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Revision 1.11 by root, Mon Oct 29 07:56:03 2007 UTC vs.
Revision 1.104 by root, Thu Oct 2 12:26:25 2008 UTC

1=head1 NAME 1=head1 NAME
2 2
3EV - perl interface to libevent, monkey.org/~provos/libevent/ 3EV - perl interface to libev, a high performance full-featured event loop
4 4
5=head1 SYNOPSIS 5=head1 SYNOPSIS
6 6
7 use EV; 7 use EV;
8
9 # TIMERS
10
11 my $w = EV::timer 2, 0, sub {
12 warn "is called after 2s";
13 };
14
15 my $w = EV::timer 2, 2, sub {
16 warn "is called roughly every 2s (repeat = 2)";
17 };
18
19 undef $w; # destroy event watcher again
20
21 my $w = EV::periodic 0, 60, 0, sub {
22 warn "is called every minute, on the minute, exactly";
23 };
24
25 # IO
26
27 my $w = EV::io *STDIN, EV::READ, sub {
28 my ($w, $revents) = @_; # all callbacks receive the watcher and event mask
29 warn "stdin is readable, you entered: ", <STDIN>;
30 };
31
32 # SIGNALS
33
34 my $w = EV::signal 'QUIT', sub {
35 warn "sigquit received\n";
36 };
37
38 # CHILD/PID STATUS CHANGES
8 39
9 # TIMER 40 my $w = EV::child 666, 0, sub {
41 my ($w, $revents) = @_;
42 my $status = $w->rstatus;
43 };
10 44
11 my $w = EV::timer 2, 0, sub { 45 # STAT CHANGES
12 warn "is called after 2s"; 46 my $w = EV::stat "/etc/passwd", 10, sub {
13 };
14
15 my $w = EV::timer 2, 1, sub {
16 warn "is called roughly every 2s (repeat = 1)";
17 };
18
19 undef $w; # destroy event watcher again
20
21 my $w = EV::timer_abs 0, 60, sub {
22 warn "is called every minute, on the minute, exactly";
23 };
24
25 # IO
26
27 my $w = EV::io \*STDIN, EV::READ | EV::PERSIST, sub {
28 my ($w, $events) = @_; # all callbacks get the watcher object and event mask
29 if ($events & EV::TIMEOUT) {
30 warn "nothing received on stdin for 10 seconds, retrying";
31 } else {
32 warn "stdin is readable, you entered: ", <STDIN>;
33 }
34 };
35 $w->timeout (10);
36
37 my $w = EV::timed_io \*STDIN, EV::READ, 30, sub {
38 my ($w, $events) = @_; 47 my ($w, $revents) = @_;
39 if ($_[1] & EV::TIMEOUT) { 48 warn $w->path, " has changed somehow.\n";
40 warn "nothing entered within 30 seconds, bye bye.\n";
41 $w->stop;
42 } else {
43 my $line = <STDIN>;
44 warn "you entered something, you again have 30 seconds.\n";
45 }
46 }; 49 };
47 50
48 # SIGNALS
49
50 my $w = EV::signal 'QUIT', sub {
51 warn "sigquit received\n";
52 };
53
54 my $w = EV::signal 3, sub {
55 warn "sigquit received (this is GNU/Linux, right?)\n";
56 };
57
58 # MAINLOOP 51 # MAINLOOP
59 EV::dispatch; # loop as long as watchers are active 52 EV::loop; # loop until EV::unloop is called or all watchers stop
60 EV::loop; # the same thing
61 EV::loop EV::LOOP_ONCE; # block until some events could be handles 53 EV::loop EV::LOOP_ONESHOT; # block until at least one event could be handled
62 EV::loop EV::LOOP_NONBLOCK; # check and handle some events, but do not wait 54 EV::loop EV::LOOP_NONBLOCK; # try to handle same events, but do not block
63 55
64=head1 DESCRIPTION 56=head1 DESCRIPTION
65 57
66This module provides an interface to libevent 58This module provides an interface to libev
67(L<http://monkey.org/~provos/libevent/>). You probably should acquaint 59(L<http://software.schmorp.de/pkg/libev.html>). While the documentation
68yourself with its documentation and source code to be able to use this 60below is comprehensive, one might also consult the documentation of
69module fully. 61libev itself (L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod> or
62F<perldoc EV::c_doc>) for more subtle details on watcher semantics or some
63discussion on the available backends, or how to force a specific backend
64with C<LIBEV_FLAGS>, or just about in any case because it has much more
65detailed information.
70 66
71Please note thta this module disables the libevent EPOLL method by 67This module is very fast and scalable. It is actually so fast that you
72default, see BUGS, below, if you need to enable it. 68can use it through the L<AnyEvent> module, stay portable to other event
69loops (if you don't rely on any watcher types not available through it)
70and still be faster than with any other event loop currently supported in
71Perl.
73 72
74=cut 73=cut
75 74
76package EV; 75package EV;
77 76
77no warnings;
78use strict; 78use strict;
79 79
80BEGIN { 80BEGIN {
81 our $VERSION = '0.02'; 81 our $VERSION = '3.44';
82 use XSLoader; 82 use XSLoader;
83 XSLoader::load "EV", $VERSION; 83 XSLoader::load "EV", $VERSION;
84} 84}
85 85
86@EV::IO::ISA =
87@EV::Timer::ISA =
88@EV::Periodic::ISA =
89@EV::Signal::ISA =
90@EV::Child::ISA =
91@EV::Stat::ISA =
92@EV::Idle::ISA =
93@EV::Prepare::ISA =
94@EV::Check::ISA =
95@EV::Embed::ISA =
96@EV::Fork::ISA =
97@EV::Async::ISA =
98 "EV::Watcher";
99
100@EV::Loop::Default::ISA = "EV::Loop";
101
102=head1 EVENT LOOPS
103
104EV supports multiple event loops: There is a single "default event loop"
105that can handle everything including signals and child watchers, and any
106number of "dynamic event loops" that can use different backends (with
107various limitations), but no child and signal watchers.
108
109You do not have to do anything to create the default event loop: When
110the module is loaded a suitable backend is selected on the premise of
111selecting a working backend (which for example rules out kqueue on most
112BSDs). Modules should, unless they have "special needs" always use the
113default loop as this is fastest (perl-wise), best supported by other
114modules (e.g. AnyEvent or Coro) and most portable event loop.
115
116For specific programs you can create additional event loops dynamically.
117
118If you want to take avdantage of kqueue (which often works properly for
119sockets only) even though the default loop doesn't enable it, you can
120I<embed> a kqueue loop into the default loop: running the default loop
121will then also service the kqueue loop to some extent. See the example in
122the section about embed watchers for an example on how to achieve that.
123
124=over 4
125
126=item $loop = new EV::loop [$flags]
127
128Create a new event loop as per the specified flags. Please refer to
129the C<ev_loop_new ()> function description in the libev documentation
130(L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod#GLOBAL_FUNCTIONS>,
131or locally-installed as F<EV::c_doc> manpage) for more info.
132
133The loop will automatically be destroyed when it is no longer referenced
134by any watcher and the loop object goes out of scope.
135
136If you are not embedding the loop, then Using C<EV::FLAG_FORKCHECK>
137is recommended, as only the default event loop is protected by this
138module. If you I<are> embedding this loop in the default loop, this is not
139necessary, as C<EV::embed> automatically does the right thing on fork.
140
141=item $loop->loop_fork
142
143Must be called after a fork in the child, before entering or continuing
144the event loop. An alternative is to use C<EV::FLAG_FORKCHECK> which calls
145this function automatically, at some performance loss (refer to the libev
146documentation).
147
148=item $loop->loop_verify
149
150Calls C<ev_verify> to make internal consistency checks (for debugging
151libev) and abort the program if any data structures were found to be
152corrupted.
153
154=item $loop = EV::default_loop [$flags]
155
156Return the default loop (which is a singleton object). Since this module
157already creates the default loop with default flags, specifying flags here
158will not have any effect unless you destroy the default loop first, which
159isn't supported. So in short: don't do it, and if you break it, you get to
160keep the pieces.
161
162=back
163
164
86=head1 BASIC INTERFACE 165=head1 BASIC INTERFACE
87 166
88=over 4 167=over 4
89 168
90=item $EV::NPRI
91
92How many priority levels are available.
93
94=item $EV::DIED 169=item $EV::DIED
95 170
96Must contain a reference to a function that is called when a callback 171Must contain a reference to a function that is called when a callback
97throws an exception (with $@ containing thr error). The default prints an 172throws an exception (with $@ containing the error). The default prints an
98informative message and continues. 173informative message and continues.
99 174
100If this callback throws an exception it will be silently ignored. 175If this callback throws an exception it will be silently ignored.
101 176
177=item $flags = EV::supported_backends
178
179=item $flags = EV::recommended_backends
180
181=item $flags = EV::embeddable_backends
182
183Returns the set (see C<EV::BACKEND_*> flags) of backends supported by this
184instance of EV, the set of recommended backends (supposed to be good) for
185this platform and the set of embeddable backends (see EMBED WATCHERS).
186
187=item EV::sleep $seconds
188
189Block the process for the given number of (fractional) seconds.
190
191=item $time = EV::time
192
193Returns the current time in (fractional) seconds since the epoch.
194
102=item $time = EV::now 195=item $time = EV::now
103 196
104Returns the time in (fractional) seconds since the epoch. 197=item $time = $loop->now
105 198
106=item $version = EV::version 199Returns the time the last event loop iteration has been started. This
200is the time that (relative) timers are based on, and refering to it is
201usually faster then calling EV::time.
107 202
108=item $method = EV::method 203=item $backend = EV::backend
109 204
110Return version string and event polling method used. 205=item $backend = $loop->backend
111 206
112=item EV::loop $flags # EV::LOOP_ONCE, EV::LOOP_ONESHOT 207Returns an integer describing the backend used by libev (EV::METHOD_SELECT
208or EV::METHOD_EPOLL).
113 209
114=item EV::loopexit $after 210=item EV::loop [$flags]
115 211
116Exit any active loop or dispatch after C<$after> seconds or immediately if 212=item $loop->loop ([$flags])
117C<$after> is missing or zero.
118 213
119=item EV::dispatch 214Begin checking for events and calling callbacks. It returns when a
215callback calls EV::unloop.
120 216
121Same as C<EV::loop 0>. 217The $flags argument can be one of the following:
122 218
123=item EV::event $callback 219 0 as above
220 EV::LOOP_ONESHOT block at most once (wait, but do not loop)
221 EV::LOOP_NONBLOCK do not block at all (fetch/handle events but do not wait)
124 222
125Creates a new event watcher waiting for nothing, calling the given callback. 223=item EV::unloop [$how]
126 224
225=item $loop->unloop ([$how])
226
227When called with no arguments or an argument of EV::UNLOOP_ONE, makes the
228innermost call to EV::loop return.
229
230When called with an argument of EV::UNLOOP_ALL, all calls to EV::loop will return as
231fast as possible.
232
233=item $count = EV::loop_count
234
235=item $count = $loop->loop_count
236
237Return the number of times the event loop has polled for new
238events. Sometiems useful as a generation counter.
239
240=item EV::once $fh_or_undef, $events, $timeout, $cb->($revents)
241
242=item $loop->once ($fh_or_undef, $events, $timeout, $cb->($revents))
243
244This function rolls together an I/O and a timer watcher for a single
245one-shot event without the need for managing a watcher object.
246
247If C<$fh_or_undef> is a filehandle or file descriptor, then C<$events>
248must be a bitset containing either C<EV::READ>, C<EV::WRITE> or C<EV::READ
249| EV::WRITE>, indicating the type of I/O event you want to wait for. If
250you do not want to wait for some I/O event, specify C<undef> for
251C<$fh_or_undef> and C<0> for C<$events>).
252
253If timeout is C<undef> or negative, then there will be no
254timeout. Otherwise a EV::timer with this value will be started.
255
256When an error occurs or either the timeout or I/O watcher triggers, then
257the callback will be called with the received event set (in general
258you can expect it to be a combination of C<EV::ERROR>, C<EV::READ>,
259C<EV::WRITE> and C<EV::TIMEOUT>).
260
261EV::once doesn't return anything: the watchers stay active till either
262of them triggers, then they will be stopped and freed, and the callback
263invoked.
264
265=item EV::feed_fd_event ($fd, $revents)
266
267=item $loop->feed_fd_event ($fd, $revents)
268
269Feed an event on a file descriptor into EV. EV will react to this call as
270if the readyness notifications specified by C<$revents> (a combination of
271C<EV::READ> and C<EV::WRITE>) happened on the file descriptor C<$fd>.
272
273=item EV::feed_signal_event ($signal)
274
275Feed a signal event into EV. EV will react to this call as if the signal
276specified by C<$signal> had occured.
277
278=item EV::set_io_collect_interval $time
279
280=item $loop->set_io_collect_interval ($time)
281
282=item EV::set_timeout_collect_interval $time
283
284=item $loop->set_timeout_collect_interval ($time)
285
286These advanced functions set the minimum block interval when polling for I/O events and the minimum
287wait interval for timer events. See the libev documentation at
288L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod#FUNCTIONS_CONTROLLING_THE_EVENT_LOOP>
289(locally installed as F<EV::c_doc>) for a more detailed discussion.
290
291=back
292
293
294=head1 WATCHER OBJECTS
295
296A watcher is an object that gets created to record your interest in some
297event. For instance, if you want to wait for STDIN to become readable, you
298would create an EV::io watcher for that:
299
300 my $watcher = EV::io *STDIN, EV::READ, sub {
301 my ($watcher, $revents) = @_;
302 warn "yeah, STDIN should now be readable without blocking!\n"
303 };
304
305All watchers can be active (waiting for events) or inactive (paused). Only
306active watchers will have their callbacks invoked. All callbacks will be
307called with at least two arguments: the watcher and a bitmask of received
308events.
309
310Each watcher type has its associated bit in revents, so you can use the
311same callback for multiple watchers. The event mask is named after the
312type, i..e. EV::child sets EV::CHILD, EV::prepare sets EV::PREPARE,
313EV::periodic sets EV::PERIODIC and so on, with the exception of I/O events
314(which can set both EV::READ and EV::WRITE bits), and EV::timer (which
315uses EV::TIMEOUT).
316
317In the rare case where one wants to create a watcher but not start it at
318the same time, each constructor has a variant with a trailing C<_ns> in
319its name, e.g. EV::io has a non-starting variant EV::io_ns and so on.
320
321Please note that a watcher will automatically be stopped when the watcher
322object is destroyed, so you I<need> to keep the watcher objects returned by
323the constructors.
324
325Also, all methods changing some aspect of a watcher (->set, ->priority,
326->fh and so on) automatically stop and start it again if it is active,
327which means pending events get lost.
328
329=head2 COMMON WATCHER METHODS
330
331This section lists methods common to all watchers.
332
333=over 4
334
335=item $w->start
336
337Starts a watcher if it isn't active already. Does nothing to an already
338active watcher. By default, all watchers start out in the active state
339(see the description of the C<_ns> variants if you need stopped watchers).
340
341=item $w->stop
342
343Stop a watcher if it is active. Also clear any pending events (events that
344have been received but that didn't yet result in a callback invocation),
345regardless of whether the watcher was active or not.
346
347=item $bool = $w->is_active
348
349Returns true if the watcher is active, false otherwise.
350
351=item $current_data = $w->data
352
353=item $old_data = $w->data ($new_data)
354
355Queries a freely usable data scalar on the watcher and optionally changes
356it. This is a way to associate custom data with a watcher:
357
358 my $w = EV::timer 60, 0, sub {
359 warn $_[0]->data;
360 };
361 $w->data ("print me!");
362
363=item $current_cb = $w->cb
364
365=item $old_cb = $w->cb ($new_cb)
366
367Queries the callback on the watcher and optionally changes it. You can do
368this at any time without the watcher restarting.
369
370=item $current_priority = $w->priority
371
372=item $old_priority = $w->priority ($new_priority)
373
374Queries the priority on the watcher and optionally changes it. Pending
375watchers with higher priority will be invoked first. The valid range of
376priorities lies between EV::MAXPRI (default 2) and EV::MINPRI (default
377-2). If the priority is outside this range it will automatically be
378normalised to the nearest valid priority.
379
380The default priority of any newly-created watcher is 0.
381
382Note that the priority semantics have not yet been fleshed out and are
383subject to almost certain change.
384
385=item $w->invoke ($revents)
386
387Call the callback *now* with the given event mask.
388
389=item $w->feed_event ($revents)
390
391Feed some events on this watcher into EV. EV will react to this call as if
392the watcher had received the given C<$revents> mask.
393
394=item $revents = $w->clear_pending
395
396If the watcher is pending, this function clears its pending status and
397returns its C<$revents> bitset (as if its callback was invoked). If the
398watcher isn't pending it does nothing and returns C<0>.
399
400=item $previous_state = $w->keepalive ($bool)
401
402Normally, C<EV::loop> will return when there are no active watchers
403(which is a "deadlock" because no progress can be made anymore). This is
404convinient because it allows you to start your watchers (and your jobs),
405call C<EV::loop> once and when it returns you know that all your jobs are
406finished (or they forgot to register some watchers for their task :).
407
408Sometimes, however, this gets in your way, for example when the module
409that calls C<EV::loop> (usually the main program) is not the same module
410as a long-living watcher (for example a DNS client module written by
411somebody else even). Then you might want any outstanding requests to be
412handled, but you would not want to keep C<EV::loop> from returning just
413because you happen to have this long-running UDP port watcher.
414
415In this case you can clear the keepalive status, which means that even
416though your watcher is active, it won't keep C<EV::loop> from returning.
417
418The initial value for keepalive is true (enabled), and you cna change it
419any time.
420
421Example: Register an I/O watcher for some UDP socket but do not keep the
422event loop from running just because of that watcher.
423
424 my $udp_socket = ...
425 my $udp_watcher = EV::io $udp_socket, EV::READ, sub { ... };
426 $udp_watcher->keepalive (0);
427
428=item $loop = $w->loop
429
430Return the loop that this watcher is attached to.
431
432=back
433
434
435=head1 WATCHER TYPES
436
437Each of the following subsections describes a single watcher type.
438
439=head3 I/O WATCHERS - is this file descriptor readable or writable?
440
441=over 4
442
127=item my $w = EV::io $fileno_or_fh, $eventmask, $callback 443=item $w = EV::io $fileno_or_fh, $eventmask, $callback
128 444
129=item my $w = EV::io_ns $fileno_or_fh, $eventmask, $callback 445=item $w = EV::io_ns $fileno_or_fh, $eventmask, $callback
446
447=item $w = $loop->io ($fileno_or_fh, $eventmask, $callback)
448
449=item $w = $loop->io_ns ($fileno_or_fh, $eventmask, $callback)
130 450
131As long as the returned watcher object is alive, call the C<$callback> 451As long as the returned watcher object is alive, call the C<$callback>
132when the events specified in C<$eventmask> happen. Initially, the timeout 452when at least one of events specified in C<$eventmask> occurs.
133is disabled.
134 453
135You can additionall set a timeout to occur on the watcher, but note that
136this timeout will not be reset when you get an I/O event in the EV::PERSIST
137case, and reaching a timeout will always stop the watcher even in the
138EV::PERSIST case.
139
140If you want a timeout to occur only after a specific time of inactivity, set
141a repeating timeout and do NOT use EV::PERSIST.
142
143Eventmask can be one or more of these constants ORed together: 454The $eventmask can be one or more of these constants ORed together:
144 455
145 EV::READ wait until read() wouldn't block anymore 456 EV::READ wait until read() wouldn't block anymore
146 EV::WRITE wait until write() wouldn't block anymore 457 EV::WRITE wait until write() wouldn't block anymore
147 EV::PERSIST stay active after a (non-timeout) event occured
148 458
149The C<io_ns> variant doesn't add/start the newly created watcher. 459The C<io_ns> variant doesn't start (activate) the newly created watcher.
150 460
151=item my $w = EV::timed_io $fileno_or_fh, $eventmask, $timeout, $callback 461=item $w->set ($fileno_or_fh, $eventmask)
152 462
153=item my $w = EV::timed_io_ns $fileno_or_fh, $eventmask, $timeout, $callback 463Reconfigures the watcher, see the constructor above for details. Can be
464called at any time.
154 465
155Same as C<io> and C<io_ns>, but also specifies a timeout (as if there was 466=item $current_fh = $w->fh
156a call to C<< $w->timeout ($timout, 1) >>. The persist flag is not allowed
157and will automatically be cleared. The watcher will be restarted after each event.
158 467
159If the timeout is zero or undef, no timeout will be set, and a normal 468=item $old_fh = $w->fh ($new_fh)
160watcher (with the persist flag set!) will be created.
161 469
162This has the effect of timing out after the specified period of inactivity 470Returns the previously set filehandle and optionally set a new one.
163has happened.
164 471
165Due to the design of libevent, this is also relatively inefficient, having 472=item $current_eventmask = $w->events
166one or two io watchers and a separate timeout watcher that you reset on
167activity (by calling its C<start> method) is usually more efficient.
168 473
474=item $old_eventmask = $w->events ($new_eventmask)
475
476Returns the previously set event mask and optionally set a new one.
477
478=back
479
480
481=head3 TIMER WATCHERS - relative and optionally repeating timeouts
482
483=over 4
484
169=item my $w = EV::timer $after, $repeat, $callback 485=item $w = EV::timer $after, $repeat, $callback
170 486
171=item my $w = EV::timer_ns $after, $repeat, $callback 487=item $w = EV::timer_ns $after, $repeat, $callback
172 488
173Calls the callback after C<$after> seconds. If C<$repeat> is true, the 489=item $w = $loop->timer ($after, $repeat, $callback)
174timer will be restarted after the callback returns. This means that the
175callback would be called roughly every C<$after> seconds, prolonged by the
176time the callback takes.
177 490
491=item $w = $loop->timer_ns ($after, $repeat, $callback)
492
493Calls the callback after C<$after> seconds (which may be fractional). If
494C<$repeat> is non-zero, the timer will be restarted (with the $repeat
495value as $after) after the callback returns.
496
497This means that the callback would be called roughly after C<$after>
498seconds, and then every C<$repeat> seconds. The timer does his best not
499to drift, but it will not invoke the timer more often then once per event
500loop iteration, and might drift in other cases. If that isn't acceptable,
501look at EV::periodic, which can provide long-term stable timers.
502
503The timer is based on a monotonic clock, that is, if somebody is sitting
504in front of the machine while the timer is running and changes the system
505clock, the timer will nevertheless run (roughly) the same time.
506
178The C<timer_ns> variant doesn't add/start the newly created watcher. 507The C<timer_ns> variant doesn't start (activate) the newly created watcher.
179 508
180=item my $w = EV::timer_abs $at, $interval, $callback 509=item $w->set ($after, $repeat)
181 510
182=item my $w = EV::timer_abs_ns $at, $interval, $callback 511Reconfigures the watcher, see the constructor above for details. Can be called at
512any time.
183 513
184Similar to EV::timer, but the time is given as an absolute point in time 514=item $w->again
185(C<$at>), plus an optional C<$interval>.
186 515
187If the C<$interval> is zero, then the callback will be called at the time 516Similar to the C<start> method, but has special semantics for repeating timers:
188C<$at> if that is in the future, or as soon as possible if its in the
189past. It will not automatically repeat.
190 517
191If the C<$interval> is nonzero, then the watcher will always be scheduled 518If the timer is active and non-repeating, it will be stopped.
192to time out at the next C<$at + integer * $interval> time.
193 519
194This can be used to schedule a callback to run at very regular intervals, 520If the timer is active and repeating, reset the timeout to occur
195as long as the processing time is less then the interval (otherwise 521C<$repeat> seconds after now.
196obviously events will be skipped). 522
523If the timer is inactive and repeating, start it using the repeat value.
524
525Otherwise do nothing.
526
527This behaviour is useful when you have a timeout for some IO
528operation. You create a timer object with the same value for C<$after> and
529C<$repeat>, and then, in the read/write watcher, run the C<again> method
530on the timeout.
531
532=back
533
534
535=head3 PERIODIC WATCHERS - to cron or not to cron?
536
537=over 4
538
539=item $w = EV::periodic $at, $interval, $reschedule_cb, $callback
540
541=item $w = EV::periodic_ns $at, $interval, $reschedule_cb, $callback
542
543=item $w = $loop->periodic ($at, $interval, $reschedule_cb, $callback)
544
545=item $w = $loop->periodic_ns ($at, $interval, $reschedule_cb, $callback)
546
547Similar to EV::timer, but is not based on relative timeouts but on
548absolute times. Apart from creating "simple" timers that trigger "at" the
549specified time, it can also be used for non-drifting absolute timers and
550more complex, cron-like, setups that are not adversely affected by time
551jumps (i.e. when the system clock is changed by explicit date -s or other
552means such as ntpd). It is also the most complex watcher type in EV.
553
554It has three distinct "modes":
555
556=over 4
557
558=item * absolute timer ($interval = $reschedule_cb = 0)
559
560This time simply fires at the wallclock time C<$at> and doesn't repeat. It
561will not adjust when a time jump occurs, that is, if it is to be run
562at January 1st 2011 then it will run when the system time reaches or
563surpasses this time.
564
565=item * repeating interval timer ($interval > 0, $reschedule_cb = 0)
566
567In this mode the watcher will always be scheduled to time out at the
568next C<$at + N * $interval> time (for some integer N) and then repeat,
569regardless of any time jumps.
570
571This can be used to create timers that do not drift with respect to system
572time:
573
574 my $hourly = EV::periodic 0, 3600, 0, sub { print "once/hour\n" };
575
576That doesn't mean there will always be 3600 seconds in between triggers,
577but only that the the clalback will be called when the system time shows a
578full hour (UTC).
197 579
198Another way to think about it (for the mathematically inclined) is that 580Another way to think about it (for the mathematically inclined) is that
199C<timer_abs> will try to tun the callback at the next possible time where 581EV::periodic will try to run the callback in this mode at the next
200C<$time = $at (mod $interval)>, regardless of any time jumps. 582possible time where C<$time = $at (mod $interval)>, regardless of any time
583jumps.
201 584
585=item * manual reschedule mode ($reschedule_cb = coderef)
586
587In this mode $interval and $at are both being ignored. Instead, each
588time the periodic watcher gets scheduled, the reschedule callback
589($reschedule_cb) will be called with the watcher as first, and the current
590time as second argument.
591
592I<This callback MUST NOT stop or destroy this or any other periodic
593watcher, ever, and MUST NOT call any event loop functions or methods>. If
594you need to stop it, return 1e30 and stop it afterwards. You may create
595and start a C<EV::prepare> watcher for this task.
596
597It must return the next time to trigger, based on the passed time value
598(that is, the lowest time value larger than or equal to to the second
599argument). It will usually be called just before the callback will be
600triggered, but might be called at other times, too.
601
602This can be used to create very complex timers, such as a timer that
603triggers on each midnight, local time (actually 24 hours after the last
604midnight, to keep the example simple. If you know a way to do it correctly
605in about the same space (without requiring elaborate modules), drop me a
606note :):
607
608 my $daily = EV::periodic 0, 0, sub {
609 my ($w, $now) = @_;
610
611 use Time::Local ();
612 my (undef, undef, undef, $d, $m, $y) = localtime $now;
613 86400 + Time::Local::timelocal 0, 0, 0, $d, $m, $y
614 }, sub {
615 print "it's midnight or likely shortly after, now\n";
616 };
617
618=back
619
202The C<timer_abs_ns> variant doesn't add/start the newly created watcher. 620The C<periodic_ns> variant doesn't start (activate) the newly created watcher.
203 621
622=item $w->set ($at, $interval, $reschedule_cb)
623
624Reconfigures the watcher, see the constructor above for details. Can be called at
625any time.
626
627=item $w->again
628
629Simply stops and starts the watcher again.
630
631=item $time = $w->at
632
633Return the time that the watcher is expected to trigger next.
634
635=back
636
637
638=head3 SIGNAL WATCHERS - signal me when a signal gets signalled!
639
640=over 4
641
204=item my $w = EV::signal $signal, $callback 642=item $w = EV::signal $signal, $callback
205 643
206=item my $w = EV::signal_ns $signal, $callback 644=item $w = EV::signal_ns $signal, $callback
207 645
208Call the callback when $signal is received (the signal can be specified 646Call the callback when $signal is received (the signal can be specified by
209by number or by name, just as with kill or %SIG). Signal watchers are 647number or by name, just as with C<kill> or C<%SIG>).
210persistent no natter what.
211 648
212EV will grab the signal for the process (the kernel only allows one 649EV will grab the signal for the process (the kernel only allows one
213component to receive signals) when you start a signal watcher, and 650component to receive a signal at a time) when you start a signal watcher,
214removes it again when you stop it. Pelr does the same when you add/remove 651and removes it again when you stop it. Perl does the same when you
215callbacks to %SIG, so watch out. 652add/remove callbacks to C<%SIG>, so watch out.
216 653
217Unfortunately, only one handler can be registered per signal. Screw 654You can have as many signal watchers per signal as you want.
218libevent.
219 655
220The C<signal_ns> variant doesn't add/start the newly created watcher. 656The C<signal_ns> variant doesn't start (activate) the newly created watcher.
221 657
222=back 658=item $w->set ($signal)
223 659
224=head1 THE EV::Event CLASS 660Reconfigures the watcher, see the constructor above for details. Can be
661called at any time.
225 662
226All EV functions creating an event watcher (designated by C<my $w =>
227above) support the following methods on the returned watcher object:
228
229=over 4
230
231=item $w->add ($timeout)
232
233Stops and (re-)starts the event watcher, setting the optional timeout to
234the given value, or clearing the timeout if none is given.
235
236=item $w->start
237
238Stops and (re-)starts the event watcher without touching the timeout.
239
240=item $w->del
241
242=item $w->stop
243
244Stop the event watcher if it was started.
245
246=item $current_callback = $w->cb
247
248=item $old_callback = $w->cb ($new_callback)
249
250Return the previously set callback and optionally set a new one.
251
252=item $current_fh = $w->fh
253
254=item $old_fh = $w->fh ($new_fh)
255
256Returns the previously set filehandle and optionally set a new one (also
257clears the EV::SIGNAL flag when setting a filehandle).
258
259=item $current_signal = $w->signal 663=item $current_signum = $w->signal
260 664
261=item $old_signal = $w->signal ($new_signal) 665=item $old_signum = $w->signal ($new_signal)
262 666
667Returns the previously set signal (always as a number not name) and
668optionally set a new one.
669
670=back
671
672
673=head3 CHILD WATCHERS - watch out for process status changes
674
675=over 4
676
677=item $w = EV::child $pid, $trace, $callback
678
679=item $w = EV::child_ns $pid, $trace, $callback
680
681=item $w = $loop->child ($pid, $trace, $callback)
682
683=item $w = $loop->child_ns ($pid, $trace, $callback)
684
685Call the callback when a status change for pid C<$pid> (or any pid
686if C<$pid> is 0) has been received (a status change happens when the
687process terminates or is killed, or, when trace is true, additionally when
688it is stopped or continued). More precisely: when the process receives
689a C<SIGCHLD>, EV will fetch the outstanding exit/wait status for all
690changed/zombie children and call the callback.
691
692It is valid (and fully supported) to install a child watcher after a child
693has exited but before the event loop has started its next iteration (for
694example, first you C<fork>, then the new child process might exit, and
695only then do you install a child watcher in the parent for the new pid).
696
697You can access both exit (or tracing) status and pid by using the
698C<rstatus> and C<rpid> methods on the watcher object.
699
700You can have as many pid watchers per pid as you want, they will all be
701called.
702
703The C<child_ns> variant doesn't start (activate) the newly created watcher.
704
705=item $w->set ($pid, $trace)
706
707Reconfigures the watcher, see the constructor above for details. Can be called at
708any time.
709
710=item $current_pid = $w->pid
711
263Returns the previously set signal number and optionally set a new one (also sets 712Returns the previously set process id and optionally set a new one.
264the EV::SIGNAL flag when setting a signal).
265 713
266=item $current_eventmask = $w->events 714=item $exit_status = $w->rstatus
267 715
268=item $old_eventmask = $w->events ($new_eventmask) 716Return the exit/wait status (as returned by waitpid, see the waitpid entry
717in perlfunc).
269 718
719=item $pid = $w->rpid
720
721Return the pid of the awaited child (useful when you have installed a
722watcher for all pids).
723
724=back
725
726
727=head3 STAT WATCHERS - did the file attributes just change?
728
729=over 4
730
731=item $w = EV::stat $path, $interval, $callback
732
733=item $w = EV::stat_ns $path, $interval, $callback
734
735=item $w = $loop->stat ($path, $interval, $callback)
736
737=item $w = $loop->stat_ns ($path, $interval, $callback)
738
739Call the callback when a file status change has been detected on
740C<$path>. The C<$path> does not need to exist, changing from "path exists"
741to "path does not exist" is a status change like any other.
742
743The C<$interval> is a recommended polling interval for systems where
744OS-supported change notifications don't exist or are not supported. If
745you use C<0> then an unspecified default is used (which is highly
746recommended!), which is to be expected to be around five seconds usually.
747
748This watcher type is not meant for massive numbers of stat watchers,
749as even with OS-supported change notifications, this can be
750resource-intensive.
751
752The C<stat_ns> variant doesn't start (activate) the newly created watcher.
753
754=item ... = $w->stat
755
756This call is very similar to the perl C<stat> built-in: It stats (using
757C<lstat>) the path specified in the watcher and sets perls stat cache (as
758well as EV's idea of the current stat values) to the values found.
759
760In scalar context, a boolean is return indicating success or failure of
761the stat. In list context, the same 13-value list as with stat is returned
762(except that the blksize and blocks fields are not reliable).
763
764In the case of an error, errno is set to C<ENOENT> (regardless of the
765actual error value) and the C<nlink> value is forced to zero (if the stat
766was successful then nlink is guaranteed to be non-zero).
767
768See also the next two entries for more info.
769
770=item ... = $w->attr
771
772Just like C<< $w->stat >>, but without the initial stat'ing: this returns
773the values most recently detected by EV. See the next entry for more info.
774
775=item ... = $w->prev
776
777Just like C<< $w->stat >>, but without the initial stat'ing: this returns
778the previous set of values, before the change.
779
780That is, when the watcher callback is invoked, C<< $w->prev >> will be set
781to the values found I<before> a change was detected, while C<< $w->attr >>
782returns the values found leading to the change detection. The difference (if any)
783between C<prev> and C<attr> is what triggered the callback.
784
785If you did something to the filesystem object and do not want to trigger
786yet another change, you can call C<stat> to update EV's idea of what the
787current attributes are.
788
789=item $w->set ($path, $interval)
790
791Reconfigures the watcher, see the constructor above for details. Can be
792called at any time.
793
794=item $current_path = $w->path
795
796=item $old_path = $w->path ($new_path)
797
270Returns the previously set event mask and optionally set a new one. 798Returns the previously set path and optionally set a new one.
271 799
272=item $w->timeout ($after, $repeat) 800=item $current_interval = $w->interval
273 801
274Resets the timeout (see C<EV::timer> for details). 802=item $old_interval = $w->interval ($new_interval)
275 803
276=item $w->timeout_abs ($at, $interval) 804Returns the previously set interval and optionally set a new one. Can be
805used to query the actual interval used.
277 806
278Resets the timeout (see C<EV::timer_abs> for details).
279
280=item $w->priority_set ($priority)
281
282Set the priority of the watcher to C<$priority> (0 <= $priority < $EV::NPRI).
283
284=back 807=back
285 808
286=head1 BUGS
287 809
288Lots. Libevent itself isn't well tested and rather buggy, and this module 810=head3 IDLE WATCHERS - when you've got nothing better to do...
289is quite new at the moment.
290 811
291Please note that the epoll method is not, in general, reliable in programs 812=over 4
292that use fork (even if no libveent calls are being made in the forked
293process). If your program behaves erratically, try setting the environment
294variable C<EVENT_NOEPOLL> first when running the program.
295 813
296In general, if you fork, then you can only use the EV module in one of the 814=item $w = EV::idle $callback
297children. 815
816=item $w = EV::idle_ns $callback
817
818=item $w = $loop->idle ($callback)
819
820=item $w = $loop->idle_ns ($callback)
821
822Call the callback when there are no other pending watchers of the same or
823higher priority (excluding check, prepare and other idle watchers of the
824same or lower priority, of course). They are called idle watchers because
825when the watcher is the highest priority pending event in the process, the
826process is considered to be idle at that priority.
827
828If you want a watcher that is only ever called when I<no> other events are
829outstanding you have to set the priority to C<EV::MINPRI>.
830
831The process will not block as long as any idle watchers are active, and
832they will be called repeatedly until stopped.
833
834For example, if you have idle watchers at priority C<0> and C<1>, and
835an I/O watcher at priority C<0>, then the idle watcher at priority C<1>
836and the I/O watcher will always run when ready. Only when the idle watcher
837at priority C<1> is stopped and the I/O watcher at priority C<0> is not
838pending with the C<0>-priority idle watcher be invoked.
839
840The C<idle_ns> variant doesn't start (activate) the newly created watcher.
841
842=back
843
844
845=head3 PREPARE WATCHERS - customise your event loop!
846
847=over 4
848
849=item $w = EV::prepare $callback
850
851=item $w = EV::prepare_ns $callback
852
853=item $w = $loop->prepare ($callback)
854
855=item $w = $loop->prepare_ns ($callback)
856
857Call the callback just before the process would block. You can still
858create/modify any watchers at this point.
859
860See the EV::check watcher, below, for explanations and an example.
861
862The C<prepare_ns> variant doesn't start (activate) the newly created watcher.
863
864=back
865
866
867=head3 CHECK WATCHERS - customise your event loop even more!
868
869=over 4
870
871=item $w = EV::check $callback
872
873=item $w = EV::check_ns $callback
874
875=item $w = $loop->check ($callback)
876
877=item $w = $loop->check_ns ($callback)
878
879Call the callback just after the process wakes up again (after it has
880gathered events), but before any other callbacks have been invoked.
881
882This is used to integrate other event-based software into the EV
883mainloop: You register a prepare callback and in there, you create io and
884timer watchers as required by the other software. Here is a real-world
885example of integrating Net::SNMP (with some details left out):
886
887 our @snmp_watcher;
888
889 our $snmp_prepare = EV::prepare sub {
890 # do nothing unless active
891 $dispatcher->{_event_queue_h}
892 or return;
893
894 # make the dispatcher handle any outstanding stuff
895 ... not shown
896
897 # create an I/O watcher for each and every socket
898 @snmp_watcher = (
899 (map { EV::io $_, EV::READ, sub { } }
900 keys %{ $dispatcher->{_descriptors} }),
901
902 EV::timer +($event->[Net::SNMP::Dispatcher::_ACTIVE]
903 ? $event->[Net::SNMP::Dispatcher::_TIME] - EV::now : 0),
904 0, sub { },
905 );
906 };
907
908The callbacks are irrelevant (and are not even being called), the
909only purpose of those watchers is to wake up the process as soon as
910one of those events occurs (socket readable, or timer timed out). The
911corresponding EV::check watcher will then clean up:
912
913 our $snmp_check = EV::check sub {
914 # destroy all watchers
915 @snmp_watcher = ();
916
917 # make the dispatcher handle any new stuff
918 ... not shown
919 };
920
921The callbacks of the created watchers will not be called as the watchers
922are destroyed before this cna happen (remember EV::check gets called
923first).
924
925The C<check_ns> variant doesn't start (activate) the newly created watcher.
926
927=back
928
929
930=head3 FORK WATCHERS - the audacity to resume the event loop after a fork
931
932Fork watchers are called when a C<fork ()> was detected. The invocation
933is done before the event loop blocks next and before C<check> watchers
934are being called, and only in the child after the fork.
935
936=over 4
937
938=item $w = EV::fork $callback
939
940=item $w = EV::fork_ns $callback
941
942=item $w = $loop->fork ($callback)
943
944=item $w = $loop->fork_ns ($callback)
945
946Call the callback before the event loop is resumed in the child process
947after a fork.
948
949The C<fork_ns> variant doesn't start (activate) the newly created watcher.
950
951=back
952
953
954=head3 EMBED WATCHERS - when one backend isn't enough...
955
956This is a rather advanced watcher type that lets you embed one event loop
957into another (currently only IO events are supported in the embedded
958loop, other types of watchers might be handled in a delayed or incorrect
959fashion and must not be used).
960
961See the libev documentation at
962L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod#code_ev_embed_code_when_one_backend_>
963(locally installed as F<EV::c_doc>) for more details.
964
965In short, this watcher is most useful on BSD systems without working
966kqueue to still be able to handle a large number of sockets:
967
968 my $socket_loop;
969
970 # check wether we use SELECT or POLL _and_ KQUEUE is supported
971 if (
972 (EV::backend & (EV::BACKEND_POLL | EV::BACKEND_SELECT))
973 && (EV::supported_backends & EV::embeddable_backends & EV::BACKEND_KQUEUE)
974 ) {
975 # use kqueue for sockets
976 $socket_loop = new EV::Loop EV::BACKEND_KQUEUE | EV::FLAG_NOENV;
977 }
978
979 # use the default loop otherwise
980 $socket_loop ||= EV::default_loop;
981
982=over 4
983
984=item $w = EV::embed $otherloop[, $callback]
985
986=item $w = EV::embed_ns $otherloop[, $callback]
987
988=item $w = $loop->embed ($otherloop[, $callback])
989
990=item $w = $loop->embed_ns ($otherloop[, $callback])
991
992Call the callback when the embedded event loop (C<$otherloop>) has any
993I/O activity. The C<$callback> is optional: if it is missing, then the
994embedded event loop will be managed automatically (which is recommended),
995otherwise you have to invoke C<sweep> yourself.
996
997The C<embed_ns> variant doesn't start (activate) the newly created watcher.
998
999=back
1000
1001=head3 ASYNC WATCHERS - how to wake up another event loop
1002
1003Async watchers are provided by EV, but have little use in perl directly, as perl
1004neither supports threads nor direct access to signal handlers or other
1005contexts where they could be of value.
1006
1007It is, however, possible to use them from the XS level.
1008
1009Please see the libev documentation for further details.
1010
1011=over 4
1012
1013=item $w = EV::async $callback
1014
1015=item $w = EV::async_ns $callback
1016
1017=item $w->send
1018
1019=item $bool = $w->async_pending
1020
1021=back
1022
1023
1024=head1 PERL SIGNALS
1025
1026While Perl signal handling (C<%SIG>) is not affected by EV, the behaviour
1027with EV is as the same as any other C library: Perl-signals will only be
1028handled when Perl runs, which means your signal handler might be invoked
1029only the next time an event callback is invoked.
1030
1031The solution is to use EV signal watchers (see C<EV::signal>), which will
1032ensure proper operations with regards to other event watchers.
1033
1034If you cannot do this for whatever reason, you can also force a watcher
1035to be called on every event loop iteration by installing a C<EV::check>
1036watcher:
1037
1038 my $async_check = EV::check sub { };
1039
1040This ensures that perl gets into control for a short time to handle any
1041pending signals, and also ensures (slightly) slower overall operation.
1042
1043=head1 THREADS
1044
1045Threads are not supported by this module in any way. Perl pseudo-threads
1046is evil stuff and must die. As soon as Perl gains real threads I will work
1047on thread support for it.
1048
1049=head1 FORK
1050
1051Most of the "improved" event delivering mechanisms of modern operating
1052systems have quite a few problems with fork(2) (to put it bluntly: it is
1053not supported and usually destructive). Libev makes it possible to work
1054around this by having a function that recreates the kernel state after
1055fork in the child.
1056
1057On non-win32 platforms, this module requires the pthread_atfork
1058functionality to do this automatically for you. This function is quite
1059buggy on most BSDs, though, so YMMV. The overhead for this is quite
1060negligible, because everything the function currently does is set a flag
1061that is checked only when the event loop gets used the next time, so when
1062you do fork but not use EV, the overhead is minimal.
1063
1064On win32, there is no notion of fork so all this doesn't apply, of course.
298 1065
299=cut 1066=cut
300 1067
301our $DIED = sub { 1068our $DIED = sub {
302 warn "EV: error in callback (ignoring): $@"; 1069 warn "EV: error in callback (ignoring): $@";
303}; 1070};
304 1071
305our $NPRI = 4; 1072default_loop
306our $BASE = init; 1073 or die 'EV: cannot initialise libev backend. bad $ENV{LIBEV_FLAGS}?';
307priority_init $NPRI;
308
309push @AnyEvent::REGISTRY, [EV => "EV::AnyEvent"];
310 1074
3111; 10751;
312 1076
313=head1 SEE ALSO 1077=head1 SEE ALSO
314 1078
315 L<EV::DNS>, L<event(3)>, L<event.h>, L<evdns.h>. 1079L<EV::ADNS> (asynchronous DNS), L<Glib::EV> (makes Glib/Gtk2 use EV as
316 L<EV::AnyEvent>. 1080event loop), L<EV::Glib> (embed Glib into EV), L<Coro::EV> (efficient
1081coroutines with EV), L<Net::SNMP::EV> (asynchronous SNMP), L<AnyEvent> for
1082event-loop agnostic and portable event driven programming.
317 1083
318=head1 AUTHOR 1084=head1 AUTHOR
319 1085
320 Marc Lehmann <schmorp@schmorp.de> 1086 Marc Lehmann <schmorp@schmorp.de>
321 http://home.schmorp.de/ 1087 http://home.schmorp.de/
322 1088
323=cut 1089=cut
324 1090

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