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Revision 1.17 by root, Fri Nov 24 14:40:13 2006 UTC vs.
Revision 1.70 by root, Fri Apr 25 07:25:44 2008 UTC

1=head1 NAME 1=head1 NAME
2 2
3AnyEvent - provide framework for multiple event loops 3AnyEvent - provide framework for multiple event loops
4 4
5Event, Coro, Glib, Tk, Perl - various supported event loops 5EV, Event, Coro::EV, Coro::Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event loops
6 6
7=head1 SYNOPSIS 7=head1 SYNOPSIS
8 8
9 use AnyEvent; 9 use AnyEvent;
10 10
14 14
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 wether a condition was flagged 19 my $w = AnyEvent->condvar; # stores whether a condition was flagged
20 $w->wait; # enters "main loop" till $condvar gets ->broadcast 20 $w->wait; # enters "main loop" till $condvar gets ->broadcast
21 $w->broadcast; # wake up current and all future wait's 21 $w->broadcast; # wake up current and all future wait's
22
23=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
24
25Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
26nowadays. So what is different about AnyEvent?
27
28Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of
29policy> and AnyEvent is I<small and efficient>.
30
31First and foremost, I<AnyEvent is not an event model> itself, it only
32interfaces to whatever event model the main program happens to use in a
33pragmatic way. For event models and certain classes of immortals alike,
34the statement "there can only be one" is a bitter reality: In general,
35only one event loop can be active at the same time in a process. AnyEvent
36helps hiding the differences between those event loops.
37
38The goal of AnyEvent is to offer module authors the ability to do event
39programming (waiting for I/O or timer events) without subscribing to a
40religion, a way of living, and most importantly: without forcing your
41module users into the same thing by forcing them to use the same event
42model you use.
43
44For modules like POE or IO::Async (which is a total misnomer as it is
45actually doing all I/O I<synchronously>...), using them in your module is
46like joining a cult: After you joined, you are dependent on them and you
47cannot use anything else, as it is simply incompatible to everything that
48isn't itself. What's worse, all the potential users of your module are
49I<also> forced to use the same event loop you use.
50
51AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
52fine. 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
54your 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
56event 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
58event loops to AnyEvent, too, so it is future-proof).
59
60In 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
62modules, you get an enourmous amount of code and strict rules you have to
63follow. 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
65technically possible.
66
67Of course, if you want lots of policy (this can arguably be somewhat
68useful) and you want to force your users to use the one and only event
69model, you should I<not> use this module.
70
22 71
23=head1 DESCRIPTION 72=head1 DESCRIPTION
24 73
25L<AnyEvent> provides an identical interface to multiple event loops. This 74L<AnyEvent> provides an identical interface to multiple event loops. This
26allows module authors to utilise an event loop without forcing module 75allows module authors to utilise an event loop without forcing module
27users to use the same event loop (as only a single event loop can coexist 76users to use the same event loop (as only a single event loop can coexist
28peacefully at any one time). 77peacefully at any one time).
29 78
30The interface itself is vaguely similar but not identical to the Event 79The interface itself is vaguely similar, but not identical to the L<Event>
31module. 80module.
32 81
33On the first call of any method, the module tries to detect the currently 82During the first call of any watcher-creation method, the module tries
34loaded event loop by probing wether any of the following modules is 83to detect the currently loaded event loop by probing whether one of the
35loaded: L<Coro::Event>, L<Event>, L<Glib>, L<Tk>. The first one found is 84following modules is already loaded: L<Coro::EV>, L<Coro::Event>, L<EV>,
36used. If none is found, the module tries to load these modules in the 85L<Event>, L<Glib>, L<Tk>, L<AnyEvent::Impl::Perl>, L<Event::Lib>, L<Qt>,
37order given. The first one that could be successfully loaded will be 86L<POE>. The first one found is used. If none are found, the module tries
38used. If still none could be found, AnyEvent will fall back to a pure-perl 87to load these modules (excluding Event::Lib, Qt and POE as the pure perl
39event loop, which is also not very efficient. 88adaptor 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
90found, AnyEvent will fall back to a pure-perl event loop, which is not
91very efficient, but should work everywhere.
40 92
41Because AnyEvent first checks for modules that are already loaded, loading 93Because AnyEvent first checks for modules that are already loaded, loading
42an Event model explicitly before first using AnyEvent will likely make 94an event model explicitly before first using AnyEvent will likely make
43that model the default. For example: 95that model the default. For example:
44 96
45 use Tk; 97 use Tk;
46 use AnyEvent; 98 use AnyEvent;
47 99
48 # .. AnyEvent will likely default to Tk 100 # .. AnyEvent will likely default to Tk
101
102The I<likely> means that, if any module loads another event model and
103starts using it, all bets are off. Maybe you should tell their authors to
104use AnyEvent so their modules work together with others seamlessly...
49 105
50The pure-perl implementation of AnyEvent is called 106The pure-perl implementation of AnyEvent is called
51C<AnyEvent::Impl::Perl>. Like other event modules you can load it 107C<AnyEvent::Impl::Perl>. Like other event modules you can load it
52explicitly. 108explicitly.
53 109
56AnyEvent has the central concept of a I<watcher>, which is an object that 112AnyEvent has the central concept of a I<watcher>, which is an object that
57stores relevant data for each kind of event you are waiting for, such as 113stores relevant data for each kind of event you are waiting for, such as
58the callback to call, the filehandle to watch, etc. 114the callback to call, the filehandle to watch, etc.
59 115
60These watchers are normal Perl objects with normal Perl lifetime. After 116These watchers are normal Perl objects with normal Perl lifetime. After
61creating a watcher it will immediately "watch" for events and invoke 117creating a watcher it will immediately "watch" for events and invoke the
118callback when the event occurs (of course, only when the event model
119is in control).
120
62the callback. To disable the watcher you have to destroy it (e.g. by 121To disable the watcher you have to destroy it (e.g. by setting the
63setting the variable that stores it to C<undef> or otherwise deleting all 122variable you store it in to C<undef> or otherwise deleting all references
64references to it). 123to it).
65 124
66All watchers are created by calling a method on the C<AnyEvent> class. 125All watchers are created by calling a method on the C<AnyEvent> class.
67 126
127Many watchers either are used with "recursion" (repeating timers for
128example), or need to refer to their watcher object in other ways.
129
130An any way to achieve that is this pattern:
131
132 my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
133 # you can use $w here, for example to undef it
134 undef $w;
135 });
136
137Note that C<my $w; $w => combination. This is necessary because in Perl,
138my variables are only visible after the statement in which they are
139declared.
140
68=head2 IO WATCHERS 141=head2 IO WATCHERS
69 142
70You can create I/O watcher by calling the C<< AnyEvent->io >> method with 143You can create an I/O watcher by calling the C<< AnyEvent->io >> method
71the following mandatory arguments: 144with the following mandatory key-value pairs as arguments:
72 145
73C<fh> the Perl I<filehandle> (not filedescriptor) to watch for 146C<fh> the Perl I<file handle> (I<not> file descriptor) to watch for
74events. C<poll> must be a string that is either C<r> or C<w>, that creates 147events. C<poll> must be a string that is either C<r> or C<w>, which
75a watcher waiting for "r"eadable or "w"ritable events. C<cb> teh callback 148creates a watcher waiting for "r"eadable or "w"ritable events,
76to invoke everytime the filehandle becomes ready. 149respectively. C<cb> is the callback to invoke each time the file handle
150becomes ready.
77 151
78Only one io watcher per C<fh> and C<poll> combination is allowed (i.e. on 152As long as the I/O watcher exists it will keep the file descriptor or a
79a socket you can have one r + one w, not any more (limitation comes from 153copy of it alive/open.
80Tk - if you are sure you are not using Tk this limitation is gone).
81 154
82Filehandles will be kept alive, so as long as the watcher exists, the 155It is not allowed to close a file handle as long as any watcher is active
83filehandle exists, too. 156on the underlying file descriptor.
157
158Some event loops issue spurious readyness notifications, so you should
159always use non-blocking calls when reading/writing from/to your file
160handles.
84 161
85Example: 162Example:
86 163
87 # wait for readability of STDIN, then read a line and disable the watcher 164 # wait for readability of STDIN, then read a line and disable the watcher
88 my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub { 165 my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
89 chomp (my $input = <STDIN>); 166 chomp (my $input = <STDIN>);
90 warn "read: $input\n"; 167 warn "read: $input\n";
91 undef $w; 168 undef $w;
92 }); 169 });
93 170
94=head2 TIMER WATCHERS 171=head2 TIME WATCHERS
95 172
96You can create a timer watcher by calling the C<< AnyEvent->timer >> 173You can create a time watcher by calling the C<< AnyEvent->timer >>
97method with the following mandatory arguments: 174method with the following mandatory arguments:
98 175
99C<after> after how many seconds (fractions are supported) should the timer 176C<after> specifies after how many seconds (fractional values are
100activate. C<cb> the callback to invoke. 177supported) should the timer activate. C<cb> the callback to invoke in that
178case.
101 179
102The timer callback will be invoked at most once: if you want a repeating 180The timer callback will be invoked at most once: if you want a repeating
103timer you have to create a new watcher (this is a limitation by both Tk 181timer you have to create a new watcher (this is a limitation by both Tk
104and Glib). 182and Glib).
105 183
109 my $w = AnyEvent->timer (after => 7.7, cb => sub { 187 my $w = AnyEvent->timer (after => 7.7, cb => sub {
110 warn "timeout\n"; 188 warn "timeout\n";
111 }); 189 });
112 190
113 # to cancel the timer: 191 # to cancel the timer:
114 undef $w 192 undef $w;
115 193
194Example 2:
195
196 # fire an event after 0.5 seconds, then roughly every second
197 my $w;
198
199 my $cb = sub {
200 # cancel the old timer while creating a new one
201 $w = AnyEvent->timer (after => 1, cb => $cb);
202 };
203
204 # start the "loop" by creating the first watcher
205 $w = AnyEvent->timer (after => 0.5, cb => $cb);
206
207=head3 TIMING ISSUES
208
209There are two ways to handle timers: based on real time (relative, "fire
210in 10 seconds") and based on wallclock time (absolute, "fire at 12
211o'clock").
212
213While most event loops expect timers to specified in a relative way, they
214use absolute time internally. This makes a difference when your clock
215"jumps", for example, when ntp decides to set your clock backwards from
216the wrong date of 2014-01-01 to 2008-01-01, a watcher that is supposed to
217fire "after" a second might actually take six years to finally fire.
218
219AnyEvent cannot compensate for this. The only event loop that is conscious
220about these issues is L<EV>, which offers both relative (ev_timer, based
221on true relative time) and absolute (ev_periodic, based on wallclock time)
222timers.
223
224AnyEvent always prefers relative timers, if available, matching the
225AnyEvent API.
226
227=head2 SIGNAL WATCHERS
228
229You can watch for signals using a signal watcher, C<signal> is the signal
230I<name> without any C<SIG> prefix, C<cb> is the Perl callback to
231be invoked whenever a signal occurs.
232
233Multiple signal occurances can be clumped together into one callback
234invocation, and callback invocation will be synchronous. synchronous means
235that it might take a while until the signal gets handled by the process,
236but it is guarenteed not to interrupt any other callbacks.
237
238The main advantage of using these watchers is that you can share a signal
239between multiple watchers.
240
241This watcher might use C<%SIG>, so programs overwriting those signals
242directly will likely not work correctly.
243
244Example: exit on SIGINT
245
246 my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
247
248=head2 CHILD PROCESS WATCHERS
249
250You can also watch on a child process exit and catch its exit status.
251
252The child process is specified by the C<pid> argument (if set to C<0>, it
253watches for any child process exit). The watcher will trigger as often
254as status change for the child are received. This works by installing a
255signal handler for C<SIGCHLD>. The callback will be called with the pid
256and exit status (as returned by waitpid).
257
258Example: wait for pid 1333
259
260 my $w = AnyEvent->child (
261 pid => 1333,
262 cb => sub {
263 my ($pid, $status) = @_;
264 warn "pid $pid exited with status $status";
265 },
266 );
267
116=head2 CONDITION WATCHERS 268=head2 CONDITION VARIABLES
117 269
118Condition watchers can be created by calling the C<< AnyEvent->condvar >> 270Condition variables can be created by calling the C<< AnyEvent->condvar >>
119method without any arguments. 271method without any arguments.
120 272
121A condition watcher watches for a condition - precisely that the C<< 273A condition variable waits for a condition - precisely that the C<<
122->broadcast >> method has been called. 274->broadcast >> method has been called.
123 275
124The watcher has only two methods: 276They are very useful to signal that a condition has been fulfilled, for
277example, if you write a module that does asynchronous http requests,
278then a condition variable would be the ideal candidate to signal the
279availability of results.
280
281You can also use condition variables to block your main program until
282an event occurs - for example, you could C<< ->wait >> in your main
283program until the user clicks the Quit button in your app, which would C<<
284->broadcast >> the "quit" event.
285
286Note that condition variables recurse into the event loop - if you have
287two pirces of code that call C<< ->wait >> in a round-robbin fashion, you
288lose. Therefore, condition variables are good to export to your caller, but
289you should avoid making a blocking wait yourself, at least in callbacks,
290as this asks for trouble.
291
292This object has two methods:
125 293
126=over 4 294=over 4
127 295
128=item $cv->wait 296=item $cv->wait
129 297
130Wait (blocking if necessary) until the C<< ->broadcast >> method has been 298Wait (blocking if necessary) until the C<< ->broadcast >> method has been
131called on c<$cv>, while servicing other watchers normally. 299called on c<$cv>, while servicing other watchers normally.
132 300
133Not all event models support a blocking wait - some die in that case, so
134if you are using this from a module, never require a blocking wait, but
135let the caller decide wether the call will block or not (for example,
136by coupling condition variables with some kind of request results and
137supporting callbacks so the caller knows that getting the result will not
138block, while still suppporting blockign waits if the caller so desires).
139
140You can only wait once on a condition - additional calls will return 301You can only wait once on a condition - additional calls will return
141immediately. 302immediately.
142 303
304Not all event models support a blocking wait - some die in that case
305(programs might want to do that to stay interactive), so I<if you are
306using this from a module, never require a blocking wait>, but let the
307caller decide whether the call will block or not (for example, by coupling
308condition variables with some kind of request results and supporting
309callbacks so the caller knows that getting the result will not block,
310while still suppporting blocking waits if the caller so desires).
311
312Another reason I<never> to C<< ->wait >> in a module is that you cannot
313sensibly have two C<< ->wait >>'s in parallel, as that would require
314multiple interpreters or coroutines/threads, none of which C<AnyEvent>
315can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and
316L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
317from different coroutines, however).
318
143=item $cv->broadcast 319=item $cv->broadcast
144 320
145Flag the condition as ready - a running C<< ->wait >> and all further 321Flag the condition as ready - a running C<< ->wait >> and all further
146calls to C<wait> will return after this method has been called. If nobody 322calls to C<wait> will (eventually) return after this method has been
147is waiting the broadcast will be remembered.. 323called. If nobody is waiting the broadcast will be remembered..
324
325=back
148 326
149Example: 327Example:
150 328
151 # wait till the result is ready 329 # wait till the result is ready
152 my $result_ready = AnyEvent->condvar; 330 my $result_ready = AnyEvent->condvar;
153 331
154 # do something such as adding a timer 332 # do something such as adding a timer
155 # or socket watcher the calls $result_ready->broadcast 333 # or socket watcher the calls $result_ready->broadcast
156 # when the "result" is ready. 334 # when the "result" is ready.
335 # in this case, we simply use a timer:
336 my $w = AnyEvent->timer (
337 after => 1,
338 cb => sub { $result_ready->broadcast },
339 );
157 340
341 # this "blocks" (while handling events) till the watcher
342 # calls broadcast
158 $result_ready->wait; 343 $result_ready->wait;
159 344
160=back 345=head1 GLOBAL VARIABLES AND FUNCTIONS
161
162=head1 GLOBALS
163 346
164=over 4 347=over 4
165 348
166=item $AnyEvent::MODEL 349=item $AnyEvent::MODEL
167 350
171C<AnyEvent::Impl:xxx> modules, but can be any other class in the case 354C<AnyEvent::Impl:xxx> modules, but can be any other class in the case
172AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>). 355AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).
173 356
174The known classes so far are: 357The known classes so far are:
175 358
176 AnyEvent::Impl::Coro based on Coro::Event, best choise. 359 AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
360 AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
361 AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
177 AnyEvent::Impl::Event based on Event, also best choice :) 362 AnyEvent::Impl::Event based on Event, second best choice.
178 AnyEvent::Impl::Glib based on Glib, second-best choice. 363 AnyEvent::Impl::Glib based on Glib, third-best choice.
179 AnyEvent::Impl::Tk based on Tk, very bad choice. 364 AnyEvent::Impl::Tk based on Tk, very bad choice.
180 AnyEvent::Impl::Perl pure-perl implementation, inefficient. 365 AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
366 AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
367 AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
368 AnyEvent::Impl::POE based on POE, not generic enough for full support.
369
370There is no support for WxWidgets, as WxWidgets has no support for
371watching file handles. However, you can use WxWidgets through the
372POE Adaptor, as POE has a Wx backend that simply polls 20 times per
373second, which was considered to be too horrible to even consider for
374AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
375it's adaptor.
376
377AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
378autodetecting them.
379
380=item AnyEvent::detect
381
382Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
383if necessary. You should only call this function right before you would
384have created an AnyEvent watcher anyway, that is, as late as possible at
385runtime.
181 386
182=back 387=back
183 388
184=head1 WHAT TO DO IN A MODULE 389=head1 WHAT TO DO IN A MODULE
185 390
186As a module author, you should "use AnyEvent" and call AnyEvent methods 391As a module author, you should C<use AnyEvent> and call AnyEvent methods
187freely, but you should not load a specific event module or rely on it. 392freely, but you should not load a specific event module or rely on it.
188 393
189Be careful when you create watchers in the module body - Anyevent will 394Be careful when you create watchers in the module body - AnyEvent will
190decide which event module to use as soon as the first method is called, so 395decide which event module to use as soon as the first method is called, so
191by calling AnyEvent in your module body you force the user of your module 396by calling AnyEvent in your module body you force the user of your module
192to load the event module first. 397to load the event module first.
193 398
399Never call C<< ->wait >> on a condition variable unless you I<know> that
400the C<< ->broadcast >> method has been called on it already. This is
401because it will stall the whole program, and the whole point of using
402events is to stay interactive.
403
404It is fine, however, to call C<< ->wait >> when the user of your module
405requests it (i.e. if you create a http request object ad have a method
406called C<results> that returns the results, it should call C<< ->wait >>
407freely, as the user of your module knows what she is doing. always).
408
194=head1 WHAT TO DO IN THE MAIN PROGRAM 409=head1 WHAT TO DO IN THE MAIN PROGRAM
195 410
196There will always be a single main program - the only place that should 411There will always be a single main program - the only place that should
197dictate which event model to use. 412dictate which event model to use.
198 413
199If it doesn't care, it can just "use AnyEvent" and use it itself, or not 414If it doesn't care, it can just "use AnyEvent" and use it itself, or not
200do anything special and let AnyEvent decide which implementation to chose. 415do anything special (it does not need to be event-based) and let AnyEvent
416decide which implementation to chose if some module relies on it.
201 417
202If the main program relies on a specific event model (for example, in Gtk2 418If the main program relies on a specific event model. For example, in
203programs you have to rely on either Glib or Glib::Event), you should load 419Gtk2 programs you have to rely on the Glib module. You should load the
204it before loading AnyEvent or any module that uses it, generally, as early 420event module before loading AnyEvent or any module that uses it: generally
205as possible. The reason is that modules might create watchers when they 421speaking, you should load it as early as possible. The reason is that
206are loaded, and AnyEvent will decide on the event model to use as soon as 422modules might create watchers when they are loaded, and AnyEvent will
207it creates watchers, and it might chose the wrong one unless you load the 423decide on the event model to use as soon as it creates watchers, and it
208correct one yourself. 424might chose the wrong one unless you load the correct one yourself.
209 425
210You can chose to use a rather inefficient pure-perl implementation by 426You can chose to use a rather inefficient pure-perl implementation by
211loading the C<AnyEvent::Impl::Perl> module, but letting AnyEvent chose is 427loading the C<AnyEvent::Impl::Perl> module, which gives you similar
212generally better. 428behaviour everywhere, but letting AnyEvent chose is generally better.
213 429
214=cut 430=cut
215 431
216package AnyEvent; 432package AnyEvent;
217 433
218no warnings; 434no warnings;
219use strict 'vars'; 435use strict;
436
220use Carp; 437use Carp;
221 438
222our $VERSION = '2.1'; 439our $VERSION = '3.3';
223our $MODEL; 440our $MODEL;
224 441
225our $AUTOLOAD; 442our $AUTOLOAD;
226our @ISA; 443our @ISA;
227 444
228our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1; 445our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
229 446
230our @REGISTRY; 447our @REGISTRY;
231 448
232my @models = ( 449my @models = (
450 [Coro::EV:: => AnyEvent::Impl::CoroEV::],
233 [Coro::Event:: => AnyEvent::Impl::Coro::], 451 [Coro::Event:: => AnyEvent::Impl::CoroEvent::],
452 [EV:: => AnyEvent::Impl::EV::],
234 [Event:: => AnyEvent::Impl::Event::], 453 [Event:: => AnyEvent::Impl::Event::],
235 [Glib:: => AnyEvent::Impl::Glib::], 454 [Glib:: => AnyEvent::Impl::Glib::],
236 [Tk:: => AnyEvent::Impl::Tk::], 455 [Tk:: => AnyEvent::Impl::Tk::],
456 [Wx:: => AnyEvent::Impl::POE::],
457 [Prima:: => AnyEvent::Impl::POE::],
237 [AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::], 458 [AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
459 # everything below here will not be autoprobed as the pureperl backend should work everywhere
460 [Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
461 [Qt:: => AnyEvent::Impl::Qt::], # requires special main program
462 [POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
238); 463);
239 464
240our %method = map +($_ => 1), qw(io timer condvar broadcast wait DESTROY); 465our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY);
241 466
242sub AUTOLOAD { 467sub detect() {
243 $AUTOLOAD =~ s/.*://;
244
245 $method{$AUTOLOAD}
246 or croak "$AUTOLOAD: not a valid method for AnyEvent objects";
247
248 unless ($MODEL) { 468 unless ($MODEL) {
469 no strict 'refs';
470
471 if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
472 my $model = "AnyEvent::Impl::$1";
473 if (eval "require $model") {
474 $MODEL = $model;
475 warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;
476 } else {
477 warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;
478 }
479 }
480
249 # check for already loaded models 481 # check for already loaded models
482 unless ($MODEL) {
250 for (@REGISTRY, @models) { 483 for (@REGISTRY, @models) {
251 my ($package, $model) = @$_; 484 my ($package, $model) = @$_;
252 if (${"$package\::VERSION"} > 0) { 485 if (${"$package\::VERSION"} > 0) {
253 if (eval "require $model") { 486 if (eval "require $model") {
254 $MODEL = $model; 487 $MODEL = $model;
255 warn "AnyEvent: found model '$model', using it.\n" if $verbose > 1; 488 warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;
256 last; 489 last;
490 }
257 } 491 }
258 } 492 }
493
494 unless ($MODEL) {
495 # try to load a model
496
497 for (@REGISTRY, @models) {
498 my ($package, $model) = @$_;
499 if (eval "require $package"
500 and ${"$package\::VERSION"} > 0
501 and eval "require $model") {
502 $MODEL = $model;
503 warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;
504 last;
505 }
506 }
507
508 $MODEL
509 or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV (or Coro+EV), Event (or Coro+Event) or Glib.";
510 }
259 } 511 }
260 512
261 unless ($MODEL) { 513 unshift @ISA, $MODEL;
262 # try to load a model 514 push @{"$MODEL\::ISA"}, "AnyEvent::Base";
263
264 for (@REGISTRY, @models) {
265 my ($package, $model) = @$_;
266 if (eval "require $model") {
267 $MODEL = $model;
268 warn "AnyEvent: autoprobed and loaded model '$model', using it.\n" if $verbose > 1;
269 last;
270 }
271 }
272
273 $MODEL
274 or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: Coro, Event, Glib or Tk.";
275 }
276 } 515 }
277 516
278 @ISA = $MODEL; 517 $MODEL
518}
519
520sub AUTOLOAD {
521 (my $func = $AUTOLOAD) =~ s/.*://;
522
523 $method{$func}
524 or croak "$func: not a valid method for AnyEvent objects";
525
526 detect unless $MODEL;
279 527
280 my $class = shift; 528 my $class = shift;
281 $class->$AUTOLOAD (@_); 529 $class->$func (@_);
282} 530}
283 531
532package AnyEvent::Base;
533
534# default implementation for ->condvar, ->wait, ->broadcast
535
536sub condvar {
537 bless \my $flag, "AnyEvent::Base::CondVar"
538}
539
540sub AnyEvent::Base::CondVar::broadcast {
541 ${$_[0]}++;
542}
543
544sub AnyEvent::Base::CondVar::wait {
545 AnyEvent->one_event while !${$_[0]};
546}
547
548# default implementation for ->signal
549
550our %SIG_CB;
551
552sub signal {
553 my (undef, %arg) = @_;
554
555 my $signal = uc $arg{signal}
556 or Carp::croak "required option 'signal' is missing";
557
558 $SIG_CB{$signal}{$arg{cb}} = $arg{cb};
559 $SIG{$signal} ||= sub {
560 $_->() for values %{ $SIG_CB{$signal} || {} };
561 };
562
563 bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"
564}
565
566sub AnyEvent::Base::Signal::DESTROY {
567 my ($signal, $cb) = @{$_[0]};
568
569 delete $SIG_CB{$signal}{$cb};
570
571 $SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };
572}
573
574# default implementation for ->child
575
576our %PID_CB;
577our $CHLD_W;
578our $CHLD_DELAY_W;
579our $PID_IDLE;
580our $WNOHANG;
581
582sub _child_wait {
583 while (0 < (my $pid = waitpid -1, $WNOHANG)) {
584 $_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),
585 (values %{ $PID_CB{0} || {} });
586 }
587
588 undef $PID_IDLE;
589}
590
591sub _sigchld {
592 # make sure we deliver these changes "synchronous" with the event loop.
593 $CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub {
594 undef $CHLD_DELAY_W;
595 &_child_wait;
596 });
597}
598
599sub child {
600 my (undef, %arg) = @_;
601
602 defined (my $pid = $arg{pid} + 0)
603 or Carp::croak "required option 'pid' is missing";
604
605 $PID_CB{$pid}{$arg{cb}} = $arg{cb};
606
607 unless ($WNOHANG) {
608 $WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;
609 }
610
611 unless ($CHLD_W) {
612 $CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
613 # child could be a zombie already, so make at least one round
614 &_sigchld;
615 }
616
617 bless [$pid, $arg{cb}], "AnyEvent::Base::Child"
618}
619
620sub AnyEvent::Base::Child::DESTROY {
621 my ($pid, $cb) = @{$_[0]};
622
623 delete $PID_CB{$pid}{$cb};
624 delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
625
626 undef $CHLD_W unless keys %PID_CB;
627}
628
284=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE 629=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
630
631This is an advanced topic that you do not normally need to use AnyEvent in
632a module. This section is only of use to event loop authors who want to
633provide AnyEvent compatibility.
285 634
286If you need to support another event library which isn't directly 635If you need to support another event library which isn't directly
287supported by AnyEvent, you can supply your own interface to it by 636supported by AnyEvent, you can supply your own interface to it by
288pushing, before the first watcher gets created, the package name of 637pushing, before the first watcher gets created, the package name of
289the event module and the package name of the interface to use onto 638the event module and the package name of the interface to use onto
290C<@AnyEvent::REGISTRY>. You can do that before and even without loading 639C<@AnyEvent::REGISTRY>. You can do that before and even without loading
291AnyEvent. 640AnyEvent, so it is reasonably cheap.
292 641
293Example: 642Example:
294 643
295 push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::]; 644 push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];
296 645
297This tells AnyEvent to (literally) use the C<urxvt::anyevent::> 646This tells AnyEvent to (literally) use the C<urxvt::anyevent::>
298package/class when it finds the C<urxvt> package/module is loaded. When 647package/class when it finds the C<urxvt> package/module is already loaded.
648
299AnyEvent is loaded and asked to find a suitable event model, it will 649When AnyEvent is loaded and asked to find a suitable event model, it
300first check for the presence of urxvt. 650will first check for the presence of urxvt by trying to C<use> the
651C<urxvt::anyevent> module.
301 652
302The class should prove implementations for all watcher types (see 653The class should provide implementations for all watcher types. See
303L<AnyEvent::Impl::Event> (source code), L<AnyEvent::Impl::Glib> 654L<AnyEvent::Impl::EV> (source code), L<AnyEvent::Impl::Glib> (Source code)
304(Source code) and so on for actual examples, use C<perldoc -m 655and so on for actual examples. Use C<perldoc -m AnyEvent::Impl::Glib> to
305AnyEvent::Impl::Glib> to see the sources). 656see the sources.
306 657
658If you don't provide C<signal> and C<child> watchers than AnyEvent will
659provide suitable (hopefully) replacements.
660
307The above isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt) 661The above example isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt)
308uses the above line as-is. An interface isn't included in AnyEvent 662terminal emulator uses the above line as-is. An interface isn't included
309because it doesn't make sense outside the embedded interpreter inside 663in AnyEvent because it doesn't make sense outside the embedded interpreter
310I<rxvt-unicode>, and it is updated and maintained as part of the 664inside I<rxvt-unicode>, and it is updated and maintained as part of the
311I<rxvt-unicode> distribution. 665I<rxvt-unicode> distribution.
312 666
313I<rxvt-unicode> also cheats a bit by not providing blocking access to 667I<rxvt-unicode> also cheats a bit by not providing blocking access to
314condition variables: code blocking while waiting for a condition will 668condition variables: code blocking while waiting for a condition will
315C<die>. This still works with most modules/usages, and blocking calls must 669C<die>. This still works with most modules/usages, and blocking calls must
316not be in an interactive appliation, so it makes sense. 670not be done in an interactive application, so it makes sense.
317 671
318=head1 ENVIRONMENT VARIABLES 672=head1 ENVIRONMENT VARIABLES
319 673
320The following environment variables are used by this module: 674The following environment variables are used by this module:
321 675
322C<PERL_ANYEVENT_VERBOSE> when set to C<2> or higher, reports which event 676=over 4
323model gets used.
324 677
678=item C<PERL_ANYEVENT_VERBOSE>
679
680By default, AnyEvent will be completely silent except in fatal
681conditions. You can set this environment variable to make AnyEvent more
682talkative.
683
684When set to C<1> or higher, causes AnyEvent to warn about unexpected
685conditions, such as not being able to load the event model specified by
686C<PERL_ANYEVENT_MODEL>.
687
688When set to C<2> or higher, cause AnyEvent to report to STDERR which event
689model it chooses.
690
691=item C<PERL_ANYEVENT_MODEL>
692
693This can be used to specify the event model to be used by AnyEvent, before
694autodetection and -probing kicks in. It must be a string consisting
695entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
696and the resulting module name is loaded and if the load was successful,
697used as event model. If it fails to load AnyEvent will proceed with
698autodetection and -probing.
699
700This functionality might change in future versions.
701
702For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
703could start your program like this:
704
705 PERL_ANYEVENT_MODEL=Perl perl ...
706
707=back
708
325=head1 EXAMPLE 709=head1 EXAMPLE PROGRAM
326 710
327The following program uses an io watcher to read data from stdin, a timer 711The following program uses an IO watcher to read data from STDIN, a timer
328to display a message once per second, and a condvar to exit the program 712to display a message once per second, and a condition variable to quit the
329when the user enters quit: 713program when the user enters quit:
330 714
331 use AnyEvent; 715 use AnyEvent;
332 716
333 my $cv = AnyEvent->condvar; 717 my $cv = AnyEvent->condvar;
334 718
335 my $io_watcher = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub { 719 my $io_watcher = AnyEvent->io (
720 fh => \*STDIN,
721 poll => 'r',
722 cb => sub {
336 warn "io event <$_[0]>\n"; # will always output <r> 723 warn "io event <$_[0]>\n"; # will always output <r>
337 chomp (my $input = <STDIN>); # read a line 724 chomp (my $input = <STDIN>); # read a line
338 warn "read: $input\n"; # output what has been read 725 warn "read: $input\n"; # output what has been read
339 $cv->broadcast if $input =~ /^q/i; # quit program if /^q/i 726 $cv->broadcast if $input =~ /^q/i; # quit program if /^q/i
727 },
340 }); 728 );
341 729
342 my $time_watcher; # can only be used once 730 my $time_watcher; # can only be used once
343 731
344 sub new_timer { 732 sub new_timer {
345 $timer = AnyEvent->timer (after => 1, cb => sub { 733 $timer = AnyEvent->timer (after => 1, cb => sub {
427 $txn->{finished}->wait; 815 $txn->{finished}->wait;
428 return $txn->{result}; 816 return $txn->{result};
429 817
430The actual code goes further and collects all errors (C<die>s, exceptions) 818The actual code goes further and collects all errors (C<die>s, exceptions)
431that occured during request processing. The C<result> method detects 819that occured during request processing. The C<result> method detects
432wether an exception as thrown (it is stored inside the $txn object) 820whether an exception as thrown (it is stored inside the $txn object)
433and just throws the exception, which means connection errors and other 821and just throws the exception, which means connection errors and other
434problems get reported tot he code that tries to use the result, not in a 822problems get reported tot he code that tries to use the result, not in a
435random callback. 823random callback.
436 824
437All of this enables the following usage styles: 825All of this enables the following usage styles:
438 826
4391. Blocking: 8271. Blocking:
440 828
441 my $data = $fcp->client_get ($url); 829 my $data = $fcp->client_get ($url);
442 830
4432. Blocking, but parallelizing: 8312. Blocking, but running in parallel:
444 832
445 my @datas = map $_->result, 833 my @datas = map $_->result,
446 map $fcp->txn_client_get ($_), 834 map $fcp->txn_client_get ($_),
447 @urls; 835 @urls;
448 836
449Both blocking examples work without the module user having to know 837Both blocking examples work without the module user having to know
450anything about events. 838anything about events.
451 839
4523a. Event-based in a main program, using any support Event module: 8403a. Event-based in a main program, using any supported event module:
453 841
454 use Event; 842 use EV;
455 843
456 $fcp->txn_client_get ($url)->cb (sub { 844 $fcp->txn_client_get ($url)->cb (sub {
457 my $txn = shift; 845 my $txn = shift;
458 my $data = $txn->result; 846 my $data = $txn->result;
459 ... 847 ...
460 }); 848 });
461 849
462 Event::loop; 850 EV::loop;
463 851
4643b. The module user could use AnyEvent, too: 8523b. The module user could use AnyEvent, too:
465 853
466 use AnyEvent; 854 use AnyEvent;
467 855
472 $quit->broadcast; 860 $quit->broadcast;
473 }); 861 });
474 862
475 $quit->wait; 863 $quit->wait;
476 864
865
866=head1 BENCHMARK
867
868To give you an idea of the performance and overheads that AnyEvent adds
869over the event loops directly, here is a benchmark of various supported
870event models natively and with anyevent. The benchmark creates a lot of
871timers (with a zero timeout) and io watchers (watching STDOUT, a pty, to
872become writable, which it is), lets them fire exactly once and destroys
873them again.
874
875=head2 Explanation of the columns
876
877I<watcher> is the number of event watchers created/destroyed. Since
878different event models feature vastly different performances, each event
879loop was given a number of watchers so that overall runtime is acceptable
880and similar between tested event loop (and keep them from crashing): Glib
881would probably take thousands of years if asked to process the same number
882of watchers as EV in this benchmark.
883
884I<bytes> is the number of bytes (as measured by the resident set size,
885RSS) consumed by each watcher. This method of measuring captures both C
886and Perl-based overheads.
887
888I<create> is the time, in microseconds (millionths of seconds), that it
889takes to create a single watcher. The callback is a closure shared between
890all watchers, to avoid adding memory overhead. That means closure creation
891and memory usage is not included in the figures.
892
893I<invoke> is the time, in microseconds, used to invoke a simple
894callback. The callback simply counts down a Perl variable and after it was
895invoked "watcher" times, it would C<< ->broadcast >> a condvar once to
896signal the end of this phase.
897
898I<destroy> is the time, in microseconds, that it takes destroy a single
899watcher.
900
901=head2 Results
902
903 name watcher bytes create invoke destroy comment
904 EV/EV 400000 244 0.56 0.46 0.31 EV native interface
905 EV/Any 100000 610 3.52 0.91 0.75 EV + AnyEvent watchers
906 CoroEV/Any 100000 610 3.49 0.92 0.75 coroutines + Coro::Signal
907 Perl/Any 16000 654 4.64 1.22 0.77 pure perl implementation
908 Event/Event 16000 523 28.05 21.38 0.86 Event native interface
909 Event/Any 16000 943 34.43 20.48 1.39 Event + AnyEvent watchers
910 Glib/Any 16000 1357 96.99 12.55 55.51 quadratic behaviour
911 Tk/Any 2000 1855 27.01 66.61 14.03 SEGV with >> 2000 watchers
912 POE/Event 2000 6644 108.15 768.19 14.33 via POE::Loop::Event
913 POE/Select 2000 6343 94.69 807.65 562.69 via POE::Loop::Select
914
915=head2 Discussion
916
917The benchmark does I<not> measure scalability of the event loop very
918well. For example, a select-based event loop (such as the pure perl one)
919can never compete with an event loop that uses epoll when the number of
920file descriptors grows high. In this benchmark, only a single filehandle
921is used (although some of the AnyEvent adaptors dup() its file descriptor
922to worka round bugs).
923
924C<EV> is the sole leader regarding speed and memory use, which are both
925maximal/minimal, respectively. Even when going through AnyEvent, there is
926only one event loop that uses less memory (the C<Event> module natively), and
927no faster event model, not event C<Event> natively.
928
929The pure perl implementation is hit in a few sweet spots (both the
930zero timeout and the use of a single fd hit optimisations in the perl
931interpreter and the backend itself). Nevertheless tis shows that it
932adds very little overhead in itself. Like any select-based backend its
933performance becomes really bad with lots of file descriptors, of course,
934but this was not subjetc of this benchmark.
935
936The C<Event> module has a relatively high setup and callback invocation cost,
937but overall scores on the third place.
938
939C<Glib>'s memory usage is quite a bit bit higher, features a faster
940callback invocation and overall lands in the same class as C<Event>.
941
942The C<Tk> adaptor works relatively well, the fact that it crashes with
943more than 2000 watchers is a big setback, however, as correctness takes
944precedence over speed. Nevertheless, its performance is surprising, as the
945file descriptor is dup()ed for each watcher. This shows that the dup()
946employed by some adaptors is not a big performance issue (it does incur a
947hidden memory cost inside the kernel, though).
948
949C<POE>, regardless of backend (wether using its pure perl select-based
950backend or the Event backend) shows abysmal performance and memory
951usage: Watchers use almost 30 times as much memory as EV watchers, and 10
952times as much memory as both Event or EV via AnyEvent. Watcher invocation
953is almost 700 times slower as with AnyEvent's pure perl implementation.
954
955Summary: using EV through AnyEvent is faster than any other event
956loop. The overhead AnyEvent adds can be very small, and you should avoid
957POE like the plague if you want performance or reasonable memory usage.
958
959
960=head1 FORK
961
962Most event libraries are not fork-safe. The ones who are usually are
963because they are so inefficient. Only L<EV> is fully fork-aware.
964
965If you have to fork, you must either do so I<before> creating your first
966watcher OR you must not use AnyEvent at all in the child.
967
968
969=head1 SECURITY CONSIDERATIONS
970
971AnyEvent can be forced to load any event model via
972$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to
973execute arbitrary code or directly gain access, it can easily be used to
974make the program hang or malfunction in subtle ways, as AnyEvent watchers
975will not be active when the program uses a different event model than
976specified in the variable.
977
978You can make AnyEvent completely ignore this variable by deleting it
979before the first watcher gets created, e.g. with a C<BEGIN> block:
980
981 BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
982
983 use AnyEvent;
984
985
477=head1 SEE ALSO 986=head1 SEE ALSO
478 987
479Event modules: L<Coro::Event>, L<Coro>, L<Event>, L<Glib::Event>, L<Glib>. 988Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,
989L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,
990L<Event::Lib>, L<Qt>, L<POE>.
480 991
992Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,
481Implementations: L<AnyEvent::Impl::Coro>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>. 993L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,
994L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,
995L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>.
482 996
483Nontrivial usage example: L<Net::FCP>. 997Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.
484 998
485=head1 999
1000=head1 AUTHOR
1001
1002 Marc Lehmann <schmorp@schmorp.de>
1003 http://home.schmorp.de/
486 1004
487=cut 1005=cut
488 1006
4891 10071
490 1008

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