1 | =head1 NAME |
1 | =head1 NAME |
2 | |
2 | |
3 | AnyEvent - provide framework for multiple event loops |
3 | AnyEvent - provide framework for multiple event loops |
4 | |
4 | |
5 | EV, Event, Coro::EV, Coro::Event, Glib, Tk, Perl - various supported event loops |
5 | EV, Event, Coro::EV, Coro::Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event loops |
6 | |
6 | |
7 | =head1 SYNOPSIS |
7 | =head1 SYNOPSIS |
8 | |
8 | |
9 | use AnyEvent; |
9 | use AnyEvent; |
10 | |
10 | |
… | |
… | |
80 | module. |
80 | module. |
81 | |
81 | |
82 | During the first call of any watcher-creation method, the module tries |
82 | During the first call of any watcher-creation method, the module tries |
83 | to detect the currently loaded event loop by probing whether one of the |
83 | to detect the currently loaded event loop by probing whether one of the |
84 | following modules is already loaded: L<Coro::EV>, L<Coro::Event>, L<EV>, |
84 | following modules is already loaded: L<Coro::EV>, L<Coro::Event>, L<EV>, |
85 | L<Event>, L<Glib>, L<Tk>. The first one found is used. If none are found, |
85 | L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>, |
86 | the module tries to load these modules in the stated order. The first one |
86 | L<POE>. The first one found is used. If none are found, the module tries |
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87 | to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl |
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88 | adaptor should always succeed) in the order given. The first one that can |
87 | that can be successfully loaded will be used. If, after this, still none |
89 | be successfully loaded will be used. If, after this, still none could be |
88 | could be found, AnyEvent will fall back to a pure-perl event loop, which |
90 | found, AnyEvent will fall back to a pure-perl event loop, which is not |
89 | is not very efficient, but should work everywhere. |
91 | very efficient, but should work everywhere. |
90 | |
92 | |
91 | Because AnyEvent first checks for modules that are already loaded, loading |
93 | Because AnyEvent first checks for modules that are already loaded, loading |
92 | an event model explicitly before first using AnyEvent will likely make |
94 | an event model explicitly before first using AnyEvent will likely make |
93 | that model the default. For example: |
95 | that model the default. For example: |
94 | |
96 | |
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134 | |
136 | |
135 | Note that C<my $w; $w => combination. This is necessary because in Perl, |
137 | Note that C<my $w; $w => combination. This is necessary because in Perl, |
136 | my variables are only visible after the statement in which they are |
138 | my variables are only visible after the statement in which they are |
137 | declared. |
139 | declared. |
138 | |
140 | |
139 | =head2 IO WATCHERS |
141 | =head2 I/O WATCHERS |
140 | |
142 | |
141 | You can create an I/O watcher by calling the C<< AnyEvent->io >> method |
143 | You can create an I/O watcher by calling the C<< AnyEvent->io >> method |
142 | with the following mandatory key-value pairs as arguments: |
144 | with the following mandatory key-value pairs as arguments: |
143 | |
145 | |
144 | C<fh> the Perl I<file handle> (I<not> file descriptor) to watch for |
146 | C<fh> the Perl I<file handle> (I<not> file descriptor) to watch for |
145 | events. C<poll> must be a string that is either C<r> or C<w>, which |
147 | events. C<poll> must be a string that is either C<r> or C<w>, which |
146 | creates a watcher waiting for "r"eadable or "w"ritable events, |
148 | creates a watcher waiting for "r"eadable or "w"ritable events, |
147 | respectively. C<cb> is the callback to invoke each time the file handle |
149 | respectively. C<cb> is the callback to invoke each time the file handle |
148 | becomes ready. |
150 | becomes ready. |
149 | |
151 | |
150 | File handles will be kept alive, so as long as the watcher exists, the |
152 | The I/O watcher might use the underlying file descriptor or a copy of it. |
151 | file handle exists, too. |
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152 | |
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153 | It is not allowed to close a file handle as long as any watcher is active |
153 | It is not allowed to close a file handle as long as any watcher is active |
154 | on the underlying file descriptor. |
154 | on the underlying file descriptor. |
155 | |
155 | |
156 | Some event loops issue spurious readyness notifications, so you should |
156 | Some event loops issue spurious readyness notifications, so you should |
157 | always use non-blocking calls when reading/writing from/to your file |
157 | always use non-blocking calls when reading/writing from/to your file |
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206 | |
206 | |
207 | There are two ways to handle timers: based on real time (relative, "fire |
207 | There are two ways to handle timers: based on real time (relative, "fire |
208 | in 10 seconds") and based on wallclock time (absolute, "fire at 12 |
208 | in 10 seconds") and based on wallclock time (absolute, "fire at 12 |
209 | o'clock"). |
209 | o'clock"). |
210 | |
210 | |
211 | While most event loops expect timers to specified in a relative way, they use |
211 | While most event loops expect timers to specified in a relative way, they |
212 | absolute time internally. This makes a difference when your clock "jumps", |
212 | use absolute time internally. This makes a difference when your clock |
213 | for example, when ntp decides to set your clock backwards from the wrong 2014-01-01 to |
213 | "jumps", for example, when ntp decides to set your clock backwards from |
214 | 2008-01-01, a watcher that you created to fire "after" a second might actually take |
214 | the wrong date of 2014-01-01 to 2008-01-01, a watcher that is supposed to |
215 | six years to finally fire. |
215 | fire "after" a second might actually take six years to finally fire. |
216 | |
216 | |
217 | AnyEvent cannot compensate for this. The only event loop that is conscious |
217 | AnyEvent cannot compensate for this. The only event loop that is conscious |
218 | about these issues is L<EV>, which offers both relative (ev_timer) and |
218 | about these issues is L<EV>, which offers both relative (ev_timer, based |
219 | absolute (ev_periodic) timers. |
219 | on true relative time) and absolute (ev_periodic, based on wallclock time) |
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220 | timers. |
220 | |
221 | |
221 | AnyEvent always prefers relative timers, if available, matching the |
222 | AnyEvent always prefers relative timers, if available, matching the |
222 | AnyEvent API. |
223 | AnyEvent API. |
223 | |
224 | |
224 | =head2 SIGNAL WATCHERS |
225 | =head2 SIGNAL WATCHERS |
225 | |
226 | |
226 | You can watch for signals using a signal watcher, C<signal> is the signal |
227 | You can watch for signals using a signal watcher, C<signal> is the signal |
227 | I<name> without any C<SIG> prefix, C<cb> is the Perl callback to |
228 | I<name> without any C<SIG> prefix, C<cb> is the Perl callback to |
228 | be invoked whenever a signal occurs. |
229 | be invoked whenever a signal occurs. |
229 | |
230 | |
230 | Multiple signals occurances can be clumped together into one callback |
231 | Multiple signal occurances can be clumped together into one callback |
231 | invocation, and callback invocation will be synchronous. synchronous means |
232 | invocation, and callback invocation will be synchronous. synchronous means |
232 | that it might take a while until the signal gets handled by the process, |
233 | that it might take a while until the signal gets handled by the process, |
233 | but it is guarenteed not to interrupt any other callbacks. |
234 | but it is guarenteed not to interrupt any other callbacks. |
234 | |
235 | |
235 | The main advantage of using these watchers is that you can share a signal |
236 | The main advantage of using these watchers is that you can share a signal |
… | |
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250 | watches for any child process exit). The watcher will trigger as often |
251 | watches for any child process exit). The watcher will trigger as often |
251 | as status change for the child are received. This works by installing a |
252 | as status change for the child are received. This works by installing a |
252 | signal handler for C<SIGCHLD>. The callback will be called with the pid |
253 | signal handler for C<SIGCHLD>. The callback will be called with the pid |
253 | and exit status (as returned by waitpid). |
254 | and exit status (as returned by waitpid). |
254 | |
255 | |
255 | Example: wait for pid 1333 |
256 | There is a slight catch to child watchers, however: you usually start them |
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257 | I<after> the child process was created, and this means the process could |
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258 | have exited already (and no SIGCHLD will be sent anymore). |
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259 | |
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260 | Not all event models handle this correctly (POE doesn't), but even for |
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261 | event models that I<do> handle this correctly, they usually need to be |
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262 | loaded before the process exits (i.e. before you fork in the first place). |
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263 | |
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264 | This means you cannot create a child watcher as the very first thing in an |
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265 | AnyEvent program, you I<have> to create at least one watcher before you |
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266 | C<fork> the child (alternatively, you can call C<AnyEvent::detect>). |
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267 | |
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268 | Example: fork a process and wait for it |
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269 | |
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270 | my $done = AnyEvent->condvar; |
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271 | |
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272 | AnyEvent::detect; # force event module to be initialised |
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273 | |
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274 | my $pid = fork or exit 5; |
256 | |
275 | |
257 | my $w = AnyEvent->child ( |
276 | my $w = AnyEvent->child ( |
258 | pid => 1333, |
277 | pid => $pid, |
259 | cb => sub { |
278 | cb => sub { |
260 | my ($pid, $status) = @_; |
279 | my ($pid, $status) = @_; |
261 | warn "pid $pid exited with status $status"; |
280 | warn "pid $pid exited with status $status"; |
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281 | $done->broadcast; |
262 | }, |
282 | }, |
263 | ); |
283 | ); |
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284 | |
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285 | # do something else, then wait for process exit |
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286 | $done->wait; |
264 | |
287 | |
265 | =head2 CONDITION VARIABLES |
288 | =head2 CONDITION VARIABLES |
266 | |
289 | |
267 | Condition variables can be created by calling the C<< AnyEvent->condvar >> |
290 | Condition variables can be created by calling the C<< AnyEvent->condvar >> |
268 | method without any arguments. |
291 | method without any arguments. |
… | |
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353 | |
376 | |
354 | The known classes so far are: |
377 | The known classes so far are: |
355 | |
378 | |
356 | AnyEvent::Impl::CoroEV based on Coro::EV, best choice. |
379 | AnyEvent::Impl::CoroEV based on Coro::EV, best choice. |
357 | AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice. |
380 | AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice. |
358 | AnyEvent::Impl::EV based on EV (an interface to libev, also best choice). |
381 | AnyEvent::Impl::EV based on EV (an interface to libev, best choice). |
359 | AnyEvent::Impl::Event based on Event, also second best choice :) |
382 | AnyEvent::Impl::Event based on Event, second best choice. |
360 | AnyEvent::Impl::Glib based on Glib, third-best choice. |
383 | AnyEvent::Impl::Glib based on Glib, third-best choice. |
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384 | AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable. |
361 | AnyEvent::Impl::Tk based on Tk, very bad choice. |
385 | AnyEvent::Impl::Tk based on Tk, very bad choice. |
362 | AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable. |
386 | AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs). |
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387 | AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse. |
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388 | AnyEvent::Impl::POE based on POE, not generic enough for full support. |
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389 | |
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390 | There is no support for WxWidgets, as WxWidgets has no support for |
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391 | watching file handles. However, you can use WxWidgets through the |
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392 | POE Adaptor, as POE has a Wx backend that simply polls 20 times per |
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393 | second, which was considered to be too horrible to even consider for |
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394 | AnyEvent. Likewise, other POE backends can be used by AnyEvent by using |
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395 | it's adaptor. |
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396 | |
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397 | AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when |
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398 | autodetecting them. |
363 | |
399 | |
364 | =item AnyEvent::detect |
400 | =item AnyEvent::detect |
365 | |
401 | |
366 | Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model |
402 | Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model |
367 | if necessary. You should only call this function right before you would |
403 | if necessary. You should only call this function right before you would |
… | |
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418 | no warnings; |
454 | no warnings; |
419 | use strict; |
455 | use strict; |
420 | |
456 | |
421 | use Carp; |
457 | use Carp; |
422 | |
458 | |
423 | our $VERSION = '3.12'; |
459 | our $VERSION = '3.3'; |
424 | our $MODEL; |
460 | our $MODEL; |
425 | |
461 | |
426 | our $AUTOLOAD; |
462 | our $AUTOLOAD; |
427 | our @ISA; |
463 | our @ISA; |
428 | |
464 | |
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435 | [Coro::Event:: => AnyEvent::Impl::CoroEvent::], |
471 | [Coro::Event:: => AnyEvent::Impl::CoroEvent::], |
436 | [EV:: => AnyEvent::Impl::EV::], |
472 | [EV:: => AnyEvent::Impl::EV::], |
437 | [Event:: => AnyEvent::Impl::Event::], |
473 | [Event:: => AnyEvent::Impl::Event::], |
438 | [Glib:: => AnyEvent::Impl::Glib::], |
474 | [Glib:: => AnyEvent::Impl::Glib::], |
439 | [Tk:: => AnyEvent::Impl::Tk::], |
475 | [Tk:: => AnyEvent::Impl::Tk::], |
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476 | [Wx:: => AnyEvent::Impl::POE::], |
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477 | [Prima:: => AnyEvent::Impl::POE::], |
440 | [AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::], |
478 | [AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::], |
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479 | # everything below here will not be autoprobed as the pureperl backend should work everywhere |
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480 | [Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy |
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481 | [Qt:: => AnyEvent::Impl::Qt::], # requires special main program |
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482 | [POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza |
441 | ); |
483 | ); |
442 | |
484 | |
443 | our %method = map +($_ => 1), qw(io timer condvar broadcast wait signal one_event DESTROY); |
485 | our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY); |
444 | |
486 | |
445 | sub detect() { |
487 | sub detect() { |
446 | unless ($MODEL) { |
488 | unless ($MODEL) { |
447 | no strict 'refs'; |
489 | no strict 'refs'; |
448 | |
490 | |
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491 | if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) { |
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492 | my $model = "AnyEvent::Impl::$1"; |
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493 | if (eval "require $model") { |
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494 | $MODEL = $model; |
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495 | warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1; |
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496 | } else { |
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497 | warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose; |
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498 | } |
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499 | } |
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500 | |
449 | # check for already loaded models |
501 | # check for already loaded models |
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502 | unless ($MODEL) { |
450 | for (@REGISTRY, @models) { |
503 | for (@REGISTRY, @models) { |
451 | my ($package, $model) = @$_; |
504 | my ($package, $model) = @$_; |
452 | if (${"$package\::VERSION"} > 0) { |
505 | if (${"$package\::VERSION"} > 0) { |
453 | if (eval "require $model") { |
506 | if (eval "require $model") { |
454 | $MODEL = $model; |
507 | $MODEL = $model; |
455 | warn "AnyEvent: found model '$model', using it.\n" if $verbose > 1; |
508 | warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1; |
456 | last; |
509 | last; |
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510 | } |
457 | } |
511 | } |
458 | } |
512 | } |
459 | } |
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460 | |
513 | |
461 | unless ($MODEL) { |
514 | unless ($MODEL) { |
462 | # try to load a model |
515 | # try to load a model |
463 | |
516 | |
464 | for (@REGISTRY, @models) { |
517 | for (@REGISTRY, @models) { |
465 | my ($package, $model) = @$_; |
518 | my ($package, $model) = @$_; |
466 | if (eval "require $package" |
519 | if (eval "require $package" |
467 | and ${"$package\::VERSION"} > 0 |
520 | and ${"$package\::VERSION"} > 0 |
468 | and eval "require $model") { |
521 | and eval "require $model") { |
469 | $MODEL = $model; |
522 | $MODEL = $model; |
470 | warn "AnyEvent: autoprobed and loaded model '$model', using it.\n" if $verbose > 1; |
523 | warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1; |
471 | last; |
524 | last; |
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525 | } |
472 | } |
526 | } |
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527 | |
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528 | $MODEL |
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529 | or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV (or Coro+EV), Event (or Coro+Event) or Glib."; |
473 | } |
530 | } |
474 | |
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475 | $MODEL |
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476 | or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV (or Coro+EV), Event (or Coro+Event), Glib or Tk."; |
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477 | } |
531 | } |
478 | |
532 | |
479 | unshift @ISA, $MODEL; |
533 | unshift @ISA, $MODEL; |
480 | push @{"$MODEL\::ISA"}, "AnyEvent::Base"; |
534 | push @{"$MODEL\::ISA"}, "AnyEvent::Base"; |
481 | } |
535 | } |
… | |
… | |
637 | |
691 | |
638 | =head1 ENVIRONMENT VARIABLES |
692 | =head1 ENVIRONMENT VARIABLES |
639 | |
693 | |
640 | The following environment variables are used by this module: |
694 | The following environment variables are used by this module: |
641 | |
695 | |
642 | C<PERL_ANYEVENT_VERBOSE> when set to C<2> or higher, cause AnyEvent to |
696 | =over 4 |
643 | report to STDERR which event model it chooses. |
697 | |
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698 | =item C<PERL_ANYEVENT_VERBOSE> |
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699 | |
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700 | By default, AnyEvent will be completely silent except in fatal |
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701 | conditions. You can set this environment variable to make AnyEvent more |
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702 | talkative. |
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703 | |
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704 | When set to C<1> or higher, causes AnyEvent to warn about unexpected |
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705 | conditions, such as not being able to load the event model specified by |
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706 | C<PERL_ANYEVENT_MODEL>. |
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707 | |
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708 | When set to C<2> or higher, cause AnyEvent to report to STDERR which event |
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709 | model it chooses. |
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710 | |
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711 | =item C<PERL_ANYEVENT_MODEL> |
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712 | |
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713 | This can be used to specify the event model to be used by AnyEvent, before |
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714 | autodetection and -probing kicks in. It must be a string consisting |
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715 | entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended |
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716 | and the resulting module name is loaded and if the load was successful, |
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717 | used as event model. If it fails to load AnyEvent will proceed with |
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718 | autodetection and -probing. |
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719 | |
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720 | This functionality might change in future versions. |
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721 | |
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722 | For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you |
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723 | could start your program like this: |
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724 | |
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725 | PERL_ANYEVENT_MODEL=Perl perl ... |
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726 | |
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727 | =back |
644 | |
728 | |
645 | =head1 EXAMPLE PROGRAM |
729 | =head1 EXAMPLE PROGRAM |
646 | |
730 | |
647 | The following program uses an IO watcher to read data from STDIN, a timer |
731 | The following program uses an I/O watcher to read data from STDIN, a timer |
648 | to display a message once per second, and a condition variable to quit the |
732 | to display a message once per second, and a condition variable to quit the |
649 | program when the user enters quit: |
733 | program when the user enters quit: |
650 | |
734 | |
651 | use AnyEvent; |
735 | use AnyEvent; |
652 | |
736 | |
… | |
… | |
796 | $quit->broadcast; |
880 | $quit->broadcast; |
797 | }); |
881 | }); |
798 | |
882 | |
799 | $quit->wait; |
883 | $quit->wait; |
800 | |
884 | |
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885 | |
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886 | =head1 BENCHMARK |
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887 | |
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888 | To give you an idea of the performance and overheads that AnyEvent adds |
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889 | over the event loops themselves (and to give you an impression of the |
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890 | speed of various event loops), here is a benchmark of various supported |
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891 | event models natively and with anyevent. The benchmark creates a lot of |
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892 | timers (with a zero timeout) and I/O watchers (watching STDOUT, a pty, to |
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893 | become writable, which it is), lets them fire exactly once and destroys |
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894 | them again. |
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895 | |
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896 | Rewriting the benchmark to use many different sockets instead of using |
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897 | the same filehandle for all I/O watchers results in a much longer runtime |
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898 | (socket creation is expensive), but qualitatively the same figures, so it |
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899 | was not used. |
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900 | |
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901 | =head2 Explanation of the columns |
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902 | |
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903 | I<watcher> is the number of event watchers created/destroyed. Since |
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904 | different event models feature vastly different performances, each event |
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905 | loop was given a number of watchers so that overall runtime is acceptable |
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906 | and similar between tested event loop (and keep them from crashing): Glib |
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907 | would probably take thousands of years if asked to process the same number |
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908 | of watchers as EV in this benchmark. |
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909 | |
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910 | I<bytes> is the number of bytes (as measured by the resident set size, |
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911 | RSS) consumed by each watcher. This method of measuring captures both C |
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912 | and Perl-based overheads. |
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913 | |
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914 | I<create> is the time, in microseconds (millionths of seconds), that it |
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915 | takes to create a single watcher. The callback is a closure shared between |
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916 | all watchers, to avoid adding memory overhead. That means closure creation |
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917 | and memory usage is not included in the figures. |
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918 | |
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919 | I<invoke> is the time, in microseconds, used to invoke a simple |
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920 | callback. The callback simply counts down a Perl variable and after it was |
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921 | invoked "watcher" times, it would C<< ->broadcast >> a condvar once to |
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922 | signal the end of this phase. |
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923 | |
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924 | I<destroy> is the time, in microseconds, that it takes to destroy a single |
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925 | watcher. |
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926 | |
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927 | =head2 Results |
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928 | |
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929 | name watchers bytes create invoke destroy comment |
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930 | EV/EV 400000 244 0.56 0.46 0.31 EV native interface |
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931 | EV/Any 100000 610 3.52 0.91 0.75 EV + AnyEvent watchers |
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932 | CoroEV/Any 100000 610 3.49 0.92 0.75 coroutines + Coro::Signal |
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933 | Perl/Any 100000 513 4.91 0.92 1.15 pure perl implementation |
|
|
934 | Event/Event 16000 523 28.05 21.38 0.86 Event native interface |
|
|
935 | Event/Any 16000 943 34.43 20.48 1.39 Event + AnyEvent watchers |
|
|
936 | Glib/Any 16000 1357 96.99 12.55 55.51 quadratic behaviour |
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|
937 | Tk/Any 2000 1855 27.01 66.61 14.03 SEGV with >> 2000 watchers |
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|
938 | POE/Event 2000 6644 108.15 768.19 14.33 via POE::Loop::Event |
|
|
939 | POE/Select 2000 6343 94.69 807.65 562.69 via POE::Loop::Select |
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|
940 | |
|
|
941 | =head2 Discussion |
|
|
942 | |
|
|
943 | The benchmark does I<not> measure scalability of the event loop very |
|
|
944 | well. For example, a select-based event loop (such as the pure perl one) |
|
|
945 | can never compete with an event loop that uses epoll when the number of |
|
|
946 | file descriptors grows high. In this benchmark, all events become ready at |
|
|
947 | the same time, so select/poll-based implementations get an unnatural speed |
|
|
948 | boost. |
|
|
949 | |
|
|
950 | C<EV> is the sole leader regarding speed and memory use, which are both |
|
|
951 | maximal/minimal, respectively. Even when going through AnyEvent, there are |
|
|
952 | only two event loops that use slightly less memory (the C<Event> module |
|
|
953 | natively and the pure perl backend), and no faster event models, not even |
|
|
954 | C<Event> natively. |
|
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955 | |
|
|
956 | The pure perl implementation is hit in a few sweet spots (both the |
|
|
957 | zero timeout and the use of a single fd hit optimisations in the perl |
|
|
958 | interpreter and the backend itself, and all watchers become ready at the |
|
|
959 | same time). Nevertheless this shows that it adds very little overhead in |
|
|
960 | itself. Like any select-based backend its performance becomes really bad |
|
|
961 | with lots of file descriptors (and few of them active), of course, but |
|
|
962 | this was not subject of this benchmark. |
|
|
963 | |
|
|
964 | The C<Event> module has a relatively high setup and callback invocation cost, |
|
|
965 | but overall scores on the third place. |
|
|
966 | |
|
|
967 | C<Glib>'s memory usage is quite a bit bit higher, but it features a |
|
|
968 | faster callback invocation and overall ends up in the same class as |
|
|
969 | C<Event>. However, Glib scales extremely badly, doubling the number of |
|
|
970 | watchers increases the processing time by more than a factor of four, |
|
|
971 | making it completely unusable when using larger numbers of watchers |
|
|
972 | (note that only a single file descriptor was used in the benchmark, so |
|
|
973 | inefficiencies of C<poll> do not account for this). |
|
|
974 | |
|
|
975 | The C<Tk> adaptor works relatively well. The fact that it crashes with |
|
|
976 | more than 2000 watchers is a big setback, however, as correctness takes |
|
|
977 | precedence over speed. Nevertheless, its performance is surprising, as the |
|
|
978 | file descriptor is dup()ed for each watcher. This shows that the dup() |
|
|
979 | employed by some adaptors is not a big performance issue (it does incur a |
|
|
980 | hidden memory cost inside the kernel, though, that is not reflected in the |
|
|
981 | figures above). |
|
|
982 | |
|
|
983 | C<POE>, regardless of underlying event loop (wether using its pure perl |
|
|
984 | select-based backend or the Event module) shows abysmal performance and |
|
|
985 | memory usage: Watchers use almost 30 times as much memory as EV watchers, |
|
|
986 | and 10 times as much memory as both Event or EV via AnyEvent. Watcher |
|
|
987 | invocation is almost 900 times slower than with AnyEvent's pure perl |
|
|
988 | implementation. The design of the POE adaptor class in AnyEvent can not |
|
|
989 | really account for this, as session creation overhead is small compared |
|
|
990 | to execution of the state machine, which is coded pretty optimally within |
|
|
991 | L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow. |
|
|
992 | |
|
|
993 | =head2 Summary |
|
|
994 | |
|
|
995 | Using EV through AnyEvent is faster than any other event loop, but most |
|
|
996 | event loops have acceptable performance with or without AnyEvent. |
|
|
997 | |
|
|
998 | The overhead AnyEvent adds is usually much smaller than the overhead of |
|
|
999 | the actual event loop, only with extremely fast event loops such as the EV |
|
|
1000 | adds AnyEvent significant overhead. |
|
|
1001 | |
|
|
1002 | And you should simply avoid POE like the plague if you want performance or |
|
|
1003 | reasonable memory usage. |
|
|
1004 | |
|
|
1005 | |
|
|
1006 | =head1 FORK |
|
|
1007 | |
|
|
1008 | Most event libraries are not fork-safe. The ones who are usually are |
|
|
1009 | because they are so inefficient. Only L<EV> is fully fork-aware. |
|
|
1010 | |
|
|
1011 | If you have to fork, you must either do so I<before> creating your first |
|
|
1012 | watcher OR you must not use AnyEvent at all in the child. |
|
|
1013 | |
|
|
1014 | |
|
|
1015 | =head1 SECURITY CONSIDERATIONS |
|
|
1016 | |
|
|
1017 | AnyEvent can be forced to load any event model via |
|
|
1018 | $ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to |
|
|
1019 | execute arbitrary code or directly gain access, it can easily be used to |
|
|
1020 | make the program hang or malfunction in subtle ways, as AnyEvent watchers |
|
|
1021 | will not be active when the program uses a different event model than |
|
|
1022 | specified in the variable. |
|
|
1023 | |
|
|
1024 | You can make AnyEvent completely ignore this variable by deleting it |
|
|
1025 | before the first watcher gets created, e.g. with a C<BEGIN> block: |
|
|
1026 | |
|
|
1027 | BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} } |
|
|
1028 | |
|
|
1029 | use AnyEvent; |
|
|
1030 | |
|
|
1031 | |
801 | =head1 SEE ALSO |
1032 | =head1 SEE ALSO |
802 | |
1033 | |
803 | Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>, |
1034 | Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>, |
804 | L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>. |
1035 | L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>, |
|
|
1036 | L<Event::Lib>, L<Qt>, L<POE>. |
805 | |
1037 | |
806 | Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>, |
1038 | Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>, |
|
|
1039 | L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>, |
|
|
1040 | L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>, |
807 | L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, |
1041 | L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>. |
808 | L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>. |
|
|
809 | |
1042 | |
810 | Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>. |
1043 | Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>. |
|
|
1044 | |
811 | |
1045 | |
812 | =head1 AUTHOR |
1046 | =head1 AUTHOR |
813 | |
1047 | |
814 | Marc Lehmann <schmorp@schmorp.de> |
1048 | Marc Lehmann <schmorp@schmorp.de> |
815 | http://home.schmorp.de/ |
1049 | http://home.schmorp.de/ |