ViewVC Help
View File | Revision Log | Show Annotations | Download File
/cvs/EV/README
(Generate patch)

Comparing EV/README (file contents):
Revision 1.4 by root, Mon Oct 29 19:53:21 2007 UTC vs.
Revision 1.40 by root, Thu Jan 19 17:55:23 2012 UTC

1NAME 1NAME
2 EV - perl interface to libevent, monkey.org/~provos/libevent/ 2 EV - perl interface to libev, a high performance full-featured event
3 loop
3 4
4SYNOPSIS 5SYNOPSIS
5 use EV; 6 use EV;
7
8 # TIMERS
9
10 my $w = EV::timer 2, 0, sub {
11 warn "is called after 2s";
12 };
13
14 my $w = EV::timer 2, 2, sub {
15 warn "is called roughly every 2s (repeat = 2)";
16 };
17
18 undef $w; # destroy event watcher again
19
20 my $w = EV::periodic 0, 60, 0, sub {
21 warn "is called every minute, on the minute, exactly";
22 };
23
24 # IO
25
26 my $w = EV::io *STDIN, EV::READ, sub {
27 my ($w, $revents) = @_; # all callbacks receive the watcher and event mask
28 warn "stdin is readable, you entered: ", <STDIN>;
29 };
30
31 # SIGNALS
32
33 my $w = EV::signal 'QUIT', sub {
34 warn "sigquit received\n";
35 };
36
37 # CHILD/PID STATUS CHANGES
6 38
7 # TIMER 39 my $w = EV::child 666, 0, sub {
40 my ($w, $revents) = @_;
41 my $status = $w->rstatus;
42 };
8 43
9 my $w = EV::timer 2, 0, sub { 44 # STAT CHANGES
10 warn "is called after 2s"; 45 my $w = EV::stat "/etc/passwd", 10, sub {
11 };
12
13 my $w = EV::timer 2, 1, sub {
14 warn "is called roughly every 2s (repeat = 1)";
15 };
16
17 undef $w; # destroy event watcher again
18
19 my $w = EV::timer_abs 0, 60, sub {
20 warn "is called every minute, on the minute, exactly";
21 };
22
23 # IO
24
25 my $w = EV::io \*STDIN, EV::READ | EV::PERSIST, sub {
26 my ($w, $events) = @_; # all callbacks get the watcher object and event mask
27 if ($events & EV::TIMEOUT) {
28 warn "nothing received on stdin for 10 seconds, retrying";
29 } else {
30 warn "stdin is readable, you entered: ", <STDIN>;
31 }
32 };
33 $w->timeout (10);
34
35 my $w = EV::timed_io \*STDIN, EV::READ, 30, sub {
36 my ($w, $events) = @_; 46 my ($w, $revents) = @_;
37 if ($_[1] & EV::TIMEOUT) { 47 warn $w->path, " has changed somehow.\n";
38 warn "nothing entered within 30 seconds, bye bye.\n";
39 $w->stop;
40 } else {
41 my $line = <STDIN>;
42 warn "you entered something, you again have 30 seconds.\n";
43 }
44 }; 48 };
45 49
46 # SIGNALS
47
48 my $w = EV::signal 'QUIT', sub {
49 warn "sigquit received\n";
50 };
51
52 my $w = EV::signal 3, sub {
53 warn "sigquit received (this is GNU/Linux, right?)\n";
54 };
55
56 # MAINLOOP 50 # MAINLOOP
57 EV::dispatch; # loop as long as watchers are active 51 EV::run; # loop until EV::unloop is called or all watchers stop
58 EV::loop; # the same thing
59 EV::loop EV::LOOP_ONCE; # block until some events could be handles 52 EV::run EV::RUN_ONCE; # block until at least one event could be handled
60 EV::loop EV::LOOP_NONBLOCK; # check and handle some events, but do not wait 53 EV::run EV::RUN_NOWAIT; # try to handle same events, but do not block
54
55BEFORE YOU START USING THIS MODULE
56 If you only need timer, I/O, signal, child and idle watchers and not the
57 advanced functionality of this module, consider using AnyEvent instead,
58 specifically the simplified API described in AE.
59
60 When used with EV as backend, the AE API is as fast as the native EV
61 API, but your programs/modules will still run with many other event
62 loops.
61 63
62DESCRIPTION 64DESCRIPTION
63 This module provides an interface to libevent 65 This module provides an interface to libev
64 (<http://monkey.org/~provos/libevent/>). You probably should acquaint 66 (<http://software.schmorp.de/pkg/libev.html>). While the documentation
65 yourself with its documentation and source code to be able to use this 67 below is comprehensive, one might also consult the documentation of
66 module fully. 68 libev itself (<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod> or
69 perldoc EV::libev) for more subtle details on watcher semantics or some
70 discussion on the available backends, or how to force a specific backend
71 with "LIBEV_FLAGS", or just about in any case because it has much more
72 detailed information.
67 73
68 Please note thta this module disables the libevent EPOLL method by 74 This module is very fast and scalable. It is actually so fast that you
69 default, see BUGS, below, if you need to enable it. 75 can use it through the AnyEvent module, stay portable to other event
76 loops (if you don't rely on any watcher types not available through it)
77 and still be faster than with any other event loop currently supported
78 in Perl.
79
80 PORTING FROM EV 3.X to 4.X
81 EV version 4 introduces a number of incompatible changes summarised
82 here. According to the depreciation strategy used by libev, there is a
83 compatibility layer in place so programs should continue to run
84 unchanged (the XS interface lacks this layer, so programs using that one
85 need to be updated).
86
87 This compatibility layer will be switched off in some future release.
88
89 All changes relevant to Perl are renames of symbols, functions and
90 methods:
91
92 EV::loop => EV::run
93 EV::LOOP_NONBLOCK => EV::RUN_NOWAIT
94 EV::LOOP_ONESHOT => EV::RUN_ONCE
95
96 EV::unloop => EV::break
97 EV::UNLOOP_CANCEL => EV::BREAK_CANCEL
98 EV::UNLOOP_ONE => EV::BREAK_ONE
99 EV::UNLOOP_ALL => EV::BREAK_ALL
100
101 EV::TIMEOUT => EV::TIMER
102
103 EV::loop_count => EV::iteration
104 EV::loop_depth => EV::depth
105 EV::loop_verify => EV::verify
106
107 The loop object methods corresponding to the functions above have been
108 similarly renamed.
109
110 MODULE EXPORTS
111 This module does not export any symbols.
112
113EVENT LOOPS
114 EV supports multiple event loops: There is a single "default event loop"
115 that can handle everything including signals and child watchers, and any
116 number of "dynamic event loops" that can use different backends (with
117 various limitations), but no child and signal watchers.
118
119 You do not have to do anything to create the default event loop: When
120 the module is loaded a suitable backend is selected on the premise of
121 selecting a working backend (which for example rules out kqueue on most
122 BSDs). Modules should, unless they have "special needs" always use the
123 default loop as this is fastest (perl-wise), best supported by other
124 modules (e.g. AnyEvent or Coro) and most portable event loop.
125
126 For specific programs you can create additional event loops dynamically.
127
128 If you want to take advantage of kqueue (which often works properly for
129 sockets only) even though the default loop doesn't enable it, you can
130 *embed* a kqueue loop into the default loop: running the default loop
131 will then also service the kqueue loop to some extent. See the example
132 in the section about embed watchers for an example on how to achieve
133 that.
134
135 $loop = new EV::Loop [$flags]
136 Create a new event loop as per the specified flags. Please refer to
137 the "ev_loop_new ()" function description in the libev documentation
138 (<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod#GLOBAL_FUNCTI
139 ONS>, or locally-installed as EV::libev manpage) for more info.
140
141 The loop will automatically be destroyed when it is no longer
142 referenced by any watcher and the loop object goes out of scope.
143
144 If you are not embedding the loop, then Using "EV::FLAG_FORKCHECK"
145 is recommended, as only the default event loop is protected by this
146 module. If you *are* embedding this loop in the default loop, this
147 is not necessary, as "EV::embed" automatically does the right thing
148 on fork.
149
150 $loop->loop_fork
151 Must be called after a fork in the child, before entering or
152 continuing the event loop. An alternative is to use
153 "EV::FLAG_FORKCHECK" which calls this function automatically, at
154 some performance loss (refer to the libev documentation).
155
156 $loop->verify
157 Calls "ev_verify" to make internal consistency checks (for debugging
158 libev) and abort the program if any data structures were found to be
159 corrupted.
160
161 $loop = EV::default_loop [$flags]
162 Return the default loop (which is a singleton object). Since this
163 module already creates the default loop with default flags,
164 specifying flags here will not have any effect unless you destroy
165 the default loop first, which isn't supported. So in short: don't do
166 it, and if you break it, you get to keep the pieces.
70 167
71BASIC INTERFACE 168BASIC INTERFACE
72 $EV::NPRI
73 How many priority levels are available.
74
75 $EV::DIED 169 $EV::DIED
76 Must contain a reference to a function that is called when a 170 Must contain a reference to a function that is called when a
77 callback throws an exception (with $@ containing thr error). The 171 callback throws an exception (with $@ containing the error). The
78 default prints an informative message and continues. 172 default prints an informative message and continues.
79 173
80 If this callback throws an exception it will be silently ignored. 174 If this callback throws an exception it will be silently ignored.
81 175
176 $flags = EV::supported_backends
177 $flags = EV::recommended_backends
178 $flags = EV::embeddable_backends
179 Returns the set (see "EV::BACKEND_*" flags) of backends supported by
180 this instance of EV, the set of recommended backends (supposed to be
181 good) for this platform and the set of embeddable backends (see
182 EMBED WATCHERS).
183
184 EV::sleep $seconds
185 Block the process for the given number of (fractional) seconds.
186
187 $time = EV::time
188 Returns the current time in (fractional) seconds since the epoch.
189
82 $time = EV::now 190 $time = EV::now
83 Returns the time in (fractional) seconds since the epoch. 191 $time = $loop->now
192 Returns the time the last event loop iteration has been started.
193 This is the time that (relative) timers are based on, and referring
194 to it is usually faster then calling EV::time.
84 195
85 $version = EV::version 196 EV::now_update
86 $method = EV::method 197 $loop->now_update
87 Return version string and event polling method used. 198 Establishes the current time by querying the kernel, updating the
199 time returned by "EV::now" in the progress. This is a costly
200 operation and is usually done automatically within "EV::loop".
88 201
89 EV::loop $flags # EV::LOOP_ONCE, EV::LOOP_ONESHOT 202 This function is rarely useful, but when some event callback runs
90 EV::loopexit $after 203 for a very long time without entering the event loop, updating
91 Exit any active loop or dispatch after $after seconds or immediately 204 libev's idea of the current time is a good idea.
92 if $after is missing or zero.
93 205
94 EV::dispatch 206 EV::suspend
95 Same as "EV::loop 0". 207 $loop->suspend
208 EV::resume
209 $loop->resume
210 These two functions suspend and resume a loop, for use when the loop
211 is not used for a while and timeouts should not be processed.
96 212
97 EV::event $callback 213 A typical use case would be an interactive program such as a game:
98 Creates a new event watcher waiting for nothing, calling the given 214 When the user presses "^Z" to suspend the game and resumes it an
99 callback. 215 hour later it would be best to handle timeouts as if no time had
216 actually passed while the program was suspended. This can be
217 achieved by calling "suspend" in your "SIGTSTP" handler, sending
218 yourself a "SIGSTOP" and calling "resume" directly afterwards to
219 resume timer processing.
100 220
221 Effectively, all "timer" watchers will be delayed by the time spend
222 between "suspend" and "resume", and all "periodic" watchers will be
223 rescheduled (that is, they will lose any events that would have
224 occured while suspended).
225
226 After calling "suspend" you must not call *any* function on the
227 given loop other than "resume", and you must not call "resume"
228 without a previous call to "suspend".
229
230 Calling "suspend"/"resume" has the side effect of updating the event
231 loop time (see "now_update").
232
233 $backend = EV::backend
234 $backend = $loop->backend
235 Returns an integer describing the backend used by libev
236 (EV::BACKEND_SELECT or EV::BACKEND_EPOLL).
237
238 EV::run [$flags]
239 $loop->run ([$flags])
240 Begin checking for events and calling callbacks. It returns when a
241 callback calls EV::unloop.
242
243 The $flags argument can be one of the following:
244
245 0 as above
246 EV::RUN_ONCE block at most once (wait, but do not loop)
247 EV::RUN_NOWAIT do not block at all (fetch/handle events but do not wait)
248
249 EV::break [$how]
250 $loop->break ([$how])
251 When called with no arguments or an argument of EV::BREAK_ONE, makes
252 the innermost call to EV::loop return.
253
254 When called with an argument of EV::BREAK_ALL, all calls to EV::loop
255 will return as fast as possible.
256
257 When called with an argument of EV::BREAK_CANCEL, any pending break
258 will be cancelled.
259
260 $count = EV::iteration
261 $count = $loop->iteration
262 Return the number of times the event loop has polled for new events.
263 Sometimes useful as a generation counter.
264
265 EV::once $fh_or_undef, $events, $timeout, $cb->($revents)
266 $loop->once ($fh_or_undef, $events, $timeout, $cb->($revents))
267 This function rolls together an I/O and a timer watcher for a single
268 one-shot event without the need for managing a watcher object.
269
270 If $fh_or_undef is a filehandle or file descriptor, then $events
271 must be a bitset containing either "EV::READ", "EV::WRITE" or
272 "EV::READ | EV::WRITE", indicating the type of I/O event you want to
273 wait for. If you do not want to wait for some I/O event, specify
274 "undef" for $fh_or_undef and 0 for $events).
275
276 If timeout is "undef" or negative, then there will be no timeout.
277 Otherwise a EV::timer with this value will be started.
278
279 When an error occurs or either the timeout or I/O watcher triggers,
280 then the callback will be called with the received event set (in
281 general you can expect it to be a combination of "EV::ERROR",
282 "EV::READ", "EV::WRITE" and "EV::TIMER").
283
284 EV::once doesn't return anything: the watchers stay active till
285 either of them triggers, then they will be stopped and freed, and
286 the callback invoked.
287
288 EV::feed_fd_event $fd, $revents
289 $loop->feed_fd_event ($fd, $revents)
290 Feed an event on a file descriptor into EV. EV will react to this
291 call as if the readyness notifications specified by $revents (a
292 combination of "EV::READ" and "EV::WRITE") happened on the file
293 descriptor $fd.
294
295 EV::feed_signal_event $signal
296 Feed a signal event into the default loop. EV will react to this
297 call as if the signal specified by $signal had occured.
298
299 EV::feed_signal $signal
300 Feed a signal event into EV - unlike "EV::feed_signal_event", this
301 works regardless of which loop has registered the signal, and is
302 mainly useful fro custom signal implementations.
303
304 EV::set_io_collect_interval $time
305 $loop->set_io_collect_interval ($time)
306 EV::set_timeout_collect_interval $time
307 $loop->set_timeout_collect_interval ($time)
308 These advanced functions set the minimum block interval when polling
309 for I/O events and the minimum wait interval for timer events. See
310 the libev documentation at
311 <http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod#FUNCTIONS_CONT
312 ROLLING_THE_EVENT_LOOP> (locally installed as EV::libev) for a more
313 detailed discussion.
314
315 $count = EV::pending_count
316 $count = $loop->pending_count
317 Returns the number of currently pending watchers.
318
319 EV::invoke_pending
320 $loop->invoke_pending
321 Invoke all currently pending watchers.
322
323WATCHER OBJECTS
324 A watcher is an object that gets created to record your interest in some
325 event. For instance, if you want to wait for STDIN to become readable,
326 you would create an EV::io watcher for that:
327
328 my $watcher = EV::io *STDIN, EV::READ, sub {
329 my ($watcher, $revents) = @_;
330 warn "yeah, STDIN should now be readable without blocking!\n"
331 };
332
333 All watchers can be active (waiting for events) or inactive (paused).
334 Only active watchers will have their callbacks invoked. All callbacks
335 will be called with at least two arguments: the watcher and a bitmask of
336 received events.
337
338 Each watcher type has its associated bit in revents, so you can use the
339 same callback for multiple watchers. The event mask is named after the
340 type, i.e. EV::child sets EV::CHILD, EV::prepare sets EV::PREPARE,
341 EV::periodic sets EV::PERIODIC and so on, with the exception of I/O
342 events (which can set both EV::READ and EV::WRITE bits).
343
344 In the rare case where one wants to create a watcher but not start it at
345 the same time, each constructor has a variant with a trailing "_ns" in
346 its name, e.g. EV::io has a non-starting variant EV::io_ns and so on.
347
348 Please note that a watcher will automatically be stopped when the
349 watcher object is destroyed, so you *need* to keep the watcher objects
350 returned by the constructors.
351
352 Also, all methods changing some aspect of a watcher (->set, ->priority,
353 ->fh and so on) automatically stop and start it again if it is active,
354 which means pending events get lost.
355
356 COMMON WATCHER METHODS
357 This section lists methods common to all watchers.
358
359 $w->start
360 Starts a watcher if it isn't active already. Does nothing to an
361 already active watcher. By default, all watchers start out in the
362 active state (see the description of the "_ns" variants if you need
363 stopped watchers).
364
365 $w->stop
366 Stop a watcher if it is active. Also clear any pending events
367 (events that have been received but that didn't yet result in a
368 callback invocation), regardless of whether the watcher was active
369 or not.
370
371 $bool = $w->is_active
372 Returns true if the watcher is active, false otherwise.
373
374 $current_data = $w->data
375 $old_data = $w->data ($new_data)
376 Queries a freely usable data scalar on the watcher and optionally
377 changes it. This is a way to associate custom data with a watcher:
378
379 my $w = EV::timer 60, 0, sub {
380 warn $_[0]->data;
381 };
382 $w->data ("print me!");
383
384 $current_cb = $w->cb
385 $old_cb = $w->cb ($new_cb)
386 Queries the callback on the watcher and optionally changes it. You
387 can do this at any time without the watcher restarting.
388
389 $current_priority = $w->priority
390 $old_priority = $w->priority ($new_priority)
391 Queries the priority on the watcher and optionally changes it.
392 Pending watchers with higher priority will be invoked first. The
393 valid range of priorities lies between EV::MAXPRI (default 2) and
394 EV::MINPRI (default -2). If the priority is outside this range it
395 will automatically be normalised to the nearest valid priority.
396
397 The default priority of any newly-created watcher is 0.
398
399 Note that the priority semantics have not yet been fleshed out and
400 are subject to almost certain change.
401
402 $w->invoke ($revents)
403 Call the callback *now* with the given event mask.
404
405 $w->feed_event ($revents)
406 Feed some events on this watcher into EV. EV will react to this call
407 as if the watcher had received the given $revents mask.
408
409 $revents = $w->clear_pending
410 If the watcher is pending, this function clears its pending status
411 and returns its $revents bitset (as if its callback was invoked). If
412 the watcher isn't pending it does nothing and returns 0.
413
414 $previous_state = $w->keepalive ($bool)
415 Normally, "EV::loop" will return when there are no active watchers
416 (which is a "deadlock" because no progress can be made anymore).
417 This is convenient because it allows you to start your watchers (and
418 your jobs), call "EV::loop" once and when it returns you know that
419 all your jobs are finished (or they forgot to register some watchers
420 for their task :).
421
422 Sometimes, however, this gets in your way, for example when the
423 module that calls "EV::loop" (usually the main program) is not the
424 same module as a long-living watcher (for example a DNS client
425 module written by somebody else even). Then you might want any
426 outstanding requests to be handled, but you would not want to keep
427 "EV::loop" from returning just because you happen to have this
428 long-running UDP port watcher.
429
430 In this case you can clear the keepalive status, which means that
431 even though your watcher is active, it won't keep "EV::loop" from
432 returning.
433
434 The initial value for keepalive is true (enabled), and you can
435 change it any time.
436
437 Example: Register an I/O watcher for some UDP socket but do not keep
438 the event loop from running just because of that watcher.
439
440 my $udp_socket = ...
441 my $udp_watcher = EV::io $udp_socket, EV::READ, sub { ... };
442 $udp_watcher->keepalive (0);
443
444 $loop = $w->loop
445 Return the loop that this watcher is attached to.
446
447WATCHER TYPES
448 Each of the following subsections describes a single watcher type.
449
450 I/O WATCHERS - is this file descriptor readable or writable?
101 my $w = EV::io $fileno_or_fh, $eventmask, $callback 451 $w = EV::io $fileno_or_fh, $eventmask, $callback
102 my $w = EV::io_ns $fileno_or_fh, $eventmask, $callback 452 $w = EV::io_ns $fileno_or_fh, $eventmask, $callback
453 $w = $loop->io ($fileno_or_fh, $eventmask, $callback)
454 $w = $loop->io_ns ($fileno_or_fh, $eventmask, $callback)
103 As long as the returned watcher object is alive, call the $callback 455 As long as the returned watcher object is alive, call the $callback
104 when the events specified in $eventmask happen. Initially, the 456 when at least one of events specified in $eventmask occurs.
105 timeout is disabled.
106 457
107 You can additionall set a timeout to occur on the watcher, but note
108 that this timeout will not be reset when you get an I/O event in the
109 EV::PERSIST case, and reaching a timeout will always stop the
110 watcher even in the EV::PERSIST case.
111
112 If you want a timeout to occur only after a specific time of
113 inactivity, set a repeating timeout and do NOT use EV::PERSIST.
114
115 Eventmask can be one or more of these constants ORed together: 458 The $eventmask can be one or more of these constants ORed together:
116 459
117 EV::READ wait until read() wouldn't block anymore 460 EV::READ wait until read() wouldn't block anymore
118 EV::WRITE wait until write() wouldn't block anymore 461 EV::WRITE wait until write() wouldn't block anymore
119 EV::PERSIST stay active after a (non-timeout) event occured
120 462
121 The "io_ns" variant doesn't add/start the newly created watcher. 463 The "io_ns" variant doesn't start (activate) the newly created
122
123 my $w = EV::timed_io $fileno_or_fh, $eventmask, $timeout, $callback
124 my $w = EV::timed_io_ns $fileno_or_fh, $eventmask, $timeout, $callback
125 Same as "io" and "io_ns", but also specifies a timeout (as if there
126 was a call to "$w->timeout ($timout, 1)". The persist flag is not
127 allowed and will automatically be cleared. The watcher will be
128 restarted after each event.
129
130 If the timeout is zero or undef, no timeout will be set, and a
131 normal watcher (with the persist flag set!) will be created.
132
133 This has the effect of timing out after the specified period of
134 inactivity has happened.
135
136 Due to the design of libevent, this is also relatively inefficient,
137 having one or two io watchers and a separate timeout watcher that
138 you reset on activity (by calling its "start" method) is usually
139 more efficient.
140
141 my $w = EV::timer $after, $repeat, $callback
142 my $w = EV::timer_ns $after, $repeat, $callback
143 Calls the callback after $after seconds. If $repeat is true, the
144 timer will be restarted after the callback returns. This means that
145 the callback would be called roughly every $after seconds, prolonged
146 by the time the callback takes.
147
148 The "timer_ns" variant doesn't add/start the newly created watcher.
149
150 my $w = EV::timer_abs $at, $interval, $callback
151 my $w = EV::timer_abs_ns $at, $interval, $callback
152 Similar to EV::timer, but the time is given as an absolute point in
153 time ($at), plus an optional $interval.
154
155 If the $interval is zero, then the callback will be called at the
156 time $at if that is in the future, or as soon as possible if its in
157 the past. It will not automatically repeat.
158
159 If the $interval is nonzero, then the watcher will always be
160 scheduled to time out at the next "$at + integer * $interval" time.
161
162 This can be used to schedule a callback to run at very regular
163 intervals, as long as the processing time is less then the interval
164 (otherwise obviously events will be skipped).
165
166 Another way to think about it (for the mathematically inclined) is
167 that "timer_abs" will try to tun the callback at the next possible
168 time where "$time = $at (mod $interval)", regardless of any time
169 jumps.
170
171 The "timer_abs_ns" variant doesn't add/start the newly created
172 watcher. 464 watcher.
173 465
174 my $w = EV::signal $signal, $callback 466 $w->set ($fileno_or_fh, $eventmask)
175 my $w = EV::signal_ns $signal, $callback 467 Reconfigures the watcher, see the constructor above for details. Can
176 Call the callback when $signal is received (the signal can be 468 be called at any time.
177 specified by number or by name, just as with kill or %SIG). Signal
178 watchers are persistent no natter what.
179
180 EV will grab the signal for the process (the kernel only allows one
181 component to receive signals) when you start a signal watcher, and
182 removes it again when you stop it. Pelr does the same when you
183 add/remove callbacks to %SIG, so watch out.
184
185 Unfortunately, only one handler can be registered per signal. Screw
186 libevent.
187
188 The "signal_ns" variant doesn't add/start the newly created watcher.
189
190THE EV::Event CLASS
191 All EV functions creating an event watcher (designated by "my $w ="
192 above) support the following methods on the returned watcher object:
193
194 $w->add ($timeout)
195 Stops and (re-)starts the event watcher, setting the optional
196 timeout to the given value, or clearing the timeout if none is
197 given.
198
199 $w->start
200 Stops and (re-)starts the event watcher without touching the
201 timeout.
202
203 $w->del
204 $w->stop
205 Stop the event watcher if it was started.
206
207 $current_callback = $w->cb
208 $old_callback = $w->cb ($new_callback)
209 Return the previously set callback and optionally set a new one.
210 469
211 $current_fh = $w->fh 470 $current_fh = $w->fh
212 $old_fh = $w->fh ($new_fh) 471 $old_fh = $w->fh ($new_fh)
213 Returns the previously set filehandle and optionally set a new one 472 Returns the previously set filehandle and optionally set a new one.
214 (also clears the EV::SIGNAL flag when setting a filehandle).
215
216 $current_signal = $w->signal
217 $old_signal = $w->signal ($new_signal)
218 Returns the previously set signal number and optionally set a new
219 one (also sets the EV::SIGNAL flag when setting a signal).
220 473
221 $current_eventmask = $w->events 474 $current_eventmask = $w->events
222 $old_eventmask = $w->events ($new_eventmask) 475 $old_eventmask = $w->events ($new_eventmask)
223 Returns the previously set event mask and optionally set a new one. 476 Returns the previously set event mask and optionally set a new one.
224 477
478 TIMER WATCHERS - relative and optionally repeating timeouts
479 $w = EV::timer $after, $repeat, $callback
480 $w = EV::timer_ns $after, $repeat, $callback
481 $w = $loop->timer ($after, $repeat, $callback)
482 $w = $loop->timer_ns ($after, $repeat, $callback)
483 Calls the callback after $after seconds (which may be fractional).
484 If $repeat is non-zero, the timer will be restarted (with the
485 $repeat value as $after) after the callback returns.
486
487 This means that the callback would be called roughly after $after
488 seconds, and then every $repeat seconds. The timer does his best not
489 to drift, but it will not invoke the timer more often then once per
490 event loop iteration, and might drift in other cases. If that isn't
491 acceptable, look at EV::periodic, which can provide long-term stable
492 timers.
493
494 The timer is based on a monotonic clock, that is, if somebody is
495 sitting in front of the machine while the timer is running and
496 changes the system clock, the timer will nevertheless run (roughly)
497 the same time.
498
499 The "timer_ns" variant doesn't start (activate) the newly created
500 watcher.
501
225 $w->timeout ($after, $repeat) 502 $w->set ($after, $repeat)
226 Resets the timeout (see "EV::timer" for details). 503 Reconfigures the watcher, see the constructor above for details. Can
504 be called at any time.
227 505
506 $w->again
507 Similar to the "start" method, but has special semantics for
508 repeating timers:
509
510 If the timer is active and non-repeating, it will be stopped.
511
512 If the timer is active and repeating, reset the timeout to occur
513 $repeat seconds after now.
514
515 If the timer is inactive and repeating, start it using the repeat
516 value.
517
518 Otherwise do nothing.
519
520 This behaviour is useful when you have a timeout for some IO
521 operation. You create a timer object with the same value for $after
522 and $repeat, and then, in the read/write watcher, run the "again"
523 method on the timeout.
524
525 PERIODIC WATCHERS - to cron or not to cron?
526 $w = EV::periodic $at, $interval, $reschedule_cb, $callback
527 $w = EV::periodic_ns $at, $interval, $reschedule_cb, $callback
528 $w = $loop->periodic ($at, $interval, $reschedule_cb, $callback)
529 $w = $loop->periodic_ns ($at, $interval, $reschedule_cb, $callback)
530 Similar to EV::timer, but is not based on relative timeouts but on
531 absolute times. Apart from creating "simple" timers that trigger
532 "at" the specified time, it can also be used for non-drifting
533 absolute timers and more complex, cron-like, setups that are not
534 adversely affected by time jumps (i.e. when the system clock is
535 changed by explicit date -s or other means such as ntpd). It is also
536 the most complex watcher type in EV.
537
538 It has three distinct "modes":
539
540 * absolute timer ($interval = $reschedule_cb = 0)
541
542 This time simply fires at the wallclock time $at and doesn't
543 repeat. It will not adjust when a time jump occurs, that is, if
544 it is to be run at January 1st 2011 then it will run when the
545 system time reaches or surpasses this time.
546
547 * repeating interval timer ($interval > 0, $reschedule_cb = 0)
548
549 In this mode the watcher will always be scheduled to time out at
550 the next "$at + N * $interval" time (for some integer N) and
551 then repeat, regardless of any time jumps.
552
553 This can be used to create timers that do not drift with respect
554 to system time:
555
556 my $hourly = EV::periodic 0, 3600, 0, sub { print "once/hour\n" };
557
558 That doesn't mean there will always be 3600 seconds in between
559 triggers, but only that the the clalback will be called when the
560 system time shows a full hour (UTC).
561
562 Another way to think about it (for the mathematically inclined)
563 is that EV::periodic will try to run the callback in this mode
564 at the next possible time where "$time = $at (mod $interval)",
565 regardless of any time jumps.
566
567 * manual reschedule mode ($reschedule_cb = coderef)
568
569 In this mode $interval and $at are both being ignored. Instead,
570 each time the periodic watcher gets scheduled, the reschedule
571 callback ($reschedule_cb) will be called with the watcher as
572 first, and the current time as second argument.
573
574 *This callback MUST NOT stop or destroy this or any other
575 periodic watcher, ever, and MUST NOT call any event loop
576 functions or methods*. If you need to stop it, return 1e30 and
577 stop it afterwards. You may create and start a "EV::prepare"
578 watcher for this task.
579
580 It must return the next time to trigger, based on the passed
581 time value (that is, the lowest time value larger than or equal
582 to to the second argument). It will usually be called just
583 before the callback will be triggered, but might be called at
584 other times, too.
585
586 This can be used to create very complex timers, such as a timer
587 that triggers on each midnight, local time (actually 24 hours
588 after the last midnight, to keep the example simple. If you know
589 a way to do it correctly in about the same space (without
590 requiring elaborate modules), drop me a note :):
591
592 my $daily = EV::periodic 0, 0, sub {
593 my ($w, $now) = @_;
594
595 use Time::Local ();
596 my (undef, undef, undef, $d, $m, $y) = localtime $now;
597 86400 + Time::Local::timelocal 0, 0, 0, $d, $m, $y
598 }, sub {
599 print "it's midnight or likely shortly after, now\n";
600 };
601
602 The "periodic_ns" variant doesn't start (activate) the newly created
603 watcher.
604
605 $w->set ($at, $interval, $reschedule_cb)
606 Reconfigures the watcher, see the constructor above for details. Can
607 be called at any time.
608
609 $w->again
610 Simply stops and starts the watcher again.
611
612 $time = $w->at
613 Return the time that the watcher is expected to trigger next.
614
615 SIGNAL WATCHERS - signal me when a signal gets signalled!
616 $w = EV::signal $signal, $callback
617 $w = EV::signal_ns $signal, $callback
618 $w = $loop->signal ($signal, $callback)
619 $w = $loop->signal_ns ($signal, $callback)
620 Call the callback when $signal is received (the signal can be
621 specified by number or by name, just as with "kill" or %SIG).
622
623 Only one event loop can grab a given signal - attempting to grab the
624 same signal from two EV loops will crash the program immediately or
625 cause data corruption.
626
627 EV will grab the signal for the process (the kernel only allows one
628 component to receive a signal at a time) when you start a signal
629 watcher, and removes it again when you stop it. Perl does the same
630 when you add/remove callbacks to %SIG, so watch out.
631
632 You can have as many signal watchers per signal as you want.
633
634 The "signal_ns" variant doesn't start (activate) the newly created
635 watcher.
636
637 $w->set ($signal)
638 Reconfigures the watcher, see the constructor above for details. Can
639 be called at any time.
640
641 $current_signum = $w->signal
642 $old_signum = $w->signal ($new_signal)
643 Returns the previously set signal (always as a number not name) and
644 optionally set a new one.
645
646 CHILD WATCHERS - watch out for process status changes
647 $w = EV::child $pid, $trace, $callback
648 $w = EV::child_ns $pid, $trace, $callback
649 $w = $loop->child ($pid, $trace, $callback)
650 $w = $loop->child_ns ($pid, $trace, $callback)
651 Call the callback when a status change for pid $pid (or any pid if
652 $pid is 0) has been received (a status change happens when the
653 process terminates or is killed, or, when trace is true,
654 additionally when it is stopped or continued). More precisely: when
655 the process receives a "SIGCHLD", EV will fetch the outstanding
656 exit/wait status for all changed/zombie children and call the
657 callback.
658
659 It is valid (and fully supported) to install a child watcher after a
660 child has exited but before the event loop has started its next
661 iteration (for example, first you "fork", then the new child process
662 might exit, and only then do you install a child watcher in the
663 parent for the new pid).
664
665 You can access both exit (or tracing) status and pid by using the
666 "rstatus" and "rpid" methods on the watcher object.
667
668 You can have as many pid watchers per pid as you want, they will all
669 be called.
670
671 The "child_ns" variant doesn't start (activate) the newly created
672 watcher.
673
674 $w->set ($pid, $trace)
675 Reconfigures the watcher, see the constructor above for details. Can
676 be called at any time.
677
678 $current_pid = $w->pid
679 Returns the previously set process id and optionally set a new one.
680
681 $exit_status = $w->rstatus
682 Return the exit/wait status (as returned by waitpid, see the waitpid
683 entry in perlfunc).
684
685 $pid = $w->rpid
686 Return the pid of the awaited child (useful when you have installed
687 a watcher for all pids).
688
689 STAT WATCHERS - did the file attributes just change?
690 $w = EV::stat $path, $interval, $callback
691 $w = EV::stat_ns $path, $interval, $callback
692 $w = $loop->stat ($path, $interval, $callback)
693 $w = $loop->stat_ns ($path, $interval, $callback)
694 Call the callback when a file status change has been detected on
695 $path. The $path does not need to exist, changing from "path exists"
696 to "path does not exist" is a status change like any other.
697
698 The $interval is a recommended polling interval for systems where
699 OS-supported change notifications don't exist or are not supported.
700 If you use 0 then an unspecified default is used (which is highly
701 recommended!), which is to be expected to be around five seconds
702 usually.
703
704 This watcher type is not meant for massive numbers of stat watchers,
705 as even with OS-supported change notifications, this can be
706 resource-intensive.
707
708 The "stat_ns" variant doesn't start (activate) the newly created
709 watcher.
710
711 ... = $w->stat
712 This call is very similar to the perl "stat" built-in: It stats
713 (using "lstat") the path specified in the watcher and sets perls
714 stat cache (as well as EV's idea of the current stat values) to the
715 values found.
716
717 In scalar context, a boolean is return indicating success or failure
718 of the stat. In list context, the same 13-value list as with stat is
719 returned (except that the blksize and blocks fields are not
720 reliable).
721
722 In the case of an error, errno is set to "ENOENT" (regardless of the
723 actual error value) and the "nlink" value is forced to zero (if the
724 stat was successful then nlink is guaranteed to be non-zero).
725
726 See also the next two entries for more info.
727
728 ... = $w->attr
729 Just like "$w->stat", but without the initial stat'ing: this returns
730 the values most recently detected by EV. See the next entry for more
731 info.
732
733 ... = $w->prev
734 Just like "$w->stat", but without the initial stat'ing: this returns
735 the previous set of values, before the change.
736
737 That is, when the watcher callback is invoked, "$w->prev" will be
738 set to the values found *before* a change was detected, while
739 "$w->attr" returns the values found leading to the change detection.
740 The difference (if any) between "prev" and "attr" is what triggered
741 the callback.
742
743 If you did something to the filesystem object and do not want to
744 trigger yet another change, you can call "stat" to update EV's idea
745 of what the current attributes are.
746
228 $w->timeout_abs ($at, $interval) 747 $w->set ($path, $interval)
229 Resets the timeout (see "EV::timer_abs" for details). 748 Reconfigures the watcher, see the constructor above for details. Can
749 be called at any time.
230 750
231 $w->priority_set ($priority) 751 $current_path = $w->path
232 Set the priority of the watcher to $priority (0 <= $priority < 752 $old_path = $w->path ($new_path)
233 $EV::NPRI). 753 Returns the previously set path and optionally set a new one.
234 754
235BUGS 755 $current_interval = $w->interval
236 Lots. Libevent itself isn't well tested and rather buggy, and this 756 $old_interval = $w->interval ($new_interval)
237 module is quite new at the moment. 757 Returns the previously set interval and optionally set a new one.
758 Can be used to query the actual interval used.
238 759
239 Please note that the epoll method is not, in general, reliable in 760 IDLE WATCHERS - when you've got nothing better to do...
240 programs that use fork (even if no libveent calls are being made in the 761 $w = EV::idle $callback
241 forked process). If your program behaves erratically, try setting the 762 $w = EV::idle_ns $callback
242 environment variable "EVENT_NOEPOLL" first when running the program. 763 $w = $loop->idle ($callback)
764 $w = $loop->idle_ns ($callback)
765 Call the callback when there are no other pending watchers of the
766 same or higher priority (excluding check, prepare and other idle
767 watchers of the same or lower priority, of course). They are called
768 idle watchers because when the watcher is the highest priority
769 pending event in the process, the process is considered to be idle
770 at that priority.
243 771
244 In general, if you fork, then you can only use the EV module in one of 772 If you want a watcher that is only ever called when *no* other
245 the children. 773 events are outstanding you have to set the priority to "EV::MINPRI".
774
775 The process will not block as long as any idle watchers are active,
776 and they will be called repeatedly until stopped.
777
778 For example, if you have idle watchers at priority 0 and 1, and an
779 I/O watcher at priority 0, then the idle watcher at priority 1 and
780 the I/O watcher will always run when ready. Only when the idle
781 watcher at priority 1 is stopped and the I/O watcher at priority 0
782 is not pending with the 0-priority idle watcher be invoked.
783
784 The "idle_ns" variant doesn't start (activate) the newly created
785 watcher.
786
787 PREPARE WATCHERS - customise your event loop!
788 $w = EV::prepare $callback
789 $w = EV::prepare_ns $callback
790 $w = $loop->prepare ($callback)
791 $w = $loop->prepare_ns ($callback)
792 Call the callback just before the process would block. You can still
793 create/modify any watchers at this point.
794
795 See the EV::check watcher, below, for explanations and an example.
796
797 The "prepare_ns" variant doesn't start (activate) the newly created
798 watcher.
799
800 CHECK WATCHERS - customise your event loop even more!
801 $w = EV::check $callback
802 $w = EV::check_ns $callback
803 $w = $loop->check ($callback)
804 $w = $loop->check_ns ($callback)
805 Call the callback just after the process wakes up again (after it
806 has gathered events), but before any other callbacks have been
807 invoked.
808
809 This can be used to integrate other event-based software into the EV
810 mainloop: You register a prepare callback and in there, you create
811 io and timer watchers as required by the other software. Here is a
812 real-world example of integrating Net::SNMP (with some details left
813 out):
814
815 our @snmp_watcher;
816
817 our $snmp_prepare = EV::prepare sub {
818 # do nothing unless active
819 $dispatcher->{_event_queue_h}
820 or return;
821
822 # make the dispatcher handle any outstanding stuff
823 ... not shown
824
825 # create an I/O watcher for each and every socket
826 @snmp_watcher = (
827 (map { EV::io $_, EV::READ, sub { } }
828 keys %{ $dispatcher->{_descriptors} }),
829
830 EV::timer +($event->[Net::SNMP::Dispatcher::_ACTIVE]
831 ? $event->[Net::SNMP::Dispatcher::_TIME] - EV::now : 0),
832 0, sub { },
833 );
834 };
835
836 The callbacks are irrelevant (and are not even being called), the
837 only purpose of those watchers is to wake up the process as soon as
838 one of those events occurs (socket readable, or timer timed out).
839 The corresponding EV::check watcher will then clean up:
840
841 our $snmp_check = EV::check sub {
842 # destroy all watchers
843 @snmp_watcher = ();
844
845 # make the dispatcher handle any new stuff
846 ... not shown
847 };
848
849 The callbacks of the created watchers will not be called as the
850 watchers are destroyed before this can happen (remember EV::check
851 gets called first).
852
853 The "check_ns" variant doesn't start (activate) the newly created
854 watcher.
855
856 EV::CHECK constant issues
857 Like all other watcher types, there is a bitmask constant for use in
858 $revents and other places. The "EV::CHECK" is special as it has the
859 same name as the "CHECK" sub called by Perl. This doesn't cause big
860 issues on newer perls (beginning with 5.8.9), but it means thatthe
861 constant must be *inlined*, i.e. runtime calls will not work. That
862 means that as long as you always "use EV" and then "EV::CHECK" you
863 are on the safe side.
864
865 FORK WATCHERS - the audacity to resume the event loop after a fork
866 Fork watchers are called when a "fork ()" was detected. The invocation
867 is done before the event loop blocks next and before "check" watchers
868 are being called, and only in the child after the fork.
869
870 $w = EV::fork $callback
871 $w = EV::fork_ns $callback
872 $w = $loop->fork ($callback)
873 $w = $loop->fork_ns ($callback)
874 Call the callback before the event loop is resumed in the child
875 process after a fork.
876
877 The "fork_ns" variant doesn't start (activate) the newly created
878 watcher.
879
880 EMBED WATCHERS - when one backend isn't enough...
881 This is a rather advanced watcher type that lets you embed one event
882 loop into another (currently only IO events are supported in the
883 embedded loop, other types of watchers might be handled in a delayed or
884 incorrect fashion and must not be used).
885
886 See the libev documentation at
887 <http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod#code_ev_embed_code
888 _when_one_backend_> (locally installed as EV::libev) for more details.
889
890 In short, this watcher is most useful on BSD systems without working
891 kqueue to still be able to handle a large number of sockets:
892
893 my $socket_loop;
894
895 # check wether we use SELECT or POLL _and_ KQUEUE is supported
896 if (
897 (EV::backend & (EV::BACKEND_POLL | EV::BACKEND_SELECT))
898 && (EV::supported_backends & EV::embeddable_backends & EV::BACKEND_KQUEUE)
899 ) {
900 # use kqueue for sockets
901 $socket_loop = new EV::Loop EV::BACKEND_KQUEUE | EV::FLAG_NOENV;
902 }
903
904 # use the default loop otherwise
905 $socket_loop ||= EV::default_loop;
906
907 $w = EV::embed $otherloop[, $callback]
908 $w = EV::embed_ns $otherloop[, $callback]
909 $w = $loop->embed ($otherloop[, $callback])
910 $w = $loop->embed_ns ($otherloop[, $callback])
911 Call the callback when the embedded event loop ($otherloop) has any
912 I/O activity. The $callback is optional: if it is missing, then the
913 embedded event loop will be managed automatically (which is
914 recommended), otherwise you have to invoke "sweep" yourself.
915
916 The "embed_ns" variant doesn't start (activate) the newly created
917 watcher.
918
919 ASYNC WATCHERS - how to wake up another event loop
920 Async watchers are provided by EV, but have little use in perl directly,
921 as perl neither supports threads running in parallel nor direct access
922 to signal handlers or other contexts where they could be of value.
923
924 It is, however, possible to use them from the XS level.
925
926 Please see the libev documentation for further details.
927
928 $w = EV::async $callback
929 $w = EV::async_ns $callback
930 $w->send
931 $bool = $w->async_pending
932
933PERL SIGNALS
934 While Perl signal handling (%SIG) is not affected by EV, the behaviour
935 with EV is as the same as any other C library: Perl-signals will only be
936 handled when Perl runs, which means your signal handler might be invoked
937 only the next time an event callback is invoked.
938
939 The solution is to use EV signal watchers (see "EV::signal"), which will
940 ensure proper operations with regards to other event watchers.
941
942 If you cannot do this for whatever reason, you can also force a watcher
943 to be called on every event loop iteration by installing a "EV::check"
944 watcher:
945
946 my $async_check = EV::check sub { };
947
948 This ensures that perl gets into control for a short time to handle any
949 pending signals, and also ensures (slightly) slower overall operation.
950
951ITHREADS
952 Ithreads are not supported by this module in any way. Perl
953 pseudo-threads is evil stuff and must die. Real threads as provided by
954 Coro are fully supported (and enhanced support is available via
955 Coro::EV).
956
957FORK
958 Most of the "improved" event delivering mechanisms of modern operating
959 systems have quite a few problems with fork(2) (to put it bluntly: it is
960 not supported and usually destructive). Libev makes it possible to work
961 around this by having a function that recreates the kernel state after
962 fork in the child.
963
964 On non-win32 platforms, this module requires the pthread_atfork
965 functionality to do this automatically for you. This function is quite
966 buggy on most BSDs, though, so YMMV. The overhead for this is quite
967 negligible, because everything the function currently does is set a flag
968 that is checked only when the event loop gets used the next time, so
969 when you do fork but not use EV, the overhead is minimal.
970
971 On win32, there is no notion of fork so all this doesn't apply, of
972 course.
246 973
247SEE ALSO 974SEE ALSO
248 L<EV::DNS>, L<event(3)>, L<event.h>, L<evdns.h>. 975 EV::MakeMaker - MakeMaker interface to XS API, EV::ADNS (asynchronous
249 L<EV::AnyEvent>. 976 DNS), Glib::EV (makes Glib/Gtk2 use EV as event loop), EV::Glib (embed
977 Glib into EV), Coro::EV (efficient thread integration), Net::SNMP::EV
978 (asynchronous SNMP), AnyEvent for event-loop agnostic and portable event
979 driven programming.
250 980
251AUTHOR 981AUTHOR
252 Marc Lehmann <schmorp@schmorp.de> 982 Marc Lehmann <schmorp@schmorp.de>
253 http://home.schmorp.de/ 983 http://home.schmorp.de/
254 984

Diff Legend

– Removed lines
+ Added lines
< Changed lines
> Changed lines