… | |
… | |
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 |
… | |
… | |
141 | =head2 I/O WATCHERS |
140 | =head2 I/O WATCHERS |
142 | |
141 | |
143 | You can create an I/O watcher by calling the C<< AnyEvent->io >> method |
142 | You can create an I/O watcher by calling the C<< AnyEvent->io >> method |
144 | with the following mandatory key-value pairs as arguments: |
143 | with the following mandatory key-value pairs as arguments: |
145 | |
144 | |
146 | C<fh> the Perl I<file handle> (I<not> file descriptor) to watch for |
145 | C<fh> the Perl I<file handle> (I<not> file descriptor) to watch |
147 | events. C<poll> must be a string that is either C<r> or C<w>, which |
146 | for events. C<poll> must be a string that is either C<r> or C<w>, |
148 | creates a watcher waiting for "r"eadable or "w"ritable events, |
147 | which creates a watcher waiting for "r"eadable or "w"ritable events, |
149 | respectively. C<cb> is the callback to invoke each time the file handle |
148 | respectively. C<cb> is the callback to invoke each time the file handle |
150 | becomes ready. |
149 | becomes ready. |
|
|
150 | |
|
|
151 | Although the callback might get passed parameters, their value and |
|
|
152 | presence is undefined and you cannot rely on them. Portable AnyEvent |
|
|
153 | callbacks cannot use arguments passed to I/O watcher callbacks. |
151 | |
154 | |
152 | The I/O watcher might use the underlying file descriptor or a copy of it. |
155 | The I/O watcher might use the underlying file descriptor or a copy of it. |
153 | You must not close a file handle as long as any watcher is active on the |
156 | You must not close a file handle as long as any watcher is active on the |
154 | underlying file descriptor. |
157 | underlying file descriptor. |
155 | |
158 | |
156 | Some event loops issue spurious readyness notifications, so you should |
159 | Some event loops issue spurious readyness notifications, so you should |
157 | always use non-blocking calls when reading/writing from/to your file |
160 | always use non-blocking calls when reading/writing from/to your file |
158 | handles. |
161 | handles. |
159 | |
|
|
160 | Although the callback might get passed parameters, their value and |
|
|
161 | presence is undefined and you cannot rely on them. Portable AnyEvent |
|
|
162 | callbacks cannot use arguments passed to I/O watcher callbacks. |
|
|
163 | |
162 | |
164 | Example: |
163 | Example: |
165 | |
164 | |
166 | # wait for readability of STDIN, then read a line and disable the watcher |
165 | # wait for readability of STDIN, then read a line and disable the watcher |
167 | my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub { |
166 | my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub { |
… | |
… | |
174 | |
173 | |
175 | You can create a time watcher by calling the C<< AnyEvent->timer >> |
174 | You can create a time watcher by calling the C<< AnyEvent->timer >> |
176 | method with the following mandatory arguments: |
175 | method with the following mandatory arguments: |
177 | |
176 | |
178 | C<after> specifies after how many seconds (fractional values are |
177 | C<after> specifies after how many seconds (fractional values are |
179 | supported) should the timer activate. C<cb> the callback to invoke in that |
178 | supported) the callback should be invoked. C<cb> is the callback to invoke |
180 | case. |
179 | in that case. |
|
|
180 | |
|
|
181 | Although the callback might get passed parameters, their value and |
|
|
182 | presence is undefined and you cannot rely on them. Portable AnyEvent |
|
|
183 | callbacks cannot use arguments passed to time watcher callbacks. |
181 | |
184 | |
182 | The timer callback will be invoked at most once: if you want a repeating |
185 | The timer callback will be invoked at most once: if you want a repeating |
183 | timer you have to create a new watcher (this is a limitation by both Tk |
186 | timer you have to create a new watcher (this is a limitation by both Tk |
184 | and Glib). |
187 | and Glib). |
185 | |
|
|
186 | Although the callback might get passed parameters, their value and |
|
|
187 | presence is undefined and you cannot rely on them. Portable AnyEvent |
|
|
188 | callbacks cannot use arguments passed to time watcher callbacks. |
|
|
189 | |
188 | |
190 | Example: |
189 | Example: |
191 | |
190 | |
192 | # fire an event after 7.7 seconds |
191 | # fire an event after 7.7 seconds |
193 | my $w = AnyEvent->timer (after => 7.7, cb => sub { |
192 | my $w = AnyEvent->timer (after => 7.7, cb => sub { |
… | |
… | |
234 | |
233 | |
235 | You can watch for signals using a signal watcher, C<signal> is the signal |
234 | You can watch for signals using a signal watcher, C<signal> is the signal |
236 | I<name> without any C<SIG> prefix, C<cb> is the Perl callback to |
235 | I<name> without any C<SIG> prefix, C<cb> is the Perl callback to |
237 | be invoked whenever a signal occurs. |
236 | be invoked whenever a signal occurs. |
238 | |
237 | |
|
|
238 | Although the callback might get passed parameters, their value and |
|
|
239 | presence is undefined and you cannot rely on them. Portable AnyEvent |
|
|
240 | callbacks cannot use arguments passed to signal watcher callbacks. |
|
|
241 | |
239 | Multiple signal occurances can be clumped together into one callback |
242 | Multiple signal occurances can be clumped together into one callback |
240 | invocation, and callback invocation will be synchronous. synchronous means |
243 | invocation, and callback invocation will be synchronous. synchronous means |
241 | that it might take a while until the signal gets handled by the process, |
244 | that it might take a while until the signal gets handled by the process, |
242 | but it is guarenteed not to interrupt any other callbacks. |
245 | but it is guarenteed not to interrupt any other callbacks. |
243 | |
246 | |
… | |
… | |
257 | |
260 | |
258 | The child process is specified by the C<pid> argument (if set to C<0>, it |
261 | The child process is specified by the C<pid> argument (if set to C<0>, it |
259 | watches for any child process exit). The watcher will trigger as often |
262 | watches for any child process exit). The watcher will trigger as often |
260 | as status change for the child are received. This works by installing a |
263 | as status change for the child are received. This works by installing a |
261 | signal handler for C<SIGCHLD>. The callback will be called with the pid |
264 | signal handler for C<SIGCHLD>. The callback will be called with the pid |
262 | and exit status (as returned by waitpid). |
265 | and exit status (as returned by waitpid), so unlike other watcher types, |
|
|
266 | you I<can> rely on child watcher callback arguments. |
263 | |
267 | |
264 | There is a slight catch to child watchers, however: you usually start them |
268 | There is a slight catch to child watchers, however: you usually start them |
265 | I<after> the child process was created, and this means the process could |
269 | I<after> the child process was created, and this means the process could |
266 | have exited already (and no SIGCHLD will be sent anymore). |
270 | have exited already (and no SIGCHLD will be sent anymore). |
267 | |
271 | |
… | |
… | |
293 | # do something else, then wait for process exit |
297 | # do something else, then wait for process exit |
294 | $done->wait; |
298 | $done->wait; |
295 | |
299 | |
296 | =head2 CONDITION VARIABLES |
300 | =head2 CONDITION VARIABLES |
297 | |
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 | |
298 | Condition variables can be created by calling the C<< AnyEvent->condvar >> |
312 | Condition variables can be created by calling the C<< AnyEvent->condvar |
299 | 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. |
300 | |
316 | |
301 | A condition variable waits for a condition - precisely that the C<< |
317 | After creation, the conditon variable is "false" until it becomes "true" |
302 | ->broadcast >> method has been called. |
318 | by calling the C<broadcast> method. |
303 | |
319 | |
304 | 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 |
|
|
325 | a result. |
|
|
326 | |
|
|
327 | Condition variables are very useful to signal that something has finished, |
305 | example, if you write a module that does asynchronous http requests, |
328 | for example, if you write a module that does asynchronous http requests, |
306 | 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 |
307 | 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. |
308 | |
332 | |
309 | 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, |
310 | 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 |
311 | 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 |
312 | ->broadcast >> the "quit" event. |
336 | button of your app, which would C<< ->broadcast >> the "quit" event. |
313 | |
337 | |
314 | 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 |
315 | 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 |
316 | 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 |
317 | 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, |
318 | as this asks for trouble. |
342 | as this asks for trouble. |
319 | |
343 | |
320 | 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 |
|
|
346 | easy (it is often useful to build your own transaction class on top of |
|
|
347 | AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call |
|
|
348 | it's C<new> method in your own C<new> method. |
321 | |
349 | |
322 | =over 4 |
350 | There are two "sides" to a condition variable - the "producer side" which |
323 | |
351 | eventually calls C<< -> broadcast >>, and the "consumer side", which waits |
324 | =item $cv->wait |
352 | for the broadcast to occur. |
325 | |
|
|
326 | Wait (blocking if necessary) until the C<< ->broadcast >> method has been |
|
|
327 | called on c<$cv>, while servicing other watchers normally. |
|
|
328 | |
|
|
329 | You can only wait once on a condition - additional calls will return |
|
|
330 | immediately. |
|
|
331 | |
|
|
332 | Not all event models support a blocking wait - some die in that case |
|
|
333 | (programs might want to do that to stay interactive), so I<if you are |
|
|
334 | using this from a module, never require a blocking wait>, but let the |
|
|
335 | caller decide whether the call will block or not (for example, by coupling |
|
|
336 | condition variables with some kind of request results and supporting |
|
|
337 | callbacks so the caller knows that getting the result will not block, |
|
|
338 | while still suppporting blocking waits if the caller so desires). |
|
|
339 | |
|
|
340 | Another reason I<never> to C<< ->wait >> in a module is that you cannot |
|
|
341 | sensibly have two C<< ->wait >>'s in parallel, as that would require |
|
|
342 | multiple interpreters or coroutines/threads, none of which C<AnyEvent> |
|
|
343 | can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and |
|
|
344 | L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s |
|
|
345 | from different coroutines, however). |
|
|
346 | |
|
|
347 | =item $cv->broadcast |
|
|
348 | |
|
|
349 | Flag the condition as ready - a running C<< ->wait >> and all further |
|
|
350 | calls to C<wait> will (eventually) return after this method has been |
|
|
351 | called. If nobody is waiting the broadcast will be remembered.. |
|
|
352 | |
|
|
353 | =back |
|
|
354 | |
353 | |
355 | Example: |
354 | Example: |
356 | |
355 | |
357 | # wait till the result is ready |
356 | # wait till the result is ready |
358 | my $result_ready = AnyEvent->condvar; |
357 | my $result_ready = AnyEvent->condvar; |
… | |
… | |
364 | my $w = AnyEvent->timer ( |
363 | my $w = AnyEvent->timer ( |
365 | after => 1, |
364 | after => 1, |
366 | cb => sub { $result_ready->broadcast }, |
365 | cb => sub { $result_ready->broadcast }, |
367 | ); |
366 | ); |
368 | |
367 | |
369 | # this "blocks" (while handling events) till the watcher |
368 | # this "blocks" (while handling events) till the callback |
370 | # calls broadcast |
369 | # calls broadcast |
371 | $result_ready->wait; |
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 |
|
|
375 | code/module that eventually broadcasts the signal. Note that it is also |
|
|
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. |
|
|
378 | |
|
|
379 | =over 4 |
|
|
380 | |
|
|
381 | =item $cv->broadcast (...) |
|
|
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 broadcast will be remembered. |
|
|
386 | |
|
|
387 | If a callback has been set on the condition variable, it is called |
|
|
388 | immediately from within broadcast. |
|
|
389 | |
|
|
390 | Any arguments passed to the C<broadcast> call will be returned by all |
|
|
391 | future C<< ->wait >> calls. |
|
|
392 | |
|
|
393 | =item $cv->croak ($error) |
|
|
394 | |
|
|
395 | Similar to broadcast, 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<< ->broadcast >>, but that is not required. If no |
|
|
413 | callback was set, C<broadcast> 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->broadcast (\%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<broadcast> 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 | broadcast 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 | =item $cv->wait |
|
|
458 | |
|
|
459 | Wait (blocking if necessary) until the C<< ->broadcast >> or C<< ->croak |
|
|
460 | >> methods have been called on c<$cv>, while servicing other watchers |
|
|
461 | normally. |
|
|
462 | |
|
|
463 | You can only wait once on a condition - additional calls are valid but |
|
|
464 | will return immediately. |
|
|
465 | |
|
|
466 | If an error condition has been set by calling C<< ->croak >>, then this |
|
|
467 | function will call C<croak>. |
|
|
468 | |
|
|
469 | In list context, all parameters passed to C<broadcast> will be returned, |
|
|
470 | in scalar context only the first one will be returned. |
|
|
471 | |
|
|
472 | Not all event models support a blocking wait - some die in that case |
|
|
473 | (programs might want to do that to stay interactive), so I<if you are |
|
|
474 | using this from a module, never require a blocking wait>, but let the |
|
|
475 | caller decide whether the call will block or not (for example, by coupling |
|
|
476 | condition variables with some kind of request results and supporting |
|
|
477 | callbacks so the caller knows that getting the result will not block, |
|
|
478 | while still suppporting blocking waits if the caller so desires). |
|
|
479 | |
|
|
480 | Another reason I<never> to C<< ->wait >> in a module is that you cannot |
|
|
481 | sensibly have two C<< ->wait >>'s in parallel, as that would require |
|
|
482 | multiple interpreters or coroutines/threads, none of which C<AnyEvent> |
|
|
483 | can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and |
|
|
484 | L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s |
|
|
485 | from different coroutines, however). |
|
|
486 | |
|
|
487 | You can ensure that C<< -wait >> never blocks by setting a callback and |
|
|
488 | only calling C<< ->wait >> from within that callback (or at a later |
|
|
489 | time). This will work even when the event loop does not support blocking |
|
|
490 | waits otherwise. |
|
|
491 | |
|
|
492 | =back |
372 | |
493 | |
373 | =head1 GLOBAL VARIABLES AND FUNCTIONS |
494 | =head1 GLOBAL VARIABLES AND FUNCTIONS |
374 | |
495 | |
375 | =over 4 |
496 | =over 4 |
376 | |
497 | |
… | |
… | |
386 | |
507 | |
387 | AnyEvent::Impl::CoroEV based on Coro::EV, best choice. |
508 | AnyEvent::Impl::CoroEV based on Coro::EV, best choice. |
388 | AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice. |
509 | AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice. |
389 | AnyEvent::Impl::EV based on EV (an interface to libev, best choice). |
510 | AnyEvent::Impl::EV based on EV (an interface to libev, best choice). |
390 | AnyEvent::Impl::Event based on Event, second best choice. |
511 | AnyEvent::Impl::Event based on Event, second best choice. |
|
|
512 | AnyEvent::Impl::Perl pure-perl implementation, fast and portable. |
391 | AnyEvent::Impl::Glib based on Glib, third-best choice. |
513 | AnyEvent::Impl::Glib based on Glib, third-best choice. |
392 | AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable. |
|
|
393 | AnyEvent::Impl::Tk based on Tk, very bad choice. |
514 | AnyEvent::Impl::Tk based on Tk, very bad choice. |
394 | AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs). |
515 | AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs). |
395 | AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse. |
516 | AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse. |
396 | AnyEvent::Impl::POE based on POE, not generic enough for full support. |
517 | AnyEvent::Impl::POE based on POE, not generic enough for full support. |
397 | |
518 | |
… | |
… | |
453 | |
574 | |
454 | You can chose to use a rather inefficient pure-perl implementation by |
575 | You can chose to use a rather inefficient pure-perl implementation by |
455 | loading the C<AnyEvent::Impl::Perl> module, which gives you similar |
576 | loading the C<AnyEvent::Impl::Perl> module, which gives you similar |
456 | behaviour everywhere, but letting AnyEvent chose is generally better. |
577 | behaviour everywhere, but letting AnyEvent chose is generally better. |
457 | |
578 | |
|
|
579 | =head1 OTHER MODULES |
|
|
580 | |
|
|
581 | The following is a non-exhaustive list of additional modules that use |
|
|
582 | AnyEvent and can therefore be mixed easily with other AnyEvent modules |
|
|
583 | in the same program. Some of the modules come with AnyEvent, some are |
|
|
584 | available via CPAN. |
|
|
585 | |
|
|
586 | =over 4 |
|
|
587 | |
|
|
588 | =item L<AnyEvent::Util> |
|
|
589 | |
|
|
590 | Contains various utility functions that replace often-used but blocking |
|
|
591 | functions such as C<inet_aton> by event-/callback-based versions. |
|
|
592 | |
|
|
593 | =item L<AnyEvent::Handle> |
|
|
594 | |
|
|
595 | Provide read and write buffers and manages watchers for reads and writes. |
|
|
596 | |
|
|
597 | =item L<AnyEvent::Socket> |
|
|
598 | |
|
|
599 | Provides a means to do non-blocking connects, accepts etc. |
|
|
600 | |
|
|
601 | =item L<AnyEvent::HTTPD> |
|
|
602 | |
|
|
603 | Provides a simple web application server framework. |
|
|
604 | |
|
|
605 | =item L<AnyEvent::DNS> |
|
|
606 | |
|
|
607 | Provides asynchronous DNS resolver capabilities, beyond what |
|
|
608 | L<AnyEvent::Util> offers. |
|
|
609 | |
|
|
610 | =item L<AnyEvent::FastPing> |
|
|
611 | |
|
|
612 | The fastest ping in the west. |
|
|
613 | |
|
|
614 | =item L<Net::IRC3> |
|
|
615 | |
|
|
616 | AnyEvent based IRC client module family. |
|
|
617 | |
|
|
618 | =item L<Net::XMPP2> |
|
|
619 | |
|
|
620 | AnyEvent based XMPP (Jabber protocol) module family. |
|
|
621 | |
|
|
622 | =item L<Net::FCP> |
|
|
623 | |
|
|
624 | AnyEvent-based implementation of the Freenet Client Protocol, birthplace |
|
|
625 | of AnyEvent. |
|
|
626 | |
|
|
627 | =item L<Event::ExecFlow> |
|
|
628 | |
|
|
629 | High level API for event-based execution flow control. |
|
|
630 | |
|
|
631 | =item L<Coro> |
|
|
632 | |
|
|
633 | Has special support for AnyEvent. |
|
|
634 | |
|
|
635 | =item L<IO::Lambda> |
|
|
636 | |
|
|
637 | The lambda approach to I/O - don't ask, look there. Can use AnyEvent. |
|
|
638 | |
|
|
639 | =item L<IO::AIO> |
|
|
640 | |
|
|
641 | Truly asynchronous I/O, should be in the toolbox of every event |
|
|
642 | programmer. Can be trivially made to use AnyEvent. |
|
|
643 | |
|
|
644 | =item L<BDB> |
|
|
645 | |
|
|
646 | Truly asynchronous Berkeley DB access. Can be trivially made to use |
|
|
647 | AnyEvent. |
|
|
648 | |
|
|
649 | =back |
|
|
650 | |
458 | =cut |
651 | =cut |
459 | |
652 | |
460 | package AnyEvent; |
653 | package AnyEvent; |
461 | |
654 | |
462 | no warnings; |
655 | no warnings; |
… | |
… | |
477 | my @models = ( |
670 | my @models = ( |
478 | [Coro::EV:: => AnyEvent::Impl::CoroEV::], |
671 | [Coro::EV:: => AnyEvent::Impl::CoroEV::], |
479 | [Coro::Event:: => AnyEvent::Impl::CoroEvent::], |
672 | [Coro::Event:: => AnyEvent::Impl::CoroEvent::], |
480 | [EV:: => AnyEvent::Impl::EV::], |
673 | [EV:: => AnyEvent::Impl::EV::], |
481 | [Event:: => AnyEvent::Impl::Event::], |
674 | [Event:: => AnyEvent::Impl::Event::], |
482 | [Glib:: => AnyEvent::Impl::Glib::], |
|
|
483 | [Tk:: => AnyEvent::Impl::Tk::], |
675 | [Tk:: => AnyEvent::Impl::Tk::], |
484 | [Wx:: => AnyEvent::Impl::POE::], |
676 | [Wx:: => AnyEvent::Impl::POE::], |
485 | [Prima:: => AnyEvent::Impl::POE::], |
677 | [Prima:: => AnyEvent::Impl::POE::], |
486 | [AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::], |
678 | [AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::], |
487 | # everything below here will not be autoprobed as the pureperl backend should work everywhere |
679 | # everything below here will not be autoprobed as the pureperl backend should work everywhere |
|
|
680 | [Glib:: => AnyEvent::Impl::Glib::], |
488 | [Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy |
681 | [Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy |
489 | [Qt:: => AnyEvent::Impl::Qt::], # requires special main program |
682 | [Qt:: => AnyEvent::Impl::Qt::], # requires special main program |
490 | [POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza |
683 | [POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza |
491 | ); |
684 | ); |
492 | |
685 | |
… | |
… | |
889 | }); |
1082 | }); |
890 | |
1083 | |
891 | $quit->wait; |
1084 | $quit->wait; |
892 | |
1085 | |
893 | |
1086 | |
894 | =head1 BENCHMARK |
1087 | =head1 BENCHMARKS |
895 | |
1088 | |
896 | To give you an idea of the performance and overheads that AnyEvent adds |
1089 | To give you an idea of the performance and overheads that AnyEvent adds |
897 | over the event loops themselves (and to give you an impression of the |
1090 | over the event loops themselves and to give you an impression of the speed |
898 | speed of various event loops), here is a benchmark of various supported |
1091 | of various event loops I prepared some benchmarks. |
899 | event models natively and with anyevent. The benchmark creates a lot of |
1092 | |
900 | timers (with a zero timeout) and I/O watchers (watching STDOUT, a pty, to |
1093 | =head2 BENCHMARKING ANYEVENT OVERHEAD |
|
|
1094 | |
|
|
1095 | Here is a benchmark of various supported event models used natively and |
|
|
1096 | through anyevent. The benchmark creates a lot of timers (with a zero |
|
|
1097 | timeout) and I/O watchers (watching STDOUT, a pty, to become writable, |
901 | become writable, which it is), lets them fire exactly once and destroys |
1098 | which it is), lets them fire exactly once and destroys them again. |
902 | them again. |
|
|
903 | |
1099 | |
904 | Rewriting the benchmark to use many different sockets instead of using |
1100 | Source code for this benchmark is found as F<eg/bench> in the AnyEvent |
905 | the same filehandle for all I/O watchers results in a much longer runtime |
1101 | distribution. |
906 | (socket creation is expensive), but qualitatively the same figures, so it |
|
|
907 | was not used. |
|
|
908 | |
1102 | |
909 | =head2 Explanation of the columns |
1103 | =head3 Explanation of the columns |
910 | |
1104 | |
911 | I<watcher> is the number of event watchers created/destroyed. Since |
1105 | I<watcher> is the number of event watchers created/destroyed. Since |
912 | different event models feature vastly different performances, each event |
1106 | different event models feature vastly different performances, each event |
913 | loop was given a number of watchers so that overall runtime is acceptable |
1107 | loop was given a number of watchers so that overall runtime is acceptable |
914 | and similar between tested event loop (and keep them from crashing): Glib |
1108 | and similar between tested event loop (and keep them from crashing): Glib |
… | |
… | |
930 | signal the end of this phase. |
1124 | signal the end of this phase. |
931 | |
1125 | |
932 | I<destroy> is the time, in microseconds, that it takes to destroy a single |
1126 | I<destroy> is the time, in microseconds, that it takes to destroy a single |
933 | watcher. |
1127 | watcher. |
934 | |
1128 | |
935 | =head2 Results |
1129 | =head3 Results |
936 | |
1130 | |
937 | name watchers bytes create invoke destroy comment |
1131 | name watchers bytes create invoke destroy comment |
938 | EV/EV 400000 244 0.56 0.46 0.31 EV native interface |
1132 | EV/EV 400000 244 0.56 0.46 0.31 EV native interface |
939 | EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers |
1133 | EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers |
940 | CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal |
1134 | CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal |
941 | Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation |
1135 | Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation |
942 | Event/Event 16000 516 31.88 31.30 0.85 Event native interface |
1136 | Event/Event 16000 516 31.88 31.30 0.85 Event native interface |
943 | Event/Any 16000 936 39.17 33.63 1.43 Event + AnyEvent watchers |
1137 | Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers |
944 | Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour |
1138 | Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour |
945 | Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers |
1139 | Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers |
946 | POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event |
1140 | POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event |
947 | POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select |
1141 | POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select |
948 | |
1142 | |
949 | =head2 Discussion |
1143 | =head3 Discussion |
950 | |
1144 | |
951 | The benchmark does I<not> measure scalability of the event loop very |
1145 | The benchmark does I<not> measure scalability of the event loop very |
952 | well. For example, a select-based event loop (such as the pure perl one) |
1146 | well. For example, a select-based event loop (such as the pure perl one) |
953 | can never compete with an event loop that uses epoll when the number of |
1147 | can never compete with an event loop that uses epoll when the number of |
954 | file descriptors grows high. In this benchmark, all events become ready at |
1148 | file descriptors grows high. In this benchmark, all events become ready at |
955 | the same time, so select/poll-based implementations get an unnatural speed |
1149 | the same time, so select/poll-based implementations get an unnatural speed |
956 | boost. |
1150 | boost. |
957 | |
1151 | |
|
|
1152 | Also, note that the number of watchers usually has a nonlinear effect on |
|
|
1153 | overall speed, that is, creating twice as many watchers doesn't take twice |
|
|
1154 | the time - usually it takes longer. This puts event loops tested with a |
|
|
1155 | higher number of watchers at a disadvantage. |
|
|
1156 | |
|
|
1157 | To put the range of results into perspective, consider that on the |
|
|
1158 | benchmark machine, handling an event takes roughly 1600 CPU cycles with |
|
|
1159 | EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU |
|
|
1160 | cycles with POE. |
|
|
1161 | |
958 | C<EV> is the sole leader regarding speed and memory use, which are both |
1162 | C<EV> is the sole leader regarding speed and memory use, which are both |
959 | maximal/minimal, respectively. Even when going through AnyEvent, it uses |
1163 | maximal/minimal, respectively. Even when going through AnyEvent, it uses |
960 | far less memory than any other event loop and is still faster than Event |
1164 | far less memory than any other event loop and is still faster than Event |
961 | natively. |
1165 | natively. |
962 | |
1166 | |
963 | The pure perl implementation is hit in a few sweet spots (both the |
1167 | The pure perl implementation is hit in a few sweet spots (both the |
964 | zero timeout and the use of a single fd hit optimisations in the perl |
1168 | constant timeout and the use of a single fd hit optimisations in the perl |
965 | interpreter and the backend itself, and all watchers become ready at the |
1169 | interpreter and the backend itself). Nevertheless this shows that it |
966 | same time). Nevertheless this shows that it adds very little overhead in |
1170 | adds very little overhead in itself. Like any select-based backend its |
967 | itself. Like any select-based backend its performance becomes really bad |
1171 | performance becomes really bad with lots of file descriptors (and few of |
968 | with lots of file descriptors (and few of them active), of course, but |
1172 | them active), of course, but this was not subject of this benchmark. |
969 | this was not subject of this benchmark. |
|
|
970 | |
1173 | |
971 | The C<Event> module has a relatively high setup and callback invocation cost, |
1174 | The C<Event> module has a relatively high setup and callback invocation |
972 | but overall scores on the third place. |
1175 | cost, but overall scores in on the third place. |
973 | |
1176 | |
974 | C<Glib>'s memory usage is quite a bit bit higher, but it features a |
1177 | C<Glib>'s memory usage is quite a bit higher, but it features a |
975 | faster callback invocation and overall ends up in the same class as |
1178 | faster callback invocation and overall ends up in the same class as |
976 | C<Event>. However, Glib scales extremely badly, doubling the number of |
1179 | C<Event>. However, Glib scales extremely badly, doubling the number of |
977 | watchers increases the processing time by more than a factor of four, |
1180 | watchers increases the processing time by more than a factor of four, |
978 | making it completely unusable when using larger numbers of watchers |
1181 | making it completely unusable when using larger numbers of watchers |
979 | (note that only a single file descriptor was used in the benchmark, so |
1182 | (note that only a single file descriptor was used in the benchmark, so |
… | |
… | |
982 | The C<Tk> adaptor works relatively well. The fact that it crashes with |
1185 | The C<Tk> adaptor works relatively well. The fact that it crashes with |
983 | more than 2000 watchers is a big setback, however, as correctness takes |
1186 | more than 2000 watchers is a big setback, however, as correctness takes |
984 | precedence over speed. Nevertheless, its performance is surprising, as the |
1187 | precedence over speed. Nevertheless, its performance is surprising, as the |
985 | file descriptor is dup()ed for each watcher. This shows that the dup() |
1188 | file descriptor is dup()ed for each watcher. This shows that the dup() |
986 | employed by some adaptors is not a big performance issue (it does incur a |
1189 | employed by some adaptors is not a big performance issue (it does incur a |
987 | hidden memory cost inside the kernel, though, that is not reflected in the |
1190 | hidden memory cost inside the kernel which is not reflected in the figures |
988 | figures above). |
1191 | above). |
989 | |
1192 | |
990 | C<POE>, regardless of underlying event loop (wether using its pure perl |
1193 | C<POE>, regardless of underlying event loop (whether using its pure perl |
991 | select-based backend or the Event module) shows abysmal performance and |
1194 | select-based backend or the Event module, the POE-EV backend couldn't |
|
|
1195 | be tested because it wasn't working) shows abysmal performance and |
992 | memory usage: Watchers use almost 30 times as much memory as EV watchers, |
1196 | memory usage with AnyEvent: Watchers use almost 30 times as much memory |
993 | and 10 times as much memory as both Event or EV via AnyEvent. Watcher |
1197 | as EV watchers, and 10 times as much memory as Event (the high memory |
|
|
1198 | requirements are caused by requiring a session for each watcher). Watcher |
994 | invocation is almost 900 times slower than with AnyEvent's pure perl |
1199 | invocation speed is almost 900 times slower than with AnyEvent's pure perl |
|
|
1200 | implementation. |
|
|
1201 | |
995 | implementation. The design of the POE adaptor class in AnyEvent can not |
1202 | The design of the POE adaptor class in AnyEvent can not really account |
996 | really account for this, as session creation overhead is small compared |
1203 | for the performance issues, though, as session creation overhead is |
997 | to execution of the state machine, which is coded pretty optimally within |
1204 | small compared to execution of the state machine, which is coded pretty |
998 | L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow. |
1205 | optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that |
|
|
1206 | using multiple sessions is not a good approach, especially regarding |
|
|
1207 | memory usage, even the author of POE could not come up with a faster |
|
|
1208 | design). |
999 | |
1209 | |
1000 | =head2 Summary |
1210 | =head3 Summary |
1001 | |
1211 | |
|
|
1212 | =over 4 |
|
|
1213 | |
1002 | Using EV through AnyEvent is faster than any other event loop, but most |
1214 | =item * Using EV through AnyEvent is faster than any other event loop |
1003 | event loops have acceptable performance with or without AnyEvent. |
1215 | (even when used without AnyEvent), but most event loops have acceptable |
|
|
1216 | performance with or without AnyEvent. |
1004 | |
1217 | |
1005 | The overhead AnyEvent adds is usually much smaller than the overhead of |
1218 | =item * The overhead AnyEvent adds is usually much smaller than the overhead of |
1006 | the actual event loop, only with extremely fast event loops such as the EV |
1219 | the actual event loop, only with extremely fast event loops such as EV |
1007 | adds AnyEvent significant overhead. |
1220 | adds AnyEvent significant overhead. |
1008 | |
1221 | |
1009 | And you should simply avoid POE like the plague if you want performance or |
1222 | =item * You should avoid POE like the plague if you want performance or |
1010 | reasonable memory usage. |
1223 | reasonable memory usage. |
1011 | |
1224 | |
|
|
1225 | =back |
|
|
1226 | |
|
|
1227 | =head2 BENCHMARKING THE LARGE SERVER CASE |
|
|
1228 | |
|
|
1229 | This benchmark atcually benchmarks the event loop itself. It works by |
|
|
1230 | creating a number of "servers": each server consists of a socketpair, a |
|
|
1231 | timeout watcher that gets reset on activity (but never fires), and an I/O |
|
|
1232 | watcher waiting for input on one side of the socket. Each time the socket |
|
|
1233 | watcher reads a byte it will write that byte to a random other "server". |
|
|
1234 | |
|
|
1235 | The effect is that there will be a lot of I/O watchers, only part of which |
|
|
1236 | are active at any one point (so there is a constant number of active |
|
|
1237 | fds for each loop iterstaion, but which fds these are is random). The |
|
|
1238 | timeout is reset each time something is read because that reflects how |
|
|
1239 | most timeouts work (and puts extra pressure on the event loops). |
|
|
1240 | |
|
|
1241 | In this benchmark, we use 10000 socketpairs (20000 sockets), of which 100 |
|
|
1242 | (1%) are active. This mirrors the activity of large servers with many |
|
|
1243 | connections, most of which are idle at any one point in time. |
|
|
1244 | |
|
|
1245 | Source code for this benchmark is found as F<eg/bench2> in the AnyEvent |
|
|
1246 | distribution. |
|
|
1247 | |
|
|
1248 | =head3 Explanation of the columns |
|
|
1249 | |
|
|
1250 | I<sockets> is the number of sockets, and twice the number of "servers" (as |
|
|
1251 | each server has a read and write socket end). |
|
|
1252 | |
|
|
1253 | I<create> is the time it takes to create a socketpair (which is |
|
|
1254 | nontrivial) and two watchers: an I/O watcher and a timeout watcher. |
|
|
1255 | |
|
|
1256 | I<request>, the most important value, is the time it takes to handle a |
|
|
1257 | single "request", that is, reading the token from the pipe and forwarding |
|
|
1258 | it to another server. This includes deleting the old timeout and creating |
|
|
1259 | a new one that moves the timeout into the future. |
|
|
1260 | |
|
|
1261 | =head3 Results |
|
|
1262 | |
|
|
1263 | name sockets create request |
|
|
1264 | EV 20000 69.01 11.16 |
|
|
1265 | Perl 20000 73.32 35.87 |
|
|
1266 | Event 20000 212.62 257.32 |
|
|
1267 | Glib 20000 651.16 1896.30 |
|
|
1268 | POE 20000 349.67 12317.24 uses POE::Loop::Event |
|
|
1269 | |
|
|
1270 | =head3 Discussion |
|
|
1271 | |
|
|
1272 | This benchmark I<does> measure scalability and overall performance of the |
|
|
1273 | particular event loop. |
|
|
1274 | |
|
|
1275 | EV is again fastest. Since it is using epoll on my system, the setup time |
|
|
1276 | is relatively high, though. |
|
|
1277 | |
|
|
1278 | Perl surprisingly comes second. It is much faster than the C-based event |
|
|
1279 | loops Event and Glib. |
|
|
1280 | |
|
|
1281 | Event suffers from high setup time as well (look at its code and you will |
|
|
1282 | understand why). Callback invocation also has a high overhead compared to |
|
|
1283 | the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event |
|
|
1284 | uses select or poll in basically all documented configurations. |
|
|
1285 | |
|
|
1286 | Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It |
|
|
1287 | clearly fails to perform with many filehandles or in busy servers. |
|
|
1288 | |
|
|
1289 | POE is still completely out of the picture, taking over 1000 times as long |
|
|
1290 | as EV, and over 100 times as long as the Perl implementation, even though |
|
|
1291 | it uses a C-based event loop in this case. |
|
|
1292 | |
|
|
1293 | =head3 Summary |
|
|
1294 | |
|
|
1295 | =over 4 |
|
|
1296 | |
|
|
1297 | =item * The pure perl implementation performs extremely well. |
|
|
1298 | |
|
|
1299 | =item * Avoid Glib or POE in large projects where performance matters. |
|
|
1300 | |
|
|
1301 | =back |
|
|
1302 | |
|
|
1303 | =head2 BENCHMARKING SMALL SERVERS |
|
|
1304 | |
|
|
1305 | While event loops should scale (and select-based ones do not...) even to |
|
|
1306 | large servers, most programs we (or I :) actually write have only a few |
|
|
1307 | I/O watchers. |
|
|
1308 | |
|
|
1309 | In this benchmark, I use the same benchmark program as in the large server |
|
|
1310 | case, but it uses only eight "servers", of which three are active at any |
|
|
1311 | one time. This should reflect performance for a small server relatively |
|
|
1312 | well. |
|
|
1313 | |
|
|
1314 | The columns are identical to the previous table. |
|
|
1315 | |
|
|
1316 | =head3 Results |
|
|
1317 | |
|
|
1318 | name sockets create request |
|
|
1319 | EV 16 20.00 6.54 |
|
|
1320 | Perl 16 25.75 12.62 |
|
|
1321 | Event 16 81.27 35.86 |
|
|
1322 | Glib 16 32.63 15.48 |
|
|
1323 | POE 16 261.87 276.28 uses POE::Loop::Event |
|
|
1324 | |
|
|
1325 | =head3 Discussion |
|
|
1326 | |
|
|
1327 | The benchmark tries to test the performance of a typical small |
|
|
1328 | server. While knowing how various event loops perform is interesting, keep |
|
|
1329 | in mind that their overhead in this case is usually not as important, due |
|
|
1330 | to the small absolute number of watchers (that is, you need efficiency and |
|
|
1331 | speed most when you have lots of watchers, not when you only have a few of |
|
|
1332 | them). |
|
|
1333 | |
|
|
1334 | EV is again fastest. |
|
|
1335 | |
|
|
1336 | Perl again comes second. It is noticably faster than the C-based event |
|
|
1337 | loops Event and Glib, although the difference is too small to really |
|
|
1338 | matter. |
|
|
1339 | |
|
|
1340 | POE also performs much better in this case, but is is still far behind the |
|
|
1341 | others. |
|
|
1342 | |
|
|
1343 | =head3 Summary |
|
|
1344 | |
|
|
1345 | =over 4 |
|
|
1346 | |
|
|
1347 | =item * C-based event loops perform very well with small number of |
|
|
1348 | watchers, as the management overhead dominates. |
|
|
1349 | |
|
|
1350 | =back |
|
|
1351 | |
1012 | |
1352 | |
1013 | =head1 FORK |
1353 | =head1 FORK |
1014 | |
1354 | |
1015 | Most event libraries are not fork-safe. The ones who are usually are |
1355 | Most event libraries are not fork-safe. The ones who are usually are |
1016 | because they are so inefficient. Only L<EV> is fully fork-aware. |
1356 | because they rely on inefficient but fork-safe C<select> or C<poll> |
|
|
1357 | calls. Only L<EV> is fully fork-aware. |
1017 | |
1358 | |
1018 | If you have to fork, you must either do so I<before> creating your first |
1359 | If you have to fork, you must either do so I<before> creating your first |
1019 | watcher OR you must not use AnyEvent at all in the child. |
1360 | watcher OR you must not use AnyEvent at all in the child. |
1020 | |
1361 | |
1021 | |
1362 | |