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Revision 1.40 by root, Tue Jun 23 23:37:32 2009 UTC vs.
Revision 1.45 by root, Fri Jul 17 14:57:03 2009 UTC

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169 169
170 I/O WATCHERS 170 I/O WATCHERS
171 You can create an I/O watcher by calling the "AnyEvent->io" method with 171 You can create an I/O watcher by calling the "AnyEvent->io" method with
172 the following mandatory key-value pairs as arguments: 172 the following mandatory key-value pairs as arguments:
173 173
174 "fh" is the Perl *file handle* (*not* file descriptor) to watch for 174 "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 175 events (AnyEvent might or might not keep a reference to this file
176 handle). Note that only file handles pointing to things for which 176 handle). Note that only file handles pointing to things for which
177 non-blocking operation makes sense are allowed. This includes sockets, 177 non-blocking operation makes sense are allowed. This includes sockets,
178 most character devices, pipes, fifos and so on, but not for example 178 most character devices, pipes, fifos and so on, but not for example
179 files or block devices. 179 files or block devices.
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380 380
381 There is a slight catch to child watchers, however: you usually start 381 There is a slight catch to child watchers, however: you usually start
382 them *after* the child process was created, and this means the process 382 them *after* the child process was created, and this means the process
383 could have exited already (and no SIGCHLD will be sent anymore). 383 could have exited already (and no SIGCHLD will be sent anymore).
384 384
385 Not all event models handle this correctly (POE doesn't), but even for 385 Not all event models handle this correctly (neither POE nor IO::Async
386 do, see their AnyEvent::Impl manpages for details), but even for event
386 event models that *do* handle this correctly, they usually need to be 387 models that *do* handle this correctly, they usually need to be loaded
387 loaded before the process exits (i.e. before you fork in the first 388 before the process exits (i.e. before you fork in the first place).
388 place). 389 AnyEvent's pure perl event loop handles all cases correctly regardless
390 of when you start the watcher.
389 391
390 This means you cannot create a child watcher as the very first thing in 392 This means you cannot create a child watcher as the very first thing in
391 an AnyEvent program, you *have* to create at least one watcher before 393 an AnyEvent program, you *have* to create at least one watcher before
392 you "fork" the child (alternatively, you can call "AnyEvent::detect"). 394 you "fork" the child (alternatively, you can call "AnyEvent::detect").
393 395
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446 CONDITION VARIABLES 448 CONDITION VARIABLES
447 If you are familiar with some event loops you will know that all of them 449 If you are familiar with some event loops you will know that all of them
448 require you to run some blocking "loop", "run" or similar function that 450 require you to run some blocking "loop", "run" or similar function that
449 will actively watch for new events and call your callbacks. 451 will actively watch for new events and call your callbacks.
450 452
451 AnyEvent is different, it expects somebody else to run the event loop 453 AnyEvent is slightly different: it expects somebody else to run the
452 and will only block when necessary (usually when told by the user). 454 event loop and will only block when necessary (usually when told by the
455 user).
453 456
454 The instrument to do that is called a "condition variable", so called 457 The instrument to do that is called a "condition variable", so called
455 because they represent a condition that must become true. 458 because they represent a condition that must become true.
456 459
460 Now is probably a good time to look at the examples further below.
461
457 Condition variables can be created by calling the "AnyEvent->condvar" 462 Condition variables can be created by calling the "AnyEvent->condvar"
458 method, usually without arguments. The only argument pair allowed is 463 method, usually without arguments. The only argument pair allowed is
459
460 "cb", which specifies a callback to be called when the condition 464 "cb", which specifies a callback to be called when the condition
461 variable becomes true, with the condition variable as the first argument 465 variable becomes true, with the condition variable as the first argument
462 (but not the results). 466 (but not the results).
463 467
464 After creation, the condition variable is "false" until it becomes 468 After creation, the condition variable is "false" until it becomes
… …
513 after => 1, 517 after => 1,
514 cb => sub { $result_ready->send }, 518 cb => sub { $result_ready->send },
515 ); 519 );
516 520
517 # this "blocks" (while handling events) till the callback 521 # this "blocks" (while handling events) till the callback
518 # calls send 522 # calls -<send
519 $result_ready->recv; 523 $result_ready->recv;
520 524
521 Example: wait for a timer, but take advantage of the fact that condition 525 Example: wait for a timer, but take advantage of the fact that condition
522 variables are also code references. 526 variables are also callable directly.
523 527
524 my $done = AnyEvent->condvar; 528 my $done = AnyEvent->condvar;
525 my $delay = AnyEvent->timer (after => 5, cb => $done); 529 my $delay = AnyEvent->timer (after => 5, cb => $done);
526 $done->recv; 530 $done->recv;
527 531
… …
533 537
534 ... 538 ...
535 539
536 my @info = $couchdb->info->recv; 540 my @info = $couchdb->info->recv;
537 541
538 And this is how you would just ste a callback to be called whenever the 542 And this is how you would just set a callback to be called whenever the
539 results are available: 543 results are available:
540 544
541 $couchdb->info->cb (sub { 545 $couchdb->info->cb (sub {
542 my @info = $_[0]->recv; 546 my @info = $_[0]->recv;
543 }); 547 });
… …
558 562
559 Any arguments passed to the "send" call will be returned by all 563 Any arguments passed to the "send" call will be returned by all
560 future "->recv" calls. 564 future "->recv" calls.
561 565
562 Condition variables are overloaded so one can call them directly (as 566 Condition variables are overloaded so one can call them directly (as
563 a code reference). Calling them directly is the same as calling 567 if they were a code reference). Calling them directly is the same as
564 "send". Note, however, that many C-based event loops do not handle 568 calling "send".
565 overloading, so as tempting as it may be, passing a condition
566 variable instead of a callback does not work. Both the pure perl and
567 EV loops support overloading, however, as well as all functions that
568 use perl to invoke a callback (as in AnyEvent::Socket and
569 AnyEvent::DNS for example).
570 569
571 $cv->croak ($error) 570 $cv->croak ($error)
572 Similar to send, but causes all call's to "->recv" to invoke 571 Similar to send, but causes all call's to "->recv" to invoke
573 "Carp::croak" with the given error message/object/scalar. 572 "Carp::croak" with the given error message/object/scalar.
574 573
575 This can be used to signal any errors to the condition variable 574 This can be used to signal any errors to the condition variable
576 user/consumer. 575 user/consumer. Doing it this way instead of calling "croak" directly
576 delays the error detetcion, but has the overwhelmign advantage that
577 it diagnoses the error at the place where the result is expected,
578 and not deep in some event clalback without connection to the actual
579 code causing the problem.
577 580
578 $cv->begin ([group callback]) 581 $cv->begin ([group callback])
579 $cv->end 582 $cv->end
580 These two methods are EXPERIMENTAL and MIGHT CHANGE.
581
582 These two methods can be used to combine many transactions/events 583 These two methods can be used to combine many transactions/events
583 into one. For example, a function that pings many hosts in parallel 584 into one. For example, a function that pings many hosts in parallel
584 might want to use a condition variable for the whole process. 585 might want to use a condition variable for the whole process.
585 586
586 Every call to "->begin" will increment a counter, and every call to 587 Every call to "->begin" will increment a counter, and every call to
587 "->end" will decrement it. If the counter reaches 0 in "->end", the 588 "->end" will decrement it. If the counter reaches 0 in "->end", the
588 (last) callback passed to "begin" will be executed. That callback is 589 (last) callback passed to "begin" will be executed. That callback is
589 *supposed* to call "->send", but that is not required. If no 590 *supposed* to call "->send", but that is not required. If no
590 callback was set, "send" will be called without any arguments. 591 callback was set, "send" will be called without any arguments.
591 592
592 Let's clarify this with the ping example: 593 You can think of "$cv->send" giving you an OR condition (one call
594 sends), while "$cv->begin" and "$cv->end" giving you an AND
595 condition (all "begin" calls must be "end"'ed before the condvar
596 sends).
597
598 Let's start with a simple example: you have two I/O watchers (for
599 example, STDOUT and STDERR for a program), and you want to wait for
600 both streams to close before activating a condvar:
601
602 my $cv = AnyEvent->condvar;
603
604 $cv->begin; # first watcher
605 my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
606 defined sysread $fh1, my $buf, 4096
607 or $cv->end;
608 });
609
610 $cv->begin; # second watcher
611 my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
612 defined sysread $fh2, my $buf, 4096
613 or $cv->end;
614 });
615
616 $cv->recv;
617
618 This works because for every event source (EOF on file handle),
619 there is one call to "begin", so the condvar waits for all calls to
620 "end" before sending.
621
622 The ping example mentioned above is slightly more complicated, as
623 the there are results to be passwd back, and the number of tasks
624 that are begung can potentially be zero:
593 625
594 my $cv = AnyEvent->condvar; 626 my $cv = AnyEvent->condvar;
595 627
596 my %result; 628 my %result;
597 $cv->begin (sub { $cv->send (\%result) }); 629 $cv->begin (sub { $cv->send (\%result) });
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617 the loop, which serves two important purposes: first, it sets the 649 the loop, which serves two important purposes: first, it sets the
618 callback to be called once the counter reaches 0, and second, it 650 callback to be called once the counter reaches 0, and second, it
619 ensures that "send" is called even when "no" hosts are being pinged 651 ensures that "send" is called even when "no" hosts are being pinged
620 (the loop doesn't execute once). 652 (the loop doesn't execute once).
621 653
622 This is the general pattern when you "fan out" into multiple 654 This is the general pattern when you "fan out" into multiple (but
623 subrequests: use an outer "begin"/"end" pair to set the callback and 655 potentially none) subrequests: use an outer "begin"/"end" pair to
624 ensure "end" is called at least once, and then, for each subrequest 656 set the callback and ensure "end" is called at least once, and then,
625 you start, call "begin" and for each subrequest you finish, call 657 for each subrequest you start, call "begin" and for each subrequest
626 "end". 658 you finish, call "end".
627 659
628 METHODS FOR CONSUMERS 660 METHODS FOR CONSUMERS
629 These methods should only be used by the consuming side, i.e. the code 661 These methods should only be used by the consuming side, i.e. the code
630 awaits the condition. 662 awaits the condition.
631 663
… …
640 function will call "croak". 672 function will call "croak".
641 673
642 In list context, all parameters passed to "send" will be returned, 674 In list context, all parameters passed to "send" will be returned,
643 in scalar context only the first one will be returned. 675 in scalar context only the first one will be returned.
644 676
677 Note that doing a blocking wait in a callback is not supported by
678 any event loop, that is, recursive invocation of a blocking "->recv"
679 is not allowed, and the "recv" call will "croak" if such a condition
680 is detected. This condition can be slightly loosened by using
681 Coro::AnyEvent, which allows you to do a blocking "->recv" from any
682 thread that doesn't run the event loop itself.
683
645 Not all event models support a blocking wait - some die in that case 684 Not all event models support a blocking wait - some die in that case
646 (programs might want to do that to stay interactive), so *if you are 685 (programs might want to do that to stay interactive), so *if you are
647 using this from a module, never require a blocking wait*, but let 686 using this from a module, never require a blocking wait*. Instead,
648 the caller decide whether the call will block or not (for example, 687 let the caller decide whether the call will block or not (for
649 by coupling condition variables with some kind of request results 688 example, by coupling condition variables with some kind of request
650 and supporting callbacks so the caller knows that getting the result 689 results and supporting callbacks so the caller knows that getting
651 will not block, while still supporting blocking waits if the caller 690 the result will not block, while still supporting blocking waits if
652 so desires). 691 the caller so desires).
653
654 Another reason *never* to "->recv" in a module is that you cannot
655 sensibly have two "->recv"'s in parallel, as that would require
656 multiple interpreters or coroutines/threads, none of which
657 "AnyEvent" can supply.
658
659 The Coro module, however, *can* and *does* supply coroutines and, in
660 fact, Coro::AnyEvent replaces AnyEvent's condvars by coroutine-safe
661 versions and also integrates coroutines into AnyEvent, making
662 blocking "->recv" calls perfectly safe as long as they are done from
663 another coroutine (one that doesn't run the event loop).
664 692
665 You can ensure that "-recv" never blocks by setting a callback and 693 You can ensure that "-recv" never blocks by setting a callback and
666 only calling "->recv" from within that callback (or at a later 694 only calling "->recv" from within that callback (or at a later
667 time). This will work even when the event loop does not support 695 time). This will work even when the event loop does not support
668 blocking waits otherwise. 696 blocking waits otherwise.
… …
678 The callback will be called when the condition becomes "true", i.e. 706 The callback will be called when the condition becomes "true", i.e.
679 when "send" or "croak" are called, with the only argument being the 707 when "send" or "croak" are called, with the only argument being the
680 condition variable itself. Calling "recv" inside the callback or at 708 condition variable itself. Calling "recv" inside the callback or at
681 any later time is guaranteed not to block. 709 any later time is guaranteed not to block.
682 710
711SUPPORTED EVENT LOOPS/BACKENDS
712 The available backend classes are (every class has its own manpage):
713
714 Backends that are autoprobed when no other event loop can be found.
715 EV is the preferred backend when no other event loop seems to be in
716 use. If EV is not installed, then AnyEvent will try Event, and,
717 failing that, will fall back to its own pure-perl implementation,
718 which is available everywhere as it comes with AnyEvent itself.
719
720 AnyEvent::Impl::EV based on EV (interface to libev, best choice).
721 AnyEvent::Impl::Event based on Event, very stable, few glitches.
722 AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
723
724 Backends that are transparently being picked up when they are used.
725 These will be used when they are currently loaded when the first
726 watcher is created, in which case it is assumed that the application
727 is using them. This means that AnyEvent will automatically pick the
728 right backend when the main program loads an event module before
729 anything starts to create watchers. Nothing special needs to be done
730 by the main program.
731
732 AnyEvent::Impl::Glib based on Glib, slow but very stable.
733 AnyEvent::Impl::Tk based on Tk, very broken.
734 AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
735 AnyEvent::Impl::POE based on POE, very slow, some limitations.
736
737 Backends with special needs.
738 Qt requires the Qt::Application to be instantiated first, but will
739 otherwise be picked up automatically. As long as the main program
740 instantiates the application before any AnyEvent watchers are
741 created, everything should just work.
742
743 AnyEvent::Impl::Qt based on Qt.
744
745 Support for IO::Async can only be partial, as it is too broken and
746 architecturally limited to even support the AnyEvent API. It also is
747 the only event loop that needs the loop to be set explicitly, so it
748 can only be used by a main program knowing about AnyEvent. See
749 AnyEvent::Impl::Async for the gory details.
750
751 AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
752
753 Event loops that are indirectly supported via other backends.
754 Some event loops can be supported via other modules:
755
756 There is no direct support for WxWidgets (Wx) or Prima.
757
758 WxWidgets has no support for watching file handles. However, you can
759 use WxWidgets through the POE adaptor, as POE has a Wx backend that
760 simply polls 20 times per second, which was considered to be too
761 horrible to even consider for AnyEvent.
762
763 Prima is not supported as nobody seems to be using it, but it has a
764 POE backend, so it can be supported through POE.
765
766 AnyEvent knows about both Prima and Wx, however, and will try to
767 load POE when detecting them, in the hope that POE will pick them
768 up, in which case everything will be automatic.
769
683GLOBAL VARIABLES AND FUNCTIONS 770GLOBAL VARIABLES AND FUNCTIONS
771 These are not normally required to use AnyEvent, but can be useful to
772 write AnyEvent extension modules.
773
684 $AnyEvent::MODEL 774 $AnyEvent::MODEL
685 Contains "undef" until the first watcher is being created. Then it 775 Contains "undef" until the first watcher is being created, before
776 the backend has been autodetected.
777
686 contains the event model that is being used, which is the name of 778 Afterwards it contains the event model that is being used, which is
687 the Perl class implementing the model. This class is usually one of 779 the name of the Perl class implementing the model. This class is
688 the "AnyEvent::Impl:xxx" modules, but can be any other class in the 780 usually one of the "AnyEvent::Impl:xxx" modules, but can be any
689 case AnyEvent has been extended at runtime (e.g. in *rxvt-unicode*). 781 other class in the case AnyEvent has been extended at runtime (e.g.
690 782 in *rxvt-unicode* it will be "urxvt::anyevent").
691 The known classes so far are:
692
693 AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
694 AnyEvent::Impl::Event based on Event, second best choice.
695 AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
696 AnyEvent::Impl::Glib based on Glib, third-best choice.
697 AnyEvent::Impl::Tk based on Tk, very bad choice.
698 AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
699 AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
700 AnyEvent::Impl::POE based on POE, not generic enough for full support.
701
702 There is no support for WxWidgets, as WxWidgets has no support for
703 watching file handles. However, you can use WxWidgets through the
704 POE Adaptor, as POE has a Wx backend that simply polls 20 times per
705 second, which was considered to be too horrible to even consider for
706 AnyEvent. Likewise, other POE backends can be used by AnyEvent by
707 using it's adaptor.
708
709 AnyEvent knows about Prima and Wx and will try to use POE when
710 autodetecting them.
711 783
712 AnyEvent::detect 784 AnyEvent::detect
713 Returns $AnyEvent::MODEL, forcing autodetection of the event model 785 Returns $AnyEvent::MODEL, forcing autodetection of the event model
714 if necessary. You should only call this function right before you 786 if necessary. You should only call this function right before you
715 would have created an AnyEvent watcher anyway, that is, as late as 787 would have created an AnyEvent watcher anyway, that is, as late as
716 possible at runtime. 788 possible at runtime, and not e.g. while initialising of your module.
789
790 If you need to do some initialisation before AnyEvent watchers are
791 created, use "post_detect".
717 792
718 $guard = AnyEvent::post_detect { BLOCK } 793 $guard = AnyEvent::post_detect { BLOCK }
719 Arranges for the code block to be executed as soon as the event 794 Arranges for the code block to be executed as soon as the event
720 model is autodetected (or immediately if this has already happened). 795 model is autodetected (or immediately if this has already happened).
796
797 The block will be executed *after* the actual backend has been
798 detected ($AnyEvent::MODEL is set), but *before* any watchers have
799 been created, so it is possible to e.g. patch @AnyEvent::ISA or do
800 other initialisations - see the sources of AnyEvent::Strict or
801 AnyEvent::AIO to see how this is used.
802
803 The most common usage is to create some global watchers, without
804 forcing event module detection too early, for example, AnyEvent::AIO
805 creates and installs the global IO::AIO watcher in a "post_detect"
806 block to avoid autodetecting the event module at load time.
721 807
722 If called in scalar or list context, then it creates and returns an 808 If called in scalar or list context, then it creates and returns an
723 object that automatically removes the callback again when it is 809 object that automatically removes the callback again when it is
724 destroyed. See Coro::BDB for a case where this is useful. 810 destroyed. See Coro::BDB for a case where this is useful.
725 811
… …
727 If there are any code references in this array (you can "push" to it 813 If there are any code references in this array (you can "push" to it
728 before or after loading AnyEvent), then they will called directly 814 before or after loading AnyEvent), then they will called directly
729 after the event loop has been chosen. 815 after the event loop has been chosen.
730 816
731 You should check $AnyEvent::MODEL before adding to this array, 817 You should check $AnyEvent::MODEL before adding to this array,
732 though: if it contains a true value then the event loop has already 818 though: if it is defined then the event loop has already been
733 been detected, and the array will be ignored. 819 detected, and the array will be ignored.
734 820
735 Best use "AnyEvent::post_detect { BLOCK }" instead. 821 Best use "AnyEvent::post_detect { BLOCK }" when your application
822 allows it,as it takes care of these details.
823
824 This variable is mainly useful for modules that can do something
825 useful when AnyEvent is used and thus want to know when it is
826 initialised, but do not need to even load it by default. This array
827 provides the means to hook into AnyEvent passively, without loading
828 it.
736 829
737WHAT TO DO IN A MODULE 830WHAT TO DO IN A MODULE
738 As a module author, you should "use AnyEvent" and call AnyEvent methods 831 As a module author, you should "use AnyEvent" and call AnyEvent methods
739 freely, but you should not load a specific event module or rely on it. 832 freely, but you should not load a specific event module or rely on it.
740 833
… …
791 variable somewhere, waiting for it, and sending it when the program 884 variable somewhere, waiting for it, and sending it when the program
792 should exit cleanly. 885 should exit cleanly.
793 886
794OTHER MODULES 887OTHER MODULES
795 The following is a non-exhaustive list of additional modules that use 888 The following is a non-exhaustive list of additional modules that use
796 AnyEvent and can therefore be mixed easily with other AnyEvent modules 889 AnyEvent as a client and can therefore be mixed easily with other
797 in the same program. Some of the modules come with AnyEvent, some are 890 AnyEvent modules and other event loops in the same program. Some of the
798 available via CPAN. 891 modules come with AnyEvent, most are available via CPAN.
799 892
800 AnyEvent::Util 893 AnyEvent::Util
801 Contains various utility functions that replace often-used but 894 Contains various utility functions that replace often-used but
802 blocking functions such as "inet_aton" by event-/callback-based 895 blocking functions such as "inet_aton" by event-/callback-based
803 versions. 896 versions.
… …
809 more. 902 more.
810 903
811 AnyEvent::Handle 904 AnyEvent::Handle
812 Provide read and write buffers, manages watchers for reads and 905 Provide read and write buffers, manages watchers for reads and
813 writes, supports raw and formatted I/O, I/O queued and fully 906 writes, supports raw and formatted I/O, I/O queued and fully
814 transparent and non-blocking SSL/TLS. 907 transparent and non-blocking SSL/TLS (via AnyEvent::TLS.
815 908
816 AnyEvent::DNS 909 AnyEvent::DNS
817 Provides rich asynchronous DNS resolver capabilities. 910 Provides rich asynchronous DNS resolver capabilities.
818 911
819 AnyEvent::HTTP 912 AnyEvent::HTTP
… …
840 933
841 AnyEvent::GPSD 934 AnyEvent::GPSD
842 A non-blocking interface to gpsd, a daemon delivering GPS 935 A non-blocking interface to gpsd, a daemon delivering GPS
843 information. 936 information.
844 937
938 AnyEvent::IRC
939 AnyEvent based IRC client module family (replacing the older
940 Net::IRC3).
941
942 AnyEvent::XMPP
943 AnyEvent based XMPP (Jabber protocol) module family (replacing the
944 older Net::XMPP2>.
945
845 AnyEvent::IGS 946 AnyEvent::IGS
846 A non-blocking interface to the Internet Go Server protocol (used by 947 A non-blocking interface to the Internet Go Server protocol (used by
847 App::IGS). 948 App::IGS).
848 949
849 AnyEvent::IRC
850 AnyEvent based IRC client module family (replacing the older
851 Net::IRC3).
852
853 Net::XMPP2
854 AnyEvent based XMPP (Jabber protocol) module family.
855
856 Net::FCP 950 Net::FCP
857 AnyEvent-based implementation of the Freenet Client Protocol, 951 AnyEvent-based implementation of the Freenet Client Protocol,
858 birthplace of AnyEvent. 952 birthplace of AnyEvent.
859 953
860 Event::ExecFlow 954 Event::ExecFlow
861 High level API for event-based execution flow control. 955 High level API for event-based execution flow control.
862 956
863 Coro 957 Coro
864 Has special support for AnyEvent via Coro::AnyEvent. 958 Has special support for AnyEvent via Coro::AnyEvent.
865
866 IO::Lambda
867 The lambda approach to I/O - don't ask, look there. Can use
868 AnyEvent.
869 959
870ERROR AND EXCEPTION HANDLING 960ERROR AND EXCEPTION HANDLING
871 In general, AnyEvent does not do any error handling - it relies on the 961 In general, AnyEvent does not do any error handling - it relies on the
872 caller to do that if required. The AnyEvent::Strict module (see also the 962 caller to do that if required. The AnyEvent::Strict module (see also the
873 "PERL_ANYEVENT_STRICT" environment variable, below) provides strict 963 "PERL_ANYEVENT_STRICT" environment variable, below) provides strict
… …
906 "PERL_ANYEVENT_STRICT" 996 "PERL_ANYEVENT_STRICT"
907 AnyEvent does not do much argument checking by default, as thorough 997 AnyEvent does not do much argument checking by default, as thorough
908 argument checking is very costly. Setting this variable to a true 998 argument checking is very costly. Setting this variable to a true
909 value will cause AnyEvent to load "AnyEvent::Strict" and then to 999 value will cause AnyEvent to load "AnyEvent::Strict" and then to
910 thoroughly check the arguments passed to most method calls. If it 1000 thoroughly check the arguments passed to most method calls. If it
911 finds any problems it will croak. 1001 finds any problems, it will croak.
912 1002
913 In other words, enables "strict" mode. 1003 In other words, enables "strict" mode.
914 1004
915 Unlike "use strict", it is definitely recommended ot keep it off in 1005 Unlike "use strict", it is definitely recommended to keep it off in
916 production. Keeping "PERL_ANYEVENT_STRICT=1" in your environment 1006 production. Keeping "PERL_ANYEVENT_STRICT=1" in your environment
917 while developing programs can be very useful, however. 1007 while developing programs can be very useful, however.
918 1008
919 "PERL_ANYEVENT_MODEL" 1009 "PERL_ANYEVENT_MODEL"
920 This can be used to specify the event model to be used by AnyEvent, 1010 This can be used to specify the event model to be used by AnyEvent,
… …
963 EDNS0 in its DNS requests. 1053 EDNS0 in its DNS requests.
964 1054
965 "PERL_ANYEVENT_MAX_FORKS" 1055 "PERL_ANYEVENT_MAX_FORKS"
966 The maximum number of child processes that 1056 The maximum number of child processes that
967 "AnyEvent::Util::fork_call" will create in parallel. 1057 "AnyEvent::Util::fork_call" will create in parallel.
1058
1059 "PERL_ANYEVENT_MAX_OUTSTANDING_DNS"
1060 The default value for the "max_outstanding" parameter for the
1061 default DNS resolver - this is the maximum number of parallel DNS
1062 requests that are sent to the DNS server.
1063
1064 "PERL_ANYEVENT_RESOLV_CONF"
1065 The file to use instead of /etc/resolv.conf (or OS-specific
1066 configuration) in the default resolver. When set to the empty
1067 string, no default config will be used.
1068
1069 "PERL_ANYEVENT_CA_FILE", "PERL_ANYEVENT_CA_PATH".
1070 When neither "ca_file" nor "ca_path" was specified during
1071 AnyEvent::TLS context creation, and either of these environment
1072 variables exist, they will be used to specify CA certificate
1073 locations instead of a system-dependent default.
968 1074
969SUPPLYING YOUR OWN EVENT MODEL INTERFACE 1075SUPPLYING YOUR OWN EVENT MODEL INTERFACE
970 This is an advanced topic that you do not normally need to use AnyEvent 1076 This is an advanced topic that you do not normally need to use AnyEvent
971 in a module. This section is only of use to event loop authors who want 1077 in a module. This section is only of use to event loop authors who want
972 to provide AnyEvent compatibility. 1078 to provide AnyEvent compatibility.
… …
1208 EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers 1314 EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers
1209 CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal 1315 CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal
1210 Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation 1316 Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation
1211 Event/Event 16000 517 32.20 31.80 0.81 Event native interface 1317 Event/Event 16000 517 32.20 31.80 0.81 Event native interface
1212 Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers 1318 Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers
1319 IOAsync/Any 16000 989 38.10 32.77 11.13 via IO::Async::Loop::IO_Poll
1320 IOAsync/Any 16000 990 37.59 29.50 10.61 via IO::Async::Loop::Epoll
1213 Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour 1321 Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour
1214 Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers 1322 Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers
1215 POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event 1323 POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event
1216 POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select 1324 POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select
1217 1325
… …
1246 few of them active), of course, but this was not subject of this 1354 few of them active), of course, but this was not subject of this
1247 benchmark. 1355 benchmark.
1248 1356
1249 The "Event" module has a relatively high setup and callback invocation 1357 The "Event" module has a relatively high setup and callback invocation
1250 cost, but overall scores in on the third place. 1358 cost, but overall scores in on the third place.
1359
1360 "IO::Async" performs admirably well, about on par with "Event", even
1361 when using its pure perl backend.
1251 1362
1252 "Glib"'s memory usage is quite a bit higher, but it features a faster 1363 "Glib"'s memory usage is quite a bit higher, but it features a faster
1253 callback invocation and overall ends up in the same class as "Event". 1364 callback invocation and overall ends up in the same class as "Event".
1254 However, Glib scales extremely badly, doubling the number of watchers 1365 However, Glib scales extremely badly, doubling the number of watchers
1255 increases the processing time by more than a factor of four, making it 1366 increases the processing time by more than a factor of four, making it
… …
1326 single "request", that is, reading the token from the pipe and 1437 single "request", that is, reading the token from the pipe and
1327 forwarding it to another server. This includes deleting the old timeout 1438 forwarding it to another server. This includes deleting the old timeout
1328 and creating a new one that moves the timeout into the future. 1439 and creating a new one that moves the timeout into the future.
1329 1440
1330 Results 1441 Results
1331 name sockets create request 1442 name sockets create request
1332 EV 20000 69.01 11.16 1443 EV 20000 69.01 11.16
1333 Perl 20000 73.32 35.87 1444 Perl 20000 73.32 35.87
1445 IOAsync 20000 157.00 98.14 epoll
1446 IOAsync 20000 159.31 616.06 poll
1334 Event 20000 212.62 257.32 1447 Event 20000 212.62 257.32
1335 Glib 20000 651.16 1896.30 1448 Glib 20000 651.16 1896.30
1336 POE 20000 349.67 12317.24 uses POE::Loop::Event 1449 POE 20000 349.67 12317.24 uses POE::Loop::Event
1337 1450
1338 Discussion 1451 Discussion
1339 This benchmark *does* measure scalability and overall performance of the 1452 This benchmark *does* measure scalability and overall performance of the
1340 particular event loop. 1453 particular event loop.
1341 1454
1342 EV is again fastest. Since it is using epoll on my system, the setup 1455 EV is again fastest. Since it is using epoll on my system, the setup
1343 time is relatively high, though. 1456 time is relatively high, though.
1344 1457
1345 Perl surprisingly comes second. It is much faster than the C-based event 1458 Perl surprisingly comes second. It is much faster than the C-based event
1346 loops Event and Glib. 1459 loops Event and Glib.
1460
1461 IO::Async performs very well when using its epoll backend, and still
1462 quite good compared to Glib when using its pure perl backend.
1347 1463
1348 Event suffers from high setup time as well (look at its code and you 1464 Event suffers from high setup time as well (look at its code and you
1349 will understand why). Callback invocation also has a high overhead 1465 will understand why). Callback invocation also has a high overhead
1350 compared to the "$_->() for .."-style loop that the Perl event loop 1466 compared to the "$_->() for .."-style loop that the Perl event loop
1351 uses. Event uses select or poll in basically all documented 1467 uses. Event uses select or poll in basically all documented
… …
1407 THE IO::Lambda BENCHMARK 1523 THE IO::Lambda BENCHMARK
1408 Recently I was told about the benchmark in the IO::Lambda manpage, which 1524 Recently I was told about the benchmark in the IO::Lambda manpage, which
1409 could be misinterpreted to make AnyEvent look bad. In fact, the 1525 could be misinterpreted to make AnyEvent look bad. In fact, the
1410 benchmark simply compares IO::Lambda with POE, and IO::Lambda looks 1526 benchmark simply compares IO::Lambda with POE, and IO::Lambda looks
1411 better (which shouldn't come as a surprise to anybody). As such, the 1527 better (which shouldn't come as a surprise to anybody). As such, the
1412 benchmark is fine, and shows that the AnyEvent backend from IO::Lambda 1528 benchmark is fine, and mostly shows that the AnyEvent backend from
1413 isn't very optimal. But how would AnyEvent compare when used without the 1529 IO::Lambda isn't very optimal. But how would AnyEvent compare when used
1414 extra baggage? To explore this, I wrote the equivalent benchmark for 1530 without the extra baggage? To explore this, I wrote the equivalent
1415 AnyEvent. 1531 benchmark for AnyEvent.
1416 1532
1417 The benchmark itself creates an echo-server, and then, for 500 times, 1533 The benchmark itself creates an echo-server, and then, for 500 times,
1418 connects to the echo server, sends a line, waits for the reply, and then 1534 connects to the echo server, sends a line, waits for the reply, and then
1419 creates the next connection. This is a rather bad benchmark, as it 1535 creates the next connection. This is a rather bad benchmark, as it
1420 doesn't test the efficiency of the framework, but it is a benchmark 1536 doesn't test the efficiency of the framework or much non-blocking I/O,
1421 nevertheless. 1537 but it is a benchmark nevertheless.
1422 1538
1423 name runtime 1539 name runtime
1424 Lambda/select 0.330 sec 1540 Lambda/select 0.330 sec
1425 + optimized 0.122 sec 1541 + optimized 0.122 sec
1426 Lambda/AnyEvent 0.327 sec 1542 Lambda/AnyEvent 0.327 sec
… …
1432 1548
1433 AnyEvent/select/nb 0.085 sec 1549 AnyEvent/select/nb 0.085 sec
1434 AnyEvent/EV/nb 0.068 sec 1550 AnyEvent/EV/nb 0.068 sec
1435 +state machine 0.134 sec 1551 +state machine 0.134 sec
1436 1552
1437 The benchmark is also a bit unfair (my fault) - the IO::Lambda 1553 The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
1438 benchmarks actually make blocking connects and use 100% blocking I/O, 1554 benchmarks actually make blocking connects and use 100% blocking I/O,
1439 defeating the purpose of an event-based solution. All of the newly 1555 defeating the purpose of an event-based solution. All of the newly
1440 written AnyEvent benchmarks use 100% non-blocking connects (using 1556 written AnyEvent benchmarks use 100% non-blocking connects (using
1441 AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS 1557 AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
1442 resolver), so AnyEvent is at a disadvantage here as non-blocking 1558 resolver), so AnyEvent is at a disadvantage here, as non-blocking
1443 connects generally require a lot more bookkeeping and event handling 1559 connects generally require a lot more bookkeeping and event handling
1444 than blocking connects (which involve a single syscall only). 1560 than blocking connects (which involve a single syscall only).
1445 1561
1446 The last AnyEvent benchmark additionally uses AnyEvent::Handle, which 1562 The last AnyEvent benchmark additionally uses AnyEvent::Handle, which
1447 offers similar expressive power as POE and IO::Lambda (using 1563 offers similar expressive power as POE and IO::Lambda, using
1448 conventional Perl syntax), which means both the echo server and the 1564 conventional Perl syntax. This means that both the echo server and the
1449 client are 100% non-blocking w.r.t. I/O, further placing it at a 1565 client are 100% non-blocking, further placing it at a disadvantage.
1450 disadvantage.
1451 1566
1452 As you can see, AnyEvent + EV even beats the hand-optimised "raw sockets 1567 As you can see, the AnyEvent + EV combination even beats the
1453 benchmark", while AnyEvent + its pure perl backend easily beats 1568 hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
1454 IO::Lambda and POE. 1569 backend easily beats IO::Lambda and POE.
1455 1570
1456 And even the 100% non-blocking version written using the high-level (and 1571 And even the 100% non-blocking version written using the high-level (and
1457 slow :) AnyEvent::Handle abstraction beats both POE and IO::Lambda, even 1572 slow :) AnyEvent::Handle abstraction beats both POE and IO::Lambda by a
1458 thought it does all of DNS, tcp-connect and socket I/O in a non-blocking 1573 large margin, even though it does all of DNS, tcp-connect and socket I/O
1459 way. 1574 in a non-blocking way.
1460 1575
1461 The two AnyEvent benchmarks can be found as eg/ae0.pl and eg/ae2.pl in 1576 The two AnyEvent benchmarks programs can be found as eg/ae0.pl and
1462 the AnyEvent distribution, the remaining benchmarks are part of the 1577 eg/ae2.pl in the AnyEvent distribution, the remaining benchmarks are
1463 IO::lambda distribution and were used without any changes. 1578 part of the IO::lambda distribution and were used without any changes.
1464 1579
1465SIGNALS 1580SIGNALS
1466 AnyEvent currently installs handlers for these signals: 1581 AnyEvent currently installs handlers for these signals:
1467 1582
1468 SIGCHLD 1583 SIGCHLD
1469 A handler for "SIGCHLD" is installed by AnyEvent's child watcher 1584 A handler for "SIGCHLD" is installed by AnyEvent's child watcher
1470 emulation for event loops that do not support them natively. Also, 1585 emulation for event loops that do not support them natively. Also,
1471 some event loops install a similar handler. 1586 some event loops install a similar handler.
1587
1588 Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE,
1589 then AnyEvent will reset it to default, to avoid losing child exit
1590 statuses.
1472 1591
1473 SIGPIPE 1592 SIGPIPE
1474 A no-op handler is installed for "SIGPIPE" when $SIG{PIPE} is 1593 A no-op handler is installed for "SIGPIPE" when $SIG{PIPE} is
1475 "undef" when AnyEvent gets loaded. 1594 "undef" when AnyEvent gets loaded.
1476 1595
… …
1512 Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can 1631 Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
1513 be used to probe what backend is used and gain other information (which 1632 be used to probe what backend is used and gain other information (which
1514 is probably even less useful to an attacker than PERL_ANYEVENT_MODEL), 1633 is probably even less useful to an attacker than PERL_ANYEVENT_MODEL),
1515 and $ENV{PERL_ANYEVENT_STRICT}. 1634 and $ENV{PERL_ANYEVENT_STRICT}.
1516 1635
1636 Note that AnyEvent will remove *all* environment variables starting with
1637 "PERL_ANYEVENT_" from %ENV when it is loaded while taint mode is
1638 enabled.
1639
1517BUGS 1640BUGS
1518 Perl 5.8 has numerous memleaks that sometimes hit this module and are 1641 Perl 5.8 has numerous memleaks that sometimes hit this module and are
1519 hard to work around. If you suffer from memleaks, first upgrade to Perl 1642 hard to work around. If you suffer from memleaks, first upgrade to Perl
1520 5.10 and check wether the leaks still show up. (Perl 5.10.0 has other 1643 5.10 and check wether the leaks still show up. (Perl 5.10.0 has other
1521 annoying memleaks, such as leaking on "map" and "grep" but it is usually 1644 annoying memleaks, such as leaking on "map" and "grep" but it is usually
… …
1527 Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk, 1650 Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk,
1528 Event::Lib, Qt, POE. 1651 Event::Lib, Qt, POE.
1529 1652
1530 Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event, 1653 Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,
1531 AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl, 1654 AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,
1532 AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE. 1655 AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE,
1656 AnyEvent::Impl::IOAsync.
1533 1657
1534 Non-blocking file handles, sockets, TCP clients and servers: 1658 Non-blocking file handles, sockets, TCP clients and servers:
1535 AnyEvent::Handle, AnyEvent::Socket. 1659 AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS.
1536 1660
1537 Asynchronous DNS: AnyEvent::DNS. 1661 Asynchronous DNS: AnyEvent::DNS.
1538 1662
1539 Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event, 1663 Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,
1540 1664
1541 Nontrivial usage examples: Net::FCP, Net::XMPP2, AnyEvent::DNS. 1665 Nontrivial usage examples: AnyEvent::GPSD, AnyEvent::XMPP,
1666 AnyEvent::HTTP.
1542 1667
1543AUTHOR 1668AUTHOR
1544 Marc Lehmann <schmorp@schmorp.de> 1669 Marc Lehmann <schmorp@schmorp.de>
1545 http://home.schmorp.de/ 1670 http://home.schmorp.de/
1546 1671

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