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1=head1 NAME 1=head1 NAME
2 2
3AnyEvent - provide framework for multiple event loops 3AnyEvent - provide framework for multiple event loops
4 4
5EV, Event, Coro::EV, Coro::Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event loops 5EV, Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event loops
6 6
7=head1 SYNOPSIS 7=head1 SYNOPSIS
8 8
9 use AnyEvent; 9 use AnyEvent;
10 10
15 my $w = AnyEvent->timer (after => $seconds, cb => sub { 15 my $w = AnyEvent->timer (after => $seconds, cb => sub {
16 ... 16 ...
17 }); 17 });
18 18
19 my $w = AnyEvent->condvar; # stores whether a condition was flagged 19 my $w = AnyEvent->condvar; # stores whether a condition was flagged
20 $w->send; # wake up current and all future recv's
20 $w->wait; # enters "main loop" till $condvar gets ->broadcast 21 $w->recv; # enters "main loop" till $condvar gets ->send
21 $w->broadcast; # wake up current and all future wait's 22
23=head1 INTRODUCTION/TUTORIAL
24
25This manpage is mainly a reference manual. If you are interested
26in a tutorial or some gentle introduction, have a look at the
27L<AnyEvent::Intro> manpage.
22 28
23=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT) 29=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
24 30
25Glib, POE, IO::Async, Event... CPAN offers event models by the dozen 31Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
26nowadays. So what is different about AnyEvent? 32nowadays. So what is different about AnyEvent?
48isn't itself. What's worse, all the potential users of your module are 54isn't itself. What's worse, all the potential users of your module are
49I<also> forced to use the same event loop you use. 55I<also> forced to use the same event loop you use.
50 56
51AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works 57AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
52fine. AnyEvent + Tk works fine etc. etc. but none of these work together 58fine. AnyEvent + Tk works fine etc. etc. but none of these work together
53with the rest: POE + IO::Async? no go. Tk + Event? no go. Again: if 59with the rest: POE + IO::Async? No go. Tk + Event? No go. Again: if
54your module uses one of those, every user of your module has to use it, 60your module uses one of those, every user of your module has to use it,
55too. But if your module uses AnyEvent, it works transparently with all 61too. But if your module uses AnyEvent, it works transparently with all
56event models it supports (including stuff like POE and IO::Async, as long 62event models it supports (including stuff like POE and IO::Async, as long
57as those use one of the supported event loops. It is trivial to add new 63as those use one of the supported event loops. It is trivial to add new
58event loops to AnyEvent, too, so it is future-proof). 64event loops to AnyEvent, too, so it is future-proof).
59 65
60In addition to being free of having to use I<the one and only true event 66In addition to being free of having to use I<the one and only true event
61model>, AnyEvent also is free of bloat and policy: with POE or similar 67model>, AnyEvent also is free of bloat and policy: with POE or similar
62modules, you get an enourmous amount of code and strict rules you have to 68modules, you get an enormous amount of code and strict rules you have to
63follow. AnyEvent, on the other hand, is lean and up to the point, by only 69follow. AnyEvent, on the other hand, is lean and up to the point, by only
64offering the functionality that is necessary, in as thin as a wrapper as 70offering the functionality that is necessary, in as thin as a wrapper as
65technically possible. 71technically possible.
66 72
73Of course, AnyEvent comes with a big (and fully optional!) toolbox
74of useful functionality, such as an asynchronous DNS resolver, 100%
75non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms
76such as Windows) and lots of real-world knowledge and workarounds for
77platform bugs and differences.
78
67Of course, if you want lots of policy (this can arguably be somewhat 79Now, if you I<do want> lots of policy (this can arguably be somewhat
68useful) and you want to force your users to use the one and only event 80useful) and you want to force your users to use the one and only event
69model, you should I<not> use this module. 81model, you should I<not> use this module.
70
71 82
72=head1 DESCRIPTION 83=head1 DESCRIPTION
73 84
74L<AnyEvent> provides an identical interface to multiple event loops. This 85L<AnyEvent> provides an identical interface to multiple event loops. This
75allows module authors to utilise an event loop without forcing module 86allows module authors to utilise an event loop without forcing module
79The interface itself is vaguely similar, but not identical to the L<Event> 90The interface itself is vaguely similar, but not identical to the L<Event>
80module. 91module.
81 92
82During the first call of any watcher-creation method, the module tries 93During the first call of any watcher-creation method, the module tries
83to detect the currently loaded event loop by probing whether one of the 94to detect the currently loaded event loop by probing whether one of the
84following modules is already loaded: L<Coro::EV>, L<Coro::Event>, L<EV>, 95following modules is already loaded: L<EV>,
85L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>, 96L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>,
86L<POE>. The first one found is used. If none are found, the module tries 97L<POE>. The first one found is used. If none are found, the module tries
87to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl 98to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl
88adaptor should always succeed) in the order given. The first one that can 99adaptor should always succeed) in the order given. The first one that can
89be successfully loaded will be used. If, after this, still none could be 100be successfully loaded will be used. If, after this, still none could be
103starts using it, all bets are off. Maybe you should tell their authors to 114starts using it, all bets are off. Maybe you should tell their authors to
104use AnyEvent so their modules work together with others seamlessly... 115use AnyEvent so their modules work together with others seamlessly...
105 116
106The pure-perl implementation of AnyEvent is called 117The pure-perl implementation of AnyEvent is called
107C<AnyEvent::Impl::Perl>. Like other event modules you can load it 118C<AnyEvent::Impl::Perl>. Like other event modules you can load it
108explicitly. 119explicitly and enjoy the high availability of that event loop :)
109 120
110=head1 WATCHERS 121=head1 WATCHERS
111 122
112AnyEvent has the central concept of a I<watcher>, which is an object that 123AnyEvent has the central concept of a I<watcher>, which is an object that
113stores relevant data for each kind of event you are waiting for, such as 124stores relevant data for each kind of event you are waiting for, such as
114the callback to call, the filehandle to watch, etc. 125the callback to call, the file handle to watch, etc.
115 126
116These watchers are normal Perl objects with normal Perl lifetime. After 127These watchers are normal Perl objects with normal Perl lifetime. After
117creating a watcher it will immediately "watch" for events and invoke the 128creating a watcher it will immediately "watch" for events and invoke the
118callback when the event occurs (of course, only when the event model 129callback when the event occurs (of course, only when the event model
119is in control). 130is in control).
127Many watchers either are used with "recursion" (repeating timers for 138Many watchers either are used with "recursion" (repeating timers for
128example), or need to refer to their watcher object in other ways. 139example), or need to refer to their watcher object in other ways.
129 140
130An any way to achieve that is this pattern: 141An any way to achieve that is this pattern:
131 142
132 my $w; $w = AnyEvent->type (arg => value ..., cb => sub { 143 my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
133 # you can use $w here, for example to undef it 144 # you can use $w here, for example to undef it
134 undef $w; 145 undef $w;
135 }); 146 });
136 147
137Note that C<my $w; $w => combination. This is necessary because in Perl, 148Note that C<my $w; $w => combination. This is necessary because in Perl,
138my variables are only visible after the statement in which they are 149my variables are only visible after the statement in which they are
139declared. 150declared.
140 151
159 170
160Some event loops issue spurious readyness notifications, so you should 171Some event loops issue spurious readyness notifications, so you should
161always use non-blocking calls when reading/writing from/to your file 172always use non-blocking calls when reading/writing from/to your file
162handles. 173handles.
163 174
164Example:
165
166 # wait for readability of STDIN, then read a line and disable the watcher 175Example: wait for readability of STDIN, then read a line and disable the
176watcher.
177
167 my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub { 178 my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
168 chomp (my $input = <STDIN>); 179 chomp (my $input = <STDIN>);
169 warn "read: $input\n"; 180 warn "read: $input\n";
170 undef $w; 181 undef $w;
171 }); 182 });
181 192
182Although the callback might get passed parameters, their value and 193Although the callback might get passed parameters, their value and
183presence is undefined and you cannot rely on them. Portable AnyEvent 194presence is undefined and you cannot rely on them. Portable AnyEvent
184callbacks cannot use arguments passed to time watcher callbacks. 195callbacks cannot use arguments passed to time watcher callbacks.
185 196
186The timer callback will be invoked at most once: if you want a repeating 197The callback will normally be invoked once only. If you specify another
187timer you have to create a new watcher (this is a limitation by both Tk 198parameter, C<interval>, as a positive number, then the callback will be
188and Glib). 199invoked regularly at that interval (in fractional seconds) after the first
200invocation.
189 201
190Example: 202The callback will be rescheduled before invoking the callback, but no
203attempt is done to avoid timer drift in most backends, so the interval is
204only approximate.
191 205
192 # fire an event after 7.7 seconds 206Example: fire an event after 7.7 seconds.
207
193 my $w = AnyEvent->timer (after => 7.7, cb => sub { 208 my $w = AnyEvent->timer (after => 7.7, cb => sub {
194 warn "timeout\n"; 209 warn "timeout\n";
195 }); 210 });
196 211
197 # to cancel the timer: 212 # to cancel the timer:
198 undef $w; 213 undef $w;
199 214
200Example 2:
201
202 # fire an event after 0.5 seconds, then roughly every second 215Example 2: fire an event after 0.5 seconds, then roughly every second.
203 my $w;
204 216
205 my $cb = sub {
206 # cancel the old timer while creating a new one
207 $w = AnyEvent->timer (after => 1, cb => $cb); 217 my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
218 warn "timeout\n";
208 }; 219 };
209
210 # start the "loop" by creating the first watcher
211 $w = AnyEvent->timer (after => 0.5, cb => $cb);
212 220
213=head3 TIMING ISSUES 221=head3 TIMING ISSUES
214 222
215There are two ways to handle timers: based on real time (relative, "fire 223There are two ways to handle timers: based on real time (relative, "fire
216in 10 seconds") and based on wallclock time (absolute, "fire at 12 224in 10 seconds") and based on wallclock time (absolute, "fire at 12
228timers. 236timers.
229 237
230AnyEvent always prefers relative timers, if available, matching the 238AnyEvent always prefers relative timers, if available, matching the
231AnyEvent API. 239AnyEvent API.
232 240
241AnyEvent has two additional methods that return the "current time":
242
243=over 4
244
245=item AnyEvent->time
246
247This returns the "current wallclock time" as a fractional number of
248seconds since the Epoch (the same thing as C<time> or C<Time::HiRes::time>
249return, and the result is guaranteed to be compatible with those).
250
251It progresses independently of any event loop processing, i.e. each call
252will check the system clock, which usually gets updated frequently.
253
254=item AnyEvent->now
255
256This also returns the "current wallclock time", but unlike C<time>, above,
257this value might change only once per event loop iteration, depending on
258the event loop (most return the same time as C<time>, above). This is the
259time that AnyEvent's timers get scheduled against.
260
261I<In almost all cases (in all cases if you don't care), this is the
262function to call when you want to know the current time.>
263
264This function is also often faster then C<< AnyEvent->time >>, and
265thus the preferred method if you want some timestamp (for example,
266L<AnyEvent::Handle> uses this to update it's activity timeouts).
267
268The rest of this section is only of relevance if you try to be very exact
269with your timing, you can skip it without bad conscience.
270
271For a practical example of when these times differ, consider L<Event::Lib>
272and L<EV> and the following set-up:
273
274The event loop is running and has just invoked one of your callback at
275time=500 (assume no other callbacks delay processing). In your callback,
276you wait a second by executing C<sleep 1> (blocking the process for a
277second) and then (at time=501) you create a relative timer that fires
278after three seconds.
279
280With L<Event::Lib>, C<< AnyEvent->time >> and C<< AnyEvent->now >> will
281both return C<501>, because that is the current time, and the timer will
282be scheduled to fire at time=504 (C<501> + C<3>).
283
284With L<EV>, C<< AnyEvent->time >> returns C<501> (as that is the current
285time), but C<< AnyEvent->now >> returns C<500>, as that is the time the
286last event processing phase started. With L<EV>, your timer gets scheduled
287to run at time=503 (C<500> + C<3>).
288
289In one sense, L<Event::Lib> is more exact, as it uses the current time
290regardless of any delays introduced by event processing. However, most
291callbacks do not expect large delays in processing, so this causes a
292higher drift (and a lot more system calls to get the current time).
293
294In another sense, L<EV> is more exact, as your timer will be scheduled at
295the same time, regardless of how long event processing actually took.
296
297In either case, if you care (and in most cases, you don't), then you
298can get whatever behaviour you want with any event loop, by taking the
299difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
300account.
301
302=back
303
233=head2 SIGNAL WATCHERS 304=head2 SIGNAL WATCHERS
234 305
235You can watch for signals using a signal watcher, C<signal> is the signal 306You can watch for signals using a signal watcher, C<signal> is the signal
236I<name> without any C<SIG> prefix, C<cb> is the Perl callback to 307I<name> without any C<SIG> prefix, C<cb> is the Perl callback to
237be invoked whenever a signal occurs. 308be invoked whenever a signal occurs.
238 309
239Although the callback might get passed parameters, their value and 310Although the callback might get passed parameters, their value and
240presence is undefined and you cannot rely on them. Portable AnyEvent 311presence is undefined and you cannot rely on them. Portable AnyEvent
241callbacks cannot use arguments passed to signal watcher callbacks. 312callbacks cannot use arguments passed to signal watcher callbacks.
242 313
243Multiple signal occurances can be clumped together into one callback 314Multiple signal occurrences can be clumped together into one callback
244invocation, and callback invocation will be synchronous. synchronous means 315invocation, and callback invocation will be synchronous. Synchronous means
245that it might take a while until the signal gets handled by the process, 316that it might take a while until the signal gets handled by the process,
246but it is guarenteed not to interrupt any other callbacks. 317but it is guaranteed not to interrupt any other callbacks.
247 318
248The main advantage of using these watchers is that you can share a signal 319The main advantage of using these watchers is that you can share a signal
249between multiple watchers. 320between multiple watchers.
250 321
251This watcher might use C<%SIG>, so programs overwriting those signals 322This watcher might use C<%SIG>, so programs overwriting those signals
278AnyEvent program, you I<have> to create at least one watcher before you 349AnyEvent program, you I<have> to create at least one watcher before you
279C<fork> the child (alternatively, you can call C<AnyEvent::detect>). 350C<fork> the child (alternatively, you can call C<AnyEvent::detect>).
280 351
281Example: fork a process and wait for it 352Example: fork a process and wait for it
282 353
283 my $done = AnyEvent->condvar; 354 my $done = AnyEvent->condvar;
284 355
285 AnyEvent::detect; # force event module to be initialised
286
287 my $pid = fork or exit 5; 356 my $pid = fork or exit 5;
288 357
289 my $w = AnyEvent->child ( 358 my $w = AnyEvent->child (
290 pid => $pid, 359 pid => $pid,
291 cb => sub { 360 cb => sub {
292 my ($pid, $status) = @_; 361 my ($pid, $status) = @_;
293 warn "pid $pid exited with status $status"; 362 warn "pid $pid exited with status $status";
294 $done->broadcast; 363 $done->send;
295 }, 364 },
296 ); 365 );
297 366
298 # do something else, then wait for process exit 367 # do something else, then wait for process exit
299 $done->wait; 368 $done->recv;
300 369
301=head2 CONDITION VARIABLES 370=head2 CONDITION VARIABLES
302 371
372If you are familiar with some event loops you will know that all of them
373require you to run some blocking "loop", "run" or similar function that
374will actively watch for new events and call your callbacks.
375
376AnyEvent is different, it expects somebody else to run the event loop and
377will only block when necessary (usually when told by the user).
378
379The instrument to do that is called a "condition variable", so called
380because they represent a condition that must become true.
381
303Condition variables can be created by calling the C<< AnyEvent->condvar >> 382Condition variables can be created by calling the C<< AnyEvent->condvar
304method without any arguments. 383>> method, usually without arguments. The only argument pair allowed is
384C<cb>, which specifies a callback to be called when the condition variable
385becomes true.
305 386
306A condition variable waits for a condition - precisely that the C<< 387After creation, the condition variable is "false" until it becomes "true"
307->broadcast >> method has been called. 388by calling the C<send> method (or calling the condition variable as if it
389were a callback, read about the caveats in the description for the C<<
390->send >> method).
308 391
309They are very useful to signal that a condition has been fulfilled, for 392Condition variables are similar to callbacks, except that you can
393optionally wait for them. They can also be called merge points - points
394in time where multiple outstanding events have been processed. And yet
395another way to call them is transactions - each condition variable can be
396used to represent a transaction, which finishes at some point and delivers
397a result.
398
399Condition variables are very useful to signal that something has finished,
310example, if you write a module that does asynchronous http requests, 400for example, if you write a module that does asynchronous http requests,
311then a condition variable would be the ideal candidate to signal the 401then a condition variable would be the ideal candidate to signal the
312availability of results. 402availability of results. The user can either act when the callback is
403called or can synchronously C<< ->recv >> for the results.
313 404
314You can also use condition variables to block your main program until 405You can also use them to simulate traditional event loops - for example,
315an event occurs - for example, you could C<< ->wait >> in your main 406you can block your main program until an event occurs - for example, you
316program until the user clicks the Quit button in your app, which would C<< 407could C<< ->recv >> in your main program until the user clicks the Quit
317->broadcast >> the "quit" event. 408button of your app, which would C<< ->send >> the "quit" event.
318 409
319Note that condition variables recurse into the event loop - if you have 410Note that condition variables recurse into the event loop - if you have
320two pirces of code that call C<< ->wait >> in a round-robbin fashion, you 411two pieces of code that call C<< ->recv >> in a round-robin fashion, you
321lose. Therefore, condition variables are good to export to your caller, but 412lose. Therefore, condition variables are good to export to your caller, but
322you should avoid making a blocking wait yourself, at least in callbacks, 413you should avoid making a blocking wait yourself, at least in callbacks,
323as this asks for trouble. 414as this asks for trouble.
324 415
325This object has two methods: 416Condition variables are represented by hash refs in perl, and the keys
417used by AnyEvent itself are all named C<_ae_XXX> to make subclassing
418easy (it is often useful to build your own transaction class on top of
419AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call
420it's C<new> method in your own C<new> method.
421
422There are two "sides" to a condition variable - the "producer side" which
423eventually calls C<< -> send >>, and the "consumer side", which waits
424for the send to occur.
425
426Example: wait for a timer.
427
428 # wait till the result is ready
429 my $result_ready = AnyEvent->condvar;
430
431 # do something such as adding a timer
432 # or socket watcher the calls $result_ready->send
433 # when the "result" is ready.
434 # in this case, we simply use a timer:
435 my $w = AnyEvent->timer (
436 after => 1,
437 cb => sub { $result_ready->send },
438 );
439
440 # this "blocks" (while handling events) till the callback
441 # calls send
442 $result_ready->recv;
443
444Example: wait for a timer, but take advantage of the fact that
445condition variables are also code references.
446
447 my $done = AnyEvent->condvar;
448 my $delay = AnyEvent->timer (after => 5, cb => $done);
449 $done->recv;
450
451=head3 METHODS FOR PRODUCERS
452
453These methods should only be used by the producing side, i.e. the
454code/module that eventually sends the signal. Note that it is also
455the producer side which creates the condvar in most cases, but it isn't
456uncommon for the consumer to create it as well.
326 457
327=over 4 458=over 4
328 459
460=item $cv->send (...)
461
462Flag the condition as ready - a running C<< ->recv >> and all further
463calls to C<recv> will (eventually) return after this method has been
464called. If nobody is waiting the send will be remembered.
465
466If a callback has been set on the condition variable, it is called
467immediately from within send.
468
469Any arguments passed to the C<send> call will be returned by all
470future C<< ->recv >> calls.
471
472Condition variables are overloaded so one can call them directly
473(as a code reference). Calling them directly is the same as calling
474C<send>. Note, however, that many C-based event loops do not handle
475overloading, so as tempting as it may be, passing a condition variable
476instead of a callback does not work. Both the pure perl and EV loops
477support overloading, however, as well as all functions that use perl to
478invoke a callback (as in L<AnyEvent::Socket> and L<AnyEvent::DNS> for
479example).
480
481=item $cv->croak ($error)
482
483Similar to send, but causes all call's to C<< ->recv >> to invoke
484C<Carp::croak> with the given error message/object/scalar.
485
486This can be used to signal any errors to the condition variable
487user/consumer.
488
489=item $cv->begin ([group callback])
490
329=item $cv->wait 491=item $cv->end
330 492
331Wait (blocking if necessary) until the C<< ->broadcast >> method has been 493These two methods are EXPERIMENTAL and MIGHT CHANGE.
494
495These two methods can be used to combine many transactions/events into
496one. For example, a function that pings many hosts in parallel might want
497to use a condition variable for the whole process.
498
499Every call to C<< ->begin >> will increment a counter, and every call to
500C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
501>>, the (last) callback passed to C<begin> will be executed. That callback
502is I<supposed> to call C<< ->send >>, but that is not required. If no
503callback was set, C<send> will be called without any arguments.
504
505Let's clarify this with the ping example:
506
507 my $cv = AnyEvent->condvar;
508
509 my %result;
510 $cv->begin (sub { $cv->send (\%result) });
511
512 for my $host (@list_of_hosts) {
513 $cv->begin;
514 ping_host_then_call_callback $host, sub {
515 $result{$host} = ...;
516 $cv->end;
517 };
518 }
519
520 $cv->end;
521
522This code fragment supposedly pings a number of hosts and calls
523C<send> after results for all then have have been gathered - in any
524order. To achieve this, the code issues a call to C<begin> when it starts
525each ping request and calls C<end> when it has received some result for
526it. Since C<begin> and C<end> only maintain a counter, the order in which
527results arrive is not relevant.
528
529There is an additional bracketing call to C<begin> and C<end> outside the
530loop, which serves two important purposes: first, it sets the callback
531to be called once the counter reaches C<0>, and second, it ensures that
532C<send> is called even when C<no> hosts are being pinged (the loop
533doesn't execute once).
534
535This is the general pattern when you "fan out" into multiple subrequests:
536use an outer C<begin>/C<end> pair to set the callback and ensure C<end>
537is called at least once, and then, for each subrequest you start, call
538C<begin> and for each subrequest you finish, call C<end>.
539
540=back
541
542=head3 METHODS FOR CONSUMERS
543
544These methods should only be used by the consuming side, i.e. the
545code awaits the condition.
546
547=over 4
548
549=item $cv->recv
550
551Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
332called on c<$cv>, while servicing other watchers normally. 552>> methods have been called on c<$cv>, while servicing other watchers
553normally.
333 554
334You can only wait once on a condition - additional calls will return 555You can only wait once on a condition - additional calls are valid but
335immediately. 556will return immediately.
557
558If an error condition has been set by calling C<< ->croak >>, then this
559function will call C<croak>.
560
561In list context, all parameters passed to C<send> will be returned,
562in scalar context only the first one will be returned.
336 563
337Not all event models support a blocking wait - some die in that case 564Not all event models support a blocking wait - some die in that case
338(programs might want to do that to stay interactive), so I<if you are 565(programs might want to do that to stay interactive), so I<if you are
339using this from a module, never require a blocking wait>, but let the 566using this from a module, never require a blocking wait>, but let the
340caller decide whether the call will block or not (for example, by coupling 567caller decide whether the call will block or not (for example, by coupling
341condition variables with some kind of request results and supporting 568condition variables with some kind of request results and supporting
342callbacks so the caller knows that getting the result will not block, 569callbacks so the caller knows that getting the result will not block,
343while still suppporting blocking waits if the caller so desires). 570while still supporting blocking waits if the caller so desires).
344 571
345Another reason I<never> to C<< ->wait >> in a module is that you cannot 572Another reason I<never> to C<< ->recv >> in a module is that you cannot
346sensibly have two C<< ->wait >>'s in parallel, as that would require 573sensibly have two C<< ->recv >>'s in parallel, as that would require
347multiple interpreters or coroutines/threads, none of which C<AnyEvent> 574multiple interpreters or coroutines/threads, none of which C<AnyEvent>
348can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and 575can supply.
349L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
350from different coroutines, however).
351 576
352=item $cv->broadcast 577The L<Coro> module, however, I<can> and I<does> supply coroutines and, in
578fact, L<Coro::AnyEvent> replaces AnyEvent's condvars by coroutine-safe
579versions and also integrates coroutines into AnyEvent, making blocking
580C<< ->recv >> calls perfectly safe as long as they are done from another
581coroutine (one that doesn't run the event loop).
353 582
354Flag the condition as ready - a running C<< ->wait >> and all further 583You can ensure that C<< -recv >> never blocks by setting a callback and
355calls to C<wait> will (eventually) return after this method has been 584only calling C<< ->recv >> from within that callback (or at a later
356called. If nobody is waiting the broadcast will be remembered.. 585time). This will work even when the event loop does not support blocking
586waits otherwise.
587
588=item $bool = $cv->ready
589
590Returns true when the condition is "true", i.e. whether C<send> or
591C<croak> have been called.
592
593=item $cb = $cv->cb ([new callback])
594
595This is a mutator function that returns the callback set and optionally
596replaces it before doing so.
597
598The callback will be called when the condition becomes "true", i.e. when
599C<send> or C<croak> are called, with the only argument being the condition
600variable itself. Calling C<recv> inside the callback or at any later time
601is guaranteed not to block.
357 602
358=back 603=back
359
360Example:
361
362 # wait till the result is ready
363 my $result_ready = AnyEvent->condvar;
364
365 # do something such as adding a timer
366 # or socket watcher the calls $result_ready->broadcast
367 # when the "result" is ready.
368 # in this case, we simply use a timer:
369 my $w = AnyEvent->timer (
370 after => 1,
371 cb => sub { $result_ready->broadcast },
372 );
373
374 # this "blocks" (while handling events) till the watcher
375 # calls broadcast
376 $result_ready->wait;
377 604
378=head1 GLOBAL VARIABLES AND FUNCTIONS 605=head1 GLOBAL VARIABLES AND FUNCTIONS
379 606
380=over 4 607=over 4
381 608
387C<AnyEvent::Impl:xxx> modules, but can be any other class in the case 614C<AnyEvent::Impl:xxx> modules, but can be any other class in the case
388AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>). 615AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).
389 616
390The known classes so far are: 617The known classes so far are:
391 618
392 AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
393 AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
394 AnyEvent::Impl::EV based on EV (an interface to libev, best choice). 619 AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
395 AnyEvent::Impl::Event based on Event, second best choice. 620 AnyEvent::Impl::Event based on Event, second best choice.
621 AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
396 AnyEvent::Impl::Glib based on Glib, third-best choice. 622 AnyEvent::Impl::Glib based on Glib, third-best choice.
397 AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
398 AnyEvent::Impl::Tk based on Tk, very bad choice. 623 AnyEvent::Impl::Tk based on Tk, very bad choice.
399 AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs). 624 AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
400 AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse. 625 AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
401 AnyEvent::Impl::POE based on POE, not generic enough for full support. 626 AnyEvent::Impl::POE based on POE, not generic enough for full support.
402 627
415Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model 640Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
416if necessary. You should only call this function right before you would 641if necessary. You should only call this function right before you would
417have created an AnyEvent watcher anyway, that is, as late as possible at 642have created an AnyEvent watcher anyway, that is, as late as possible at
418runtime. 643runtime.
419 644
645=item $guard = AnyEvent::post_detect { BLOCK }
646
647Arranges for the code block to be executed as soon as the event model is
648autodetected (or immediately if this has already happened).
649
650If called in scalar or list context, then it creates and returns an object
651that automatically removes the callback again when it is destroyed. See
652L<Coro::BDB> for a case where this is useful.
653
654=item @AnyEvent::post_detect
655
656If there are any code references in this array (you can C<push> to it
657before or after loading AnyEvent), then they will called directly after
658the event loop has been chosen.
659
660You should check C<$AnyEvent::MODEL> before adding to this array, though:
661if it contains a true value then the event loop has already been detected,
662and the array will be ignored.
663
664Best use C<AnyEvent::post_detect { BLOCK }> instead.
665
420=back 666=back
421 667
422=head1 WHAT TO DO IN A MODULE 668=head1 WHAT TO DO IN A MODULE
423 669
424As a module author, you should C<use AnyEvent> and call AnyEvent methods 670As a module author, you should C<use AnyEvent> and call AnyEvent methods
427Be careful when you create watchers in the module body - AnyEvent will 673Be careful when you create watchers in the module body - AnyEvent will
428decide which event module to use as soon as the first method is called, so 674decide which event module to use as soon as the first method is called, so
429by calling AnyEvent in your module body you force the user of your module 675by calling AnyEvent in your module body you force the user of your module
430to load the event module first. 676to load the event module first.
431 677
432Never call C<< ->wait >> on a condition variable unless you I<know> that 678Never call C<< ->recv >> on a condition variable unless you I<know> that
433the C<< ->broadcast >> method has been called on it already. This is 679the C<< ->send >> method has been called on it already. This is
434because it will stall the whole program, and the whole point of using 680because it will stall the whole program, and the whole point of using
435events is to stay interactive. 681events is to stay interactive.
436 682
437It is fine, however, to call C<< ->wait >> when the user of your module 683It is fine, however, to call C<< ->recv >> when the user of your module
438requests it (i.e. if you create a http request object ad have a method 684requests it (i.e. if you create a http request object ad have a method
439called C<results> that returns the results, it should call C<< ->wait >> 685called C<results> that returns the results, it should call C<< ->recv >>
440freely, as the user of your module knows what she is doing. always). 686freely, as the user of your module knows what she is doing. always).
441 687
442=head1 WHAT TO DO IN THE MAIN PROGRAM 688=head1 WHAT TO DO IN THE MAIN PROGRAM
443 689
444There will always be a single main program - the only place that should 690There will always be a single main program - the only place that should
446 692
447If it doesn't care, it can just "use AnyEvent" and use it itself, or not 693If it doesn't care, it can just "use AnyEvent" and use it itself, or not
448do anything special (it does not need to be event-based) and let AnyEvent 694do anything special (it does not need to be event-based) and let AnyEvent
449decide which implementation to chose if some module relies on it. 695decide which implementation to chose if some module relies on it.
450 696
451If the main program relies on a specific event model. For example, in 697If the main program relies on a specific event model - for example, in
452Gtk2 programs you have to rely on the Glib module. You should load the 698Gtk2 programs you have to rely on the Glib module - you should load the
453event module before loading AnyEvent or any module that uses it: generally 699event module before loading AnyEvent or any module that uses it: generally
454speaking, you should load it as early as possible. The reason is that 700speaking, you should load it as early as possible. The reason is that
455modules might create watchers when they are loaded, and AnyEvent will 701modules might create watchers when they are loaded, and AnyEvent will
456decide on the event model to use as soon as it creates watchers, and it 702decide on the event model to use as soon as it creates watchers, and it
457might chose the wrong one unless you load the correct one yourself. 703might chose the wrong one unless you load the correct one yourself.
458 704
459You can chose to use a rather inefficient pure-perl implementation by 705You can chose to use a pure-perl implementation by loading the
460loading the C<AnyEvent::Impl::Perl> module, which gives you similar 706C<AnyEvent::Impl::Perl> module, which gives you similar behaviour
461behaviour everywhere, but letting AnyEvent chose is generally better. 707everywhere, but letting AnyEvent chose the model is generally better.
708
709=head2 MAINLOOP EMULATION
710
711Sometimes (often for short test scripts, or even standalone programs who
712only want to use AnyEvent), you do not want to run a specific event loop.
713
714In that case, you can use a condition variable like this:
715
716 AnyEvent->condvar->recv;
717
718This has the effect of entering the event loop and looping forever.
719
720Note that usually your program has some exit condition, in which case
721it is better to use the "traditional" approach of storing a condition
722variable somewhere, waiting for it, and sending it when the program should
723exit cleanly.
724
725
726=head1 OTHER MODULES
727
728The following is a non-exhaustive list of additional modules that use
729AnyEvent and can therefore be mixed easily with other AnyEvent modules
730in the same program. Some of the modules come with AnyEvent, some are
731available via CPAN.
732
733=over 4
734
735=item L<AnyEvent::Util>
736
737Contains various utility functions that replace often-used but blocking
738functions such as C<inet_aton> by event-/callback-based versions.
739
740=item L<AnyEvent::Socket>
741
742Provides various utility functions for (internet protocol) sockets,
743addresses and name resolution. Also functions to create non-blocking tcp
744connections or tcp servers, with IPv6 and SRV record support and more.
745
746=item L<AnyEvent::Handle>
747
748Provide read and write buffers, manages watchers for reads and writes,
749supports raw and formatted I/O, I/O queued and fully transparent and
750non-blocking SSL/TLS.
751
752=item L<AnyEvent::DNS>
753
754Provides rich asynchronous DNS resolver capabilities.
755
756=item L<AnyEvent::HTTP>
757
758A simple-to-use HTTP library that is capable of making a lot of concurrent
759HTTP requests.
760
761=item L<AnyEvent::HTTPD>
762
763Provides a simple web application server framework.
764
765=item L<AnyEvent::FastPing>
766
767The fastest ping in the west.
768
769=item L<AnyEvent::DBI>
770
771Executes L<DBI> requests asynchronously in a proxy process.
772
773=item L<AnyEvent::AIO>
774
775Truly asynchronous I/O, should be in the toolbox of every event
776programmer. AnyEvent::AIO transparently fuses L<IO::AIO> and AnyEvent
777together.
778
779=item L<AnyEvent::BDB>
780
781Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently fuses
782L<BDB> and AnyEvent together.
783
784=item L<AnyEvent::GPSD>
785
786A non-blocking interface to gpsd, a daemon delivering GPS information.
787
788=item L<AnyEvent::IGS>
789
790A non-blocking interface to the Internet Go Server protocol (used by
791L<App::IGS>).
792
793=item L<Net::IRC3>
794
795AnyEvent based IRC client module family.
796
797=item L<Net::XMPP2>
798
799AnyEvent based XMPP (Jabber protocol) module family.
800
801=item L<Net::FCP>
802
803AnyEvent-based implementation of the Freenet Client Protocol, birthplace
804of AnyEvent.
805
806=item L<Event::ExecFlow>
807
808High level API for event-based execution flow control.
809
810=item L<Coro>
811
812Has special support for AnyEvent via L<Coro::AnyEvent>.
813
814=item L<IO::Lambda>
815
816The lambda approach to I/O - don't ask, look there. Can use AnyEvent.
817
818=back
462 819
463=cut 820=cut
464 821
465package AnyEvent; 822package AnyEvent;
466 823
467no warnings; 824no warnings;
468use strict; 825use strict;
469 826
470use Carp; 827use Carp;
471 828
472our $VERSION = '3.3'; 829our $VERSION = 4.2;
473our $MODEL; 830our $MODEL;
474 831
475our $AUTOLOAD; 832our $AUTOLOAD;
476our @ISA; 833our @ISA;
477 834
835our @REGISTRY;
836
837our $WIN32;
838
839BEGIN {
840 my $win32 = ! ! ($^O =~ /mswin32/i);
841 eval "sub WIN32(){ $win32 }";
842}
843
478our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1; 844our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
479 845
480our @REGISTRY; 846our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
847
848{
849 my $idx;
850 $PROTOCOL{$_} = ++$idx
851 for reverse split /\s*,\s*/,
852 $ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
853}
481 854
482my @models = ( 855my @models = (
483 [Coro::EV:: => AnyEvent::Impl::CoroEV::],
484 [Coro::Event:: => AnyEvent::Impl::CoroEvent::],
485 [EV:: => AnyEvent::Impl::EV::], 856 [EV:: => AnyEvent::Impl::EV::],
486 [Event:: => AnyEvent::Impl::Event::], 857 [Event:: => AnyEvent::Impl::Event::],
487 [Glib:: => AnyEvent::Impl::Glib::],
488 [Tk:: => AnyEvent::Impl::Tk::],
489 [Wx:: => AnyEvent::Impl::POE::],
490 [Prima:: => AnyEvent::Impl::POE::],
491 [AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::], 858 [AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
492 # everything below here will not be autoprobed as the pureperl backend should work everywhere 859 # everything below here will not be autoprobed
860 # as the pureperl backend should work everywhere
861 # and is usually faster
862 [Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
863 [Glib:: => AnyEvent::Impl::Glib::], # becomes extremely slow with many watchers
493 [Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy 864 [Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
494 [Qt:: => AnyEvent::Impl::Qt::], # requires special main program 865 [Qt:: => AnyEvent::Impl::Qt::], # requires special main program
495 [POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza 866 [POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
867 [Wx:: => AnyEvent::Impl::POE::],
868 [Prima:: => AnyEvent::Impl::POE::],
496); 869);
497 870
498our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY); 871our %method = map +($_ => 1), qw(io timer time now signal child condvar one_event DESTROY);
872
873our @post_detect;
874
875sub post_detect(&) {
876 my ($cb) = @_;
877
878 if ($MODEL) {
879 $cb->();
880
881 1
882 } else {
883 push @post_detect, $cb;
884
885 defined wantarray
886 ? bless \$cb, "AnyEvent::Util::PostDetect"
887 : ()
888 }
889}
890
891sub AnyEvent::Util::PostDetect::DESTROY {
892 @post_detect = grep $_ != ${$_[0]}, @post_detect;
893}
499 894
500sub detect() { 895sub detect() {
501 unless ($MODEL) { 896 unless ($MODEL) {
502 no strict 'refs'; 897 no strict 'refs';
898 local $SIG{__DIE__};
503 899
504 if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) { 900 if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
505 my $model = "AnyEvent::Impl::$1"; 901 my $model = "AnyEvent::Impl::$1";
506 if (eval "require $model") { 902 if (eval "require $model") {
507 $MODEL = $model; 903 $MODEL = $model;
537 last; 933 last;
538 } 934 }
539 } 935 }
540 936
541 $MODEL 937 $MODEL
542 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."; 938 or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.";
543 } 939 }
544 } 940 }
545 941
546 unshift @ISA, $MODEL; 942 unshift @ISA, $MODEL;
547 push @{"$MODEL\::ISA"}, "AnyEvent::Base"; 943 push @{"$MODEL\::ISA"}, "AnyEvent::Base";
944
945 (shift @post_detect)->() while @post_detect;
548 } 946 }
549 947
550 $MODEL 948 $MODEL
551} 949}
552 950
562 $class->$func (@_); 960 $class->$func (@_);
563} 961}
564 962
565package AnyEvent::Base; 963package AnyEvent::Base;
566 964
965# default implementation for now and time
966
967use Time::HiRes ();
968
969sub time { Time::HiRes::time }
970sub now { Time::HiRes::time }
971
567# default implementation for ->condvar, ->wait, ->broadcast 972# default implementation for ->condvar
568 973
569sub condvar { 974sub condvar {
570 bless \my $flag, "AnyEvent::Base::CondVar" 975 bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, AnyEvent::CondVar::
571}
572
573sub AnyEvent::Base::CondVar::broadcast {
574 ${$_[0]}++;
575}
576
577sub AnyEvent::Base::CondVar::wait {
578 AnyEvent->one_event while !${$_[0]};
579} 976}
580 977
581# default implementation for ->signal 978# default implementation for ->signal
582 979
583our %SIG_CB; 980our %SIG_CB;
599sub AnyEvent::Base::Signal::DESTROY { 996sub AnyEvent::Base::Signal::DESTROY {
600 my ($signal, $cb) = @{$_[0]}; 997 my ($signal, $cb) = @{$_[0]};
601 998
602 delete $SIG_CB{$signal}{$cb}; 999 delete $SIG_CB{$signal}{$cb};
603 1000
604 $SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} }; 1001 delete $SIG{$signal} unless keys %{ $SIG_CB{$signal} };
605} 1002}
606 1003
607# default implementation for ->child 1004# default implementation for ->child
608 1005
609our %PID_CB; 1006our %PID_CB;
636 or Carp::croak "required option 'pid' is missing"; 1033 or Carp::croak "required option 'pid' is missing";
637 1034
638 $PID_CB{$pid}{$arg{cb}} = $arg{cb}; 1035 $PID_CB{$pid}{$arg{cb}} = $arg{cb};
639 1036
640 unless ($WNOHANG) { 1037 unless ($WNOHANG) {
641 $WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1; 1038 $WNOHANG = eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
642 } 1039 }
643 1040
644 unless ($CHLD_W) { 1041 unless ($CHLD_W) {
645 $CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld); 1042 $CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
646 # child could be a zombie already, so make at least one round 1043 # child could be a zombie already, so make at least one round
656 delete $PID_CB{$pid}{$cb}; 1053 delete $PID_CB{$pid}{$cb};
657 delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} }; 1054 delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
658 1055
659 undef $CHLD_W unless keys %PID_CB; 1056 undef $CHLD_W unless keys %PID_CB;
660} 1057}
1058
1059package AnyEvent::CondVar;
1060
1061our @ISA = AnyEvent::CondVar::Base::;
1062
1063package AnyEvent::CondVar::Base;
1064
1065use overload
1066 '&{}' => sub { my $self = shift; sub { $self->send (@_) } },
1067 fallback => 1;
1068
1069sub _send {
1070 # nop
1071}
1072
1073sub send {
1074 my $cv = shift;
1075 $cv->{_ae_sent} = [@_];
1076 (delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
1077 $cv->_send;
1078}
1079
1080sub croak {
1081 $_[0]{_ae_croak} = $_[1];
1082 $_[0]->send;
1083}
1084
1085sub ready {
1086 $_[0]{_ae_sent}
1087}
1088
1089sub _wait {
1090 AnyEvent->one_event while !$_[0]{_ae_sent};
1091}
1092
1093sub recv {
1094 $_[0]->_wait;
1095
1096 Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};
1097 wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]
1098}
1099
1100sub cb {
1101 $_[0]{_ae_cb} = $_[1] if @_ > 1;
1102 $_[0]{_ae_cb}
1103}
1104
1105sub begin {
1106 ++$_[0]{_ae_counter};
1107 $_[0]{_ae_end_cb} = $_[1] if @_ > 1;
1108}
1109
1110sub end {
1111 return if --$_[0]{_ae_counter};
1112 &{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
1113}
1114
1115# undocumented/compatibility with pre-3.4
1116*broadcast = \&send;
1117*wait = \&_wait;
661 1118
662=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE 1119=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
663 1120
664This is an advanced topic that you do not normally need to use AnyEvent in 1121This is an advanced topic that you do not normally need to use AnyEvent in
665a module. This section is only of use to event loop authors who want to 1122a module. This section is only of use to event loop authors who want to
722model it chooses. 1179model it chooses.
723 1180
724=item C<PERL_ANYEVENT_MODEL> 1181=item C<PERL_ANYEVENT_MODEL>
725 1182
726This can be used to specify the event model to be used by AnyEvent, before 1183This can be used to specify the event model to be used by AnyEvent, before
727autodetection and -probing kicks in. It must be a string consisting 1184auto detection and -probing kicks in. It must be a string consisting
728entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended 1185entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
729and the resulting module name is loaded and if the load was successful, 1186and the resulting module name is loaded and if the load was successful,
730used as event model. If it fails to load AnyEvent will proceed with 1187used as event model. If it fails to load AnyEvent will proceed with
731autodetection and -probing. 1188auto detection and -probing.
732 1189
733This functionality might change in future versions. 1190This functionality might change in future versions.
734 1191
735For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you 1192For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
736could start your program like this: 1193could start your program like this:
737 1194
738 PERL_ANYEVENT_MODEL=Perl perl ... 1195 PERL_ANYEVENT_MODEL=Perl perl ...
1196
1197=item C<PERL_ANYEVENT_PROTOCOLS>
1198
1199Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
1200for IPv4 or IPv6. The default is unspecified (and might change, or be the result
1201of auto probing).
1202
1203Must be set to a comma-separated list of protocols or address families,
1204current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
1205used, and preference will be given to protocols mentioned earlier in the
1206list.
1207
1208This variable can effectively be used for denial-of-service attacks
1209against local programs (e.g. when setuid), although the impact is likely
1210small, as the program has to handle connection errors already-
1211
1212Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
1213but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
1214- only support IPv4, never try to resolve or contact IPv6
1215addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
1216IPv6, but prefer IPv6 over IPv4.
1217
1218=item C<PERL_ANYEVENT_EDNS0>
1219
1220Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
1221for DNS. This extension is generally useful to reduce DNS traffic, but
1222some (broken) firewalls drop such DNS packets, which is why it is off by
1223default.
1224
1225Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
1226EDNS0 in its DNS requests.
1227
1228=item C<PERL_ANYEVENT_MAX_FORKS>
1229
1230The maximum number of child processes that C<AnyEvent::Util::fork_call>
1231will create in parallel.
739 1232
740=back 1233=back
741 1234
742=head1 EXAMPLE PROGRAM 1235=head1 EXAMPLE PROGRAM
743 1236
754 poll => 'r', 1247 poll => 'r',
755 cb => sub { 1248 cb => sub {
756 warn "io event <$_[0]>\n"; # will always output <r> 1249 warn "io event <$_[0]>\n"; # will always output <r>
757 chomp (my $input = <STDIN>); # read a line 1250 chomp (my $input = <STDIN>); # read a line
758 warn "read: $input\n"; # output what has been read 1251 warn "read: $input\n"; # output what has been read
759 $cv->broadcast if $input =~ /^q/i; # quit program if /^q/i 1252 $cv->send if $input =~ /^q/i; # quit program if /^q/i
760 }, 1253 },
761 ); 1254 );
762 1255
763 my $time_watcher; # can only be used once 1256 my $time_watcher; # can only be used once
764 1257
769 }); 1262 });
770 } 1263 }
771 1264
772 new_timer; # create first timer 1265 new_timer; # create first timer
773 1266
774 $cv->wait; # wait until user enters /^q/i 1267 $cv->recv; # wait until user enters /^q/i
775 1268
776=head1 REAL-WORLD EXAMPLE 1269=head1 REAL-WORLD EXAMPLE
777 1270
778Consider the L<Net::FCP> module. It features (among others) the following 1271Consider the L<Net::FCP> module. It features (among others) the following
779API calls, which are to freenet what HTTP GET requests are to http: 1272API calls, which are to freenet what HTTP GET requests are to http:
829 syswrite $txn->{fh}, $txn->{request} 1322 syswrite $txn->{fh}, $txn->{request}
830 or die "connection or write error"; 1323 or die "connection or write error";
831 $txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r }); 1324 $txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
832 1325
833Again, C<fh_ready_r> waits till all data has arrived, and then stores the 1326Again, C<fh_ready_r> waits till all data has arrived, and then stores the
834result and signals any possible waiters that the request ahs finished: 1327result and signals any possible waiters that the request has finished:
835 1328
836 sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf}; 1329 sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
837 1330
838 if (end-of-file or data complete) { 1331 if (end-of-file or data complete) {
839 $txn->{result} = $txn->{buf}; 1332 $txn->{result} = $txn->{buf};
840 $txn->{finished}->broadcast; 1333 $txn->{finished}->send;
841 $txb->{cb}->($txn) of $txn->{cb}; # also call callback 1334 $txb->{cb}->($txn) of $txn->{cb}; # also call callback
842 } 1335 }
843 1336
844The C<result> method, finally, just waits for the finished signal (if the 1337The C<result> method, finally, just waits for the finished signal (if the
845request was already finished, it doesn't wait, of course, and returns the 1338request was already finished, it doesn't wait, of course, and returns the
846data: 1339data:
847 1340
848 $txn->{finished}->wait; 1341 $txn->{finished}->recv;
849 return $txn->{result}; 1342 return $txn->{result};
850 1343
851The actual code goes further and collects all errors (C<die>s, exceptions) 1344The actual code goes further and collects all errors (C<die>s, exceptions)
852that occured during request processing. The C<result> method detects 1345that occurred during request processing. The C<result> method detects
853whether an exception as thrown (it is stored inside the $txn object) 1346whether an exception as thrown (it is stored inside the $txn object)
854and just throws the exception, which means connection errors and other 1347and just throws the exception, which means connection errors and other
855problems get reported tot he code that tries to use the result, not in a 1348problems get reported tot he code that tries to use the result, not in a
856random callback. 1349random callback.
857 1350
888 1381
889 my $quit = AnyEvent->condvar; 1382 my $quit = AnyEvent->condvar;
890 1383
891 $fcp->txn_client_get ($url)->cb (sub { 1384 $fcp->txn_client_get ($url)->cb (sub {
892 ... 1385 ...
893 $quit->broadcast; 1386 $quit->send;
894 }); 1387 });
895 1388
896 $quit->wait; 1389 $quit->recv;
897 1390
898 1391
899=head1 BENCHMARKS 1392=head1 BENCHMARKS
900 1393
901To give you an idea of the performance and overheads that AnyEvent adds 1394To give you an idea of the performance and overheads that AnyEvent adds
903of various event loops I prepared some benchmarks. 1396of various event loops I prepared some benchmarks.
904 1397
905=head2 BENCHMARKING ANYEVENT OVERHEAD 1398=head2 BENCHMARKING ANYEVENT OVERHEAD
906 1399
907Here is a benchmark of various supported event models used natively and 1400Here is a benchmark of various supported event models used natively and
908through anyevent. The benchmark creates a lot of timers (with a zero 1401through AnyEvent. The benchmark creates a lot of timers (with a zero
909timeout) and I/O watchers (watching STDOUT, a pty, to become writable, 1402timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
910which it is), lets them fire exactly once and destroys them again. 1403which it is), lets them fire exactly once and destroys them again.
911 1404
912Source code for this benchmark is found as F<eg/bench> in the AnyEvent 1405Source code for this benchmark is found as F<eg/bench> in the AnyEvent
913distribution. 1406distribution.
930all watchers, to avoid adding memory overhead. That means closure creation 1423all watchers, to avoid adding memory overhead. That means closure creation
931and memory usage is not included in the figures. 1424and memory usage is not included in the figures.
932 1425
933I<invoke> is the time, in microseconds, used to invoke a simple 1426I<invoke> is the time, in microseconds, used to invoke a simple
934callback. The callback simply counts down a Perl variable and after it was 1427callback. The callback simply counts down a Perl variable and after it was
935invoked "watcher" times, it would C<< ->broadcast >> a condvar once to 1428invoked "watcher" times, it would C<< ->send >> a condvar once to
936signal the end of this phase. 1429signal the end of this phase.
937 1430
938I<destroy> is the time, in microseconds, that it takes to destroy a single 1431I<destroy> is the time, in microseconds, that it takes to destroy a single
939watcher. 1432watcher.
940 1433
944 EV/EV 400000 244 0.56 0.46 0.31 EV native interface 1437 EV/EV 400000 244 0.56 0.46 0.31 EV native interface
945 EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers 1438 EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers
946 CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal 1439 CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal
947 Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation 1440 Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation
948 Event/Event 16000 516 31.88 31.30 0.85 Event native interface 1441 Event/Event 16000 516 31.88 31.30 0.85 Event native interface
949 Event/Any 16000 936 39.17 33.63 1.43 Event + AnyEvent watchers 1442 Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers
950 Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour 1443 Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour
951 Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers 1444 Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers
952 POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event 1445 POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event
953 POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select 1446 POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select
954 1447
958well. For example, a select-based event loop (such as the pure perl one) 1451well. For example, a select-based event loop (such as the pure perl one)
959can never compete with an event loop that uses epoll when the number of 1452can never compete with an event loop that uses epoll when the number of
960file descriptors grows high. In this benchmark, all events become ready at 1453file descriptors grows high. In this benchmark, all events become ready at
961the same time, so select/poll-based implementations get an unnatural speed 1454the same time, so select/poll-based implementations get an unnatural speed
962boost. 1455boost.
1456
1457Also, note that the number of watchers usually has a nonlinear effect on
1458overall speed, that is, creating twice as many watchers doesn't take twice
1459the time - usually it takes longer. This puts event loops tested with a
1460higher number of watchers at a disadvantage.
1461
1462To put the range of results into perspective, consider that on the
1463benchmark machine, handling an event takes roughly 1600 CPU cycles with
1464EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
1465cycles with POE.
963 1466
964C<EV> is the sole leader regarding speed and memory use, which are both 1467C<EV> is the sole leader regarding speed and memory use, which are both
965maximal/minimal, respectively. Even when going through AnyEvent, it uses 1468maximal/minimal, respectively. Even when going through AnyEvent, it uses
966far less memory than any other event loop and is still faster than Event 1469far less memory than any other event loop and is still faster than Event
967natively. 1470natively.
990file descriptor is dup()ed for each watcher. This shows that the dup() 1493file descriptor is dup()ed for each watcher. This shows that the dup()
991employed by some adaptors is not a big performance issue (it does incur a 1494employed by some adaptors is not a big performance issue (it does incur a
992hidden memory cost inside the kernel which is not reflected in the figures 1495hidden memory cost inside the kernel which is not reflected in the figures
993above). 1496above).
994 1497
995C<POE>, regardless of underlying event loop (whether using its pure 1498C<POE>, regardless of underlying event loop (whether using its pure perl
996perl select-based backend or the Event module, the POE-EV backend 1499select-based backend or the Event module, the POE-EV backend couldn't
997couldn't be tested because it wasn't working) shows abysmal performance 1500be tested because it wasn't working) shows abysmal performance and
998and memory usage: Watchers use almost 30 times as much memory as 1501memory usage with AnyEvent: Watchers use almost 30 times as much memory
999EV watchers, and 10 times as much memory as Event (the high memory 1502as EV watchers, and 10 times as much memory as Event (the high memory
1000requirements are caused by requiring a session for each watcher). Watcher 1503requirements are caused by requiring a session for each watcher). Watcher
1001invocation speed is almost 900 times slower than with AnyEvent's pure perl 1504invocation speed is almost 900 times slower than with AnyEvent's pure perl
1505implementation.
1506
1002implementation. The design of the POE adaptor class in AnyEvent can not 1507The design of the POE adaptor class in AnyEvent can not really account
1003really account for this, as session creation overhead is small compared 1508for the performance issues, though, as session creation overhead is
1004to execution of the state machine, which is coded pretty optimally within 1509small compared to execution of the state machine, which is coded pretty
1005L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow. 1510optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that
1511using multiple sessions is not a good approach, especially regarding
1512memory usage, even the author of POE could not come up with a faster
1513design).
1006 1514
1007=head3 Summary 1515=head3 Summary
1008 1516
1009=over 4 1517=over 4
1010 1518
1021 1529
1022=back 1530=back
1023 1531
1024=head2 BENCHMARKING THE LARGE SERVER CASE 1532=head2 BENCHMARKING THE LARGE SERVER CASE
1025 1533
1026This benchmark atcually benchmarks the event loop itself. It works by 1534This benchmark actually benchmarks the event loop itself. It works by
1027creating a number of "servers": each server consists of a socketpair, a 1535creating a number of "servers": each server consists of a socket pair, a
1028timeout watcher that gets reset on activity (but never fires), and an I/O 1536timeout watcher that gets reset on activity (but never fires), and an I/O
1029watcher waiting for input on one side of the socket. Each time the socket 1537watcher waiting for input on one side of the socket. Each time the socket
1030watcher reads a byte it will write that byte to a random other "server". 1538watcher reads a byte it will write that byte to a random other "server".
1031 1539
1032The effect is that there will be a lot of I/O watchers, only part of which 1540The effect is that there will be a lot of I/O watchers, only part of which
1033are active at any one point (so there is a constant number of active 1541are active at any one point (so there is a constant number of active
1034fds for each loop iterstaion, but which fds these are is random). The 1542fds for each loop iteration, but which fds these are is random). The
1035timeout is reset each time something is read because that reflects how 1543timeout is reset each time something is read because that reflects how
1036most timeouts work (and puts extra pressure on the event loops). 1544most timeouts work (and puts extra pressure on the event loops).
1037 1545
1038In this benchmark, we use 10000 socketpairs (20000 sockets), of which 100 1546In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
1039(1%) are active. This mirrors the activity of large servers with many 1547(1%) are active. This mirrors the activity of large servers with many
1040connections, most of which are idle at any one point in time. 1548connections, most of which are idle at any one point in time.
1041 1549
1042Source code for this benchmark is found as F<eg/bench2> in the AnyEvent 1550Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
1043distribution. 1551distribution.
1044 1552
1045=head3 Explanation of the columns 1553=head3 Explanation of the columns
1046 1554
1047I<sockets> is the number of sockets, and twice the number of "servers" (as 1555I<sockets> is the number of sockets, and twice the number of "servers" (as
1048eahc server has a read and write socket end). 1556each server has a read and write socket end).
1049 1557
1050I<create> is the time it takes to create a socketpair (which is 1558I<create> is the time it takes to create a socket pair (which is
1051nontrivial) and two watchers: an I/O watcher and a timeout watcher. 1559nontrivial) and two watchers: an I/O watcher and a timeout watcher.
1052 1560
1053I<request>, the most important value, is the time it takes to handle a 1561I<request>, the most important value, is the time it takes to handle a
1054single "request", that is, reading the token from the pipe and forwarding 1562single "request", that is, reading the token from the pipe and forwarding
1055it to another server. This includes deleting the old timeout and creating 1563it to another server. This includes deleting the old timeout and creating
1057 1565
1058=head3 Results 1566=head3 Results
1059 1567
1060 name sockets create request 1568 name sockets create request
1061 EV 20000 69.01 11.16 1569 EV 20000 69.01 11.16
1062 Perl 20000 75.28 112.76 1570 Perl 20000 73.32 35.87
1063 Event 20000 212.62 257.32 1571 Event 20000 212.62 257.32
1064 Glib 20000 651.16 1896.30 1572 Glib 20000 651.16 1896.30
1065 POE 20000 349.67 12317.24 uses POE::Loop::Event 1573 POE 20000 349.67 12317.24 uses POE::Loop::Event
1066 1574
1067=head3 Discussion 1575=head3 Discussion
1089 1597
1090=head3 Summary 1598=head3 Summary
1091 1599
1092=over 4 1600=over 4
1093 1601
1094=item * The pure perl implementation performs extremely well, considering 1602=item * The pure perl implementation performs extremely well.
1095that it uses select.
1096 1603
1097=item * Avoid Glib or POE in large projects where performance matters. 1604=item * Avoid Glib or POE in large projects where performance matters.
1098 1605
1099=back 1606=back
1100 1607
1113 1620
1114=head3 Results 1621=head3 Results
1115 1622
1116 name sockets create request 1623 name sockets create request
1117 EV 16 20.00 6.54 1624 EV 16 20.00 6.54
1625 Perl 16 25.75 12.62
1118 Event 16 81.27 35.86 1626 Event 16 81.27 35.86
1119 Glib 16 32.63 15.48 1627 Glib 16 32.63 15.48
1120 Perl 16 24.62 162.37
1121 POE 16 261.87 276.28 uses POE::Loop::Event 1628 POE 16 261.87 276.28 uses POE::Loop::Event
1122 1629
1123=head3 Discussion 1630=head3 Discussion
1124 1631
1125The benchmark tries to test the performance of a typical small 1632The benchmark tries to test the performance of a typical small
1126server. While knowing how various event loops perform is interesting, keep 1633server. While knowing how various event loops perform is interesting, keep
1127in mind that their overhead in this case is usually not as important, due 1634in mind that their overhead in this case is usually not as important, due
1128to the small absolute number of watchers. 1635to the small absolute number of watchers (that is, you need efficiency and
1636speed most when you have lots of watchers, not when you only have a few of
1637them).
1129 1638
1130EV is again fastest. 1639EV is again fastest.
1131 1640
1132The C-based event loops Event and Glib come in second this time, as the 1641Perl again comes second. It is noticeably faster than the C-based event
1133overhead of running an iteration is much smaller in C than in Perl (little 1642loops Event and Glib, although the difference is too small to really
1134code to execute in the inner loop, and perl's function calling overhead is 1643matter.
1135high, and updating all the data structures is costly).
1136 1644
1137The pure perl event loop is much slower, but still competitive.
1138
1139POE also performs much better in this case, but is is stillf ar behind the 1645POE also performs much better in this case, but is is still far behind the
1140others. 1646others.
1141 1647
1142=head3 Summary 1648=head3 Summary
1143 1649
1144=over 4 1650=over 4
1150 1656
1151 1657
1152=head1 FORK 1658=head1 FORK
1153 1659
1154Most event libraries are not fork-safe. The ones who are usually are 1660Most event libraries are not fork-safe. The ones who are usually are
1155because they are so inefficient. Only L<EV> is fully fork-aware. 1661because they rely on inefficient but fork-safe C<select> or C<poll>
1662calls. Only L<EV> is fully fork-aware.
1156 1663
1157If you have to fork, you must either do so I<before> creating your first 1664If you have to fork, you must either do so I<before> creating your first
1158watcher OR you must not use AnyEvent at all in the child. 1665watcher OR you must not use AnyEvent at all in the child.
1159 1666
1160 1667
1168specified in the variable. 1675specified in the variable.
1169 1676
1170You can make AnyEvent completely ignore this variable by deleting it 1677You can make AnyEvent completely ignore this variable by deleting it
1171before the first watcher gets created, e.g. with a C<BEGIN> block: 1678before the first watcher gets created, e.g. with a C<BEGIN> block:
1172 1679
1173 BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} } 1680 BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1174 1681
1175 use AnyEvent; 1682 use AnyEvent;
1683
1684Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
1685be used to probe what backend is used and gain other information (which is
1686probably even less useful to an attacker than PERL_ANYEVENT_MODEL).
1687
1688
1689=head1 BUGS
1690
1691Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
1692to work around. If you suffer from memleaks, first upgrade to Perl 5.10
1693and check wether the leaks still show up. (Perl 5.10.0 has other annoying
1694mamleaks, such as leaking on C<map> and C<grep> but it is usually not as
1695pronounced).
1176 1696
1177 1697
1178=head1 SEE ALSO 1698=head1 SEE ALSO
1179 1699
1180Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>, 1700Utility functions: L<AnyEvent::Util>.
1181L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>, 1701
1702Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,
1182L<Event::Lib>, L<Qt>, L<POE>. 1703L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
1183 1704
1184Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>, 1705Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
1185L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>, 1706L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
1186L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>, 1707L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
1187L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>. 1708L<AnyEvent::Impl::POE>.
1188 1709
1710Non-blocking file handles, sockets, TCP clients and
1711servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>.
1712
1713Asynchronous DNS: L<AnyEvent::DNS>.
1714
1715Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>,
1716
1189Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>. 1717Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>, L<AnyEvent::DNS>.
1190 1718
1191 1719
1192=head1 AUTHOR 1720=head1 AUTHOR
1193 1721
1194 Marc Lehmann <schmorp@schmorp.de> 1722 Marc Lehmann <schmorp@schmorp.de>
1195 http://home.schmorp.de/ 1723 http://home.schmorp.de/
1196 1724
1197=cut 1725=cut
1198 1726
11991 17271
1200 1728

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