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, Event::Lib, Qt - 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 | |
… | |
… | |
15 | my $w = AnyEvent->timer (after => $seconds, cb => sub { |
15 | my $w = AnyEvent->timer (after => $seconds, cb => sub { |
16 | ... |
16 | ... |
17 | }); |
17 | }); |
18 | |
18 | |
19 | my $w = AnyEvent->condvar; # stores whether a condition was flagged |
19 | my $w = AnyEvent->condvar; # stores whether a condition was flagged |
20 | $w->wait; # enters "main loop" till $condvar gets ->broadcast |
20 | $w->wait; # enters "main loop" till $condvar gets ->send |
21 | $w->broadcast; # wake up current and all future wait's |
21 | $w->send; # wake up current and all future wait's |
22 | |
22 | |
23 | =head1 WHY YOU SHOULD USE THIS MODULE (OR NOT) |
23 | =head1 WHY YOU SHOULD USE THIS MODULE (OR NOT) |
24 | |
24 | |
25 | Glib, POE, IO::Async, Event... CPAN offers event models by the dozen |
25 | Glib, POE, IO::Async, Event... CPAN offers event models by the dozen |
26 | nowadays. So what is different about AnyEvent? |
26 | nowadays. So what is different about AnyEvent? |
… | |
… | |
66 | |
66 | |
67 | Of course, if you want lots of policy (this can arguably be somewhat |
67 | Of course, if you want lots of policy (this can arguably be somewhat |
68 | useful) and you want to force your users to use the one and only event |
68 | useful) and you want to force your users to use the one and only event |
69 | model, you should I<not> use this module. |
69 | model, you should I<not> use this module. |
70 | |
70 | |
71 | |
|
|
72 | =head1 DESCRIPTION |
71 | =head1 DESCRIPTION |
73 | |
72 | |
74 | L<AnyEvent> provides an identical interface to multiple event loops. This |
73 | L<AnyEvent> provides an identical interface to multiple event loops. This |
75 | allows module authors to utilise an event loop without forcing module |
74 | allows module authors to utilise an event loop without forcing module |
76 | users to use the same event loop (as only a single event loop can coexist |
75 | users to use the same event loop (as only a single event loop can coexist |
… | |
… | |
80 | module. |
79 | module. |
81 | |
80 | |
82 | During the first call of any watcher-creation method, the module tries |
81 | 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 |
82 | 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>, |
83 | 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, |
84 | 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 |
85 | L<POE>. The first one found is used. If none are found, the module tries |
|
|
86 | to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl |
|
|
87 | 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 |
88 | 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 |
89 | found, AnyEvent will fall back to a pure-perl event loop, which is not |
89 | is not very efficient, but should work everywhere. |
90 | very efficient, but should work everywhere. |
90 | |
91 | |
91 | Because AnyEvent first checks for modules that are already loaded, loading |
92 | Because AnyEvent first checks for modules that are already loaded, loading |
92 | an event model explicitly before first using AnyEvent will likely make |
93 | an event model explicitly before first using AnyEvent will likely make |
93 | that model the default. For example: |
94 | that model the default. For example: |
94 | |
95 | |
… | |
… | |
134 | |
135 | |
135 | Note that C<my $w; $w => combination. This is necessary because in Perl, |
136 | 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 |
137 | my variables are only visible after the statement in which they are |
137 | declared. |
138 | declared. |
138 | |
139 | |
139 | =head2 IO WATCHERS |
140 | =head2 I/O WATCHERS |
140 | |
141 | |
141 | You can create an I/O watcher by calling the C<< AnyEvent->io >> method |
142 | You can create an I/O watcher by calling the C<< AnyEvent->io >> method |
142 | with the following mandatory key-value pairs as arguments: |
143 | with the following mandatory key-value pairs as arguments: |
143 | |
144 | |
144 | C<fh> the Perl I<file handle> (I<not> file descriptor) to watch for |
145 | C<fh> the Perl I<file handle> (I<not> file descriptor) to watch |
145 | events. C<poll> must be a string that is either C<r> or C<w>, which |
146 | for events. C<poll> must be a string that is either C<r> or C<w>, |
146 | creates a watcher waiting for "r"eadable or "w"ritable events, |
147 | which 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 |
148 | respectively. C<cb> is the callback to invoke each time the file handle |
148 | becomes ready. |
149 | becomes ready. |
149 | |
150 | |
150 | As long as the I/O watcher exists it will keep the file descriptor or a |
151 | Although the callback might get passed parameters, their value and |
151 | copy of it alive/open. |
152 | presence is undefined and you cannot rely on them. Portable AnyEvent |
|
|
153 | callbacks cannot use arguments passed to I/O watcher callbacks. |
152 | |
154 | |
|
|
155 | The I/O watcher might use the underlying file descriptor or a copy of it. |
153 | It is not allowed to close a file handle as long as any watcher is active |
156 | You must not close a file handle as long as any watcher is active on the |
154 | on the underlying file descriptor. |
157 | underlying file descriptor. |
155 | |
158 | |
156 | Some event loops issue spurious readyness notifications, so you should |
159 | Some event loops issue spurious readyness notifications, so you should |
157 | always use non-blocking calls when reading/writing from/to your file |
160 | always use non-blocking calls when reading/writing from/to your file |
158 | handles. |
161 | handles. |
159 | |
162 | |
… | |
… | |
170 | |
173 | |
171 | You can create a time watcher by calling the C<< AnyEvent->timer >> |
174 | You can create a time watcher by calling the C<< AnyEvent->timer >> |
172 | method with the following mandatory arguments: |
175 | method with the following mandatory arguments: |
173 | |
176 | |
174 | C<after> specifies after how many seconds (fractional values are |
177 | C<after> specifies after how many seconds (fractional values are |
175 | supported) should the timer activate. C<cb> the callback to invoke in that |
178 | supported) the callback should be invoked. C<cb> is the callback to invoke |
176 | case. |
179 | in that case. |
|
|
180 | |
|
|
181 | Although the callback might get passed parameters, their value and |
|
|
182 | presence is undefined and you cannot rely on them. Portable AnyEvent |
|
|
183 | callbacks cannot use arguments passed to time watcher callbacks. |
177 | |
184 | |
178 | The timer callback will be invoked at most once: if you want a repeating |
185 | The timer callback will be invoked at most once: if you want a repeating |
179 | timer you have to create a new watcher (this is a limitation by both Tk |
186 | timer you have to create a new watcher (this is a limitation by both Tk |
180 | and Glib). |
187 | and Glib). |
181 | |
188 | |
… | |
… | |
206 | |
213 | |
207 | There are two ways to handle timers: based on real time (relative, "fire |
214 | 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 |
215 | in 10 seconds") and based on wallclock time (absolute, "fire at 12 |
209 | o'clock"). |
216 | o'clock"). |
210 | |
217 | |
211 | While most event loops expect timers to specified in a relative way, they use |
218 | 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", |
219 | 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 |
220 | "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 |
221 | the wrong date of 2014-01-01 to 2008-01-01, a watcher that is supposed to |
215 | six years to finally fire. |
222 | fire "after" a second might actually take six years to finally fire. |
216 | |
223 | |
217 | AnyEvent cannot compensate for this. The only event loop that is conscious |
224 | 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 |
225 | about these issues is L<EV>, which offers both relative (ev_timer, based |
219 | absolute (ev_periodic) timers. |
226 | on true relative time) and absolute (ev_periodic, based on wallclock time) |
|
|
227 | timers. |
220 | |
228 | |
221 | AnyEvent always prefers relative timers, if available, matching the |
229 | AnyEvent always prefers relative timers, if available, matching the |
222 | AnyEvent API. |
230 | AnyEvent API. |
223 | |
231 | |
224 | =head2 SIGNAL WATCHERS |
232 | =head2 SIGNAL WATCHERS |
225 | |
233 | |
226 | You can watch for signals using a signal watcher, C<signal> is the signal |
234 | You can watch for signals using a signal watcher, C<signal> is the signal |
227 | I<name> without any C<SIG> prefix, C<cb> is the Perl callback to |
235 | I<name> without any C<SIG> prefix, C<cb> is the Perl callback to |
228 | be invoked whenever a signal occurs. |
236 | be invoked whenever a signal occurs. |
229 | |
237 | |
|
|
238 | Although the callback might get passed parameters, their value and |
|
|
239 | presence is undefined and you cannot rely on them. Portable AnyEvent |
|
|
240 | callbacks cannot use arguments passed to signal watcher callbacks. |
|
|
241 | |
230 | Multiple signals occurances can be clumped together into one callback |
242 | Multiple signal occurances can be clumped together into one callback |
231 | invocation, and callback invocation will be synchronous. synchronous means |
243 | invocation, and callback invocation will be synchronous. synchronous means |
232 | that it might take a while until the signal gets handled by the process, |
244 | that it might take a while until the signal gets handled by the process, |
233 | but it is guarenteed not to interrupt any other callbacks. |
245 | but it is guarenteed not to interrupt any other callbacks. |
234 | |
246 | |
235 | The main advantage of using these watchers is that you can share a signal |
247 | The main advantage of using these watchers is that you can share a signal |
… | |
… | |
248 | |
260 | |
249 | The child process is specified by the C<pid> argument (if set to C<0>, it |
261 | The child process is specified by the C<pid> argument (if set to C<0>, it |
250 | watches for any child process exit). The watcher will trigger as often |
262 | watches for any child process exit). The watcher will trigger as often |
251 | as status change for the child are received. This works by installing a |
263 | as status change for the child are received. This works by installing a |
252 | signal handler for C<SIGCHLD>. The callback will be called with the pid |
264 | signal handler for C<SIGCHLD>. The callback will be called with the pid |
253 | and exit status (as returned by waitpid). |
265 | and exit status (as returned by waitpid), so unlike other watcher types, |
|
|
266 | you I<can> rely on child watcher callback arguments. |
254 | |
267 | |
255 | Example: wait for pid 1333 |
268 | There is a slight catch to child watchers, however: you usually start them |
|
|
269 | I<after> the child process was created, and this means the process could |
|
|
270 | have exited already (and no SIGCHLD will be sent anymore). |
|
|
271 | |
|
|
272 | Not all event models handle this correctly (POE doesn't), but even for |
|
|
273 | event models that I<do> handle this correctly, they usually need to be |
|
|
274 | loaded before the process exits (i.e. before you fork in the first place). |
|
|
275 | |
|
|
276 | This means you cannot create a child watcher as the very first thing in an |
|
|
277 | AnyEvent program, you I<have> to create at least one watcher before you |
|
|
278 | C<fork> the child (alternatively, you can call C<AnyEvent::detect>). |
|
|
279 | |
|
|
280 | Example: fork a process and wait for it |
|
|
281 | |
|
|
282 | my $done = AnyEvent->condvar; |
|
|
283 | |
|
|
284 | AnyEvent::detect; # force event module to be initialised |
|
|
285 | |
|
|
286 | my $pid = fork or exit 5; |
256 | |
287 | |
257 | my $w = AnyEvent->child ( |
288 | my $w = AnyEvent->child ( |
258 | pid => 1333, |
289 | pid => $pid, |
259 | cb => sub { |
290 | cb => sub { |
260 | my ($pid, $status) = @_; |
291 | my ($pid, $status) = @_; |
261 | warn "pid $pid exited with status $status"; |
292 | warn "pid $pid exited with status $status"; |
|
|
293 | $done->send; |
262 | }, |
294 | }, |
263 | ); |
295 | ); |
264 | |
296 | |
|
|
297 | # do something else, then wait for process exit |
|
|
298 | $done->wait; |
|
|
299 | |
265 | =head2 CONDITION VARIABLES |
300 | =head2 CONDITION VARIABLES |
266 | |
301 | |
|
|
302 | If you are familiar with some event loops you will know that all of them |
|
|
303 | require you to run some blocking "loop", "run" or similar function that |
|
|
304 | will actively watch for new events and call your callbacks. |
|
|
305 | |
|
|
306 | AnyEvent is different, it expects somebody else to run the event loop and |
|
|
307 | will only block when necessary (usually when told by the user). |
|
|
308 | |
|
|
309 | The instrument to do that is called a "condition variable", so called |
|
|
310 | because they represent a condition that must become true. |
|
|
311 | |
267 | Condition variables can be created by calling the C<< AnyEvent->condvar >> |
312 | Condition variables can be created by calling the C<< AnyEvent->condvar |
268 | method without any arguments. |
313 | >> method, usually without arguments. The only argument pair allowed is |
|
|
314 | C<cb>, which specifies a callback to be called when the condition variable |
|
|
315 | becomes true. |
269 | |
316 | |
270 | A condition variable waits for a condition - precisely that the C<< |
317 | After creation, the conditon variable is "false" until it becomes "true" |
271 | ->broadcast >> method has been called. |
318 | by calling the C<send> method. |
272 | |
319 | |
273 | They are very useful to signal that a condition has been fulfilled, for |
320 | Condition variables are similar to callbacks, except that you can |
|
|
321 | optionally wait for them. They can also be called merge points - points |
|
|
322 | in time where multiple outstandign events have been processed. And yet |
|
|
323 | another way to call them is transations - each condition variable can be |
|
|
324 | used to represent a transaction, which finishes at some point and delivers |
|
|
325 | a result. |
|
|
326 | |
|
|
327 | Condition variables are very useful to signal that something has finished, |
274 | example, if you write a module that does asynchronous http requests, |
328 | for example, if you write a module that does asynchronous http requests, |
275 | then a condition variable would be the ideal candidate to signal the |
329 | then a condition variable would be the ideal candidate to signal the |
276 | availability of results. |
330 | availability of results. The user can either act when the callback is |
|
|
331 | called or can synchronously C<< ->wait >> for the results. |
277 | |
332 | |
278 | You can also use condition variables to block your main program until |
333 | You can also use them to simulate traditional event loops - for example, |
279 | an event occurs - for example, you could C<< ->wait >> in your main |
334 | you can block your main program until an event occurs - for example, you |
280 | program until the user clicks the Quit button in your app, which would C<< |
335 | could C<< ->wait >> in your main program until the user clicks the Quit |
281 | ->broadcast >> the "quit" event. |
336 | button of your app, which would C<< ->send >> the "quit" event. |
282 | |
337 | |
283 | Note that condition variables recurse into the event loop - if you have |
338 | Note that condition variables recurse into the event loop - if you have |
284 | two pirces of code that call C<< ->wait >> in a round-robbin fashion, you |
339 | two pieces of code that call C<< ->wait >> in a round-robbin fashion, you |
285 | lose. Therefore, condition variables are good to export to your caller, but |
340 | lose. Therefore, condition variables are good to export to your caller, but |
286 | you should avoid making a blocking wait yourself, at least in callbacks, |
341 | you should avoid making a blocking wait yourself, at least in callbacks, |
287 | as this asks for trouble. |
342 | as this asks for trouble. |
288 | |
343 | |
289 | This object has two methods: |
344 | Condition variables are represented by hash refs in perl, and the keys |
|
|
345 | used by AnyEvent itself are all named C<_ae_XXX> to make subclassing |
|
|
346 | easy (it is often useful to build your own transaction class on top of |
|
|
347 | AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call |
|
|
348 | it's C<new> method in your own C<new> method. |
|
|
349 | |
|
|
350 | There are two "sides" to a condition variable - the "producer side" which |
|
|
351 | eventually calls C<< -> send >>, and the "consumer side", which waits |
|
|
352 | for the send to occur. |
|
|
353 | |
|
|
354 | Example: |
|
|
355 | |
|
|
356 | # wait till the result is ready |
|
|
357 | my $result_ready = AnyEvent->condvar; |
|
|
358 | |
|
|
359 | # do something such as adding a timer |
|
|
360 | # or socket watcher the calls $result_ready->send |
|
|
361 | # when the "result" is ready. |
|
|
362 | # in this case, we simply use a timer: |
|
|
363 | my $w = AnyEvent->timer ( |
|
|
364 | after => 1, |
|
|
365 | cb => sub { $result_ready->send }, |
|
|
366 | ); |
|
|
367 | |
|
|
368 | # this "blocks" (while handling events) till the callback |
|
|
369 | # calls send |
|
|
370 | $result_ready->wait; |
|
|
371 | |
|
|
372 | =head3 METHODS FOR PRODUCERS |
|
|
373 | |
|
|
374 | These methods should only be used by the producing side, i.e. the |
|
|
375 | code/module that eventually sends the signal. Note that it is also |
|
|
376 | the producer side which creates the condvar in most cases, but it isn't |
|
|
377 | uncommon for the consumer to create it as well. |
290 | |
378 | |
291 | =over 4 |
379 | =over 4 |
292 | |
380 | |
|
|
381 | =item $cv->send (...) |
|
|
382 | |
|
|
383 | Flag the condition as ready - a running C<< ->wait >> and all further |
|
|
384 | calls to C<wait> will (eventually) return after this method has been |
|
|
385 | called. If nobody is waiting the send will be remembered. |
|
|
386 | |
|
|
387 | If a callback has been set on the condition variable, it is called |
|
|
388 | immediately from within send. |
|
|
389 | |
|
|
390 | Any arguments passed to the C<send> call will be returned by all |
|
|
391 | future C<< ->wait >> calls. |
|
|
392 | |
|
|
393 | =item $cv->croak ($error) |
|
|
394 | |
|
|
395 | Similar to send, but causes all call's wait C<< ->wait >> to invoke |
|
|
396 | C<Carp::croak> with the given error message/object/scalar. |
|
|
397 | |
|
|
398 | This can be used to signal any errors to the condition variable |
|
|
399 | user/consumer. |
|
|
400 | |
|
|
401 | =item $cv->begin ([group callback]) |
|
|
402 | |
|
|
403 | =item $cv->end |
|
|
404 | |
|
|
405 | These two methods can be used to combine many transactions/events into |
|
|
406 | one. For example, a function that pings many hosts in parallel might want |
|
|
407 | to use a condition variable for the whole process. |
|
|
408 | |
|
|
409 | Every call to C<< ->begin >> will increment a counter, and every call to |
|
|
410 | C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end |
|
|
411 | >>, the (last) callback passed to C<begin> will be executed. That callback |
|
|
412 | is I<supposed> to call C<< ->send >>, but that is not required. If no |
|
|
413 | callback was set, C<send> will be called without any arguments. |
|
|
414 | |
|
|
415 | Let's clarify this with the ping example: |
|
|
416 | |
|
|
417 | my $cv = AnyEvent->condvar; |
|
|
418 | |
|
|
419 | my %result; |
|
|
420 | $cv->begin (sub { $cv->send (\%result) }); |
|
|
421 | |
|
|
422 | for my $host (@list_of_hosts) { |
|
|
423 | $cv->begin; |
|
|
424 | ping_host_then_call_callback $host, sub { |
|
|
425 | $result{$host} = ...; |
|
|
426 | $cv->end; |
|
|
427 | }; |
|
|
428 | } |
|
|
429 | |
|
|
430 | $cv->end; |
|
|
431 | |
|
|
432 | This code fragment supposedly pings a number of hosts and calls |
|
|
433 | C<send> after results for all then have have been gathered - in any |
|
|
434 | order. To achieve this, the code issues a call to C<begin> when it starts |
|
|
435 | each ping request and calls C<end> when it has received some result for |
|
|
436 | it. Since C<begin> and C<end> only maintain a counter, the order in which |
|
|
437 | results arrive is not relevant. |
|
|
438 | |
|
|
439 | There is an additional bracketing call to C<begin> and C<end> outside the |
|
|
440 | loop, which serves two important purposes: first, it sets the callback |
|
|
441 | to be called once the counter reaches C<0>, and second, it ensures that |
|
|
442 | C<send> is called even when C<no> hosts are being pinged (the loop |
|
|
443 | doesn't execute once). |
|
|
444 | |
|
|
445 | This is the general pattern when you "fan out" into multiple subrequests: |
|
|
446 | use an outer C<begin>/C<end> pair to set the callback and ensure C<end> |
|
|
447 | is called at least once, and then, for each subrequest you start, call |
|
|
448 | C<begin> and for eahc subrequest you finish, call C<end>. |
|
|
449 | |
|
|
450 | =back |
|
|
451 | |
|
|
452 | =head3 METHODS FOR CONSUMERS |
|
|
453 | |
|
|
454 | These methods should only be used by the consuming side, i.e. the |
|
|
455 | code awaits the condition. |
|
|
456 | |
|
|
457 | =over 4 |
|
|
458 | |
293 | =item $cv->wait |
459 | =item $cv->wait |
294 | |
460 | |
295 | Wait (blocking if necessary) until the C<< ->broadcast >> method has been |
461 | Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak |
296 | called on c<$cv>, while servicing other watchers normally. |
462 | >> methods have been called on c<$cv>, while servicing other watchers |
|
|
463 | normally. |
297 | |
464 | |
298 | You can only wait once on a condition - additional calls will return |
465 | You can only wait once on a condition - additional calls are valid but |
299 | immediately. |
466 | will return immediately. |
|
|
467 | |
|
|
468 | If an error condition has been set by calling C<< ->croak >>, then this |
|
|
469 | function will call C<croak>. |
|
|
470 | |
|
|
471 | In list context, all parameters passed to C<send> will be returned, |
|
|
472 | in scalar context only the first one will be returned. |
300 | |
473 | |
301 | Not all event models support a blocking wait - some die in that case |
474 | Not all event models support a blocking wait - some die in that case |
302 | (programs might want to do that to stay interactive), so I<if you are |
475 | (programs might want to do that to stay interactive), so I<if you are |
303 | using this from a module, never require a blocking wait>, but let the |
476 | using this from a module, never require a blocking wait>, but let the |
304 | caller decide whether the call will block or not (for example, by coupling |
477 | caller decide whether the call will block or not (for example, by coupling |
… | |
… | |
311 | multiple interpreters or coroutines/threads, none of which C<AnyEvent> |
484 | multiple interpreters or coroutines/threads, none of which C<AnyEvent> |
312 | can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and |
485 | can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and |
313 | L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s |
486 | L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s |
314 | from different coroutines, however). |
487 | from different coroutines, however). |
315 | |
488 | |
316 | =item $cv->broadcast |
489 | You can ensure that C<< -wait >> never blocks by setting a callback and |
|
|
490 | only calling C<< ->wait >> from within that callback (or at a later |
|
|
491 | time). This will work even when the event loop does not support blocking |
|
|
492 | waits otherwise. |
317 | |
493 | |
318 | Flag the condition as ready - a running C<< ->wait >> and all further |
494 | =item $bool = $cv->ready |
319 | calls to C<wait> will (eventually) return after this method has been |
495 | |
320 | called. If nobody is waiting the broadcast will be remembered.. |
496 | Returns true when the condition is "true", i.e. whether C<send> or |
|
|
497 | C<croak> have been called. |
|
|
498 | |
|
|
499 | =item $cb = $cv->cb ([new callback]) |
|
|
500 | |
|
|
501 | This is a mutator function that returns the callback set and optionally |
|
|
502 | replaces it before doing so. |
|
|
503 | |
|
|
504 | The callback will be called when the condition becomes "true", i.e. when |
|
|
505 | C<send> or C<croak> are called. Calling C<wait> inside the callback |
|
|
506 | or at any later time is guaranteed not to block. |
321 | |
507 | |
322 | =back |
508 | =back |
323 | |
|
|
324 | Example: |
|
|
325 | |
|
|
326 | # wait till the result is ready |
|
|
327 | my $result_ready = AnyEvent->condvar; |
|
|
328 | |
|
|
329 | # do something such as adding a timer |
|
|
330 | # or socket watcher the calls $result_ready->broadcast |
|
|
331 | # when the "result" is ready. |
|
|
332 | # in this case, we simply use a timer: |
|
|
333 | my $w = AnyEvent->timer ( |
|
|
334 | after => 1, |
|
|
335 | cb => sub { $result_ready->broadcast }, |
|
|
336 | ); |
|
|
337 | |
|
|
338 | # this "blocks" (while handling events) till the watcher |
|
|
339 | # calls broadcast |
|
|
340 | $result_ready->wait; |
|
|
341 | |
509 | |
342 | =head1 GLOBAL VARIABLES AND FUNCTIONS |
510 | =head1 GLOBAL VARIABLES AND FUNCTIONS |
343 | |
511 | |
344 | =over 4 |
512 | =over 4 |
345 | |
513 | |
… | |
… | |
355 | |
523 | |
356 | AnyEvent::Impl::CoroEV based on Coro::EV, best choice. |
524 | AnyEvent::Impl::CoroEV based on Coro::EV, best choice. |
357 | AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice. |
525 | AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice. |
358 | AnyEvent::Impl::EV based on EV (an interface to libev, best choice). |
526 | AnyEvent::Impl::EV based on EV (an interface to libev, best choice). |
359 | AnyEvent::Impl::Event based on Event, second best choice. |
527 | AnyEvent::Impl::Event based on Event, second best choice. |
|
|
528 | AnyEvent::Impl::Perl pure-perl implementation, fast and portable. |
360 | AnyEvent::Impl::Glib based on Glib, third-best choice. |
529 | AnyEvent::Impl::Glib based on Glib, third-best choice. |
361 | AnyEvent::Impl::Tk based on Tk, very bad choice. |
530 | AnyEvent::Impl::Tk based on Tk, very bad choice. |
362 | AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable. |
|
|
363 | AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs). |
531 | AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs). |
364 | AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse. |
532 | AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse. |
|
|
533 | AnyEvent::Impl::POE based on POE, not generic enough for full support. |
|
|
534 | |
|
|
535 | There is no support for WxWidgets, as WxWidgets has no support for |
|
|
536 | watching file handles. However, you can use WxWidgets through the |
|
|
537 | POE Adaptor, as POE has a Wx backend that simply polls 20 times per |
|
|
538 | second, which was considered to be too horrible to even consider for |
|
|
539 | AnyEvent. Likewise, other POE backends can be used by AnyEvent by using |
|
|
540 | it's adaptor. |
|
|
541 | |
|
|
542 | AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when |
|
|
543 | autodetecting them. |
365 | |
544 | |
366 | =item AnyEvent::detect |
545 | =item AnyEvent::detect |
367 | |
546 | |
368 | Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model |
547 | Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model |
369 | if necessary. You should only call this function right before you would |
548 | if necessary. You should only call this function right before you would |
… | |
… | |
381 | decide which event module to use as soon as the first method is called, so |
560 | decide which event module to use as soon as the first method is called, so |
382 | by calling AnyEvent in your module body you force the user of your module |
561 | by calling AnyEvent in your module body you force the user of your module |
383 | to load the event module first. |
562 | to load the event module first. |
384 | |
563 | |
385 | Never call C<< ->wait >> on a condition variable unless you I<know> that |
564 | Never call C<< ->wait >> on a condition variable unless you I<know> that |
386 | the C<< ->broadcast >> method has been called on it already. This is |
565 | the C<< ->send >> method has been called on it already. This is |
387 | because it will stall the whole program, and the whole point of using |
566 | because it will stall the whole program, and the whole point of using |
388 | events is to stay interactive. |
567 | events is to stay interactive. |
389 | |
568 | |
390 | It is fine, however, to call C<< ->wait >> when the user of your module |
569 | It is fine, however, to call C<< ->wait >> when the user of your module |
391 | requests it (i.e. if you create a http request object ad have a method |
570 | requests it (i.e. if you create a http request object ad have a method |
… | |
… | |
411 | |
590 | |
412 | You can chose to use a rather inefficient pure-perl implementation by |
591 | You can chose to use a rather inefficient pure-perl implementation by |
413 | loading the C<AnyEvent::Impl::Perl> module, which gives you similar |
592 | loading the C<AnyEvent::Impl::Perl> module, which gives you similar |
414 | behaviour everywhere, but letting AnyEvent chose is generally better. |
593 | behaviour everywhere, but letting AnyEvent chose is generally better. |
415 | |
594 | |
|
|
595 | =head1 OTHER MODULES |
|
|
596 | |
|
|
597 | The following is a non-exhaustive list of additional modules that use |
|
|
598 | AnyEvent and can therefore be mixed easily with other AnyEvent modules |
|
|
599 | in the same program. Some of the modules come with AnyEvent, some are |
|
|
600 | available via CPAN. |
|
|
601 | |
|
|
602 | =over 4 |
|
|
603 | |
|
|
604 | =item L<AnyEvent::Util> |
|
|
605 | |
|
|
606 | Contains various utility functions that replace often-used but blocking |
|
|
607 | functions such as C<inet_aton> by event-/callback-based versions. |
|
|
608 | |
|
|
609 | =item L<AnyEvent::Handle> |
|
|
610 | |
|
|
611 | Provide read and write buffers and manages watchers for reads and writes. |
|
|
612 | |
|
|
613 | =item L<AnyEvent::Socket> |
|
|
614 | |
|
|
615 | Provides a means to do non-blocking connects, accepts etc. |
|
|
616 | |
|
|
617 | =item L<AnyEvent::HTTPD> |
|
|
618 | |
|
|
619 | Provides a simple web application server framework. |
|
|
620 | |
|
|
621 | =item L<AnyEvent::DNS> |
|
|
622 | |
|
|
623 | Provides asynchronous DNS resolver capabilities, beyond what |
|
|
624 | L<AnyEvent::Util> offers. |
|
|
625 | |
|
|
626 | =item L<AnyEvent::FastPing> |
|
|
627 | |
|
|
628 | The fastest ping in the west. |
|
|
629 | |
|
|
630 | =item L<Net::IRC3> |
|
|
631 | |
|
|
632 | AnyEvent based IRC client module family. |
|
|
633 | |
|
|
634 | =item L<Net::XMPP2> |
|
|
635 | |
|
|
636 | AnyEvent based XMPP (Jabber protocol) module family. |
|
|
637 | |
|
|
638 | =item L<Net::FCP> |
|
|
639 | |
|
|
640 | AnyEvent-based implementation of the Freenet Client Protocol, birthplace |
|
|
641 | of AnyEvent. |
|
|
642 | |
|
|
643 | =item L<Event::ExecFlow> |
|
|
644 | |
|
|
645 | High level API for event-based execution flow control. |
|
|
646 | |
|
|
647 | =item L<Coro> |
|
|
648 | |
|
|
649 | Has special support for AnyEvent. |
|
|
650 | |
|
|
651 | =item L<IO::Lambda> |
|
|
652 | |
|
|
653 | The lambda approach to I/O - don't ask, look there. Can use AnyEvent. |
|
|
654 | |
|
|
655 | =item L<IO::AIO> |
|
|
656 | |
|
|
657 | Truly asynchronous I/O, should be in the toolbox of every event |
|
|
658 | programmer. Can be trivially made to use AnyEvent. |
|
|
659 | |
|
|
660 | =item L<BDB> |
|
|
661 | |
|
|
662 | Truly asynchronous Berkeley DB access. Can be trivially made to use |
|
|
663 | AnyEvent. |
|
|
664 | |
|
|
665 | =back |
|
|
666 | |
416 | =cut |
667 | =cut |
417 | |
668 | |
418 | package AnyEvent; |
669 | package AnyEvent; |
419 | |
670 | |
420 | no warnings; |
671 | no warnings; |
421 | use strict; |
672 | use strict; |
422 | |
673 | |
423 | use Carp; |
674 | use Carp; |
424 | |
675 | |
425 | our $VERSION = '3.12'; |
676 | our $VERSION = '3.3'; |
426 | our $MODEL; |
677 | our $MODEL; |
427 | |
678 | |
428 | our $AUTOLOAD; |
679 | our $AUTOLOAD; |
429 | our @ISA; |
680 | our @ISA; |
430 | |
681 | |
… | |
… | |
435 | my @models = ( |
686 | my @models = ( |
436 | [Coro::EV:: => AnyEvent::Impl::CoroEV::], |
687 | [Coro::EV:: => AnyEvent::Impl::CoroEV::], |
437 | [Coro::Event:: => AnyEvent::Impl::CoroEvent::], |
688 | [Coro::Event:: => AnyEvent::Impl::CoroEvent::], |
438 | [EV:: => AnyEvent::Impl::EV::], |
689 | [EV:: => AnyEvent::Impl::EV::], |
439 | [Event:: => AnyEvent::Impl::Event::], |
690 | [Event:: => AnyEvent::Impl::Event::], |
|
|
691 | [Tk:: => AnyEvent::Impl::Tk::], |
|
|
692 | [Wx:: => AnyEvent::Impl::POE::], |
|
|
693 | [Prima:: => AnyEvent::Impl::POE::], |
|
|
694 | [AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::], |
|
|
695 | # everything below here will not be autoprobed as the pureperl backend should work everywhere |
440 | [Glib:: => AnyEvent::Impl::Glib::], |
696 | [Glib:: => AnyEvent::Impl::Glib::], |
441 | [Tk:: => AnyEvent::Impl::Tk::], |
697 | [Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy |
442 | [AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::], |
698 | [Qt:: => AnyEvent::Impl::Qt::], # requires special main program |
|
|
699 | [POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza |
443 | ); |
700 | ); |
444 | my @models_detect = ( |
|
|
445 | [Qt:: => AnyEvent::Impl::Qt::], # requires special main program |
|
|
446 | [Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy |
|
|
447 | ); |
|
|
448 | |
701 | |
449 | our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY); |
702 | our %method = map +($_ => 1), qw(io timer signal child condvar one_event DESTROY); |
450 | |
703 | |
451 | sub detect() { |
704 | sub detect() { |
452 | unless ($MODEL) { |
705 | unless ($MODEL) { |
453 | no strict 'refs'; |
706 | no strict 'refs'; |
454 | |
707 | |
455 | if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) { |
708 | if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) { |
456 | my $model = "AnyEvent::Impl::$1"; |
709 | my $model = "AnyEvent::Impl::$1"; |
457 | if (eval "require $model") { |
710 | if (eval "require $model") { |
458 | $MODEL = $model; |
711 | $MODEL = $model; |
459 | warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1; |
712 | warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1; |
|
|
713 | } else { |
|
|
714 | warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose; |
460 | } |
715 | } |
461 | } |
716 | } |
462 | |
717 | |
463 | # check for already loaded models |
718 | # check for already loaded models |
464 | unless ($MODEL) { |
719 | unless ($MODEL) { |
465 | for (@REGISTRY, @models, @models_detect) { |
720 | for (@REGISTRY, @models) { |
466 | my ($package, $model) = @$_; |
721 | my ($package, $model) = @$_; |
467 | if (${"$package\::VERSION"} > 0) { |
722 | if (${"$package\::VERSION"} > 0) { |
468 | if (eval "require $model") { |
723 | if (eval "require $model") { |
469 | $MODEL = $model; |
724 | $MODEL = $model; |
470 | warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1; |
725 | warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1; |
… | |
… | |
657 | |
912 | |
658 | =over 4 |
913 | =over 4 |
659 | |
914 | |
660 | =item C<PERL_ANYEVENT_VERBOSE> |
915 | =item C<PERL_ANYEVENT_VERBOSE> |
661 | |
916 | |
|
|
917 | By default, AnyEvent will be completely silent except in fatal |
|
|
918 | conditions. You can set this environment variable to make AnyEvent more |
|
|
919 | talkative. |
|
|
920 | |
|
|
921 | When set to C<1> or higher, causes AnyEvent to warn about unexpected |
|
|
922 | conditions, such as not being able to load the event model specified by |
|
|
923 | C<PERL_ANYEVENT_MODEL>. |
|
|
924 | |
662 | When set to C<2> or higher, cause AnyEvent to report to STDERR which event |
925 | When set to C<2> or higher, cause AnyEvent to report to STDERR which event |
663 | model it chooses. |
926 | model it chooses. |
664 | |
927 | |
665 | =item C<PERL_ANYEVENT_MODEL> |
928 | =item C<PERL_ANYEVENT_MODEL> |
666 | |
929 | |
… | |
… | |
680 | |
943 | |
681 | =back |
944 | =back |
682 | |
945 | |
683 | =head1 EXAMPLE PROGRAM |
946 | =head1 EXAMPLE PROGRAM |
684 | |
947 | |
685 | The following program uses an IO watcher to read data from STDIN, a timer |
948 | The following program uses an I/O watcher to read data from STDIN, a timer |
686 | to display a message once per second, and a condition variable to quit the |
949 | to display a message once per second, and a condition variable to quit the |
687 | program when the user enters quit: |
950 | program when the user enters quit: |
688 | |
951 | |
689 | use AnyEvent; |
952 | use AnyEvent; |
690 | |
953 | |
… | |
… | |
834 | $quit->broadcast; |
1097 | $quit->broadcast; |
835 | }); |
1098 | }); |
836 | |
1099 | |
837 | $quit->wait; |
1100 | $quit->wait; |
838 | |
1101 | |
|
|
1102 | |
|
|
1103 | =head1 BENCHMARKS |
|
|
1104 | |
|
|
1105 | To give you an idea of the performance and overheads that AnyEvent adds |
|
|
1106 | over the event loops themselves and to give you an impression of the speed |
|
|
1107 | of various event loops I prepared some benchmarks. |
|
|
1108 | |
|
|
1109 | =head2 BENCHMARKING ANYEVENT OVERHEAD |
|
|
1110 | |
|
|
1111 | Here is a benchmark of various supported event models used natively and |
|
|
1112 | through anyevent. The benchmark creates a lot of timers (with a zero |
|
|
1113 | timeout) and I/O watchers (watching STDOUT, a pty, to become writable, |
|
|
1114 | which it is), lets them fire exactly once and destroys them again. |
|
|
1115 | |
|
|
1116 | Source code for this benchmark is found as F<eg/bench> in the AnyEvent |
|
|
1117 | distribution. |
|
|
1118 | |
|
|
1119 | =head3 Explanation of the columns |
|
|
1120 | |
|
|
1121 | I<watcher> is the number of event watchers created/destroyed. Since |
|
|
1122 | different event models feature vastly different performances, each event |
|
|
1123 | loop was given a number of watchers so that overall runtime is acceptable |
|
|
1124 | and similar between tested event loop (and keep them from crashing): Glib |
|
|
1125 | would probably take thousands of years if asked to process the same number |
|
|
1126 | of watchers as EV in this benchmark. |
|
|
1127 | |
|
|
1128 | I<bytes> is the number of bytes (as measured by the resident set size, |
|
|
1129 | RSS) consumed by each watcher. This method of measuring captures both C |
|
|
1130 | and Perl-based overheads. |
|
|
1131 | |
|
|
1132 | I<create> is the time, in microseconds (millionths of seconds), that it |
|
|
1133 | takes to create a single watcher. The callback is a closure shared between |
|
|
1134 | all watchers, to avoid adding memory overhead. That means closure creation |
|
|
1135 | and memory usage is not included in the figures. |
|
|
1136 | |
|
|
1137 | I<invoke> is the time, in microseconds, used to invoke a simple |
|
|
1138 | callback. The callback simply counts down a Perl variable and after it was |
|
|
1139 | invoked "watcher" times, it would C<< ->broadcast >> a condvar once to |
|
|
1140 | signal the end of this phase. |
|
|
1141 | |
|
|
1142 | I<destroy> is the time, in microseconds, that it takes to destroy a single |
|
|
1143 | watcher. |
|
|
1144 | |
|
|
1145 | =head3 Results |
|
|
1146 | |
|
|
1147 | name watchers bytes create invoke destroy comment |
|
|
1148 | EV/EV 400000 244 0.56 0.46 0.31 EV native interface |
|
|
1149 | EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers |
|
|
1150 | CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal |
|
|
1151 | Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation |
|
|
1152 | Event/Event 16000 516 31.88 31.30 0.85 Event native interface |
|
|
1153 | Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers |
|
|
1154 | Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour |
|
|
1155 | Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers |
|
|
1156 | POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event |
|
|
1157 | POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select |
|
|
1158 | |
|
|
1159 | =head3 Discussion |
|
|
1160 | |
|
|
1161 | The benchmark does I<not> measure scalability of the event loop very |
|
|
1162 | well. For example, a select-based event loop (such as the pure perl one) |
|
|
1163 | can never compete with an event loop that uses epoll when the number of |
|
|
1164 | file descriptors grows high. In this benchmark, all events become ready at |
|
|
1165 | the same time, so select/poll-based implementations get an unnatural speed |
|
|
1166 | boost. |
|
|
1167 | |
|
|
1168 | Also, note that the number of watchers usually has a nonlinear effect on |
|
|
1169 | overall speed, that is, creating twice as many watchers doesn't take twice |
|
|
1170 | the time - usually it takes longer. This puts event loops tested with a |
|
|
1171 | higher number of watchers at a disadvantage. |
|
|
1172 | |
|
|
1173 | To put the range of results into perspective, consider that on the |
|
|
1174 | benchmark machine, handling an event takes roughly 1600 CPU cycles with |
|
|
1175 | EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU |
|
|
1176 | cycles with POE. |
|
|
1177 | |
|
|
1178 | C<EV> is the sole leader regarding speed and memory use, which are both |
|
|
1179 | maximal/minimal, respectively. Even when going through AnyEvent, it uses |
|
|
1180 | far less memory than any other event loop and is still faster than Event |
|
|
1181 | natively. |
|
|
1182 | |
|
|
1183 | The pure perl implementation is hit in a few sweet spots (both the |
|
|
1184 | constant timeout and the use of a single fd hit optimisations in the perl |
|
|
1185 | interpreter and the backend itself). Nevertheless this shows that it |
|
|
1186 | adds very little overhead in itself. Like any select-based backend its |
|
|
1187 | performance becomes really bad with lots of file descriptors (and few of |
|
|
1188 | them active), of course, but this was not subject of this benchmark. |
|
|
1189 | |
|
|
1190 | The C<Event> module has a relatively high setup and callback invocation |
|
|
1191 | cost, but overall scores in on the third place. |
|
|
1192 | |
|
|
1193 | C<Glib>'s memory usage is quite a bit higher, but it features a |
|
|
1194 | faster callback invocation and overall ends up in the same class as |
|
|
1195 | C<Event>. However, Glib scales extremely badly, doubling the number of |
|
|
1196 | watchers increases the processing time by more than a factor of four, |
|
|
1197 | making it completely unusable when using larger numbers of watchers |
|
|
1198 | (note that only a single file descriptor was used in the benchmark, so |
|
|
1199 | inefficiencies of C<poll> do not account for this). |
|
|
1200 | |
|
|
1201 | The C<Tk> adaptor works relatively well. The fact that it crashes with |
|
|
1202 | more than 2000 watchers is a big setback, however, as correctness takes |
|
|
1203 | precedence over speed. Nevertheless, its performance is surprising, as the |
|
|
1204 | file descriptor is dup()ed for each watcher. This shows that the dup() |
|
|
1205 | employed by some adaptors is not a big performance issue (it does incur a |
|
|
1206 | hidden memory cost inside the kernel which is not reflected in the figures |
|
|
1207 | above). |
|
|
1208 | |
|
|
1209 | C<POE>, regardless of underlying event loop (whether using its pure perl |
|
|
1210 | select-based backend or the Event module, the POE-EV backend couldn't |
|
|
1211 | be tested because it wasn't working) shows abysmal performance and |
|
|
1212 | memory usage with AnyEvent: Watchers use almost 30 times as much memory |
|
|
1213 | as EV watchers, and 10 times as much memory as Event (the high memory |
|
|
1214 | requirements are caused by requiring a session for each watcher). Watcher |
|
|
1215 | invocation speed is almost 900 times slower than with AnyEvent's pure perl |
|
|
1216 | implementation. |
|
|
1217 | |
|
|
1218 | The design of the POE adaptor class in AnyEvent can not really account |
|
|
1219 | for the performance issues, though, as session creation overhead is |
|
|
1220 | small compared to execution of the state machine, which is coded pretty |
|
|
1221 | optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that |
|
|
1222 | using multiple sessions is not a good approach, especially regarding |
|
|
1223 | memory usage, even the author of POE could not come up with a faster |
|
|
1224 | design). |
|
|
1225 | |
|
|
1226 | =head3 Summary |
|
|
1227 | |
|
|
1228 | =over 4 |
|
|
1229 | |
|
|
1230 | =item * Using EV through AnyEvent is faster than any other event loop |
|
|
1231 | (even when used without AnyEvent), but most event loops have acceptable |
|
|
1232 | performance with or without AnyEvent. |
|
|
1233 | |
|
|
1234 | =item * The overhead AnyEvent adds is usually much smaller than the overhead of |
|
|
1235 | the actual event loop, only with extremely fast event loops such as EV |
|
|
1236 | adds AnyEvent significant overhead. |
|
|
1237 | |
|
|
1238 | =item * You should avoid POE like the plague if you want performance or |
|
|
1239 | reasonable memory usage. |
|
|
1240 | |
|
|
1241 | =back |
|
|
1242 | |
|
|
1243 | =head2 BENCHMARKING THE LARGE SERVER CASE |
|
|
1244 | |
|
|
1245 | This benchmark atcually benchmarks the event loop itself. It works by |
|
|
1246 | creating a number of "servers": each server consists of a socketpair, a |
|
|
1247 | timeout watcher that gets reset on activity (but never fires), and an I/O |
|
|
1248 | watcher waiting for input on one side of the socket. Each time the socket |
|
|
1249 | watcher reads a byte it will write that byte to a random other "server". |
|
|
1250 | |
|
|
1251 | The effect is that there will be a lot of I/O watchers, only part of which |
|
|
1252 | are active at any one point (so there is a constant number of active |
|
|
1253 | fds for each loop iterstaion, but which fds these are is random). The |
|
|
1254 | timeout is reset each time something is read because that reflects how |
|
|
1255 | most timeouts work (and puts extra pressure on the event loops). |
|
|
1256 | |
|
|
1257 | In this benchmark, we use 10000 socketpairs (20000 sockets), of which 100 |
|
|
1258 | (1%) are active. This mirrors the activity of large servers with many |
|
|
1259 | connections, most of which are idle at any one point in time. |
|
|
1260 | |
|
|
1261 | Source code for this benchmark is found as F<eg/bench2> in the AnyEvent |
|
|
1262 | distribution. |
|
|
1263 | |
|
|
1264 | =head3 Explanation of the columns |
|
|
1265 | |
|
|
1266 | I<sockets> is the number of sockets, and twice the number of "servers" (as |
|
|
1267 | each server has a read and write socket end). |
|
|
1268 | |
|
|
1269 | I<create> is the time it takes to create a socketpair (which is |
|
|
1270 | nontrivial) and two watchers: an I/O watcher and a timeout watcher. |
|
|
1271 | |
|
|
1272 | I<request>, the most important value, is the time it takes to handle a |
|
|
1273 | single "request", that is, reading the token from the pipe and forwarding |
|
|
1274 | it to another server. This includes deleting the old timeout and creating |
|
|
1275 | a new one that moves the timeout into the future. |
|
|
1276 | |
|
|
1277 | =head3 Results |
|
|
1278 | |
|
|
1279 | name sockets create request |
|
|
1280 | EV 20000 69.01 11.16 |
|
|
1281 | Perl 20000 73.32 35.87 |
|
|
1282 | Event 20000 212.62 257.32 |
|
|
1283 | Glib 20000 651.16 1896.30 |
|
|
1284 | POE 20000 349.67 12317.24 uses POE::Loop::Event |
|
|
1285 | |
|
|
1286 | =head3 Discussion |
|
|
1287 | |
|
|
1288 | This benchmark I<does> measure scalability and overall performance of the |
|
|
1289 | particular event loop. |
|
|
1290 | |
|
|
1291 | EV is again fastest. Since it is using epoll on my system, the setup time |
|
|
1292 | is relatively high, though. |
|
|
1293 | |
|
|
1294 | Perl surprisingly comes second. It is much faster than the C-based event |
|
|
1295 | loops Event and Glib. |
|
|
1296 | |
|
|
1297 | Event suffers from high setup time as well (look at its code and you will |
|
|
1298 | understand why). Callback invocation also has a high overhead compared to |
|
|
1299 | the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event |
|
|
1300 | uses select or poll in basically all documented configurations. |
|
|
1301 | |
|
|
1302 | Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It |
|
|
1303 | clearly fails to perform with many filehandles or in busy servers. |
|
|
1304 | |
|
|
1305 | POE is still completely out of the picture, taking over 1000 times as long |
|
|
1306 | as EV, and over 100 times as long as the Perl implementation, even though |
|
|
1307 | it uses a C-based event loop in this case. |
|
|
1308 | |
|
|
1309 | =head3 Summary |
|
|
1310 | |
|
|
1311 | =over 4 |
|
|
1312 | |
|
|
1313 | =item * The pure perl implementation performs extremely well. |
|
|
1314 | |
|
|
1315 | =item * Avoid Glib or POE in large projects where performance matters. |
|
|
1316 | |
|
|
1317 | =back |
|
|
1318 | |
|
|
1319 | =head2 BENCHMARKING SMALL SERVERS |
|
|
1320 | |
|
|
1321 | While event loops should scale (and select-based ones do not...) even to |
|
|
1322 | large servers, most programs we (or I :) actually write have only a few |
|
|
1323 | I/O watchers. |
|
|
1324 | |
|
|
1325 | In this benchmark, I use the same benchmark program as in the large server |
|
|
1326 | case, but it uses only eight "servers", of which three are active at any |
|
|
1327 | one time. This should reflect performance for a small server relatively |
|
|
1328 | well. |
|
|
1329 | |
|
|
1330 | The columns are identical to the previous table. |
|
|
1331 | |
|
|
1332 | =head3 Results |
|
|
1333 | |
|
|
1334 | name sockets create request |
|
|
1335 | EV 16 20.00 6.54 |
|
|
1336 | Perl 16 25.75 12.62 |
|
|
1337 | Event 16 81.27 35.86 |
|
|
1338 | Glib 16 32.63 15.48 |
|
|
1339 | POE 16 261.87 276.28 uses POE::Loop::Event |
|
|
1340 | |
|
|
1341 | =head3 Discussion |
|
|
1342 | |
|
|
1343 | The benchmark tries to test the performance of a typical small |
|
|
1344 | server. While knowing how various event loops perform is interesting, keep |
|
|
1345 | in mind that their overhead in this case is usually not as important, due |
|
|
1346 | to the small absolute number of watchers (that is, you need efficiency and |
|
|
1347 | speed most when you have lots of watchers, not when you only have a few of |
|
|
1348 | them). |
|
|
1349 | |
|
|
1350 | EV is again fastest. |
|
|
1351 | |
|
|
1352 | Perl again comes second. It is noticably faster than the C-based event |
|
|
1353 | loops Event and Glib, although the difference is too small to really |
|
|
1354 | matter. |
|
|
1355 | |
|
|
1356 | POE also performs much better in this case, but is is still far behind the |
|
|
1357 | others. |
|
|
1358 | |
|
|
1359 | =head3 Summary |
|
|
1360 | |
|
|
1361 | =over 4 |
|
|
1362 | |
|
|
1363 | =item * C-based event loops perform very well with small number of |
|
|
1364 | watchers, as the management overhead dominates. |
|
|
1365 | |
|
|
1366 | =back |
|
|
1367 | |
|
|
1368 | |
839 | =head1 FORK |
1369 | =head1 FORK |
840 | |
1370 | |
841 | Most event libraries are not fork-safe. The ones who are usually are |
1371 | Most event libraries are not fork-safe. The ones who are usually are |
842 | because they are so inefficient. Only L<EV> is fully fork-aware. |
1372 | because they rely on inefficient but fork-safe C<select> or C<poll> |
|
|
1373 | calls. Only L<EV> is fully fork-aware. |
843 | |
1374 | |
844 | If you have to fork, you must either do so I<before> creating your first |
1375 | If you have to fork, you must either do so I<before> creating your first |
845 | watcher OR you must not use AnyEvent at all in the child. |
1376 | watcher OR you must not use AnyEvent at all in the child. |
|
|
1377 | |
846 | |
1378 | |
847 | =head1 SECURITY CONSIDERATIONS |
1379 | =head1 SECURITY CONSIDERATIONS |
848 | |
1380 | |
849 | AnyEvent can be forced to load any event model via |
1381 | AnyEvent can be forced to load any event model via |
850 | $ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to |
1382 | $ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to |
… | |
… | |
858 | |
1390 | |
859 | BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} } |
1391 | BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} } |
860 | |
1392 | |
861 | use AnyEvent; |
1393 | use AnyEvent; |
862 | |
1394 | |
|
|
1395 | Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can |
|
|
1396 | be used to probe what backend is used and gain other information (which is |
|
|
1397 | probably even less useful to an attacker than PERL_ANYEVENT_MODEL). |
|
|
1398 | |
|
|
1399 | |
863 | =head1 SEE ALSO |
1400 | =head1 SEE ALSO |
864 | |
1401 | |
865 | Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>, |
1402 | Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>, |
866 | L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>, |
1403 | L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>, |
867 | L<Event::Lib>, L<Qt>. |
1404 | L<Event::Lib>, L<Qt>, L<POE>. |
868 | |
1405 | |
869 | Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>, |
1406 | Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>, |
870 | L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>, |
1407 | L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>, |
871 | L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>, |
1408 | L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>, |
872 | L<AnyEvent::Impl::Qt>. |
1409 | L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>. |
873 | |
1410 | |
874 | Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>. |
1411 | Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>. |
|
|
1412 | |
875 | |
1413 | |
876 | =head1 AUTHOR |
1414 | =head1 AUTHOR |
877 | |
1415 | |
878 | Marc Lehmann <schmorp@schmorp.de> |
1416 | Marc Lehmann <schmorp@schmorp.de> |
879 | http://home.schmorp.de/ |
1417 | http://home.schmorp.de/ |