1 | NAME |
1 | NAME |
2 | AnyEvent - the DBI of event loop programming |
2 | AnyEvent - the DBI of event loop programming |
3 | |
3 | |
4 | EV, Event, Glib, Tk, Perl, Event::Lib, Irssi, IO::Async, Qt and POE are |
4 | EV, Event, Glib, Tk, Perl, Event::Lib, Irssi, rxvt-unicode, IO::Async, |
5 | various supported event loops/environments. |
5 | Qt and POE are various supported event loops/environments. |
6 | |
6 | |
7 | SYNOPSIS |
7 | SYNOPSIS |
8 | use AnyEvent; |
8 | use AnyEvent; |
9 | |
9 | |
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10 | # if you prefer function calls, look at the AE manpage for |
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11 | # an alternative API. |
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12 | |
10 | # file descriptor readable |
13 | # file handle or descriptor readable |
11 | my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... }); |
14 | my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... }); |
12 | |
15 | |
13 | # one-shot or repeating timers |
16 | # one-shot or repeating timers |
14 | my $w = AnyEvent->timer (after => $seconds, cb => sub { ... }); |
17 | my $w = AnyEvent->timer (after => $seconds, cb => sub { ... }); |
15 | my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ... |
18 | my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ... |
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173 | Note that "my $w; $w =" combination. This is necessary because in Perl, |
176 | Note that "my $w; $w =" combination. This is necessary because in Perl, |
174 | my variables are only visible after the statement in which they are |
177 | my variables are only visible after the statement in which they are |
175 | declared. |
178 | declared. |
176 | |
179 | |
177 | I/O WATCHERS |
180 | I/O WATCHERS |
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181 | $w = AnyEvent->io ( |
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182 | fh => <filehandle_or_fileno>, |
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183 | poll => <"r" or "w">, |
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184 | cb => <callback>, |
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185 | ); |
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186 | |
178 | You can create an I/O watcher by calling the "AnyEvent->io" method with |
187 | You can create an I/O watcher by calling the "AnyEvent->io" method with |
179 | the following mandatory key-value pairs as arguments: |
188 | the following mandatory key-value pairs as arguments: |
180 | |
189 | |
181 | "fh" is the Perl *file handle* (or a naked file descriptor) to watch for |
190 | "fh" is the Perl *file handle* (or a naked file descriptor) to watch for |
182 | events (AnyEvent might or might not keep a reference to this file |
191 | events (AnyEvent might or might not keep a reference to this file |
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210 | warn "read: $input\n"; |
219 | warn "read: $input\n"; |
211 | undef $w; |
220 | undef $w; |
212 | }); |
221 | }); |
213 | |
222 | |
214 | TIME WATCHERS |
223 | TIME WATCHERS |
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224 | $w = AnyEvent->timer (after => <seconds>, cb => <callback>); |
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225 | |
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226 | $w = AnyEvent->timer ( |
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227 | after => <fractional_seconds>, |
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228 | interval => <fractional_seconds>, |
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229 | cb => <callback>, |
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230 | ); |
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231 | |
215 | You can create a time watcher by calling the "AnyEvent->timer" method |
232 | You can create a time watcher by calling the "AnyEvent->timer" method |
216 | with the following mandatory arguments: |
233 | with the following mandatory arguments: |
217 | |
234 | |
218 | "after" specifies after how many seconds (fractional values are |
235 | "after" specifies after how many seconds (fractional values are |
219 | supported) the callback should be invoked. "cb" is the callback to |
236 | supported) the callback should be invoked. "cb" is the callback to |
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340 | time, which might affect timers and time-outs. |
357 | time, which might affect timers and time-outs. |
341 | |
358 | |
342 | When this is the case, you can call this method, which will update |
359 | When this is the case, you can call this method, which will update |
343 | the event loop's idea of "current time". |
360 | the event loop's idea of "current time". |
344 | |
361 | |
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362 | A typical example would be a script in a web server (e.g. |
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363 | "mod_perl") - when mod_perl executes the script, then the event loop |
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364 | will have the wrong idea about the "current time" (being potentially |
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365 | far in the past, when the script ran the last time). In that case |
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366 | you should arrange a call to "AnyEvent->now_update" each time the |
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367 | web server process wakes up again (e.g. at the start of your script, |
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368 | or in a handler). |
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369 | |
345 | Note that updating the time *might* cause some events to be handled. |
370 | Note that updating the time *might* cause some events to be handled. |
346 | |
371 | |
347 | SIGNAL WATCHERS |
372 | SIGNAL WATCHERS |
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373 | $w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>); |
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374 | |
348 | You can watch for signals using a signal watcher, "signal" is the signal |
375 | You can watch for signals using a signal watcher, "signal" is the signal |
349 | *name* in uppercase and without any "SIG" prefix, "cb" is the Perl |
376 | *name* in uppercase and without any "SIG" prefix, "cb" is the Perl |
350 | callback to be invoked whenever a signal occurs. |
377 | callback to be invoked whenever a signal occurs. |
351 | |
378 | |
352 | Although the callback might get passed parameters, their value and |
379 | Although the callback might get passed parameters, their value and |
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368 | |
395 | |
369 | Example: exit on SIGINT |
396 | Example: exit on SIGINT |
370 | |
397 | |
371 | my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 }); |
398 | my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 }); |
372 | |
399 | |
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400 | Restart Behaviour |
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401 | While restart behaviour is up to the event loop implementation, most |
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402 | will not restart syscalls (that includes Async::Interrupt and AnyEvent's |
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403 | pure perl implementation). |
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404 | |
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405 | Safe/Unsafe Signals |
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406 | Perl signals can be either "safe" (synchronous to opcode handling) or |
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407 | "unsafe" (asynchronous) - the former might get delayed indefinitely, the |
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408 | latter might corrupt your memory. |
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409 | |
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410 | AnyEvent signal handlers are, in addition, synchronous to the event |
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411 | loop, i.e. they will not interrupt your running perl program but will |
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412 | only be called as part of the normal event handling (just like timer, |
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413 | I/O etc. callbacks, too). |
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414 | |
373 | Signal Races, Delays and Workarounds |
415 | Signal Races, Delays and Workarounds |
374 | Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching |
416 | Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching |
375 | callbacks to signals in a generic way, which is a pity, as you cannot do |
417 | callbacks to signals in a generic way, which is a pity, as you cannot do |
376 | race-free signal handling in perl. AnyEvent will try to do it's best, |
418 | race-free signal handling in perl, requiring C libraries for this. |
377 | but in some cases, signals will be delayed. The maximum time a signal |
419 | AnyEvent will try to do it's best, which means in some cases, signals |
378 | might be delayed is specified in $AnyEvent::MAX_SIGNAL_LATENCY (default: |
420 | will be delayed. The maximum time a signal might be delayed is specified |
379 | 10 seconds). This variable can be changed only before the first signal |
421 | in $AnyEvent::MAX_SIGNAL_LATENCY (default: 10 seconds). This variable |
380 | watcher is created, and should be left alone otherwise. Higher values |
422 | can be changed only before the first signal watcher is created, and |
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423 | should be left alone otherwise. This variable determines how often |
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424 | AnyEvent polls for signals (in case a wake-up was missed). Higher values |
381 | will cause fewer spurious wake-ups, which is better for power and CPU |
425 | will cause fewer spurious wake-ups, which is better for power and CPU |
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426 | saving. |
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427 | |
382 | saving. All these problems can be avoided by installing the optional |
428 | All these problems can be avoided by installing the optional |
383 | Async::Interrupt module. This will not work with inherently broken event |
429 | Async::Interrupt module, which works with most event loops. It will not |
384 | loops such as Event or Event::Lib (and not with POE currently, as POE |
430 | work with inherently broken event loops such as Event or Event::Lib (and |
385 | does it's own workaround with one-second latency). With those, you just |
431 | not with POE currently, as POE does it's own workaround with one-second |
386 | have to suffer the delays. |
432 | latency). For those, you just have to suffer the delays. |
387 | |
433 | |
388 | CHILD PROCESS WATCHERS |
434 | CHILD PROCESS WATCHERS |
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435 | $w = AnyEvent->child (pid => <process id>, cb => <callback>); |
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436 | |
389 | You can also watch on a child process exit and catch its exit status. |
437 | You can also watch on a child process exit and catch its exit status. |
390 | |
438 | |
391 | The child process is specified by the "pid" argument (one some backends, |
439 | The child process is specified by the "pid" argument (one some backends, |
392 | using 0 watches for any child process exit, on others this will croak). |
440 | using 0 watches for any child process exit, on others this will croak). |
393 | The watcher will be triggered only when the child process has finished |
441 | The watcher will be triggered only when the child process has finished |
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439 | |
487 | |
440 | # do something else, then wait for process exit |
488 | # do something else, then wait for process exit |
441 | $done->recv; |
489 | $done->recv; |
442 | |
490 | |
443 | IDLE WATCHERS |
491 | IDLE WATCHERS |
444 | Sometimes there is a need to do something, but it is not so important to |
492 | $w = AnyEvent->idle (cb => <callback>); |
445 | do it instantly, but only when there is nothing better to do. This |
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446 | "nothing better to do" is usually defined to be "no other events need |
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447 | attention by the event loop". |
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448 | |
493 | |
449 | Idle watchers ideally get invoked when the event loop has nothing better |
494 | Repeatedly invoke the callback after the process becomes idle, until |
450 | to do, just before it would block the process to wait for new events. |
495 | either the watcher is destroyed or new events have been detected. |
451 | Instead of blocking, the idle watcher is invoked. |
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452 | |
496 | |
453 | Most event loops unfortunately do not really support idle watchers (only |
497 | Idle watchers are useful when there is a need to do something, but it is |
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498 | not so important (or wise) to do it instantly. The callback will be |
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499 | invoked only when there is "nothing better to do", which is usually |
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500 | defined as "all outstanding events have been handled and no new events |
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501 | have been detected". That means that idle watchers ideally get invoked |
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502 | when the event loop has just polled for new events but none have been |
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503 | detected. Instead of blocking to wait for more events, the idle watchers |
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504 | will be invoked. |
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505 | |
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506 | Unfortunately, most event loops do not really support idle watchers |
454 | EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent |
507 | (only EV, Event and Glib do it in a usable fashion) - for the rest, |
455 | will simply call the callback "from time to time". |
508 | AnyEvent will simply call the callback "from time to time". |
456 | |
509 | |
457 | Example: read lines from STDIN, but only process them when the program |
510 | Example: read lines from STDIN, but only process them when the program |
458 | is otherwise idle: |
511 | is otherwise idle: |
459 | |
512 | |
460 | my @lines; # read data |
513 | my @lines; # read data |
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473 | } |
526 | } |
474 | }); |
527 | }); |
475 | }); |
528 | }); |
476 | |
529 | |
477 | CONDITION VARIABLES |
530 | CONDITION VARIABLES |
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531 | $cv = AnyEvent->condvar; |
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532 | |
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533 | $cv->send (<list>); |
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534 | my @res = $cv->recv; |
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535 | |
478 | If you are familiar with some event loops you will know that all of them |
536 | If you are familiar with some event loops you will know that all of them |
479 | require you to run some blocking "loop", "run" or similar function that |
537 | require you to run some blocking "loop", "run" or similar function that |
480 | will actively watch for new events and call your callbacks. |
538 | will actively watch for new events and call your callbacks. |
481 | |
539 | |
482 | AnyEvent is slightly different: it expects somebody else to run the |
540 | AnyEvent is slightly different: it expects somebody else to run the |
483 | event loop and will only block when necessary (usually when told by the |
541 | event loop and will only block when necessary (usually when told by the |
484 | user). |
542 | user). |
485 | |
543 | |
486 | The instrument to do that is called a "condition variable", so called |
544 | The tool to do that is called a "condition variable", so called because |
487 | because they represent a condition that must become true. |
545 | they represent a condition that must become true. |
488 | |
546 | |
489 | Now is probably a good time to look at the examples further below. |
547 | Now is probably a good time to look at the examples further below. |
490 | |
548 | |
491 | Condition variables can be created by calling the "AnyEvent->condvar" |
549 | Condition variables can be created by calling the "AnyEvent->condvar" |
492 | method, usually without arguments. The only argument pair allowed is |
550 | method, usually without arguments. The only argument pair allowed is |
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497 | After creation, the condition variable is "false" until it becomes |
555 | After creation, the condition variable is "false" until it becomes |
498 | "true" by calling the "send" method (or calling the condition variable |
556 | "true" by calling the "send" method (or calling the condition variable |
499 | as if it were a callback, read about the caveats in the description for |
557 | as if it were a callback, read about the caveats in the description for |
500 | the "->send" method). |
558 | the "->send" method). |
501 | |
559 | |
502 | Condition variables are similar to callbacks, except that you can |
560 | Since condition variables are the most complex part of the AnyEvent API, |
503 | optionally wait for them. They can also be called merge points - points |
561 | here are some different mental models of what they are - pick the ones |
504 | in time where multiple outstanding events have been processed. And yet |
562 | you can connect to: |
505 | another way to call them is transactions - each condition variable can |
563 | |
506 | be used to represent a transaction, which finishes at some point and |
564 | * Condition variables are like callbacks - you can call them (and pass |
507 | delivers a result. And yet some people know them as "futures" - a |
565 | them instead of callbacks). Unlike callbacks however, you can also |
508 | promise to compute/deliver something that you can wait for. |
566 | wait for them to be called. |
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567 | |
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568 | * Condition variables are signals - one side can emit or send them, |
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569 | the other side can wait for them, or install a handler that is |
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570 | called when the signal fires. |
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571 | |
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572 | * Condition variables are like "Merge Points" - points in your program |
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573 | where you merge multiple independent results/control flows into one. |
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574 | |
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575 | * Condition variables represent a transaction - function that start |
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576 | some kind of transaction can return them, leaving the caller the |
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577 | choice between waiting in a blocking fashion, or setting a callback. |
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578 | |
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579 | * Condition variables represent future values, or promises to deliver |
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580 | some result, long before the result is available. |
509 | |
581 | |
510 | Condition variables are very useful to signal that something has |
582 | Condition variables are very useful to signal that something has |
511 | finished, for example, if you write a module that does asynchronous http |
583 | finished, for example, if you write a module that does asynchronous http |
512 | requests, then a condition variable would be the ideal candidate to |
584 | requests, then a condition variable would be the ideal candidate to |
513 | signal the availability of results. The user can either act when the |
585 | signal the availability of results. The user can either act when the |
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534 | which eventually calls "-> send", and the "consumer side", which waits |
606 | which eventually calls "-> send", and the "consumer side", which waits |
535 | for the send to occur. |
607 | for the send to occur. |
536 | |
608 | |
537 | Example: wait for a timer. |
609 | Example: wait for a timer. |
538 | |
610 | |
539 | # wait till the result is ready |
611 | # condition: "wait till the timer is fired" |
540 | my $result_ready = AnyEvent->condvar; |
612 | my $timer_fired = AnyEvent->condvar; |
541 | |
613 | |
542 | # do something such as adding a timer |
614 | # create the timer - we could wait for, say |
543 | # or socket watcher the calls $result_ready->send |
615 | # a handle becomign ready, or even an |
544 | # when the "result" is ready. |
616 | # AnyEvent::HTTP request to finish, but |
545 | # in this case, we simply use a timer: |
617 | # in this case, we simply use a timer: |
546 | my $w = AnyEvent->timer ( |
618 | my $w = AnyEvent->timer ( |
547 | after => 1, |
619 | after => 1, |
548 | cb => sub { $result_ready->send }, |
620 | cb => sub { $timer_fired->send }, |
549 | ); |
621 | ); |
550 | |
622 | |
551 | # this "blocks" (while handling events) till the callback |
623 | # this "blocks" (while handling events) till the callback |
552 | # calls -<send |
624 | # calls ->send |
553 | $result_ready->recv; |
625 | $timer_fired->recv; |
554 | |
626 | |
555 | Example: wait for a timer, but take advantage of the fact that condition |
627 | Example: wait for a timer, but take advantage of the fact that condition |
556 | variables are also callable directly. |
628 | variables are also callable directly. |
557 | |
629 | |
558 | my $done = AnyEvent->condvar; |
630 | my $done = AnyEvent->condvar; |
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614 | into one. For example, a function that pings many hosts in parallel |
686 | into one. For example, a function that pings many hosts in parallel |
615 | might want to use a condition variable for the whole process. |
687 | might want to use a condition variable for the whole process. |
616 | |
688 | |
617 | Every call to "->begin" will increment a counter, and every call to |
689 | Every call to "->begin" will increment a counter, and every call to |
618 | "->end" will decrement it. If the counter reaches 0 in "->end", the |
690 | "->end" will decrement it. If the counter reaches 0 in "->end", the |
619 | (last) callback passed to "begin" will be executed. That callback is |
691 | (last) callback passed to "begin" will be executed, passing the |
620 | *supposed* to call "->send", but that is not required. If no |
692 | condvar as first argument. That callback is *supposed* to call |
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693 | "->send", but that is not required. If no group callback was set, |
621 | callback was set, "send" will be called without any arguments. |
694 | "send" will be called without any arguments. |
622 | |
695 | |
623 | You can think of "$cv->send" giving you an OR condition (one call |
696 | You can think of "$cv->send" giving you an OR condition (one call |
624 | sends), while "$cv->begin" and "$cv->end" giving you an AND |
697 | sends), while "$cv->begin" and "$cv->end" giving you an AND |
625 | condition (all "begin" calls must be "end"'ed before the condvar |
698 | condition (all "begin" calls must be "end"'ed before the condvar |
626 | sends). |
699 | sends). |
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654 | that are begung can potentially be zero: |
727 | that are begung can potentially be zero: |
655 | |
728 | |
656 | my $cv = AnyEvent->condvar; |
729 | my $cv = AnyEvent->condvar; |
657 | |
730 | |
658 | my %result; |
731 | my %result; |
659 | $cv->begin (sub { $cv->send (\%result) }); |
732 | $cv->begin (sub { shift->send (\%result) }); |
660 | |
733 | |
661 | for my $host (@list_of_hosts) { |
734 | for my $host (@list_of_hosts) { |
662 | $cv->begin; |
735 | $cv->begin; |
663 | ping_host_then_call_callback $host, sub { |
736 | ping_host_then_call_callback $host, sub { |
664 | $result{$host} = ...; |
737 | $result{$host} = ...; |
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731 | |
804 | |
732 | $cb = $cv->cb ($cb->($cv)) |
805 | $cb = $cv->cb ($cb->($cv)) |
733 | This is a mutator function that returns the callback set and |
806 | This is a mutator function that returns the callback set and |
734 | optionally replaces it before doing so. |
807 | optionally replaces it before doing so. |
735 | |
808 | |
736 | The callback will be called when the condition becomes "true", i.e. |
809 | The callback will be called when the condition becomes (or already |
737 | when "send" or "croak" are called, with the only argument being the |
810 | was) "true", i.e. when "send" or "croak" are called (or were |
738 | condition variable itself. Calling "recv" inside the callback or at |
811 | called), with the only argument being the condition variable itself. |
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812 | Calling "recv" inside the callback or at any later time is |
739 | any later time is guaranteed not to block. |
813 | guaranteed not to block. |
740 | |
814 | |
741 | SUPPORTED EVENT LOOPS/BACKENDS |
815 | SUPPORTED EVENT LOOPS/BACKENDS |
742 | The available backend classes are (every class has its own manpage): |
816 | The available backend classes are (every class has its own manpage): |
743 | |
817 | |
744 | Backends that are autoprobed when no other event loop can be found. |
818 | Backends that are autoprobed when no other event loop can be found. |
745 | EV is the preferred backend when no other event loop seems to be in |
819 | EV is the preferred backend when no other event loop seems to be in |
746 | use. If EV is not installed, then AnyEvent will try Event, and, |
820 | use. If EV is not installed, then AnyEvent will fall back to its own |
747 | failing that, will fall back to its own pure-perl implementation, |
821 | pure-perl implementation, which is available everywhere as it comes |
748 | which is available everywhere as it comes with AnyEvent itself. |
822 | with AnyEvent itself. |
749 | |
823 | |
750 | AnyEvent::Impl::EV based on EV (interface to libev, best choice). |
824 | AnyEvent::Impl::EV based on EV (interface to libev, best choice). |
751 | AnyEvent::Impl::Event based on Event, very stable, few glitches. |
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752 | AnyEvent::Impl::Perl pure-perl implementation, fast and portable. |
825 | AnyEvent::Impl::Perl pure-perl implementation, fast and portable. |
753 | |
826 | |
754 | Backends that are transparently being picked up when they are used. |
827 | Backends that are transparently being picked up when they are used. |
755 | These will be used when they are currently loaded when the first |
828 | These will be used when they are currently loaded when the first |
756 | watcher is created, in which case it is assumed that the application |
829 | watcher is created, in which case it is assumed that the application |
757 | is using them. This means that AnyEvent will automatically pick the |
830 | is using them. This means that AnyEvent will automatically pick the |
758 | right backend when the main program loads an event module before |
831 | right backend when the main program loads an event module before |
759 | anything starts to create watchers. Nothing special needs to be done |
832 | anything starts to create watchers. Nothing special needs to be done |
760 | by the main program. |
833 | by the main program. |
761 | |
834 | |
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835 | AnyEvent::Impl::Event based on Event, very stable, few glitches. |
762 | AnyEvent::Impl::Glib based on Glib, slow but very stable. |
836 | AnyEvent::Impl::Glib based on Glib, slow but very stable. |
763 | AnyEvent::Impl::Tk based on Tk, very broken. |
837 | AnyEvent::Impl::Tk based on Tk, very broken. |
764 | AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse. |
838 | AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse. |
765 | AnyEvent::Impl::POE based on POE, very slow, some limitations. |
839 | AnyEvent::Impl::POE based on POE, very slow, some limitations. |
766 | AnyEvent::Impl::Irssi used when running within irssi. |
840 | AnyEvent::Impl::Irssi used when running within irssi. |
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865 | You should check $AnyEvent::MODEL before adding to this array, |
939 | You should check $AnyEvent::MODEL before adding to this array, |
866 | though: if it is defined then the event loop has already been |
940 | though: if it is defined then the event loop has already been |
867 | detected, and the array will be ignored. |
941 | detected, and the array will be ignored. |
868 | |
942 | |
869 | Best use "AnyEvent::post_detect { BLOCK }" when your application |
943 | Best use "AnyEvent::post_detect { BLOCK }" when your application |
870 | allows it,as it takes care of these details. |
944 | allows it, as it takes care of these details. |
871 | |
945 | |
872 | This variable is mainly useful for modules that can do something |
946 | This variable is mainly useful for modules that can do something |
873 | useful when AnyEvent is used and thus want to know when it is |
947 | useful when AnyEvent is used and thus want to know when it is |
874 | initialised, but do not need to even load it by default. This array |
948 | initialised, but do not need to even load it by default. This array |
875 | provides the means to hook into AnyEvent passively, without loading |
949 | provides the means to hook into AnyEvent passively, without loading |
876 | it. |
950 | it. |
|
|
951 | |
|
|
952 | Example: To load Coro::AnyEvent whenever Coro and AnyEvent are used |
|
|
953 | together, you could put this into Coro (this is the actual code used |
|
|
954 | by Coro to accomplish this): |
|
|
955 | |
|
|
956 | if (defined $AnyEvent::MODEL) { |
|
|
957 | # AnyEvent already initialised, so load Coro::AnyEvent |
|
|
958 | require Coro::AnyEvent; |
|
|
959 | } else { |
|
|
960 | # AnyEvent not yet initialised, so make sure to load Coro::AnyEvent |
|
|
961 | # as soon as it is |
|
|
962 | push @AnyEvent::post_detect, sub { require Coro::AnyEvent }; |
|
|
963 | } |
877 | |
964 | |
878 | WHAT TO DO IN A MODULE |
965 | WHAT TO DO IN A MODULE |
879 | As a module author, you should "use AnyEvent" and call AnyEvent methods |
966 | As a module author, you should "use AnyEvent" and call AnyEvent methods |
880 | freely, but you should not load a specific event module or rely on it. |
967 | freely, but you should not load a specific event module or rely on it. |
881 | |
968 | |
… | |
… | |
934 | |
1021 | |
935 | OTHER MODULES |
1022 | OTHER MODULES |
936 | The following is a non-exhaustive list of additional modules that use |
1023 | The following is a non-exhaustive list of additional modules that use |
937 | AnyEvent as a client and can therefore be mixed easily with other |
1024 | AnyEvent as a client and can therefore be mixed easily with other |
938 | AnyEvent modules and other event loops in the same program. Some of the |
1025 | AnyEvent modules and other event loops in the same program. Some of the |
939 | modules come with AnyEvent, most are available via CPAN. |
1026 | modules come as part of AnyEvent, the others are available via CPAN. |
940 | |
1027 | |
941 | AnyEvent::Util |
1028 | AnyEvent::Util |
942 | Contains various utility functions that replace often-used but |
1029 | Contains various utility functions that replace often-used but |
943 | blocking functions such as "inet_aton" by event-/callback-based |
1030 | blocking functions such as "inet_aton" by event-/callback-based |
944 | versions. |
1031 | versions. |
… | |
… | |
955 | transparent and non-blocking SSL/TLS (via AnyEvent::TLS. |
1042 | transparent and non-blocking SSL/TLS (via AnyEvent::TLS. |
956 | |
1043 | |
957 | AnyEvent::DNS |
1044 | AnyEvent::DNS |
958 | Provides rich asynchronous DNS resolver capabilities. |
1045 | Provides rich asynchronous DNS resolver capabilities. |
959 | |
1046 | |
|
|
1047 | AnyEvent::HTTP, AnyEvent::IRC, AnyEvent::XMPP, AnyEvent::GPSD, |
|
|
1048 | AnyEvent::IGS, AnyEvent::FCP |
|
|
1049 | Implement event-based interfaces to the protocols of the same name |
|
|
1050 | (for the curious, IGS is the International Go Server and FCP is the |
|
|
1051 | Freenet Client Protocol). |
|
|
1052 | |
|
|
1053 | AnyEvent::Handle::UDP |
|
|
1054 | Here be danger! |
|
|
1055 | |
|
|
1056 | As Pauli would put it, "Not only is it not right, it's not even |
|
|
1057 | wrong!" - there are so many things wrong with AnyEvent::Handle::UDP, |
|
|
1058 | most notably it's use of a stream-based API with a protocol that |
|
|
1059 | isn't streamable, that the only way to improve it is to delete it. |
|
|
1060 | |
|
|
1061 | It features data corruption (but typically only under load) and |
|
|
1062 | general confusion. On top, the author is not only clueless about UDP |
|
|
1063 | but also fact-resistant - some gems of his understanding: "connect |
|
|
1064 | doesn't work with UDP", "UDP packets are not IP packets", "UDP only |
|
|
1065 | has datagrams, not packets", "I don't need to implement proper error |
|
|
1066 | checking as UDP doesn't support error checking" and so on - he |
|
|
1067 | doesn't even understand what's wrong with his module when it is |
|
|
1068 | explained to him. |
|
|
1069 | |
960 | AnyEvent::HTTP |
1070 | AnyEvent::DBI |
961 | A simple-to-use HTTP library that is capable of making a lot of |
1071 | Executes DBI requests asynchronously in a proxy process for you, |
962 | concurrent HTTP requests. |
1072 | notifying you in an event-bnased way when the operation is finished. |
|
|
1073 | |
|
|
1074 | AnyEvent::AIO |
|
|
1075 | Truly asynchronous (as opposed to non-blocking) I/O, should be in |
|
|
1076 | the toolbox of every event programmer. AnyEvent::AIO transparently |
|
|
1077 | fuses IO::AIO and AnyEvent together, giving AnyEvent access to |
|
|
1078 | event-based file I/O, and much more. |
963 | |
1079 | |
964 | AnyEvent::HTTPD |
1080 | AnyEvent::HTTPD |
965 | Provides a simple web application server framework. |
1081 | A simple embedded webserver. |
966 | |
1082 | |
967 | AnyEvent::FastPing |
1083 | AnyEvent::FastPing |
968 | The fastest ping in the west. |
1084 | The fastest ping in the west. |
969 | |
1085 | |
970 | AnyEvent::DBI |
|
|
971 | Executes DBI requests asynchronously in a proxy process. |
|
|
972 | |
|
|
973 | AnyEvent::AIO |
|
|
974 | Truly asynchronous I/O, should be in the toolbox of every event |
|
|
975 | programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent |
|
|
976 | together. |
|
|
977 | |
|
|
978 | AnyEvent::BDB |
|
|
979 | Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently |
|
|
980 | fuses BDB and AnyEvent together. |
|
|
981 | |
|
|
982 | AnyEvent::GPSD |
|
|
983 | A non-blocking interface to gpsd, a daemon delivering GPS |
|
|
984 | information. |
|
|
985 | |
|
|
986 | AnyEvent::IRC |
|
|
987 | AnyEvent based IRC client module family (replacing the older |
|
|
988 | Net::IRC3). |
|
|
989 | |
|
|
990 | AnyEvent::XMPP |
|
|
991 | AnyEvent based XMPP (Jabber protocol) module family (replacing the |
|
|
992 | older Net::XMPP2>. |
|
|
993 | |
|
|
994 | AnyEvent::IGS |
|
|
995 | A non-blocking interface to the Internet Go Server protocol (used by |
|
|
996 | App::IGS). |
|
|
997 | |
|
|
998 | Net::FCP |
|
|
999 | AnyEvent-based implementation of the Freenet Client Protocol, |
|
|
1000 | birthplace of AnyEvent. |
|
|
1001 | |
|
|
1002 | Event::ExecFlow |
|
|
1003 | High level API for event-based execution flow control. |
|
|
1004 | |
|
|
1005 | Coro |
1086 | Coro |
1006 | Has special support for AnyEvent via Coro::AnyEvent. |
1087 | Has special support for AnyEvent via Coro::AnyEvent. |
|
|
1088 | |
|
|
1089 | SIMPLIFIED AE API |
|
|
1090 | Starting with version 5.0, AnyEvent officially supports a second, much |
|
|
1091 | simpler, API that is designed to reduce the calling, typing and memory |
|
|
1092 | overhead by using function call syntax and a fixed number of parameters. |
|
|
1093 | |
|
|
1094 | See the AE manpage for details. |
1007 | |
1095 | |
1008 | ERROR AND EXCEPTION HANDLING |
1096 | ERROR AND EXCEPTION HANDLING |
1009 | In general, AnyEvent does not do any error handling - it relies on the |
1097 | In general, AnyEvent does not do any error handling - it relies on the |
1010 | caller to do that if required. The AnyEvent::Strict module (see also the |
1098 | caller to do that if required. The AnyEvent::Strict module (see also the |
1011 | "PERL_ANYEVENT_STRICT" environment variable, below) provides strict |
1099 | "PERL_ANYEVENT_STRICT" environment variable, below) provides strict |
… | |
… | |
1190 | warn "read: $input\n"; # output what has been read |
1278 | warn "read: $input\n"; # output what has been read |
1191 | $cv->send if $input =~ /^q/i; # quit program if /^q/i |
1279 | $cv->send if $input =~ /^q/i; # quit program if /^q/i |
1192 | }, |
1280 | }, |
1193 | ); |
1281 | ); |
1194 | |
1282 | |
1195 | my $time_watcher; # can only be used once |
|
|
1196 | |
|
|
1197 | sub new_timer { |
|
|
1198 | $timer = AnyEvent->timer (after => 1, cb => sub { |
1283 | my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub { |
1199 | warn "timeout\n"; # print 'timeout' about every second |
1284 | warn "timeout\n"; # print 'timeout' at most every second |
1200 | &new_timer; # and restart the time |
|
|
1201 | }); |
|
|
1202 | } |
1285 | }); |
1203 | |
|
|
1204 | new_timer; # create first timer |
|
|
1205 | |
1286 | |
1206 | $cv->recv; # wait until user enters /^q/i |
1287 | $cv->recv; # wait until user enters /^q/i |
1207 | |
1288 | |
1208 | REAL-WORLD EXAMPLE |
1289 | REAL-WORLD EXAMPLE |
1209 | Consider the Net::FCP module. It features (among others) the following |
1290 | Consider the Net::FCP module. It features (among others) the following |
… | |
… | |
1281 | |
1362 | |
1282 | The actual code goes further and collects all errors ("die"s, |
1363 | The actual code goes further and collects all errors ("die"s, |
1283 | exceptions) that occurred during request processing. The "result" method |
1364 | exceptions) that occurred during request processing. The "result" method |
1284 | detects whether an exception as thrown (it is stored inside the $txn |
1365 | detects whether an exception as thrown (it is stored inside the $txn |
1285 | object) and just throws the exception, which means connection errors and |
1366 | object) and just throws the exception, which means connection errors and |
1286 | other problems get reported tot he code that tries to use the result, |
1367 | other problems get reported to the code that tries to use the result, |
1287 | not in a random callback. |
1368 | not in a random callback. |
1288 | |
1369 | |
1289 | All of this enables the following usage styles: |
1370 | All of this enables the following usage styles: |
1290 | |
1371 | |
1291 | 1. Blocking: |
1372 | 1. Blocking: |
… | |
… | |
1336 | through AnyEvent. The benchmark creates a lot of timers (with a zero |
1417 | through AnyEvent. The benchmark creates a lot of timers (with a zero |
1337 | timeout) and I/O watchers (watching STDOUT, a pty, to become writable, |
1418 | timeout) and I/O watchers (watching STDOUT, a pty, to become writable, |
1338 | which it is), lets them fire exactly once and destroys them again. |
1419 | which it is), lets them fire exactly once and destroys them again. |
1339 | |
1420 | |
1340 | Source code for this benchmark is found as eg/bench in the AnyEvent |
1421 | Source code for this benchmark is found as eg/bench in the AnyEvent |
1341 | distribution. |
1422 | distribution. It uses the AE interface, which makes a real difference |
|
|
1423 | for the EV and Perl backends only. |
1342 | |
1424 | |
1343 | Explanation of the columns |
1425 | Explanation of the columns |
1344 | *watcher* is the number of event watchers created/destroyed. Since |
1426 | *watcher* is the number of event watchers created/destroyed. Since |
1345 | different event models feature vastly different performances, each event |
1427 | different event models feature vastly different performances, each event |
1346 | loop was given a number of watchers so that overall runtime is |
1428 | loop was given a number of watchers so that overall runtime is |
… | |
… | |
1365 | *destroy* is the time, in microseconds, that it takes to destroy a |
1447 | *destroy* is the time, in microseconds, that it takes to destroy a |
1366 | single watcher. |
1448 | single watcher. |
1367 | |
1449 | |
1368 | Results |
1450 | Results |
1369 | name watchers bytes create invoke destroy comment |
1451 | name watchers bytes create invoke destroy comment |
1370 | EV/EV 400000 224 0.47 0.35 0.27 EV native interface |
1452 | EV/EV 100000 223 0.47 0.43 0.27 EV native interface |
1371 | EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers |
1453 | EV/Any 100000 223 0.48 0.42 0.26 EV + AnyEvent watchers |
1372 | CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal |
1454 | Coro::EV/Any 100000 223 0.47 0.42 0.26 coroutines + Coro::Signal |
1373 | Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation |
1455 | Perl/Any 100000 431 2.70 0.74 0.92 pure perl implementation |
1374 | Event/Event 16000 517 32.20 31.80 0.81 Event native interface |
1456 | Event/Event 16000 516 31.16 31.84 0.82 Event native interface |
1375 | Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers |
1457 | Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers |
1376 | IOAsync/Any 16000 989 38.10 32.77 11.13 via IO::Async::Loop::IO_Poll |
1458 | IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll |
1377 | IOAsync/Any 16000 990 37.59 29.50 10.61 via IO::Async::Loop::Epoll |
1459 | IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll |
1378 | Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour |
1460 | Glib/Any 16000 1118 89.00 12.57 51.17 quadratic behaviour |
1379 | Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers |
1461 | Tk/Any 2000 1346 20.96 10.75 8.00 SEGV with >> 2000 watchers |
1380 | POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event |
1462 | POE/Any 2000 6951 108.97 795.32 14.24 via POE::Loop::Event |
1381 | POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select |
1463 | POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select |
1382 | |
1464 | |
1383 | Discussion |
1465 | Discussion |
1384 | The benchmark does *not* measure scalability of the event loop very |
1466 | The benchmark does *not* measure scalability of the event loop very |
1385 | well. For example, a select-based event loop (such as the pure perl one) |
1467 | well. For example, a select-based event loop (such as the pure perl one) |
1386 | can never compete with an event loop that uses epoll when the number of |
1468 | can never compete with an event loop that uses epoll when the number of |
… | |
… | |
1397 | benchmark machine, handling an event takes roughly 1600 CPU cycles with |
1479 | benchmark machine, handling an event takes roughly 1600 CPU cycles with |
1398 | EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 |
1480 | EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 |
1399 | CPU cycles with POE. |
1481 | CPU cycles with POE. |
1400 | |
1482 | |
1401 | "EV" is the sole leader regarding speed and memory use, which are both |
1483 | "EV" is the sole leader regarding speed and memory use, which are both |
1402 | maximal/minimal, respectively. Even when going through AnyEvent, it uses |
1484 | maximal/minimal, respectively. When using the AE API there is zero |
|
|
1485 | overhead (when going through the AnyEvent API create is about 5-6 times |
|
|
1486 | slower, with other times being equal, so still uses far less memory than |
1403 | far less memory than any other event loop and is still faster than Event |
1487 | any other event loop and is still faster than Event natively). |
1404 | natively. |
|
|
1405 | |
1488 | |
1406 | The pure perl implementation is hit in a few sweet spots (both the |
1489 | The pure perl implementation is hit in a few sweet spots (both the |
1407 | constant timeout and the use of a single fd hit optimisations in the |
1490 | constant timeout and the use of a single fd hit optimisations in the |
1408 | perl interpreter and the backend itself). Nevertheless this shows that |
1491 | perl interpreter and the backend itself). Nevertheless this shows that |
1409 | it adds very little overhead in itself. Like any select-based backend |
1492 | it adds very little overhead in itself. Like any select-based backend |
… | |
… | |
1479 | In this benchmark, we use 10000 socket pairs (20000 sockets), of which |
1562 | In this benchmark, we use 10000 socket pairs (20000 sockets), of which |
1480 | 100 (1%) are active. This mirrors the activity of large servers with |
1563 | 100 (1%) are active. This mirrors the activity of large servers with |
1481 | many connections, most of which are idle at any one point in time. |
1564 | many connections, most of which are idle at any one point in time. |
1482 | |
1565 | |
1483 | Source code for this benchmark is found as eg/bench2 in the AnyEvent |
1566 | Source code for this benchmark is found as eg/bench2 in the AnyEvent |
1484 | distribution. |
1567 | distribution. It uses the AE interface, which makes a real difference |
|
|
1568 | for the EV and Perl backends only. |
1485 | |
1569 | |
1486 | Explanation of the columns |
1570 | Explanation of the columns |
1487 | *sockets* is the number of sockets, and twice the number of "servers" |
1571 | *sockets* is the number of sockets, and twice the number of "servers" |
1488 | (as each server has a read and write socket end). |
1572 | (as each server has a read and write socket end). |
1489 | |
1573 | |
… | |
… | |
1495 | forwarding it to another server. This includes deleting the old timeout |
1579 | forwarding it to another server. This includes deleting the old timeout |
1496 | and creating a new one that moves the timeout into the future. |
1580 | and creating a new one that moves the timeout into the future. |
1497 | |
1581 | |
1498 | Results |
1582 | Results |
1499 | name sockets create request |
1583 | name sockets create request |
1500 | EV 20000 69.01 11.16 |
1584 | EV 20000 62.66 7.99 |
1501 | Perl 20000 73.32 35.87 |
1585 | Perl 20000 68.32 32.64 |
1502 | IOAsync 20000 157.00 98.14 epoll |
1586 | IOAsync 20000 174.06 101.15 epoll |
1503 | IOAsync 20000 159.31 616.06 poll |
1587 | IOAsync 20000 174.67 610.84 poll |
1504 | Event 20000 212.62 257.32 |
1588 | Event 20000 202.69 242.91 |
1505 | Glib 20000 651.16 1896.30 |
1589 | Glib 20000 557.01 1689.52 |
1506 | POE 20000 349.67 12317.24 uses POE::Loop::Event |
1590 | POE 20000 341.54 12086.32 uses POE::Loop::Event |
1507 | |
1591 | |
1508 | Discussion |
1592 | Discussion |
1509 | This benchmark *does* measure scalability and overall performance of the |
1593 | This benchmark *does* measure scalability and overall performance of the |
1510 | particular event loop. |
1594 | particular event loop. |
1511 | |
1595 | |
… | |
… | |
1624 | As you can see, the AnyEvent + EV combination even beats the |
1708 | As you can see, the AnyEvent + EV combination even beats the |
1625 | hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl |
1709 | hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl |
1626 | backend easily beats IO::Lambda and POE. |
1710 | backend easily beats IO::Lambda and POE. |
1627 | |
1711 | |
1628 | And even the 100% non-blocking version written using the high-level (and |
1712 | And even the 100% non-blocking version written using the high-level (and |
1629 | slow :) AnyEvent::Handle abstraction beats both POE and IO::Lambda by a |
1713 | slow :) AnyEvent::Handle abstraction beats both POE and IO::Lambda |
1630 | large margin, even though it does all of DNS, tcp-connect and socket I/O |
1714 | higher level ("unoptimised") abstractions by a large margin, even though |
1631 | in a non-blocking way. |
1715 | it does all of DNS, tcp-connect and socket I/O in a non-blocking way. |
1632 | |
1716 | |
1633 | The two AnyEvent benchmarks programs can be found as eg/ae0.pl and |
1717 | The two AnyEvent benchmarks programs can be found as eg/ae0.pl and |
1634 | eg/ae2.pl in the AnyEvent distribution, the remaining benchmarks are |
1718 | eg/ae2.pl in the AnyEvent distribution, the remaining benchmarks are |
1635 | part of the IO::lambda distribution and were used without any changes. |
1719 | part of the IO::Lambda distribution and were used without any changes. |
1636 | |
1720 | |
1637 | SIGNALS |
1721 | SIGNALS |
1638 | AnyEvent currently installs handlers for these signals: |
1722 | AnyEvent currently installs handlers for these signals: |
1639 | |
1723 | |
1640 | SIGCHLD |
1724 | SIGCHLD |
… | |
… | |
1667 | it's built-in modules) are required to use it. |
1751 | it's built-in modules) are required to use it. |
1668 | |
1752 | |
1669 | That does not mean that AnyEvent won't take advantage of some additional |
1753 | That does not mean that AnyEvent won't take advantage of some additional |
1670 | modules if they are installed. |
1754 | modules if they are installed. |
1671 | |
1755 | |
1672 | This section epxlains which additional modules will be used, and how |
1756 | This section explains which additional modules will be used, and how |
1673 | they affect AnyEvent's operetion. |
1757 | they affect AnyEvent's operation. |
1674 | |
1758 | |
1675 | Async::Interrupt |
1759 | Async::Interrupt |
1676 | This slightly arcane module is used to implement fast signal |
1760 | This slightly arcane module is used to implement fast signal |
1677 | handling: To my knowledge, there is no way to do completely |
1761 | handling: To my knowledge, there is no way to do completely |
1678 | race-free and quick signal handling in pure perl. To ensure that |
1762 | race-free and quick signal handling in pure perl. To ensure that |
… | |
… | |
1681 | 10 seconds, look for $AnyEvent::MAX_SIGNAL_LATENCY). |
1765 | 10 seconds, look for $AnyEvent::MAX_SIGNAL_LATENCY). |
1682 | |
1766 | |
1683 | If this module is available, then it will be used to implement |
1767 | If this module is available, then it will be used to implement |
1684 | signal catching, which means that signals will not be delayed, and |
1768 | signal catching, which means that signals will not be delayed, and |
1685 | the event loop will not be interrupted regularly, which is more |
1769 | the event loop will not be interrupted regularly, which is more |
1686 | efficient (And good for battery life on laptops). |
1770 | efficient (and good for battery life on laptops). |
1687 | |
1771 | |
1688 | This affects not just the pure-perl event loop, but also other event |
1772 | This affects not just the pure-perl event loop, but also other event |
1689 | loops that have no signal handling on their own (e.g. Glib, Tk, Qt). |
1773 | loops that have no signal handling on their own (e.g. Glib, Tk, Qt). |
1690 | |
1774 | |
1691 | Some event loops (POE, Event, Event::Lib) offer signal watchers |
1775 | Some event loops (POE, Event, Event::Lib) offer signal watchers |
… | |
… | |
1701 | clock is available, can take avdantage of advanced kernel interfaces |
1785 | clock is available, can take avdantage of advanced kernel interfaces |
1702 | such as "epoll" and "kqueue", and is the fastest backend *by far*. |
1786 | such as "epoll" and "kqueue", and is the fastest backend *by far*. |
1703 | You can even embed Glib/Gtk2 in it (or vice versa, see EV::Glib and |
1787 | You can even embed Glib/Gtk2 in it (or vice versa, see EV::Glib and |
1704 | Glib::EV). |
1788 | Glib::EV). |
1705 | |
1789 | |
|
|
1790 | If you only use backends that rely on another event loop (e.g. |
|
|
1791 | "Tk"), then this module will do nothing for you. |
|
|
1792 | |
1706 | Guard |
1793 | Guard |
1707 | The guard module, when used, will be used to implement |
1794 | The guard module, when used, will be used to implement |
1708 | "AnyEvent::Util::guard". This speeds up guards considerably (and |
1795 | "AnyEvent::Util::guard". This speeds up guards considerably (and |
1709 | uses a lot less memory), but otherwise doesn't affect guard |
1796 | uses a lot less memory), but otherwise doesn't affect guard |
1710 | operation much. It is purely used for performance. |
1797 | operation much. It is purely used for performance. |
1711 | |
1798 | |
1712 | JSON and JSON::XS |
1799 | JSON and JSON::XS |
1713 | This module is required when you want to read or write JSON data via |
1800 | One of these modules is required when you want to read or write JSON |
1714 | AnyEvent::Handle. It is also written in pure-perl, but can take |
1801 | data via AnyEvent::Handle. JSON is also written in pure-perl, but |
1715 | advantage of the ultra-high-speed JSON::XS module when it is |
1802 | can take advantage of the ultra-high-speed JSON::XS module when it |
1716 | installed. |
1803 | is installed. |
1717 | |
|
|
1718 | In fact, AnyEvent::Handle will use JSON::XS by default if it is |
|
|
1719 | installed. |
|
|
1720 | |
1804 | |
1721 | Net::SSLeay |
1805 | Net::SSLeay |
1722 | Implementing TLS/SSL in Perl is certainly interesting, but not very |
1806 | Implementing TLS/SSL in Perl is certainly interesting, but not very |
1723 | worthwhile: If this module is installed, then AnyEvent::Handle (with |
1807 | worthwhile: If this module is installed, then AnyEvent::Handle (with |
1724 | the help of AnyEvent::TLS), gains the ability to do TLS/SSL. |
1808 | the help of AnyEvent::TLS), gains the ability to do TLS/SSL. |
… | |
… | |
1730 | additionally use it to try to use a monotonic clock for timing |
1814 | additionally use it to try to use a monotonic clock for timing |
1731 | stability. |
1815 | stability. |
1732 | |
1816 | |
1733 | FORK |
1817 | FORK |
1734 | Most event libraries are not fork-safe. The ones who are usually are |
1818 | Most event libraries are not fork-safe. The ones who are usually are |
1735 | because they rely on inefficient but fork-safe "select" or "poll" calls. |
1819 | because they rely on inefficient but fork-safe "select" or "poll" calls |
1736 | Only EV is fully fork-aware. |
1820 | - higher performance APIs such as BSD's kqueue or the dreaded Linux |
|
|
1821 | epoll are usually badly thought-out hacks that are incompatible with |
|
|
1822 | fork in one way or another. Only EV is fully fork-aware and ensures that |
|
|
1823 | you continue event-processing in both parent and child (or both, if you |
|
|
1824 | know what you are doing). |
|
|
1825 | |
|
|
1826 | This means that, in general, you cannot fork and do event processing in |
|
|
1827 | the child if the event library was initialised before the fork (which |
|
|
1828 | usually happens when the first AnyEvent watcher is created, or the |
|
|
1829 | library is loaded). |
1737 | |
1830 | |
1738 | If you have to fork, you must either do so *before* creating your first |
1831 | If you have to fork, you must either do so *before* creating your first |
1739 | watcher OR you must not use AnyEvent at all in the child OR you must do |
1832 | watcher OR you must not use AnyEvent at all in the child OR you must do |
1740 | something completely out of the scope of AnyEvent. |
1833 | something completely out of the scope of AnyEvent. |
|
|
1834 | |
|
|
1835 | The problem of doing event processing in the parent *and* the child is |
|
|
1836 | much more complicated: even for backends that *are* fork-aware or |
|
|
1837 | fork-safe, their behaviour is not usually what you want: fork clones all |
|
|
1838 | watchers, that means all timers, I/O watchers etc. are active in both |
|
|
1839 | parent and child, which is almost never what you want. USing "exec" to |
|
|
1840 | start worker children from some kind of manage rprocess is usually |
|
|
1841 | preferred, because it is much easier and cleaner, at the expense of |
|
|
1842 | having to have another binary. |
1741 | |
1843 | |
1742 | SECURITY CONSIDERATIONS |
1844 | SECURITY CONSIDERATIONS |
1743 | AnyEvent can be forced to load any event model via |
1845 | AnyEvent can be forced to load any event model via |
1744 | $ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used |
1846 | $ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used |
1745 | to execute arbitrary code or directly gain access, it can easily be used |
1847 | to execute arbitrary code or directly gain access, it can easily be used |