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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.
… …
314 In either case, if you care (and in most cases, you don't), then you 321 In either case, if you care (and in most cases, you don't), then you
315 can get whatever behaviour you want with any event loop, by taking 322 can get whatever behaviour you want with any event loop, by taking
316 the difference between "AnyEvent->time" and "AnyEvent->now" into 323 the difference between "AnyEvent->time" and "AnyEvent->now" into
317 account. 324 account.
318 325
326 AnyEvent->now_update
327 Some event loops (such as EV or AnyEvent::Impl::Perl) cache the
328 current time for each loop iteration (see the discussion of
329 AnyEvent->now, above).
330
331 When a callback runs for a long time (or when the process sleeps),
332 then this "current" time will differ substantially from the real
333 time, which might affect timers and time-outs.
334
335 When this is the case, you can call this method, which will update
336 the event loop's idea of "current time".
337
338 Note that updating the time *might* cause some events to be handled.
339
319 SIGNAL WATCHERS 340 SIGNAL WATCHERS
320 You can watch for signals using a signal watcher, "signal" is the signal 341 You can watch for signals using a signal watcher, "signal" is the signal
321 *name* in uppercase and without any "SIG" prefix, "cb" is the Perl 342 *name* in uppercase and without any "SIG" prefix, "cb" is the Perl
322 callback to be invoked whenever a signal occurs. 343 callback to be invoked whenever a signal occurs.
323 344
… …
359 380
360 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
361 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
362 could have exited already (and no SIGCHLD will be sent anymore). 383 could have exited already (and no SIGCHLD will be sent anymore).
363 384
364 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
365 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
366 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).
367 place). 389 AnyEvent's pure perl event loop handles all cases correctly regardless
390 of when you start the watcher.
368 391
369 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
370 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
371 you "fork" the child (alternatively, you can call "AnyEvent::detect"). 394 you "fork" the child (alternatively, you can call "AnyEvent::detect").
372 395
373 Example: fork a process and wait for it 396 Example: fork a process and wait for it
374 397
375 my $done = AnyEvent->condvar; 398 my $done = AnyEvent->condvar;
376 399
377 my $pid = fork or exit 5; 400 my $pid = fork or exit 5;
378 401
379 my $w = AnyEvent->child ( 402 my $w = AnyEvent->child (
380 pid => $pid, 403 pid => $pid,
381 cb => sub { 404 cb => sub {
382 my ($pid, $status) = @_; 405 my ($pid, $status) = @_;
383 warn "pid $pid exited with status $status"; 406 warn "pid $pid exited with status $status";
384 $done->send; 407 $done->send;
385 }, 408 },
386 ); 409 );
387 410
388 # do something else, then wait for process exit 411 # do something else, then wait for process exit
389 $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 });
390 447
391 CONDITION VARIABLES 448 CONDITION VARIABLES
392 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
393 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
394 will actively watch for new events and call your callbacks. 451 will actively watch for new events and call your callbacks.
… …
520 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
521 user/consumer. 578 user/consumer.
522 579
523 $cv->begin ([group callback]) 580 $cv->begin ([group callback])
524 $cv->end 581 $cv->end
525 These two methods are EXPERIMENTAL and MIGHT CHANGE.
526
527 These two methods can be used to combine many transactions/events 582 These two methods can be used to combine many transactions/events
528 into one. For example, a function that pings many hosts in parallel 583 into one. For example, a function that pings many hosts in parallel
529 might want to use a condition variable for the whole process. 584 might want to use a condition variable for the whole process.
530 585
531 Every call to "->begin" will increment a counter, and every call to 586 Every call to "->begin" will increment a counter, and every call to
532 "->end" will decrement it. If the counter reaches 0 in "->end", the 587 "->end" will decrement it. If the counter reaches 0 in "->end", the
533 (last) callback passed to "begin" will be executed. That callback is 588 (last) callback passed to "begin" will be executed. That callback is
534 *supposed* to call "->send", but that is not required. If no 589 *supposed* to call "->send", but that is not required. If no
535 callback was set, "send" will be called without any arguments. 590 callback was set, "send" will be called without any arguments.
536 591
537 Let's clarify this with the ping example: 592 You can think of "$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:
538 624
539 my $cv = AnyEvent->condvar; 625 my $cv = AnyEvent->condvar;
540 626
541 my %result; 627 my %result;
542 $cv->begin (sub { $cv->send (\%result) }); 628 $cv->begin (sub { $cv->send (\%result) });
… …
562 the loop, which serves two important purposes: first, it sets the 648 the loop, which serves two important purposes: first, it sets the
563 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
564 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
565 (the loop doesn't execute once). 651 (the loop doesn't execute once).
566 652
567 This is the general pattern when you "fan out" into multiple 653 This is the general pattern when you "fan out" into multiple (but
568 subrequests: use an outer "begin"/"end" pair to set the callback and 654 potentially none) subrequests: use an outer "begin"/"end" pair to
569 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,
570 you start, call "begin" and for each subrequest you finish, call 656 for each subrequest you start, call "begin" and for each subrequest
571 "end". 657 you finish, call "end".
572 658
573 METHODS FOR CONSUMERS 659 METHODS FOR CONSUMERS
574 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
575 awaits the condition. 661 awaits the condition.
576 662
… …
623 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.
624 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
625 condition variable itself. Calling "recv" inside the callback or at 711 condition variable itself. Calling "recv" inside the callback or at
626 any later time is guaranteed not to block. 712 any later time is guaranteed not to block.
627 713
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
628GLOBAL 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
629 $AnyEvent::MODEL 777 $AnyEvent::MODEL
630 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
631 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
632 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
633 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
634 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.
635 785 in *rxvt-unicode* it will be "urxvt::anyevent").
636 The known classes so far are:
637
638 AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
639 AnyEvent::Impl::Event based on Event, second best choice.
640 AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
641 AnyEvent::Impl::Glib based on Glib, third-best choice.
642 AnyEvent::Impl::Tk based on Tk, very bad choice.
643 AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
644 AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
645 AnyEvent::Impl::POE based on POE, not generic enough for full support.
646
647 There is no support for WxWidgets, as WxWidgets has no support for
648 watching file handles. However, you can use WxWidgets through the
649 POE Adaptor, as POE has a Wx backend that simply polls 20 times per
650 second, which was considered to be too horrible to even consider for
651 AnyEvent. Likewise, other POE backends can be used by AnyEvent by
652 using it's adaptor.
653
654 AnyEvent knows about Prima and Wx and will try to use POE when
655 autodetecting them.
656 786
657 AnyEvent::detect 787 AnyEvent::detect
658 Returns $AnyEvent::MODEL, forcing autodetection of the event model 788 Returns $AnyEvent::MODEL, forcing autodetection of the event model
659 if necessary. You should only call this function right before you 789 if necessary. You should only call this function right before you
660 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
661 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".
662 795
663 $guard = AnyEvent::post_detect { BLOCK } 796 $guard = AnyEvent::post_detect { BLOCK }
664 Arranges for the code block to be executed as soon as the event 797 Arranges for the code block to be executed as soon as the event
665 model is autodetected (or immediately if this has already happened). 798 model is autodetected (or immediately if this has already happened).
799
800 The block will be executed *after* the actual backend has been
801 detected ($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.
666 810
667 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
668 object that automatically removes the callback again when it is 812 object that automatically removes the callback again when it is
669 destroyed. See Coro::BDB for a case where this is useful. 813 destroyed. See Coro::BDB for a case where this is useful.
670 814
… …
672 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
673 before or after loading AnyEvent), then they will called directly 817 before or after loading AnyEvent), then they will called directly
674 after the event loop has been chosen. 818 after the event loop has been chosen.
675 819
676 You should check $AnyEvent::MODEL before adding to this array, 820 You should check $AnyEvent::MODEL before adding to this array,
677 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
678 been detected, and the array will be ignored. 822 detected, and the array will be ignored.
679 823
680 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.
681 832
682WHAT TO DO IN A MODULE 833WHAT TO DO IN A MODULE
683 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
684 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.
685 836
… …
736 variable somewhere, waiting for it, and sending it when the program 887 variable somewhere, waiting for it, and sending it when the program
737 should exit cleanly. 888 should exit cleanly.
738 889
739OTHER MODULES 890OTHER MODULES
740 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
741 AnyEvent and can therefore be mixed easily with other AnyEvent modules 892 AnyEvent as a client and can therefore be mixed easily with other
742 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
743 available via CPAN. 894 modules come with AnyEvent, most are available via CPAN.
744 895
745 AnyEvent::Util 896 AnyEvent::Util
746 Contains various utility functions that replace often-used but 897 Contains various utility functions that replace often-used but
747 blocking functions such as "inet_aton" by event-/callback-based 898 blocking functions such as "inet_aton" by event-/callback-based
748 versions. 899 versions.
… …
754 more. 905 more.
755 906
756 AnyEvent::Handle 907 AnyEvent::Handle
757 Provide read and write buffers, manages watchers for reads and 908 Provide read and write buffers, manages watchers for reads and
758 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
759 transparent and non-blocking SSL/TLS. 910 transparent and non-blocking SSL/TLS (via AnyEvent::TLS.
760 911
761 AnyEvent::DNS 912 AnyEvent::DNS
762 Provides rich asynchronous DNS resolver capabilities. 913 Provides rich asynchronous DNS resolver capabilities.
763 914
764 AnyEvent::HTTP 915 AnyEvent::HTTP
… …
785 936
786 AnyEvent::GPSD 937 AnyEvent::GPSD
787 A non-blocking interface to gpsd, a daemon delivering GPS 938 A non-blocking interface to gpsd, a daemon delivering GPS
788 information. 939 information.
789 940
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
790 AnyEvent::IGS 949 AnyEvent::IGS
791 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
792 App::IGS). 951 App::IGS).
793 952
794 AnyEvent::IRC
795 AnyEvent based IRC client module family (replacing the older
796 Net::IRC3).
797
798 Net::XMPP2
799 AnyEvent based XMPP (Jabber protocol) module family.
800
801 Net::FCP 953 Net::FCP
802 AnyEvent-based implementation of the Freenet Client Protocol, 954 AnyEvent-based implementation of the Freenet Client Protocol,
803 birthplace of AnyEvent. 955 birthplace of AnyEvent.
804 956
805 Event::ExecFlow 957 Event::ExecFlow
806 High level API for event-based execution flow control. 958 High level API for event-based execution flow control.
807 959
808 Coro 960 Coro
809 Has special support for AnyEvent via Coro::AnyEvent. 961 Has special support for AnyEvent via Coro::AnyEvent.
810
811 IO::Lambda
812 The lambda approach to I/O - don't ask, look there. Can use
813 AnyEvent.
814 962
815ERROR AND EXCEPTION HANDLING 963ERROR AND EXCEPTION HANDLING
816 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
817 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
818 "PERL_ANYEVENT_STRICT" environment variable, below) provides strict 966 "PERL_ANYEVENT_STRICT" environment variable, below) provides strict
… …
828 "condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()", 976 "condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()",
829 Glib uses "install_exception_handler" and so on. 977 Glib uses "install_exception_handler" and so on.
830 978
831ENVIRONMENT VARIABLES 979ENVIRONMENT VARIABLES
832 The following environment variables are used by this module or its 980 The following environment variables are used by this module or its
833 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.
834 986
835 "PERL_ANYEVENT_VERBOSE" 987 "PERL_ANYEVENT_VERBOSE"
836 By default, AnyEvent will be completely silent except in fatal 988 By default, AnyEvent will be completely silent except in fatal
837 conditions. You can set this environment variable to make AnyEvent 989 conditions. You can set this environment variable to make AnyEvent
838 more talkative. 990 more talkative.
… …
847 "PERL_ANYEVENT_STRICT" 999 "PERL_ANYEVENT_STRICT"
848 AnyEvent does not do much argument checking by default, as thorough 1000 AnyEvent does not do much argument checking by default, as thorough
849 argument checking is very costly. Setting this variable to a true 1001 argument checking is very costly. Setting this variable to a true
850 value will cause AnyEvent to load "AnyEvent::Strict" and then to 1002 value will cause AnyEvent to load "AnyEvent::Strict" and then to
851 thoroughly check the arguments passed to most method calls. If it 1003 thoroughly check the arguments passed to most method calls. If it
852 finds any problems it will croak. 1004 finds any problems, it will croak.
853 1005
854 In other words, enables "strict" mode. 1006 In other words, enables "strict" mode.
855 1007
856 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
857 production. Keeping "PERL_ANYEVENT_STRICT=1" in your environment 1009 production. Keeping "PERL_ANYEVENT_STRICT=1" in your environment
858 while developing programs can be very useful, however. 1010 while developing programs can be very useful, however.
859 1011
860 "PERL_ANYEVENT_MODEL" 1012 "PERL_ANYEVENT_MODEL"
861 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,
… …
904 EDNS0 in its DNS requests. 1056 EDNS0 in its DNS requests.
905 1057
906 "PERL_ANYEVENT_MAX_FORKS" 1058 "PERL_ANYEVENT_MAX_FORKS"
907 The maximum number of child processes that 1059 The maximum number of child processes that
908 "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.
909 1077
910SUPPLYING YOUR OWN EVENT MODEL INTERFACE 1078SUPPLYING YOUR OWN EVENT MODEL INTERFACE
911 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
912 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
913 to provide AnyEvent compatibility. 1081 to provide AnyEvent compatibility.
… …
1149 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
1150 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
1151 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
1152 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
1153 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
1154 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
1155 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
1156 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
1157 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
1158 1328
… …
1187 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
1188 benchmark. 1358 benchmark.
1189 1359
1190 The "Event" module has a relatively high setup and callback invocation 1360 The "Event" module has a relatively high setup and callback invocation
1191 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.
1192 1365
1193 "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
1194 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".
1195 However, Glib scales extremely badly, doubling the number of watchers 1368 However, Glib scales extremely badly, doubling the number of watchers
1196 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
… …
1267 single "request", that is, reading the token from the pipe and 1440 single "request", that is, reading the token from the pipe and
1268 forwarding it to another server. This includes deleting the old timeout 1441 forwarding it to another server. This includes deleting the old timeout
1269 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.
1270 1443
1271 Results 1444 Results
1272 name sockets create request 1445 name sockets create request
1273 EV 20000 69.01 11.16 1446 EV 20000 69.01 11.16
1274 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
1275 Event 20000 212.62 257.32 1450 Event 20000 212.62 257.32
1276 Glib 20000 651.16 1896.30 1451 Glib 20000 651.16 1896.30
1277 POE 20000 349.67 12317.24 uses POE::Loop::Event 1452 POE 20000 349.67 12317.24 uses POE::Loop::Event
1278 1453
1279 Discussion 1454 Discussion
1280 This benchmark *does* measure scalability and overall performance of the 1455 This benchmark *does* measure scalability and overall performance of the
1281 particular event loop. 1456 particular event loop.
1282 1457
1283 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
1284 time is relatively high, though. 1459 time is relatively high, though.
1285 1460
1286 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
1287 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.
1288 1466
1289 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
1290 will understand why). Callback invocation also has a high overhead 1468 will understand why). Callback invocation also has a high overhead
1291 compared to the "$_->() for .."-style loop that the Perl event loop 1469 compared to the "$_->() for .."-style loop that the Perl event loop
1292 uses. Event uses select or poll in basically all documented 1470 uses. Event uses select or poll in basically all documented
… …
1343 1521
1344 Summary 1522 Summary
1345 * 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,
1346 as the management overhead dominates. 1524 as the management overhead dominates.
1347 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
1348SIGNALS 1583SIGNALS
1349 AnyEvent currently installs handlers for these signals: 1584 AnyEvent currently installs handlers for these signals:
1350 1585
1351 SIGCHLD 1586 SIGCHLD
1352 A handler for "SIGCHLD" is installed by AnyEvent's child watcher 1587 A handler for "SIGCHLD" is installed by AnyEvent's child watcher
1353 emulation for event loops that do not support them natively. Also, 1588 emulation for event loops that do not support them natively. Also,
1354 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.
1355 1593
1356 SIGPIPE 1594 SIGPIPE
1357 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
1358 "undef" when AnyEvent gets loaded. 1596 "undef" when AnyEvent gets loaded.
1359 1597
… …
1387 1625
1388 You can make AnyEvent completely ignore this variable by deleting it 1626 You can make AnyEvent completely ignore this variable by deleting it
1389 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:
1390 1628
1391 BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} } 1629 BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1392 1630
1393 use AnyEvent; 1631 use AnyEvent;
1394 1632
1395 Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can 1633 Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
1396 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
1397 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),
1398 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.
1399 1641
1400BUGS 1642BUGS
1401 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
1402 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
1403 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
… …
1410 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,
1411 Event::Lib, Qt, POE. 1653 Event::Lib, Qt, POE.
1412 1654
1413 Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event, 1655 Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,
1414 AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl, 1656 AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,
1415 AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE. 1657 AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE,
1658 AnyEvent::Impl::IOAsync.
1416 1659
1417 Non-blocking file handles, sockets, TCP clients and servers: 1660 Non-blocking file handles, sockets, TCP clients and servers:
1418 AnyEvent::Handle, AnyEvent::Socket. 1661 AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS.
1419 1662
1420 Asynchronous DNS: AnyEvent::DNS. 1663 Asynchronous DNS: AnyEvent::DNS.
1421 1664
1422 Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event, 1665 Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,
1423 1666
1424 Nontrivial usage examples: Net::FCP, Net::XMPP2, AnyEvent::DNS. 1667 Nontrivial usage examples: AnyEvent::GPSD, AnyEvent::XMPP,
1668 AnyEvent::HTTP.
1425 1669
1426AUTHOR 1670AUTHOR
1427 Marc Lehmann <schmorp@schmorp.de> 1671 Marc Lehmann <schmorp@schmorp.de>
1428 http://home.schmorp.de/ 1672 http://home.schmorp.de/
1429 1673

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