1 | NAME |
1 | NAME |
2 | AnyEvent - provide framework for multiple event loops |
2 | AnyEvent - the DBI of event loop programming |
3 | |
3 | |
4 | EV, Event, Glib, Tk, Perl, Event::Lib, Qt and POE are various supported |
4 | EV, Event, Glib, Tk, Perl, Event::Lib, Irssi, IO::Async, Qt and POE are |
5 | event loops. |
5 | various supported event loops/environments. |
6 | |
6 | |
7 | SYNOPSIS |
7 | SYNOPSIS |
8 | use AnyEvent; |
8 | use AnyEvent; |
9 | |
9 | |
10 | # file descriptor readable |
10 | # file descriptor readable |
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37 | |
37 | |
38 | INTRODUCTION/TUTORIAL |
38 | INTRODUCTION/TUTORIAL |
39 | This manpage is mainly a reference manual. If you are interested in a |
39 | This manpage is mainly a reference manual. If you are interested in a |
40 | tutorial or some gentle introduction, have a look at the AnyEvent::Intro |
40 | tutorial or some gentle introduction, have a look at the AnyEvent::Intro |
41 | manpage. |
41 | manpage. |
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42 | |
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43 | SUPPORT |
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44 | There is a mailinglist for discussing all things AnyEvent, and an IRC |
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45 | channel, too. |
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46 | |
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47 | See the AnyEvent project page at the Schmorpforge Ta-Sa Software |
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48 | Repository, at <http://anyevent.schmorp.de>, for more info. |
42 | |
49 | |
43 | WHY YOU SHOULD USE THIS MODULE (OR NOT) |
50 | WHY YOU SHOULD USE THIS MODULE (OR NOT) |
44 | Glib, POE, IO::Async, Event... CPAN offers event models by the dozen |
51 | Glib, POE, IO::Async, Event... CPAN offers event models by the dozen |
45 | nowadays. So what is different about AnyEvent? |
52 | nowadays. So what is different about AnyEvent? |
46 | |
53 | |
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350 | invocation, and callback invocation will be synchronous. Synchronous |
357 | invocation, and callback invocation will be synchronous. Synchronous |
351 | means that it might take a while until the signal gets handled by the |
358 | means that it might take a while until the signal gets handled by the |
352 | process, but it is guaranteed not to interrupt any other callbacks. |
359 | process, but it is guaranteed not to interrupt any other callbacks. |
353 | |
360 | |
354 | The main advantage of using these watchers is that you can share a |
361 | The main advantage of using these watchers is that you can share a |
355 | signal between multiple watchers. |
362 | signal between multiple watchers, and AnyEvent will ensure that signals |
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363 | will not interrupt your program at bad times. |
356 | |
364 | |
357 | This watcher might use %SIG, so programs overwriting those signals |
365 | This watcher might use %SIG (depending on the event loop used), so |
358 | directly will likely not work correctly. |
366 | programs overwriting those signals directly will likely not work |
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367 | correctly. |
359 | |
368 | |
360 | Example: exit on SIGINT |
369 | Example: exit on SIGINT |
361 | |
370 | |
362 | my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 }); |
371 | my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 }); |
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372 | |
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373 | Signal Races, Delays and Workarounds |
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374 | Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching |
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375 | callbacks to signals in a generic way, which is a pity, as you cannot do |
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376 | race-free signal handling in perl. AnyEvent will try to do it's best, |
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377 | but in some cases, signals will be delayed. The maximum time a signal |
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378 | might be delayed is specified in $AnyEvent::MAX_SIGNAL_LATENCY (default: |
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379 | 10 seconds). This variable can be changed only before the first signal |
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380 | watcher is created, and should be left alone otherwise. Higher values |
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381 | will cause fewer spurious wake-ups, which is better for power and CPU |
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382 | saving. All these problems can be avoided by installing the optional |
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383 | Async::Interrupt module. This will not work with inherently broken event |
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384 | loops such as Event or Event::Lib (and not with POE currently, as POE |
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385 | does it's own workaround with one-second latency). With those, you just |
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386 | have to suffer the delays. |
363 | |
387 | |
364 | CHILD PROCESS WATCHERS |
388 | CHILD PROCESS WATCHERS |
365 | You can also watch on a child process exit and catch its exit status. |
389 | You can also watch on a child process exit and catch its exit status. |
366 | |
390 | |
367 | The child process is specified by the "pid" argument (if set to 0, it |
391 | The child process is specified by the "pid" argument (one some backends, |
368 | watches for any child process exit). The watcher will triggered only |
392 | using 0 watches for any child process exit, on others this will croak). |
369 | when the child process has finished and an exit status is available, not |
393 | The watcher will be triggered only when the child process has finished |
370 | on any trace events (stopped/continued). |
394 | and an exit status is available, not on any trace events |
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395 | (stopped/continued). |
371 | |
396 | |
372 | The callback will be called with the pid and exit status (as returned by |
397 | The callback will be called with the pid and exit status (as returned by |
373 | waitpid), so unlike other watcher types, you *can* rely on child watcher |
398 | waitpid), so unlike other watcher types, you *can* rely on child watcher |
374 | callback arguments. |
399 | callback arguments. |
375 | |
400 | |
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390 | of when you start the watcher. |
415 | of when you start the watcher. |
391 | |
416 | |
392 | This means you cannot create a child watcher as the very first thing in |
417 | This means you cannot create a child watcher as the very first thing in |
393 | an AnyEvent program, you *have* to create at least one watcher before |
418 | an AnyEvent program, you *have* to create at least one watcher before |
394 | you "fork" the child (alternatively, you can call "AnyEvent::detect"). |
419 | you "fork" the child (alternatively, you can call "AnyEvent::detect"). |
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420 | |
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421 | As most event loops do not support waiting for child events, they will |
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422 | be emulated by AnyEvent in most cases, in which the latency and race |
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423 | problems mentioned in the description of signal watchers apply. |
395 | |
424 | |
396 | Example: fork a process and wait for it |
425 | Example: fork a process and wait for it |
397 | |
426 | |
398 | my $done = AnyEvent->condvar; |
427 | my $done = AnyEvent->condvar; |
399 | |
428 | |
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473 | Condition variables are similar to callbacks, except that you can |
502 | Condition variables are similar to callbacks, except that you can |
474 | optionally wait for them. They can also be called merge points - points |
503 | optionally wait for them. They can also be called merge points - points |
475 | in time where multiple outstanding events have been processed. And yet |
504 | in time where multiple outstanding events have been processed. And yet |
476 | another way to call them is transactions - each condition variable can |
505 | another way to call them is transactions - each condition variable can |
477 | be used to represent a transaction, which finishes at some point and |
506 | be used to represent a transaction, which finishes at some point and |
478 | delivers a result. |
507 | delivers a result. And yet some people know them as "futures" - a |
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508 | promise to compute/deliver something that you can wait for. |
479 | |
509 | |
480 | Condition variables are very useful to signal that something has |
510 | Condition variables are very useful to signal that something has |
481 | finished, for example, if you write a module that does asynchronous http |
511 | finished, for example, if you write a module that does asynchronous http |
482 | requests, then a condition variable would be the ideal candidate to |
512 | requests, then a condition variable would be the ideal candidate to |
483 | signal the availability of results. The user can either act when the |
513 | signal the availability of results. The user can either act when the |
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731 | |
761 | |
732 | AnyEvent::Impl::Glib based on Glib, slow but very stable. |
762 | AnyEvent::Impl::Glib based on Glib, slow but very stable. |
733 | AnyEvent::Impl::Tk based on Tk, very broken. |
763 | AnyEvent::Impl::Tk based on Tk, very broken. |
734 | AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse. |
764 | AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse. |
735 | AnyEvent::Impl::POE based on POE, very slow, some limitations. |
765 | AnyEvent::Impl::POE based on POE, very slow, some limitations. |
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766 | AnyEvent::Impl::Irssi used when running within irssi. |
736 | |
767 | |
737 | Backends with special needs. |
768 | Backends with special needs. |
738 | Qt requires the Qt::Application to be instantiated first, but will |
769 | Qt requires the Qt::Application to be instantiated first, but will |
739 | otherwise be picked up automatically. As long as the main program |
770 | otherwise be picked up automatically. As long as the main program |
740 | instantiates the application before any AnyEvent watchers are |
771 | instantiates the application before any AnyEvent watchers are |
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805 | creates and installs the global IO::AIO watcher in a "post_detect" |
836 | creates and installs the global IO::AIO watcher in a "post_detect" |
806 | block to avoid autodetecting the event module at load time. |
837 | block to avoid autodetecting the event module at load time. |
807 | |
838 | |
808 | If called in scalar or list context, then it creates and returns an |
839 | If called in scalar or list context, then it creates and returns an |
809 | object that automatically removes the callback again when it is |
840 | object that automatically removes the callback again when it is |
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841 | destroyed (or "undef" when the hook was immediately executed). See |
810 | destroyed. See Coro::BDB for a case where this is useful. |
842 | AnyEvent::AIO for a case where this is useful. |
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843 | |
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844 | Example: Create a watcher for the IO::AIO module and store it in |
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845 | $WATCHER. Only do so after the event loop is initialised, though. |
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846 | |
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847 | our WATCHER; |
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848 | |
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849 | my $guard = AnyEvent::post_detect { |
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850 | $WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb); |
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851 | }; |
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852 | |
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853 | # the ||= is important in case post_detect immediately runs the block, |
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854 | # as to not clobber the newly-created watcher. assigning both watcher and |
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855 | # post_detect guard to the same variable has the advantage of users being |
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856 | # able to just C<undef $WATCHER> if the watcher causes them grief. |
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857 | |
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858 | $WATCHER ||= $guard; |
811 | |
859 | |
812 | @AnyEvent::post_detect |
860 | @AnyEvent::post_detect |
813 | If there are any code references in this array (you can "push" to it |
861 | If there are any code references in this array (you can "push" to it |
814 | before or after loading AnyEvent), then they will called directly |
862 | before or after loading AnyEvent), then they will called directly |
815 | after the event loop has been chosen. |
863 | after the event loop has been chosen. |
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991 | by "PERL_ANYEVENT_MODEL". |
1039 | by "PERL_ANYEVENT_MODEL". |
992 | |
1040 | |
993 | When set to 2 or higher, cause AnyEvent to report to STDERR which |
1041 | When set to 2 or higher, cause AnyEvent to report to STDERR which |
994 | event model it chooses. |
1042 | event model it chooses. |
995 | |
1043 | |
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1044 | When set to 8 or higher, then AnyEvent will report extra information |
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1045 | on which optional modules it loads and how it implements certain |
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1046 | features. |
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1047 | |
996 | "PERL_ANYEVENT_STRICT" |
1048 | "PERL_ANYEVENT_STRICT" |
997 | AnyEvent does not do much argument checking by default, as thorough |
1049 | AnyEvent does not do much argument checking by default, as thorough |
998 | argument checking is very costly. Setting this variable to a true |
1050 | argument checking is very costly. Setting this variable to a true |
999 | value will cause AnyEvent to load "AnyEvent::Strict" and then to |
1051 | value will cause AnyEvent to load "AnyEvent::Strict" and then to |
1000 | thoroughly check the arguments passed to most method calls. If it |
1052 | thoroughly check the arguments passed to most method calls. If it |
1001 | finds any problems, it will croak. |
1053 | finds any problems, it will croak. |
1002 | |
1054 | |
1003 | In other words, enables "strict" mode. |
1055 | In other words, enables "strict" mode. |
1004 | |
1056 | |
1005 | Unlike "use strict", it is definitely recommended to keep it off in |
1057 | Unlike "use strict" (or it's modern cousin, "use common::sense", it |
1006 | production. Keeping "PERL_ANYEVENT_STRICT=1" in your environment |
1058 | is definitely recommended to keep it off in production. Keeping |
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1059 | "PERL_ANYEVENT_STRICT=1" in your environment while developing |
1007 | while developing programs can be very useful, however. |
1060 | programs can be very useful, however. |
1008 | |
1061 | |
1009 | "PERL_ANYEVENT_MODEL" |
1062 | "PERL_ANYEVENT_MODEL" |
1010 | This can be used to specify the event model to be used by AnyEvent, |
1063 | This can be used to specify the event model to be used by AnyEvent, |
1011 | before auto detection and -probing kicks in. It must be a string |
1064 | before auto detection and -probing kicks in. It must be a string |
1012 | consisting entirely of ASCII letters. The string "AnyEvent::Impl::" |
1065 | consisting entirely of ASCII letters. The string "AnyEvent::Impl::" |
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1069 | "PERL_ANYEVENT_CA_FILE", "PERL_ANYEVENT_CA_PATH". |
1122 | "PERL_ANYEVENT_CA_FILE", "PERL_ANYEVENT_CA_PATH". |
1070 | When neither "ca_file" nor "ca_path" was specified during |
1123 | When neither "ca_file" nor "ca_path" was specified during |
1071 | AnyEvent::TLS context creation, and either of these environment |
1124 | AnyEvent::TLS context creation, and either of these environment |
1072 | variables exist, they will be used to specify CA certificate |
1125 | variables exist, they will be used to specify CA certificate |
1073 | locations instead of a system-dependent default. |
1126 | locations instead of a system-dependent default. |
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1127 | |
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1128 | "PERL_ANYEVENT_AVOID_GUARD" and "PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT" |
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1129 | When these are set to 1, then the respective modules are not loaded. |
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1130 | Mostly good for testing AnyEvent itself. |
1074 | |
1131 | |
1075 | SUPPLYING YOUR OWN EVENT MODEL INTERFACE |
1132 | SUPPLYING YOUR OWN EVENT MODEL INTERFACE |
1076 | This is an advanced topic that you do not normally need to use AnyEvent |
1133 | This is an advanced topic that you do not normally need to use AnyEvent |
1077 | in a module. This section is only of use to event loop authors who want |
1134 | in a module. This section is only of use to event loop authors who want |
1078 | to provide AnyEvent compatibility. |
1135 | to provide AnyEvent compatibility. |
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1603 | it is that this way, the handler will be restored to defaults on |
1660 | it is that this way, the handler will be restored to defaults on |
1604 | exec. |
1661 | exec. |
1605 | |
1662 | |
1606 | Feel free to install your own handler, or reset it to defaults. |
1663 | Feel free to install your own handler, or reset it to defaults. |
1607 | |
1664 | |
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1665 | RECOMMENDED/OPTIONAL MODULES |
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1666 | One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and |
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1667 | it's built-in modules) are required to use it. |
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1668 | |
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1669 | That does not mean that AnyEvent won't take advantage of some additional |
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1670 | modules if they are installed. |
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1671 | |
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1672 | This section epxlains which additional modules will be used, and how |
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1673 | they affect AnyEvent's operetion. |
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1674 | |
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1675 | Async::Interrupt |
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1676 | This slightly arcane module is used to implement fast signal |
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1677 | handling: To my knowledge, there is no way to do completely |
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1678 | race-free and quick signal handling in pure perl. To ensure that |
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1679 | signals still get delivered, AnyEvent will start an interval timer |
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1680 | to wake up perl (and catch the signals) with some delay (default is |
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1681 | 10 seconds, look for $AnyEvent::MAX_SIGNAL_LATENCY). |
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1682 | |
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1683 | If this module is available, then it will be used to implement |
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1684 | signal catching, which means that signals will not be delayed, and |
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1685 | the event loop will not be interrupted regularly, which is more |
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1686 | efficient (And good for battery life on laptops). |
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1687 | |
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1688 | This affects not just the pure-perl event loop, but also other event |
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1689 | loops that have no signal handling on their own (e.g. Glib, Tk, Qt). |
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1690 | |
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1691 | Some event loops (POE, Event, Event::Lib) offer signal watchers |
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1692 | natively, and either employ their own workarounds (POE) or use |
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1693 | AnyEvent's workaround (using $AnyEvent::MAX_SIGNAL_LATENCY). |
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1694 | Installing Async::Interrupt does nothing for those backends. |
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1695 | |
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1696 | EV This module isn't really "optional", as it is simply one of the |
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1697 | backend event loops that AnyEvent can use. However, it is simply the |
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1698 | best event loop available in terms of features, speed and stability: |
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1699 | It supports the AnyEvent API optimally, implements all the watcher |
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1700 | types in XS, does automatic timer adjustments even when no monotonic |
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1701 | clock is available, can take avdantage of advanced kernel interfaces |
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1702 | such as "epoll" and "kqueue", and is the fastest backend *by far*. |
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1703 | You can even embed Glib/Gtk2 in it (or vice versa, see EV::Glib and |
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1704 | Glib::EV). |
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1705 | |
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1706 | Guard |
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1707 | The guard module, when used, will be used to implement |
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1708 | "AnyEvent::Util::guard". This speeds up guards considerably (and |
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1709 | uses a lot less memory), but otherwise doesn't affect guard |
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1710 | operation much. It is purely used for performance. |
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1711 | |
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1712 | JSON and JSON::XS |
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1713 | This module is required when you want to read or write JSON data via |
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1714 | AnyEvent::Handle. It is also written in pure-perl, but can take |
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1715 | advantage of the ultra-high-speed JSON::XS module when it is |
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1716 | installed. |
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1717 | |
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1718 | In fact, AnyEvent::Handle will use JSON::XS by default if it is |
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1719 | installed. |
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1720 | |
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1721 | Net::SSLeay |
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1722 | Implementing TLS/SSL in Perl is certainly interesting, but not very |
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1723 | worthwhile: If this module is installed, then AnyEvent::Handle (with |
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1724 | the help of AnyEvent::TLS), gains the ability to do TLS/SSL. |
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1725 | |
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1726 | Time::HiRes |
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1727 | This module is part of perl since release 5.008. It will be used |
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1728 | when the chosen event library does not come with a timing source on |
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1729 | it's own. The pure-perl event loop (AnyEvent::Impl::Perl) will |
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1730 | additionally use it to try to use a monotonic clock for timing |
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1731 | stability. |
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1732 | |
1608 | FORK |
1733 | FORK |
1609 | Most event libraries are not fork-safe. The ones who are usually are |
1734 | Most event libraries are not fork-safe. The ones who are usually are |
1610 | because they rely on inefficient but fork-safe "select" or "poll" calls. |
1735 | because they rely on inefficient but fork-safe "select" or "poll" calls. |
1611 | Only EV is fully fork-aware. |
1736 | Only EV is fully fork-aware. |
1612 | |
1737 | |
1613 | If you have to fork, you must either do so *before* creating your first |
1738 | If you have to fork, you must either do so *before* creating your first |
1614 | watcher OR you must not use AnyEvent at all in the child. |
1739 | watcher OR you must not use AnyEvent at all in the child OR you must do |
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1740 | something completely out of the scope of AnyEvent. |
1615 | |
1741 | |
1616 | SECURITY CONSIDERATIONS |
1742 | SECURITY CONSIDERATIONS |
1617 | AnyEvent can be forced to load any event model via |
1743 | AnyEvent can be forced to load any event model via |
1618 | $ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used |
1744 | $ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used |
1619 | to execute arbitrary code or directly gain access, it can easily be used |
1745 | to execute arbitrary code or directly gain access, it can easily be used |
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1651 | Event::Lib, Qt, POE. |
1777 | Event::Lib, Qt, POE. |
1652 | |
1778 | |
1653 | Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event, |
1779 | Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event, |
1654 | AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl, |
1780 | AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl, |
1655 | AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE, |
1781 | AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE, |
1656 | AnyEvent::Impl::IOAsync. |
1782 | AnyEvent::Impl::IOAsync, Anyevent::Impl::Irssi. |
1657 | |
1783 | |
1658 | Non-blocking file handles, sockets, TCP clients and servers: |
1784 | Non-blocking file handles, sockets, TCP clients and servers: |
1659 | AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS. |
1785 | AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS. |
1660 | |
1786 | |
1661 | Asynchronous DNS: AnyEvent::DNS. |
1787 | Asynchronous DNS: AnyEvent::DNS. |