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 | |
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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 | |
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71 | #TODO# |
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72 | |
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73 | Net::IRC3 |
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74 | AnyEvent::HTTPD |
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75 | AnyEvent::DNS |
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76 | IO::AnyEvent |
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77 | Net::FPing |
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78 | Net::XMPP2 |
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79 | Coro |
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80 | |
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81 | AnyEvent::IRC |
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82 | AnyEvent::HTTPD |
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83 | AnyEvent::DNS |
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84 | AnyEvent::Handle |
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85 | AnyEvent::Socket |
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86 | AnyEvent::FPing |
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87 | AnyEvent::XMPP |
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88 | AnyEvent::SNMP |
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89 | Coro |
71 | |
90 | |
72 | =head1 DESCRIPTION |
91 | =head1 DESCRIPTION |
73 | |
92 | |
74 | L<AnyEvent> provides an identical interface to multiple event loops. This |
93 | L<AnyEvent> provides an identical interface to multiple event loops. This |
75 | allows module authors to utilise an event loop without forcing module |
94 | allows module authors to utilise an event loop without forcing module |
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78 | |
97 | |
79 | The interface itself is vaguely similar, but not identical to the L<Event> |
98 | The interface itself is vaguely similar, but not identical to the L<Event> |
80 | module. |
99 | module. |
81 | |
100 | |
82 | During the first call of any watcher-creation method, the module tries |
101 | 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 |
102 | to detect the currently loaded event loop by probing whether one of the |
84 | the following modules is already loaded: L<Coro::EV>, L<Coro::Event>, |
103 | following modules is already loaded: L<Coro::EV>, L<Coro::Event>, L<EV>, |
85 | L<EV>, L<Event>, L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>. The first one |
104 | L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>, |
86 | found is used. If none are found, the module tries to load these modules |
105 | L<POE>. The first one found is used. If none are found, the module tries |
87 | (excluding Event::Lib and Qt) in the order given. The first one that can |
106 | to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl |
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107 | adaptor should always succeed) in the order given. The first one that can |
88 | be successfully loaded will be used. If, after this, still none could be |
108 | be successfully loaded will be used. If, after this, still none could be |
89 | found, AnyEvent will fall back to a pure-perl event loop, which is not |
109 | found, AnyEvent will fall back to a pure-perl event loop, which is not |
90 | very efficient, but should work everywhere. |
110 | very efficient, but should work everywhere. |
91 | |
111 | |
92 | Because AnyEvent first checks for modules that are already loaded, loading |
112 | Because AnyEvent first checks for modules that are already loaded, loading |
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135 | |
155 | |
136 | Note that C<my $w; $w => combination. This is necessary because in Perl, |
156 | Note that C<my $w; $w => combination. This is necessary because in Perl, |
137 | my variables are only visible after the statement in which they are |
157 | my variables are only visible after the statement in which they are |
138 | declared. |
158 | declared. |
139 | |
159 | |
140 | =head2 IO WATCHERS |
160 | =head2 I/O WATCHERS |
141 | |
161 | |
142 | You can create an I/O watcher by calling the C<< AnyEvent->io >> method |
162 | You can create an I/O watcher by calling the C<< AnyEvent->io >> method |
143 | with the following mandatory key-value pairs as arguments: |
163 | with the following mandatory key-value pairs as arguments: |
144 | |
164 | |
145 | C<fh> the Perl I<file handle> (I<not> file descriptor) to watch for |
165 | C<fh> the Perl I<file handle> (I<not> file descriptor) to watch |
146 | events. C<poll> must be a string that is either C<r> or C<w>, which |
166 | for events. C<poll> must be a string that is either C<r> or C<w>, |
147 | creates a watcher waiting for "r"eadable or "w"ritable events, |
167 | which creates a watcher waiting for "r"eadable or "w"ritable events, |
148 | respectively. C<cb> is the callback to invoke each time the file handle |
168 | respectively. C<cb> is the callback to invoke each time the file handle |
149 | becomes ready. |
169 | becomes ready. |
150 | |
170 | |
151 | As long as the I/O watcher exists it will keep the file descriptor or a |
171 | Although the callback might get passed parameters, their value and |
152 | copy of it alive/open. |
172 | presence is undefined and you cannot rely on them. Portable AnyEvent |
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173 | callbacks cannot use arguments passed to I/O watcher callbacks. |
153 | |
174 | |
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175 | The I/O watcher might use the underlying file descriptor or a copy of it. |
154 | It is not allowed to close a file handle as long as any watcher is active |
176 | You must not close a file handle as long as any watcher is active on the |
155 | on the underlying file descriptor. |
177 | underlying file descriptor. |
156 | |
178 | |
157 | Some event loops issue spurious readyness notifications, so you should |
179 | Some event loops issue spurious readyness notifications, so you should |
158 | always use non-blocking calls when reading/writing from/to your file |
180 | always use non-blocking calls when reading/writing from/to your file |
159 | handles. |
181 | handles. |
160 | |
182 | |
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171 | |
193 | |
172 | You can create a time watcher by calling the C<< AnyEvent->timer >> |
194 | You can create a time watcher by calling the C<< AnyEvent->timer >> |
173 | method with the following mandatory arguments: |
195 | method with the following mandatory arguments: |
174 | |
196 | |
175 | C<after> specifies after how many seconds (fractional values are |
197 | C<after> specifies after how many seconds (fractional values are |
176 | supported) should the timer activate. C<cb> the callback to invoke in that |
198 | supported) the callback should be invoked. C<cb> is the callback to invoke |
177 | case. |
199 | in that case. |
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200 | |
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201 | Although the callback might get passed parameters, their value and |
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202 | presence is undefined and you cannot rely on them. Portable AnyEvent |
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203 | callbacks cannot use arguments passed to time watcher callbacks. |
178 | |
204 | |
179 | The timer callback will be invoked at most once: if you want a repeating |
205 | The timer callback will be invoked at most once: if you want a repeating |
180 | timer you have to create a new watcher (this is a limitation by both Tk |
206 | timer you have to create a new watcher (this is a limitation by both Tk |
181 | and Glib). |
207 | and Glib). |
182 | |
208 | |
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207 | |
233 | |
208 | There are two ways to handle timers: based on real time (relative, "fire |
234 | There are two ways to handle timers: based on real time (relative, "fire |
209 | in 10 seconds") and based on wallclock time (absolute, "fire at 12 |
235 | in 10 seconds") and based on wallclock time (absolute, "fire at 12 |
210 | o'clock"). |
236 | o'clock"). |
211 | |
237 | |
212 | While most event loops expect timers to specified in a relative way, they use |
238 | While most event loops expect timers to specified in a relative way, they |
213 | absolute time internally. This makes a difference when your clock "jumps", |
239 | use absolute time internally. This makes a difference when your clock |
214 | for example, when ntp decides to set your clock backwards from the wrong 2014-01-01 to |
240 | "jumps", for example, when ntp decides to set your clock backwards from |
215 | 2008-01-01, a watcher that you created to fire "after" a second might actually take |
241 | the wrong date of 2014-01-01 to 2008-01-01, a watcher that is supposed to |
216 | six years to finally fire. |
242 | fire "after" a second might actually take six years to finally fire. |
217 | |
243 | |
218 | AnyEvent cannot compensate for this. The only event loop that is conscious |
244 | AnyEvent cannot compensate for this. The only event loop that is conscious |
219 | about these issues is L<EV>, which offers both relative (ev_timer) and |
245 | about these issues is L<EV>, which offers both relative (ev_timer, based |
220 | absolute (ev_periodic) timers. |
246 | on true relative time) and absolute (ev_periodic, based on wallclock time) |
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247 | timers. |
221 | |
248 | |
222 | AnyEvent always prefers relative timers, if available, matching the |
249 | AnyEvent always prefers relative timers, if available, matching the |
223 | AnyEvent API. |
250 | AnyEvent API. |
224 | |
251 | |
225 | =head2 SIGNAL WATCHERS |
252 | =head2 SIGNAL WATCHERS |
226 | |
253 | |
227 | You can watch for signals using a signal watcher, C<signal> is the signal |
254 | You can watch for signals using a signal watcher, C<signal> is the signal |
228 | I<name> without any C<SIG> prefix, C<cb> is the Perl callback to |
255 | I<name> without any C<SIG> prefix, C<cb> is the Perl callback to |
229 | be invoked whenever a signal occurs. |
256 | be invoked whenever a signal occurs. |
230 | |
257 | |
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258 | Although the callback might get passed parameters, their value and |
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259 | presence is undefined and you cannot rely on them. Portable AnyEvent |
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260 | callbacks cannot use arguments passed to signal watcher callbacks. |
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261 | |
231 | Multiple signals occurances can be clumped together into one callback |
262 | Multiple signal occurances can be clumped together into one callback |
232 | invocation, and callback invocation will be synchronous. synchronous means |
263 | invocation, and callback invocation will be synchronous. synchronous means |
233 | that it might take a while until the signal gets handled by the process, |
264 | that it might take a while until the signal gets handled by the process, |
234 | but it is guarenteed not to interrupt any other callbacks. |
265 | but it is guarenteed not to interrupt any other callbacks. |
235 | |
266 | |
236 | The main advantage of using these watchers is that you can share a signal |
267 | The main advantage of using these watchers is that you can share a signal |
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249 | |
280 | |
250 | The child process is specified by the C<pid> argument (if set to C<0>, it |
281 | The child process is specified by the C<pid> argument (if set to C<0>, it |
251 | watches for any child process exit). The watcher will trigger as often |
282 | watches for any child process exit). The watcher will trigger as often |
252 | as status change for the child are received. This works by installing a |
283 | as status change for the child are received. This works by installing a |
253 | signal handler for C<SIGCHLD>. The callback will be called with the pid |
284 | signal handler for C<SIGCHLD>. The callback will be called with the pid |
254 | and exit status (as returned by waitpid). |
285 | and exit status (as returned by waitpid), so unlike other watcher types, |
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286 | you I<can> rely on child watcher callback arguments. |
255 | |
287 | |
256 | Example: wait for pid 1333 |
288 | There is a slight catch to child watchers, however: you usually start them |
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289 | I<after> the child process was created, and this means the process could |
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290 | have exited already (and no SIGCHLD will be sent anymore). |
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291 | |
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292 | Not all event models handle this correctly (POE doesn't), but even for |
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293 | event models that I<do> handle this correctly, they usually need to be |
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294 | loaded before the process exits (i.e. before you fork in the first place). |
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295 | |
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296 | This means you cannot create a child watcher as the very first thing in an |
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297 | AnyEvent program, you I<have> to create at least one watcher before you |
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298 | C<fork> the child (alternatively, you can call C<AnyEvent::detect>). |
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299 | |
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300 | Example: fork a process and wait for it |
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301 | |
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302 | my $done = AnyEvent->condvar; |
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303 | |
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304 | AnyEvent::detect; # force event module to be initialised |
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305 | |
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306 | my $pid = fork or exit 5; |
257 | |
307 | |
258 | my $w = AnyEvent->child ( |
308 | my $w = AnyEvent->child ( |
259 | pid => 1333, |
309 | pid => $pid, |
260 | cb => sub { |
310 | cb => sub { |
261 | my ($pid, $status) = @_; |
311 | my ($pid, $status) = @_; |
262 | warn "pid $pid exited with status $status"; |
312 | warn "pid $pid exited with status $status"; |
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313 | $done->broadcast; |
263 | }, |
314 | }, |
264 | ); |
315 | ); |
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316 | |
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317 | # do something else, then wait for process exit |
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318 | $done->wait; |
265 | |
319 | |
266 | =head2 CONDITION VARIABLES |
320 | =head2 CONDITION VARIABLES |
267 | |
321 | |
268 | Condition variables can be created by calling the C<< AnyEvent->condvar >> |
322 | Condition variables can be created by calling the C<< AnyEvent->condvar >> |
269 | method without any arguments. |
323 | method without any arguments. |
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357 | AnyEvent::Impl::CoroEV based on Coro::EV, best choice. |
411 | AnyEvent::Impl::CoroEV based on Coro::EV, best choice. |
358 | AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice. |
412 | AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice. |
359 | AnyEvent::Impl::EV based on EV (an interface to libev, best choice). |
413 | AnyEvent::Impl::EV based on EV (an interface to libev, best choice). |
360 | AnyEvent::Impl::Event based on Event, second best choice. |
414 | AnyEvent::Impl::Event based on Event, second best choice. |
361 | AnyEvent::Impl::Glib based on Glib, third-best choice. |
415 | AnyEvent::Impl::Glib based on Glib, third-best choice. |
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416 | AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable. |
362 | AnyEvent::Impl::Tk based on Tk, very bad choice. |
417 | AnyEvent::Impl::Tk based on Tk, very bad choice. |
363 | AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable. |
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364 | AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs). |
418 | AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs). |
365 | AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse. |
419 | AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse. |
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420 | AnyEvent::Impl::POE based on POE, not generic enough for full support. |
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421 | |
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422 | There is no support for WxWidgets, as WxWidgets has no support for |
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423 | watching file handles. However, you can use WxWidgets through the |
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424 | POE Adaptor, as POE has a Wx backend that simply polls 20 times per |
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425 | second, which was considered to be too horrible to even consider for |
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426 | AnyEvent. Likewise, other POE backends can be used by AnyEvent by using |
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427 | it's adaptor. |
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428 | |
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429 | AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when |
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430 | autodetecting them. |
366 | |
431 | |
367 | =item AnyEvent::detect |
432 | =item AnyEvent::detect |
368 | |
433 | |
369 | Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model |
434 | Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model |
370 | if necessary. You should only call this function right before you would |
435 | if necessary. You should only call this function right before you would |
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421 | no warnings; |
486 | no warnings; |
422 | use strict; |
487 | use strict; |
423 | |
488 | |
424 | use Carp; |
489 | use Carp; |
425 | |
490 | |
426 | our $VERSION = '3.12'; |
491 | our $VERSION = '3.3'; |
427 | our $MODEL; |
492 | our $MODEL; |
428 | |
493 | |
429 | our $AUTOLOAD; |
494 | our $AUTOLOAD; |
430 | our @ISA; |
495 | our @ISA; |
431 | |
496 | |
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438 | [Coro::Event:: => AnyEvent::Impl::CoroEvent::], |
503 | [Coro::Event:: => AnyEvent::Impl::CoroEvent::], |
439 | [EV:: => AnyEvent::Impl::EV::], |
504 | [EV:: => AnyEvent::Impl::EV::], |
440 | [Event:: => AnyEvent::Impl::Event::], |
505 | [Event:: => AnyEvent::Impl::Event::], |
441 | [Glib:: => AnyEvent::Impl::Glib::], |
506 | [Glib:: => AnyEvent::Impl::Glib::], |
442 | [Tk:: => AnyEvent::Impl::Tk::], |
507 | [Tk:: => AnyEvent::Impl::Tk::], |
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508 | [Wx:: => AnyEvent::Impl::POE::], |
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509 | [Prima:: => AnyEvent::Impl::POE::], |
443 | [AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::], |
510 | [AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::], |
444 | ); |
511 | # everything below here will not be autoprobed as the pureperl backend should work everywhere |
445 | my @models_detect = ( |
512 | [Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy |
446 | [Qt:: => AnyEvent::Impl::Qt::], # requires special main program |
513 | [Qt:: => AnyEvent::Impl::Qt::], # requires special main program |
447 | [Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy |
514 | [POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza |
448 | ); |
515 | ); |
449 | |
516 | |
450 | our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY); |
517 | our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY); |
451 | |
518 | |
452 | sub detect() { |
519 | sub detect() { |
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456 | if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) { |
523 | if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) { |
457 | my $model = "AnyEvent::Impl::$1"; |
524 | my $model = "AnyEvent::Impl::$1"; |
458 | if (eval "require $model") { |
525 | if (eval "require $model") { |
459 | $MODEL = $model; |
526 | $MODEL = $model; |
460 | warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1; |
527 | warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1; |
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528 | } else { |
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529 | warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose; |
461 | } |
530 | } |
462 | } |
531 | } |
463 | |
532 | |
464 | # check for already loaded models |
533 | # check for already loaded models |
465 | unless ($MODEL) { |
534 | unless ($MODEL) { |
466 | for (@REGISTRY, @models, @models_detect) { |
535 | for (@REGISTRY, @models) { |
467 | my ($package, $model) = @$_; |
536 | my ($package, $model) = @$_; |
468 | if (${"$package\::VERSION"} > 0) { |
537 | if (${"$package\::VERSION"} > 0) { |
469 | if (eval "require $model") { |
538 | if (eval "require $model") { |
470 | $MODEL = $model; |
539 | $MODEL = $model; |
471 | warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1; |
540 | warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1; |
… | |
… | |
658 | |
727 | |
659 | =over 4 |
728 | =over 4 |
660 | |
729 | |
661 | =item C<PERL_ANYEVENT_VERBOSE> |
730 | =item C<PERL_ANYEVENT_VERBOSE> |
662 | |
731 | |
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732 | By default, AnyEvent will be completely silent except in fatal |
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733 | conditions. You can set this environment variable to make AnyEvent more |
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734 | talkative. |
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735 | |
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736 | When set to C<1> or higher, causes AnyEvent to warn about unexpected |
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737 | conditions, such as not being able to load the event model specified by |
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738 | C<PERL_ANYEVENT_MODEL>. |
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739 | |
663 | When set to C<2> or higher, cause AnyEvent to report to STDERR which event |
740 | When set to C<2> or higher, cause AnyEvent to report to STDERR which event |
664 | model it chooses. |
741 | model it chooses. |
665 | |
742 | |
666 | =item C<PERL_ANYEVENT_MODEL> |
743 | =item C<PERL_ANYEVENT_MODEL> |
667 | |
744 | |
… | |
… | |
681 | |
758 | |
682 | =back |
759 | =back |
683 | |
760 | |
684 | =head1 EXAMPLE PROGRAM |
761 | =head1 EXAMPLE PROGRAM |
685 | |
762 | |
686 | The following program uses an IO watcher to read data from STDIN, a timer |
763 | The following program uses an I/O watcher to read data from STDIN, a timer |
687 | to display a message once per second, and a condition variable to quit the |
764 | to display a message once per second, and a condition variable to quit the |
688 | program when the user enters quit: |
765 | program when the user enters quit: |
689 | |
766 | |
690 | use AnyEvent; |
767 | use AnyEvent; |
691 | |
768 | |
… | |
… | |
835 | $quit->broadcast; |
912 | $quit->broadcast; |
836 | }); |
913 | }); |
837 | |
914 | |
838 | $quit->wait; |
915 | $quit->wait; |
839 | |
916 | |
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917 | |
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918 | =head1 BENCHMARKS |
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919 | |
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920 | To give you an idea of the performance and overheads that AnyEvent adds |
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921 | over the event loops themselves and to give you an impression of the speed |
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922 | of various event loops I prepared some benchmarks. |
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923 | |
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924 | =head2 BENCHMARKING ANYEVENT OVERHEAD |
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925 | |
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926 | Here is a benchmark of various supported event models used natively and |
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927 | through anyevent. The benchmark creates a lot of timers (with a zero |
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928 | timeout) and I/O watchers (watching STDOUT, a pty, to become writable, |
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929 | which it is), lets them fire exactly once and destroys them again. |
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930 | |
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931 | Source code for this benchmark is found as F<eg/bench> in the AnyEvent |
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932 | distribution. |
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933 | |
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934 | =head3 Explanation of the columns |
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935 | |
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936 | I<watcher> is the number of event watchers created/destroyed. Since |
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937 | different event models feature vastly different performances, each event |
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938 | loop was given a number of watchers so that overall runtime is acceptable |
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939 | and similar between tested event loop (and keep them from crashing): Glib |
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940 | would probably take thousands of years if asked to process the same number |
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941 | of watchers as EV in this benchmark. |
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942 | |
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943 | I<bytes> is the number of bytes (as measured by the resident set size, |
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944 | RSS) consumed by each watcher. This method of measuring captures both C |
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945 | and Perl-based overheads. |
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946 | |
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947 | I<create> is the time, in microseconds (millionths of seconds), that it |
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948 | takes to create a single watcher. The callback is a closure shared between |
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949 | all watchers, to avoid adding memory overhead. That means closure creation |
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950 | and memory usage is not included in the figures. |
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951 | |
|
|
952 | I<invoke> is the time, in microseconds, used to invoke a simple |
|
|
953 | callback. The callback simply counts down a Perl variable and after it was |
|
|
954 | invoked "watcher" times, it would C<< ->broadcast >> a condvar once to |
|
|
955 | signal the end of this phase. |
|
|
956 | |
|
|
957 | I<destroy> is the time, in microseconds, that it takes to destroy a single |
|
|
958 | watcher. |
|
|
959 | |
|
|
960 | =head3 Results |
|
|
961 | |
|
|
962 | name watchers bytes create invoke destroy comment |
|
|
963 | EV/EV 400000 244 0.56 0.46 0.31 EV native interface |
|
|
964 | EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers |
|
|
965 | CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal |
|
|
966 | Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation |
|
|
967 | Event/Event 16000 516 31.88 31.30 0.85 Event native interface |
|
|
968 | Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers |
|
|
969 | Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour |
|
|
970 | Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers |
|
|
971 | POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event |
|
|
972 | POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select |
|
|
973 | |
|
|
974 | =head3 Discussion |
|
|
975 | |
|
|
976 | The benchmark does I<not> measure scalability of the event loop very |
|
|
977 | well. For example, a select-based event loop (such as the pure perl one) |
|
|
978 | can never compete with an event loop that uses epoll when the number of |
|
|
979 | file descriptors grows high. In this benchmark, all events become ready at |
|
|
980 | the same time, so select/poll-based implementations get an unnatural speed |
|
|
981 | boost. |
|
|
982 | |
|
|
983 | Also, note that the number of watchers usually has a nonlinear effect on |
|
|
984 | overall speed, that is, creating twice as many watchers doesn't take twice |
|
|
985 | the time - usually it takes longer. This puts event loops tested with a |
|
|
986 | higher number of watchers at a disadvantage. |
|
|
987 | |
|
|
988 | To put the range of results into perspective, consider that on the |
|
|
989 | benchmark machine, handling an event takes roughly 1600 CPU cycles with |
|
|
990 | EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU |
|
|
991 | cycles with POE. |
|
|
992 | |
|
|
993 | C<EV> is the sole leader regarding speed and memory use, which are both |
|
|
994 | maximal/minimal, respectively. Even when going through AnyEvent, it uses |
|
|
995 | far less memory than any other event loop and is still faster than Event |
|
|
996 | natively. |
|
|
997 | |
|
|
998 | The pure perl implementation is hit in a few sweet spots (both the |
|
|
999 | constant timeout and the use of a single fd hit optimisations in the perl |
|
|
1000 | interpreter and the backend itself). Nevertheless this shows that it |
|
|
1001 | adds very little overhead in itself. Like any select-based backend its |
|
|
1002 | performance becomes really bad with lots of file descriptors (and few of |
|
|
1003 | them active), of course, but this was not subject of this benchmark. |
|
|
1004 | |
|
|
1005 | The C<Event> module has a relatively high setup and callback invocation |
|
|
1006 | cost, but overall scores in on the third place. |
|
|
1007 | |
|
|
1008 | C<Glib>'s memory usage is quite a bit higher, but it features a |
|
|
1009 | faster callback invocation and overall ends up in the same class as |
|
|
1010 | C<Event>. However, Glib scales extremely badly, doubling the number of |
|
|
1011 | watchers increases the processing time by more than a factor of four, |
|
|
1012 | making it completely unusable when using larger numbers of watchers |
|
|
1013 | (note that only a single file descriptor was used in the benchmark, so |
|
|
1014 | inefficiencies of C<poll> do not account for this). |
|
|
1015 | |
|
|
1016 | The C<Tk> adaptor works relatively well. The fact that it crashes with |
|
|
1017 | more than 2000 watchers is a big setback, however, as correctness takes |
|
|
1018 | precedence over speed. Nevertheless, its performance is surprising, as the |
|
|
1019 | file descriptor is dup()ed for each watcher. This shows that the dup() |
|
|
1020 | employed by some adaptors is not a big performance issue (it does incur a |
|
|
1021 | hidden memory cost inside the kernel which is not reflected in the figures |
|
|
1022 | above). |
|
|
1023 | |
|
|
1024 | C<POE>, regardless of underlying event loop (whether using its pure |
|
|
1025 | perl select-based backend or the Event module, the POE-EV backend |
|
|
1026 | couldn't be tested because it wasn't working) shows abysmal performance |
|
|
1027 | and memory usage: Watchers use almost 30 times as much memory as |
|
|
1028 | EV watchers, and 10 times as much memory as Event (the high memory |
|
|
1029 | requirements are caused by requiring a session for each watcher). Watcher |
|
|
1030 | invocation speed is almost 900 times slower than with AnyEvent's pure perl |
|
|
1031 | implementation. The design of the POE adaptor class in AnyEvent can not |
|
|
1032 | really account for this, as session creation overhead is small compared |
|
|
1033 | to execution of the state machine, which is coded pretty optimally within |
|
|
1034 | L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow. |
|
|
1035 | |
|
|
1036 | =head3 Summary |
|
|
1037 | |
|
|
1038 | =over 4 |
|
|
1039 | |
|
|
1040 | =item * Using EV through AnyEvent is faster than any other event loop |
|
|
1041 | (even when used without AnyEvent), but most event loops have acceptable |
|
|
1042 | performance with or without AnyEvent. |
|
|
1043 | |
|
|
1044 | =item * The overhead AnyEvent adds is usually much smaller than the overhead of |
|
|
1045 | the actual event loop, only with extremely fast event loops such as EV |
|
|
1046 | adds AnyEvent significant overhead. |
|
|
1047 | |
|
|
1048 | =item * You should avoid POE like the plague if you want performance or |
|
|
1049 | reasonable memory usage. |
|
|
1050 | |
|
|
1051 | =back |
|
|
1052 | |
|
|
1053 | =head2 BENCHMARKING THE LARGE SERVER CASE |
|
|
1054 | |
|
|
1055 | This benchmark atcually benchmarks the event loop itself. It works by |
|
|
1056 | creating a number of "servers": each server consists of a socketpair, a |
|
|
1057 | timeout watcher that gets reset on activity (but never fires), and an I/O |
|
|
1058 | watcher waiting for input on one side of the socket. Each time the socket |
|
|
1059 | watcher reads a byte it will write that byte to a random other "server". |
|
|
1060 | |
|
|
1061 | The effect is that there will be a lot of I/O watchers, only part of which |
|
|
1062 | are active at any one point (so there is a constant number of active |
|
|
1063 | fds for each loop iterstaion, but which fds these are is random). The |
|
|
1064 | timeout is reset each time something is read because that reflects how |
|
|
1065 | most timeouts work (and puts extra pressure on the event loops). |
|
|
1066 | |
|
|
1067 | In this benchmark, we use 10000 socketpairs (20000 sockets), of which 100 |
|
|
1068 | (1%) are active. This mirrors the activity of large servers with many |
|
|
1069 | connections, most of which are idle at any one point in time. |
|
|
1070 | |
|
|
1071 | Source code for this benchmark is found as F<eg/bench2> in the AnyEvent |
|
|
1072 | distribution. |
|
|
1073 | |
|
|
1074 | =head3 Explanation of the columns |
|
|
1075 | |
|
|
1076 | I<sockets> is the number of sockets, and twice the number of "servers" (as |
|
|
1077 | each server has a read and write socket end). |
|
|
1078 | |
|
|
1079 | I<create> is the time it takes to create a socketpair (which is |
|
|
1080 | nontrivial) and two watchers: an I/O watcher and a timeout watcher. |
|
|
1081 | |
|
|
1082 | I<request>, the most important value, is the time it takes to handle a |
|
|
1083 | single "request", that is, reading the token from the pipe and forwarding |
|
|
1084 | it to another server. This includes deleting the old timeout and creating |
|
|
1085 | a new one that moves the timeout into the future. |
|
|
1086 | |
|
|
1087 | =head3 Results |
|
|
1088 | |
|
|
1089 | name sockets create request |
|
|
1090 | EV 20000 69.01 11.16 |
|
|
1091 | Perl 20000 73.32 35.87 |
|
|
1092 | Event 20000 212.62 257.32 |
|
|
1093 | Glib 20000 651.16 1896.30 |
|
|
1094 | POE 20000 349.67 12317.24 uses POE::Loop::Event |
|
|
1095 | |
|
|
1096 | =head3 Discussion |
|
|
1097 | |
|
|
1098 | This benchmark I<does> measure scalability and overall performance of the |
|
|
1099 | particular event loop. |
|
|
1100 | |
|
|
1101 | EV is again fastest. Since it is using epoll on my system, the setup time |
|
|
1102 | is relatively high, though. |
|
|
1103 | |
|
|
1104 | Perl surprisingly comes second. It is much faster than the C-based event |
|
|
1105 | loops Event and Glib. |
|
|
1106 | |
|
|
1107 | Event suffers from high setup time as well (look at its code and you will |
|
|
1108 | understand why). Callback invocation also has a high overhead compared to |
|
|
1109 | the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event |
|
|
1110 | uses select or poll in basically all documented configurations. |
|
|
1111 | |
|
|
1112 | Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It |
|
|
1113 | clearly fails to perform with many filehandles or in busy servers. |
|
|
1114 | |
|
|
1115 | POE is still completely out of the picture, taking over 1000 times as long |
|
|
1116 | as EV, and over 100 times as long as the Perl implementation, even though |
|
|
1117 | it uses a C-based event loop in this case. |
|
|
1118 | |
|
|
1119 | =head3 Summary |
|
|
1120 | |
|
|
1121 | =over 4 |
|
|
1122 | |
|
|
1123 | =item * The pure perl implementation performs extremely well, considering |
|
|
1124 | that it uses select. |
|
|
1125 | |
|
|
1126 | =item * Avoid Glib or POE in large projects where performance matters. |
|
|
1127 | |
|
|
1128 | =back |
|
|
1129 | |
|
|
1130 | =head2 BENCHMARKING SMALL SERVERS |
|
|
1131 | |
|
|
1132 | While event loops should scale (and select-based ones do not...) even to |
|
|
1133 | large servers, most programs we (or I :) actually write have only a few |
|
|
1134 | I/O watchers. |
|
|
1135 | |
|
|
1136 | In this benchmark, I use the same benchmark program as in the large server |
|
|
1137 | case, but it uses only eight "servers", of which three are active at any |
|
|
1138 | one time. This should reflect performance for a small server relatively |
|
|
1139 | well. |
|
|
1140 | |
|
|
1141 | The columns are identical to the previous table. |
|
|
1142 | |
|
|
1143 | =head3 Results |
|
|
1144 | |
|
|
1145 | name sockets create request |
|
|
1146 | EV 16 20.00 6.54 |
|
|
1147 | Perl 16 25.75 12.62 |
|
|
1148 | Event 16 81.27 35.86 |
|
|
1149 | Glib 16 32.63 15.48 |
|
|
1150 | POE 16 261.87 276.28 uses POE::Loop::Event |
|
|
1151 | |
|
|
1152 | =head3 Discussion |
|
|
1153 | |
|
|
1154 | The benchmark tries to test the performance of a typical small |
|
|
1155 | server. While knowing how various event loops perform is interesting, keep |
|
|
1156 | in mind that their overhead in this case is usually not as important, due |
|
|
1157 | to the small absolute number of watchers (that is, you need efficiency and |
|
|
1158 | speed most when you have lots of watchers, not when you only have a few of |
|
|
1159 | them). |
|
|
1160 | |
|
|
1161 | EV is again fastest. |
|
|
1162 | |
|
|
1163 | The C-based event loops Event and Glib come in second this time, as the |
|
|
1164 | overhead of running an iteration is much smaller in C than in Perl (little |
|
|
1165 | code to execute in the inner loop, and perl's function calling overhead is |
|
|
1166 | high, and updating all the data structures is costly). |
|
|
1167 | |
|
|
1168 | The pure perl event loop is much slower, but still competitive. |
|
|
1169 | |
|
|
1170 | POE also performs much better in this case, but is is still far behind the |
|
|
1171 | others. |
|
|
1172 | |
|
|
1173 | =head3 Summary |
|
|
1174 | |
|
|
1175 | =over 4 |
|
|
1176 | |
|
|
1177 | =item * C-based event loops perform very well with small number of |
|
|
1178 | watchers, as the management overhead dominates. |
|
|
1179 | |
|
|
1180 | =back |
|
|
1181 | |
|
|
1182 | |
840 | =head1 FORK |
1183 | =head1 FORK |
841 | |
1184 | |
842 | Most event libraries are not fork-safe. The ones who are usually are |
1185 | Most event libraries are not fork-safe. The ones who are usually are |
843 | because they are so inefficient. Only L<EV> is fully fork-aware. |
1186 | because they are so inefficient. Only L<EV> is fully fork-aware. |
844 | |
1187 | |
845 | If you have to fork, you must either do so I<before> creating your first |
1188 | If you have to fork, you must either do so I<before> creating your first |
846 | watcher OR you must not use AnyEvent at all in the child. |
1189 | watcher OR you must not use AnyEvent at all in the child. |
|
|
1190 | |
847 | |
1191 | |
848 | =head1 SECURITY CONSIDERATIONS |
1192 | =head1 SECURITY CONSIDERATIONS |
849 | |
1193 | |
850 | AnyEvent can be forced to load any event model via |
1194 | AnyEvent can be forced to load any event model via |
851 | $ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to |
1195 | $ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to |
… | |
… | |
859 | |
1203 | |
860 | BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} } |
1204 | BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} } |
861 | |
1205 | |
862 | use AnyEvent; |
1206 | use AnyEvent; |
863 | |
1207 | |
|
|
1208 | |
864 | =head1 SEE ALSO |
1209 | =head1 SEE ALSO |
865 | |
1210 | |
866 | Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>, |
1211 | Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>, |
867 | L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>, |
1212 | L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>, |
868 | L<Event::Lib>, L<Qt>. |
1213 | L<Event::Lib>, L<Qt>, L<POE>. |
869 | |
1214 | |
870 | Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>, |
1215 | Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>, |
871 | L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>, |
1216 | L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>, |
872 | L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>, |
1217 | L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>, |
873 | L<AnyEvent::Impl::Qt>. |
1218 | L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>. |
874 | |
1219 | |
875 | Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>. |
1220 | Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>. |
|
|
1221 | |
876 | |
1222 | |
877 | =head1 AUTHOR |
1223 | =head1 AUTHOR |
878 | |
1224 | |
879 | Marc Lehmann <schmorp@schmorp.de> |
1225 | Marc Lehmann <schmorp@schmorp.de> |
880 | http://home.schmorp.de/ |
1226 | http://home.schmorp.de/ |