… | |
… | |
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? |
… | |
… | |
288 | my $w = AnyEvent->child ( |
288 | my $w = AnyEvent->child ( |
289 | pid => $pid, |
289 | pid => $pid, |
290 | cb => sub { |
290 | cb => sub { |
291 | my ($pid, $status) = @_; |
291 | my ($pid, $status) = @_; |
292 | warn "pid $pid exited with status $status"; |
292 | warn "pid $pid exited with status $status"; |
293 | $done->broadcast; |
293 | $done->send; |
294 | }, |
294 | }, |
295 | ); |
295 | ); |
296 | |
296 | |
297 | # do something else, then wait for process exit |
297 | # do something else, then wait for process exit |
298 | $done->wait; |
298 | $done->wait; |
… | |
… | |
313 | >> method, usually without arguments. The only argument pair allowed is |
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 |
314 | C<cb>, which specifies a callback to be called when the condition variable |
315 | becomes true. |
315 | becomes true. |
316 | |
316 | |
317 | After creation, the conditon variable is "false" until it becomes "true" |
317 | After creation, the conditon variable is "false" until it becomes "true" |
318 | by calling the C<broadcast> method. |
318 | by calling the C<send> method. |
319 | |
319 | |
320 | Condition variables are similar to callbacks, except that you can |
320 | Condition variables are similar to callbacks, except that you can |
321 | optionally wait for them. They can also be called merge points - points |
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 |
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 |
323 | another way to call them is transations - each condition variable can be |
… | |
… | |
331 | called or can synchronously C<< ->wait >> for the results. |
331 | called or can synchronously C<< ->wait >> for the results. |
332 | |
332 | |
333 | You can also use them to simulate traditional event loops - for example, |
333 | You can also use them to simulate traditional event loops - for example, |
334 | you can block your main program until an event occurs - for example, you |
334 | you can block your main program until an event occurs - for example, you |
335 | could C<< ->wait >> in your main program until the user clicks the Quit |
335 | could C<< ->wait >> in your main program until the user clicks the Quit |
336 | button of your app, which would C<< ->broadcast >> the "quit" event. |
336 | button of your app, which would C<< ->send >> the "quit" event. |
337 | |
337 | |
338 | 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 |
339 | two pieces 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 |
340 | 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 |
341 | 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, |
… | |
… | |
346 | easy (it is often useful to build your own transaction class on top of |
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 |
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. |
348 | it's C<new> method in your own C<new> method. |
349 | |
349 | |
350 | There are two "sides" to a condition variable - the "producer side" which |
350 | There are two "sides" to a condition variable - the "producer side" which |
351 | eventually calls C<< -> broadcast >>, and the "consumer side", which waits |
351 | eventually calls C<< -> send >>, and the "consumer side", which waits |
352 | for the broadcast to occur. |
352 | for the send to occur. |
353 | |
353 | |
354 | Example: |
354 | Example: |
355 | |
355 | |
356 | # wait till the result is ready |
356 | # wait till the result is ready |
357 | my $result_ready = AnyEvent->condvar; |
357 | my $result_ready = AnyEvent->condvar; |
358 | |
358 | |
359 | # do something such as adding a timer |
359 | # do something such as adding a timer |
360 | # or socket watcher the calls $result_ready->broadcast |
360 | # or socket watcher the calls $result_ready->send |
361 | # when the "result" is ready. |
361 | # when the "result" is ready. |
362 | # in this case, we simply use a timer: |
362 | # in this case, we simply use a timer: |
363 | my $w = AnyEvent->timer ( |
363 | my $w = AnyEvent->timer ( |
364 | after => 1, |
364 | after => 1, |
365 | cb => sub { $result_ready->broadcast }, |
365 | cb => sub { $result_ready->send }, |
366 | ); |
366 | ); |
367 | |
367 | |
368 | # this "blocks" (while handling events) till the callback |
368 | # this "blocks" (while handling events) till the callback |
369 | # calls broadcast |
369 | # calls send |
370 | $result_ready->wait; |
370 | $result_ready->wait; |
371 | |
371 | |
372 | =head3 METHODS FOR PRODUCERS |
372 | =head3 METHODS FOR PRODUCERS |
373 | |
373 | |
374 | These methods should only be used by the producing side, i.e. the |
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 |
375 | code/module that eventually sends the signal. Note that it is also |
376 | the producer side which creates the condvar in most cases, but it isn't |
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. |
377 | uncommon for the consumer to create it as well. |
378 | |
378 | |
379 | =over 4 |
379 | =over 4 |
380 | |
380 | |
381 | =item $cv->broadcast (...) |
381 | =item $cv->send (...) |
382 | |
382 | |
383 | Flag the condition as ready - a running C<< ->wait >> and all further |
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 |
384 | calls to C<wait> will (eventually) return after this method has been |
385 | called. If nobody is waiting the broadcast will be remembered. |
385 | called. If nobody is waiting the send will be remembered. |
386 | |
386 | |
387 | If a callback has been set on the condition variable, it is called |
387 | If a callback has been set on the condition variable, it is called |
388 | immediately from within broadcast. |
388 | immediately from within send. |
389 | |
389 | |
390 | Any arguments passed to the C<broadcast> call will be returned by all |
390 | Any arguments passed to the C<send> call will be returned by all |
391 | future C<< ->wait >> calls. |
391 | future C<< ->wait >> calls. |
392 | |
392 | |
393 | =item $cv->croak ($error) |
393 | =item $cv->croak ($error) |
394 | |
394 | |
395 | Similar to broadcast, but causes all call's wait C<< ->wait >> to invoke |
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. |
396 | C<Carp::croak> with the given error message/object/scalar. |
397 | |
397 | |
398 | This can be used to signal any errors to the condition variable |
398 | This can be used to signal any errors to the condition variable |
399 | user/consumer. |
399 | user/consumer. |
400 | |
400 | |
… | |
… | |
407 | to use a condition variable for the whole process. |
407 | to use a condition variable for the whole process. |
408 | |
408 | |
409 | Every call to C<< ->begin >> will increment a counter, and every call to |
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 |
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 |
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 |
412 | is I<supposed> to call C<< ->send >>, but that is not required. If no |
413 | callback was set, C<broadcast> will be called without any arguments. |
413 | callback was set, C<send> will be called without any arguments. |
414 | |
414 | |
415 | Let's clarify this with the ping example: |
415 | Let's clarify this with the ping example: |
416 | |
416 | |
417 | my $cv = AnyEvent->condvar; |
417 | my $cv = AnyEvent->condvar; |
418 | |
418 | |
419 | my %result; |
419 | my %result; |
420 | $cv->begin (sub { $cv->broadcast (\%result) }); |
420 | $cv->begin (sub { $cv->send (\%result) }); |
421 | |
421 | |
422 | for my $host (@list_of_hosts) { |
422 | for my $host (@list_of_hosts) { |
423 | $cv->begin; |
423 | $cv->begin; |
424 | ping_host_then_call_callback $host, sub { |
424 | ping_host_then_call_callback $host, sub { |
425 | $result{$host} = ...; |
425 | $result{$host} = ...; |
… | |
… | |
428 | } |
428 | } |
429 | |
429 | |
430 | $cv->end; |
430 | $cv->end; |
431 | |
431 | |
432 | This code fragment supposedly pings a number of hosts and calls |
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 |
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 |
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 |
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 |
436 | it. Since C<begin> and C<end> only maintain a counter, the order in which |
437 | results arrive is not relevant. |
437 | results arrive is not relevant. |
438 | |
438 | |
439 | There is an additional bracketing call to C<begin> and C<end> outside the |
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 |
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 |
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 |
442 | C<send> is called even when C<no> hosts are being pinged (the loop |
443 | doesn't execute once). |
443 | doesn't execute once). |
444 | |
444 | |
445 | This is the general pattern when you "fan out" into multiple subrequests: |
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> |
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 |
447 | is called at least once, and then, for each subrequest you start, call |
… | |
… | |
452 | =head3 METHODS FOR CONSUMERS |
452 | =head3 METHODS FOR CONSUMERS |
453 | |
453 | |
454 | These methods should only be used by the consuming side, i.e. the |
454 | These methods should only be used by the consuming side, i.e. the |
455 | code awaits the condition. |
455 | code awaits the condition. |
456 | |
456 | |
|
|
457 | =over 4 |
|
|
458 | |
457 | =item $cv->wait |
459 | =item $cv->wait |
458 | |
460 | |
459 | Wait (blocking if necessary) until the C<< ->broadcast >> or C<< ->croak |
461 | Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak |
460 | >> methods have been called on c<$cv>, while servicing other watchers |
462 | >> methods have been called on c<$cv>, while servicing other watchers |
461 | normally. |
463 | normally. |
462 | |
464 | |
463 | You can only wait once on a condition - additional calls are valid but |
465 | You can only wait once on a condition - additional calls are valid but |
464 | will return immediately. |
466 | will return immediately. |
465 | |
467 | |
466 | If an error condition has been set by calling C<< ->croak >>, then this |
468 | If an error condition has been set by calling C<< ->croak >>, then this |
467 | function will call C<croak>. |
469 | function will call C<croak>. |
468 | |
470 | |
469 | In list context, all parameters passed to C<broadcast> will be returned, |
471 | In list context, all parameters passed to C<send> will be returned, |
470 | in scalar context only the first one will be returned. |
472 | in scalar context only the first one will be returned. |
471 | |
473 | |
472 | 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 |
473 | (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 |
474 | 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 |
… | |
… | |
486 | |
488 | |
487 | You can ensure that C<< -wait >> never blocks by setting a callback and |
489 | 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 |
490 | 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 |
491 | time). This will work even when the event loop does not support blocking |
490 | waits otherwise. |
492 | waits otherwise. |
|
|
493 | |
|
|
494 | =item $bool = $cv->ready |
|
|
495 | |
|
|
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. |
491 | |
507 | |
492 | =back |
508 | =back |
493 | |
509 | |
494 | =head1 GLOBAL VARIABLES AND FUNCTIONS |
510 | =head1 GLOBAL VARIABLES AND FUNCTIONS |
495 | |
511 | |
… | |
… | |
544 | 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 |
545 | 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 |
546 | to load the event module first. |
562 | to load the event module first. |
547 | |
563 | |
548 | 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 |
549 | 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 |
550 | 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 |
551 | events is to stay interactive. |
567 | events is to stay interactive. |
552 | |
568 | |
553 | 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 |
554 | 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 |
… | |
… | |
681 | [Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy |
697 | [Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy |
682 | [Qt:: => AnyEvent::Impl::Qt::], # requires special main program |
698 | [Qt:: => AnyEvent::Impl::Qt::], # requires special main program |
683 | [POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza |
699 | [POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza |
684 | ); |
700 | ); |
685 | |
701 | |
686 | our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY); |
702 | our %method = map +($_ => 1), qw(io timer signal child condvar one_event DESTROY); |
687 | |
703 | |
688 | sub detect() { |
704 | sub detect() { |
689 | unless ($MODEL) { |
705 | unless ($MODEL) { |
690 | no strict 'refs'; |
706 | no strict 'refs'; |
691 | |
707 | |