 964 A non-blocking interface to gpsd, a daemon delivering GPS
849 information. 965 information.
850 966
967 AnyEvent::IRC
968 AnyEvent based IRC client module family (replacing the older
969 Net::IRC3).
970
971 AnyEvent::XMPP
972 AnyEvent based XMPP (Jabber protocol) module family (replacing the
973 older Net::XMPP2>.
974
851 AnyEvent::IGS 975 AnyEvent::IGS
852 A non-blocking interface to the Internet Go Server protocol (used by 976 A non-blocking interface to the Internet Go Server protocol (used by
853 App::IGS). 977 App::IGS).
854 978
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 979 Net::FCP
863 AnyEvent-based implementation of the Freenet Client Protocol, 980 AnyEvent-based implementation of the Freenet Client Protocol,
864 birthplace of AnyEvent. 981 birthplace of AnyEvent.
865 982
866 Event::ExecFlow 983 Event::ExecFlow
867 High level API for event-based execution flow control. 984 High level API for event-based execution flow control.
868 985
869 Coro 986 Coro
870 Has special support for AnyEvent via Coro::AnyEvent. 987 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.
875 988
876ERROR AND EXCEPTION HANDLING 989ERROR AND EXCEPTION HANDLING
877 In general, AnyEvent does not do any error handling - it relies on the 990 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 991 caller to do that if required. The AnyEvent::Strict module (see also the
879 "PERL_ANYEVENT_STRICT" environment variable, below) provides strict 992 "PERL_ANYEVENT_STRICT" environment variable, below) provides strict
… …
907 by "PERL_ANYEVENT_MODEL". 1020 by "PERL_ANYEVENT_MODEL".
908 1021
909 When set to 2 or higher, cause AnyEvent to report to STDERR which 1022 When set to 2 or higher, cause AnyEvent to report to STDERR which
910 event model it chooses. 1023 event model it chooses.
911 1024
1025 When set to 8 or higher, then AnyEvent will report extra information
1026 on which optional modules it loads and how it implements certain
1027 features.
1028
912 "PERL_ANYEVENT_STRICT" 1029 "PERL_ANYEVENT_STRICT"
913 AnyEvent does not do much argument checking by default, as thorough 1030 AnyEvent does not do much argument checking by default, as thorough
914 argument checking is very costly. Setting this variable to a true 1031 argument checking is very costly. Setting this variable to a true
915 value will cause AnyEvent to load "AnyEvent::Strict" and then to 1032 value will cause AnyEvent to load "AnyEvent::Strict" and then to
916 thoroughly check the arguments passed to most method calls. If it 1033 thoroughly check the arguments passed to most method calls. If it
917 finds any problems, it will croak. 1034 finds any problems, it will croak.
918 1035
919 In other words, enables "strict" mode. 1036 In other words, enables "strict" mode.
920 1037
921 Unlike "use strict", it is definitely recommended to keep it off in 1038 Unlike "use strict" (or it's modern cousin, "use common::sense", it
922 production. Keeping "PERL_ANYEVENT_STRICT=1" in your environment 1039 is definitely recommended to keep it off in production. Keeping
1040 "PERL_ANYEVENT_STRICT=1" in your environment while developing
923 while developing programs can be very useful, however. 1041 programs can be very useful, however.
924 1042
925 "PERL_ANYEVENT_MODEL" 1043 "PERL_ANYEVENT_MODEL"
926 This can be used to specify the event model to be used by AnyEvent, 1044 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 1045 before auto detection and -probing kicks in. It must be a string
928 consisting entirely of ASCII letters. The string "AnyEvent::Impl::" 1046 consisting entirely of ASCII letters. The string "AnyEvent::Impl::"
… …
969 EDNS0 in its DNS requests. 1087 EDNS0 in its DNS requests.
970 1088
971 "PERL_ANYEVENT_MAX_FORKS" 1089 "PERL_ANYEVENT_MAX_FORKS"
972 The maximum number of child processes that 1090 The maximum number of child processes that
973 "AnyEvent::Util::fork_call" will create in parallel. 1091 "AnyEvent::Util::fork_call" will create in parallel.
1092
1093 "PERL_ANYEVENT_MAX_OUTSTANDING_DNS"
1094 The default value for the "max_outstanding" parameter for the
1095 default DNS resolver - this is the maximum number of parallel DNS
1096 requests that are sent to the DNS server.
1097
1098 "PERL_ANYEVENT_RESOLV_CONF"
1099 The file to use instead of /etc/resolv.conf (or OS-specific
1100 configuration) in the default resolver. When set to the empty
1101 string, no default config will be used.
1102
1103 "PERL_ANYEVENT_CA_FILE", "PERL_ANYEVENT_CA_PATH".
1104 When neither "ca_file" nor "ca_path" was specified during
1105 AnyEvent::TLS context creation, and either of these environment
1106 variables exist, they will be used to specify CA certificate
1107 locations instead of a system-dependent default.
1108
1109 "PERL_ANYEVENT_AVOID_GUARD" and "PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT"
1110 When these are set to 1, then the respective modules are not loaded.
1111 Mostly good for testing AnyEvent itself.
974 1112
975SUPPLYING YOUR OWN EVENT MODEL INTERFACE 1113SUPPLYING YOUR OWN EVENT MODEL INTERFACE
976 This is an advanced topic that you do not normally need to use AnyEvent 1114 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 1115 in a module. This section is only of use to event loop authors who want
978 to provide AnyEvent compatibility. 1116 to provide AnyEvent compatibility.
… …
1483 SIGCHLD 1621 SIGCHLD
1484 A handler for "SIGCHLD" is installed by AnyEvent's child watcher 1622 A handler for "SIGCHLD" is installed by AnyEvent's child watcher
1485 emulation for event loops that do not support them natively. Also, 1623 emulation for event loops that do not support them natively. Also,
1486 some event loops install a similar handler. 1624 some event loops install a similar handler.
1487 1625
1488 If, when AnyEvent is loaded, SIGCHLD is set to IGNORE, then AnyEvent 1626 Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE,
1489 will reset it to default, to avoid losing child exit statuses. 1627 then AnyEvent will reset it to default, to avoid losing child exit
1628 statuses.
1490 1629
1491 SIGPIPE 1630 SIGPIPE
1492 A no-op handler is installed for "SIGPIPE" when $SIG{PIPE} is 1631 A no-op handler is installed for "SIGPIPE" when $SIG{PIPE} is
1493 "undef" when AnyEvent gets loaded. 1632 "undef" when AnyEvent gets loaded.
1494 1633
… …
1502 it is that this way, the handler will be restored to defaults on 1641 it is that this way, the handler will be restored to defaults on
1503 exec. 1642 exec.
1504 1643
1505 Feel free to install your own handler, or reset it to defaults. 1644 Feel free to install your own handler, or reset it to defaults.
1506 1645
1646RECOMMENDED/OPTIONAL MODULES
1647 One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
1648 it's built-in modules) are required to use it.
1649
1650 That does not mean that AnyEvent won't take advantage of some additional
1651 modules if they are installed.
1652
1653 This section epxlains which additional modules will be used, and how
1654 they affect AnyEvent's operetion.
1655
1656 Async::Interrupt
1657 This slightly arcane module is used to implement fast signal
1658 handling: To my knowledge, there is no way to do completely
1659 race-free and quick signal handling in pure perl. To ensure that
1660 signals still get delivered, AnyEvent will start an interval timer
1661 to wake up perl (and catch the signals) with some delay (default is
1662 10 seconds, look for $AnyEvent::MAX_SIGNAL_LATENCY).
1663
1664 If this module is available, then it will be used to implement
1665 signal catching, which means that signals will not be delayed, and
1666 the event loop will not be interrupted regularly, which is more
1667 efficient (And good for battery life on laptops).
1668
1669 This affects not just the pure-perl event loop, but also other event
1670 loops that have no signal handling on their own (e.g. Glib, Tk, Qt).
1671
1672 Some event loops (POE, Event, Event::Lib) offer signal watchers
1673 natively, and either employ their own workarounds (POE) or use
1674 AnyEvent's workaround (using $AnyEvent::MAX_SIGNAL_LATENCY).
1675 Installing Async::Interrupt does nothing for those backends.
1676
1677 EV This module isn't really "optional", as it is simply one of the
1678 backend event loops that AnyEvent can use. However, it is simply the
1679 best event loop available in terms of features, speed and stability:
1680 It supports the AnyEvent API optimally, implements all the watcher
1681 types in XS, does automatic timer adjustments even when no monotonic
1682 clock is available, can take avdantage of advanced kernel interfaces
1683 such as "epoll" and "kqueue", and is the fastest backend *by far*.
1684 You can even embed Glib/Gtk2 in it (or vice versa, see EV::Glib and
1685 Glib::EV).
1686
1687 Guard
1688 The guard module, when used, will be used to implement
1689 "AnyEvent::Util::guard". This speeds up guards considerably (and
1690 uses a lot less memory), but otherwise doesn't affect guard
1691 operation much. It is purely used for performance.
1692
1693 JSON and JSON::XS
1694 This module is required when you want to read or write JSON data via
1695 AnyEvent::Handle. It is also written in pure-perl, but can take
1696 advantage of the ultra-high-speed JSON::XS module when it is
1697 installed.
1698
1699 In fact, AnyEvent::Handle will use JSON::XS by default if it is
1700 installed.
1701
1702 Net::SSLeay
1703 Implementing TLS/SSL in Perl is certainly interesting, but not very
1704 worthwhile: If this module is installed, then AnyEvent::Handle (with
1705 the help of AnyEvent::TLS), gains the ability to do TLS/SSL.
1706
1707 Time::HiRes
1708 This module is part of perl since release 5.008. It will be used
1709 when the chosen event library does not come with a timing source on
1710 it's own. The pure-perl event loop (AnyEvent::Impl::Perl) will
1711 additionally use it to try to use a monotonic clock for timing
1712 stability.
1713
1507FORK 1714FORK
1508 Most event libraries are not fork-safe. The ones who are usually are 1715 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. 1716 because they rely on inefficient but fork-safe "select" or "poll" calls.
1510 Only EV is fully fork-aware. 1717 Only EV is fully fork-aware.
1511 1718
1512 If you have to fork, you must either do so *before* creating your first 1719 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. 1720 watcher OR you must not use AnyEvent at all in the child OR you must do
1721 something completely out of the scope of AnyEvent.
1514 1722
1515SECURITY CONSIDERATIONS 1723SECURITY CONSIDERATIONS
1516 AnyEvent can be forced to load any event model via 1724 AnyEvent can be forced to load any event model via
1517 $ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used 1725 $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 1726 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, 1757 Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk,
1550 Event::Lib, Qt, POE. 1758 Event::Lib, Qt, POE.
1551 1759
1552 Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event, 1760 Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,
1553 AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl, 1761 AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,
1554 AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE. 1762 AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE,
1763 AnyEvent::Impl::IOAsync.
1555 1764
1556 Non-blocking file handles, sockets, TCP clients and servers: 1765 Non-blocking file handles, sockets, TCP clients and servers:
1557 AnyEvent::Handle, AnyEvent::Socket. 1766 AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS.
1558 1767
1559 Asynchronous DNS: AnyEvent::DNS. 1768 Asynchronous DNS: AnyEvent::DNS.
1560 1769
1561 Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event, 1770 Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,
1562 1771
1563 Nontrivial usage examples: Net::FCP, Net::XMPP2, AnyEvent::DNS. 1772 Nontrivial usage examples: AnyEvent::GPSD, AnyEvent::XMPP,
1773 AnyEvent::HTTP.
1564 1774
1565AUTHOR 1775AUTHOR
1566 Marc Lehmann <schmorp@schmorp.de> 1776 Marc Lehmann <schmorp@schmorp.de>
1567 http://home.schmorp.de/ 1777 http://home.schmorp.de/
1568 1778

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