1 | NAME |
1 | NAME |
2 | AnyEvent - provide framework for multiple event loops |
2 | AnyEvent - provide framework for multiple event loops |
3 | |
3 | |
4 | EV, Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event |
4 | EV, Event, Glib, Tk, Perl, Event::Lib, Qt and POE are various supported |
5 | loops |
5 | event loops. |
6 | |
6 | |
7 | SYNOPSIS |
7 | SYNOPSIS |
8 | use AnyEvent; |
8 | use AnyEvent; |
9 | |
9 | |
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10 | # file descriptor readable |
10 | my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub { ... }); |
11 | my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... }); |
11 | |
12 | |
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13 | # one-shot or repeating timers |
12 | my $w = AnyEvent->timer (after => $seconds, cb => sub { ... }); |
14 | my $w = AnyEvent->timer (after => $seconds, cb => sub { ... }); |
13 | my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ... |
15 | my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ... |
14 | |
16 | |
15 | print AnyEvent->now; # prints current event loop time |
17 | print AnyEvent->now; # prints current event loop time |
16 | print AnyEvent->time; # think Time::HiRes::time or simply CORE::time. |
18 | print AnyEvent->time; # think Time::HiRes::time or simply CORE::time. |
17 | |
19 | |
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20 | # POSIX signal |
18 | my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... }); |
21 | my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... }); |
19 | |
22 | |
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23 | # child process exit |
20 | my $w = AnyEvent->child (pid => $pid, cb => sub { |
24 | my $w = AnyEvent->child (pid => $pid, cb => sub { |
21 | my ($pid, $status) = @_; |
25 | my ($pid, $status) = @_; |
22 | ... |
26 | ... |
23 | }); |
27 | }); |
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28 | |
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29 | # called when event loop idle (if applicable) |
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30 | my $w = AnyEvent->idle (cb => sub { ... }); |
24 | |
31 | |
25 | my $w = AnyEvent->condvar; # stores whether a condition was flagged |
32 | my $w = AnyEvent->condvar; # stores whether a condition was flagged |
26 | $w->send; # wake up current and all future recv's |
33 | $w->send; # wake up current and all future recv's |
27 | $w->recv; # enters "main loop" till $condvar gets ->send |
34 | $w->recv; # enters "main loop" till $condvar gets ->send |
28 | # use a condvar in callback mode: |
35 | # use a condvar in callback mode: |
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132 | These watchers are normal Perl objects with normal Perl lifetime. After |
139 | These watchers are normal Perl objects with normal Perl lifetime. After |
133 | creating a watcher it will immediately "watch" for events and invoke the |
140 | creating a watcher it will immediately "watch" for events and invoke the |
134 | callback when the event occurs (of course, only when the event model is |
141 | callback when the event occurs (of course, only when the event model is |
135 | in control). |
142 | in control). |
136 | |
143 | |
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144 | Note that callbacks must not permanently change global variables |
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145 | potentially in use by the event loop (such as $_ or $[) and that |
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146 | callbacks must not "die". The former is good programming practise in |
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147 | Perl and the latter stems from the fact that exception handling differs |
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148 | widely between event loops. |
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149 | |
137 | To disable the watcher you have to destroy it (e.g. by setting the |
150 | To disable the watcher you have to destroy it (e.g. by setting the |
138 | variable you store it in to "undef" or otherwise deleting all references |
151 | variable you store it in to "undef" or otherwise deleting all references |
139 | to it). |
152 | to it). |
140 | |
153 | |
141 | All watchers are created by calling a method on the "AnyEvent" class. |
154 | All watchers are created by calling a method on the "AnyEvent" class. |
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156 | |
169 | |
157 | I/O WATCHERS |
170 | I/O WATCHERS |
158 | You can create an I/O watcher by calling the "AnyEvent->io" method with |
171 | You can create an I/O watcher by calling the "AnyEvent->io" method with |
159 | the following mandatory key-value pairs as arguments: |
172 | the following mandatory key-value pairs as arguments: |
160 | |
173 | |
161 | "fh" the Perl *file handle* (*not* file descriptor) to watch for events |
174 | "fh" is the Perl *file handle* (*not* file descriptor) to watch for |
162 | (AnyEvent might or might not keep a reference to this file handle). |
175 | events (AnyEvent might or might not keep a reference to this file |
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176 | handle). Note that only file handles pointing to things for which |
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177 | non-blocking operation makes sense are allowed. This includes sockets, |
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178 | most character devices, pipes, fifos and so on, but not for example |
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179 | files or block devices. |
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180 | |
163 | "poll" must be a string that is either "r" or "w", which creates a |
181 | "poll" must be a string that is either "r" or "w", which creates a |
164 | watcher waiting for "r"eadable or "w"ritable events, respectively. "cb" |
182 | watcher waiting for "r"eadable or "w"ritable events, respectively. |
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183 | |
165 | is the callback to invoke each time the file handle becomes ready. |
184 | "cb" is the callback to invoke each time the file handle becomes ready. |
166 | |
185 | |
167 | Although the callback might get passed parameters, their value and |
186 | Although the callback might get passed parameters, their value and |
168 | presence is undefined and you cannot rely on them. Portable AnyEvent |
187 | presence is undefined and you cannot rely on them. Portable AnyEvent |
169 | callbacks cannot use arguments passed to I/O watcher callbacks. |
188 | callbacks cannot use arguments passed to I/O watcher callbacks. |
170 | |
189 | |
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302 | In either case, if you care (and in most cases, you don't), then you |
321 | In either case, if you care (and in most cases, you don't), then you |
303 | can get whatever behaviour you want with any event loop, by taking |
322 | can get whatever behaviour you want with any event loop, by taking |
304 | the difference between "AnyEvent->time" and "AnyEvent->now" into |
323 | the difference between "AnyEvent->time" and "AnyEvent->now" into |
305 | account. |
324 | account. |
306 | |
325 | |
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326 | AnyEvent->now_update |
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327 | Some event loops (such as EV or AnyEvent::Impl::Perl) cache the |
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328 | current time for each loop iteration (see the discussion of |
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329 | AnyEvent->now, above). |
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330 | |
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331 | When a callback runs for a long time (or when the process sleeps), |
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332 | then this "current" time will differ substantially from the real |
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333 | time, which might affect timers and time-outs. |
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334 | |
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335 | When this is the case, you can call this method, which will update |
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336 | the event loop's idea of "current time". |
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337 | |
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338 | Note that updating the time *might* cause some events to be handled. |
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339 | |
307 | SIGNAL WATCHERS |
340 | SIGNAL WATCHERS |
308 | You can watch for signals using a signal watcher, "signal" is the signal |
341 | You can watch for signals using a signal watcher, "signal" is the signal |
309 | *name* in uppercase and without any "SIG" prefix, "cb" is the Perl |
342 | *name* in uppercase and without any "SIG" prefix, "cb" is the Perl |
310 | callback to be invoked whenever a signal occurs. |
343 | callback to be invoked whenever a signal occurs. |
311 | |
344 | |
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330 | |
363 | |
331 | CHILD PROCESS WATCHERS |
364 | CHILD PROCESS WATCHERS |
332 | You can also watch on a child process exit and catch its exit status. |
365 | You can also watch on a child process exit and catch its exit status. |
333 | |
366 | |
334 | The child process is specified by the "pid" argument (if set to 0, it |
367 | The child process is specified by the "pid" argument (if set to 0, it |
335 | watches for any child process exit). The watcher will trigger as often |
368 | watches for any child process exit). The watcher will triggered only |
336 | as status change for the child are received. This works by installing a |
369 | when the child process has finished and an exit status is available, not |
337 | signal handler for "SIGCHLD". The callback will be called with the pid |
370 | on any trace events (stopped/continued). |
338 | and exit status (as returned by waitpid), so unlike other watcher types, |
371 | |
339 | you *can* rely on child watcher callback arguments. |
372 | The callback will be called with the pid and exit status (as returned by |
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373 | waitpid), so unlike other watcher types, you *can* rely on child watcher |
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374 | callback arguments. |
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375 | |
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376 | This watcher type works by installing a signal handler for "SIGCHLD", |
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377 | and since it cannot be shared, nothing else should use SIGCHLD or reap |
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378 | random child processes (waiting for specific child processes, e.g. |
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379 | inside "system", is just fine). |
340 | |
380 | |
341 | There is a slight catch to child watchers, however: you usually start |
381 | There is a slight catch to child watchers, however: you usually start |
342 | them *after* the child process was created, and this means the process |
382 | them *after* the child process was created, and this means the process |
343 | could have exited already (and no SIGCHLD will be sent anymore). |
383 | could have exited already (and no SIGCHLD will be sent anymore). |
344 | |
384 | |
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352 | you "fork" the child (alternatively, you can call "AnyEvent::detect"). |
392 | you "fork" the child (alternatively, you can call "AnyEvent::detect"). |
353 | |
393 | |
354 | Example: fork a process and wait for it |
394 | Example: fork a process and wait for it |
355 | |
395 | |
356 | my $done = AnyEvent->condvar; |
396 | my $done = AnyEvent->condvar; |
357 | |
397 | |
358 | my $pid = fork or exit 5; |
398 | my $pid = fork or exit 5; |
359 | |
399 | |
360 | my $w = AnyEvent->child ( |
400 | my $w = AnyEvent->child ( |
361 | pid => $pid, |
401 | pid => $pid, |
362 | cb => sub { |
402 | cb => sub { |
363 | my ($pid, $status) = @_; |
403 | my ($pid, $status) = @_; |
364 | warn "pid $pid exited with status $status"; |
404 | warn "pid $pid exited with status $status"; |
365 | $done->send; |
405 | $done->send; |
366 | }, |
406 | }, |
367 | ); |
407 | ); |
368 | |
408 | |
369 | # do something else, then wait for process exit |
409 | # do something else, then wait for process exit |
370 | $done->recv; |
410 | $done->recv; |
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411 | |
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412 | IDLE WATCHERS |
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413 | Sometimes there is a need to do something, but it is not so important to |
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414 | do it instantly, but only when there is nothing better to do. This |
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415 | "nothing better to do" is usually defined to be "no other events need |
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416 | attention by the event loop". |
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417 | |
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418 | Idle watchers ideally get invoked when the event loop has nothing better |
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419 | to do, just before it would block the process to wait for new events. |
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420 | Instead of blocking, the idle watcher is invoked. |
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421 | |
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422 | Most event loops unfortunately do not really support idle watchers (only |
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423 | EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent |
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424 | will simply call the callback "from time to time". |
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425 | |
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426 | Example: read lines from STDIN, but only process them when the program |
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427 | is otherwise idle: |
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428 | |
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429 | my @lines; # read data |
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430 | my $idle_w; |
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431 | my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub { |
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432 | push @lines, scalar <STDIN>; |
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433 | |
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434 | # start an idle watcher, if not already done |
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435 | $idle_w ||= AnyEvent->idle (cb => sub { |
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436 | # handle only one line, when there are lines left |
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437 | if (my $line = shift @lines) { |
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438 | print "handled when idle: $line"; |
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439 | } else { |
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440 | # otherwise disable the idle watcher again |
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441 | undef $idle_w; |
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442 | } |
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443 | }); |
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444 | }); |
371 | |
445 | |
372 | CONDITION VARIABLES |
446 | CONDITION VARIABLES |
373 | If you are familiar with some event loops you will know that all of them |
447 | If you are familiar with some event loops you will know that all of them |
374 | require you to run some blocking "loop", "run" or similar function that |
448 | require you to run some blocking "loop", "run" or similar function that |
375 | will actively watch for new events and call your callbacks. |
449 | will actively watch for new events and call your callbacks. |
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770 | |
844 | |
771 | AnyEvent::IGS |
845 | AnyEvent::IGS |
772 | A non-blocking interface to the Internet Go Server protocol (used by |
846 | A non-blocking interface to the Internet Go Server protocol (used by |
773 | App::IGS). |
847 | App::IGS). |
774 | |
848 | |
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849 | AnyEvent::IRC |
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850 | AnyEvent based IRC client module family (replacing the older |
775 | Net::IRC3 |
851 | Net::IRC3). |
776 | AnyEvent based IRC client module family. |
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777 | |
852 | |
778 | Net::XMPP2 |
853 | Net::XMPP2 |
779 | AnyEvent based XMPP (Jabber protocol) module family. |
854 | AnyEvent based XMPP (Jabber protocol) module family. |
780 | |
855 | |
781 | Net::FCP |
856 | Net::FCP |
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790 | |
865 | |
791 | IO::Lambda |
866 | IO::Lambda |
792 | The lambda approach to I/O - don't ask, look there. Can use |
867 | The lambda approach to I/O - don't ask, look there. Can use |
793 | AnyEvent. |
868 | AnyEvent. |
794 | |
869 | |
795 | SUPPLYING YOUR OWN EVENT MODEL INTERFACE |
870 | ERROR AND EXCEPTION HANDLING |
796 | This is an advanced topic that you do not normally need to use AnyEvent |
871 | In general, AnyEvent does not do any error handling - it relies on the |
797 | in a module. This section is only of use to event loop authors who want |
872 | caller to do that if required. The AnyEvent::Strict module (see also the |
798 | to provide AnyEvent compatibility. |
873 | "PERL_ANYEVENT_STRICT" environment variable, below) provides strict |
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874 | checking of all AnyEvent methods, however, which is highly useful during |
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875 | development. |
799 | |
876 | |
800 | If you need to support another event library which isn't directly |
877 | As for exception handling (i.e. runtime errors and exceptions thrown |
801 | supported by AnyEvent, you can supply your own interface to it by |
878 | while executing a callback), this is not only highly event-loop |
802 | pushing, before the first watcher gets created, the package name of the |
879 | specific, but also not in any way wrapped by this module, as this is the |
803 | event module and the package name of the interface to use onto |
880 | job of the main program. |
804 | @AnyEvent::REGISTRY. You can do that before and even without loading |
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805 | AnyEvent, so it is reasonably cheap. |
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806 | |
881 | |
807 | Example: |
882 | The pure perl event loop simply re-throws the exception (usually within |
808 | |
883 | "condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()", |
809 | push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::]; |
884 | Glib uses "install_exception_handler" and so on. |
810 | |
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811 | This tells AnyEvent to (literally) use the "urxvt::anyevent::" |
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812 | package/class when it finds the "urxvt" package/module is already |
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813 | loaded. |
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814 | |
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815 | When AnyEvent is loaded and asked to find a suitable event model, it |
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816 | will first check for the presence of urxvt by trying to "use" the |
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817 | "urxvt::anyevent" module. |
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818 | |
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819 | The class should provide implementations for all watcher types. See |
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820 | AnyEvent::Impl::EV (source code), AnyEvent::Impl::Glib (Source code) and |
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821 | so on for actual examples. Use "perldoc -m AnyEvent::Impl::Glib" to see |
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822 | the sources. |
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823 | |
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824 | If you don't provide "signal" and "child" watchers than AnyEvent will |
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825 | provide suitable (hopefully) replacements. |
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826 | |
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827 | The above example isn't fictitious, the *rxvt-unicode* (a.k.a. urxvt) |
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828 | terminal emulator uses the above line as-is. An interface isn't included |
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829 | in AnyEvent because it doesn't make sense outside the embedded |
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830 | interpreter inside *rxvt-unicode*, and it is updated and maintained as |
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831 | part of the *rxvt-unicode* distribution. |
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832 | |
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833 | *rxvt-unicode* also cheats a bit by not providing blocking access to |
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834 | condition variables: code blocking while waiting for a condition will |
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835 | "die". This still works with most modules/usages, and blocking calls |
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836 | must not be done in an interactive application, so it makes sense. |
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837 | |
885 | |
838 | ENVIRONMENT VARIABLES |
886 | ENVIRONMENT VARIABLES |
839 | The following environment variables are used by this module: |
887 | The following environment variables are used by this module or its |
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888 | submodules. |
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889 | |
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890 | Note that AnyEvent will remove *all* environment variables starting with |
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891 | "PERL_ANYEVENT_" from %ENV when it is loaded while taint mode is |
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892 | enabled. |
840 | |
893 | |
841 | "PERL_ANYEVENT_VERBOSE" |
894 | "PERL_ANYEVENT_VERBOSE" |
842 | By default, AnyEvent will be completely silent except in fatal |
895 | By default, AnyEvent will be completely silent except in fatal |
843 | conditions. You can set this environment variable to make AnyEvent |
896 | conditions. You can set this environment variable to make AnyEvent |
844 | more talkative. |
897 | more talkative. |
… | |
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857 | thoroughly check the arguments passed to most method calls. If it |
910 | thoroughly check the arguments passed to most method calls. If it |
858 | finds any problems it will croak. |
911 | finds any problems it will croak. |
859 | |
912 | |
860 | In other words, enables "strict" mode. |
913 | In other words, enables "strict" mode. |
861 | |
914 | |
862 | Unlike "use strict" it is definitely recommended ot keep it off in |
915 | Unlike "use strict", it is definitely recommended ot keep it off in |
863 | production. |
916 | production. Keeping "PERL_ANYEVENT_STRICT=1" in your environment |
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917 | while developing programs can be very useful, however. |
864 | |
918 | |
865 | "PERL_ANYEVENT_MODEL" |
919 | "PERL_ANYEVENT_MODEL" |
866 | This can be used to specify the event model to be used by AnyEvent, |
920 | This can be used to specify the event model to be used by AnyEvent, |
867 | before auto detection and -probing kicks in. It must be a string |
921 | before auto detection and -probing kicks in. It must be a string |
868 | consisting entirely of ASCII letters. The string "AnyEvent::Impl::" |
922 | consisting entirely of ASCII letters. The string "AnyEvent::Impl::" |
… | |
… | |
887 | mentioned will be used, and preference will be given to protocols |
941 | mentioned will be used, and preference will be given to protocols |
888 | mentioned earlier in the list. |
942 | mentioned earlier in the list. |
889 | |
943 | |
890 | This variable can effectively be used for denial-of-service attacks |
944 | This variable can effectively be used for denial-of-service attacks |
891 | against local programs (e.g. when setuid), although the impact is |
945 | against local programs (e.g. when setuid), although the impact is |
892 | likely small, as the program has to handle connection errors |
946 | likely small, as the program has to handle conenction and other |
893 | already- |
947 | failures anyways. |
894 | |
948 | |
895 | Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over |
949 | Examples: "PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6" - prefer IPv4 over |
896 | IPv6, but support both and try to use both. |
950 | IPv6, but support both and try to use both. |
897 | "PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to |
951 | "PERL_ANYEVENT_PROTOCOLS=ipv4" - only support IPv4, never try to |
898 | resolve or contact IPv6 addresses. |
952 | resolve or contact IPv6 addresses. |
… | |
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909 | EDNS0 in its DNS requests. |
963 | EDNS0 in its DNS requests. |
910 | |
964 | |
911 | "PERL_ANYEVENT_MAX_FORKS" |
965 | "PERL_ANYEVENT_MAX_FORKS" |
912 | The maximum number of child processes that |
966 | The maximum number of child processes that |
913 | "AnyEvent::Util::fork_call" will create in parallel. |
967 | "AnyEvent::Util::fork_call" will create in parallel. |
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968 | |
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969 | SUPPLYING YOUR OWN EVENT MODEL INTERFACE |
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970 | This is an advanced topic that you do not normally need to use AnyEvent |
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971 | in a module. This section is only of use to event loop authors who want |
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972 | to provide AnyEvent compatibility. |
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973 | |
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974 | If you need to support another event library which isn't directly |
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975 | supported by AnyEvent, you can supply your own interface to it by |
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976 | pushing, before the first watcher gets created, the package name of the |
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977 | event module and the package name of the interface to use onto |
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978 | @AnyEvent::REGISTRY. You can do that before and even without loading |
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979 | AnyEvent, so it is reasonably cheap. |
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980 | |
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981 | Example: |
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982 | |
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983 | push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::]; |
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984 | |
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985 | This tells AnyEvent to (literally) use the "urxvt::anyevent::" |
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986 | package/class when it finds the "urxvt" package/module is already |
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987 | loaded. |
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988 | |
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989 | When AnyEvent is loaded and asked to find a suitable event model, it |
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990 | will first check for the presence of urxvt by trying to "use" the |
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991 | "urxvt::anyevent" module. |
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992 | |
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993 | The class should provide implementations for all watcher types. See |
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994 | AnyEvent::Impl::EV (source code), AnyEvent::Impl::Glib (Source code) and |
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995 | so on for actual examples. Use "perldoc -m AnyEvent::Impl::Glib" to see |
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996 | the sources. |
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997 | |
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998 | If you don't provide "signal" and "child" watchers than AnyEvent will |
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999 | provide suitable (hopefully) replacements. |
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1000 | |
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1001 | The above example isn't fictitious, the *rxvt-unicode* (a.k.a. urxvt) |
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1002 | terminal emulator uses the above line as-is. An interface isn't included |
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1003 | in AnyEvent because it doesn't make sense outside the embedded |
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1004 | interpreter inside *rxvt-unicode*, and it is updated and maintained as |
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1005 | part of the *rxvt-unicode* distribution. |
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1006 | |
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1007 | *rxvt-unicode* also cheats a bit by not providing blocking access to |
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1008 | condition variables: code blocking while waiting for a condition will |
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1009 | "die". This still works with most modules/usages, and blocking calls |
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1010 | must not be done in an interactive application, so it makes sense. |
914 | |
1011 | |
915 | EXAMPLE PROGRAM |
1012 | EXAMPLE PROGRAM |
916 | The following program uses an I/O watcher to read data from STDIN, a |
1013 | The following program uses an I/O watcher to read data from STDIN, a |
917 | timer to display a message once per second, and a condition variable to |
1014 | timer to display a message once per second, and a condition variable to |
918 | quit the program when the user enters quit: |
1015 | quit the program when the user enters quit: |
… | |
… | |
1105 | *destroy* is the time, in microseconds, that it takes to destroy a |
1202 | *destroy* is the time, in microseconds, that it takes to destroy a |
1106 | single watcher. |
1203 | single watcher. |
1107 | |
1204 | |
1108 | Results |
1205 | Results |
1109 | name watchers bytes create invoke destroy comment |
1206 | name watchers bytes create invoke destroy comment |
1110 | EV/EV 400000 244 0.56 0.46 0.31 EV native interface |
1207 | EV/EV 400000 224 0.47 0.35 0.27 EV native interface |
1111 | EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers |
1208 | EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers |
1112 | CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal |
1209 | CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal |
1113 | Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation |
1210 | Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation |
1114 | Event/Event 16000 516 31.88 31.30 0.85 Event native interface |
1211 | Event/Event 16000 517 32.20 31.80 0.81 Event native interface |
1115 | Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers |
1212 | Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers |
1116 | Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour |
1213 | Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour |
1117 | Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers |
1214 | Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers |
1118 | POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event |
1215 | POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event |
1119 | POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select |
1216 | POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select |
1120 | |
1217 | |
1121 | Discussion |
1218 | Discussion |
1122 | The benchmark does *not* measure scalability of the event loop very |
1219 | The benchmark does *not* measure scalability of the event loop very |
1123 | well. For example, a select-based event loop (such as the pure perl one) |
1220 | well. For example, a select-based event loop (such as the pure perl one) |
1124 | can never compete with an event loop that uses epoll when the number of |
1221 | can never compete with an event loop that uses epoll when the number of |
… | |
… | |
1305 | |
1402 | |
1306 | Summary |
1403 | Summary |
1307 | * C-based event loops perform very well with small number of watchers, |
1404 | * C-based event loops perform very well with small number of watchers, |
1308 | as the management overhead dominates. |
1405 | as the management overhead dominates. |
1309 | |
1406 | |
|
|
1407 | THE IO::Lambda BENCHMARK |
|
|
1408 | Recently I was told about the benchmark in the IO::Lambda manpage, which |
|
|
1409 | could be misinterpreted to make AnyEvent look bad. In fact, the |
|
|
1410 | benchmark simply compares IO::Lambda with POE, and IO::Lambda looks |
|
|
1411 | better (which shouldn't come as a surprise to anybody). As such, the |
|
|
1412 | benchmark is fine, and shows that the AnyEvent backend from IO::Lambda |
|
|
1413 | isn't very optimal. But how would AnyEvent compare when used without the |
|
|
1414 | extra baggage? To explore this, I wrote the equivalent benchmark for |
|
|
1415 | AnyEvent. |
|
|
1416 | |
|
|
1417 | The benchmark itself creates an echo-server, and then, for 500 times, |
|
|
1418 | connects to the echo server, sends a line, waits for the reply, and then |
|
|
1419 | creates the next connection. This is a rather bad benchmark, as it |
|
|
1420 | doesn't test the efficiency of the framework, but it is a benchmark |
|
|
1421 | nevertheless. |
|
|
1422 | |
|
|
1423 | name runtime |
|
|
1424 | Lambda/select 0.330 sec |
|
|
1425 | + optimized 0.122 sec |
|
|
1426 | Lambda/AnyEvent 0.327 sec |
|
|
1427 | + optimized 0.138 sec |
|
|
1428 | Raw sockets/select 0.077 sec |
|
|
1429 | POE/select, components 0.662 sec |
|
|
1430 | POE/select, raw sockets 0.226 sec |
|
|
1431 | POE/select, optimized 0.404 sec |
|
|
1432 | |
|
|
1433 | AnyEvent/select/nb 0.085 sec |
|
|
1434 | AnyEvent/EV/nb 0.068 sec |
|
|
1435 | +state machine 0.134 sec |
|
|
1436 | |
|
|
1437 | The benchmark is also a bit unfair (my fault) - the IO::Lambda |
|
|
1438 | benchmarks actually make blocking connects and use 100% blocking I/O, |
|
|
1439 | defeating the purpose of an event-based solution. All of the newly |
|
|
1440 | written AnyEvent benchmarks use 100% non-blocking connects (using |
|
|
1441 | AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS |
|
|
1442 | resolver), so AnyEvent is at a disadvantage here as non-blocking |
|
|
1443 | connects generally require a lot more bookkeeping and event handling |
|
|
1444 | than blocking connects (which involve a single syscall only). |
|
|
1445 | |
|
|
1446 | The last AnyEvent benchmark additionally uses AnyEvent::Handle, which |
|
|
1447 | offers similar expressive power as POE and IO::Lambda (using |
|
|
1448 | conventional Perl syntax), which means both the echo server and the |
|
|
1449 | client are 100% non-blocking w.r.t. I/O, further placing it at a |
|
|
1450 | disadvantage. |
|
|
1451 | |
|
|
1452 | As you can see, AnyEvent + EV even beats the hand-optimised "raw sockets |
|
|
1453 | benchmark", while AnyEvent + its pure perl backend easily beats |
|
|
1454 | IO::Lambda and POE. |
|
|
1455 | |
|
|
1456 | And even the 100% non-blocking version written using the high-level (and |
|
|
1457 | slow :) AnyEvent::Handle abstraction beats both POE and IO::Lambda, even |
|
|
1458 | thought it does all of DNS, tcp-connect and socket I/O in a non-blocking |
|
|
1459 | way. |
|
|
1460 | |
|
|
1461 | The two AnyEvent benchmarks can be found as eg/ae0.pl and eg/ae2.pl in |
|
|
1462 | the AnyEvent distribution, the remaining benchmarks are part of the |
|
|
1463 | IO::lambda distribution and were used without any changes. |
|
|
1464 | |
|
|
1465 | SIGNALS |
|
|
1466 | AnyEvent currently installs handlers for these signals: |
|
|
1467 | |
|
|
1468 | SIGCHLD |
|
|
1469 | A handler for "SIGCHLD" is installed by AnyEvent's child watcher |
|
|
1470 | emulation for event loops that do not support them natively. Also, |
|
|
1471 | some event loops install a similar handler. |
|
|
1472 | |
|
|
1473 | SIGPIPE |
|
|
1474 | A no-op handler is installed for "SIGPIPE" when $SIG{PIPE} is |
|
|
1475 | "undef" when AnyEvent gets loaded. |
|
|
1476 | |
|
|
1477 | The rationale for this is that AnyEvent users usually do not really |
|
|
1478 | depend on SIGPIPE delivery (which is purely an optimisation for |
|
|
1479 | shell use, or badly-written programs), but "SIGPIPE" can cause |
|
|
1480 | spurious and rare program exits as a lot of people do not expect |
|
|
1481 | "SIGPIPE" when writing to some random socket. |
|
|
1482 | |
|
|
1483 | The rationale for installing a no-op handler as opposed to ignoring |
|
|
1484 | it is that this way, the handler will be restored to defaults on |
|
|
1485 | exec. |
|
|
1486 | |
|
|
1487 | Feel free to install your own handler, or reset it to defaults. |
|
|
1488 | |
1310 | FORK |
1489 | FORK |
1311 | Most event libraries are not fork-safe. The ones who are usually are |
1490 | Most event libraries are not fork-safe. The ones who are usually are |
1312 | because they rely on inefficient but fork-safe "select" or "poll" calls. |
1491 | because they rely on inefficient but fork-safe "select" or "poll" calls. |
1313 | Only EV is fully fork-aware. |
1492 | Only EV is fully fork-aware. |
1314 | |
1493 | |
… | |
… | |
1325 | |
1504 | |
1326 | You can make AnyEvent completely ignore this variable by deleting it |
1505 | You can make AnyEvent completely ignore this variable by deleting it |
1327 | before the first watcher gets created, e.g. with a "BEGIN" block: |
1506 | before the first watcher gets created, e.g. with a "BEGIN" block: |
1328 | |
1507 | |
1329 | BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} } |
1508 | BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} } |
1330 | |
1509 | |
1331 | use AnyEvent; |
1510 | use AnyEvent; |
1332 | |
1511 | |
1333 | Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can |
1512 | Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can |
1334 | be used to probe what backend is used and gain other information (which |
1513 | be used to probe what backend is used and gain other information (which |
1335 | is probably even less useful to an attacker than PERL_ANYEVENT_MODEL), |
1514 | is probably even less useful to an attacker than PERL_ANYEVENT_MODEL), |
1336 | and $ENV{PERL_ANYEGENT_STRICT}. |
1515 | and $ENV{PERL_ANYEVENT_STRICT}. |
1337 | |
1516 | |
1338 | BUGS |
1517 | BUGS |
1339 | Perl 5.8 has numerous memleaks that sometimes hit this module and are |
1518 | Perl 5.8 has numerous memleaks that sometimes hit this module and are |
1340 | hard to work around. If you suffer from memleaks, first upgrade to Perl |
1519 | hard to work around. If you suffer from memleaks, first upgrade to Perl |
1341 | 5.10 and check wether the leaks still show up. (Perl 5.10.0 has other |
1520 | 5.10 and check wether the leaks still show up. (Perl 5.10.0 has other |
1342 | annoying mamleaks, such as leaking on "map" and "grep" but it is usually |
1521 | annoying memleaks, such as leaking on "map" and "grep" but it is usually |
1343 | not as pronounced). |
1522 | not as pronounced). |
1344 | |
1523 | |
1345 | SEE ALSO |
1524 | SEE ALSO |
1346 | Utility functions: AnyEvent::Util. |
1525 | Utility functions: AnyEvent::Util. |
1347 | |
1526 | |