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, POE - various supported event loops |
5 | EV, 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 | |
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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? |
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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 | |
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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 |
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79 | The interface itself is vaguely similar, but not identical to the L<Event> |
78 | The interface itself is vaguely similar, but not identical to the L<Event> |
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<EV>, |
85 | L<Event>, L<Glib>, L<Tk>, L<AnyEvent::Impl::Perl>, L<Event::Lib>, L<Qt>, |
84 | L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>, |
86 | L<POE>. The first one found is used. If none are found, the module tries |
85 | L<POE>. The first one found is used. If none are found, the module tries |
87 | to load these modules (excluding Event::Lib, Qt and POE as the pure perl |
86 | to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl |
88 | adaptor should always succeed) in the order given. The first one that can |
87 | adaptor should always succeed) in the order given. The first one that can |
89 | be successfully loaded will be used. If, after this, still none could be |
88 | be successfully loaded will be used. If, after this, still none could be |
90 | found, AnyEvent will fall back to a pure-perl event loop, which is not |
89 | found, AnyEvent will fall back to a pure-perl event loop, which is not |
91 | very efficient, but should work everywhere. |
90 | very efficient, but should work everywhere. |
92 | |
91 | |
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136 | |
135 | |
137 | 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, |
138 | 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 |
139 | declared. |
138 | declared. |
140 | |
139 | |
141 | =head2 IO WATCHERS |
140 | =head2 I/O WATCHERS |
142 | |
141 | |
143 | You can create an I/O watcher by calling the C<< AnyEvent->io >> method |
142 | You can create an I/O watcher by calling the C<< AnyEvent->io >> method |
144 | with the following mandatory key-value pairs as arguments: |
143 | with the following mandatory key-value pairs as arguments: |
145 | |
144 | |
146 | C<fh> the Perl I<file handle> (I<not> file descriptor) to watch for |
145 | C<fh> the Perl I<file handle> (I<not> file descriptor) to watch |
147 | events. C<poll> must be a string that is either C<r> or C<w>, which |
146 | for events. C<poll> must be a string that is either C<r> or C<w>, |
148 | creates a watcher waiting for "r"eadable or "w"ritable events, |
147 | which creates a watcher waiting for "r"eadable or "w"ritable events, |
149 | respectively. C<cb> is the callback to invoke each time the file handle |
148 | respectively. C<cb> is the callback to invoke each time the file handle |
150 | becomes ready. |
149 | becomes ready. |
151 | |
150 | |
152 | 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 |
153 | copy of it alive/open. |
152 | presence is undefined and you cannot rely on them. Portable AnyEvent |
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153 | callbacks cannot use arguments passed to I/O watcher callbacks. |
154 | |
154 | |
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155 | The I/O watcher might use the underlying file descriptor or a copy of it. |
155 | 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 |
156 | on the underlying file descriptor. |
157 | underlying file descriptor. |
157 | |
158 | |
158 | Some event loops issue spurious readyness notifications, so you should |
159 | Some event loops issue spurious readyness notifications, so you should |
159 | 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 |
160 | handles. |
161 | handles. |
161 | |
162 | |
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172 | |
173 | |
173 | 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 >> |
174 | method with the following mandatory arguments: |
175 | method with the following mandatory arguments: |
175 | |
176 | |
176 | C<after> specifies after how many seconds (fractional values are |
177 | C<after> specifies after how many seconds (fractional values are |
177 | 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 |
178 | case. |
179 | in that case. |
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180 | |
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181 | Although the callback might get passed parameters, their value and |
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182 | presence is undefined and you cannot rely on them. Portable AnyEvent |
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183 | callbacks cannot use arguments passed to time watcher callbacks. |
179 | |
184 | |
180 | 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 |
181 | 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 |
182 | and Glib). |
187 | and Glib). |
183 | |
188 | |
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228 | |
233 | |
229 | 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 |
230 | 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 |
231 | be invoked whenever a signal occurs. |
236 | be invoked whenever a signal occurs. |
232 | |
237 | |
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238 | Although the callback might get passed parameters, their value and |
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239 | presence is undefined and you cannot rely on them. Portable AnyEvent |
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240 | callbacks cannot use arguments passed to signal watcher callbacks. |
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241 | |
233 | Multiple signal occurances can be clumped together into one callback |
242 | Multiple signal occurances can be clumped together into one callback |
234 | invocation, and callback invocation will be synchronous. synchronous means |
243 | invocation, and callback invocation will be synchronous. synchronous means |
235 | 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, |
236 | but it is guarenteed not to interrupt any other callbacks. |
245 | but it is guarenteed not to interrupt any other callbacks. |
237 | |
246 | |
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251 | |
260 | |
252 | 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 |
253 | 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 |
254 | 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 |
255 | 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 |
256 | and exit status (as returned by waitpid). |
265 | and exit status (as returned by waitpid), so unlike other watcher types, |
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266 | you I<can> rely on child watcher callback arguments. |
257 | |
267 | |
258 | Example: wait for pid 1333 |
268 | There is a slight catch to child watchers, however: you usually start them |
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269 | I<after> the child process was created, and this means the process could |
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270 | have exited already (and no SIGCHLD will be sent anymore). |
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271 | |
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272 | Not all event models handle this correctly (POE doesn't), but even for |
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273 | event models that I<do> handle this correctly, they usually need to be |
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274 | loaded before the process exits (i.e. before you fork in the first place). |
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275 | |
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276 | This means you cannot create a child watcher as the very first thing in an |
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277 | AnyEvent program, you I<have> to create at least one watcher before you |
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278 | C<fork> the child (alternatively, you can call C<AnyEvent::detect>). |
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279 | |
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280 | Example: fork a process and wait for it |
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281 | |
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282 | my $done = AnyEvent->condvar; |
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283 | |
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284 | AnyEvent::detect; # force event module to be initialised |
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285 | |
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286 | my $pid = fork or exit 5; |
259 | |
287 | |
260 | my $w = AnyEvent->child ( |
288 | my $w = AnyEvent->child ( |
261 | pid => 1333, |
289 | pid => $pid, |
262 | cb => sub { |
290 | cb => sub { |
263 | my ($pid, $status) = @_; |
291 | my ($pid, $status) = @_; |
264 | warn "pid $pid exited with status $status"; |
292 | warn "pid $pid exited with status $status"; |
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293 | $done->send; |
265 | }, |
294 | }, |
266 | ); |
295 | ); |
267 | |
296 | |
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297 | # do something else, then wait for process exit |
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298 | $done->wait; |
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299 | |
268 | =head2 CONDITION VARIABLES |
300 | =head2 CONDITION VARIABLES |
269 | |
301 | |
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302 | If you are familiar with some event loops you will know that all of them |
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303 | require you to run some blocking "loop", "run" or similar function that |
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304 | will actively watch for new events and call your callbacks. |
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305 | |
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306 | AnyEvent is different, it expects somebody else to run the event loop and |
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307 | will only block when necessary (usually when told by the user). |
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308 | |
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309 | The instrument to do that is called a "condition variable", so called |
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310 | because they represent a condition that must become true. |
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311 | |
270 | Condition variables can be created by calling the C<< AnyEvent->condvar >> |
312 | Condition variables can be created by calling the C<< AnyEvent->condvar |
271 | method without any arguments. |
313 | >> method, usually without arguments. The only argument pair allowed is |
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314 | C<cb>, which specifies a callback to be called when the condition variable |
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315 | becomes true. |
272 | |
316 | |
273 | A condition variable waits for a condition - precisely that the C<< |
317 | After creation, the conditon variable is "false" until it becomes "true" |
274 | ->broadcast >> method has been called. |
318 | by calling the C<send> method. |
275 | |
319 | |
276 | They are very useful to signal that a condition has been fulfilled, for |
320 | Condition variables are similar to callbacks, except that you can |
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321 | optionally wait for them. They can also be called merge points - points |
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322 | in time where multiple outstandign events have been processed. And yet |
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323 | another way to call them is transations - each condition variable can be |
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324 | used to represent a transaction, which finishes at some point and delivers |
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325 | a result. |
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326 | |
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327 | Condition variables are very useful to signal that something has finished, |
277 | example, if you write a module that does asynchronous http requests, |
328 | for example, if you write a module that does asynchronous http requests, |
278 | 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 |
279 | availability of results. |
330 | availability of results. The user can either act when the callback is |
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331 | called or can synchronously C<< ->wait >> for the results. |
280 | |
332 | |
281 | 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, |
282 | 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 |
283 | 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 |
284 | ->broadcast >> the "quit" event. |
336 | button of your app, which would C<< ->send >> the "quit" event. |
285 | |
337 | |
286 | 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 |
287 | 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 |
288 | 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 |
289 | 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, |
290 | as this asks for trouble. |
342 | as this asks for trouble. |
291 | |
343 | |
292 | This object has two methods: |
344 | Condition variables are represented by hash refs in perl, and the keys |
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345 | used by AnyEvent itself are all named C<_ae_XXX> to make subclassing |
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346 | easy (it is often useful to build your own transaction class on top of |
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347 | AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call |
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348 | it's C<new> method in your own C<new> method. |
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349 | |
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350 | There are two "sides" to a condition variable - the "producer side" which |
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351 | eventually calls C<< -> send >>, and the "consumer side", which waits |
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352 | for the send to occur. |
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353 | |
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354 | Example: |
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355 | |
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356 | # wait till the result is ready |
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357 | my $result_ready = AnyEvent->condvar; |
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358 | |
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359 | # do something such as adding a timer |
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360 | # or socket watcher the calls $result_ready->send |
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361 | # when the "result" is ready. |
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362 | # in this case, we simply use a timer: |
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363 | my $w = AnyEvent->timer ( |
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364 | after => 1, |
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365 | cb => sub { $result_ready->send }, |
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366 | ); |
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367 | |
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368 | # this "blocks" (while handling events) till the callback |
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369 | # calls send |
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370 | $result_ready->wait; |
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371 | |
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372 | =head3 METHODS FOR PRODUCERS |
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373 | |
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374 | These methods should only be used by the producing side, i.e. the |
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375 | code/module that eventually sends the signal. Note that it is also |
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376 | the producer side which creates the condvar in most cases, but it isn't |
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377 | uncommon for the consumer to create it as well. |
293 | |
378 | |
294 | =over 4 |
379 | =over 4 |
295 | |
380 | |
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381 | =item $cv->send (...) |
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382 | |
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383 | Flag the condition as ready - a running C<< ->wait >> and all further |
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384 | calls to C<wait> will (eventually) return after this method has been |
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385 | called. If nobody is waiting the send will be remembered. |
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386 | |
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387 | If a callback has been set on the condition variable, it is called |
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388 | immediately from within send. |
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389 | |
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390 | Any arguments passed to the C<send> call will be returned by all |
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391 | future C<< ->wait >> calls. |
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392 | |
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393 | =item $cv->croak ($error) |
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394 | |
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395 | Similar to send, but causes all call's wait C<< ->wait >> to invoke |
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396 | C<Carp::croak> with the given error message/object/scalar. |
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397 | |
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398 | This can be used to signal any errors to the condition variable |
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399 | user/consumer. |
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400 | |
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401 | =item $cv->begin ([group callback]) |
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402 | |
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403 | =item $cv->end |
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404 | |
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405 | These two methods can be used to combine many transactions/events into |
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406 | one. For example, a function that pings many hosts in parallel might want |
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407 | to use a condition variable for the whole process. |
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408 | |
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409 | Every call to C<< ->begin >> will increment a counter, and every call to |
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410 | C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end |
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411 | >>, the (last) callback passed to C<begin> will be executed. That callback |
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412 | is I<supposed> to call C<< ->send >>, but that is not required. If no |
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413 | callback was set, C<send> will be called without any arguments. |
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414 | |
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415 | Let's clarify this with the ping example: |
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416 | |
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417 | my $cv = AnyEvent->condvar; |
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418 | |
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419 | my %result; |
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420 | $cv->begin (sub { $cv->send (\%result) }); |
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421 | |
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422 | for my $host (@list_of_hosts) { |
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423 | $cv->begin; |
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424 | ping_host_then_call_callback $host, sub { |
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425 | $result{$host} = ...; |
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426 | $cv->end; |
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427 | }; |
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428 | } |
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429 | |
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430 | $cv->end; |
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431 | |
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432 | This code fragment supposedly pings a number of hosts and calls |
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433 | C<send> after results for all then have have been gathered - in any |
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434 | order. To achieve this, the code issues a call to C<begin> when it starts |
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435 | each ping request and calls C<end> when it has received some result for |
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436 | it. Since C<begin> and C<end> only maintain a counter, the order in which |
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437 | results arrive is not relevant. |
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438 | |
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439 | There is an additional bracketing call to C<begin> and C<end> outside the |
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440 | loop, which serves two important purposes: first, it sets the callback |
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441 | to be called once the counter reaches C<0>, and second, it ensures that |
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442 | C<send> is called even when C<no> hosts are being pinged (the loop |
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443 | doesn't execute once). |
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444 | |
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445 | This is the general pattern when you "fan out" into multiple subrequests: |
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446 | use an outer C<begin>/C<end> pair to set the callback and ensure C<end> |
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447 | is called at least once, and then, for each subrequest you start, call |
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448 | C<begin> and for eahc subrequest you finish, call C<end>. |
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449 | |
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450 | =back |
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451 | |
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452 | =head3 METHODS FOR CONSUMERS |
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453 | |
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454 | These methods should only be used by the consuming side, i.e. the |
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455 | code awaits the condition. |
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456 | |
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457 | =over 4 |
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458 | |
296 | =item $cv->wait |
459 | =item $cv->wait |
297 | |
460 | |
298 | Wait (blocking if necessary) until the C<< ->broadcast >> method has been |
461 | Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak |
299 | called on c<$cv>, while servicing other watchers normally. |
462 | >> methods have been called on c<$cv>, while servicing other watchers |
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463 | normally. |
300 | |
464 | |
301 | 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 |
302 | immediately. |
466 | will return immediately. |
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467 | |
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468 | If an error condition has been set by calling C<< ->croak >>, then this |
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469 | function will call C<croak>. |
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470 | |
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471 | In list context, all parameters passed to C<send> will be returned, |
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472 | in scalar context only the first one will be returned. |
303 | |
473 | |
304 | 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 |
305 | (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 |
306 | 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 |
307 | 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 |
… | |
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310 | while still suppporting blocking waits if the caller so desires). |
480 | while still suppporting blocking waits if the caller so desires). |
311 | |
481 | |
312 | Another reason I<never> to C<< ->wait >> in a module is that you cannot |
482 | Another reason I<never> to C<< ->wait >> in a module is that you cannot |
313 | sensibly have two C<< ->wait >>'s in parallel, as that would require |
483 | sensibly have two C<< ->wait >>'s in parallel, as that would require |
314 | multiple interpreters or coroutines/threads, none of which C<AnyEvent> |
484 | multiple interpreters or coroutines/threads, none of which C<AnyEvent> |
315 | can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and |
485 | can supply. |
316 | L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s |
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317 | from different coroutines, however). |
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318 | |
486 | |
319 | =item $cv->broadcast |
487 | The L<Coro> module, however, I<can> and I<does> supply coroutines and, in |
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488 | fact, L<Coro::AnyEvent> replaces AnyEvent's condvars by coroutine-safe |
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489 | versions and also integrates coroutines into AnyEvent, making blocking |
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490 | C<< ->wait >> calls perfectly safe as long as they are done from another |
|
|
491 | coroutine (one that doesn't run the event loop). |
320 | |
492 | |
321 | Flag the condition as ready - a running C<< ->wait >> and all further |
493 | You can ensure that C<< -wait >> never blocks by setting a callback and |
322 | calls to C<wait> will (eventually) return after this method has been |
494 | only calling C<< ->wait >> from within that callback (or at a later |
323 | called. If nobody is waiting the broadcast will be remembered.. |
495 | time). This will work even when the event loop does not support blocking |
|
|
496 | waits otherwise. |
|
|
497 | |
|
|
498 | =item $bool = $cv->ready |
|
|
499 | |
|
|
500 | Returns true when the condition is "true", i.e. whether C<send> or |
|
|
501 | C<croak> have been called. |
|
|
502 | |
|
|
503 | =item $cb = $cv->cb ([new callback]) |
|
|
504 | |
|
|
505 | This is a mutator function that returns the callback set and optionally |
|
|
506 | replaces it before doing so. |
|
|
507 | |
|
|
508 | The callback will be called when the condition becomes "true", i.e. when |
|
|
509 | C<send> or C<croak> are called. Calling C<wait> inside the callback |
|
|
510 | or at any later time is guaranteed not to block. |
324 | |
511 | |
325 | =back |
512 | =back |
326 | |
|
|
327 | Example: |
|
|
328 | |
|
|
329 | # wait till the result is ready |
|
|
330 | my $result_ready = AnyEvent->condvar; |
|
|
331 | |
|
|
332 | # do something such as adding a timer |
|
|
333 | # or socket watcher the calls $result_ready->broadcast |
|
|
334 | # when the "result" is ready. |
|
|
335 | # in this case, we simply use a timer: |
|
|
336 | my $w = AnyEvent->timer ( |
|
|
337 | after => 1, |
|
|
338 | cb => sub { $result_ready->broadcast }, |
|
|
339 | ); |
|
|
340 | |
|
|
341 | # this "blocks" (while handling events) till the watcher |
|
|
342 | # calls broadcast |
|
|
343 | $result_ready->wait; |
|
|
344 | |
513 | |
345 | =head1 GLOBAL VARIABLES AND FUNCTIONS |
514 | =head1 GLOBAL VARIABLES AND FUNCTIONS |
346 | |
515 | |
347 | =over 4 |
516 | =over 4 |
348 | |
517 | |
… | |
… | |
354 | C<AnyEvent::Impl:xxx> modules, but can be any other class in the case |
523 | C<AnyEvent::Impl:xxx> modules, but can be any other class in the case |
355 | AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>). |
524 | AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>). |
356 | |
525 | |
357 | The known classes so far are: |
526 | The known classes so far are: |
358 | |
527 | |
359 | AnyEvent::Impl::CoroEV based on Coro::EV, best choice. |
|
|
360 | AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice. |
|
|
361 | AnyEvent::Impl::EV based on EV (an interface to libev, best choice). |
528 | AnyEvent::Impl::EV based on EV (an interface to libev, best choice). |
362 | AnyEvent::Impl::Event based on Event, second best choice. |
529 | AnyEvent::Impl::Event based on Event, second best choice. |
|
|
530 | AnyEvent::Impl::Perl pure-perl implementation, fast and portable. |
363 | AnyEvent::Impl::Glib based on Glib, third-best choice. |
531 | AnyEvent::Impl::Glib based on Glib, third-best choice. |
364 | AnyEvent::Impl::Tk based on Tk, very bad choice. |
532 | AnyEvent::Impl::Tk based on Tk, very bad choice. |
365 | AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable. |
|
|
366 | AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs). |
533 | AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs). |
367 | AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse. |
534 | AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse. |
368 | AnyEvent::Impl::POE based on POE, not generic enough for full support. |
535 | AnyEvent::Impl::POE based on POE, not generic enough for full support. |
369 | |
536 | |
370 | There is no support for WxWidgets, as WxWidgets has no support for |
537 | There is no support for WxWidgets, as WxWidgets has no support for |
… | |
… | |
382 | Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model |
549 | Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model |
383 | if necessary. You should only call this function right before you would |
550 | if necessary. You should only call this function right before you would |
384 | have created an AnyEvent watcher anyway, that is, as late as possible at |
551 | have created an AnyEvent watcher anyway, that is, as late as possible at |
385 | runtime. |
552 | runtime. |
386 | |
553 | |
|
|
554 | =item $guard = AnyEvent::post_detect { BLOCK } |
|
|
555 | |
|
|
556 | Arranges for the code block to be executed as soon as the event model is |
|
|
557 | autodetected (or immediately if this has already happened). |
|
|
558 | |
|
|
559 | If called in scalar or list context, then it creates and returns an object |
|
|
560 | that automatically removes the callback again when it is destroyed. See |
|
|
561 | L<Coro::BDB> for a case where this is useful. |
|
|
562 | |
|
|
563 | =item @AnyEvent::post_detect |
|
|
564 | |
|
|
565 | If there are any code references in this array (you can C<push> to it |
|
|
566 | before or after loading AnyEvent), then they will called directly after |
|
|
567 | the event loop has been chosen. |
|
|
568 | |
|
|
569 | You should check C<$AnyEvent::MODEL> before adding to this array, though: |
|
|
570 | if it contains a true value then the event loop has already been detected, |
|
|
571 | and the array will be ignored. |
|
|
572 | |
|
|
573 | Best use C<AnyEvent::post_detect { BLOCK }> instead. |
|
|
574 | |
387 | =back |
575 | =back |
388 | |
576 | |
389 | =head1 WHAT TO DO IN A MODULE |
577 | =head1 WHAT TO DO IN A MODULE |
390 | |
578 | |
391 | As a module author, you should C<use AnyEvent> and call AnyEvent methods |
579 | As a module author, you should C<use AnyEvent> and call AnyEvent methods |
… | |
… | |
395 | decide which event module to use as soon as the first method is called, so |
583 | decide which event module to use as soon as the first method is called, so |
396 | by calling AnyEvent in your module body you force the user of your module |
584 | by calling AnyEvent in your module body you force the user of your module |
397 | to load the event module first. |
585 | to load the event module first. |
398 | |
586 | |
399 | Never call C<< ->wait >> on a condition variable unless you I<know> that |
587 | Never call C<< ->wait >> on a condition variable unless you I<know> that |
400 | the C<< ->broadcast >> method has been called on it already. This is |
588 | the C<< ->send >> method has been called on it already. This is |
401 | because it will stall the whole program, and the whole point of using |
589 | because it will stall the whole program, and the whole point of using |
402 | events is to stay interactive. |
590 | events is to stay interactive. |
403 | |
591 | |
404 | It is fine, however, to call C<< ->wait >> when the user of your module |
592 | It is fine, however, to call C<< ->wait >> when the user of your module |
405 | requests it (i.e. if you create a http request object ad have a method |
593 | requests it (i.e. if you create a http request object ad have a method |
… | |
… | |
425 | |
613 | |
426 | You can chose to use a rather inefficient pure-perl implementation by |
614 | You can chose to use a rather inefficient pure-perl implementation by |
427 | loading the C<AnyEvent::Impl::Perl> module, which gives you similar |
615 | loading the C<AnyEvent::Impl::Perl> module, which gives you similar |
428 | behaviour everywhere, but letting AnyEvent chose is generally better. |
616 | behaviour everywhere, but letting AnyEvent chose is generally better. |
429 | |
617 | |
|
|
618 | =head1 OTHER MODULES |
|
|
619 | |
|
|
620 | The following is a non-exhaustive list of additional modules that use |
|
|
621 | AnyEvent and can therefore be mixed easily with other AnyEvent modules |
|
|
622 | in the same program. Some of the modules come with AnyEvent, some are |
|
|
623 | available via CPAN. |
|
|
624 | |
|
|
625 | =over 4 |
|
|
626 | |
|
|
627 | =item L<AnyEvent::Util> |
|
|
628 | |
|
|
629 | Contains various utility functions that replace often-used but blocking |
|
|
630 | functions such as C<inet_aton> by event-/callback-based versions. |
|
|
631 | |
|
|
632 | =item L<AnyEvent::Handle> |
|
|
633 | |
|
|
634 | Provide read and write buffers and manages watchers for reads and writes. |
|
|
635 | |
|
|
636 | =item L<AnyEvent::Socket> |
|
|
637 | |
|
|
638 | Provides a means to do non-blocking connects, accepts etc. |
|
|
639 | |
|
|
640 | =item L<AnyEvent::HTTPD> |
|
|
641 | |
|
|
642 | Provides a simple web application server framework. |
|
|
643 | |
|
|
644 | =item L<AnyEvent::DNS> |
|
|
645 | |
|
|
646 | Provides asynchronous DNS resolver capabilities, beyond what |
|
|
647 | L<AnyEvent::Util> offers. |
|
|
648 | |
|
|
649 | =item L<AnyEvent::FastPing> |
|
|
650 | |
|
|
651 | The fastest ping in the west. |
|
|
652 | |
|
|
653 | =item L<Net::IRC3> |
|
|
654 | |
|
|
655 | AnyEvent based IRC client module family. |
|
|
656 | |
|
|
657 | =item L<Net::XMPP2> |
|
|
658 | |
|
|
659 | AnyEvent based XMPP (Jabber protocol) module family. |
|
|
660 | |
|
|
661 | =item L<Net::FCP> |
|
|
662 | |
|
|
663 | AnyEvent-based implementation of the Freenet Client Protocol, birthplace |
|
|
664 | of AnyEvent. |
|
|
665 | |
|
|
666 | =item L<Event::ExecFlow> |
|
|
667 | |
|
|
668 | High level API for event-based execution flow control. |
|
|
669 | |
|
|
670 | =item L<Coro> |
|
|
671 | |
|
|
672 | Has special support for AnyEvent via L<Coro::AnyEvent>. |
|
|
673 | |
|
|
674 | =item L<IO::Lambda> |
|
|
675 | |
|
|
676 | The lambda approach to I/O - don't ask, look there. Can use AnyEvent. |
|
|
677 | |
|
|
678 | =item L<IO::AIO> |
|
|
679 | |
|
|
680 | Truly asynchronous I/O, should be in the toolbox of every event |
|
|
681 | programmer. Can be trivially made to use AnyEvent. |
|
|
682 | |
|
|
683 | =item L<BDB> |
|
|
684 | |
|
|
685 | Truly asynchronous Berkeley DB access. Can be trivially made to use |
|
|
686 | AnyEvent. |
|
|
687 | |
|
|
688 | =back |
|
|
689 | |
430 | =cut |
690 | =cut |
431 | |
691 | |
432 | package AnyEvent; |
692 | package AnyEvent; |
433 | |
693 | |
434 | no warnings; |
694 | no warnings; |
435 | use strict; |
695 | use strict; |
436 | |
696 | |
437 | use Carp; |
697 | use Carp; |
438 | |
698 | |
439 | our $VERSION = '3.3'; |
699 | our $VERSION = '3.4'; |
440 | our $MODEL; |
700 | our $MODEL; |
441 | |
701 | |
442 | our $AUTOLOAD; |
702 | our $AUTOLOAD; |
443 | our @ISA; |
703 | our @ISA; |
444 | |
704 | |
445 | our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1; |
705 | our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1; |
446 | |
706 | |
447 | our @REGISTRY; |
707 | our @REGISTRY; |
448 | |
708 | |
449 | my @models = ( |
709 | my @models = ( |
450 | [Coro::EV:: => AnyEvent::Impl::CoroEV::], |
|
|
451 | [Coro::Event:: => AnyEvent::Impl::CoroEvent::], |
|
|
452 | [EV:: => AnyEvent::Impl::EV::], |
710 | [EV:: => AnyEvent::Impl::EV::], |
453 | [Event:: => AnyEvent::Impl::Event::], |
711 | [Event:: => AnyEvent::Impl::Event::], |
454 | [Glib:: => AnyEvent::Impl::Glib::], |
|
|
455 | [Tk:: => AnyEvent::Impl::Tk::], |
712 | [Tk:: => AnyEvent::Impl::Tk::], |
456 | [Wx:: => AnyEvent::Impl::POE::], |
713 | [Wx:: => AnyEvent::Impl::POE::], |
457 | [Prima:: => AnyEvent::Impl::POE::], |
714 | [Prima:: => AnyEvent::Impl::POE::], |
458 | [AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::], |
715 | [AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::], |
459 | # everything below here will not be autoprobed as the pureperl backend should work everywhere |
716 | # everything below here will not be autoprobed as the pureperl backend should work everywhere |
|
|
717 | [Glib:: => AnyEvent::Impl::Glib::], |
460 | [Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy |
718 | [Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy |
461 | [Qt:: => AnyEvent::Impl::Qt::], # requires special main program |
719 | [Qt:: => AnyEvent::Impl::Qt::], # requires special main program |
462 | [POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza |
720 | [POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza |
463 | ); |
721 | ); |
464 | |
722 | |
465 | our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY); |
723 | our %method = map +($_ => 1), qw(io timer signal child condvar one_event DESTROY); |
|
|
724 | |
|
|
725 | our @post_detect; |
|
|
726 | |
|
|
727 | sub post_detect(&) { |
|
|
728 | my ($cb) = @_; |
|
|
729 | |
|
|
730 | if ($MODEL) { |
|
|
731 | $cb->(); |
|
|
732 | |
|
|
733 | 1 |
|
|
734 | } else { |
|
|
735 | push @post_detect, $cb; |
|
|
736 | |
|
|
737 | defined wantarray |
|
|
738 | ? bless \$cb, "AnyEvent::Util::Guard" |
|
|
739 | : () |
|
|
740 | } |
|
|
741 | } |
|
|
742 | |
|
|
743 | sub AnyEvent::Util::Guard::DESTROY { |
|
|
744 | @post_detect = grep $_ != ${$_[0]}, @post_detect; |
|
|
745 | } |
466 | |
746 | |
467 | sub detect() { |
747 | sub detect() { |
468 | unless ($MODEL) { |
748 | unless ($MODEL) { |
469 | no strict 'refs'; |
749 | no strict 'refs'; |
470 | |
750 | |
… | |
… | |
504 | last; |
784 | last; |
505 | } |
785 | } |
506 | } |
786 | } |
507 | |
787 | |
508 | $MODEL |
788 | $MODEL |
509 | 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."; |
789 | or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib."; |
510 | } |
790 | } |
511 | } |
791 | } |
512 | |
792 | |
513 | unshift @ISA, $MODEL; |
793 | unshift @ISA, $MODEL; |
514 | push @{"$MODEL\::ISA"}, "AnyEvent::Base"; |
794 | push @{"$MODEL\::ISA"}, "AnyEvent::Base"; |
|
|
795 | |
|
|
796 | (shift @post_detect)->() while @post_detect; |
515 | } |
797 | } |
516 | |
798 | |
517 | $MODEL |
799 | $MODEL |
518 | } |
800 | } |
519 | |
801 | |
… | |
… | |
706 | |
988 | |
707 | =back |
989 | =back |
708 | |
990 | |
709 | =head1 EXAMPLE PROGRAM |
991 | =head1 EXAMPLE PROGRAM |
710 | |
992 | |
711 | The following program uses an IO watcher to read data from STDIN, a timer |
993 | The following program uses an I/O watcher to read data from STDIN, a timer |
712 | to display a message once per second, and a condition variable to quit the |
994 | to display a message once per second, and a condition variable to quit the |
713 | program when the user enters quit: |
995 | program when the user enters quit: |
714 | |
996 | |
715 | use AnyEvent; |
997 | use AnyEvent; |
716 | |
998 | |
… | |
… | |
861 | }); |
1143 | }); |
862 | |
1144 | |
863 | $quit->wait; |
1145 | $quit->wait; |
864 | |
1146 | |
865 | |
1147 | |
866 | =head1 BENCHMARK |
1148 | =head1 BENCHMARKS |
867 | |
1149 | |
868 | To give you an idea of the performance and overheads that AnyEvent adds |
1150 | To give you an idea of the performance and overheads that AnyEvent adds |
869 | over the event loops themselves (and to give you an impression of the |
1151 | over the event loops themselves and to give you an impression of the speed |
870 | speed of various event loops), here is a benchmark of various supported |
1152 | of various event loops I prepared some benchmarks. |
871 | event models natively and with anyevent. The benchmark creates a lot of |
1153 | |
872 | timers (with a zero timeout) and io watchers (watching STDOUT, a pty, to |
1154 | =head2 BENCHMARKING ANYEVENT OVERHEAD |
|
|
1155 | |
|
|
1156 | Here is a benchmark of various supported event models used natively and |
|
|
1157 | through anyevent. The benchmark creates a lot of timers (with a zero |
|
|
1158 | timeout) and I/O watchers (watching STDOUT, a pty, to become writable, |
873 | become writable, which it is), lets them fire exactly once and destroys |
1159 | which it is), lets them fire exactly once and destroys them again. |
874 | them again. |
|
|
875 | |
1160 | |
|
|
1161 | Source code for this benchmark is found as F<eg/bench> in the AnyEvent |
|
|
1162 | distribution. |
|
|
1163 | |
876 | =head2 Explanation of the columns |
1164 | =head3 Explanation of the columns |
877 | |
1165 | |
878 | I<watcher> is the number of event watchers created/destroyed. Since |
1166 | I<watcher> is the number of event watchers created/destroyed. Since |
879 | different event models feature vastly different performances, each event |
1167 | different event models feature vastly different performances, each event |
880 | loop was given a number of watchers so that overall runtime is acceptable |
1168 | loop was given a number of watchers so that overall runtime is acceptable |
881 | and similar between tested event loop (and keep them from crashing): Glib |
1169 | and similar between tested event loop (and keep them from crashing): Glib |
… | |
… | |
897 | signal the end of this phase. |
1185 | signal the end of this phase. |
898 | |
1186 | |
899 | I<destroy> is the time, in microseconds, that it takes to destroy a single |
1187 | I<destroy> is the time, in microseconds, that it takes to destroy a single |
900 | watcher. |
1188 | watcher. |
901 | |
1189 | |
902 | =head2 Results |
1190 | =head3 Results |
903 | |
1191 | |
904 | name watchers bytes create invoke destroy comment |
1192 | name watchers bytes create invoke destroy comment |
905 | EV/EV 400000 244 0.56 0.46 0.31 EV native interface |
1193 | EV/EV 400000 244 0.56 0.46 0.31 EV native interface |
906 | EV/Any 100000 610 3.52 0.91 0.75 EV + AnyEvent watchers |
1194 | EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers |
907 | CoroEV/Any 100000 610 3.49 0.92 0.75 coroutines + Coro::Signal |
1195 | CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal |
908 | Perl/Any 16000 654 4.64 1.22 0.77 pure perl implementation |
1196 | Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation |
909 | Event/Event 16000 523 28.05 21.38 0.86 Event native interface |
1197 | Event/Event 16000 516 31.88 31.30 0.85 Event native interface |
910 | Event/Any 16000 943 34.43 20.48 1.39 Event + AnyEvent watchers |
1198 | Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers |
911 | Glib/Any 16000 1357 96.99 12.55 55.51 quadratic behaviour |
1199 | Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour |
912 | Tk/Any 2000 1855 27.01 66.61 14.03 SEGV with >> 2000 watchers |
1200 | Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers |
913 | POE/Event 2000 6644 108.15 768.19 14.33 via POE::Loop::Event |
1201 | POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event |
914 | POE/Select 2000 6343 94.69 807.65 562.69 via POE::Loop::Select |
1202 | POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select |
915 | |
1203 | |
916 | =head2 Discussion |
1204 | =head3 Discussion |
917 | |
1205 | |
918 | The benchmark does I<not> measure scalability of the event loop very |
1206 | The benchmark does I<not> measure scalability of the event loop very |
919 | well. For example, a select-based event loop (such as the pure perl one) |
1207 | well. For example, a select-based event loop (such as the pure perl one) |
920 | can never compete with an event loop that uses epoll when the number of |
1208 | can never compete with an event loop that uses epoll when the number of |
921 | file descriptors grows high. In this benchmark, only a single filehandle |
1209 | file descriptors grows high. In this benchmark, all events become ready at |
922 | is used (although some of the AnyEvent adaptors dup() its file descriptor |
1210 | the same time, so select/poll-based implementations get an unnatural speed |
923 | to worka round bugs). |
1211 | boost. |
|
|
1212 | |
|
|
1213 | Also, note that the number of watchers usually has a nonlinear effect on |
|
|
1214 | overall speed, that is, creating twice as many watchers doesn't take twice |
|
|
1215 | the time - usually it takes longer. This puts event loops tested with a |
|
|
1216 | higher number of watchers at a disadvantage. |
|
|
1217 | |
|
|
1218 | To put the range of results into perspective, consider that on the |
|
|
1219 | benchmark machine, handling an event takes roughly 1600 CPU cycles with |
|
|
1220 | EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU |
|
|
1221 | cycles with POE. |
924 | |
1222 | |
925 | C<EV> is the sole leader regarding speed and memory use, which are both |
1223 | C<EV> is the sole leader regarding speed and memory use, which are both |
926 | maximal/minimal, respectively. Even when going through AnyEvent, there is |
1224 | maximal/minimal, respectively. Even when going through AnyEvent, it uses |
927 | only one event loop that uses less memory (the C<Event> module natively), and |
1225 | far less memory than any other event loop and is still faster than Event |
928 | no faster event model, not event C<Event> natively. |
1226 | natively. |
929 | |
1227 | |
930 | The pure perl implementation is hit in a few sweet spots (both the |
1228 | The pure perl implementation is hit in a few sweet spots (both the |
931 | zero timeout and the use of a single fd hit optimisations in the perl |
1229 | constant timeout and the use of a single fd hit optimisations in the perl |
932 | interpreter and the backend itself). Nevertheless tis shows that it |
1230 | interpreter and the backend itself). Nevertheless this shows that it |
933 | adds very little overhead in itself. Like any select-based backend its |
1231 | adds very little overhead in itself. Like any select-based backend its |
934 | performance becomes really bad with lots of file descriptors, of course, |
1232 | performance becomes really bad with lots of file descriptors (and few of |
935 | but this was not subjetc of this benchmark. |
1233 | them active), of course, but this was not subject of this benchmark. |
936 | |
1234 | |
937 | The C<Event> module has a relatively high setup and callback invocation cost, |
1235 | The C<Event> module has a relatively high setup and callback invocation |
938 | but overall scores on the third place. |
1236 | cost, but overall scores in on the third place. |
939 | |
1237 | |
940 | C<Glib>'s memory usage is quite a bit bit higher, but it features a |
1238 | C<Glib>'s memory usage is quite a bit higher, but it features a |
941 | faster callback invocation and overall ends up in the same class as |
1239 | faster callback invocation and overall ends up in the same class as |
942 | C<Event>. However, Glib scales extremely badly, doubling the number of |
1240 | C<Event>. However, Glib scales extremely badly, doubling the number of |
943 | watchers increases the processing time by more than a factor of four, |
1241 | watchers increases the processing time by more than a factor of four, |
944 | making it completely unusable when using larger numbers of watchers |
1242 | making it completely unusable when using larger numbers of watchers |
945 | (note that only a single file descriptor was used in the benchmark, so |
1243 | (note that only a single file descriptor was used in the benchmark, so |
… | |
… | |
948 | The C<Tk> adaptor works relatively well. The fact that it crashes with |
1246 | The C<Tk> adaptor works relatively well. The fact that it crashes with |
949 | more than 2000 watchers is a big setback, however, as correctness takes |
1247 | more than 2000 watchers is a big setback, however, as correctness takes |
950 | precedence over speed. Nevertheless, its performance is surprising, as the |
1248 | precedence over speed. Nevertheless, its performance is surprising, as the |
951 | file descriptor is dup()ed for each watcher. This shows that the dup() |
1249 | file descriptor is dup()ed for each watcher. This shows that the dup() |
952 | employed by some adaptors is not a big performance issue (it does incur a |
1250 | employed by some adaptors is not a big performance issue (it does incur a |
953 | hidden memory cost inside the kernel, though, that is not reflected in the |
1251 | hidden memory cost inside the kernel which is not reflected in the figures |
954 | figures above). |
1252 | above). |
955 | |
1253 | |
956 | C<POE>, regardless of underlying event loop (wether using its pure perl |
1254 | C<POE>, regardless of underlying event loop (whether using its pure perl |
957 | select-based backend or the Event module) shows abysmal performance and |
1255 | select-based backend or the Event module, the POE-EV backend couldn't |
|
|
1256 | be tested because it wasn't working) shows abysmal performance and |
958 | memory usage: Watchers use almost 30 times as much memory as EV watchers, |
1257 | memory usage with AnyEvent: Watchers use almost 30 times as much memory |
959 | and 10 times as much memory as both Event or EV via AnyEvent. Watcher |
1258 | as EV watchers, and 10 times as much memory as Event (the high memory |
|
|
1259 | requirements are caused by requiring a session for each watcher). Watcher |
960 | invocation is almost 700 times slower than with AnyEvent's pure perl |
1260 | invocation speed is almost 900 times slower than with AnyEvent's pure perl |
|
|
1261 | implementation. |
|
|
1262 | |
961 | implementation. The design of the POE adaptor class in AnyEvent can not |
1263 | The design of the POE adaptor class in AnyEvent can not really account |
962 | really account for this, as session creation overhead is small compared |
1264 | for the performance issues, though, as session creation overhead is |
963 | to execution of the state machine, which is coded pretty optimally within |
1265 | small compared to execution of the state machine, which is coded pretty |
964 | L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow. |
1266 | optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that |
|
|
1267 | using multiple sessions is not a good approach, especially regarding |
|
|
1268 | memory usage, even the author of POE could not come up with a faster |
|
|
1269 | design). |
965 | |
1270 | |
966 | =head2 Summary |
1271 | =head3 Summary |
967 | |
1272 | |
|
|
1273 | =over 4 |
|
|
1274 | |
968 | Using EV through AnyEvent is faster than any other event loop, but most |
1275 | =item * Using EV through AnyEvent is faster than any other event loop |
969 | event loops have acceptable performance with or without AnyEvent. |
1276 | (even when used without AnyEvent), but most event loops have acceptable |
|
|
1277 | performance with or without AnyEvent. |
970 | |
1278 | |
971 | The overhead AnyEvent adds is usually much smaller than the overhead of |
1279 | =item * The overhead AnyEvent adds is usually much smaller than the overhead of |
972 | the actual event loop, only with extremely fast event loops such as the EV |
1280 | the actual event loop, only with extremely fast event loops such as EV |
973 | adds AnyEvent significant overhead. |
1281 | adds AnyEvent significant overhead. |
974 | |
1282 | |
975 | And you should simply avoid POE like the plague if you want performance or |
1283 | =item * You should avoid POE like the plague if you want performance or |
976 | reasonable memory usage. |
1284 | reasonable memory usage. |
977 | |
1285 | |
|
|
1286 | =back |
|
|
1287 | |
|
|
1288 | =head2 BENCHMARKING THE LARGE SERVER CASE |
|
|
1289 | |
|
|
1290 | This benchmark atcually benchmarks the event loop itself. It works by |
|
|
1291 | creating a number of "servers": each server consists of a socketpair, a |
|
|
1292 | timeout watcher that gets reset on activity (but never fires), and an I/O |
|
|
1293 | watcher waiting for input on one side of the socket. Each time the socket |
|
|
1294 | watcher reads a byte it will write that byte to a random other "server". |
|
|
1295 | |
|
|
1296 | The effect is that there will be a lot of I/O watchers, only part of which |
|
|
1297 | are active at any one point (so there is a constant number of active |
|
|
1298 | fds for each loop iterstaion, but which fds these are is random). The |
|
|
1299 | timeout is reset each time something is read because that reflects how |
|
|
1300 | most timeouts work (and puts extra pressure on the event loops). |
|
|
1301 | |
|
|
1302 | In this benchmark, we use 10000 socketpairs (20000 sockets), of which 100 |
|
|
1303 | (1%) are active. This mirrors the activity of large servers with many |
|
|
1304 | connections, most of which are idle at any one point in time. |
|
|
1305 | |
|
|
1306 | Source code for this benchmark is found as F<eg/bench2> in the AnyEvent |
|
|
1307 | distribution. |
|
|
1308 | |
|
|
1309 | =head3 Explanation of the columns |
|
|
1310 | |
|
|
1311 | I<sockets> is the number of sockets, and twice the number of "servers" (as |
|
|
1312 | each server has a read and write socket end). |
|
|
1313 | |
|
|
1314 | I<create> is the time it takes to create a socketpair (which is |
|
|
1315 | nontrivial) and two watchers: an I/O watcher and a timeout watcher. |
|
|
1316 | |
|
|
1317 | I<request>, the most important value, is the time it takes to handle a |
|
|
1318 | single "request", that is, reading the token from the pipe and forwarding |
|
|
1319 | it to another server. This includes deleting the old timeout and creating |
|
|
1320 | a new one that moves the timeout into the future. |
|
|
1321 | |
|
|
1322 | =head3 Results |
|
|
1323 | |
|
|
1324 | name sockets create request |
|
|
1325 | EV 20000 69.01 11.16 |
|
|
1326 | Perl 20000 73.32 35.87 |
|
|
1327 | Event 20000 212.62 257.32 |
|
|
1328 | Glib 20000 651.16 1896.30 |
|
|
1329 | POE 20000 349.67 12317.24 uses POE::Loop::Event |
|
|
1330 | |
|
|
1331 | =head3 Discussion |
|
|
1332 | |
|
|
1333 | This benchmark I<does> measure scalability and overall performance of the |
|
|
1334 | particular event loop. |
|
|
1335 | |
|
|
1336 | EV is again fastest. Since it is using epoll on my system, the setup time |
|
|
1337 | is relatively high, though. |
|
|
1338 | |
|
|
1339 | Perl surprisingly comes second. It is much faster than the C-based event |
|
|
1340 | loops Event and Glib. |
|
|
1341 | |
|
|
1342 | Event suffers from high setup time as well (look at its code and you will |
|
|
1343 | understand why). Callback invocation also has a high overhead compared to |
|
|
1344 | the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event |
|
|
1345 | uses select or poll in basically all documented configurations. |
|
|
1346 | |
|
|
1347 | Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It |
|
|
1348 | clearly fails to perform with many filehandles or in busy servers. |
|
|
1349 | |
|
|
1350 | POE is still completely out of the picture, taking over 1000 times as long |
|
|
1351 | as EV, and over 100 times as long as the Perl implementation, even though |
|
|
1352 | it uses a C-based event loop in this case. |
|
|
1353 | |
|
|
1354 | =head3 Summary |
|
|
1355 | |
|
|
1356 | =over 4 |
|
|
1357 | |
|
|
1358 | =item * The pure perl implementation performs extremely well. |
|
|
1359 | |
|
|
1360 | =item * Avoid Glib or POE in large projects where performance matters. |
|
|
1361 | |
|
|
1362 | =back |
|
|
1363 | |
|
|
1364 | =head2 BENCHMARKING SMALL SERVERS |
|
|
1365 | |
|
|
1366 | While event loops should scale (and select-based ones do not...) even to |
|
|
1367 | large servers, most programs we (or I :) actually write have only a few |
|
|
1368 | I/O watchers. |
|
|
1369 | |
|
|
1370 | In this benchmark, I use the same benchmark program as in the large server |
|
|
1371 | case, but it uses only eight "servers", of which three are active at any |
|
|
1372 | one time. This should reflect performance for a small server relatively |
|
|
1373 | well. |
|
|
1374 | |
|
|
1375 | The columns are identical to the previous table. |
|
|
1376 | |
|
|
1377 | =head3 Results |
|
|
1378 | |
|
|
1379 | name sockets create request |
|
|
1380 | EV 16 20.00 6.54 |
|
|
1381 | Perl 16 25.75 12.62 |
|
|
1382 | Event 16 81.27 35.86 |
|
|
1383 | Glib 16 32.63 15.48 |
|
|
1384 | POE 16 261.87 276.28 uses POE::Loop::Event |
|
|
1385 | |
|
|
1386 | =head3 Discussion |
|
|
1387 | |
|
|
1388 | The benchmark tries to test the performance of a typical small |
|
|
1389 | server. While knowing how various event loops perform is interesting, keep |
|
|
1390 | in mind that their overhead in this case is usually not as important, due |
|
|
1391 | to the small absolute number of watchers (that is, you need efficiency and |
|
|
1392 | speed most when you have lots of watchers, not when you only have a few of |
|
|
1393 | them). |
|
|
1394 | |
|
|
1395 | EV is again fastest. |
|
|
1396 | |
|
|
1397 | Perl again comes second. It is noticably faster than the C-based event |
|
|
1398 | loops Event and Glib, although the difference is too small to really |
|
|
1399 | matter. |
|
|
1400 | |
|
|
1401 | POE also performs much better in this case, but is is still far behind the |
|
|
1402 | others. |
|
|
1403 | |
|
|
1404 | =head3 Summary |
|
|
1405 | |
|
|
1406 | =over 4 |
|
|
1407 | |
|
|
1408 | =item * C-based event loops perform very well with small number of |
|
|
1409 | watchers, as the management overhead dominates. |
|
|
1410 | |
|
|
1411 | =back |
|
|
1412 | |
978 | |
1413 | |
979 | =head1 FORK |
1414 | =head1 FORK |
980 | |
1415 | |
981 | Most event libraries are not fork-safe. The ones who are usually are |
1416 | Most event libraries are not fork-safe. The ones who are usually are |
982 | because they are so inefficient. Only L<EV> is fully fork-aware. |
1417 | because they rely on inefficient but fork-safe C<select> or C<poll> |
|
|
1418 | calls. Only L<EV> is fully fork-aware. |
983 | |
1419 | |
984 | If you have to fork, you must either do so I<before> creating your first |
1420 | If you have to fork, you must either do so I<before> creating your first |
985 | watcher OR you must not use AnyEvent at all in the child. |
1421 | watcher OR you must not use AnyEvent at all in the child. |
986 | |
1422 | |
987 | |
1423 | |
… | |
… | |
999 | |
1435 | |
1000 | BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} } |
1436 | BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} } |
1001 | |
1437 | |
1002 | use AnyEvent; |
1438 | use AnyEvent; |
1003 | |
1439 | |
|
|
1440 | Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can |
|
|
1441 | be used to probe what backend is used and gain other information (which is |
|
|
1442 | probably even less useful to an attacker than PERL_ANYEVENT_MODEL). |
|
|
1443 | |
1004 | |
1444 | |
1005 | =head1 SEE ALSO |
1445 | =head1 SEE ALSO |
1006 | |
1446 | |
1007 | Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>, |
1447 | Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>, |
1008 | L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>, |
|
|
1009 | L<Event::Lib>, L<Qt>, L<POE>. |
1448 | L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>. |
1010 | |
1449 | |
1011 | Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>, |
1450 | Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>, |
1012 | L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>, |
1451 | L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, |
1013 | L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>, |
1452 | L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>, |
1014 | L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>. |
1453 | L<AnyEvent::Impl::POE>. |
|
|
1454 | |
|
|
1455 | Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>, |
1015 | |
1456 | |
1016 | Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>. |
1457 | Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>. |
1017 | |
1458 | |
1018 | |
1459 | |
1019 | =head1 AUTHOR |
1460 | =head1 AUTHOR |