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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#TODO#
72
73Net::IRC3
74AnyEvent::HTTPD
75AnyEvent::DNS
76IO::AnyEvent
77Net::FPing
78Net::XMPP2
79Coro
80
81AnyEvent::IRC
82AnyEvent::HTTPD
83AnyEvent::DNS
84AnyEvent::Handle
85AnyEvent::Socket
86AnyEvent::FPing
87AnyEvent::XMPP
88AnyEvent::SNMP
89Coro
90 82
91=head1 DESCRIPTION 83=head1 DESCRIPTION
92 84
93L<AnyEvent> provides an identical interface to multiple event loops. This 85L<AnyEvent> provides an identical interface to multiple event loops. This
94allows module authors to utilise an event loop without forcing module 86allows module authors to utilise an event loop without forcing module
98The 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>
99module. 91module.
100 92
101During the first call of any watcher-creation method, the module tries 93During the first call of any watcher-creation method, the module tries
102to 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
103following modules is already loaded: L<Coro::EV>, L<Coro::Event>, L<EV>, 95following modules is already loaded: L<EV>,
104L<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>,
105L<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
106to 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
107adaptor 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
108be 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
122starts 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
123use AnyEvent so their modules work together with others seamlessly... 115use AnyEvent so their modules work together with others seamlessly...
124 116
125The pure-perl implementation of AnyEvent is called 117The pure-perl implementation of AnyEvent is called
126C<AnyEvent::Impl::Perl>. Like other event modules you can load it 118C<AnyEvent::Impl::Perl>. Like other event modules you can load it
127explicitly. 119explicitly and enjoy the high availability of that event loop :)
128 120
129=head1 WATCHERS 121=head1 WATCHERS
130 122
131AnyEvent 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
132stores 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
133the callback to call, the filehandle to watch, etc. 125the callback to call, the file handle to watch, etc.
134 126
135These watchers are normal Perl objects with normal Perl lifetime. After 127These watchers are normal Perl objects with normal Perl lifetime. After
136creating a watcher it will immediately "watch" for events and invoke the 128creating a watcher it will immediately "watch" for events and invoke the
137callback when the event occurs (of course, only when the event model 129callback when the event occurs (of course, only when the event model
138is in control). 130is in control).
146Many watchers either are used with "recursion" (repeating timers for 138Many watchers either are used with "recursion" (repeating timers for
147example), or need to refer to their watcher object in other ways. 139example), or need to refer to their watcher object in other ways.
148 140
149An any way to achieve that is this pattern: 141An any way to achieve that is this pattern:
150 142
151 my $w; $w = AnyEvent->type (arg => value ..., cb => sub { 143 my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
152 # you can use $w here, for example to undef it 144 # you can use $w here, for example to undef it
153 undef $w; 145 undef $w;
154 }); 146 });
155 147
156Note 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,
157my variables are only visible after the statement in which they are 149my variables are only visible after the statement in which they are
158declared. 150declared.
159 151
160=head2 I/O WATCHERS 152=head2 I/O WATCHERS
161 153
162You can create an I/O watcher by calling the C<< AnyEvent->io >> method 154You can create an I/O watcher by calling the C<< AnyEvent->io >> method
163with the following mandatory key-value pairs as arguments: 155with the following mandatory key-value pairs as arguments:
164 156
165C<fh> the Perl I<file handle> (I<not> file descriptor) to watch 157C<fh> the Perl I<file handle> (I<not> file descriptor) to watch for events
166for events. C<poll> must be a string that is either C<r> or C<w>, 158(AnyEvent might or might not keep a reference to this file handle). C<poll>
167which creates a watcher waiting for "r"eadable or "w"ritable events, 159must be a string that is either C<r> or C<w>, which creates a watcher
168respectively. C<cb> is the callback to invoke each time the file handle 160waiting for "r"eadable or "w"ritable events, respectively. C<cb> is the
169becomes ready. 161callback to invoke each time the file handle becomes ready.
170 162
171Although the callback might get passed parameters, their value and 163Although the callback might get passed parameters, their value and
172presence is undefined and you cannot rely on them. Portable AnyEvent 164presence is undefined and you cannot rely on them. Portable AnyEvent
173callbacks cannot use arguments passed to I/O watcher callbacks. 165callbacks cannot use arguments passed to I/O watcher callbacks.
174 166
178 170
179Some event loops issue spurious readyness notifications, so you should 171Some event loops issue spurious readyness notifications, so you should
180always use non-blocking calls when reading/writing from/to your file 172always use non-blocking calls when reading/writing from/to your file
181handles. 173handles.
182 174
183Example:
184
185 # 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
186 my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub { 178 my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
187 chomp (my $input = <STDIN>); 179 chomp (my $input = <STDIN>);
188 warn "read: $input\n"; 180 warn "read: $input\n";
189 undef $w; 181 undef $w;
190 }); 182 });
200 192
201Although the callback might get passed parameters, their value and 193Although the callback might get passed parameters, their value and
202presence is undefined and you cannot rely on them. Portable AnyEvent 194presence is undefined and you cannot rely on them. Portable AnyEvent
203callbacks cannot use arguments passed to time watcher callbacks. 195callbacks cannot use arguments passed to time watcher callbacks.
204 196
205The 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
206timer you have to create a new watcher (this is a limitation by both Tk 198parameter, C<interval>, as a strictly positive number (> 0), then the
207and Glib). 199callback will be invoked regularly at that interval (in fractional
200seconds) after the first invocation. If C<interval> is specified with a
201false value, then it is treated as if it were missing.
208 202
209Example: 203The callback will be rescheduled before invoking the callback, but no
204attempt is done to avoid timer drift in most backends, so the interval is
205only approximate.
210 206
211 # fire an event after 7.7 seconds 207Example: fire an event after 7.7 seconds.
208
212 my $w = AnyEvent->timer (after => 7.7, cb => sub { 209 my $w = AnyEvent->timer (after => 7.7, cb => sub {
213 warn "timeout\n"; 210 warn "timeout\n";
214 }); 211 });
215 212
216 # to cancel the timer: 213 # to cancel the timer:
217 undef $w; 214 undef $w;
218 215
219Example 2:
220
221 # fire an event after 0.5 seconds, then roughly every second 216Example 2: fire an event after 0.5 seconds, then roughly every second.
222 my $w;
223 217
224 my $cb = sub {
225 # cancel the old timer while creating a new one
226 $w = AnyEvent->timer (after => 1, cb => $cb); 218 my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
219 warn "timeout\n";
227 }; 220 };
228
229 # start the "loop" by creating the first watcher
230 $w = AnyEvent->timer (after => 0.5, cb => $cb);
231 221
232=head3 TIMING ISSUES 222=head3 TIMING ISSUES
233 223
234There are two ways to handle timers: based on real time (relative, "fire 224There are two ways to handle timers: based on real time (relative, "fire
235in 10 seconds") and based on wallclock time (absolute, "fire at 12 225in 10 seconds") and based on wallclock time (absolute, "fire at 12
247timers. 237timers.
248 238
249AnyEvent always prefers relative timers, if available, matching the 239AnyEvent always prefers relative timers, if available, matching the
250AnyEvent API. 240AnyEvent API.
251 241
242AnyEvent has two additional methods that return the "current time":
243
244=over 4
245
246=item AnyEvent->time
247
248This returns the "current wallclock time" as a fractional number of
249seconds since the Epoch (the same thing as C<time> or C<Time::HiRes::time>
250return, and the result is guaranteed to be compatible with those).
251
252It progresses independently of any event loop processing, i.e. each call
253will check the system clock, which usually gets updated frequently.
254
255=item AnyEvent->now
256
257This also returns the "current wallclock time", but unlike C<time>, above,
258this value might change only once per event loop iteration, depending on
259the event loop (most return the same time as C<time>, above). This is the
260time that AnyEvent's timers get scheduled against.
261
262I<In almost all cases (in all cases if you don't care), this is the
263function to call when you want to know the current time.>
264
265This function is also often faster then C<< AnyEvent->time >>, and
266thus the preferred method if you want some timestamp (for example,
267L<AnyEvent::Handle> uses this to update it's activity timeouts).
268
269The rest of this section is only of relevance if you try to be very exact
270with your timing, you can skip it without bad conscience.
271
272For a practical example of when these times differ, consider L<Event::Lib>
273and L<EV> and the following set-up:
274
275The event loop is running and has just invoked one of your callback at
276time=500 (assume no other callbacks delay processing). In your callback,
277you wait a second by executing C<sleep 1> (blocking the process for a
278second) and then (at time=501) you create a relative timer that fires
279after three seconds.
280
281With L<Event::Lib>, C<< AnyEvent->time >> and C<< AnyEvent->now >> will
282both return C<501>, because that is the current time, and the timer will
283be scheduled to fire at time=504 (C<501> + C<3>).
284
285With L<EV>, C<< AnyEvent->time >> returns C<501> (as that is the current
286time), but C<< AnyEvent->now >> returns C<500>, as that is the time the
287last event processing phase started. With L<EV>, your timer gets scheduled
288to run at time=503 (C<500> + C<3>).
289
290In one sense, L<Event::Lib> is more exact, as it uses the current time
291regardless of any delays introduced by event processing. However, most
292callbacks do not expect large delays in processing, so this causes a
293higher drift (and a lot more system calls to get the current time).
294
295In another sense, L<EV> is more exact, as your timer will be scheduled at
296the same time, regardless of how long event processing actually took.
297
298In either case, if you care (and in most cases, you don't), then you
299can get whatever behaviour you want with any event loop, by taking the
300difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
301account.
302
303=back
304
252=head2 SIGNAL WATCHERS 305=head2 SIGNAL WATCHERS
253 306
254You can watch for signals using a signal watcher, C<signal> is the signal 307You can watch for signals using a signal watcher, C<signal> is the signal
255I<name> without any C<SIG> prefix, C<cb> is the Perl callback to 308I<name> without any C<SIG> prefix, C<cb> is the Perl callback to
256be invoked whenever a signal occurs. 309be invoked whenever a signal occurs.
257 310
258Although the callback might get passed parameters, their value and 311Although the callback might get passed parameters, their value and
259presence is undefined and you cannot rely on them. Portable AnyEvent 312presence is undefined and you cannot rely on them. Portable AnyEvent
260callbacks cannot use arguments passed to signal watcher callbacks. 313callbacks cannot use arguments passed to signal watcher callbacks.
261 314
262Multiple signal occurances can be clumped together into one callback 315Multiple signal occurrences can be clumped together into one callback
263invocation, and callback invocation will be synchronous. synchronous means 316invocation, and callback invocation will be synchronous. Synchronous means
264that it might take a while until the signal gets handled by the process, 317that it might take a while until the signal gets handled by the process,
265but it is guarenteed not to interrupt any other callbacks. 318but it is guaranteed not to interrupt any other callbacks.
266 319
267The main advantage of using these watchers is that you can share a signal 320The main advantage of using these watchers is that you can share a signal
268between multiple watchers. 321between multiple watchers.
269 322
270This watcher might use C<%SIG>, so programs overwriting those signals 323This watcher might use C<%SIG>, so programs overwriting those signals
297AnyEvent program, you I<have> to create at least one watcher before you 350AnyEvent program, you I<have> to create at least one watcher before you
298C<fork> the child (alternatively, you can call C<AnyEvent::detect>). 351C<fork> the child (alternatively, you can call C<AnyEvent::detect>).
299 352
300Example: fork a process and wait for it 353Example: fork a process and wait for it
301 354
302 my $done = AnyEvent->condvar; 355 my $done = AnyEvent->condvar;
303 356
304 AnyEvent::detect; # force event module to be initialised
305
306 my $pid = fork or exit 5; 357 my $pid = fork or exit 5;
307 358
308 my $w = AnyEvent->child ( 359 my $w = AnyEvent->child (
309 pid => $pid, 360 pid => $pid,
310 cb => sub { 361 cb => sub {
311 my ($pid, $status) = @_; 362 my ($pid, $status) = @_;
312 warn "pid $pid exited with status $status"; 363 warn "pid $pid exited with status $status";
313 $done->broadcast; 364 $done->send;
314 }, 365 },
315 ); 366 );
316 367
317 # do something else, then wait for process exit 368 # do something else, then wait for process exit
318 $done->wait; 369 $done->recv;
319 370
320=head2 CONDITION VARIABLES 371=head2 CONDITION VARIABLES
321 372
373If you are familiar with some event loops you will know that all of them
374require you to run some blocking "loop", "run" or similar function that
375will actively watch for new events and call your callbacks.
376
377AnyEvent is different, it expects somebody else to run the event loop and
378will only block when necessary (usually when told by the user).
379
380The instrument to do that is called a "condition variable", so called
381because they represent a condition that must become true.
382
322Condition variables can be created by calling the C<< AnyEvent->condvar >> 383Condition variables can be created by calling the C<< AnyEvent->condvar
323method without any arguments. 384>> method, usually without arguments. The only argument pair allowed is
385C<cb>, which specifies a callback to be called when the condition variable
386becomes true.
324 387
325A condition variable waits for a condition - precisely that the C<< 388After creation, the condition variable is "false" until it becomes "true"
326->broadcast >> method has been called. 389by calling the C<send> method (or calling the condition variable as if it
390were a callback, read about the caveats in the description for the C<<
391->send >> method).
327 392
328They are very useful to signal that a condition has been fulfilled, for 393Condition variables are similar to callbacks, except that you can
394optionally wait for them. They can also be called merge points - points
395in time where multiple outstanding events have been processed. And yet
396another way to call them is transactions - each condition variable can be
397used to represent a transaction, which finishes at some point and delivers
398a result.
399
400Condition variables are very useful to signal that something has finished,
329example, if you write a module that does asynchronous http requests, 401for example, if you write a module that does asynchronous http requests,
330then a condition variable would be the ideal candidate to signal the 402then a condition variable would be the ideal candidate to signal the
331availability of results. 403availability of results. The user can either act when the callback is
404called or can synchronously C<< ->recv >> for the results.
332 405
333You can also use condition variables to block your main program until 406You can also use them to simulate traditional event loops - for example,
334an event occurs - for example, you could C<< ->wait >> in your main 407you can block your main program until an event occurs - for example, you
335program until the user clicks the Quit button in your app, which would C<< 408could C<< ->recv >> in your main program until the user clicks the Quit
336->broadcast >> the "quit" event. 409button of your app, which would C<< ->send >> the "quit" event.
337 410
338Note that condition variables recurse into the event loop - if you have 411Note that condition variables recurse into the event loop - if you have
339two pirces of code that call C<< ->wait >> in a round-robbin fashion, you 412two pieces of code that call C<< ->recv >> in a round-robin fashion, you
340lose. Therefore, condition variables are good to export to your caller, but 413lose. Therefore, condition variables are good to export to your caller, but
341you should avoid making a blocking wait yourself, at least in callbacks, 414you should avoid making a blocking wait yourself, at least in callbacks,
342as this asks for trouble. 415as this asks for trouble.
343 416
344This object has two methods: 417Condition variables are represented by hash refs in perl, and the keys
418used by AnyEvent itself are all named C<_ae_XXX> to make subclassing
419easy (it is often useful to build your own transaction class on top of
420AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call
421it's C<new> method in your own C<new> method.
422
423There are two "sides" to a condition variable - the "producer side" which
424eventually calls C<< -> send >>, and the "consumer side", which waits
425for the send to occur.
426
427Example: wait for a timer.
428
429 # wait till the result is ready
430 my $result_ready = AnyEvent->condvar;
431
432 # do something such as adding a timer
433 # or socket watcher the calls $result_ready->send
434 # when the "result" is ready.
435 # in this case, we simply use a timer:
436 my $w = AnyEvent->timer (
437 after => 1,
438 cb => sub { $result_ready->send },
439 );
440
441 # this "blocks" (while handling events) till the callback
442 # calls send
443 $result_ready->recv;
444
445Example: wait for a timer, but take advantage of the fact that
446condition variables are also code references.
447
448 my $done = AnyEvent->condvar;
449 my $delay = AnyEvent->timer (after => 5, cb => $done);
450 $done->recv;
451
452=head3 METHODS FOR PRODUCERS
453
454These methods should only be used by the producing side, i.e. the
455code/module that eventually sends the signal. Note that it is also
456the producer side which creates the condvar in most cases, but it isn't
457uncommon for the consumer to create it as well.
345 458
346=over 4 459=over 4
347 460
461=item $cv->send (...)
462
463Flag the condition as ready - a running C<< ->recv >> and all further
464calls to C<recv> will (eventually) return after this method has been
465called. If nobody is waiting the send will be remembered.
466
467If a callback has been set on the condition variable, it is called
468immediately from within send.
469
470Any arguments passed to the C<send> call will be returned by all
471future C<< ->recv >> calls.
472
473Condition variables are overloaded so one can call them directly
474(as a code reference). Calling them directly is the same as calling
475C<send>. Note, however, that many C-based event loops do not handle
476overloading, so as tempting as it may be, passing a condition variable
477instead of a callback does not work. Both the pure perl and EV loops
478support overloading, however, as well as all functions that use perl to
479invoke a callback (as in L<AnyEvent::Socket> and L<AnyEvent::DNS> for
480example).
481
482=item $cv->croak ($error)
483
484Similar to send, but causes all call's to C<< ->recv >> to invoke
485C<Carp::croak> with the given error message/object/scalar.
486
487This can be used to signal any errors to the condition variable
488user/consumer.
489
490=item $cv->begin ([group callback])
491
348=item $cv->wait 492=item $cv->end
349 493
350Wait (blocking if necessary) until the C<< ->broadcast >> method has been 494These two methods are EXPERIMENTAL and MIGHT CHANGE.
495
496These two methods can be used to combine many transactions/events into
497one. For example, a function that pings many hosts in parallel might want
498to use a condition variable for the whole process.
499
500Every call to C<< ->begin >> will increment a counter, and every call to
501C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
502>>, the (last) callback passed to C<begin> will be executed. That callback
503is I<supposed> to call C<< ->send >>, but that is not required. If no
504callback was set, C<send> will be called without any arguments.
505
506Let's clarify this with the ping example:
507
508 my $cv = AnyEvent->condvar;
509
510 my %result;
511 $cv->begin (sub { $cv->send (\%result) });
512
513 for my $host (@list_of_hosts) {
514 $cv->begin;
515 ping_host_then_call_callback $host, sub {
516 $result{$host} = ...;
517 $cv->end;
518 };
519 }
520
521 $cv->end;
522
523This code fragment supposedly pings a number of hosts and calls
524C<send> after results for all then have have been gathered - in any
525order. To achieve this, the code issues a call to C<begin> when it starts
526each ping request and calls C<end> when it has received some result for
527it. Since C<begin> and C<end> only maintain a counter, the order in which
528results arrive is not relevant.
529
530There is an additional bracketing call to C<begin> and C<end> outside the
531loop, which serves two important purposes: first, it sets the callback
532to be called once the counter reaches C<0>, and second, it ensures that
533C<send> is called even when C<no> hosts are being pinged (the loop
534doesn't execute once).
535
536This is the general pattern when you "fan out" into multiple subrequests:
537use an outer C<begin>/C<end> pair to set the callback and ensure C<end>
538is called at least once, and then, for each subrequest you start, call
539C<begin> and for each subrequest you finish, call C<end>.
540
541=back
542
543=head3 METHODS FOR CONSUMERS
544
545These methods should only be used by the consuming side, i.e. the
546code awaits the condition.
547
548=over 4
549
550=item $cv->recv
551
552Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
351called on c<$cv>, while servicing other watchers normally. 553>> methods have been called on c<$cv>, while servicing other watchers
554normally.
352 555
353You can only wait once on a condition - additional calls will return 556You can only wait once on a condition - additional calls are valid but
354immediately. 557will return immediately.
558
559If an error condition has been set by calling C<< ->croak >>, then this
560function will call C<croak>.
561
562In list context, all parameters passed to C<send> will be returned,
563in scalar context only the first one will be returned.
355 564
356Not all event models support a blocking wait - some die in that case 565Not all event models support a blocking wait - some die in that case
357(programs might want to do that to stay interactive), so I<if you are 566(programs might want to do that to stay interactive), so I<if you are
358using this from a module, never require a blocking wait>, but let the 567using this from a module, never require a blocking wait>, but let the
359caller decide whether the call will block or not (for example, by coupling 568caller decide whether the call will block or not (for example, by coupling
360condition variables with some kind of request results and supporting 569condition variables with some kind of request results and supporting
361callbacks so the caller knows that getting the result will not block, 570callbacks so the caller knows that getting the result will not block,
362while still suppporting blocking waits if the caller so desires). 571while still supporting blocking waits if the caller so desires).
363 572
364Another reason I<never> to C<< ->wait >> in a module is that you cannot 573Another reason I<never> to C<< ->recv >> in a module is that you cannot
365sensibly have two C<< ->wait >>'s in parallel, as that would require 574sensibly have two C<< ->recv >>'s in parallel, as that would require
366multiple interpreters or coroutines/threads, none of which C<AnyEvent> 575multiple interpreters or coroutines/threads, none of which C<AnyEvent>
367can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and 576can supply.
368L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
369from different coroutines, however).
370 577
371=item $cv->broadcast 578The L<Coro> module, however, I<can> and I<does> supply coroutines and, in
579fact, L<Coro::AnyEvent> replaces AnyEvent's condvars by coroutine-safe
580versions and also integrates coroutines into AnyEvent, making blocking
581C<< ->recv >> calls perfectly safe as long as they are done from another
582coroutine (one that doesn't run the event loop).
372 583
373Flag the condition as ready - a running C<< ->wait >> and all further 584You can ensure that C<< -recv >> never blocks by setting a callback and
374calls to C<wait> will (eventually) return after this method has been 585only calling C<< ->recv >> from within that callback (or at a later
375called. If nobody is waiting the broadcast will be remembered.. 586time). This will work even when the event loop does not support blocking
587waits otherwise.
588
589=item $bool = $cv->ready
590
591Returns true when the condition is "true", i.e. whether C<send> or
592C<croak> have been called.
593
594=item $cb = $cv->cb ([new callback])
595
596This is a mutator function that returns the callback set and optionally
597replaces it before doing so.
598
599The callback will be called when the condition becomes "true", i.e. when
600C<send> or C<croak> are called, with the only argument being the condition
601variable itself. Calling C<recv> inside the callback or at any later time
602is guaranteed not to block.
376 603
377=back 604=back
378
379Example:
380
381 # wait till the result is ready
382 my $result_ready = AnyEvent->condvar;
383
384 # do something such as adding a timer
385 # or socket watcher the calls $result_ready->broadcast
386 # when the "result" is ready.
387 # in this case, we simply use a timer:
388 my $w = AnyEvent->timer (
389 after => 1,
390 cb => sub { $result_ready->broadcast },
391 );
392
393 # this "blocks" (while handling events) till the watcher
394 # calls broadcast
395 $result_ready->wait;
396 605
397=head1 GLOBAL VARIABLES AND FUNCTIONS 606=head1 GLOBAL VARIABLES AND FUNCTIONS
398 607
399=over 4 608=over 4
400 609
406C<AnyEvent::Impl:xxx> modules, but can be any other class in the case 615C<AnyEvent::Impl:xxx> modules, but can be any other class in the case
407AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>). 616AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).
408 617
409The known classes so far are: 618The known classes so far are:
410 619
411 AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
412 AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
413 AnyEvent::Impl::EV based on EV (an interface to libev, best choice). 620 AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
414 AnyEvent::Impl::Event based on Event, second best choice. 621 AnyEvent::Impl::Event based on Event, second best choice.
622 AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
415 AnyEvent::Impl::Glib based on Glib, third-best choice. 623 AnyEvent::Impl::Glib based on Glib, third-best choice.
416 AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
417 AnyEvent::Impl::Tk based on Tk, very bad choice. 624 AnyEvent::Impl::Tk based on Tk, very bad choice.
418 AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs). 625 AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
419 AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse. 626 AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
420 AnyEvent::Impl::POE based on POE, not generic enough for full support. 627 AnyEvent::Impl::POE based on POE, not generic enough for full support.
421 628
434Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model 641Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
435if necessary. You should only call this function right before you would 642if necessary. You should only call this function right before you would
436have created an AnyEvent watcher anyway, that is, as late as possible at 643have created an AnyEvent watcher anyway, that is, as late as possible at
437runtime. 644runtime.
438 645
646=item $guard = AnyEvent::post_detect { BLOCK }
647
648Arranges for the code block to be executed as soon as the event model is
649autodetected (or immediately if this has already happened).
650
651If called in scalar or list context, then it creates and returns an object
652that automatically removes the callback again when it is destroyed. See
653L<Coro::BDB> for a case where this is useful.
654
655=item @AnyEvent::post_detect
656
657If there are any code references in this array (you can C<push> to it
658before or after loading AnyEvent), then they will called directly after
659the event loop has been chosen.
660
661You should check C<$AnyEvent::MODEL> before adding to this array, though:
662if it contains a true value then the event loop has already been detected,
663and the array will be ignored.
664
665Best use C<AnyEvent::post_detect { BLOCK }> instead.
666
439=back 667=back
440 668
441=head1 WHAT TO DO IN A MODULE 669=head1 WHAT TO DO IN A MODULE
442 670
443As a module author, you should C<use AnyEvent> and call AnyEvent methods 671As a module author, you should C<use AnyEvent> and call AnyEvent methods
446Be careful when you create watchers in the module body - AnyEvent will 674Be careful when you create watchers in the module body - AnyEvent will
447decide which event module to use as soon as the first method is called, so 675decide which event module to use as soon as the first method is called, so
448by calling AnyEvent in your module body you force the user of your module 676by calling AnyEvent in your module body you force the user of your module
449to load the event module first. 677to load the event module first.
450 678
451Never call C<< ->wait >> on a condition variable unless you I<know> that 679Never call C<< ->recv >> on a condition variable unless you I<know> that
452the C<< ->broadcast >> method has been called on it already. This is 680the C<< ->send >> method has been called on it already. This is
453because it will stall the whole program, and the whole point of using 681because it will stall the whole program, and the whole point of using
454events is to stay interactive. 682events is to stay interactive.
455 683
456It is fine, however, to call C<< ->wait >> when the user of your module 684It is fine, however, to call C<< ->recv >> when the user of your module
457requests it (i.e. if you create a http request object ad have a method 685requests it (i.e. if you create a http request object ad have a method
458called C<results> that returns the results, it should call C<< ->wait >> 686called C<results> that returns the results, it should call C<< ->recv >>
459freely, as the user of your module knows what she is doing. always). 687freely, as the user of your module knows what she is doing. always).
460 688
461=head1 WHAT TO DO IN THE MAIN PROGRAM 689=head1 WHAT TO DO IN THE MAIN PROGRAM
462 690
463There will always be a single main program - the only place that should 691There will always be a single main program - the only place that should
465 693
466If it doesn't care, it can just "use AnyEvent" and use it itself, or not 694If it doesn't care, it can just "use AnyEvent" and use it itself, or not
467do anything special (it does not need to be event-based) and let AnyEvent 695do anything special (it does not need to be event-based) and let AnyEvent
468decide which implementation to chose if some module relies on it. 696decide which implementation to chose if some module relies on it.
469 697
470If the main program relies on a specific event model. For example, in 698If the main program relies on a specific event model - for example, in
471Gtk2 programs you have to rely on the Glib module. You should load the 699Gtk2 programs you have to rely on the Glib module - you should load the
472event module before loading AnyEvent or any module that uses it: generally 700event module before loading AnyEvent or any module that uses it: generally
473speaking, you should load it as early as possible. The reason is that 701speaking, you should load it as early as possible. The reason is that
474modules might create watchers when they are loaded, and AnyEvent will 702modules might create watchers when they are loaded, and AnyEvent will
475decide on the event model to use as soon as it creates watchers, and it 703decide on the event model to use as soon as it creates watchers, and it
476might chose the wrong one unless you load the correct one yourself. 704might chose the wrong one unless you load the correct one yourself.
477 705
478You can chose to use a rather inefficient pure-perl implementation by 706You can chose to use a pure-perl implementation by loading the
479loading the C<AnyEvent::Impl::Perl> module, which gives you similar 707C<AnyEvent::Impl::Perl> module, which gives you similar behaviour
480behaviour everywhere, but letting AnyEvent chose is generally better. 708everywhere, but letting AnyEvent chose the model is generally better.
709
710=head2 MAINLOOP EMULATION
711
712Sometimes (often for short test scripts, or even standalone programs who
713only want to use AnyEvent), you do not want to run a specific event loop.
714
715In that case, you can use a condition variable like this:
716
717 AnyEvent->condvar->recv;
718
719This has the effect of entering the event loop and looping forever.
720
721Note that usually your program has some exit condition, in which case
722it is better to use the "traditional" approach of storing a condition
723variable somewhere, waiting for it, and sending it when the program should
724exit cleanly.
725
726
727=head1 OTHER MODULES
728
729The following is a non-exhaustive list of additional modules that use
730AnyEvent and can therefore be mixed easily with other AnyEvent modules
731in the same program. Some of the modules come with AnyEvent, some are
732available via CPAN.
733
734=over 4
735
736=item L<AnyEvent::Util>
737
738Contains various utility functions that replace often-used but blocking
739functions such as C<inet_aton> by event-/callback-based versions.
740
741=item L<AnyEvent::Socket>
742
743Provides various utility functions for (internet protocol) sockets,
744addresses and name resolution. Also functions to create non-blocking tcp
745connections or tcp servers, with IPv6 and SRV record support and more.
746
747=item L<AnyEvent::Handle>
748
749Provide read and write buffers, manages watchers for reads and writes,
750supports raw and formatted I/O, I/O queued and fully transparent and
751non-blocking SSL/TLS.
752
753=item L<AnyEvent::DNS>
754
755Provides rich asynchronous DNS resolver capabilities.
756
757=item L<AnyEvent::HTTP>
758
759A simple-to-use HTTP library that is capable of making a lot of concurrent
760HTTP requests.
761
762=item L<AnyEvent::HTTPD>
763
764Provides a simple web application server framework.
765
766=item L<AnyEvent::FastPing>
767
768The fastest ping in the west.
769
770=item L<AnyEvent::DBI>
771
772Executes L<DBI> requests asynchronously in a proxy process.
773
774=item L<AnyEvent::AIO>
775
776Truly asynchronous I/O, should be in the toolbox of every event
777programmer. AnyEvent::AIO transparently fuses L<IO::AIO> and AnyEvent
778together.
779
780=item L<AnyEvent::BDB>
781
782Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently fuses
783L<BDB> and AnyEvent together.
784
785=item L<AnyEvent::GPSD>
786
787A non-blocking interface to gpsd, a daemon delivering GPS information.
788
789=item L<AnyEvent::IGS>
790
791A non-blocking interface to the Internet Go Server protocol (used by
792L<App::IGS>).
793
794=item L<Net::IRC3>
795
796AnyEvent based IRC client module family.
797
798=item L<Net::XMPP2>
799
800AnyEvent based XMPP (Jabber protocol) module family.
801
802=item L<Net::FCP>
803
804AnyEvent-based implementation of the Freenet Client Protocol, birthplace
805of AnyEvent.
806
807=item L<Event::ExecFlow>
808
809High level API for event-based execution flow control.
810
811=item L<Coro>
812
813Has special support for AnyEvent via L<Coro::AnyEvent>.
814
815=item L<IO::Lambda>
816
817The lambda approach to I/O - don't ask, look there. Can use AnyEvent.
818
819=back
481 820
482=cut 821=cut
483 822
484package AnyEvent; 823package AnyEvent;
485 824
486no warnings; 825no warnings;
487use strict; 826use strict;
488 827
489use Carp; 828use Carp;
490 829
491our $VERSION = '3.3'; 830our $VERSION = 4.2;
492our $MODEL; 831our $MODEL;
493 832
494our $AUTOLOAD; 833our $AUTOLOAD;
495our @ISA; 834our @ISA;
496 835
836our @REGISTRY;
837
838our $WIN32;
839
840BEGIN {
841 my $win32 = ! ! ($^O =~ /mswin32/i);
842 eval "sub WIN32(){ $win32 }";
843}
844
497our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1; 845our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
498 846
499our @REGISTRY; 847our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
848
849{
850 my $idx;
851 $PROTOCOL{$_} = ++$idx
852 for reverse split /\s*,\s*/,
853 $ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
854}
500 855
501my @models = ( 856my @models = (
502 [Coro::EV:: => AnyEvent::Impl::CoroEV::],
503 [Coro::Event:: => AnyEvent::Impl::CoroEvent::],
504 [EV:: => AnyEvent::Impl::EV::], 857 [EV:: => AnyEvent::Impl::EV::],
505 [Event:: => AnyEvent::Impl::Event::], 858 [Event:: => AnyEvent::Impl::Event::],
506 [Glib:: => AnyEvent::Impl::Glib::],
507 [Tk:: => AnyEvent::Impl::Tk::],
508 [Wx:: => AnyEvent::Impl::POE::],
509 [Prima:: => AnyEvent::Impl::POE::],
510 [AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::], 859 [AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
511 # everything below here will not be autoprobed as the pureperl backend should work everywhere 860 # everything below here will not be autoprobed
861 # as the pureperl backend should work everywhere
862 # and is usually faster
863 [Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
864 [Glib:: => AnyEvent::Impl::Glib::], # becomes extremely slow with many watchers
512 [Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy 865 [Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
513 [Qt:: => AnyEvent::Impl::Qt::], # requires special main program 866 [Qt:: => AnyEvent::Impl::Qt::], # requires special main program
514 [POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza 867 [POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
868 [Wx:: => AnyEvent::Impl::POE::],
869 [Prima:: => AnyEvent::Impl::POE::],
515); 870);
516 871
517our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY); 872our %method = map +($_ => 1), qw(io timer time now signal child condvar one_event DESTROY);
873
874our @post_detect;
875
876sub post_detect(&) {
877 my ($cb) = @_;
878
879 if ($MODEL) {
880 $cb->();
881
882 1
883 } else {
884 push @post_detect, $cb;
885
886 defined wantarray
887 ? bless \$cb, "AnyEvent::Util::PostDetect"
888 : ()
889 }
890}
891
892sub AnyEvent::Util::PostDetect::DESTROY {
893 @post_detect = grep $_ != ${$_[0]}, @post_detect;
894}
518 895
519sub detect() { 896sub detect() {
520 unless ($MODEL) { 897 unless ($MODEL) {
521 no strict 'refs'; 898 no strict 'refs';
899 local $SIG{__DIE__};
522 900
523 if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) { 901 if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
524 my $model = "AnyEvent::Impl::$1"; 902 my $model = "AnyEvent::Impl::$1";
525 if (eval "require $model") { 903 if (eval "require $model") {
526 $MODEL = $model; 904 $MODEL = $model;
556 last; 934 last;
557 } 935 }
558 } 936 }
559 937
560 $MODEL 938 $MODEL
561 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."; 939 or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.";
562 } 940 }
563 } 941 }
564 942
565 unshift @ISA, $MODEL; 943 unshift @ISA, $MODEL;
566 push @{"$MODEL\::ISA"}, "AnyEvent::Base"; 944 push @{"$MODEL\::ISA"}, "AnyEvent::Base";
945
946 (shift @post_detect)->() while @post_detect;
567 } 947 }
568 948
569 $MODEL 949 $MODEL
570} 950}
571 951
581 $class->$func (@_); 961 $class->$func (@_);
582} 962}
583 963
584package AnyEvent::Base; 964package AnyEvent::Base;
585 965
966# default implementation for now and time
967
968use Time::HiRes ();
969
970sub time { Time::HiRes::time }
971sub now { Time::HiRes::time }
972
586# default implementation for ->condvar, ->wait, ->broadcast 973# default implementation for ->condvar
587 974
588sub condvar { 975sub condvar {
589 bless \my $flag, "AnyEvent::Base::CondVar" 976 bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, AnyEvent::CondVar::
590}
591
592sub AnyEvent::Base::CondVar::broadcast {
593 ${$_[0]}++;
594}
595
596sub AnyEvent::Base::CondVar::wait {
597 AnyEvent->one_event while !${$_[0]};
598} 977}
599 978
600# default implementation for ->signal 979# default implementation for ->signal
601 980
602our %SIG_CB; 981our %SIG_CB;
618sub AnyEvent::Base::Signal::DESTROY { 997sub AnyEvent::Base::Signal::DESTROY {
619 my ($signal, $cb) = @{$_[0]}; 998 my ($signal, $cb) = @{$_[0]};
620 999
621 delete $SIG_CB{$signal}{$cb}; 1000 delete $SIG_CB{$signal}{$cb};
622 1001
623 $SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} }; 1002 delete $SIG{$signal} unless keys %{ $SIG_CB{$signal} };
624} 1003}
625 1004
626# default implementation for ->child 1005# default implementation for ->child
627 1006
628our %PID_CB; 1007our %PID_CB;
655 or Carp::croak "required option 'pid' is missing"; 1034 or Carp::croak "required option 'pid' is missing";
656 1035
657 $PID_CB{$pid}{$arg{cb}} = $arg{cb}; 1036 $PID_CB{$pid}{$arg{cb}} = $arg{cb};
658 1037
659 unless ($WNOHANG) { 1038 unless ($WNOHANG) {
660 $WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1; 1039 $WNOHANG = eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
661 } 1040 }
662 1041
663 unless ($CHLD_W) { 1042 unless ($CHLD_W) {
664 $CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld); 1043 $CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
665 # child could be a zombie already, so make at least one round 1044 # child could be a zombie already, so make at least one round
675 delete $PID_CB{$pid}{$cb}; 1054 delete $PID_CB{$pid}{$cb};
676 delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} }; 1055 delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
677 1056
678 undef $CHLD_W unless keys %PID_CB; 1057 undef $CHLD_W unless keys %PID_CB;
679} 1058}
1059
1060package AnyEvent::CondVar;
1061
1062our @ISA = AnyEvent::CondVar::Base::;
1063
1064package AnyEvent::CondVar::Base;
1065
1066use overload
1067 '&{}' => sub { my $self = shift; sub { $self->send (@_) } },
1068 fallback => 1;
1069
1070sub _send {
1071 # nop
1072}
1073
1074sub send {
1075 my $cv = shift;
1076 $cv->{_ae_sent} = [@_];
1077 (delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
1078 $cv->_send;
1079}
1080
1081sub croak {
1082 $_[0]{_ae_croak} = $_[1];
1083 $_[0]->send;
1084}
1085
1086sub ready {
1087 $_[0]{_ae_sent}
1088}
1089
1090sub _wait {
1091 AnyEvent->one_event while !$_[0]{_ae_sent};
1092}
1093
1094sub recv {
1095 $_[0]->_wait;
1096
1097 Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};
1098 wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]
1099}
1100
1101sub cb {
1102 $_[0]{_ae_cb} = $_[1] if @_ > 1;
1103 $_[0]{_ae_cb}
1104}
1105
1106sub begin {
1107 ++$_[0]{_ae_counter};
1108 $_[0]{_ae_end_cb} = $_[1] if @_ > 1;
1109}
1110
1111sub end {
1112 return if --$_[0]{_ae_counter};
1113 &{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
1114}
1115
1116# undocumented/compatibility with pre-3.4
1117*broadcast = \&send;
1118*wait = \&_wait;
680 1119
681=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE 1120=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
682 1121
683This is an advanced topic that you do not normally need to use AnyEvent in 1122This is an advanced topic that you do not normally need to use AnyEvent in
684a module. This section is only of use to event loop authors who want to 1123a module. This section is only of use to event loop authors who want to
741model it chooses. 1180model it chooses.
742 1181
743=item C<PERL_ANYEVENT_MODEL> 1182=item C<PERL_ANYEVENT_MODEL>
744 1183
745This can be used to specify the event model to be used by AnyEvent, before 1184This can be used to specify the event model to be used by AnyEvent, before
746autodetection and -probing kicks in. It must be a string consisting 1185auto detection and -probing kicks in. It must be a string consisting
747entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended 1186entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
748and the resulting module name is loaded and if the load was successful, 1187and the resulting module name is loaded and if the load was successful,
749used as event model. If it fails to load AnyEvent will proceed with 1188used as event model. If it fails to load AnyEvent will proceed with
750autodetection and -probing. 1189auto detection and -probing.
751 1190
752This functionality might change in future versions. 1191This functionality might change in future versions.
753 1192
754For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you 1193For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
755could start your program like this: 1194could start your program like this:
756 1195
757 PERL_ANYEVENT_MODEL=Perl perl ... 1196 PERL_ANYEVENT_MODEL=Perl perl ...
1197
1198=item C<PERL_ANYEVENT_PROTOCOLS>
1199
1200Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
1201for IPv4 or IPv6. The default is unspecified (and might change, or be the result
1202of auto probing).
1203
1204Must be set to a comma-separated list of protocols or address families,
1205current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
1206used, and preference will be given to protocols mentioned earlier in the
1207list.
1208
1209This variable can effectively be used for denial-of-service attacks
1210against local programs (e.g. when setuid), although the impact is likely
1211small, as the program has to handle connection errors already-
1212
1213Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
1214but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
1215- only support IPv4, never try to resolve or contact IPv6
1216addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
1217IPv6, but prefer IPv6 over IPv4.
1218
1219=item C<PERL_ANYEVENT_EDNS0>
1220
1221Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
1222for DNS. This extension is generally useful to reduce DNS traffic, but
1223some (broken) firewalls drop such DNS packets, which is why it is off by
1224default.
1225
1226Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
1227EDNS0 in its DNS requests.
1228
1229=item C<PERL_ANYEVENT_MAX_FORKS>
1230
1231The maximum number of child processes that C<AnyEvent::Util::fork_call>
1232will create in parallel.
758 1233
759=back 1234=back
760 1235
761=head1 EXAMPLE PROGRAM 1236=head1 EXAMPLE PROGRAM
762 1237
773 poll => 'r', 1248 poll => 'r',
774 cb => sub { 1249 cb => sub {
775 warn "io event <$_[0]>\n"; # will always output <r> 1250 warn "io event <$_[0]>\n"; # will always output <r>
776 chomp (my $input = <STDIN>); # read a line 1251 chomp (my $input = <STDIN>); # read a line
777 warn "read: $input\n"; # output what has been read 1252 warn "read: $input\n"; # output what has been read
778 $cv->broadcast if $input =~ /^q/i; # quit program if /^q/i 1253 $cv->send if $input =~ /^q/i; # quit program if /^q/i
779 }, 1254 },
780 ); 1255 );
781 1256
782 my $time_watcher; # can only be used once 1257 my $time_watcher; # can only be used once
783 1258
788 }); 1263 });
789 } 1264 }
790 1265
791 new_timer; # create first timer 1266 new_timer; # create first timer
792 1267
793 $cv->wait; # wait until user enters /^q/i 1268 $cv->recv; # wait until user enters /^q/i
794 1269
795=head1 REAL-WORLD EXAMPLE 1270=head1 REAL-WORLD EXAMPLE
796 1271
797Consider the L<Net::FCP> module. It features (among others) the following 1272Consider the L<Net::FCP> module. It features (among others) the following
798API calls, which are to freenet what HTTP GET requests are to http: 1273API calls, which are to freenet what HTTP GET requests are to http:
848 syswrite $txn->{fh}, $txn->{request} 1323 syswrite $txn->{fh}, $txn->{request}
849 or die "connection or write error"; 1324 or die "connection or write error";
850 $txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r }); 1325 $txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
851 1326
852Again, C<fh_ready_r> waits till all data has arrived, and then stores the 1327Again, C<fh_ready_r> waits till all data has arrived, and then stores the
853result and signals any possible waiters that the request ahs finished: 1328result and signals any possible waiters that the request has finished:
854 1329
855 sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf}; 1330 sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
856 1331
857 if (end-of-file or data complete) { 1332 if (end-of-file or data complete) {
858 $txn->{result} = $txn->{buf}; 1333 $txn->{result} = $txn->{buf};
859 $txn->{finished}->broadcast; 1334 $txn->{finished}->send;
860 $txb->{cb}->($txn) of $txn->{cb}; # also call callback 1335 $txb->{cb}->($txn) of $txn->{cb}; # also call callback
861 } 1336 }
862 1337
863The C<result> method, finally, just waits for the finished signal (if the 1338The C<result> method, finally, just waits for the finished signal (if the
864request was already finished, it doesn't wait, of course, and returns the 1339request was already finished, it doesn't wait, of course, and returns the
865data: 1340data:
866 1341
867 $txn->{finished}->wait; 1342 $txn->{finished}->recv;
868 return $txn->{result}; 1343 return $txn->{result};
869 1344
870The actual code goes further and collects all errors (C<die>s, exceptions) 1345The actual code goes further and collects all errors (C<die>s, exceptions)
871that occured during request processing. The C<result> method detects 1346that occurred during request processing. The C<result> method detects
872whether an exception as thrown (it is stored inside the $txn object) 1347whether an exception as thrown (it is stored inside the $txn object)
873and just throws the exception, which means connection errors and other 1348and just throws the exception, which means connection errors and other
874problems get reported tot he code that tries to use the result, not in a 1349problems get reported tot he code that tries to use the result, not in a
875random callback. 1350random callback.
876 1351
907 1382
908 my $quit = AnyEvent->condvar; 1383 my $quit = AnyEvent->condvar;
909 1384
910 $fcp->txn_client_get ($url)->cb (sub { 1385 $fcp->txn_client_get ($url)->cb (sub {
911 ... 1386 ...
912 $quit->broadcast; 1387 $quit->send;
913 }); 1388 });
914 1389
915 $quit->wait; 1390 $quit->recv;
916 1391
917 1392
918=head1 BENCHMARKS 1393=head1 BENCHMARKS
919 1394
920To give you an idea of the performance and overheads that AnyEvent adds 1395To give you an idea of the performance and overheads that AnyEvent adds
922of various event loops I prepared some benchmarks. 1397of various event loops I prepared some benchmarks.
923 1398
924=head2 BENCHMARKING ANYEVENT OVERHEAD 1399=head2 BENCHMARKING ANYEVENT OVERHEAD
925 1400
926Here is a benchmark of various supported event models used natively and 1401Here is a benchmark of various supported event models used natively and
927through anyevent. The benchmark creates a lot of timers (with a zero 1402through AnyEvent. The benchmark creates a lot of timers (with a zero
928timeout) and I/O watchers (watching STDOUT, a pty, to become writable, 1403timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
929which it is), lets them fire exactly once and destroys them again. 1404which it is), lets them fire exactly once and destroys them again.
930 1405
931Source code for this benchmark is found as F<eg/bench> in the AnyEvent 1406Source code for this benchmark is found as F<eg/bench> in the AnyEvent
932distribution. 1407distribution.
949all watchers, to avoid adding memory overhead. That means closure creation 1424all watchers, to avoid adding memory overhead. That means closure creation
950and memory usage is not included in the figures. 1425and memory usage is not included in the figures.
951 1426
952I<invoke> is the time, in microseconds, used to invoke a simple 1427I<invoke> is the time, in microseconds, used to invoke a simple
953callback. The callback simply counts down a Perl variable and after it was 1428callback. The callback simply counts down a Perl variable and after it was
954invoked "watcher" times, it would C<< ->broadcast >> a condvar once to 1429invoked "watcher" times, it would C<< ->send >> a condvar once to
955signal the end of this phase. 1430signal the end of this phase.
956 1431
957I<destroy> is the time, in microseconds, that it takes to destroy a single 1432I<destroy> is the time, in microseconds, that it takes to destroy a single
958watcher. 1433watcher.
959 1434
1019file descriptor is dup()ed for each watcher. This shows that the dup() 1494file descriptor is dup()ed for each watcher. This shows that the dup()
1020employed by some adaptors is not a big performance issue (it does incur a 1495employed by some adaptors is not a big performance issue (it does incur a
1021hidden memory cost inside the kernel which is not reflected in the figures 1496hidden memory cost inside the kernel which is not reflected in the figures
1022above). 1497above).
1023 1498
1024C<POE>, regardless of underlying event loop (whether using its pure 1499C<POE>, regardless of underlying event loop (whether using its pure perl
1025perl select-based backend or the Event module, the POE-EV backend 1500select-based backend or the Event module, the POE-EV backend couldn't
1026couldn't be tested because it wasn't working) shows abysmal performance 1501be tested because it wasn't working) shows abysmal performance and
1027and memory usage: Watchers use almost 30 times as much memory as 1502memory usage with AnyEvent: Watchers use almost 30 times as much memory
1028EV watchers, and 10 times as much memory as Event (the high memory 1503as EV watchers, and 10 times as much memory as Event (the high memory
1029requirements are caused by requiring a session for each watcher). Watcher 1504requirements are caused by requiring a session for each watcher). Watcher
1030invocation speed is almost 900 times slower than with AnyEvent's pure perl 1505invocation speed is almost 900 times slower than with AnyEvent's pure perl
1506implementation.
1507
1031implementation. The design of the POE adaptor class in AnyEvent can not 1508The design of the POE adaptor class in AnyEvent can not really account
1032really account for this, as session creation overhead is small compared 1509for the performance issues, though, as session creation overhead is
1033to execution of the state machine, which is coded pretty optimally within 1510small compared to execution of the state machine, which is coded pretty
1034L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow. 1511optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that
1512using multiple sessions is not a good approach, especially regarding
1513memory usage, even the author of POE could not come up with a faster
1514design).
1035 1515
1036=head3 Summary 1516=head3 Summary
1037 1517
1038=over 4 1518=over 4
1039 1519
1050 1530
1051=back 1531=back
1052 1532
1053=head2 BENCHMARKING THE LARGE SERVER CASE 1533=head2 BENCHMARKING THE LARGE SERVER CASE
1054 1534
1055This benchmark atcually benchmarks the event loop itself. It works by 1535This benchmark actually benchmarks the event loop itself. It works by
1056creating a number of "servers": each server consists of a socketpair, a 1536creating a number of "servers": each server consists of a socket pair, a
1057timeout watcher that gets reset on activity (but never fires), and an I/O 1537timeout watcher that gets reset on activity (but never fires), and an I/O
1058watcher waiting for input on one side of the socket. Each time the socket 1538watcher waiting for input on one side of the socket. Each time the socket
1059watcher reads a byte it will write that byte to a random other "server". 1539watcher reads a byte it will write that byte to a random other "server".
1060 1540
1061The effect is that there will be a lot of I/O watchers, only part of which 1541The effect is that there will be a lot of I/O watchers, only part of which
1062are active at any one point (so there is a constant number of active 1542are active at any one point (so there is a constant number of active
1063fds for each loop iterstaion, but which fds these are is random). The 1543fds for each loop iteration, but which fds these are is random). The
1064timeout is reset each time something is read because that reflects how 1544timeout is reset each time something is read because that reflects how
1065most timeouts work (and puts extra pressure on the event loops). 1545most timeouts work (and puts extra pressure on the event loops).
1066 1546
1067In this benchmark, we use 10000 socketpairs (20000 sockets), of which 100 1547In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
1068(1%) are active. This mirrors the activity of large servers with many 1548(1%) are active. This mirrors the activity of large servers with many
1069connections, most of which are idle at any one point in time. 1549connections, most of which are idle at any one point in time.
1070 1550
1071Source code for this benchmark is found as F<eg/bench2> in the AnyEvent 1551Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
1072distribution. 1552distribution.
1074=head3 Explanation of the columns 1554=head3 Explanation of the columns
1075 1555
1076I<sockets> is the number of sockets, and twice the number of "servers" (as 1556I<sockets> is the number of sockets, and twice the number of "servers" (as
1077each server has a read and write socket end). 1557each server has a read and write socket end).
1078 1558
1079I<create> is the time it takes to create a socketpair (which is 1559I<create> is the time it takes to create a socket pair (which is
1080nontrivial) and two watchers: an I/O watcher and a timeout watcher. 1560nontrivial) and two watchers: an I/O watcher and a timeout watcher.
1081 1561
1082I<request>, the most important value, is the time it takes to handle a 1562I<request>, the most important value, is the time it takes to handle a
1083single "request", that is, reading the token from the pipe and forwarding 1563single "request", that is, reading the token from the pipe and forwarding
1084it to another server. This includes deleting the old timeout and creating 1564it to another server. This includes deleting the old timeout and creating
1086 1566
1087=head3 Results 1567=head3 Results
1088 1568
1089 name sockets create request 1569 name sockets create request
1090 EV 20000 69.01 11.16 1570 EV 20000 69.01 11.16
1091 Perl 20000 75.28 112.76 1571 Perl 20000 73.32 35.87
1092 Event 20000 212.62 257.32 1572 Event 20000 212.62 257.32
1093 Glib 20000 651.16 1896.30 1573 Glib 20000 651.16 1896.30
1094 POE 20000 349.67 12317.24 uses POE::Loop::Event 1574 POE 20000 349.67 12317.24 uses POE::Loop::Event
1095 1575
1096=head3 Discussion 1576=head3 Discussion
1118 1598
1119=head3 Summary 1599=head3 Summary
1120 1600
1121=over 4 1601=over 4
1122 1602
1123=item * The pure perl implementation performs extremely well, considering 1603=item * The pure perl implementation performs extremely well.
1124that it uses select.
1125 1604
1126=item * Avoid Glib or POE in large projects where performance matters. 1605=item * Avoid Glib or POE in large projects where performance matters.
1127 1606
1128=back 1607=back
1129 1608
1142 1621
1143=head3 Results 1622=head3 Results
1144 1623
1145 name sockets create request 1624 name sockets create request
1146 EV 16 20.00 6.54 1625 EV 16 20.00 6.54
1626 Perl 16 25.75 12.62
1147 Event 16 81.27 35.86 1627 Event 16 81.27 35.86
1148 Glib 16 32.63 15.48 1628 Glib 16 32.63 15.48
1149 Perl 16 24.62 162.37
1150 POE 16 261.87 276.28 uses POE::Loop::Event 1629 POE 16 261.87 276.28 uses POE::Loop::Event
1151 1630
1152=head3 Discussion 1631=head3 Discussion
1153 1632
1154The benchmark tries to test the performance of a typical small 1633The benchmark tries to test the performance of a typical small
1158speed most when you have lots of watchers, not when you only have a few of 1637speed most when you have lots of watchers, not when you only have a few of
1159them). 1638them).
1160 1639
1161EV is again fastest. 1640EV is again fastest.
1162 1641
1163The C-based event loops Event and Glib come in second this time, as the 1642Perl again comes second. It is noticeably faster than the C-based event
1164overhead of running an iteration is much smaller in C than in Perl (little 1643loops Event and Glib, although the difference is too small to really
1165code to execute in the inner loop, and perl's function calling overhead is 1644matter.
1166high, and updating all the data structures is costly).
1167
1168The pure perl event loop is much slower, but still competitive.
1169 1645
1170POE also performs much better in this case, but is is still far behind the 1646POE also performs much better in this case, but is is still far behind the
1171others. 1647others.
1172 1648
1173=head3 Summary 1649=head3 Summary
1181 1657
1182 1658
1183=head1 FORK 1659=head1 FORK
1184 1660
1185Most event libraries are not fork-safe. The ones who are usually are 1661Most event libraries are not fork-safe. The ones who are usually are
1186because they are so inefficient. Only L<EV> is fully fork-aware. 1662because they rely on inefficient but fork-safe C<select> or C<poll>
1663calls. Only L<EV> is fully fork-aware.
1187 1664
1188If you have to fork, you must either do so I<before> creating your first 1665If you have to fork, you must either do so I<before> creating your first
1189watcher OR you must not use AnyEvent at all in the child. 1666watcher OR you must not use AnyEvent at all in the child.
1190 1667
1191 1668
1199specified in the variable. 1676specified in the variable.
1200 1677
1201You can make AnyEvent completely ignore this variable by deleting it 1678You can make AnyEvent completely ignore this variable by deleting it
1202before the first watcher gets created, e.g. with a C<BEGIN> block: 1679before the first watcher gets created, e.g. with a C<BEGIN> block:
1203 1680
1204 BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} } 1681 BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1205 1682
1206 use AnyEvent; 1683 use AnyEvent;
1684
1685Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
1686be used to probe what backend is used and gain other information (which is
1687probably even less useful to an attacker than PERL_ANYEVENT_MODEL).
1688
1689
1690=head1 BUGS
1691
1692Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
1693to work around. If you suffer from memleaks, first upgrade to Perl 5.10
1694and check wether the leaks still show up. (Perl 5.10.0 has other annoying
1695mamleaks, such as leaking on C<map> and C<grep> but it is usually not as
1696pronounced).
1207 1697
1208 1698
1209=head1 SEE ALSO 1699=head1 SEE ALSO
1210 1700
1211Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>, 1701Utility functions: L<AnyEvent::Util>.
1212L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>, 1702
1703Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,
1213L<Event::Lib>, L<Qt>, L<POE>. 1704L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
1214 1705
1215Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>, 1706Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
1216L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>, 1707L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
1217L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>, 1708L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
1218L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>. 1709L<AnyEvent::Impl::POE>.
1219 1710
1711Non-blocking file handles, sockets, TCP clients and
1712servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>.
1713
1714Asynchronous DNS: L<AnyEvent::DNS>.
1715
1716Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>,
1717
1220Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>. 1718Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>, L<AnyEvent::DNS>.
1221 1719
1222 1720
1223=head1 AUTHOR 1721=head1 AUTHOR
1224 1722
1225 Marc Lehmann <schmorp@schmorp.de> 1723 Marc Lehmann <schmorp@schmorp.de>
1226 http://home.schmorp.de/ 1724 http://home.schmorp.de/
1227 1725
1228=cut 1726=cut
1229 1727
12301 17281
1231 1729

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