1 | NAME |
1 | NAME |
2 | AnyEvent - provide framework for multiple event loops |
2 | AnyEvent - provide framework for multiple event loops |
3 | |
3 | |
4 | Event, Coro, Glib, Tk, Perl - various supported event loops |
4 | EV, Event, Coro::EV, Coro::Event, Glib, Tk, Perl - various supported |
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5 | event loops |
5 | |
6 | |
6 | SYNOPSIS |
7 | SYNOPSIS |
7 | use AnyEvent; |
8 | use AnyEvent; |
8 | |
9 | |
9 | my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub { |
10 | my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub { |
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15 | }); |
16 | }); |
16 | |
17 | |
17 | my $w = AnyEvent->condvar; # stores wether a condition was flagged |
18 | my $w = AnyEvent->condvar; # stores wether a condition was flagged |
18 | $w->wait; # enters "main loop" till $condvar gets ->broadcast |
19 | $w->wait; # enters "main loop" till $condvar gets ->broadcast |
19 | $w->broadcast; # wake up current and all future wait's |
20 | $w->broadcast; # wake up current and all future wait's |
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21 | |
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22 | WHY YOU SHOULD USE THIS MODULE (OR NOT) |
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23 | Glib, POE, IO::Async, Event... CPAN offers event models by the dozen |
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24 | nowadays. So what is different about AnyEvent? |
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25 | |
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26 | Executive Summary: AnyEvent is *compatible*, AnyEvent is *free of |
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27 | policy* and AnyEvent is *small and efficient*. |
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28 | |
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29 | First and foremost, *AnyEvent is not an event model* itself, it only |
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30 | interfaces to whatever event model the main program happens to use in a |
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31 | pragmatic way. For event models and certain classes of immortals alike, |
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32 | the statement "there can only be one" is a bitter reality, and AnyEvent |
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33 | helps hiding the differences. |
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34 | |
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35 | The goal of AnyEvent is to offer module authors the ability to do event |
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36 | programming (waiting for I/O or timer events) without subscribing to a |
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37 | religion, a way of living, and most importantly: without forcing your |
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38 | module users into the same thing by forcing them to use the same event |
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39 | model you use. |
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40 | |
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41 | For modules like POE or IO::Async (which is actually doing all I/O |
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42 | *synchronously*...), using them in your module is like joining a cult: |
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43 | After you joined, you are dependent on them and you cannot use anything |
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44 | else, as it is simply incompatible to everything that isn't itself. |
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45 | |
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46 | AnyEvent + POE works fine. AnyEvent + Glib works fine. AnyEvent + Tk |
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47 | works fine etc. etc. but none of these work together with the rest: POE |
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48 | + IO::Async? no go. Tk + Event? no go. If your module uses one of those, |
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49 | every user of your module has to use it, too. If your module uses |
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50 | AnyEvent, it works transparently with all event models it supports |
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51 | (including stuff like POE and IO::Async). |
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52 | |
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53 | In addition of being free of having to use *the one and only true event |
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54 | model*, AnyEvent also is free of bloat and policy: with POE or similar |
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55 | modules, you get an enourmous amount of code and strict rules you have |
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56 | to follow. AnyEvent, on the other hand, is lean and to the point by only |
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57 | offering the functionality that is useful, in as thin as a wrapper as |
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58 | technically possible. |
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59 | |
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60 | Of course, if you want lots of policy (this can arguably be somewhat |
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61 | useful) and you want to force your users to use the one and only event |
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62 | model, you should *not* use this module. |
20 | |
63 | |
21 | DESCRIPTION |
64 | DESCRIPTION |
22 | AnyEvent provides an identical interface to multiple event loops. This |
65 | AnyEvent provides an identical interface to multiple event loops. This |
23 | allows module authors to utilise an event loop without forcing module |
66 | allows module authors to utilise an event loop without forcing module |
24 | users to use the same event loop (as only a single event loop can |
67 | users to use the same event loop (as only a single event loop can |
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27 | The interface itself is vaguely similar but not identical to the Event |
70 | The interface itself is vaguely similar but not identical to the Event |
28 | module. |
71 | module. |
29 | |
72 | |
30 | On the first call of any method, the module tries to detect the |
73 | On the first call of any method, the module tries to detect the |
31 | currently loaded event loop by probing wether any of the following |
74 | currently loaded event loop by probing wether any of the following |
32 | modules is loaded: Coro::Event, Event, Glib, Tk. The first one found is |
75 | modules is loaded: Coro::EV, Coro::Event, EV, Event, Glib, Tk. The first |
33 | used. If none is found, the module tries to load these modules in the |
76 | one found is used. If none are found, the module tries to load these |
34 | order given. The first one that could be successfully loaded will be |
77 | modules in the order given. The first one that could be successfully |
35 | used. If still none could be found, AnyEvent will fall back to a |
78 | loaded will be used. If still none could be found, AnyEvent will fall |
36 | pure-perl event loop, which is also not very efficient. |
79 | back to a pure-perl event loop, which is also not very efficient. |
37 | |
80 | |
38 | Because AnyEvent first checks for modules that are already loaded, |
81 | Because AnyEvent first checks for modules that are already loaded, |
39 | loading an Event model explicitly before first using AnyEvent will |
82 | loading an Event model explicitly before first using AnyEvent will |
40 | likely make that model the default. For example: |
83 | likely make that model the default. For example: |
41 | |
84 | |
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65 | You can create I/O watcher by calling the "AnyEvent->io" method with the |
108 | You can create I/O watcher by calling the "AnyEvent->io" method with the |
66 | following mandatory arguments: |
109 | following mandatory arguments: |
67 | |
110 | |
68 | "fh" the Perl *filehandle* (not filedescriptor) to watch for events. |
111 | "fh" the Perl *filehandle* (not filedescriptor) to watch for events. |
69 | "poll" must be a string that is either "r" or "w", that creates a |
112 | "poll" must be a string that is either "r" or "w", that creates a |
70 | watcher waiting for "r"eadable or "w"ritable events. "cb" teh callback |
113 | watcher waiting for "r"eadable or "w"ritable events. "cb" the callback |
71 | to invoke everytime the filehandle becomes ready. |
114 | to invoke everytime the filehandle becomes ready. |
72 | |
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73 | Only one io watcher per "fh" and "poll" combination is allowed (i.e. on |
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74 | a socket you can have one r + one w, not any more (limitation comes from |
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75 | Tk - if you are sure you are not using Tk this limitation is gone). |
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76 | |
115 | |
77 | Filehandles will be kept alive, so as long as the watcher exists, the |
116 | Filehandles will be kept alive, so as long as the watcher exists, the |
78 | filehandle exists, too. |
117 | filehandle exists, too. |
79 | |
118 | |
80 | Example: |
119 | Example: |
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103 | my $w = AnyEvent->timer (after => 7.7, cb => sub { |
142 | my $w = AnyEvent->timer (after => 7.7, cb => sub { |
104 | warn "timeout\n"; |
143 | warn "timeout\n"; |
105 | }); |
144 | }); |
106 | |
145 | |
107 | # to cancel the timer: |
146 | # to cancel the timer: |
108 | undef $w |
147 | undef $w; |
109 | |
148 | |
110 | CONDITION WATCHERS |
149 | CONDITION WATCHERS |
111 | Condition watchers can be created by calling the "AnyEvent->condvar" |
150 | Condition watchers can be created by calling the "AnyEvent->condvar" |
112 | method without any arguments. |
151 | method without any arguments. |
113 | |
152 | |
114 | A condition watcher watches for a condition - precisely that the |
153 | A condition watcher watches for a condition - precisely that the |
115 | "->broadcast" method has been called. |
154 | "->broadcast" method has been called. |
116 | |
155 | |
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156 | Note that condition watchers recurse into the event loop - if you have |
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157 | two watchers that call "->wait" in a round-robbin fashion, you lose. |
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158 | Therefore, condition watchers are good to export to your caller, but you |
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159 | should avoid making a blocking wait, at least in callbacks, as this |
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160 | usually asks for trouble. |
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161 | |
117 | The watcher has only two methods: |
162 | The watcher has only two methods: |
118 | |
163 | |
119 | $cv->wait |
164 | $cv->wait |
120 | Wait (blocking if necessary) until the "->broadcast" method has been |
165 | Wait (blocking if necessary) until the "->broadcast" method has been |
121 | called on c<$cv>, while servicing other watchers normally. |
166 | called on c<$cv>, while servicing other watchers normally. |
122 | |
167 | |
123 | Not all event models support a blocking wait - some die in that |
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124 | case, so if you are using this from a module, never require a |
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125 | blocking wait, but let the caller decide wether the call will block |
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126 | or not (for example, by coupling condition variables with some kind |
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127 | of request results and supporting callbacks so the caller knows that |
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128 | getting the result will not block, while still suppporting blockign |
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129 | waits if the caller so desires). |
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130 | |
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131 | You can only wait once on a condition - additional calls will return |
168 | You can only wait once on a condition - additional calls will return |
132 | immediately. |
169 | immediately. |
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170 | |
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171 | Not all event models support a blocking wait - some die in that case |
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172 | (programs might want to do that so they stay interactive), so *if |
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173 | you are using this from a module, never require a blocking wait*, |
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174 | but let the caller decide wether the call will block or not (for |
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175 | example, by coupling condition variables with some kind of request |
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176 | results and supporting callbacks so the caller knows that getting |
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177 | the result will not block, while still suppporting blocking waits if |
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178 | the caller so desires). |
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179 | |
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180 | Another reason *never* to "->wait" in a module is that you cannot |
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181 | sensibly have two "->wait"'s in parallel, as that would require |
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182 | multiple interpreters or coroutines/threads, none of which |
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183 | "AnyEvent" can supply (the coroutine-aware backends "Coro::EV" and |
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184 | "Coro::Event" explicitly support concurrent "->wait"'s from |
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185 | different coroutines, however). |
133 | |
186 | |
134 | $cv->broadcast |
187 | $cv->broadcast |
135 | Flag the condition as ready - a running "->wait" and all further |
188 | Flag the condition as ready - a running "->wait" and all further |
136 | calls to "wait" will return after this method has been called. If |
189 | calls to "wait" will return after this method has been called. If |
137 | nobody is waiting the broadcast will be remembered.. |
190 | nobody is waiting the broadcast will be remembered.. |
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180 | case AnyEvent has been extended at runtime (e.g. in *rxvt-unicode*). |
233 | case AnyEvent has been extended at runtime (e.g. in *rxvt-unicode*). |
181 | |
234 | |
182 | The known classes so far are: |
235 | The known classes so far are: |
183 | |
236 | |
184 | AnyEvent::Impl::CoroEV based on Coro::EV, best choice. |
237 | AnyEvent::Impl::CoroEV based on Coro::EV, best choice. |
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238 | AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice. |
185 | AnyEvent::Impl::EV based on EV (an interface to libev, also best choice). |
239 | AnyEvent::Impl::EV based on EV (an interface to libev, also best choice). |
186 | AnyEvent::Impl::Coro based on Coro::Event, second best choice. |
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187 | AnyEvent::Impl::Event based on Event, also second best choice :) |
240 | AnyEvent::Impl::Event based on Event, also second best choice :) |
188 | AnyEvent::Impl::Glib based on Glib, second-best choice. |
241 | AnyEvent::Impl::Glib based on Glib, third-best choice. |
189 | AnyEvent::Impl::Tk based on Tk, very bad choice. |
242 | AnyEvent::Impl::Tk based on Tk, very bad choice. |
190 | AnyEvent::Impl::Perl pure-perl implementation, inefficient. |
243 | AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable. |
191 | |
244 | |
192 | AnyEvent::detect |
245 | AnyEvent::detect |
193 | Returns $AnyEvent::MODEL, forcing autodetection of the event model |
246 | Returns $AnyEvent::MODEL, forcing autodetection of the event model |
194 | if necessary. You should only call this function right before you |
247 | if necessary. You should only call this function right before you |
195 | would have created an AnyEvent watcher anyway, that is, very late at |
248 | would have created an AnyEvent watcher anyway, that is, very late at |
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377 | |
430 | |
378 | 1. Blocking: |
431 | 1. Blocking: |
379 | |
432 | |
380 | my $data = $fcp->client_get ($url); |
433 | my $data = $fcp->client_get ($url); |
381 | |
434 | |
382 | 2. Blocking, but parallelizing: |
435 | 2. Blocking, but running in parallel: |
383 | |
436 | |
384 | my @datas = map $_->result, |
437 | my @datas = map $_->result, |
385 | map $fcp->txn_client_get ($_), |
438 | map $fcp->txn_client_get ($_), |
386 | @urls; |
439 | @urls; |
387 | |
440 | |
388 | Both blocking examples work without the module user having to know |
441 | Both blocking examples work without the module user having to know |
389 | anything about events. |
442 | anything about events. |
390 | |
443 | |
391 | 3a. Event-based in a main program, using any support Event module: |
444 | 3a. Event-based in a main program, using any supported event module: |
392 | |
445 | |
393 | use Event; |
446 | use EV; |
394 | |
447 | |
395 | $fcp->txn_client_get ($url)->cb (sub { |
448 | $fcp->txn_client_get ($url)->cb (sub { |
396 | my $txn = shift; |
449 | my $txn = shift; |
397 | my $data = $txn->result; |
450 | my $data = $txn->result; |
398 | ... |
451 | ... |
399 | }); |
452 | }); |
400 | |
453 | |
401 | Event::loop; |
454 | EV::loop; |
402 | |
455 | |
403 | 3b. The module user could use AnyEvent, too: |
456 | 3b. The module user could use AnyEvent, too: |
404 | |
457 | |
405 | use AnyEvent; |
458 | use AnyEvent; |
406 | |
459 | |
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412 | }); |
465 | }); |
413 | |
466 | |
414 | $quit->wait; |
467 | $quit->wait; |
415 | |
468 | |
416 | SEE ALSO |
469 | SEE ALSO |
417 | Event modules: Coro::Event, Coro, Event, Glib::Event, Glib. |
470 | Event modules: Coro::EV, EV, EV::Glib, Glib::EV, Coro::Event, Event, |
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471 | Glib::Event, Glib, Coro, Tk. |
418 | |
472 | |
419 | Implementations: AnyEvent::Impl::Coro, AnyEvent::Impl::Event, |
473 | Implementations: AnyEvent::Impl::CoroEV, AnyEvent::Impl::EV, |
420 | AnyEvent::Impl::Glib, AnyEvent::Impl::Tk. |
474 | AnyEvent::Impl::CoroEvent, AnyEvent::Impl::Event, AnyEvent::Impl::Glib, |
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475 | AnyEvent::Impl::Tk, AnyEvent::Impl::Perl. |
421 | |
476 | |
422 | Nontrivial usage example: Net::FCP. |
477 | Nontrivial usage examples: Net::FCP, Net::XMPP2. |
423 | |
478 | |
424 | |
479 | |