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Revision 1.29 by root, Wed Oct 31 14:17:43 2007 UTC vs.
Revision 1.59 by root, Thu Apr 24 08:38:13 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 - 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
35loaded: L<Coro::Event>, L<Event>, L<Glib>, L<Tk>. The first one found is 84the following modules is already loaded: L<Coro::EV>, L<Coro::Event>,
85L<EV>, L<Event>, L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>. The first one
36used. If none is found, the module tries to load these modules in the 86found is used. If none are found, the module tries to load these modules
37order given. The first one that could be successfully loaded will be 87(excluding Event::Lib and Qt) in the order given. The first one that can
38used. If still none could be found, AnyEvent will fall back to a pure-perl 88be successfully loaded will be used. If, after this, still none could be
39event loop, which is also not very efficient. 89found, AnyEvent will fall back to a pure-perl event loop, which is not
90very efficient, but should work everywhere.
40 91
41Because AnyEvent first checks for modules that are already loaded, loading 92Because AnyEvent first checks for modules that are already loaded, loading
42an Event model explicitly before first using AnyEvent will likely make 93an event model explicitly before first using AnyEvent will likely make
43that model the default. For example: 94that model the default. For example:
44 95
45 use Tk; 96 use Tk;
46 use AnyEvent; 97 use AnyEvent;
47 98
48 # .. AnyEvent will likely default to Tk 99 # .. AnyEvent will likely default to Tk
100
101The I<likely> means that, if any module loads another event model and
102starts using it, all bets are off. Maybe you should tell their authors to
103use AnyEvent so their modules work together with others seamlessly...
49 104
50The pure-perl implementation of AnyEvent is called 105The pure-perl implementation of AnyEvent is called
51C<AnyEvent::Impl::Perl>. Like other event modules you can load it 106C<AnyEvent::Impl::Perl>. Like other event modules you can load it
52explicitly. 107explicitly.
53 108
… …
56AnyEvent has the central concept of a I<watcher>, which is an object that 111AnyEvent 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 112stores relevant data for each kind of event you are waiting for, such as
58the callback to call, the filehandle to watch, etc. 113the callback to call, the filehandle to watch, etc.
59 114
60These watchers are normal Perl objects with normal Perl lifetime. After 115These watchers are normal Perl objects with normal Perl lifetime. After
61creating a watcher it will immediately "watch" for events and invoke 116creating a watcher it will immediately "watch" for events and invoke the
117callback when the event occurs (of course, only when the event model
118is in control).
119
62the callback. To disable the watcher you have to destroy it (e.g. by 120To 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 121variable you store it in to C<undef> or otherwise deleting all references
64references to it). 122to it).
65 123
66All watchers are created by calling a method on the C<AnyEvent> class. 124All watchers are created by calling a method on the C<AnyEvent> class.
67 125
126Many watchers either are used with "recursion" (repeating timers for
127example), or need to refer to their watcher object in other ways.
128
129An any way to achieve that is this pattern:
130
131 my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
132 # you can use $w here, for example to undef it
133 undef $w;
134 });
135
136Note that C<my $w; $w => combination. This is necessary because in Perl,
137my variables are only visible after the statement in which they are
138declared.
139
68=head2 IO WATCHERS 140=head2 IO WATCHERS
69 141
70You can create I/O watcher by calling the C<< AnyEvent->io >> method with 142You can create an I/O watcher by calling the C<< AnyEvent->io >> method
71the following mandatory arguments: 143with the following mandatory key-value pairs as arguments:
72 144
73C<fh> the Perl I<filehandle> (not filedescriptor) to watch for 145C<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 146events. 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 147creates a watcher waiting for "r"eadable or "w"ritable events,
76to invoke everytime the filehandle becomes ready. 148respectively. C<cb> is the callback to invoke each time the file handle
149becomes ready.
77 150
78Only one io watcher per C<fh> and C<poll> combination is allowed (i.e. on 151As 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 152copy of it alive/open.
80Tk - if you are sure you are not using Tk this limitation is gone).
81 153
82Filehandles will be kept alive, so as long as the watcher exists, the 154It is not allowed to close a file handle as long as any watcher is active
83filehandle exists, too. 155on the underlying file descriptor.
156
157Some event loops issue spurious readyness notifications, so you should
158always use non-blocking calls when reading/writing from/to your file
159handles.
84 160
85Example: 161Example:
86 162
87 # wait for readability of STDIN, then read a line and disable the watcher 163 # 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 { 164 my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
… …
94=head2 TIME WATCHERS 170=head2 TIME WATCHERS
95 171
96You can create a time watcher by calling the C<< AnyEvent->timer >> 172You can create a time watcher by calling the C<< AnyEvent->timer >>
97method with the following mandatory arguments: 173method with the following mandatory arguments:
98 174
99C<after> after how many seconds (fractions are supported) should the timer 175C<after> specifies after how many seconds (fractional values are
100activate. C<cb> the callback to invoke. 176supported) should the timer activate. C<cb> the callback to invoke in that
177case.
101 178
102The timer callback will be invoked at most once: if you want a repeating 179The 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 180timer you have to create a new watcher (this is a limitation by both Tk
104and Glib). 181and Glib).
105 182
… …
109 my $w = AnyEvent->timer (after => 7.7, cb => sub { 186 my $w = AnyEvent->timer (after => 7.7, cb => sub {
110 warn "timeout\n"; 187 warn "timeout\n";
111 }); 188 });
112 189
113 # to cancel the timer: 190 # to cancel the timer:
114 undef $w 191 undef $w;
115 192
193Example 2:
194
195 # fire an event after 0.5 seconds, then roughly every second
196 my $w;
197
198 my $cb = sub {
199 # cancel the old timer while creating a new one
200 $w = AnyEvent->timer (after => 1, cb => $cb);
201 };
202
203 # start the "loop" by creating the first watcher
204 $w = AnyEvent->timer (after => 0.5, cb => $cb);
205
206=head3 TIMING ISSUES
207
208There are two ways to handle timers: based on real time (relative, "fire
209in 10 seconds") and based on wallclock time (absolute, "fire at 12
210o'clock").
211
212While most event loops expect timers to specified in a relative way, they
213use absolute time internally. This makes a difference when your clock
214"jumps", for example, when ntp decides to set your clock backwards from
215the wrong date of 2014-01-01 to 2008-01-01, a watcher that is supposed to
216fire "after" a second might actually take six years to finally fire.
217
218AnyEvent cannot compensate for this. The only event loop that is conscious
219about these issues is L<EV>, which offers both relative (ev_timer, based
220on true relative time) and absolute (ev_periodic, based on wallclock time)
221timers.
222
223AnyEvent always prefers relative timers, if available, matching the
224AnyEvent API.
225
226=head2 SIGNAL WATCHERS
227
228You can watch for signals using a signal watcher, C<signal> is the signal
229I<name> without any C<SIG> prefix, C<cb> is the Perl callback to
230be invoked whenever a signal occurs.
231
232Multiple signal occurances can be clumped together into one callback
233invocation, and callback invocation will be synchronous. synchronous means
234that it might take a while until the signal gets handled by the process,
235but it is guarenteed not to interrupt any other callbacks.
236
237The main advantage of using these watchers is that you can share a signal
238between multiple watchers.
239
240This watcher might use C<%SIG>, so programs overwriting those signals
241directly will likely not work correctly.
242
243Example: exit on SIGINT
244
245 my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
246
247=head2 CHILD PROCESS WATCHERS
248
249You can also watch on a child process exit and catch its exit status.
250
251The child process is specified by the C<pid> argument (if set to C<0>, it
252watches for any child process exit). The watcher will trigger as often
253as status change for the child are received. This works by installing a
254signal handler for C<SIGCHLD>. The callback will be called with the pid
255and exit status (as returned by waitpid).
256
257Example: wait for pid 1333
258
259 my $w = AnyEvent->child (
260 pid => 1333,
261 cb => sub {
262 my ($pid, $status) = @_;
263 warn "pid $pid exited with status $status";
264 },
265 );
266
116=head2 CONDITION WATCHERS 267=head2 CONDITION VARIABLES
117 268
118Condition watchers can be created by calling the C<< AnyEvent->condvar >> 269Condition variables can be created by calling the C<< AnyEvent->condvar >>
119method without any arguments. 270method without any arguments.
120 271
121A condition watcher watches for a condition - precisely that the C<< 272A condition variable waits for a condition - precisely that the C<<
122->broadcast >> method has been called. 273->broadcast >> method has been called.
123 274
124The watcher has only two methods: 275They are very useful to signal that a condition has been fulfilled, for
276example, if you write a module that does asynchronous http requests,
277then a condition variable would be the ideal candidate to signal the
278availability of results.
279
280You can also use condition variables to block your main program until
281an event occurs - for example, you could C<< ->wait >> in your main
282program until the user clicks the Quit button in your app, which would C<<
283->broadcast >> the "quit" event.
284
285Note that condition variables recurse into the event loop - if you have
286two pirces of code that call C<< ->wait >> in a round-robbin fashion, you
287lose. Therefore, condition variables are good to export to your caller, but
288you should avoid making a blocking wait yourself, at least in callbacks,
289as this asks for trouble.
290
291This object has two methods:
125 292
126=over 4 293=over 4
127 294
128=item $cv->wait 295=item $cv->wait
129 296
130Wait (blocking if necessary) until the C<< ->broadcast >> method has been 297Wait (blocking if necessary) until the C<< ->broadcast >> method has been
131called on c<$cv>, while servicing other watchers normally. 298called on c<$cv>, while servicing other watchers normally.
132 299
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 300You can only wait once on a condition - additional calls will return
141immediately. 301immediately.
142 302
303Not all event models support a blocking wait - some die in that case
304(programs might want to do that to stay interactive), so I<if you are
305using this from a module, never require a blocking wait>, but let the
306caller decide whether the call will block or not (for example, by coupling
307condition variables with some kind of request results and supporting
308callbacks so the caller knows that getting the result will not block,
309while still suppporting blocking waits if the caller so desires).
310
311Another reason I<never> to C<< ->wait >> in a module is that you cannot
312sensibly have two C<< ->wait >>'s in parallel, as that would require
313multiple interpreters or coroutines/threads, none of which C<AnyEvent>
314can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and
315L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
316from different coroutines, however).
317
143=item $cv->broadcast 318=item $cv->broadcast
144 319
145Flag the condition as ready - a running C<< ->wait >> and all further 320Flag 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 321calls to C<wait> will (eventually) return after this method has been
147is waiting the broadcast will be remembered.. 322called. If nobody is waiting the broadcast will be remembered..
323
324=back
148 325
149Example: 326Example:
150 327
151 # wait till the result is ready 328 # wait till the result is ready
152 my $result_ready = AnyEvent->condvar; 329 my $result_ready = AnyEvent->condvar;
153 330
154 # do something such as adding a timer 331 # do something such as adding a timer
155 # or socket watcher the calls $result_ready->broadcast 332 # or socket watcher the calls $result_ready->broadcast
156 # when the "result" is ready. 333 # when the "result" is ready.
334 # in this case, we simply use a timer:
335 my $w = AnyEvent->timer (
336 after => 1,
337 cb => sub { $result_ready->broadcast },
338 );
157 339
340 # this "blocks" (while handling events) till the watcher
341 # calls broadcast
158 $result_ready->wait; 342 $result_ready->wait;
159 343
160=back 344=head1 GLOBAL VARIABLES AND FUNCTIONS
161
162=head2 SIGNAL WATCHERS
163
164You can listen for signals using a signal watcher, C<signal> is the signal
165I<name> without any C<SIG> prefix. Multiple signals events can be clumped
166together into one callback invocation, and callback invocation might or
167might not be asynchronous.
168
169These watchers might use C<%SIG>, so programs overwriting those signals
170directly will likely not work correctly.
171
172Example: exit on SIGINT
173
174 my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
175
176=head2 CHILD PROCESS WATCHERS
177
178You can also listen for the status of a child process specified by the
179C<pid> argument. The watcher will only trigger once. This works by
180installing a signal handler for C<SIGCHLD>.
181
182Example: wait for pid 1333
183
184 my $w = AnyEvent->child (pid => 1333, cb => sub { warn "exit status $?" });
185
186=head1 GLOBALS
187 345
188=over 4 346=over 4
189 347
190=item $AnyEvent::MODEL 348=item $AnyEvent::MODEL
191 349
… …
195C<AnyEvent::Impl:xxx> modules, but can be any other class in the case 353C<AnyEvent::Impl:xxx> modules, but can be any other class in the case
196AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>). 354AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).
197 355
198The known classes so far are: 356The known classes so far are:
199 357
200 EV::AnyEvent based on EV (an interface to libev, best choice) 358 AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
201 AnyEvent::Impl::Coro based on Coro::Event, second best choice. 359 AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
360 AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
202 AnyEvent::Impl::Event based on Event, also second best choice :) 361 AnyEvent::Impl::Event based on Event, second best choice.
203 AnyEvent::Impl::Glib based on Glib, second-best choice. 362 AnyEvent::Impl::Glib based on Glib, third-best choice.
204 AnyEvent::Impl::Tk based on Tk, very bad choice. 363 AnyEvent::Impl::Tk based on Tk, very bad choice.
205 AnyEvent::Impl::Perl pure-perl implementation, inefficient. 364 AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
365 AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
366 AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
206 367
207=item AnyEvent::detect 368=item AnyEvent::detect
208 369
209Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model if 370Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
210necessary. You should only call this function right before you would have 371if necessary. You should only call this function right before you would
211created an AnyEvent watcher anyway, that is, very late at runtime. 372have created an AnyEvent watcher anyway, that is, as late as possible at
373runtime.
212 374
213=back 375=back
214 376
215=head1 WHAT TO DO IN A MODULE 377=head1 WHAT TO DO IN A MODULE
216 378
217As a module author, you should "use AnyEvent" and call AnyEvent methods 379As a module author, you should C<use AnyEvent> and call AnyEvent methods
218freely, but you should not load a specific event module or rely on it. 380freely, but you should not load a specific event module or rely on it.
219 381
220Be careful when you create watchers in the module body - Anyevent will 382Be careful when you create watchers in the module body - AnyEvent will
221decide which event module to use as soon as the first method is called, so 383decide which event module to use as soon as the first method is called, so
222by calling AnyEvent in your module body you force the user of your module 384by calling AnyEvent in your module body you force the user of your module
223to load the event module first. 385to load the event module first.
224 386
387Never call C<< ->wait >> on a condition variable unless you I<know> that
388the C<< ->broadcast >> method has been called on it already. This is
389because it will stall the whole program, and the whole point of using
390events is to stay interactive.
391
392It is fine, however, to call C<< ->wait >> when the user of your module
393requests it (i.e. if you create a http request object ad have a method
394called C<results> that returns the results, it should call C<< ->wait >>
395freely, as the user of your module knows what she is doing. always).
396
225=head1 WHAT TO DO IN THE MAIN PROGRAM 397=head1 WHAT TO DO IN THE MAIN PROGRAM
226 398
227There will always be a single main program - the only place that should 399There will always be a single main program - the only place that should
228dictate which event model to use. 400dictate which event model to use.
229 401
230If it doesn't care, it can just "use AnyEvent" and use it itself, or not 402If it doesn't care, it can just "use AnyEvent" and use it itself, or not
231do anything special and let AnyEvent decide which implementation to chose. 403do anything special (it does not need to be event-based) and let AnyEvent
404decide which implementation to chose if some module relies on it.
232 405
233If the main program relies on a specific event model (for example, in Gtk2 406If the main program relies on a specific event model. For example, in
234programs you have to rely on either Glib or Glib::Event), you should load 407Gtk2 programs you have to rely on the Glib module. You should load the
235it before loading AnyEvent or any module that uses it, generally, as early 408event module before loading AnyEvent or any module that uses it: generally
236as possible. The reason is that modules might create watchers when they 409speaking, you should load it as early as possible. The reason is that
237are loaded, and AnyEvent will decide on the event model to use as soon as 410modules might create watchers when they are loaded, and AnyEvent will
238it creates watchers, and it might chose the wrong one unless you load the 411decide on the event model to use as soon as it creates watchers, and it
239correct one yourself. 412might chose the wrong one unless you load the correct one yourself.
240 413
241You can chose to use a rather inefficient pure-perl implementation by 414You can chose to use a rather inefficient pure-perl implementation by
242loading the C<AnyEvent::Impl::Perl> module, but letting AnyEvent chose is 415loading the C<AnyEvent::Impl::Perl> module, which gives you similar
243generally better. 416behaviour everywhere, but letting AnyEvent chose is generally better.
244 417
245=cut 418=cut
246 419
247package AnyEvent; 420package AnyEvent;
248 421
249no warnings; 422no warnings;
250use strict; 423use strict;
251 424
252use Carp; 425use Carp;
253 426
254our $VERSION = '2.55'; 427our $VERSION = '3.2';
255our $MODEL; 428our $MODEL;
256 429
257our $AUTOLOAD; 430our $AUTOLOAD;
258our @ISA; 431our @ISA;
259 432
260our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1; 433our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
261 434
262our @REGISTRY; 435our @REGISTRY;
263 436
264my @models = ( 437my @models = (
438 [Coro::EV:: => AnyEvent::Impl::CoroEV::],
265 [Coro::Event:: => AnyEvent::Impl::Coro::], 439 [Coro::Event:: => AnyEvent::Impl::CoroEvent::],
266 [EV:: => EV::AnyEvent::], 440 [EV:: => AnyEvent::Impl::EV::],
267 [Event:: => AnyEvent::Impl::Event::], 441 [Event:: => AnyEvent::Impl::Event::],
268 [Glib:: => AnyEvent::Impl::Glib::], 442 [Glib:: => AnyEvent::Impl::Glib::],
269 [Tk:: => AnyEvent::Impl::Tk::], 443 [Tk:: => AnyEvent::Impl::Tk::],
270 [AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::], 444 [AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
271); 445);
446my @models_detect = (
447 [Qt:: => AnyEvent::Impl::Qt::], # requires special main program
448 [Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
449);
272 450
273our %method = map +($_ => 1), qw(io timer condvar broadcast wait signal one_event DESTROY); 451our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY);
274 452
275sub detect() { 453sub detect() {
276 unless ($MODEL) { 454 unless ($MODEL) {
277 no strict 'refs'; 455 no strict 'refs';
278 456
457 if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
458 my $model = "AnyEvent::Impl::$1";
459 if (eval "require $model") {
460 $MODEL = $model;
461 warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;
462 }
463 }
464
279 # check for already loaded models 465 # check for already loaded models
466 unless ($MODEL) {
280 for (@REGISTRY, @models) { 467 for (@REGISTRY, @models, @models_detect) {
281 my ($package, $model) = @$_; 468 my ($package, $model) = @$_;
282 if (${"$package\::VERSION"} > 0) { 469 if (${"$package\::VERSION"} > 0) {
283 if (eval "require $model") { 470 if (eval "require $model") {
284 $MODEL = $model; 471 $MODEL = $model;
285 warn "AnyEvent: found model '$model', using it.\n" if $verbose > 1; 472 warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;
286 last; 473 last;
474 }
287 } 475 }
288 } 476 }
289 }
290 477
291 unless ($MODEL) { 478 unless ($MODEL) {
292 # try to load a model 479 # try to load a model
293 480
294 for (@REGISTRY, @models) { 481 for (@REGISTRY, @models) {
295 my ($package, $model) = @$_; 482 my ($package, $model) = @$_;
296 if (eval "require $package" 483 if (eval "require $package"
297 and ${"$package\::VERSION"} > 0 484 and ${"$package\::VERSION"} > 0
298 and eval "require $model") { 485 and eval "require $model") {
299 $MODEL = $model; 486 $MODEL = $model;
300 warn "AnyEvent: autoprobed and loaded model '$model', using it.\n" if $verbose > 1; 487 warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;
301 last; 488 last;
489 }
302 } 490 }
491
492 $MODEL
493 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.";
303 } 494 }
304
305 $MODEL
306 or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: Event (or Coro+Event), Glib or Tk.";
307 } 495 }
308 496
309 unshift @ISA, $MODEL; 497 unshift @ISA, $MODEL;
310 push @{"$MODEL\::ISA"}, "AnyEvent::Base"; 498 push @{"$MODEL\::ISA"}, "AnyEvent::Base";
311 } 499 }
… …
369 557
370# default implementation for ->child 558# default implementation for ->child
371 559
372our %PID_CB; 560our %PID_CB;
373our $CHLD_W; 561our $CHLD_W;
562our $CHLD_DELAY_W;
374our $PID_IDLE; 563our $PID_IDLE;
375our $WNOHANG; 564our $WNOHANG;
376 565
377sub _child_wait { 566sub _child_wait {
378 while (0 < (my $pid = waitpid -1, $WNOHANG)) { 567 while (0 < (my $pid = waitpid -1, $WNOHANG)) {
379 $_->() for values %{ (delete $PID_CB{$pid}) || {} }; 568 $_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),
569 (values %{ $PID_CB{0} || {} });
380 } 570 }
381 571
382 undef $PID_IDLE; 572 undef $PID_IDLE;
573}
574
575sub _sigchld {
576 # make sure we deliver these changes "synchronous" with the event loop.
577 $CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub {
578 undef $CHLD_DELAY_W;
579 &_child_wait;
580 });
383} 581}
384 582
385sub child { 583sub child {
386 my (undef, %arg) = @_; 584 my (undef, %arg) = @_;
387 585
388 my $pid = uc $arg{pid} 586 defined (my $pid = $arg{pid} + 0)
389 or Carp::croak "required option 'pid' is missing"; 587 or Carp::croak "required option 'pid' is missing";
390 588
391 $PID_CB{$pid}{$arg{cb}} = $arg{cb}; 589 $PID_CB{$pid}{$arg{cb}} = $arg{cb};
392 590
393 unless ($WNOHANG) { 591 unless ($WNOHANG) {
394 $WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1; 592 $WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;
395 } 593 }
396 594
397 unless ($CHLD_W) { 595 unless ($CHLD_W) {
398 $CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_child_wait); 596 $CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
399 # child could be a zombie already 597 # child could be a zombie already, so make at least one round
400 $PID_IDLE ||= AnyEvent->timer (after => 0, cb => \&_child_wait); 598 &_sigchld;
401 } 599 }
402 600
403 bless [$pid, $arg{cb}], "AnyEvent::Base::Child" 601 bless [$pid, $arg{cb}], "AnyEvent::Base::Child"
404} 602}
405 603
… …
411 609
412 undef $CHLD_W unless keys %PID_CB; 610 undef $CHLD_W unless keys %PID_CB;
413} 611}
414 612
415=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE 613=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
614
615This is an advanced topic that you do not normally need to use AnyEvent in
616a module. This section is only of use to event loop authors who want to
617provide AnyEvent compatibility.
416 618
417If you need to support another event library which isn't directly 619If you need to support another event library which isn't directly
418supported by AnyEvent, you can supply your own interface to it by 620supported by AnyEvent, you can supply your own interface to it by
419pushing, before the first watcher gets created, the package name of 621pushing, before the first watcher gets created, the package name of
420the event module and the package name of the interface to use onto 622the event module and the package name of the interface to use onto
421C<@AnyEvent::REGISTRY>. You can do that before and even without loading 623C<@AnyEvent::REGISTRY>. You can do that before and even without loading
422AnyEvent. 624AnyEvent, so it is reasonably cheap.
423 625
424Example: 626Example:
425 627
426 push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::]; 628 push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];
427 629
428This tells AnyEvent to (literally) use the C<urxvt::anyevent::> 630This tells AnyEvent to (literally) use the C<urxvt::anyevent::>
429package/class when it finds the C<urxvt> package/module is loaded. When 631package/class when it finds the C<urxvt> package/module is already loaded.
632
430AnyEvent is loaded and asked to find a suitable event model, it will 633When AnyEvent is loaded and asked to find a suitable event model, it
431first check for the presence of urxvt. 634will first check for the presence of urxvt by trying to C<use> the
635C<urxvt::anyevent> module.
432 636
433The class should provide implementations for all watcher types (see 637The class should provide implementations for all watcher types. See
434L<AnyEvent::Impl::Event> (source code), L<AnyEvent::Impl::Glib> 638L<AnyEvent::Impl::EV> (source code), L<AnyEvent::Impl::Glib> (Source code)
435(Source code) and so on for actual examples, use C<perldoc -m 639and so on for actual examples. Use C<perldoc -m AnyEvent::Impl::Glib> to
436AnyEvent::Impl::Glib> to see the sources). 640see the sources.
437 641
642If you don't provide C<signal> and C<child> watchers than AnyEvent will
643provide suitable (hopefully) replacements.
644
438The above isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt) 645The above example isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt)
439uses the above line as-is. An interface isn't included in AnyEvent 646terminal emulator uses the above line as-is. An interface isn't included
440because it doesn't make sense outside the embedded interpreter inside 647in AnyEvent because it doesn't make sense outside the embedded interpreter
441I<rxvt-unicode>, and it is updated and maintained as part of the 648inside I<rxvt-unicode>, and it is updated and maintained as part of the
442I<rxvt-unicode> distribution. 649I<rxvt-unicode> distribution.
443 650
444I<rxvt-unicode> also cheats a bit by not providing blocking access to 651I<rxvt-unicode> also cheats a bit by not providing blocking access to
445condition variables: code blocking while waiting for a condition will 652condition variables: code blocking while waiting for a condition will
446C<die>. This still works with most modules/usages, and blocking calls must 653C<die>. This still works with most modules/usages, and blocking calls must
447not be in an interactive application, so it makes sense. 654not be done in an interactive application, so it makes sense.
448 655
449=head1 ENVIRONMENT VARIABLES 656=head1 ENVIRONMENT VARIABLES
450 657
451The following environment variables are used by this module: 658The following environment variables are used by this module:
452 659
453C<PERL_ANYEVENT_VERBOSE> when set to C<2> or higher, reports which event 660=over 4
454model gets used.
455 661
662=item C<PERL_ANYEVENT_VERBOSE>
663
664When set to C<2> or higher, cause AnyEvent to report to STDERR which event
665model it chooses.
666
667=item C<PERL_ANYEVENT_MODEL>
668
669This can be used to specify the event model to be used by AnyEvent, before
670autodetection and -probing kicks in. It must be a string consisting
671entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
672and the resulting module name is loaded and if the load was successful,
673used as event model. If it fails to load AnyEvent will proceed with
674autodetection and -probing.
675
676This functionality might change in future versions.
677
678For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
679could start your program like this:
680
681 PERL_ANYEVENT_MODEL=Perl perl ...
682
683=back
684
456=head1 EXAMPLE 685=head1 EXAMPLE PROGRAM
457 686
458The following program uses an io watcher to read data from stdin, a timer 687The following program uses an IO watcher to read data from STDIN, a timer
459to display a message once per second, and a condvar to exit the program 688to display a message once per second, and a condition variable to quit the
460when the user enters quit: 689program when the user enters quit:
461 690
462 use AnyEvent; 691 use AnyEvent;
463 692
464 my $cv = AnyEvent->condvar; 693 my $cv = AnyEvent->condvar;
465 694
466 my $io_watcher = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub { 695 my $io_watcher = AnyEvent->io (
696 fh => \*STDIN,
697 poll => 'r',
698 cb => sub {
467 warn "io event <$_[0]>\n"; # will always output <r> 699 warn "io event <$_[0]>\n"; # will always output <r>
468 chomp (my $input = <STDIN>); # read a line 700 chomp (my $input = <STDIN>); # read a line
469 warn "read: $input\n"; # output what has been read 701 warn "read: $input\n"; # output what has been read
470 $cv->broadcast if $input =~ /^q/i; # quit program if /^q/i 702 $cv->broadcast if $input =~ /^q/i; # quit program if /^q/i
703 },
471 }); 704 );
472 705
473 my $time_watcher; # can only be used once 706 my $time_watcher; # can only be used once
474 707
475 sub new_timer { 708 sub new_timer {
476 $timer = AnyEvent->timer (after => 1, cb => sub { 709 $timer = AnyEvent->timer (after => 1, cb => sub {
… …
558 $txn->{finished}->wait; 791 $txn->{finished}->wait;
559 return $txn->{result}; 792 return $txn->{result};
560 793
561The actual code goes further and collects all errors (C<die>s, exceptions) 794The actual code goes further and collects all errors (C<die>s, exceptions)
562that occured during request processing. The C<result> method detects 795that occured during request processing. The C<result> method detects
563wether an exception as thrown (it is stored inside the $txn object) 796whether an exception as thrown (it is stored inside the $txn object)
564and just throws the exception, which means connection errors and other 797and just throws the exception, which means connection errors and other
565problems get reported tot he code that tries to use the result, not in a 798problems get reported tot he code that tries to use the result, not in a
566random callback. 799random callback.
567 800
568All of this enables the following usage styles: 801All of this enables the following usage styles:
569 802
5701. Blocking: 8031. Blocking:
571 804
572 my $data = $fcp->client_get ($url); 805 my $data = $fcp->client_get ($url);
573 806
5742. Blocking, but parallelizing: 8072. Blocking, but running in parallel:
575 808
576 my @datas = map $_->result, 809 my @datas = map $_->result,
577 map $fcp->txn_client_get ($_), 810 map $fcp->txn_client_get ($_),
578 @urls; 811 @urls;
579 812
580Both blocking examples work without the module user having to know 813Both blocking examples work without the module user having to know
581anything about events. 814anything about events.
582 815
5833a. Event-based in a main program, using any support Event module: 8163a. Event-based in a main program, using any supported event module:
584 817
585 use Event; 818 use EV;
586 819
587 $fcp->txn_client_get ($url)->cb (sub { 820 $fcp->txn_client_get ($url)->cb (sub {
588 my $txn = shift; 821 my $txn = shift;
589 my $data = $txn->result; 822 my $data = $txn->result;
590 ... 823 ...
591 }); 824 });
592 825
593 Event::loop; 826 EV::loop;
594 827
5953b. The module user could use AnyEvent, too: 8283b. The module user could use AnyEvent, too:
596 829
597 use AnyEvent; 830 use AnyEvent;
598 831
… …
603 $quit->broadcast; 836 $quit->broadcast;
604 }); 837 });
605 838
606 $quit->wait; 839 $quit->wait;
607 840
841=head1 FORK
842
843Most event libraries are not fork-safe. The ones who are usually are
844because they are so inefficient. Only L<EV> is fully fork-aware.
845
846If you have to fork, you must either do so I<before> creating your first
847watcher OR you must not use AnyEvent at all in the child.
848
849=head1 SECURITY CONSIDERATIONS
850
851AnyEvent can be forced to load any event model via
852$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to
853execute arbitrary code or directly gain access, it can easily be used to
854make the program hang or malfunction in subtle ways, as AnyEvent watchers
855will not be active when the program uses a different event model than
856specified in the variable.
857
858You can make AnyEvent completely ignore this variable by deleting it
859before the first watcher gets created, e.g. with a C<BEGIN> block:
860
861 BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
862
863 use AnyEvent;
864
608=head1 SEE ALSO 865=head1 SEE ALSO
609 866
610Event modules: L<Coro::Event>, L<Coro>, L<Event>, L<Glib::Event>, L<Glib>. 867Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,
868L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,
869L<Event::Lib>, L<Qt>.
611 870
871Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,
612Implementations: L<AnyEvent::Impl::Coro>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>. 872L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,
873L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,
874L<AnyEvent::Impl::Qt>.
613 875
614Nontrivial usage example: L<Net::FCP>. 876Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.
615 877
616=head1 878=head1 AUTHOR
879
880 Marc Lehmann <schmorp@schmorp.de>
881 http://home.schmorp.de/
617 882
618=cut 883=cut
619 884
6201 8851
621 886

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