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Revision 1.43 by root, Thu Jul 9 08:37:06 2009 UTC

1NAME 1NAME
2 AnyEvent - provide framework for multiple event loops 2 AnyEvent - provide framework for multiple event loops
3 3
4 EV, Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event 4 EV, Event, Glib, Tk, Perl, Event::Lib, Qt and POE are various supported
5 loops 5 event loops.
6 6
7SYNOPSIS 7SYNOPSIS
8 use AnyEvent; 8 use AnyEvent;
9 9
10 # file descriptor readable
10 my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub { ... }); 11 my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... });
11 12
13 # one-shot or repeating timers
12 my $w = AnyEvent->timer (after => $seconds, cb => sub { ... }); 14 my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
13 my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ... 15 my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...
14 16
15 print AnyEvent->now; # prints current event loop time 17 print AnyEvent->now; # prints current event loop time
16 print AnyEvent->time; # think Time::HiRes::time or simply CORE::time. 18 print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
17 19
20 # POSIX signal
18 my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... }); 21 my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });
19 22
23 # child process exit
20 my $w = AnyEvent->child (pid => $pid, cb => sub { 24 my $w = AnyEvent->child (pid => $pid, cb => sub {
21 my ($pid, $status) = @_; 25 my ($pid, $status) = @_;
22 ... 26 ...
23 }); 27 });
28
29 # called when event loop idle (if applicable)
30 my $w = AnyEvent->idle (cb => sub { ... });
24 31
25 my $w = AnyEvent->condvar; # stores whether a condition was flagged 32 my $w = AnyEvent->condvar; # stores whether a condition was flagged
26 $w->send; # wake up current and all future recv's 33 $w->send; # wake up current and all future recv's
27 $w->recv; # enters "main loop" till $condvar gets ->send 34 $w->recv; # enters "main loop" till $condvar gets ->send
28 # use a condvar in callback mode: 35 # use a condvar in callback mode:
… …
162 169
163 I/O WATCHERS 170 I/O WATCHERS
164 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
165 the following mandatory key-value pairs as arguments: 172 the following mandatory key-value pairs as arguments:
166 173
167 "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
168 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
169 handle). Note that only file handles pointing to things for which 176 handle). Note that only file handles pointing to things for which
170 non-blocking operation makes sense are allowed. This includes sockets, 177 non-blocking operation makes sense are allowed. This includes sockets,
171 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
172 files or block devices. 179 files or block devices.
… …
373 380
374 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
375 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
376 could have exited already (and no SIGCHLD will be sent anymore). 383 could have exited already (and no SIGCHLD will be sent anymore).
377 384
378 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
379 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
380 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).
381 place). 389 AnyEvent's pure perl event loop handles all cases correctly regardless
390 of when you start the watcher.
382 391
383 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
384 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
385 you "fork" the child (alternatively, you can call "AnyEvent::detect"). 394 you "fork" the child (alternatively, you can call "AnyEvent::detect").
386 395
387 Example: fork a process and wait for it 396 Example: fork a process and wait for it
388 397
389 my $done = AnyEvent->condvar; 398 my $done = AnyEvent->condvar;
390 399
391 my $pid = fork or exit 5; 400 my $pid = fork or exit 5;
392 401
393 my $w = AnyEvent->child ( 402 my $w = AnyEvent->child (
394 pid => $pid, 403 pid => $pid,
395 cb => sub { 404 cb => sub {
396 my ($pid, $status) = @_; 405 my ($pid, $status) = @_;
397 warn "pid $pid exited with status $status"; 406 warn "pid $pid exited with status $status";
398 $done->send; 407 $done->send;
399 }, 408 },
400 ); 409 );
401 410
402 # do something else, then wait for process exit 411 # do something else, then wait for process exit
403 $done->recv; 412 $done->recv;
413
414 IDLE WATCHERS
415 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
417 "nothing better to do" is usually defined to be "no other events need
418 attention by the event loop".
419
420 Idle watchers ideally get invoked when the event loop has nothing better
421 to do, just before it would block the process to wait for new events.
422 Instead of blocking, the idle watcher is invoked.
423
424 Most event loops unfortunately do not really support idle watchers (only
425 EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
426 will simply call the callback "from time to time".
427
428 Example: read lines from STDIN, but only process them when the program
429 is otherwise idle:
430
431 my @lines; # read data
432 my $idle_w;
433 my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
434 push @lines, scalar <STDIN>;
435
436 # start an idle watcher, if not already done
437 $idle_w ||= AnyEvent->idle (cb => sub {
438 # handle only one line, when there are lines left
439 if (my $line = shift @lines) {
440 print "handled when idle: $line";
441 } else {
442 # otherwise disable the idle watcher again
443 undef $idle_w;
444 }
445 });
446 });
404 447
405 CONDITION VARIABLES 448 CONDITION VARIABLES
406 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
407 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
408 will actively watch for new events and call your callbacks. 451 will actively watch for new events and call your callbacks.
… …
534 This can be used to signal any errors to the condition variable 577 This can be used to signal any errors to the condition variable
535 user/consumer. 578 user/consumer.
536 579
537 $cv->begin ([group callback]) 580 $cv->begin ([group callback])
538 $cv->end 581 $cv->end
539 These two methods are EXPERIMENTAL and MIGHT CHANGE.
540
541 These two methods can be used to combine many transactions/events 582 These two methods can be used to combine many transactions/events
542 into one. For example, a function that pings many hosts in parallel 583 into one. For example, a function that pings many hosts in parallel
543 might want to use a condition variable for the whole process. 584 might want to use a condition variable for the whole process.
544 585
545 Every call to "->begin" will increment a counter, and every call to 586 Every call to "->begin" will increment a counter, and every call to
546 "->end" will decrement it. If the counter reaches 0 in "->end", the 587 "->end" will decrement it. If the counter reaches 0 in "->end", the
547 (last) callback passed to "begin" will be executed. That callback is 588 (last) callback passed to "begin" will be executed. That callback is
548 *supposed* to call "->send", but that is not required. If no 589 *supposed* to call "->send", but that is not required. If no
549 callback was set, "send" will be called without any arguments. 590 callback was set, "send" will be called without any arguments.
550 591
551 Let's clarify this with the ping example: 592 You can think of "$cv->send" giving you an OR condition (one call
593 sends), while "$cv->begin" and "$cv->end" giving you an AND
594 condition (all "begin" calls must be "end"'ed before the condvar
595 sends).
596
597 Let's start with a simple example: you have two I/O watchers (for
598 example, STDOUT and STDERR for a program), and you want to wait for
599 both streams to close before activating a condvar:
600
601 my $cv = AnyEvent->condvar;
602
603 $cv->begin; # first watcher
604 my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
605 defined sysread $fh1, my $buf, 4096
606 or $cv->end;
607 });
608
609 $cv->begin; # second watcher
610 my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
611 defined sysread $fh2, my $buf, 4096
612 or $cv->end;
613 });
614
615 $cv->recv;
616
617 This works because for every event source (EOF on file handle),
618 there is one call to "begin", so the condvar waits for all calls to
619 "end" before sending.
620
621 The ping example mentioned above is slightly more complicated, as
622 the there are results to be passwd back, and the number of tasks
623 that are begung can potentially be zero:
552 624
553 my $cv = AnyEvent->condvar; 625 my $cv = AnyEvent->condvar;
554 626
555 my %result; 627 my %result;
556 $cv->begin (sub { $cv->send (\%result) }); 628 $cv->begin (sub { $cv->send (\%result) });
… …
576 the loop, which serves two important purposes: first, it sets the 648 the loop, which serves two important purposes: first, it sets the
577 callback to be called once the counter reaches 0, and second, it 649 callback to be called once the counter reaches 0, and second, it
578 ensures that "send" is called even when "no" hosts are being pinged 650 ensures that "send" is called even when "no" hosts are being pinged
579 (the loop doesn't execute once). 651 (the loop doesn't execute once).
580 652
581 This is the general pattern when you "fan out" into multiple 653 This is the general pattern when you "fan out" into multiple (but
582 subrequests: use an outer "begin"/"end" pair to set the callback and 654 potentially none) subrequests: use an outer "begin"/"end" pair to
583 ensure "end" is called at least once, and then, for each subrequest 655 set the callback and ensure "end" is called at least once, and then,
584 you start, call "begin" and for each subrequest you finish, call 656 for each subrequest you start, call "begin" and for each subrequest
585 "end". 657 you finish, call "end".
586 658
587 METHODS FOR CONSUMERS 659 METHODS FOR CONSUMERS
588 These methods should only be used by the consuming side, i.e. the code 660 These methods should only be used by the consuming side, i.e. the code
589 awaits the condition. 661 awaits the condition.
590 662
… …
637 The callback will be called when the condition becomes "true", i.e. 709 The callback will be called when the condition becomes "true", i.e.
638 when "send" or "croak" are called, with the only argument being the 710 when "send" or "croak" are called, with the only argument being the
639 condition variable itself. Calling "recv" inside the callback or at 711 condition variable itself. Calling "recv" inside the callback or at
640 any later time is guaranteed not to block. 712 any later time is guaranteed not to block.
641 713
714SUPPORTED EVENT LOOPS/BACKENDS
715 The available backend classes are (every class has its own manpage):
716
717 Backends that are autoprobed when no other event loop can be found.
718 EV is the preferred backend when no other event loop seems to be in
719 use. If EV is not installed, then AnyEvent will try Event, and,
720 failing that, will fall back to its own pure-perl implementation,
721 which is available everywhere as it comes with AnyEvent itself.
722
723 AnyEvent::Impl::EV based on EV (interface to libev, best choice).
724 AnyEvent::Impl::Event based on Event, very stable, few glitches.
725 AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
726
727 Backends that are transparently being picked up when they are used.
728 These will be used when they are currently loaded when the first
729 watcher is created, in which case it is assumed that the application
730 is using them. This means that AnyEvent will automatically pick the
731 right backend when the main program loads an event module before
732 anything starts to create watchers. Nothing special needs to be done
733 by the main program.
734
735 AnyEvent::Impl::Glib based on Glib, slow but very stable.
736 AnyEvent::Impl::Tk based on Tk, very broken.
737 AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
738 AnyEvent::Impl::POE based on POE, very slow, some limitations.
739
740 Backends with special needs.
741 Qt requires the Qt::Application to be instantiated first, but will
742 otherwise be picked up automatically. As long as the main program
743 instantiates the application before any AnyEvent watchers are
744 created, everything should just work.
745
746 AnyEvent::Impl::Qt based on Qt.
747
748 Support for IO::Async can only be partial, as it is too broken and
749 architecturally limited to even support the AnyEvent API. It also is
750 the only event loop that needs the loop to be set explicitly, so it
751 can only be used by a main program knowing about AnyEvent. See
752 AnyEvent::Impl::Async for the gory details.
753
754 AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
755
756 Event loops that are indirectly supported via other backends.
757 Some event loops can be supported via other modules:
758
759 There is no direct support for WxWidgets (Wx) or Prima.
760
761 WxWidgets has no support for watching file handles. However, you can
762 use WxWidgets through the POE adaptor, as POE has a Wx backend that
763 simply polls 20 times per second, which was considered to be too
764 horrible to even consider for AnyEvent.
765
766 Prima is not supported as nobody seems to be using it, but it has a
767 POE backend, so it can be supported through POE.
768
769 AnyEvent knows about both Prima and Wx, however, and will try to
770 load POE when detecting them, in the hope that POE will pick them
771 up, in which case everything will be automatic.
772
642GLOBAL VARIABLES AND FUNCTIONS 773GLOBAL VARIABLES AND FUNCTIONS
774 These are not normally required to use AnyEvent, but can be useful to
775 write AnyEvent extension modules.
776
643 $AnyEvent::MODEL 777 $AnyEvent::MODEL
644 Contains "undef" until the first watcher is being created. Then it 778 Contains "undef" until the first watcher is being created, before
779 the backend has been autodetected.
780
645 contains the event model that is being used, which is the name of 781 Afterwards it contains the event model that is being used, which is
646 the Perl class implementing the model. This class is usually one of 782 the name of the Perl class implementing the model. This class is
647 the "AnyEvent::Impl:xxx" modules, but can be any other class in the 783 usually one of the "AnyEvent::Impl:xxx" modules, but can be any
648 case AnyEvent has been extended at runtime (e.g. in *rxvt-unicode*). 784 other class in the case AnyEvent has been extended at runtime (e.g.
649 785 in *rxvt-unicode* it will be "urxvt::anyevent").
650 The known classes so far are:
651
652 AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
653 AnyEvent::Impl::Event based on Event, second best choice.
654 AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
655 AnyEvent::Impl::Glib based on Glib, third-best choice.
656 AnyEvent::Impl::Tk based on Tk, very bad choice.
657 AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
658 AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
659 AnyEvent::Impl::POE based on POE, not generic enough for full support.
660
661 There is no support for WxWidgets, as WxWidgets has no support for
662 watching file handles. However, you can use WxWidgets through the
663 POE Adaptor, as POE has a Wx backend that simply polls 20 times per
664 second, which was considered to be too horrible to even consider for
665 AnyEvent. Likewise, other POE backends can be used by AnyEvent by
666 using it's adaptor.
667
668 AnyEvent knows about Prima and Wx and will try to use POE when
669 autodetecting them.
670 786
671 AnyEvent::detect 787 AnyEvent::detect
672 Returns $AnyEvent::MODEL, forcing autodetection of the event model 788 Returns $AnyEvent::MODEL, forcing autodetection of the event model
673 if necessary. You should only call this function right before you 789 if necessary. You should only call this function right before you
674 would have created an AnyEvent watcher anyway, that is, as late as 790 would have created an AnyEvent watcher anyway, that is, as late as
675 possible at runtime. 791 possible at runtime, and not e.g. while initialising of your module.
792
793 If you need to do some initialisation before AnyEvent watchers are
794 created, use "post_detect".
676 795
677 $guard = AnyEvent::post_detect { BLOCK } 796 $guard = AnyEvent::post_detect { BLOCK }
678 Arranges for the code block to be executed as soon as the event 797 Arranges for the code block to be executed as soon as the event
679 model is autodetected (or immediately if this has already happened). 798 model is autodetected (or immediately if this has already happened).
799
800 The block will be executed *after* the actual backend has been
801 detected ($AnyEvent::MODEL is set), but *before* any watchers have
802 been created, so it is possible to e.g. patch @AnyEvent::ISA or do
803 other initialisations - see the sources of AnyEvent::Strict or
804 AnyEvent::AIO to see how this is used.
805
806 The most common usage is to create some global watchers, without
807 forcing event module detection too early, for example, AnyEvent::AIO
808 creates and installs the global IO::AIO watcher in a "post_detect"
809 block to avoid autodetecting the event module at load time.
680 810
681 If called in scalar or list context, then it creates and returns an 811 If called in scalar or list context, then it creates and returns an
682 object that automatically removes the callback again when it is 812 object that automatically removes the callback again when it is
683 destroyed. See Coro::BDB for a case where this is useful. 813 destroyed. See Coro::BDB for a case where this is useful.
684 814
… …
686 If there are any code references in this array (you can "push" to it 816 If there are any code references in this array (you can "push" to it
687 before or after loading AnyEvent), then they will called directly 817 before or after loading AnyEvent), then they will called directly
688 after the event loop has been chosen. 818 after the event loop has been chosen.
689 819
690 You should check $AnyEvent::MODEL before adding to this array, 820 You should check $AnyEvent::MODEL before adding to this array,
691 though: if it contains a true value then the event loop has already 821 though: if it is defined then the event loop has already been
692 been detected, and the array will be ignored. 822 detected, and the array will be ignored.
693 823
694 Best use "AnyEvent::post_detect { BLOCK }" instead. 824 Best use "AnyEvent::post_detect { BLOCK }" when your application
825 allows it,as it takes care of these details.
826
827 This variable is mainly useful for modules that can do something
828 useful when AnyEvent is used and thus want to know when it is
829 initialised, but do not need to even load it by default. This array
830 provides the means to hook into AnyEvent passively, without loading
831 it.
695 832
696WHAT TO DO IN A MODULE 833WHAT TO DO IN A MODULE
697 As a module author, you should "use AnyEvent" and call AnyEvent methods 834 As a module author, you should "use AnyEvent" and call AnyEvent methods
698 freely, but you should not load a specific event module or rely on it. 835 freely, but you should not load a specific event module or rely on it.
699 836
… …
750 variable somewhere, waiting for it, and sending it when the program 887 variable somewhere, waiting for it, and sending it when the program
751 should exit cleanly. 888 should exit cleanly.
752 889
753OTHER MODULES 890OTHER MODULES
754 The following is a non-exhaustive list of additional modules that use 891 The following is a non-exhaustive list of additional modules that use
755 AnyEvent and can therefore be mixed easily with other AnyEvent modules 892 AnyEvent as a client and can therefore be mixed easily with other
756 in the same program. Some of the modules come with AnyEvent, some are 893 AnyEvent modules and other event loops in the same program. Some of the
757 available via CPAN. 894 modules come with AnyEvent, most are available via CPAN.
758 895
759 AnyEvent::Util 896 AnyEvent::Util
760 Contains various utility functions that replace often-used but 897 Contains various utility functions that replace often-used but
761 blocking functions such as "inet_aton" by event-/callback-based 898 blocking functions such as "inet_aton" by event-/callback-based
762 versions. 899 versions.
… …
768 more. 905 more.
769 906
770 AnyEvent::Handle 907 AnyEvent::Handle
771 Provide read and write buffers, manages watchers for reads and 908 Provide read and write buffers, manages watchers for reads and
772 writes, supports raw and formatted I/O, I/O queued and fully 909 writes, supports raw and formatted I/O, I/O queued and fully
773 transparent and non-blocking SSL/TLS. 910 transparent and non-blocking SSL/TLS (via AnyEvent::TLS.
774 911
775 AnyEvent::DNS 912 AnyEvent::DNS
776 Provides rich asynchronous DNS resolver capabilities. 913 Provides rich asynchronous DNS resolver capabilities.
777 914
778 AnyEvent::HTTP 915 AnyEvent::HTTP
… …
799 936
800 AnyEvent::GPSD 937 AnyEvent::GPSD
801 A non-blocking interface to gpsd, a daemon delivering GPS 938 A non-blocking interface to gpsd, a daemon delivering GPS
802 information. 939 information.
803 940
941 AnyEvent::IRC
942 AnyEvent based IRC client module family (replacing the older
943 Net::IRC3).
944
945 AnyEvent::XMPP
946 AnyEvent based XMPP (Jabber protocol) module family (replacing the
947 older Net::XMPP2>.
948
804 AnyEvent::IGS 949 AnyEvent::IGS
805 A non-blocking interface to the Internet Go Server protocol (used by 950 A non-blocking interface to the Internet Go Server protocol (used by
806 App::IGS). 951 App::IGS).
807 952
808 AnyEvent::IRC
809 AnyEvent based IRC client module family (replacing the older
810 Net::IRC3).
811
812 Net::XMPP2
813 AnyEvent based XMPP (Jabber protocol) module family.
814
815 Net::FCP 953 Net::FCP
816 AnyEvent-based implementation of the Freenet Client Protocol, 954 AnyEvent-based implementation of the Freenet Client Protocol,
817 birthplace of AnyEvent. 955 birthplace of AnyEvent.
818 956
819 Event::ExecFlow 957 Event::ExecFlow
820 High level API for event-based execution flow control. 958 High level API for event-based execution flow control.
821 959
822 Coro 960 Coro
823 Has special support for AnyEvent via Coro::AnyEvent. 961 Has special support for AnyEvent via Coro::AnyEvent.
824
825 IO::Lambda
826 The lambda approach to I/O - don't ask, look there. Can use
827 AnyEvent.
828 962
829ERROR AND EXCEPTION HANDLING 963ERROR AND EXCEPTION HANDLING
830 In general, AnyEvent does not do any error handling - it relies on the 964 In general, AnyEvent does not do any error handling - it relies on the
831 caller to do that if required. The AnyEvent::Strict module (see also the 965 caller to do that if required. The AnyEvent::Strict module (see also the
832 "PERL_ANYEVENT_STRICT" environment variable, below) provides strict 966 "PERL_ANYEVENT_STRICT" environment variable, below) provides strict
… …
842 "condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()", 976 "condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()",
843 Glib uses "install_exception_handler" and so on. 977 Glib uses "install_exception_handler" and so on.
844 978
845ENVIRONMENT VARIABLES 979ENVIRONMENT VARIABLES
846 The following environment variables are used by this module or its 980 The following environment variables are used by this module or its
847 submodules: 981 submodules.
982
983 Note that AnyEvent will remove *all* environment variables starting with
984 "PERL_ANYEVENT_" from %ENV when it is loaded while taint mode is
985 enabled.
848 986
849 "PERL_ANYEVENT_VERBOSE" 987 "PERL_ANYEVENT_VERBOSE"
850 By default, AnyEvent will be completely silent except in fatal 988 By default, AnyEvent will be completely silent except in fatal
851 conditions. You can set this environment variable to make AnyEvent 989 conditions. You can set this environment variable to make AnyEvent
852 more talkative. 990 more talkative.
… …
861 "PERL_ANYEVENT_STRICT" 999 "PERL_ANYEVENT_STRICT"
862 AnyEvent does not do much argument checking by default, as thorough 1000 AnyEvent does not do much argument checking by default, as thorough
863 argument checking is very costly. Setting this variable to a true 1001 argument checking is very costly. Setting this variable to a true
864 value will cause AnyEvent to load "AnyEvent::Strict" and then to 1002 value will cause AnyEvent to load "AnyEvent::Strict" and then to
865 thoroughly check the arguments passed to most method calls. If it 1003 thoroughly check the arguments passed to most method calls. If it
866 finds any problems it will croak. 1004 finds any problems, it will croak.
867 1005
868 In other words, enables "strict" mode. 1006 In other words, enables "strict" mode.
869 1007
870 Unlike "use strict", it is definitely recommended ot keep it off in 1008 Unlike "use strict", it is definitely recommended to keep it off in
871 production. Keeping "PERL_ANYEVENT_STRICT=1" in your environment 1009 production. Keeping "PERL_ANYEVENT_STRICT=1" in your environment
872 while developing programs can be very useful, however. 1010 while developing programs can be very useful, however.
873 1011
874 "PERL_ANYEVENT_MODEL" 1012 "PERL_ANYEVENT_MODEL"
875 This can be used to specify the event model to be used by AnyEvent, 1013 This can be used to specify the event model to be used by AnyEvent,
… …
918 EDNS0 in its DNS requests. 1056 EDNS0 in its DNS requests.
919 1057
920 "PERL_ANYEVENT_MAX_FORKS" 1058 "PERL_ANYEVENT_MAX_FORKS"
921 The maximum number of child processes that 1059 The maximum number of child processes that
922 "AnyEvent::Util::fork_call" will create in parallel. 1060 "AnyEvent::Util::fork_call" will create in parallel.
1061
1062 "PERL_ANYEVENT_MAX_OUTSTANDING_DNS"
1063 The default value for the "max_outstanding" parameter for the
1064 default DNS resolver - this is the maximum number of parallel DNS
1065 requests that are sent to the DNS server.
1066
1067 "PERL_ANYEVENT_RESOLV_CONF"
1068 The file to use instead of /etc/resolv.conf (or OS-specific
1069 configuration) in the default resolver. When set to the empty
1070 string, no default config will be used.
1071
1072 "PERL_ANYEVENT_CA_FILE", "PERL_ANYEVENT_CA_PATH".
1073 When neither "ca_file" nor "ca_path" was specified during
1074 AnyEvent::TLS context creation, and either of these environment
1075 variables exist, they will be used to specify CA certificate
1076 locations instead of a system-dependent default.
923 1077
924SUPPLYING YOUR OWN EVENT MODEL INTERFACE 1078SUPPLYING YOUR OWN EVENT MODEL INTERFACE
925 This is an advanced topic that you do not normally need to use AnyEvent 1079 This is an advanced topic that you do not normally need to use AnyEvent
926 in a module. This section is only of use to event loop authors who want 1080 in a module. This section is only of use to event loop authors who want
927 to provide AnyEvent compatibility. 1081 to provide AnyEvent compatibility.
… …
1163 EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers 1317 EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers
1164 CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal 1318 CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal
1165 Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation 1319 Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation
1166 Event/Event 16000 517 32.20 31.80 0.81 Event native interface 1320 Event/Event 16000 517 32.20 31.80 0.81 Event native interface
1167 Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers 1321 Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers
1322 IOAsync/Any 16000 989 38.10 32.77 11.13 via IO::Async::Loop::IO_Poll
1323 IOAsync/Any 16000 990 37.59 29.50 10.61 via IO::Async::Loop::Epoll
1168 Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour 1324 Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour
1169 Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers 1325 Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers
1170 POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event 1326 POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event
1171 POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select 1327 POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select
1172 1328
… …
1201 few of them active), of course, but this was not subject of this 1357 few of them active), of course, but this was not subject of this
1202 benchmark. 1358 benchmark.
1203 1359
1204 The "Event" module has a relatively high setup and callback invocation 1360 The "Event" module has a relatively high setup and callback invocation
1205 cost, but overall scores in on the third place. 1361 cost, but overall scores in on the third place.
1362
1363 "IO::Async" performs admirably well, about on par with "Event", even
1364 when using its pure perl backend.
1206 1365
1207 "Glib"'s memory usage is quite a bit higher, but it features a faster 1366 "Glib"'s memory usage is quite a bit higher, but it features a faster
1208 callback invocation and overall ends up in the same class as "Event". 1367 callback invocation and overall ends up in the same class as "Event".
1209 However, Glib scales extremely badly, doubling the number of watchers 1368 However, Glib scales extremely badly, doubling the number of watchers
1210 increases the processing time by more than a factor of four, making it 1369 increases the processing time by more than a factor of four, making it
… …
1281 single "request", that is, reading the token from the pipe and 1440 single "request", that is, reading the token from the pipe and
1282 forwarding it to another server. This includes deleting the old timeout 1441 forwarding it to another server. This includes deleting the old timeout
1283 and creating a new one that moves the timeout into the future. 1442 and creating a new one that moves the timeout into the future.
1284 1443
1285 Results 1444 Results
1286 name sockets create request 1445 name sockets create request
1287 EV 20000 69.01 11.16 1446 EV 20000 69.01 11.16
1288 Perl 20000 73.32 35.87 1447 Perl 20000 73.32 35.87
1448 IOAsync 20000 157.00 98.14 epoll
1449 IOAsync 20000 159.31 616.06 poll
1289 Event 20000 212.62 257.32 1450 Event 20000 212.62 257.32
1290 Glib 20000 651.16 1896.30 1451 Glib 20000 651.16 1896.30
1291 POE 20000 349.67 12317.24 uses POE::Loop::Event 1452 POE 20000 349.67 12317.24 uses POE::Loop::Event
1292 1453
1293 Discussion 1454 Discussion
1294 This benchmark *does* measure scalability and overall performance of the 1455 This benchmark *does* measure scalability and overall performance of the
1295 particular event loop. 1456 particular event loop.
1296 1457
1297 EV is again fastest. Since it is using epoll on my system, the setup 1458 EV is again fastest. Since it is using epoll on my system, the setup
1298 time is relatively high, though. 1459 time is relatively high, though.
1299 1460
1300 Perl surprisingly comes second. It is much faster than the C-based event 1461 Perl surprisingly comes second. It is much faster than the C-based event
1301 loops Event and Glib. 1462 loops Event and Glib.
1463
1464 IO::Async performs very well when using its epoll backend, and still
1465 quite good compared to Glib when using its pure perl backend.
1302 1466
1303 Event suffers from high setup time as well (look at its code and you 1467 Event suffers from high setup time as well (look at its code and you
1304 will understand why). Callback invocation also has a high overhead 1468 will understand why). Callback invocation also has a high overhead
1305 compared to the "$_->() for .."-style loop that the Perl event loop 1469 compared to the "$_->() for .."-style loop that the Perl event loop
1306 uses. Event uses select or poll in basically all documented 1470 uses. Event uses select or poll in basically all documented
… …
1357 1521
1358 Summary 1522 Summary
1359 * C-based event loops perform very well with small number of watchers, 1523 * C-based event loops perform very well with small number of watchers,
1360 as the management overhead dominates. 1524 as the management overhead dominates.
1361 1525
1526 THE IO::Lambda BENCHMARK
1527 Recently I was told about the benchmark in the IO::Lambda manpage, which
1528 could be misinterpreted to make AnyEvent look bad. In fact, the
1529 benchmark simply compares IO::Lambda with POE, and IO::Lambda looks
1530 better (which shouldn't come as a surprise to anybody). As such, the
1531 benchmark is fine, and mostly shows that the AnyEvent backend from
1532 IO::Lambda isn't very optimal. But how would AnyEvent compare when used
1533 without the extra baggage? To explore this, I wrote the equivalent
1534 benchmark for AnyEvent.
1535
1536 The benchmark itself creates an echo-server, and then, for 500 times,
1537 connects to the echo server, sends a line, waits for the reply, and then
1538 creates the next connection. This is a rather bad benchmark, as it
1539 doesn't test the efficiency of the framework or much non-blocking I/O,
1540 but it is a benchmark nevertheless.
1541
1542 name runtime
1543 Lambda/select 0.330 sec
1544 + optimized 0.122 sec
1545 Lambda/AnyEvent 0.327 sec
1546 + optimized 0.138 sec
1547 Raw sockets/select 0.077 sec
1548 POE/select, components 0.662 sec
1549 POE/select, raw sockets 0.226 sec
1550 POE/select, optimized 0.404 sec
1551
1552 AnyEvent/select/nb 0.085 sec
1553 AnyEvent/EV/nb 0.068 sec
1554 +state machine 0.134 sec
1555
1556 The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
1557 benchmarks actually make blocking connects and use 100% blocking I/O,
1558 defeating the purpose of an event-based solution. All of the newly
1559 written AnyEvent benchmarks use 100% non-blocking connects (using
1560 AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
1561 resolver), so AnyEvent is at a disadvantage here, as non-blocking
1562 connects generally require a lot more bookkeeping and event handling
1563 than blocking connects (which involve a single syscall only).
1564
1565 The last AnyEvent benchmark additionally uses AnyEvent::Handle, which
1566 offers similar expressive power as POE and IO::Lambda, using
1567 conventional Perl syntax. This means that both the echo server and the
1568 client are 100% non-blocking, further placing it at a disadvantage.
1569
1570 As you can see, the AnyEvent + EV combination even beats the
1571 hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
1572 backend easily beats IO::Lambda and POE.
1573
1574 And even the 100% non-blocking version written using the high-level (and
1575 slow :) AnyEvent::Handle abstraction beats both POE and IO::Lambda by a
1576 large margin, even though it does all of DNS, tcp-connect and socket I/O
1577 in a non-blocking way.
1578
1579 The two AnyEvent benchmarks programs can be found as eg/ae0.pl and
1580 eg/ae2.pl in the AnyEvent distribution, the remaining benchmarks are
1581 part of the IO::lambda distribution and were used without any changes.
1582
1362SIGNALS 1583SIGNALS
1363 AnyEvent currently installs handlers for these signals: 1584 AnyEvent currently installs handlers for these signals:
1364 1585
1365 SIGCHLD 1586 SIGCHLD
1366 A handler for "SIGCHLD" is installed by AnyEvent's child watcher 1587 A handler for "SIGCHLD" is installed by AnyEvent's child watcher
1367 emulation for event loops that do not support them natively. Also, 1588 emulation for event loops that do not support them natively. Also,
1368 some event loops install a similar handler. 1589 some event loops install a similar handler.
1590
1591 If, when AnyEvent is loaded, SIGCHLD is set to IGNORE, then AnyEvent
1592 will reset it to default, to avoid losing child exit statuses.
1369 1593
1370 SIGPIPE 1594 SIGPIPE
1371 A no-op handler is installed for "SIGPIPE" when $SIG{PIPE} is 1595 A no-op handler is installed for "SIGPIPE" when $SIG{PIPE} is
1372 "undef" when AnyEvent gets loaded. 1596 "undef" when AnyEvent gets loaded.
1373 1597
… …
1401 1625
1402 You can make AnyEvent completely ignore this variable by deleting it 1626 You can make AnyEvent completely ignore this variable by deleting it
1403 before the first watcher gets created, e.g. with a "BEGIN" block: 1627 before the first watcher gets created, e.g. with a "BEGIN" block:
1404 1628
1405 BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} } 1629 BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1406 1630
1407 use AnyEvent; 1631 use AnyEvent;
1408 1632
1409 Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can 1633 Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
1410 be used to probe what backend is used and gain other information (which 1634 be used to probe what backend is used and gain other information (which
1411 is probably even less useful to an attacker than PERL_ANYEVENT_MODEL), 1635 is probably even less useful to an attacker than PERL_ANYEVENT_MODEL),
1412 and $ENV{PERL_ANYEGENT_STRICT}. 1636 and $ENV{PERL_ANYEVENT_STRICT}.
1637
1638 Note that AnyEvent will remove *all* environment variables starting with
1639 "PERL_ANYEVENT_" from %ENV when it is loaded while taint mode is
1640 enabled.
1413 1641
1414BUGS 1642BUGS
1415 Perl 5.8 has numerous memleaks that sometimes hit this module and are 1643 Perl 5.8 has numerous memleaks that sometimes hit this module and are
1416 hard to work around. If you suffer from memleaks, first upgrade to Perl 1644 hard to work around. If you suffer from memleaks, first upgrade to Perl
1417 5.10 and check wether the leaks still show up. (Perl 5.10.0 has other 1645 5.10 and check wether the leaks still show up. (Perl 5.10.0 has other
… …
1424 Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk, 1652 Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk,
1425 Event::Lib, Qt, POE. 1653 Event::Lib, Qt, POE.
1426 1654
1427 Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event, 1655 Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,
1428 AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl, 1656 AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,
1429 AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE. 1657 AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE,
1658 AnyEvent::Impl::IOAsync.
1430 1659
1431 Non-blocking file handles, sockets, TCP clients and servers: 1660 Non-blocking file handles, sockets, TCP clients and servers:
1432 AnyEvent::Handle, AnyEvent::Socket. 1661 AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS.
1433 1662
1434 Asynchronous DNS: AnyEvent::DNS. 1663 Asynchronous DNS: AnyEvent::DNS.
1435 1664
1436 Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event, 1665 Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,
1437 1666
1438 Nontrivial usage examples: Net::FCP, Net::XMPP2, AnyEvent::DNS. 1667 Nontrivial usage examples: AnyEvent::GPSD, AnyEvent::XMPP,
1668 AnyEvent::HTTP.
1439 1669
1440AUTHOR 1670AUTHOR
1441 Marc Lehmann <schmorp@schmorp.de> 1671 Marc Lehmann <schmorp@schmorp.de>
1442 http://home.schmorp.de/ 1672 http://home.schmorp.de/
1443 1673

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