… | |
… | |
15 | my $w = AnyEvent->timer (after => $seconds, cb => sub { |
15 | my $w = AnyEvent->timer (after => $seconds, cb => sub { |
16 | ... |
16 | ... |
17 | }); |
17 | }); |
18 | |
18 | |
19 | my $w = AnyEvent->condvar; # stores whether a condition was flagged |
19 | my $w = AnyEvent->condvar; # stores whether a condition was flagged |
20 | $w->wait; # enters "main loop" till $condvar gets ->broadcast |
20 | $w->wait; # enters "main loop" till $condvar gets ->send |
21 | $w->broadcast; # wake up current and all future wait's |
21 | $w->send; # wake up current and all future wait's |
22 | |
22 | |
23 | =head1 WHY YOU SHOULD USE THIS MODULE (OR NOT) |
23 | =head1 WHY YOU SHOULD USE THIS MODULE (OR NOT) |
24 | |
24 | |
25 | Glib, POE, IO::Async, Event... CPAN offers event models by the dozen |
25 | Glib, POE, IO::Async, Event... CPAN offers event models by the dozen |
26 | nowadays. So what is different about AnyEvent? |
26 | nowadays. So what is different about AnyEvent? |
… | |
… | |
65 | technically possible. |
65 | technically possible. |
66 | |
66 | |
67 | Of course, if you want lots of policy (this can arguably be somewhat |
67 | Of course, if you want lots of policy (this can arguably be somewhat |
68 | useful) and you want to force your users to use the one and only event |
68 | useful) and you want to force your users to use the one and only event |
69 | model, you should I<not> use this module. |
69 | model, you should I<not> use this module. |
70 | |
|
|
71 | |
70 | |
72 | =head1 DESCRIPTION |
71 | =head1 DESCRIPTION |
73 | |
72 | |
74 | L<AnyEvent> provides an identical interface to multiple event loops. This |
73 | L<AnyEvent> provides an identical interface to multiple event loops. This |
75 | allows module authors to utilise an event loop without forcing module |
74 | allows module authors to utilise an event loop without forcing module |
… | |
… | |
289 | my $w = AnyEvent->child ( |
288 | my $w = AnyEvent->child ( |
290 | pid => $pid, |
289 | pid => $pid, |
291 | cb => sub { |
290 | cb => sub { |
292 | my ($pid, $status) = @_; |
291 | my ($pid, $status) = @_; |
293 | warn "pid $pid exited with status $status"; |
292 | warn "pid $pid exited with status $status"; |
294 | $done->broadcast; |
293 | $done->send; |
295 | }, |
294 | }, |
296 | ); |
295 | ); |
297 | |
296 | |
298 | # do something else, then wait for process exit |
297 | # do something else, then wait for process exit |
299 | $done->wait; |
298 | $done->wait; |
300 | |
299 | |
301 | =head2 CONDITION VARIABLES |
300 | =head2 CONDITION VARIABLES |
302 | |
301 | |
|
|
302 | If you are familiar with some event loops you will know that all of them |
|
|
303 | require you to run some blocking "loop", "run" or similar function that |
|
|
304 | will actively watch for new events and call your callbacks. |
|
|
305 | |
|
|
306 | AnyEvent is different, it expects somebody else to run the event loop and |
|
|
307 | will only block when necessary (usually when told by the user). |
|
|
308 | |
|
|
309 | The instrument to do that is called a "condition variable", so called |
|
|
310 | because they represent a condition that must become true. |
|
|
311 | |
303 | Condition variables can be created by calling the C<< AnyEvent->condvar >> |
312 | Condition variables can be created by calling the C<< AnyEvent->condvar |
304 | method without any arguments. |
313 | >> method, usually without arguments. The only argument pair allowed is |
|
|
314 | C<cb>, which specifies a callback to be called when the condition variable |
|
|
315 | becomes true. |
305 | |
316 | |
306 | A condition variable waits for a condition - precisely that the C<< |
317 | After creation, the conditon variable is "false" until it becomes "true" |
307 | ->broadcast >> method has been called. |
318 | by calling the C<send> method. |
308 | |
319 | |
309 | They are very useful to signal that a condition has been fulfilled, for |
320 | Condition variables are similar to callbacks, except that you can |
|
|
321 | optionally wait for them. They can also be called merge points - points |
|
|
322 | in time where multiple outstandign events have been processed. And yet |
|
|
323 | another way to call them is transations - each condition variable can be |
|
|
324 | used to represent a transaction, which finishes at some point and delivers |
|
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325 | a result. |
|
|
326 | |
|
|
327 | Condition variables are very useful to signal that something has finished, |
310 | example, if you write a module that does asynchronous http requests, |
328 | for example, if you write a module that does asynchronous http requests, |
311 | then a condition variable would be the ideal candidate to signal the |
329 | then a condition variable would be the ideal candidate to signal the |
312 | availability of results. |
330 | availability of results. The user can either act when the callback is |
|
|
331 | called or can synchronously C<< ->wait >> for the results. |
313 | |
332 | |
314 | You can also use condition variables to block your main program until |
333 | You can also use them to simulate traditional event loops - for example, |
315 | an event occurs - for example, you could C<< ->wait >> in your main |
334 | you can block your main program until an event occurs - for example, you |
316 | program until the user clicks the Quit button in your app, which would C<< |
335 | could C<< ->wait >> in your main program until the user clicks the Quit |
317 | ->broadcast >> the "quit" event. |
336 | button of your app, which would C<< ->send >> the "quit" event. |
318 | |
337 | |
319 | Note that condition variables recurse into the event loop - if you have |
338 | Note that condition variables recurse into the event loop - if you have |
320 | two pirces of code that call C<< ->wait >> in a round-robbin fashion, you |
339 | two pieces of code that call C<< ->wait >> in a round-robbin fashion, you |
321 | lose. Therefore, condition variables are good to export to your caller, but |
340 | lose. Therefore, condition variables are good to export to your caller, but |
322 | you should avoid making a blocking wait yourself, at least in callbacks, |
341 | you should avoid making a blocking wait yourself, at least in callbacks, |
323 | as this asks for trouble. |
342 | as this asks for trouble. |
324 | |
343 | |
325 | This object has two methods: |
344 | Condition variables are represented by hash refs in perl, and the keys |
|
|
345 | used by AnyEvent itself are all named C<_ae_XXX> to make subclassing |
|
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346 | easy (it is often useful to build your own transaction class on top of |
|
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347 | AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call |
|
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348 | it's C<new> method in your own C<new> method. |
|
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349 | |
|
|
350 | There are two "sides" to a condition variable - the "producer side" which |
|
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351 | eventually calls C<< -> send >>, and the "consumer side", which waits |
|
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352 | for the send to occur. |
|
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353 | |
|
|
354 | Example: |
|
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355 | |
|
|
356 | # wait till the result is ready |
|
|
357 | my $result_ready = AnyEvent->condvar; |
|
|
358 | |
|
|
359 | # do something such as adding a timer |
|
|
360 | # or socket watcher the calls $result_ready->send |
|
|
361 | # when the "result" is ready. |
|
|
362 | # in this case, we simply use a timer: |
|
|
363 | my $w = AnyEvent->timer ( |
|
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364 | after => 1, |
|
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365 | cb => sub { $result_ready->send }, |
|
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366 | ); |
|
|
367 | |
|
|
368 | # this "blocks" (while handling events) till the callback |
|
|
369 | # calls send |
|
|
370 | $result_ready->wait; |
|
|
371 | |
|
|
372 | =head3 METHODS FOR PRODUCERS |
|
|
373 | |
|
|
374 | These methods should only be used by the producing side, i.e. the |
|
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375 | code/module that eventually sends the signal. Note that it is also |
|
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376 | the producer side which creates the condvar in most cases, but it isn't |
|
|
377 | uncommon for the consumer to create it as well. |
326 | |
378 | |
327 | =over 4 |
379 | =over 4 |
328 | |
380 | |
|
|
381 | =item $cv->send (...) |
|
|
382 | |
|
|
383 | Flag the condition as ready - a running C<< ->wait >> and all further |
|
|
384 | calls to C<wait> will (eventually) return after this method has been |
|
|
385 | called. If nobody is waiting the send will be remembered. |
|
|
386 | |
|
|
387 | If a callback has been set on the condition variable, it is called |
|
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388 | immediately from within send. |
|
|
389 | |
|
|
390 | Any arguments passed to the C<send> call will be returned by all |
|
|
391 | future C<< ->wait >> calls. |
|
|
392 | |
|
|
393 | =item $cv->croak ($error) |
|
|
394 | |
|
|
395 | Similar to send, but causes all call's wait C<< ->wait >> to invoke |
|
|
396 | C<Carp::croak> with the given error message/object/scalar. |
|
|
397 | |
|
|
398 | This can be used to signal any errors to the condition variable |
|
|
399 | user/consumer. |
|
|
400 | |
|
|
401 | =item $cv->begin ([group callback]) |
|
|
402 | |
|
|
403 | =item $cv->end |
|
|
404 | |
|
|
405 | These two methods can be used to combine many transactions/events into |
|
|
406 | one. For example, a function that pings many hosts in parallel might want |
|
|
407 | to use a condition variable for the whole process. |
|
|
408 | |
|
|
409 | Every call to C<< ->begin >> will increment a counter, and every call to |
|
|
410 | C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end |
|
|
411 | >>, the (last) callback passed to C<begin> will be executed. That callback |
|
|
412 | is I<supposed> to call C<< ->send >>, but that is not required. If no |
|
|
413 | callback was set, C<send> will be called without any arguments. |
|
|
414 | |
|
|
415 | Let's clarify this with the ping example: |
|
|
416 | |
|
|
417 | my $cv = AnyEvent->condvar; |
|
|
418 | |
|
|
419 | my %result; |
|
|
420 | $cv->begin (sub { $cv->send (\%result) }); |
|
|
421 | |
|
|
422 | for my $host (@list_of_hosts) { |
|
|
423 | $cv->begin; |
|
|
424 | ping_host_then_call_callback $host, sub { |
|
|
425 | $result{$host} = ...; |
|
|
426 | $cv->end; |
|
|
427 | }; |
|
|
428 | } |
|
|
429 | |
|
|
430 | $cv->end; |
|
|
431 | |
|
|
432 | This code fragment supposedly pings a number of hosts and calls |
|
|
433 | C<send> after results for all then have have been gathered - in any |
|
|
434 | order. To achieve this, the code issues a call to C<begin> when it starts |
|
|
435 | each ping request and calls C<end> when it has received some result for |
|
|
436 | it. Since C<begin> and C<end> only maintain a counter, the order in which |
|
|
437 | results arrive is not relevant. |
|
|
438 | |
|
|
439 | There is an additional bracketing call to C<begin> and C<end> outside the |
|
|
440 | loop, which serves two important purposes: first, it sets the callback |
|
|
441 | to be called once the counter reaches C<0>, and second, it ensures that |
|
|
442 | C<send> is called even when C<no> hosts are being pinged (the loop |
|
|
443 | doesn't execute once). |
|
|
444 | |
|
|
445 | This is the general pattern when you "fan out" into multiple subrequests: |
|
|
446 | use an outer C<begin>/C<end> pair to set the callback and ensure C<end> |
|
|
447 | is called at least once, and then, for each subrequest you start, call |
|
|
448 | C<begin> and for eahc subrequest you finish, call C<end>. |
|
|
449 | |
|
|
450 | =back |
|
|
451 | |
|
|
452 | =head3 METHODS FOR CONSUMERS |
|
|
453 | |
|
|
454 | These methods should only be used by the consuming side, i.e. the |
|
|
455 | code awaits the condition. |
|
|
456 | |
|
|
457 | =over 4 |
|
|
458 | |
329 | =item $cv->wait |
459 | =item $cv->wait |
330 | |
460 | |
331 | Wait (blocking if necessary) until the C<< ->broadcast >> method has been |
461 | Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak |
332 | called on c<$cv>, while servicing other watchers normally. |
462 | >> methods have been called on c<$cv>, while servicing other watchers |
|
|
463 | normally. |
333 | |
464 | |
334 | You can only wait once on a condition - additional calls will return |
465 | You can only wait once on a condition - additional calls are valid but |
335 | immediately. |
466 | will return immediately. |
|
|
467 | |
|
|
468 | If an error condition has been set by calling C<< ->croak >>, then this |
|
|
469 | function will call C<croak>. |
|
|
470 | |
|
|
471 | In list context, all parameters passed to C<send> will be returned, |
|
|
472 | in scalar context only the first one will be returned. |
336 | |
473 | |
337 | Not all event models support a blocking wait - some die in that case |
474 | Not all event models support a blocking wait - some die in that case |
338 | (programs might want to do that to stay interactive), so I<if you are |
475 | (programs might want to do that to stay interactive), so I<if you are |
339 | using this from a module, never require a blocking wait>, but let the |
476 | using this from a module, never require a blocking wait>, but let the |
340 | caller decide whether the call will block or not (for example, by coupling |
477 | caller decide whether the call will block or not (for example, by coupling |
… | |
… | |
347 | multiple interpreters or coroutines/threads, none of which C<AnyEvent> |
484 | multiple interpreters or coroutines/threads, none of which C<AnyEvent> |
348 | can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and |
485 | can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and |
349 | L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s |
486 | L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s |
350 | from different coroutines, however). |
487 | from different coroutines, however). |
351 | |
488 | |
352 | =item $cv->broadcast |
489 | You can ensure that C<< -wait >> never blocks by setting a callback and |
|
|
490 | only calling C<< ->wait >> from within that callback (or at a later |
|
|
491 | time). This will work even when the event loop does not support blocking |
|
|
492 | waits otherwise. |
353 | |
493 | |
354 | Flag the condition as ready - a running C<< ->wait >> and all further |
494 | =item $bool = $cv->ready |
355 | calls to C<wait> will (eventually) return after this method has been |
495 | |
356 | called. If nobody is waiting the broadcast will be remembered.. |
496 | Returns true when the condition is "true", i.e. whether C<send> or |
|
|
497 | C<croak> have been called. |
|
|
498 | |
|
|
499 | =item $cb = $cv->cb ([new callback]) |
|
|
500 | |
|
|
501 | This is a mutator function that returns the callback set and optionally |
|
|
502 | replaces it before doing so. |
|
|
503 | |
|
|
504 | The callback will be called when the condition becomes "true", i.e. when |
|
|
505 | C<send> or C<croak> are called. Calling C<wait> inside the callback |
|
|
506 | or at any later time is guaranteed not to block. |
357 | |
507 | |
358 | =back |
508 | =back |
359 | |
|
|
360 | Example: |
|
|
361 | |
|
|
362 | # wait till the result is ready |
|
|
363 | my $result_ready = AnyEvent->condvar; |
|
|
364 | |
|
|
365 | # do something such as adding a timer |
|
|
366 | # or socket watcher the calls $result_ready->broadcast |
|
|
367 | # when the "result" is ready. |
|
|
368 | # in this case, we simply use a timer: |
|
|
369 | my $w = AnyEvent->timer ( |
|
|
370 | after => 1, |
|
|
371 | cb => sub { $result_ready->broadcast }, |
|
|
372 | ); |
|
|
373 | |
|
|
374 | # this "blocks" (while handling events) till the watcher |
|
|
375 | # calls broadcast |
|
|
376 | $result_ready->wait; |
|
|
377 | |
509 | |
378 | =head1 GLOBAL VARIABLES AND FUNCTIONS |
510 | =head1 GLOBAL VARIABLES AND FUNCTIONS |
379 | |
511 | |
380 | =over 4 |
512 | =over 4 |
381 | |
513 | |
… | |
… | |
391 | |
523 | |
392 | AnyEvent::Impl::CoroEV based on Coro::EV, best choice. |
524 | AnyEvent::Impl::CoroEV based on Coro::EV, best choice. |
393 | AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice. |
525 | AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice. |
394 | AnyEvent::Impl::EV based on EV (an interface to libev, best choice). |
526 | AnyEvent::Impl::EV based on EV (an interface to libev, best choice). |
395 | AnyEvent::Impl::Event based on Event, second best choice. |
527 | AnyEvent::Impl::Event based on Event, second best choice. |
|
|
528 | AnyEvent::Impl::Perl pure-perl implementation, fast and portable. |
396 | AnyEvent::Impl::Glib based on Glib, third-best choice. |
529 | AnyEvent::Impl::Glib based on Glib, third-best choice. |
397 | AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable. |
|
|
398 | AnyEvent::Impl::Tk based on Tk, very bad choice. |
530 | AnyEvent::Impl::Tk based on Tk, very bad choice. |
399 | AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs). |
531 | AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs). |
400 | AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse. |
532 | AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse. |
401 | AnyEvent::Impl::POE based on POE, not generic enough for full support. |
533 | AnyEvent::Impl::POE based on POE, not generic enough for full support. |
402 | |
534 | |
… | |
… | |
428 | decide which event module to use as soon as the first method is called, so |
560 | decide which event module to use as soon as the first method is called, so |
429 | by calling AnyEvent in your module body you force the user of your module |
561 | by calling AnyEvent in your module body you force the user of your module |
430 | to load the event module first. |
562 | to load the event module first. |
431 | |
563 | |
432 | Never call C<< ->wait >> on a condition variable unless you I<know> that |
564 | Never call C<< ->wait >> on a condition variable unless you I<know> that |
433 | the C<< ->broadcast >> method has been called on it already. This is |
565 | the C<< ->send >> method has been called on it already. This is |
434 | because it will stall the whole program, and the whole point of using |
566 | because it will stall the whole program, and the whole point of using |
435 | events is to stay interactive. |
567 | events is to stay interactive. |
436 | |
568 | |
437 | It is fine, however, to call C<< ->wait >> when the user of your module |
569 | It is fine, however, to call C<< ->wait >> when the user of your module |
438 | requests it (i.e. if you create a http request object ad have a method |
570 | requests it (i.e. if you create a http request object ad have a method |
… | |
… | |
458 | |
590 | |
459 | You can chose to use a rather inefficient pure-perl implementation by |
591 | You can chose to use a rather inefficient pure-perl implementation by |
460 | loading the C<AnyEvent::Impl::Perl> module, which gives you similar |
592 | loading the C<AnyEvent::Impl::Perl> module, which gives you similar |
461 | behaviour everywhere, but letting AnyEvent chose is generally better. |
593 | behaviour everywhere, but letting AnyEvent chose is generally better. |
462 | |
594 | |
|
|
595 | =head1 OTHER MODULES |
|
|
596 | |
|
|
597 | The following is a non-exhaustive list of additional modules that use |
|
|
598 | AnyEvent and can therefore be mixed easily with other AnyEvent modules |
|
|
599 | in the same program. Some of the modules come with AnyEvent, some are |
|
|
600 | available via CPAN. |
|
|
601 | |
|
|
602 | =over 4 |
|
|
603 | |
|
|
604 | =item L<AnyEvent::Util> |
|
|
605 | |
|
|
606 | Contains various utility functions that replace often-used but blocking |
|
|
607 | functions such as C<inet_aton> by event-/callback-based versions. |
|
|
608 | |
|
|
609 | =item L<AnyEvent::Handle> |
|
|
610 | |
|
|
611 | Provide read and write buffers and manages watchers for reads and writes. |
|
|
612 | |
|
|
613 | =item L<AnyEvent::Socket> |
|
|
614 | |
|
|
615 | Provides a means to do non-blocking connects, accepts etc. |
|
|
616 | |
|
|
617 | =item L<AnyEvent::HTTPD> |
|
|
618 | |
|
|
619 | Provides a simple web application server framework. |
|
|
620 | |
|
|
621 | =item L<AnyEvent::DNS> |
|
|
622 | |
|
|
623 | Provides asynchronous DNS resolver capabilities, beyond what |
|
|
624 | L<AnyEvent::Util> offers. |
|
|
625 | |
|
|
626 | =item L<AnyEvent::FastPing> |
|
|
627 | |
|
|
628 | The fastest ping in the west. |
|
|
629 | |
|
|
630 | =item L<Net::IRC3> |
|
|
631 | |
|
|
632 | AnyEvent based IRC client module family. |
|
|
633 | |
|
|
634 | =item L<Net::XMPP2> |
|
|
635 | |
|
|
636 | AnyEvent based XMPP (Jabber protocol) module family. |
|
|
637 | |
|
|
638 | =item L<Net::FCP> |
|
|
639 | |
|
|
640 | AnyEvent-based implementation of the Freenet Client Protocol, birthplace |
|
|
641 | of AnyEvent. |
|
|
642 | |
|
|
643 | =item L<Event::ExecFlow> |
|
|
644 | |
|
|
645 | High level API for event-based execution flow control. |
|
|
646 | |
|
|
647 | =item L<Coro> |
|
|
648 | |
|
|
649 | Has special support for AnyEvent. |
|
|
650 | |
|
|
651 | =item L<IO::Lambda> |
|
|
652 | |
|
|
653 | The lambda approach to I/O - don't ask, look there. Can use AnyEvent. |
|
|
654 | |
|
|
655 | =item L<IO::AIO> |
|
|
656 | |
|
|
657 | Truly asynchronous I/O, should be in the toolbox of every event |
|
|
658 | programmer. Can be trivially made to use AnyEvent. |
|
|
659 | |
|
|
660 | =item L<BDB> |
|
|
661 | |
|
|
662 | Truly asynchronous Berkeley DB access. Can be trivially made to use |
|
|
663 | AnyEvent. |
|
|
664 | |
|
|
665 | =back |
|
|
666 | |
463 | =cut |
667 | =cut |
464 | |
668 | |
465 | package AnyEvent; |
669 | package AnyEvent; |
466 | |
670 | |
467 | no warnings; |
671 | no warnings; |
… | |
… | |
482 | my @models = ( |
686 | my @models = ( |
483 | [Coro::EV:: => AnyEvent::Impl::CoroEV::], |
687 | [Coro::EV:: => AnyEvent::Impl::CoroEV::], |
484 | [Coro::Event:: => AnyEvent::Impl::CoroEvent::], |
688 | [Coro::Event:: => AnyEvent::Impl::CoroEvent::], |
485 | [EV:: => AnyEvent::Impl::EV::], |
689 | [EV:: => AnyEvent::Impl::EV::], |
486 | [Event:: => AnyEvent::Impl::Event::], |
690 | [Event:: => AnyEvent::Impl::Event::], |
487 | [Glib:: => AnyEvent::Impl::Glib::], |
|
|
488 | [Tk:: => AnyEvent::Impl::Tk::], |
691 | [Tk:: => AnyEvent::Impl::Tk::], |
489 | [Wx:: => AnyEvent::Impl::POE::], |
692 | [Wx:: => AnyEvent::Impl::POE::], |
490 | [Prima:: => AnyEvent::Impl::POE::], |
693 | [Prima:: => AnyEvent::Impl::POE::], |
491 | [AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::], |
694 | [AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::], |
492 | # everything below here will not be autoprobed as the pureperl backend should work everywhere |
695 | # everything below here will not be autoprobed as the pureperl backend should work everywhere |
|
|
696 | [Glib:: => AnyEvent::Impl::Glib::], |
493 | [Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy |
697 | [Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy |
494 | [Qt:: => AnyEvent::Impl::Qt::], # requires special main program |
698 | [Qt:: => AnyEvent::Impl::Qt::], # requires special main program |
495 | [POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza |
699 | [POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza |
496 | ); |
700 | ); |
497 | |
701 | |
498 | our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY); |
702 | our %method = map +($_ => 1), qw(io timer signal child condvar one_event DESTROY); |
499 | |
703 | |
500 | sub detect() { |
704 | sub detect() { |
501 | unless ($MODEL) { |
705 | unless ($MODEL) { |
502 | no strict 'refs'; |
706 | no strict 'refs'; |
503 | |
707 | |
… | |
… | |
894 | }); |
1098 | }); |
895 | |
1099 | |
896 | $quit->wait; |
1100 | $quit->wait; |
897 | |
1101 | |
898 | |
1102 | |
899 | =head1 BENCHMARK |
1103 | =head1 BENCHMARKS |
900 | |
1104 | |
901 | To give you an idea of the performance and overheads that AnyEvent adds |
1105 | To give you an idea of the performance and overheads that AnyEvent adds |
902 | over the event loops themselves (and to give you an impression of the |
1106 | over the event loops themselves and to give you an impression of the speed |
903 | speed of various event loops), here is a benchmark of various supported |
1107 | of various event loops I prepared some benchmarks. |
904 | event models natively and with anyevent. The benchmark creates a lot of |
1108 | |
905 | timers (with a zero timeout) and I/O watchers (watching STDOUT, a pty, to |
1109 | =head2 BENCHMARKING ANYEVENT OVERHEAD |
|
|
1110 | |
|
|
1111 | Here is a benchmark of various supported event models used natively and |
|
|
1112 | through anyevent. The benchmark creates a lot of timers (with a zero |
|
|
1113 | timeout) and I/O watchers (watching STDOUT, a pty, to become writable, |
906 | become writable, which it is), lets them fire exactly once and destroys |
1114 | which it is), lets them fire exactly once and destroys them again. |
907 | them again. |
|
|
908 | |
1115 | |
909 | Rewriting the benchmark to use many different sockets instead of using |
1116 | Source code for this benchmark is found as F<eg/bench> in the AnyEvent |
910 | the same filehandle for all I/O watchers results in a much longer runtime |
1117 | distribution. |
911 | (socket creation is expensive), but qualitatively the same figures, so it |
|
|
912 | was not used. |
|
|
913 | |
1118 | |
914 | =head2 Explanation of the columns |
1119 | =head3 Explanation of the columns |
915 | |
1120 | |
916 | I<watcher> is the number of event watchers created/destroyed. Since |
1121 | I<watcher> is the number of event watchers created/destroyed. Since |
917 | different event models feature vastly different performances, each event |
1122 | different event models feature vastly different performances, each event |
918 | loop was given a number of watchers so that overall runtime is acceptable |
1123 | loop was given a number of watchers so that overall runtime is acceptable |
919 | and similar between tested event loop (and keep them from crashing): Glib |
1124 | and similar between tested event loop (and keep them from crashing): Glib |
… | |
… | |
935 | signal the end of this phase. |
1140 | signal the end of this phase. |
936 | |
1141 | |
937 | I<destroy> is the time, in microseconds, that it takes to destroy a single |
1142 | I<destroy> is the time, in microseconds, that it takes to destroy a single |
938 | watcher. |
1143 | watcher. |
939 | |
1144 | |
940 | =head2 Results |
1145 | =head3 Results |
941 | |
1146 | |
942 | name watchers bytes create invoke destroy comment |
1147 | name watchers bytes create invoke destroy comment |
943 | EV/EV 400000 244 0.56 0.46 0.31 EV native interface |
1148 | EV/EV 400000 244 0.56 0.46 0.31 EV native interface |
944 | EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers |
1149 | EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers |
945 | CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal |
1150 | CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal |
946 | Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation |
1151 | Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation |
947 | Event/Event 16000 516 31.88 31.30 0.85 Event native interface |
1152 | Event/Event 16000 516 31.88 31.30 0.85 Event native interface |
948 | Event/Any 16000 936 39.17 33.63 1.43 Event + AnyEvent watchers |
1153 | Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers |
949 | Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour |
1154 | Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour |
950 | Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers |
1155 | Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers |
951 | POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event |
1156 | POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event |
952 | POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select |
1157 | POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select |
953 | |
1158 | |
954 | =head2 Discussion |
1159 | =head3 Discussion |
955 | |
1160 | |
956 | The benchmark does I<not> measure scalability of the event loop very |
1161 | The benchmark does I<not> measure scalability of the event loop very |
957 | well. For example, a select-based event loop (such as the pure perl one) |
1162 | well. For example, a select-based event loop (such as the pure perl one) |
958 | can never compete with an event loop that uses epoll when the number of |
1163 | can never compete with an event loop that uses epoll when the number of |
959 | file descriptors grows high. In this benchmark, all events become ready at |
1164 | file descriptors grows high. In this benchmark, all events become ready at |
960 | the same time, so select/poll-based implementations get an unnatural speed |
1165 | the same time, so select/poll-based implementations get an unnatural speed |
961 | boost. |
1166 | boost. |
962 | |
1167 | |
|
|
1168 | Also, note that the number of watchers usually has a nonlinear effect on |
|
|
1169 | overall speed, that is, creating twice as many watchers doesn't take twice |
|
|
1170 | the time - usually it takes longer. This puts event loops tested with a |
|
|
1171 | higher number of watchers at a disadvantage. |
|
|
1172 | |
|
|
1173 | To put the range of results into perspective, consider that on the |
|
|
1174 | benchmark machine, handling an event takes roughly 1600 CPU cycles with |
|
|
1175 | EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU |
|
|
1176 | cycles with POE. |
|
|
1177 | |
963 | C<EV> is the sole leader regarding speed and memory use, which are both |
1178 | C<EV> is the sole leader regarding speed and memory use, which are both |
964 | maximal/minimal, respectively. Even when going through AnyEvent, it uses |
1179 | maximal/minimal, respectively. Even when going through AnyEvent, it uses |
965 | far less memory than any other event loop and is still faster than Event |
1180 | far less memory than any other event loop and is still faster than Event |
966 | natively. |
1181 | natively. |
967 | |
1182 | |
968 | The pure perl implementation is hit in a few sweet spots (both the |
1183 | The pure perl implementation is hit in a few sweet spots (both the |
969 | zero timeout and the use of a single fd hit optimisations in the perl |
1184 | constant timeout and the use of a single fd hit optimisations in the perl |
970 | interpreter and the backend itself, and all watchers become ready at the |
1185 | interpreter and the backend itself). Nevertheless this shows that it |
971 | same time). Nevertheless this shows that it adds very little overhead in |
1186 | adds very little overhead in itself. Like any select-based backend its |
972 | itself. Like any select-based backend its performance becomes really bad |
1187 | performance becomes really bad with lots of file descriptors (and few of |
973 | with lots of file descriptors (and few of them active), of course, but |
1188 | them active), of course, but this was not subject of this benchmark. |
974 | this was not subject of this benchmark. |
|
|
975 | |
1189 | |
976 | The C<Event> module has a relatively high setup and callback invocation cost, |
1190 | The C<Event> module has a relatively high setup and callback invocation |
977 | but overall scores on the third place. |
1191 | cost, but overall scores in on the third place. |
978 | |
1192 | |
979 | C<Glib>'s memory usage is quite a bit bit higher, but it features a |
1193 | C<Glib>'s memory usage is quite a bit higher, but it features a |
980 | faster callback invocation and overall ends up in the same class as |
1194 | faster callback invocation and overall ends up in the same class as |
981 | C<Event>. However, Glib scales extremely badly, doubling the number of |
1195 | C<Event>. However, Glib scales extremely badly, doubling the number of |
982 | watchers increases the processing time by more than a factor of four, |
1196 | watchers increases the processing time by more than a factor of four, |
983 | making it completely unusable when using larger numbers of watchers |
1197 | making it completely unusable when using larger numbers of watchers |
984 | (note that only a single file descriptor was used in the benchmark, so |
1198 | (note that only a single file descriptor was used in the benchmark, so |
… | |
… | |
987 | The C<Tk> adaptor works relatively well. The fact that it crashes with |
1201 | The C<Tk> adaptor works relatively well. The fact that it crashes with |
988 | more than 2000 watchers is a big setback, however, as correctness takes |
1202 | more than 2000 watchers is a big setback, however, as correctness takes |
989 | precedence over speed. Nevertheless, its performance is surprising, as the |
1203 | precedence over speed. Nevertheless, its performance is surprising, as the |
990 | file descriptor is dup()ed for each watcher. This shows that the dup() |
1204 | file descriptor is dup()ed for each watcher. This shows that the dup() |
991 | employed by some adaptors is not a big performance issue (it does incur a |
1205 | employed by some adaptors is not a big performance issue (it does incur a |
992 | hidden memory cost inside the kernel, though, that is not reflected in the |
1206 | hidden memory cost inside the kernel which is not reflected in the figures |
993 | figures above). |
1207 | above). |
994 | |
1208 | |
995 | C<POE>, regardless of underlying event loop (wether using its pure perl |
1209 | C<POE>, regardless of underlying event loop (whether using its pure perl |
996 | select-based backend or the Event module) shows abysmal performance and |
1210 | select-based backend or the Event module, the POE-EV backend couldn't |
|
|
1211 | be tested because it wasn't working) shows abysmal performance and |
997 | memory usage: Watchers use almost 30 times as much memory as EV watchers, |
1212 | memory usage with AnyEvent: Watchers use almost 30 times as much memory |
998 | and 10 times as much memory as both Event or EV via AnyEvent. Watcher |
1213 | as EV watchers, and 10 times as much memory as Event (the high memory |
|
|
1214 | requirements are caused by requiring a session for each watcher). Watcher |
999 | invocation is almost 900 times slower than with AnyEvent's pure perl |
1215 | invocation speed is almost 900 times slower than with AnyEvent's pure perl |
|
|
1216 | implementation. |
|
|
1217 | |
1000 | implementation. The design of the POE adaptor class in AnyEvent can not |
1218 | The design of the POE adaptor class in AnyEvent can not really account |
1001 | really account for this, as session creation overhead is small compared |
1219 | for the performance issues, though, as session creation overhead is |
1002 | to execution of the state machine, which is coded pretty optimally within |
1220 | small compared to execution of the state machine, which is coded pretty |
1003 | L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow. |
1221 | optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that |
|
|
1222 | using multiple sessions is not a good approach, especially regarding |
|
|
1223 | memory usage, even the author of POE could not come up with a faster |
|
|
1224 | design). |
1004 | |
1225 | |
1005 | =head2 Summary |
1226 | =head3 Summary |
1006 | |
1227 | |
|
|
1228 | =over 4 |
|
|
1229 | |
1007 | Using EV through AnyEvent is faster than any other event loop, but most |
1230 | =item * Using EV through AnyEvent is faster than any other event loop |
1008 | event loops have acceptable performance with or without AnyEvent. |
1231 | (even when used without AnyEvent), but most event loops have acceptable |
|
|
1232 | performance with or without AnyEvent. |
1009 | |
1233 | |
1010 | The overhead AnyEvent adds is usually much smaller than the overhead of |
1234 | =item * The overhead AnyEvent adds is usually much smaller than the overhead of |
1011 | the actual event loop, only with extremely fast event loops such as the EV |
1235 | the actual event loop, only with extremely fast event loops such as EV |
1012 | adds AnyEvent significant overhead. |
1236 | adds AnyEvent significant overhead. |
1013 | |
1237 | |
1014 | And you should simply avoid POE like the plague if you want performance or |
1238 | =item * You should avoid POE like the plague if you want performance or |
1015 | reasonable memory usage. |
1239 | reasonable memory usage. |
1016 | |
1240 | |
|
|
1241 | =back |
|
|
1242 | |
|
|
1243 | =head2 BENCHMARKING THE LARGE SERVER CASE |
|
|
1244 | |
|
|
1245 | This benchmark atcually benchmarks the event loop itself. It works by |
|
|
1246 | creating a number of "servers": each server consists of a socketpair, a |
|
|
1247 | timeout watcher that gets reset on activity (but never fires), and an I/O |
|
|
1248 | watcher waiting for input on one side of the socket. Each time the socket |
|
|
1249 | watcher reads a byte it will write that byte to a random other "server". |
|
|
1250 | |
|
|
1251 | The effect is that there will be a lot of I/O watchers, only part of which |
|
|
1252 | are active at any one point (so there is a constant number of active |
|
|
1253 | fds for each loop iterstaion, but which fds these are is random). The |
|
|
1254 | timeout is reset each time something is read because that reflects how |
|
|
1255 | most timeouts work (and puts extra pressure on the event loops). |
|
|
1256 | |
|
|
1257 | In this benchmark, we use 10000 socketpairs (20000 sockets), of which 100 |
|
|
1258 | (1%) are active. This mirrors the activity of large servers with many |
|
|
1259 | connections, most of which are idle at any one point in time. |
|
|
1260 | |
|
|
1261 | Source code for this benchmark is found as F<eg/bench2> in the AnyEvent |
|
|
1262 | distribution. |
|
|
1263 | |
|
|
1264 | =head3 Explanation of the columns |
|
|
1265 | |
|
|
1266 | I<sockets> is the number of sockets, and twice the number of "servers" (as |
|
|
1267 | each server has a read and write socket end). |
|
|
1268 | |
|
|
1269 | I<create> is the time it takes to create a socketpair (which is |
|
|
1270 | nontrivial) and two watchers: an I/O watcher and a timeout watcher. |
|
|
1271 | |
|
|
1272 | I<request>, the most important value, is the time it takes to handle a |
|
|
1273 | single "request", that is, reading the token from the pipe and forwarding |
|
|
1274 | it to another server. This includes deleting the old timeout and creating |
|
|
1275 | a new one that moves the timeout into the future. |
|
|
1276 | |
|
|
1277 | =head3 Results |
|
|
1278 | |
|
|
1279 | name sockets create request |
|
|
1280 | EV 20000 69.01 11.16 |
|
|
1281 | Perl 20000 73.32 35.87 |
|
|
1282 | Event 20000 212.62 257.32 |
|
|
1283 | Glib 20000 651.16 1896.30 |
|
|
1284 | POE 20000 349.67 12317.24 uses POE::Loop::Event |
|
|
1285 | |
|
|
1286 | =head3 Discussion |
|
|
1287 | |
|
|
1288 | This benchmark I<does> measure scalability and overall performance of the |
|
|
1289 | particular event loop. |
|
|
1290 | |
|
|
1291 | EV is again fastest. Since it is using epoll on my system, the setup time |
|
|
1292 | is relatively high, though. |
|
|
1293 | |
|
|
1294 | Perl surprisingly comes second. It is much faster than the C-based event |
|
|
1295 | loops Event and Glib. |
|
|
1296 | |
|
|
1297 | Event suffers from high setup time as well (look at its code and you will |
|
|
1298 | understand why). Callback invocation also has a high overhead compared to |
|
|
1299 | the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event |
|
|
1300 | uses select or poll in basically all documented configurations. |
|
|
1301 | |
|
|
1302 | Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It |
|
|
1303 | clearly fails to perform with many filehandles or in busy servers. |
|
|
1304 | |
|
|
1305 | POE is still completely out of the picture, taking over 1000 times as long |
|
|
1306 | as EV, and over 100 times as long as the Perl implementation, even though |
|
|
1307 | it uses a C-based event loop in this case. |
|
|
1308 | |
|
|
1309 | =head3 Summary |
|
|
1310 | |
|
|
1311 | =over 4 |
|
|
1312 | |
|
|
1313 | =item * The pure perl implementation performs extremely well. |
|
|
1314 | |
|
|
1315 | =item * Avoid Glib or POE in large projects where performance matters. |
|
|
1316 | |
|
|
1317 | =back |
|
|
1318 | |
|
|
1319 | =head2 BENCHMARKING SMALL SERVERS |
|
|
1320 | |
|
|
1321 | While event loops should scale (and select-based ones do not...) even to |
|
|
1322 | large servers, most programs we (or I :) actually write have only a few |
|
|
1323 | I/O watchers. |
|
|
1324 | |
|
|
1325 | In this benchmark, I use the same benchmark program as in the large server |
|
|
1326 | case, but it uses only eight "servers", of which three are active at any |
|
|
1327 | one time. This should reflect performance for a small server relatively |
|
|
1328 | well. |
|
|
1329 | |
|
|
1330 | The columns are identical to the previous table. |
|
|
1331 | |
|
|
1332 | =head3 Results |
|
|
1333 | |
|
|
1334 | name sockets create request |
|
|
1335 | EV 16 20.00 6.54 |
|
|
1336 | Perl 16 25.75 12.62 |
|
|
1337 | Event 16 81.27 35.86 |
|
|
1338 | Glib 16 32.63 15.48 |
|
|
1339 | POE 16 261.87 276.28 uses POE::Loop::Event |
|
|
1340 | |
|
|
1341 | =head3 Discussion |
|
|
1342 | |
|
|
1343 | The benchmark tries to test the performance of a typical small |
|
|
1344 | server. While knowing how various event loops perform is interesting, keep |
|
|
1345 | in mind that their overhead in this case is usually not as important, due |
|
|
1346 | to the small absolute number of watchers (that is, you need efficiency and |
|
|
1347 | speed most when you have lots of watchers, not when you only have a few of |
|
|
1348 | them). |
|
|
1349 | |
|
|
1350 | EV is again fastest. |
|
|
1351 | |
|
|
1352 | Perl again comes second. It is noticably faster than the C-based event |
|
|
1353 | loops Event and Glib, although the difference is too small to really |
|
|
1354 | matter. |
|
|
1355 | |
|
|
1356 | POE also performs much better in this case, but is is still far behind the |
|
|
1357 | others. |
|
|
1358 | |
|
|
1359 | =head3 Summary |
|
|
1360 | |
|
|
1361 | =over 4 |
|
|
1362 | |
|
|
1363 | =item * C-based event loops perform very well with small number of |
|
|
1364 | watchers, as the management overhead dominates. |
|
|
1365 | |
|
|
1366 | =back |
|
|
1367 | |
1017 | |
1368 | |
1018 | =head1 FORK |
1369 | =head1 FORK |
1019 | |
1370 | |
1020 | Most event libraries are not fork-safe. The ones who are usually are |
1371 | Most event libraries are not fork-safe. The ones who are usually are |
1021 | because they are so inefficient. Only L<EV> is fully fork-aware. |
1372 | because they rely on inefficient but fork-safe C<select> or C<poll> |
|
|
1373 | calls. Only L<EV> is fully fork-aware. |
1022 | |
1374 | |
1023 | If you have to fork, you must either do so I<before> creating your first |
1375 | If you have to fork, you must either do so I<before> creating your first |
1024 | watcher OR you must not use AnyEvent at all in the child. |
1376 | watcher OR you must not use AnyEvent at all in the child. |
1025 | |
1377 | |
1026 | |
1378 | |