… | |
… | |
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 | |
|
|
10 | # if you prefer function calls, look at the L<AE> manpage for |
|
|
11 | # an alternative API. |
|
|
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 => ... |
… | |
… | |
354 | time, which might affect timers and time-outs. |
357 | time, which might affect timers and time-outs. |
355 | |
358 | |
356 | When this is the case, you can call this method, which will update |
359 | When this is the case, you can call this method, which will update |
357 | the event loop's idea of "current time". |
360 | the event loop's idea of "current time". |
358 | |
361 | |
|
|
362 | A typical example would be a script in a web server (e.g. |
|
|
363 | "mod_perl") - when mod_perl executes the script, then the event loop |
|
|
364 | will have the wrong idea about the "current time" (being potentially |
|
|
365 | far in the past, when the script ran the last time). In that case |
|
|
366 | you should arrange a call to "AnyEvent->now_update" each time the |
|
|
367 | web server process wakes up again (e.g. at the start of your script, |
|
|
368 | or in a handler). |
|
|
369 | |
359 | Note that updating the time *might* cause some events to be handled. |
370 | Note that updating the time *might* cause some events to be handled. |
360 | |
371 | |
361 | SIGNAL WATCHERS |
372 | SIGNAL WATCHERS |
362 | $w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>); |
373 | $w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>); |
363 | |
374 | |
… | |
… | |
383 | correctly. |
394 | correctly. |
384 | |
395 | |
385 | Example: exit on SIGINT |
396 | Example: exit on SIGINT |
386 | |
397 | |
387 | my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 }); |
398 | my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 }); |
|
|
399 | |
|
|
400 | Restart Behaviour |
|
|
401 | While restart behaviour is up to the event loop implementation, most |
|
|
402 | will not restart syscalls (that includes Async::Interrupt and AnyEvent's |
|
|
403 | pure perl implementation). |
|
|
404 | |
|
|
405 | Safe/Unsafe Signals |
|
|
406 | Perl signals can be either "safe" (synchronous to opcode handling) or |
|
|
407 | "unsafe" (asynchronous) - the former might get delayed indefinitely, the |
|
|
408 | latter might corrupt your memory. |
|
|
409 | |
|
|
410 | AnyEvent signal handlers are, in addition, synchronous to the event |
|
|
411 | loop, i.e. they will not interrupt your running perl program but will |
|
|
412 | only be called as part of the normal event handling (just like timer, |
|
|
413 | I/O etc. callbacks, too). |
388 | |
414 | |
389 | Signal Races, Delays and Workarounds |
415 | Signal Races, Delays and Workarounds |
390 | 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 |
391 | 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 |
392 | race-free signal handling in perl, requiring C libraries for this. |
418 | race-free signal handling in perl, requiring C libraries for this. |
… | |
… | |
463 | $done->recv; |
489 | $done->recv; |
464 | |
490 | |
465 | IDLE WATCHERS |
491 | IDLE WATCHERS |
466 | $w = AnyEvent->idle (cb => <callback>); |
492 | $w = AnyEvent->idle (cb => <callback>); |
467 | |
493 | |
468 | 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 |
469 | 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. |
470 | "nothing better to do" is usually defined to be "no other events need |
|
|
471 | attention by the event loop". |
|
|
472 | |
496 | |
473 | 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 |
474 | 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 |
475 | Instead of blocking, the idle watcher is invoked. |
499 | invoked only when there is "nothing better to do", which is usually |
|
|
500 | defined as "all outstanding events have been handled and no new events |
|
|
501 | have been detected". That means that idle watchers ideally get invoked |
|
|
502 | when the event loop has just polled for new events but none have been |
|
|
503 | detected. Instead of blocking to wait for more events, the idle watchers |
|
|
504 | will be invoked. |
476 | |
505 | |
477 | Most event loops unfortunately do not really support idle watchers (only |
506 | Unfortunately, most event loops do not really support idle watchers |
478 | 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, |
479 | will simply call the callback "from time to time". |
508 | AnyEvent will simply call the callback "from time to time". |
480 | |
509 | |
481 | 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 |
482 | is otherwise idle: |
511 | is otherwise idle: |
483 | |
512 | |
484 | my @lines; # read data |
513 | my @lines; # read data |
… | |
… | |
563 | which eventually calls "-> send", and the "consumer side", which waits |
592 | which eventually calls "-> send", and the "consumer side", which waits |
564 | for the send to occur. |
593 | for the send to occur. |
565 | |
594 | |
566 | Example: wait for a timer. |
595 | Example: wait for a timer. |
567 | |
596 | |
568 | # wait till the result is ready |
597 | # condition: "wait till the timer is fired" |
569 | my $result_ready = AnyEvent->condvar; |
598 | my $timer_fired = AnyEvent->condvar; |
570 | |
599 | |
571 | # do something such as adding a timer |
600 | # create the timer - we could wait for, say |
572 | # or socket watcher the calls $result_ready->send |
601 | # a handle becomign ready, or even an |
573 | # when the "result" is ready. |
602 | # AnyEvent::HTTP request to finish, but |
574 | # in this case, we simply use a timer: |
603 | # in this case, we simply use a timer: |
575 | my $w = AnyEvent->timer ( |
604 | my $w = AnyEvent->timer ( |
576 | after => 1, |
605 | after => 1, |
577 | cb => sub { $result_ready->send }, |
606 | cb => sub { $timer_fired->send }, |
578 | ); |
607 | ); |
579 | |
608 | |
580 | # this "blocks" (while handling events) till the callback |
609 | # this "blocks" (while handling events) till the callback |
581 | # calls ->send |
610 | # calls ->send |
582 | $result_ready->recv; |
611 | $timer_fired->recv; |
583 | |
612 | |
584 | 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 |
585 | variables are also callable directly. |
614 | variables are also callable directly. |
586 | |
615 | |
587 | my $done = AnyEvent->condvar; |
616 | my $done = AnyEvent->condvar; |
… | |
… | |
896 | You should check $AnyEvent::MODEL before adding to this array, |
925 | You should check $AnyEvent::MODEL before adding to this array, |
897 | 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 |
898 | detected, and the array will be ignored. |
927 | detected, and the array will be ignored. |
899 | |
928 | |
900 | Best use "AnyEvent::post_detect { BLOCK }" when your application |
929 | Best use "AnyEvent::post_detect { BLOCK }" when your application |
901 | allows it,as it takes care of these details. |
930 | allows it, as it takes care of these details. |
902 | |
931 | |
903 | This variable is mainly useful for modules that can do something |
932 | This variable is mainly useful for modules that can do something |
904 | 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 |
905 | 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 |
906 | provides the means to hook into AnyEvent passively, without loading |
935 | provides the means to hook into AnyEvent passively, without loading |
907 | it. |
936 | it. |
|
|
937 | |
|
|
938 | Example: To load Coro::AnyEvent whenever Coro and AnyEvent are used |
|
|
939 | together, you could put this into Coro (this is the actual code used |
|
|
940 | by Coro to accomplish this): |
|
|
941 | |
|
|
942 | if (defined $AnyEvent::MODEL) { |
|
|
943 | # AnyEvent already initialised, so load Coro::AnyEvent |
|
|
944 | require Coro::AnyEvent; |
|
|
945 | } else { |
|
|
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 }; |
|
|
949 | } |
908 | |
950 | |
909 | WHAT TO DO IN A MODULE |
951 | WHAT TO DO IN A MODULE |
910 | 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 |
911 | 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. |
912 | |
954 | |
… | |
… | |
1037 | Has special support for AnyEvent via Coro::AnyEvent. |
1079 | Has special support for AnyEvent via Coro::AnyEvent. |
1038 | |
1080 | |
1039 | SIMPLIFIED AE API |
1081 | SIMPLIFIED AE API |
1040 | Starting with version 5.0, AnyEvent officially supports a second, much |
1082 | Starting with version 5.0, AnyEvent officially supports a second, much |
1041 | 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 |
1042 | overhead. |
1084 | overhead by using function call syntax and a fixed number of parameters. |
1043 | |
1085 | |
1044 | See the AE manpage for details. |
1086 | See the AE manpage for details. |
1045 | |
1087 | |
1046 | ERROR AND EXCEPTION HANDLING |
1088 | ERROR AND EXCEPTION HANDLING |
1047 | 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 |
… | |
… | |
1228 | warn "read: $input\n"; # output what has been read |
1270 | warn "read: $input\n"; # output what has been read |
1229 | $cv->send if $input =~ /^q/i; # quit program if /^q/i |
1271 | $cv->send if $input =~ /^q/i; # quit program if /^q/i |
1230 | }, |
1272 | }, |
1231 | ); |
1273 | ); |
1232 | |
1274 | |
1233 | my $time_watcher; # can only be used once |
|
|
1234 | |
|
|
1235 | sub new_timer { |
|
|
1236 | $timer = AnyEvent->timer (after => 1, cb => sub { |
1275 | my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub { |
1237 | warn "timeout\n"; # print 'timeout' about every second |
1276 | warn "timeout\n"; # print 'timeout' at most every second |
1238 | &new_timer; # and restart the time |
|
|
1239 | }); |
|
|
1240 | } |
1277 | }); |
1241 | |
|
|
1242 | new_timer; # create first timer |
|
|
1243 | |
1278 | |
1244 | $cv->recv; # wait until user enters /^q/i |
1279 | $cv->recv; # wait until user enters /^q/i |
1245 | |
1280 | |
1246 | REAL-WORLD EXAMPLE |
1281 | REAL-WORLD EXAMPLE |
1247 | Consider the Net::FCP module. It features (among others) the following |
1282 | Consider the Net::FCP module. It features (among others) the following |
… | |
… | |
1319 | |
1354 | |
1320 | The actual code goes further and collects all errors ("die"s, |
1355 | The actual code goes further and collects all errors ("die"s, |
1321 | exceptions) that occurred during request processing. The "result" method |
1356 | exceptions) that occurred during request processing. The "result" method |
1322 | 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 |
1323 | object) and just throws the exception, which means connection errors and |
1358 | object) and just throws the exception, which means connection errors and |
1324 | 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, |
1325 | not in a random callback. |
1360 | not in a random callback. |
1326 | |
1361 | |
1327 | All of this enables the following usage styles: |
1362 | All of this enables the following usage styles: |
1328 | |
1363 | |
1329 | 1. Blocking: |
1364 | 1. Blocking: |
… | |
… | |
1665 | As you can see, the AnyEvent + EV combination even beats the |
1700 | As you can see, the AnyEvent + EV combination even beats the |
1666 | hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl |
1701 | hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl |
1667 | backend easily beats IO::Lambda and POE. |
1702 | backend easily beats IO::Lambda and POE. |
1668 | |
1703 | |
1669 | And even the 100% non-blocking version written using the high-level (and |
1704 | And even the 100% non-blocking version written using the high-level (and |
1670 | slow :) AnyEvent::Handle abstraction beats both POE and IO::Lambda by a |
1705 | slow :) AnyEvent::Handle abstraction beats both POE and IO::Lambda |
1671 | large margin, even though it does all of DNS, tcp-connect and socket I/O |
1706 | higher level ("unoptimised") abstractions by a large margin, even though |
1672 | in a non-blocking way. |
1707 | it does all of DNS, tcp-connect and socket I/O in a non-blocking way. |
1673 | |
1708 | |
1674 | The two AnyEvent benchmarks programs can be found as eg/ae0.pl and |
1709 | The two AnyEvent benchmarks programs can be found as eg/ae0.pl and |
1675 | eg/ae2.pl in the AnyEvent distribution, the remaining benchmarks are |
1710 | eg/ae2.pl in the AnyEvent distribution, the remaining benchmarks are |
1676 | part of the IO::lambda distribution and were used without any changes. |
1711 | part of the IO::Lambda distribution and were used without any changes. |
1677 | |
1712 | |
1678 | SIGNALS |
1713 | SIGNALS |
1679 | AnyEvent currently installs handlers for these signals: |
1714 | AnyEvent currently installs handlers for these signals: |
1680 | |
1715 | |
1681 | SIGCHLD |
1716 | SIGCHLD |
… | |
… | |
1708 | it's built-in modules) are required to use it. |
1743 | it's built-in modules) are required to use it. |
1709 | |
1744 | |
1710 | 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 |
1711 | modules if they are installed. |
1746 | modules if they are installed. |
1712 | |
1747 | |
1713 | This section epxlains which additional modules will be used, and how |
1748 | This section explains which additional modules will be used, and how |
1714 | they affect AnyEvent's operetion. |
1749 | they affect AnyEvent's operation. |
1715 | |
1750 | |
1716 | Async::Interrupt |
1751 | Async::Interrupt |
1717 | This slightly arcane module is used to implement fast signal |
1752 | This slightly arcane module is used to implement fast signal |
1718 | handling: To my knowledge, there is no way to do completely |
1753 | handling: To my knowledge, there is no way to do completely |
1719 | 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 |
… | |
… | |
1722 | 10 seconds, look for $AnyEvent::MAX_SIGNAL_LATENCY). |
1757 | 10 seconds, look for $AnyEvent::MAX_SIGNAL_LATENCY). |
1723 | |
1758 | |
1724 | 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 |
1725 | signal catching, which means that signals will not be delayed, and |
1760 | signal catching, which means that signals will not be delayed, and |
1726 | the event loop will not be interrupted regularly, which is more |
1761 | the event loop will not be interrupted regularly, which is more |
1727 | efficient (And good for battery life on laptops). |
1762 | efficient (and good for battery life on laptops). |
1728 | |
1763 | |
1729 | 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 |
1730 | 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). |
1731 | |
1766 | |
1732 | Some event loops (POE, Event, Event::Lib) offer signal watchers |
1767 | Some event loops (POE, Event, Event::Lib) offer signal watchers |
… | |
… | |
1742 | clock is available, can take avdantage of advanced kernel interfaces |
1777 | clock is available, can take avdantage of advanced kernel interfaces |
1743 | 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*. |
1744 | 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 |
1745 | Glib::EV). |
1780 | Glib::EV). |
1746 | |
1781 | |
|
|
1782 | If you only use backends that rely on another event loop (e.g. |
|
|
1783 | "Tk"), then this module will do nothing for you. |
|
|
1784 | |
1747 | Guard |
1785 | Guard |
1748 | The guard module, when used, will be used to implement |
1786 | The guard module, when used, will be used to implement |
1749 | "AnyEvent::Util::guard". This speeds up guards considerably (and |
1787 | "AnyEvent::Util::guard". This speeds up guards considerably (and |
1750 | uses a lot less memory), but otherwise doesn't affect guard |
1788 | uses a lot less memory), but otherwise doesn't affect guard |
1751 | operation much. It is purely used for performance. |
1789 | operation much. It is purely used for performance. |
1752 | |
1790 | |
1753 | JSON and JSON::XS |
1791 | JSON and JSON::XS |
1754 | This module is required when you want to read or write JSON data via |
1792 | One of these modules is required when you want to read or write JSON |
1755 | AnyEvent::Handle. It is also written in pure-perl, but can take |
1793 | data via AnyEvent::Handle. JSON is also written in pure-perl, but |
1756 | 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 |
1757 | installed. |
1795 | is installed. |
1758 | |
|
|
1759 | In fact, AnyEvent::Handle will use JSON::XS by default if it is |
|
|
1760 | installed. |
|
|
1761 | |
1796 | |
1762 | Net::SSLeay |
1797 | Net::SSLeay |
1763 | Implementing TLS/SSL in Perl is certainly interesting, but not very |
1798 | Implementing TLS/SSL in Perl is certainly interesting, but not very |
1764 | worthwhile: If this module is installed, then AnyEvent::Handle (with |
1799 | worthwhile: If this module is installed, then AnyEvent::Handle (with |
1765 | 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. |
… | |
… | |
1771 | 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 |
1772 | stability. |
1807 | stability. |
1773 | |
1808 | |
1774 | FORK |
1809 | FORK |
1775 | 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 |
1776 | 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 |
1777 | 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 |
|
|
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 |
|
|
1819 | the child if the event library was initialised before the fork (which |
|
|
1820 | usually happens when the first AnyEvent watcher is created, or the |
|
|
1821 | library is loaded). |
1778 | |
1822 | |
1779 | 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 |
1780 | 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 |
1781 | 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. |
1782 | |
1835 | |
1783 | SECURITY CONSIDERATIONS |
1836 | SECURITY CONSIDERATIONS |
1784 | AnyEvent can be forced to load any event model via |
1837 | AnyEvent can be forced to load any event model via |
1785 | $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 |
1786 | 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 |