… | |
… | |
350 | invocation, and callback invocation will be synchronous. Synchronous |
350 | invocation, and callback invocation will be synchronous. Synchronous |
351 | means that it might take a while until the signal gets handled by the |
351 | 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. |
352 | process, but it is guaranteed not to interrupt any other callbacks. |
353 | |
353 | |
354 | The main advantage of using these watchers is that you can share a |
354 | The main advantage of using these watchers is that you can share a |
355 | signal between multiple watchers. |
355 | signal between multiple watchers, and AnyEvent will ensure that signals |
|
|
356 | will not interrupt your program at bad times. |
356 | |
357 | |
357 | This watcher might use %SIG, so programs overwriting those signals |
358 | This watcher might use %SIG (depending on the event loop used), so |
358 | directly will likely not work correctly. |
359 | programs overwriting those signals directly will likely not work |
|
|
360 | correctly. |
|
|
361 | |
|
|
362 | Also note that many event loops (e.g. Glib, Tk, Qt, IO::Async) do not |
|
|
363 | support attaching callbacks to signals, which is a pity, as you cannot |
|
|
364 | do race-free signal handling in perl. AnyEvent will try to do it's best, |
|
|
365 | but in some cases, signals will be delayed. The maximum time a signal |
|
|
366 | might be delayed is specified in $AnyEvent::MAX_SIGNAL_LATENCY (default: |
|
|
367 | 10 seconds). This variable can be changed only before the first signal |
|
|
368 | watcher is created, and should be left alone otherwise. Higher values |
|
|
369 | will cause fewer spurious wake-ups, which is better for power and CPU |
|
|
370 | saving. All these problems can be avoided by installing the optional |
|
|
371 | Async::Interrupt module. |
359 | |
372 | |
360 | Example: exit on SIGINT |
373 | Example: exit on SIGINT |
361 | |
374 | |
362 | my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 }); |
375 | my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 }); |
363 | |
376 | |
… | |
… | |
390 | of when you start the watcher. |
403 | of when you start the watcher. |
391 | |
404 | |
392 | This means you cannot create a child watcher as the very first thing in |
405 | 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 |
406 | an AnyEvent program, you *have* to create at least one watcher before |
394 | you "fork" the child (alternatively, you can call "AnyEvent::detect"). |
407 | you "fork" the child (alternatively, you can call "AnyEvent::detect"). |
|
|
408 | |
|
|
409 | As most event loops do not support waiting for child events, they will |
|
|
410 | be emulated by AnyEvent in most cases, in which the latency and race |
|
|
411 | problems mentioned in the description of signal watchers apply. |
395 | |
412 | |
396 | Example: fork a process and wait for it |
413 | Example: fork a process and wait for it |
397 | |
414 | |
398 | my $done = AnyEvent->condvar; |
415 | my $done = AnyEvent->condvar; |
399 | |
416 | |
… | |
… | |
448 | CONDITION VARIABLES |
465 | CONDITION VARIABLES |
449 | If you are familiar with some event loops you will know that all of them |
466 | If you are familiar with some event loops you will know that all of them |
450 | require you to run some blocking "loop", "run" or similar function that |
467 | require you to run some blocking "loop", "run" or similar function that |
451 | will actively watch for new events and call your callbacks. |
468 | will actively watch for new events and call your callbacks. |
452 | |
469 | |
453 | AnyEvent is different, it expects somebody else to run the event loop |
470 | AnyEvent is slightly different: it expects somebody else to run the |
454 | and will only block when necessary (usually when told by the user). |
471 | event loop and will only block when necessary (usually when told by the |
|
|
472 | user). |
455 | |
473 | |
456 | The instrument to do that is called a "condition variable", so called |
474 | The instrument to do that is called a "condition variable", so called |
457 | because they represent a condition that must become true. |
475 | because they represent a condition that must become true. |
458 | |
476 | |
|
|
477 | Now is probably a good time to look at the examples further below. |
|
|
478 | |
459 | Condition variables can be created by calling the "AnyEvent->condvar" |
479 | Condition variables can be created by calling the "AnyEvent->condvar" |
460 | method, usually without arguments. The only argument pair allowed is |
480 | method, usually without arguments. The only argument pair allowed is |
461 | |
|
|
462 | "cb", which specifies a callback to be called when the condition |
481 | "cb", which specifies a callback to be called when the condition |
463 | variable becomes true, with the condition variable as the first argument |
482 | variable becomes true, with the condition variable as the first argument |
464 | (but not the results). |
483 | (but not the results). |
465 | |
484 | |
466 | After creation, the condition variable is "false" until it becomes |
485 | After creation, the condition variable is "false" until it becomes |
… | |
… | |
515 | after => 1, |
534 | after => 1, |
516 | cb => sub { $result_ready->send }, |
535 | cb => sub { $result_ready->send }, |
517 | ); |
536 | ); |
518 | |
537 | |
519 | # this "blocks" (while handling events) till the callback |
538 | # this "blocks" (while handling events) till the callback |
520 | # calls send |
539 | # calls -<send |
521 | $result_ready->recv; |
540 | $result_ready->recv; |
522 | |
541 | |
523 | Example: wait for a timer, but take advantage of the fact that condition |
542 | Example: wait for a timer, but take advantage of the fact that condition |
524 | variables are also code references. |
543 | variables are also callable directly. |
525 | |
544 | |
526 | my $done = AnyEvent->condvar; |
545 | my $done = AnyEvent->condvar; |
527 | my $delay = AnyEvent->timer (after => 5, cb => $done); |
546 | my $delay = AnyEvent->timer (after => 5, cb => $done); |
528 | $done->recv; |
547 | $done->recv; |
529 | |
548 | |
… | |
… | |
535 | |
554 | |
536 | ... |
555 | ... |
537 | |
556 | |
538 | my @info = $couchdb->info->recv; |
557 | my @info = $couchdb->info->recv; |
539 | |
558 | |
540 | And this is how you would just ste a callback to be called whenever the |
559 | And this is how you would just set a callback to be called whenever the |
541 | results are available: |
560 | results are available: |
542 | |
561 | |
543 | $couchdb->info->cb (sub { |
562 | $couchdb->info->cb (sub { |
544 | my @info = $_[0]->recv; |
563 | my @info = $_[0]->recv; |
545 | }); |
564 | }); |
… | |
… | |
560 | |
579 | |
561 | Any arguments passed to the "send" call will be returned by all |
580 | Any arguments passed to the "send" call will be returned by all |
562 | future "->recv" calls. |
581 | future "->recv" calls. |
563 | |
582 | |
564 | Condition variables are overloaded so one can call them directly (as |
583 | Condition variables are overloaded so one can call them directly (as |
565 | a code reference). Calling them directly is the same as calling |
584 | if they were a code reference). Calling them directly is the same as |
566 | "send". Note, however, that many C-based event loops do not handle |
585 | calling "send". |
567 | overloading, so as tempting as it may be, passing a condition |
|
|
568 | variable instead of a callback does not work. Both the pure perl and |
|
|
569 | EV loops support overloading, however, as well as all functions that |
|
|
570 | use perl to invoke a callback (as in AnyEvent::Socket and |
|
|
571 | AnyEvent::DNS for example). |
|
|
572 | |
586 | |
573 | $cv->croak ($error) |
587 | $cv->croak ($error) |
574 | Similar to send, but causes all call's to "->recv" to invoke |
588 | Similar to send, but causes all call's to "->recv" to invoke |
575 | "Carp::croak" with the given error message/object/scalar. |
589 | "Carp::croak" with the given error message/object/scalar. |
576 | |
590 | |
577 | This can be used to signal any errors to the condition variable |
591 | This can be used to signal any errors to the condition variable |
578 | user/consumer. |
592 | user/consumer. Doing it this way instead of calling "croak" directly |
|
|
593 | delays the error detetcion, but has the overwhelmign advantage that |
|
|
594 | it diagnoses the error at the place where the result is expected, |
|
|
595 | and not deep in some event clalback without connection to the actual |
|
|
596 | code causing the problem. |
579 | |
597 | |
580 | $cv->begin ([group callback]) |
598 | $cv->begin ([group callback]) |
581 | $cv->end |
599 | $cv->end |
582 | These two methods can be used to combine many transactions/events |
600 | These two methods can be used to combine many transactions/events |
583 | into one. For example, a function that pings many hosts in parallel |
601 | into one. For example, a function that pings many hosts in parallel |
… | |
… | |
671 | function will call "croak". |
689 | function will call "croak". |
672 | |
690 | |
673 | In list context, all parameters passed to "send" will be returned, |
691 | In list context, all parameters passed to "send" will be returned, |
674 | in scalar context only the first one will be returned. |
692 | in scalar context only the first one will be returned. |
675 | |
693 | |
|
|
694 | Note that doing a blocking wait in a callback is not supported by |
|
|
695 | any event loop, that is, recursive invocation of a blocking "->recv" |
|
|
696 | is not allowed, and the "recv" call will "croak" if such a condition |
|
|
697 | is detected. This condition can be slightly loosened by using |
|
|
698 | Coro::AnyEvent, which allows you to do a blocking "->recv" from any |
|
|
699 | thread that doesn't run the event loop itself. |
|
|
700 | |
676 | Not all event models support a blocking wait - some die in that case |
701 | Not all event models support a blocking wait - some die in that case |
677 | (programs might want to do that to stay interactive), so *if you are |
702 | (programs might want to do that to stay interactive), so *if you are |
678 | using this from a module, never require a blocking wait*, but let |
703 | using this from a module, never require a blocking wait*. Instead, |
679 | the caller decide whether the call will block or not (for example, |
704 | let the caller decide whether the call will block or not (for |
680 | by coupling condition variables with some kind of request results |
705 | example, by coupling condition variables with some kind of request |
681 | and supporting callbacks so the caller knows that getting the result |
706 | results and supporting callbacks so the caller knows that getting |
682 | will not block, while still supporting blocking waits if the caller |
707 | the result will not block, while still supporting blocking waits if |
683 | so desires). |
708 | the caller so desires). |
684 | |
|
|
685 | Another reason *never* to "->recv" in a module is that you cannot |
|
|
686 | sensibly have two "->recv"'s in parallel, as that would require |
|
|
687 | multiple interpreters or coroutines/threads, none of which |
|
|
688 | "AnyEvent" can supply. |
|
|
689 | |
|
|
690 | The Coro module, however, *can* and *does* supply coroutines and, in |
|
|
691 | fact, Coro::AnyEvent replaces AnyEvent's condvars by coroutine-safe |
|
|
692 | versions and also integrates coroutines into AnyEvent, making |
|
|
693 | blocking "->recv" calls perfectly safe as long as they are done from |
|
|
694 | another coroutine (one that doesn't run the event loop). |
|
|
695 | |
709 | |
696 | You can ensure that "-recv" never blocks by setting a callback and |
710 | You can ensure that "-recv" never blocks by setting a callback and |
697 | only calling "->recv" from within that callback (or at a later |
711 | only calling "->recv" from within that callback (or at a later |
698 | time). This will work even when the event loop does not support |
712 | time). This will work even when the event loop does not support |
699 | blocking waits otherwise. |
713 | blocking waits otherwise. |
… | |
… | |
994 | by "PERL_ANYEVENT_MODEL". |
1008 | by "PERL_ANYEVENT_MODEL". |
995 | |
1009 | |
996 | When set to 2 or higher, cause AnyEvent to report to STDERR which |
1010 | When set to 2 or higher, cause AnyEvent to report to STDERR which |
997 | event model it chooses. |
1011 | event model it chooses. |
998 | |
1012 | |
|
|
1013 | When set to 8 or higher, then AnyEvent will report extra information |
|
|
1014 | on which optional modules it loads and how it implements certain |
|
|
1015 | features. |
|
|
1016 | |
999 | "PERL_ANYEVENT_STRICT" |
1017 | "PERL_ANYEVENT_STRICT" |
1000 | AnyEvent does not do much argument checking by default, as thorough |
1018 | AnyEvent does not do much argument checking by default, as thorough |
1001 | argument checking is very costly. Setting this variable to a true |
1019 | argument checking is very costly. Setting this variable to a true |
1002 | value will cause AnyEvent to load "AnyEvent::Strict" and then to |
1020 | value will cause AnyEvent to load "AnyEvent::Strict" and then to |
1003 | thoroughly check the arguments passed to most method calls. If it |
1021 | thoroughly check the arguments passed to most method calls. If it |
1004 | finds any problems, it will croak. |
1022 | finds any problems, it will croak. |
1005 | |
1023 | |
1006 | In other words, enables "strict" mode. |
1024 | In other words, enables "strict" mode. |
1007 | |
1025 | |
1008 | Unlike "use strict", it is definitely recommended to keep it off in |
1026 | Unlike "use strict" (or it's modern cousin, "use common::sense", it |
1009 | production. Keeping "PERL_ANYEVENT_STRICT=1" in your environment |
1027 | is definitely recommended to keep it off in production. Keeping |
|
|
1028 | "PERL_ANYEVENT_STRICT=1" in your environment while developing |
1010 | while developing programs can be very useful, however. |
1029 | programs can be very useful, however. |
1011 | |
1030 | |
1012 | "PERL_ANYEVENT_MODEL" |
1031 | "PERL_ANYEVENT_MODEL" |
1013 | This can be used to specify the event model to be used by AnyEvent, |
1032 | This can be used to specify the event model to be used by AnyEvent, |
1014 | before auto detection and -probing kicks in. It must be a string |
1033 | before auto detection and -probing kicks in. It must be a string |
1015 | consisting entirely of ASCII letters. The string "AnyEvent::Impl::" |
1034 | consisting entirely of ASCII letters. The string "AnyEvent::Impl::" |
… | |
… | |
1072 | "PERL_ANYEVENT_CA_FILE", "PERL_ANYEVENT_CA_PATH". |
1091 | "PERL_ANYEVENT_CA_FILE", "PERL_ANYEVENT_CA_PATH". |
1073 | When neither "ca_file" nor "ca_path" was specified during |
1092 | When neither "ca_file" nor "ca_path" was specified during |
1074 | AnyEvent::TLS context creation, and either of these environment |
1093 | AnyEvent::TLS context creation, and either of these environment |
1075 | variables exist, they will be used to specify CA certificate |
1094 | variables exist, they will be used to specify CA certificate |
1076 | locations instead of a system-dependent default. |
1095 | locations instead of a system-dependent default. |
|
|
1096 | |
|
|
1097 | "PERL_ANYEVENT_AVOID_GUARD" and "PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT" |
|
|
1098 | When these are set to 1, then the respective modules are not loaded. |
|
|
1099 | Mostly good for testing AnyEvent itself. |
1077 | |
1100 | |
1078 | SUPPLYING YOUR OWN EVENT MODEL INTERFACE |
1101 | SUPPLYING YOUR OWN EVENT MODEL INTERFACE |
1079 | This is an advanced topic that you do not normally need to use AnyEvent |
1102 | This is an advanced topic that you do not normally need to use AnyEvent |
1080 | in a module. This section is only of use to event loop authors who want |
1103 | in a module. This section is only of use to event loop authors who want |
1081 | to provide AnyEvent compatibility. |
1104 | to provide AnyEvent compatibility. |
… | |
… | |
1606 | it is that this way, the handler will be restored to defaults on |
1629 | it is that this way, the handler will be restored to defaults on |
1607 | exec. |
1630 | exec. |
1608 | |
1631 | |
1609 | Feel free to install your own handler, or reset it to defaults. |
1632 | Feel free to install your own handler, or reset it to defaults. |
1610 | |
1633 | |
|
|
1634 | RECOMMENDED/OPTIONAL MODULES |
|
|
1635 | One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and |
|
|
1636 | it's built-in modules) are required to use it. |
|
|
1637 | |
|
|
1638 | That does not mean that AnyEvent won't take advantage of some additional |
|
|
1639 | modules if they are installed. |
|
|
1640 | |
|
|
1641 | This section epxlains which additional modules will be used, and how |
|
|
1642 | they affect AnyEvent's operetion. |
|
|
1643 | |
|
|
1644 | Async::Interrupt |
|
|
1645 | This slightly arcane module is used to implement fast signal |
|
|
1646 | handling: To my knowledge, there is no way to do completely |
|
|
1647 | race-free and quick signal handling in pure perl. To ensure that |
|
|
1648 | signals still get delivered, AnyEvent will start an interval timer |
|
|
1649 | to wake up perl (and catch the signals) with soemd elay (default is |
|
|
1650 | 10 seconds, look for $AnyEvent::MAX_SIGNAL_LATENCY). |
|
|
1651 | |
|
|
1652 | If this module is available, then it will be used to implement |
|
|
1653 | signal catching, which means that signals will not be delayed, and |
|
|
1654 | the event loop will not be interrupted regularly, which is more |
|
|
1655 | efficient (And good for battery life on laptops). |
|
|
1656 | |
|
|
1657 | This affects not just the pure-perl event loop, but also other event |
|
|
1658 | loops that have no signal handling on their own (e.g. Glib, Tk, Qt). |
|
|
1659 | |
|
|
1660 | EV This module isn't really "optional", as it is simply one of the |
|
|
1661 | backend event loops that AnyEvent can use. However, it is simply the |
|
|
1662 | best event loop available in terms of features, speed and stability: |
|
|
1663 | It supports the AnyEvent API optimally, implements all the watcher |
|
|
1664 | types in XS, does automatic timer adjustments even when no monotonic |
|
|
1665 | clock is available, can take avdantage of advanced kernel interfaces |
|
|
1666 | such as "epoll" and "kqueue", and is the fastest backend *by far*. |
|
|
1667 | You can even embed Glib/Gtk2 in it (or vice versa, see EV::Glib and |
|
|
1668 | Glib::EV). |
|
|
1669 | |
|
|
1670 | Guard |
|
|
1671 | The guard module, when used, will be used to implement |
|
|
1672 | "AnyEvent::Util::guard". This speeds up guards considerably (and |
|
|
1673 | uses a lot less memory), but otherwise doesn't affect guard |
|
|
1674 | operation much. It is purely used for performance. |
|
|
1675 | |
|
|
1676 | JSON and JSON::XS |
|
|
1677 | This module is required when you want to read or write JSON data via |
|
|
1678 | AnyEvent::Handle. It is also written in pure-perl, but can take |
|
|
1679 | advantage of the ulta-high-speed JSON::XS module when it is |
|
|
1680 | installed. |
|
|
1681 | |
|
|
1682 | In fact, AnyEvent::Handle will use JSON::XS by default if it is |
|
|
1683 | installed. |
|
|
1684 | |
|
|
1685 | Net::SSLeay |
|
|
1686 | Implementing TLS/SSL in Perl is certainly interesting, but not very |
|
|
1687 | worthwhile: If this module is installed, then AnyEvent::Handle (with |
|
|
1688 | the help of AnyEvent::TLS), gains the ability to do TLS/SSL. |
|
|
1689 | |
|
|
1690 | Time::HiRes |
|
|
1691 | This module is part of perl since release 5.008. It will be used |
|
|
1692 | when the chosen event library does not come with a timing source on |
|
|
1693 | it's own. The pure-perl event loop (AnyEvent::Impl::Perl) will |
|
|
1694 | additionally use it to try to use a monotonic clock for timing |
|
|
1695 | stability. |
|
|
1696 | |
1611 | FORK |
1697 | FORK |
1612 | Most event libraries are not fork-safe. The ones who are usually are |
1698 | Most event libraries are not fork-safe. The ones who are usually are |
1613 | because they rely on inefficient but fork-safe "select" or "poll" calls. |
1699 | because they rely on inefficient but fork-safe "select" or "poll" calls. |
1614 | Only EV is fully fork-aware. |
1700 | Only EV is fully fork-aware. |
1615 | |
1701 | |
1616 | If you have to fork, you must either do so *before* creating your first |
1702 | If you have to fork, you must either do so *before* creating your first |
1617 | watcher OR you must not use AnyEvent at all in the child. |
1703 | watcher OR you must not use AnyEvent at all in the child OR you must do |
|
|
1704 | something completely out of the scope of AnyEvent. |
1618 | |
1705 | |
1619 | SECURITY CONSIDERATIONS |
1706 | SECURITY CONSIDERATIONS |
1620 | AnyEvent can be forced to load any event model via |
1707 | AnyEvent can be forced to load any event model via |
1621 | $ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used |
1708 | $ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used |
1622 | to execute arbitrary code or directly gain access, it can easily be used |
1709 | to execute arbitrary code or directly gain access, it can easily be used |