… | |
… | |
5 | Qt and POE are various supported event loops/environments. |
5 | Qt and POE are various supported event loops/environments. |
6 | |
6 | |
7 | SYNOPSIS |
7 | SYNOPSIS |
8 | use AnyEvent; |
8 | use AnyEvent; |
9 | |
9 | |
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|
10 | # if you prefer function calls, look at the L<AE> manpage for |
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|
11 | # an alternative API. |
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12 | |
10 | # file descriptor readable |
13 | # file handle or descriptor readable |
11 | my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... }); |
14 | my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... }); |
12 | |
15 | |
13 | # one-shot or repeating timers |
16 | # one-shot or repeating timers |
14 | my $w = AnyEvent->timer (after => $seconds, cb => sub { ... }); |
17 | my $w = AnyEvent->timer (after => $seconds, cb => sub { ... }); |
15 | my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ... |
18 | my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ... |
… | |
… | |
391 | correctly. |
394 | correctly. |
392 | |
395 | |
393 | Example: exit on SIGINT |
396 | Example: exit on SIGINT |
394 | |
397 | |
395 | my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 }); |
398 | my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 }); |
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399 | |
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400 | Restart Behaviour |
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401 | While restart behaviour is up to the event loop implementation, most |
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402 | will not restart syscalls (that includes Async::Interrupt and AnyEvent's |
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403 | pure perl implementation). |
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404 | |
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405 | Safe/Unsafe Signals |
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406 | Perl signals can be either "safe" (synchronous to opcode handling) or |
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407 | "unsafe" (asynchronous) - the former might get delayed indefinitely, the |
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408 | latter might corrupt your memory. |
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409 | |
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410 | AnyEvent signal handlers are, in addition, synchronous to the event |
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411 | loop, i.e. they will not interrupt your running perl program but will |
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412 | only be called as part of the normal event handling (just like timer, |
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413 | I/O etc. callbacks, too). |
396 | |
414 | |
397 | Signal Races, Delays and Workarounds |
415 | Signal Races, Delays and Workarounds |
398 | Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching |
416 | Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching |
399 | callbacks to signals in a generic way, which is a pity, as you cannot do |
417 | callbacks to signals in a generic way, which is a pity, as you cannot do |
400 | race-free signal handling in perl, requiring C libraries for this. |
418 | race-free signal handling in perl, requiring C libraries for this. |
… | |
… | |
453 | problems mentioned in the description of signal watchers apply. |
471 | problems mentioned in the description of signal watchers apply. |
454 | |
472 | |
455 | Example: fork a process and wait for it |
473 | Example: fork a process and wait for it |
456 | |
474 | |
457 | my $done = AnyEvent->condvar; |
475 | my $done = AnyEvent->condvar; |
458 | |
476 | |
459 | my $pid = fork or exit 5; |
477 | my $pid = fork or exit 5; |
460 | |
478 | |
461 | my $w = AnyEvent->child ( |
479 | my $w = AnyEvent->child ( |
462 | pid => $pid, |
480 | pid => $pid, |
463 | cb => sub { |
481 | cb => sub { |
464 | my ($pid, $status) = @_; |
482 | my ($pid, $status) = @_; |
465 | warn "pid $pid exited with status $status"; |
483 | warn "pid $pid exited with status $status"; |
466 | $done->send; |
484 | $done->send; |
467 | }, |
485 | }, |
468 | ); |
486 | ); |
469 | |
487 | |
470 | # do something else, then wait for process exit |
488 | # do something else, then wait for process exit |
471 | $done->recv; |
489 | $done->recv; |
472 | |
490 | |
473 | IDLE WATCHERS |
491 | IDLE WATCHERS |
474 | $w = AnyEvent->idle (cb => <callback>); |
492 | $w = AnyEvent->idle (cb => <callback>); |
475 | |
493 | |
476 | Sometimes there is a need to do something, but it is not so important to |
494 | Repeatedly invoke the callback after the process becomes idle, until |
477 | do it instantly, but only when there is nothing better to do. This |
495 | either the watcher is destroyed or new events have been detected. |
478 | "nothing better to do" is usually defined to be "no other events need |
|
|
479 | attention by the event loop". |
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|
480 | |
496 | |
481 | Idle watchers ideally get invoked when the event loop has nothing better |
497 | Idle watchers are useful when there is a need to do something, but it is |
482 | to do, just before it would block the process to wait for new events. |
498 | not so important (or wise) to do it instantly. The callback will be |
483 | Instead of blocking, the idle watcher is invoked. |
499 | invoked only when there is "nothing better to do", which is usually |
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500 | defined as "all outstanding events have been handled and no new events |
|
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501 | have been detected". That means that idle watchers ideally get invoked |
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502 | when the event loop has just polled for new events but none have been |
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503 | detected. Instead of blocking to wait for more events, the idle watchers |
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504 | will be invoked. |
484 | |
505 | |
485 | Most event loops unfortunately do not really support idle watchers (only |
506 | Unfortunately, most event loops do not really support idle watchers |
486 | EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent |
507 | (only EV, Event and Glib do it in a usable fashion) - for the rest, |
487 | will simply call the callback "from time to time". |
508 | AnyEvent will simply call the callback "from time to time". |
488 | |
509 | |
489 | Example: read lines from STDIN, but only process them when the program |
510 | Example: read lines from STDIN, but only process them when the program |
490 | is otherwise idle: |
511 | is otherwise idle: |
491 | |
512 | |
492 | my @lines; # read data |
513 | my @lines; # read data |
… | |
… | |
571 | which eventually calls "-> send", and the "consumer side", which waits |
592 | which eventually calls "-> send", and the "consumer side", which waits |
572 | for the send to occur. |
593 | for the send to occur. |
573 | |
594 | |
574 | Example: wait for a timer. |
595 | Example: wait for a timer. |
575 | |
596 | |
576 | # wait till the result is ready |
597 | # condition: "wait till the timer is fired" |
577 | my $result_ready = AnyEvent->condvar; |
598 | my $timer_fired = AnyEvent->condvar; |
578 | |
599 | |
579 | # do something such as adding a timer |
600 | # create the timer - we could wait for, say |
580 | # or socket watcher the calls $result_ready->send |
601 | # a handle becomign ready, or even an |
581 | # when the "result" is ready. |
602 | # AnyEvent::HTTP request to finish, but |
582 | # in this case, we simply use a timer: |
603 | # in this case, we simply use a timer: |
583 | my $w = AnyEvent->timer ( |
604 | my $w = AnyEvent->timer ( |
584 | after => 1, |
605 | after => 1, |
585 | cb => sub { $result_ready->send }, |
606 | cb => sub { $timer_fired->send }, |
586 | ); |
607 | ); |
587 | |
608 | |
588 | # this "blocks" (while handling events) till the callback |
609 | # this "blocks" (while handling events) till the callback |
589 | # calls ->send |
610 | # calls ->send |
590 | $result_ready->recv; |
611 | $timer_fired->recv; |
591 | |
612 | |
592 | Example: wait for a timer, but take advantage of the fact that condition |
613 | Example: wait for a timer, but take advantage of the fact that condition |
593 | variables are also callable directly. |
614 | variables are also callable directly. |
594 | |
615 | |
595 | my $done = AnyEvent->condvar; |
616 | my $done = AnyEvent->condvar; |
… | |
… | |
904 | You should check $AnyEvent::MODEL before adding to this array, |
925 | You should check $AnyEvent::MODEL before adding to this array, |
905 | though: if it is defined then the event loop has already been |
926 | though: if it is defined then the event loop has already been |
906 | detected, and the array will be ignored. |
927 | detected, and the array will be ignored. |
907 | |
928 | |
908 | Best use "AnyEvent::post_detect { BLOCK }" when your application |
929 | Best use "AnyEvent::post_detect { BLOCK }" when your application |
909 | allows it,as it takes care of these details. |
930 | allows it, as it takes care of these details. |
910 | |
931 | |
911 | This variable is mainly useful for modules that can do something |
932 | This variable is mainly useful for modules that can do something |
912 | useful when AnyEvent is used and thus want to know when it is |
933 | useful when AnyEvent is used and thus want to know when it is |
913 | initialised, but do not need to even load it by default. This array |
934 | initialised, but do not need to even load it by default. This array |
914 | provides the means to hook into AnyEvent passively, without loading |
935 | provides the means to hook into AnyEvent passively, without loading |
915 | it. |
936 | it. |
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937 | |
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938 | Example: To load Coro::AnyEvent whenever Coro and AnyEvent are used |
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939 | together, you could put this into Coro (this is the actual code used |
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940 | by Coro to accomplish this): |
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941 | |
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942 | if (defined $AnyEvent::MODEL) { |
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943 | # AnyEvent already initialised, so load Coro::AnyEvent |
|
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944 | require Coro::AnyEvent; |
|
|
945 | } else { |
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|
946 | # AnyEvent not yet initialised, so make sure to load Coro::AnyEvent |
|
|
947 | # as soon as it is |
|
|
948 | push @AnyEvent::post_detect, sub { require Coro::AnyEvent }; |
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|
949 | } |
916 | |
950 | |
917 | WHAT TO DO IN A MODULE |
951 | WHAT TO DO IN A MODULE |
918 | As a module author, you should "use AnyEvent" and call AnyEvent methods |
952 | As a module author, you should "use AnyEvent" and call AnyEvent methods |
919 | freely, but you should not load a specific event module or rely on it. |
953 | freely, but you should not load a specific event module or rely on it. |
920 | |
954 | |
… | |
… | |
1045 | Has special support for AnyEvent via Coro::AnyEvent. |
1079 | Has special support for AnyEvent via Coro::AnyEvent. |
1046 | |
1080 | |
1047 | SIMPLIFIED AE API |
1081 | SIMPLIFIED AE API |
1048 | Starting with version 5.0, AnyEvent officially supports a second, much |
1082 | Starting with version 5.0, AnyEvent officially supports a second, much |
1049 | simpler, API that is designed to reduce the calling, typing and memory |
1083 | simpler, API that is designed to reduce the calling, typing and memory |
1050 | overhead. |
1084 | overhead by using function call syntax and a fixed number of parameters. |
1051 | |
1085 | |
1052 | See the AE manpage for details. |
1086 | See the AE manpage for details. |
1053 | |
1087 | |
1054 | ERROR AND EXCEPTION HANDLING |
1088 | ERROR AND EXCEPTION HANDLING |
1055 | In general, AnyEvent does not do any error handling - it relies on the |
1089 | In general, AnyEvent does not do any error handling - it relies on the |
… | |
… | |
1320 | |
1354 | |
1321 | The actual code goes further and collects all errors ("die"s, |
1355 | The actual code goes further and collects all errors ("die"s, |
1322 | exceptions) that occurred during request processing. The "result" method |
1356 | exceptions) that occurred during request processing. The "result" method |
1323 | detects whether an exception as thrown (it is stored inside the $txn |
1357 | detects whether an exception as thrown (it is stored inside the $txn |
1324 | object) and just throws the exception, which means connection errors and |
1358 | object) and just throws the exception, which means connection errors and |
1325 | other problems get reported tot he code that tries to use the result, |
1359 | other problems get reported to the code that tries to use the result, |
1326 | not in a random callback. |
1360 | not in a random callback. |
1327 | |
1361 | |
1328 | All of this enables the following usage styles: |
1362 | All of this enables the following usage styles: |
1329 | |
1363 | |
1330 | 1. Blocking: |
1364 | 1. Blocking: |
… | |
… | |
1709 | it's built-in modules) are required to use it. |
1743 | it's built-in modules) are required to use it. |
1710 | |
1744 | |
1711 | That does not mean that AnyEvent won't take advantage of some additional |
1745 | That does not mean that AnyEvent won't take advantage of some additional |
1712 | modules if they are installed. |
1746 | modules if they are installed. |
1713 | |
1747 | |
1714 | This section epxlains which additional modules will be used, and how |
1748 | This section explains which additional modules will be used, and how |
1715 | they affect AnyEvent's operetion. |
1749 | they affect AnyEvent's operation. |
1716 | |
1750 | |
1717 | Async::Interrupt |
1751 | Async::Interrupt |
1718 | This slightly arcane module is used to implement fast signal |
1752 | This slightly arcane module is used to implement fast signal |
1719 | handling: To my knowledge, there is no way to do completely |
1753 | handling: To my knowledge, there is no way to do completely |
1720 | race-free and quick signal handling in pure perl. To ensure that |
1754 | race-free and quick signal handling in pure perl. To ensure that |
… | |
… | |
1723 | 10 seconds, look for $AnyEvent::MAX_SIGNAL_LATENCY). |
1757 | 10 seconds, look for $AnyEvent::MAX_SIGNAL_LATENCY). |
1724 | |
1758 | |
1725 | If this module is available, then it will be used to implement |
1759 | If this module is available, then it will be used to implement |
1726 | signal catching, which means that signals will not be delayed, and |
1760 | signal catching, which means that signals will not be delayed, and |
1727 | the event loop will not be interrupted regularly, which is more |
1761 | the event loop will not be interrupted regularly, which is more |
1728 | efficient (And good for battery life on laptops). |
1762 | efficient (and good for battery life on laptops). |
1729 | |
1763 | |
1730 | This affects not just the pure-perl event loop, but also other event |
1764 | This affects not just the pure-perl event loop, but also other event |
1731 | loops that have no signal handling on their own (e.g. Glib, Tk, Qt). |
1765 | loops that have no signal handling on their own (e.g. Glib, Tk, Qt). |
1732 | |
1766 | |
1733 | Some event loops (POE, Event, Event::Lib) offer signal watchers |
1767 | Some event loops (POE, Event, Event::Lib) offer signal watchers |
… | |
… | |
1743 | clock is available, can take avdantage of advanced kernel interfaces |
1777 | clock is available, can take avdantage of advanced kernel interfaces |
1744 | such as "epoll" and "kqueue", and is the fastest backend *by far*. |
1778 | such as "epoll" and "kqueue", and is the fastest backend *by far*. |
1745 | You can even embed Glib/Gtk2 in it (or vice versa, see EV::Glib and |
1779 | You can even embed Glib/Gtk2 in it (or vice versa, see EV::Glib and |
1746 | Glib::EV). |
1780 | Glib::EV). |
1747 | |
1781 | |
|
|
1782 | If you only use backends that rely on another event loop (e.g. |
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1783 | "Tk"), then this module will do nothing for you. |
|
|
1784 | |
1748 | Guard |
1785 | Guard |
1749 | The guard module, when used, will be used to implement |
1786 | The guard module, when used, will be used to implement |
1750 | "AnyEvent::Util::guard". This speeds up guards considerably (and |
1787 | "AnyEvent::Util::guard". This speeds up guards considerably (and |
1751 | uses a lot less memory), but otherwise doesn't affect guard |
1788 | uses a lot less memory), but otherwise doesn't affect guard |
1752 | operation much. It is purely used for performance. |
1789 | operation much. It is purely used for performance. |
1753 | |
1790 | |
1754 | JSON and JSON::XS |
1791 | JSON and JSON::XS |
1755 | One of these modules is required when you want to read or write JSON |
1792 | One of these modules is required when you want to read or write JSON |
1756 | data via AnyEvent::Handle. It is also written in pure-perl, but can |
1793 | data via AnyEvent::Handle. JSON is also written in pure-perl, but |
1757 | take advantage of the ultra-high-speed JSON::XS module when it is |
1794 | can take advantage of the ultra-high-speed JSON::XS module when it |
1758 | installed. |
1795 | is installed. |
1759 | |
|
|
1760 | In fact, AnyEvent::Handle will use JSON::XS by default if it is |
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|
1761 | installed. |
|
|
1762 | |
1796 | |
1763 | Net::SSLeay |
1797 | Net::SSLeay |
1764 | Implementing TLS/SSL in Perl is certainly interesting, but not very |
1798 | Implementing TLS/SSL in Perl is certainly interesting, but not very |
1765 | worthwhile: If this module is installed, then AnyEvent::Handle (with |
1799 | worthwhile: If this module is installed, then AnyEvent::Handle (with |
1766 | the help of AnyEvent::TLS), gains the ability to do TLS/SSL. |
1800 | the help of AnyEvent::TLS), gains the ability to do TLS/SSL. |
… | |
… | |
1772 | additionally use it to try to use a monotonic clock for timing |
1806 | additionally use it to try to use a monotonic clock for timing |
1773 | stability. |
1807 | stability. |
1774 | |
1808 | |
1775 | FORK |
1809 | FORK |
1776 | Most event libraries are not fork-safe. The ones who are usually are |
1810 | Most event libraries are not fork-safe. The ones who are usually are |
1777 | because they rely on inefficient but fork-safe "select" or "poll" calls. |
1811 | because they rely on inefficient but fork-safe "select" or "poll" calls |
1778 | Only EV is fully fork-aware. |
1812 | - higher performance APIs such as BSD's kqueue or the dreaded Linux |
|
|
1813 | epoll are usually badly thought-out hacks that are incompatible with |
|
|
1814 | fork in one way or another. Only EV is fully fork-aware and ensures that |
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|
1815 | you continue event-processing in both parent and child (or both, if you |
|
|
1816 | know what you are doing). |
|
|
1817 | |
|
|
1818 | This means that, in general, you cannot fork and do event processing in |
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1819 | the child if the event library was initialised before the fork (which |
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1820 | usually happens when the first AnyEvent watcher is created, or the |
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1821 | library is loaded). |
1779 | |
1822 | |
1780 | If you have to fork, you must either do so *before* creating your first |
1823 | If you have to fork, you must either do so *before* creating your first |
1781 | watcher OR you must not use AnyEvent at all in the child OR you must do |
1824 | watcher OR you must not use AnyEvent at all in the child OR you must do |
1782 | something completely out of the scope of AnyEvent. |
1825 | something completely out of the scope of AnyEvent. |
|
|
1826 | |
|
|
1827 | The problem of doing event processing in the parent *and* the child is |
|
|
1828 | much more complicated: even for backends that *are* fork-aware or |
|
|
1829 | fork-safe, their behaviour is not usually what you want: fork clones all |
|
|
1830 | watchers, that means all timers, I/O watchers etc. are active in both |
|
|
1831 | parent and child, which is almost never what you want. USing "exec" to |
|
|
1832 | start worker children from some kind of manage rprocess is usually |
|
|
1833 | preferred, because it is much easier and cleaner, at the expense of |
|
|
1834 | having to have another binary. |
1783 | |
1835 | |
1784 | SECURITY CONSIDERATIONS |
1836 | SECURITY CONSIDERATIONS |
1785 | AnyEvent can be forced to load any event model via |
1837 | AnyEvent can be forced to load any event model via |
1786 | $ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used |
1838 | $ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used |
1787 | to execute arbitrary code or directly gain access, it can easily be used |
1839 | to execute arbitrary code or directly gain access, it can easily be used |
… | |
… | |
1791 | |
1843 | |
1792 | You can make AnyEvent completely ignore this variable by deleting it |
1844 | You can make AnyEvent completely ignore this variable by deleting it |
1793 | before the first watcher gets created, e.g. with a "BEGIN" block: |
1845 | before the first watcher gets created, e.g. with a "BEGIN" block: |
1794 | |
1846 | |
1795 | BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} } |
1847 | BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} } |
1796 | |
1848 | |
1797 | use AnyEvent; |
1849 | use AnyEvent; |
1798 | |
1850 | |
1799 | Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can |
1851 | Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can |
1800 | be used to probe what backend is used and gain other information (which |
1852 | be used to probe what backend is used and gain other information (which |
1801 | is probably even less useful to an attacker than PERL_ANYEVENT_MODEL), |
1853 | is probably even less useful to an attacker than PERL_ANYEVENT_MODEL), |
1802 | and $ENV{PERL_ANYEVENT_STRICT}. |
1854 | and $ENV{PERL_ANYEVENT_STRICT}. |