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 1.35 by root, Thu Dec 31 06:59:47 2009 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::loop; # 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::loop EV::LOOP_ONESHOT; # 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::loop EV::LOOP_NONBLOCK; # try to handle same events, but do not block
61 54
62DESCRIPTION 55DESCRIPTION
63 This module provides an interface to libevent 56 This module provides an interface to libev
64 (<http://monkey.org/~provos/libevent/>). You probably should acquaint 57 (<http://software.schmorp.de/pkg/libev.html>). While the documentation
65 yourself with its documentation and source code to be able to use this 58 below is comprehensive, one might also consult the documentation of
66 module fully. 59 libev itself (<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod> or
60 perldoc EV::libev) for more subtle details on watcher semantics or some
61 discussion on the available backends, or how to force a specific backend
62 with "LIBEV_FLAGS", or just about in any case because it has much more
63 detailed information.
67 64
68 Please note thta this module disables the libevent EPOLL method by 65 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. 66 can use it through the AnyEvent module, stay portable to other event
67 loops (if you don't rely on any watcher types not available through it)
68 and still be faster than with any other event loop currently supported
69 in Perl.
70
71 MODULE EXPORTS
72 This module does not export any symbols.
73
74EVENT LOOPS
75 EV supports multiple event loops: There is a single "default event loop"
76 that can handle everything including signals and child watchers, and any
77 number of "dynamic event loops" that can use different backends (with
78 various limitations), but no child and signal watchers.
79
80 You do not have to do anything to create the default event loop: When
81 the module is loaded a suitable backend is selected on the premise of
82 selecting a working backend (which for example rules out kqueue on most
83 BSDs). Modules should, unless they have "special needs" always use the
84 default loop as this is fastest (perl-wise), best supported by other
85 modules (e.g. AnyEvent or Coro) and most portable event loop.
86
87 For specific programs you can create additional event loops dynamically.
88
89 If you want to take advantage of kqueue (which often works properly for
90 sockets only) even though the default loop doesn't enable it, you can
91 *embed* a kqueue loop into the default loop: running the default loop
92 will then also service the kqueue loop to some extent. See the example
93 in the section about embed watchers for an example on how to achieve
94 that.
95
96 $loop = new EV::Loop [$flags]
97 Create a new event loop as per the specified flags. Please refer to
98 the "ev_loop_new ()" function description in the libev documentation
99 (<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod#GLOBAL_FUNCTI
100 ONS>, or locally-installed as EV::libev manpage) for more info.
101
102 The loop will automatically be destroyed when it is no longer
103 referenced by any watcher and the loop object goes out of scope.
104
105 If you are not embedding the loop, then Using "EV::FLAG_FORKCHECK"
106 is recommended, as only the default event loop is protected by this
107 module. If you *are* embedding this loop in the default loop, this
108 is not necessary, as "EV::embed" automatically does the right thing
109 on fork.
110
111 $loop->loop_fork
112 Must be called after a fork in the child, before entering or
113 continuing the event loop. An alternative is to use
114 "EV::FLAG_FORKCHECK" which calls this function automatically, at
115 some performance loss (refer to the libev documentation).
116
117 $loop->loop_verify
118 Calls "ev_verify" to make internal consistency checks (for debugging
119 libev) and abort the program if any data structures were found to be
120 corrupted.
121
122 $loop = EV::default_loop [$flags]
123 Return the default loop (which is a singleton object). Since this
124 module already creates the default loop with default flags,
125 specifying flags here will not have any effect unless you destroy
126 the default loop first, which isn't supported. So in short: don't do
127 it, and if you break it, you get to keep the pieces.
70 128
71BASIC INTERFACE 129BASIC INTERFACE
72 $EV::NPRI
73 How many priority levels are available.
74
75 $EV::DIED 130 $EV::DIED
76 Must contain a reference to a function that is called when a 131 Must contain a reference to a function that is called when a
77 callback throws an exception (with $@ containing thr error). The 132 callback throws an exception (with $@ containing the error). The
78 default prints an informative message and continues. 133 default prints an informative message and continues.
79 134
80 If this callback throws an exception it will be silently ignored. 135 If this callback throws an exception it will be silently ignored.
81 136
137 $flags = EV::supported_backends
138 $flags = EV::recommended_backends
139 $flags = EV::embeddable_backends
140 Returns the set (see "EV::BACKEND_*" flags) of backends supported by
141 this instance of EV, the set of recommended backends (supposed to be
142 good) for this platform and the set of embeddable backends (see
143 EMBED WATCHERS).
144
145 EV::sleep $seconds
146 Block the process for the given number of (fractional) seconds.
147
148 $time = EV::time
149 Returns the current time in (fractional) seconds since the epoch.
150
82 $time = EV::now 151 $time = EV::now
83 Returns the time in (fractional) seconds since the epoch. 152 $time = $loop->now
153 Returns the time the last event loop iteration has been started.
154 This is the time that (relative) timers are based on, and referring
155 to it is usually faster then calling EV::time.
84 156
85 $version = EV::version 157 EV::now_update
86 $method = EV::method 158 $loop->now_update
87 Return version string and event polling method used. 159 Establishes the current time by querying the kernel, updating the
160 time returned by "EV::now" in the progress. This is a costly
161 operation and is usually done automatically within "EV::loop".
88 162
89 EV::loop $flags # EV::LOOP_ONCE, EV::LOOP_ONESHOT 163 This function is rarely useful, but when some event callback runs
90 EV::loopexit $after 164 for a very long time without entering the event loop, updating
91 Exit any active loop or dispatch after $after seconds or immediately 165 libev's idea of the current time is a good idea.
92 if $after is missing or zero.
93 166
94 EV::dispatch 167 EV::suspend
95 Same as "EV::loop 0". 168 $loop->suspend
169 EV::resume
170 $loop->resume
171 These two functions suspend and resume a loop, for use when the loop
172 is not used for a while and timeouts should not be processed.
96 173
97 EV::event $callback 174 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 175 When the user presses "^Z" to suspend the game and resumes it an
99 callback. 176 hour later it would be best to handle timeouts as if no time had
177 actually passed while the program was suspended. This can be
178 achieved by calling "suspend" in your "SIGTSTP" handler, sending
179 yourself a "SIGSTOP" and calling "resume" directly afterwards to
180 resume timer processing.
100 181
182 Effectively, all "timer" watchers will be delayed by the time spend
183 between "suspend" and "resume", and all "periodic" watchers will be
184 rescheduled (that is, they will lose any events that would have
185 occured while suspended).
186
187 After calling "suspend" you must not call *any* function on the
188 given loop other than "resume", and you must not call "resume"
189 without a previous call to "suspend".
190
191 Calling "suspend"/"resume" has the side effect of updating the event
192 loop time (see "now_update").
193
194 $backend = EV::backend
195 $backend = $loop->backend
196 Returns an integer describing the backend used by libev
197 (EV::BACKEND_SELECT or EV::BACKEND_EPOLL).
198
199 EV::loop [$flags]
200 $loop->loop ([$flags])
201 Begin checking for events and calling callbacks. It returns when a
202 callback calls EV::unloop.
203
204 The $flags argument can be one of the following:
205
206 0 as above
207 EV::LOOP_ONESHOT block at most once (wait, but do not loop)
208 EV::LOOP_NONBLOCK do not block at all (fetch/handle events but do not wait)
209
210 EV::unloop [$how]
211 $loop->unloop ([$how])
212 When called with no arguments or an argument of EV::UNLOOP_ONE,
213 makes the innermost call to EV::loop return.
214
215 When called with an argument of EV::UNLOOP_ALL, all calls to
216 EV::loop will return as fast as possible.
217
218 $count = EV::loop_count
219 $count = $loop->loop_count
220 Return the number of times the event loop has polled for new events.
221 Sometimes useful as a generation counter.
222
223 EV::once $fh_or_undef, $events, $timeout, $cb->($revents)
224 $loop->once ($fh_or_undef, $events, $timeout, $cb->($revents))
225 This function rolls together an I/O and a timer watcher for a single
226 one-shot event without the need for managing a watcher object.
227
228 If $fh_or_undef is a filehandle or file descriptor, then $events
229 must be a bitset containing either "EV::READ", "EV::WRITE" or
230 "EV::READ | EV::WRITE", indicating the type of I/O event you want to
231 wait for. If you do not want to wait for some I/O event, specify
232 "undef" for $fh_or_undef and 0 for $events).
233
234 If timeout is "undef" or negative, then there will be no timeout.
235 Otherwise a EV::timer with this value will be started.
236
237 When an error occurs or either the timeout or I/O watcher triggers,
238 then the callback will be called with the received event set (in
239 general you can expect it to be a combination of "EV::ERROR",
240 "EV::READ", "EV::WRITE" and "EV::TIMEOUT").
241
242 EV::once doesn't return anything: the watchers stay active till
243 either of them triggers, then they will be stopped and freed, and
244 the callback invoked.
245
246 EV::feed_fd_event ($fd, $revents)
247 $loop->feed_fd_event ($fd, $revents)
248 Feed an event on a file descriptor into EV. EV will react to this
249 call as if the readyness notifications specified by $revents (a
250 combination of "EV::READ" and "EV::WRITE") happened on the file
251 descriptor $fd.
252
253 EV::feed_signal_event ($signal)
254 Feed a signal event into EV. EV will react to this call as if the
255 signal specified by $signal had occured.
256
257 EV::set_io_collect_interval $time
258 $loop->set_io_collect_interval ($time)
259 EV::set_timeout_collect_interval $time
260 $loop->set_timeout_collect_interval ($time)
261 These advanced functions set the minimum block interval when polling
262 for I/O events and the minimum wait interval for timer events. See
263 the libev documentation at
264 <http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod#FUNCTIONS_CONT
265 ROLLING_THE_EVENT_LOOP> (locally installed as EV::libev) for a more
266 detailed discussion.
267
268 $count = EV::pending_count
269 $count = $loop->pending_count
270 Returns the number of currently pending watchers.
271
272 EV::invoke_pending
273 $loop->invoke_pending
274 Invoke all currently pending watchers.
275
276WATCHER OBJECTS
277 A watcher is an object that gets created to record your interest in some
278 event. For instance, if you want to wait for STDIN to become readable,
279 you would create an EV::io watcher for that:
280
281 my $watcher = EV::io *STDIN, EV::READ, sub {
282 my ($watcher, $revents) = @_;
283 warn "yeah, STDIN should now be readable without blocking!\n"
284 };
285
286 All watchers can be active (waiting for events) or inactive (paused).
287 Only active watchers will have their callbacks invoked. All callbacks
288 will be called with at least two arguments: the watcher and a bitmask of
289 received events.
290
291 Each watcher type has its associated bit in revents, so you can use the
292 same callback for multiple watchers. The event mask is named after the
293 type, i.e. EV::child sets EV::CHILD, EV::prepare sets EV::PREPARE,
294 EV::periodic sets EV::PERIODIC and so on, with the exception of I/O
295 events (which can set both EV::READ and EV::WRITE bits), and EV::timer
296 (which uses EV::TIMEOUT).
297
298 In the rare case where one wants to create a watcher but not start it at
299 the same time, each constructor has a variant with a trailing "_ns" in
300 its name, e.g. EV::io has a non-starting variant EV::io_ns and so on.
301
302 Please note that a watcher will automatically be stopped when the
303 watcher object is destroyed, so you *need* to keep the watcher objects
304 returned by the constructors.
305
306 Also, all methods changing some aspect of a watcher (->set, ->priority,
307 ->fh and so on) automatically stop and start it again if it is active,
308 which means pending events get lost.
309
310 COMMON WATCHER METHODS
311 This section lists methods common to all watchers.
312
313 $w->start
314 Starts a watcher if it isn't active already. Does nothing to an
315 already active watcher. By default, all watchers start out in the
316 active state (see the description of the "_ns" variants if you need
317 stopped watchers).
318
319 $w->stop
320 Stop a watcher if it is active. Also clear any pending events
321 (events that have been received but that didn't yet result in a
322 callback invocation), regardless of whether the watcher was active
323 or not.
324
325 $bool = $w->is_active
326 Returns true if the watcher is active, false otherwise.
327
328 $current_data = $w->data
329 $old_data = $w->data ($new_data)
330 Queries a freely usable data scalar on the watcher and optionally
331 changes it. This is a way to associate custom data with a watcher:
332
333 my $w = EV::timer 60, 0, sub {
334 warn $_[0]->data;
335 };
336 $w->data ("print me!");
337
338 $current_cb = $w->cb
339 $old_cb = $w->cb ($new_cb)
340 Queries the callback on the watcher and optionally changes it. You
341 can do this at any time without the watcher restarting.
342
343 $current_priority = $w->priority
344 $old_priority = $w->priority ($new_priority)
345 Queries the priority on the watcher and optionally changes it.
346 Pending watchers with higher priority will be invoked first. The
347 valid range of priorities lies between EV::MAXPRI (default 2) and
348 EV::MINPRI (default -2). If the priority is outside this range it
349 will automatically be normalised to the nearest valid priority.
350
351 The default priority of any newly-created watcher is 0.
352
353 Note that the priority semantics have not yet been fleshed out and
354 are subject to almost certain change.
355
356 $w->invoke ($revents)
357 Call the callback *now* with the given event mask.
358
359 $w->feed_event ($revents)
360 Feed some events on this watcher into EV. EV will react to this call
361 as if the watcher had received the given $revents mask.
362
363 $revents = $w->clear_pending
364 If the watcher is pending, this function clears its pending status
365 and returns its $revents bitset (as if its callback was invoked). If
366 the watcher isn't pending it does nothing and returns 0.
367
368 $previous_state = $w->keepalive ($bool)
369 Normally, "EV::loop" will return when there are no active watchers
370 (which is a "deadlock" because no progress can be made anymore).
371 This is convenient because it allows you to start your watchers (and
372 your jobs), call "EV::loop" once and when it returns you know that
373 all your jobs are finished (or they forgot to register some watchers
374 for their task :).
375
376 Sometimes, however, this gets in your way, for example when the
377 module that calls "EV::loop" (usually the main program) is not the
378 same module as a long-living watcher (for example a DNS client
379 module written by somebody else even). Then you might want any
380 outstanding requests to be handled, but you would not want to keep
381 "EV::loop" from returning just because you happen to have this
382 long-running UDP port watcher.
383
384 In this case you can clear the keepalive status, which means that
385 even though your watcher is active, it won't keep "EV::loop" from
386 returning.
387
388 The initial value for keepalive is true (enabled), and you can
389 change it any time.
390
391 Example: Register an I/O watcher for some UDP socket but do not keep
392 the event loop from running just because of that watcher.
393
394 my $udp_socket = ...
395 my $udp_watcher = EV::io $udp_socket, EV::READ, sub { ... };
396 $udp_watcher->keepalive (0);
397
398 $loop = $w->loop
399 Return the loop that this watcher is attached to.
400
401WATCHER TYPES
402 Each of the following subsections describes a single watcher type.
403
404 I/O WATCHERS - is this file descriptor readable or writable?
101 my $w = EV::io $fileno_or_fh, $eventmask, $callback 405 $w = EV::io $fileno_or_fh, $eventmask, $callback
102 my $w = EV::io_ns $fileno_or_fh, $eventmask, $callback 406 $w = EV::io_ns $fileno_or_fh, $eventmask, $callback
407 $w = $loop->io ($fileno_or_fh, $eventmask, $callback)
408 $w = $loop->io_ns ($fileno_or_fh, $eventmask, $callback)
103 As long as the returned watcher object is alive, call the $callback 409 As long as the returned watcher object is alive, call the $callback
104 when the events specified in $eventmask happen. Initially, the 410 when at least one of events specified in $eventmask occurs.
105 timeout is disabled.
106 411
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: 412 The $eventmask can be one or more of these constants ORed together:
116 413
117 EV::READ wait until read() wouldn't block anymore 414 EV::READ wait until read() wouldn't block anymore
118 EV::WRITE wait until write() wouldn't block anymore 415 EV::WRITE wait until write() wouldn't block anymore
119 EV::PERSIST stay active after a (non-timeout) event occured
120 416
121 The "io_ns" variant doesn't add/start the newly created watcher. 417 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. 418 watcher.
173 419
174 my $w = EV::signal $signal, $callback 420 $w->set ($fileno_or_fh, $eventmask)
175 my $w = EV::signal_ns $signal, $callback 421 Reconfigures the watcher, see the constructor above for details. Can
176 Call the callback when $signal is received (the signal can be 422 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.
210 423
211 $current_fh = $w->fh 424 $current_fh = $w->fh
212 $old_fh = $w->fh ($new_fh) 425 $old_fh = $w->fh ($new_fh)
213 Returns the previously set filehandle and optionally set a new one 426 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).
220 427
221 $current_eventmask = $w->events 428 $current_eventmask = $w->events
222 $old_eventmask = $w->events ($new_eventmask) 429 $old_eventmask = $w->events ($new_eventmask)
223 Returns the previously set event mask and optionally set a new one. 430 Returns the previously set event mask and optionally set a new one.
224 431
432 TIMER WATCHERS - relative and optionally repeating timeouts
433 $w = EV::timer $after, $repeat, $callback
434 $w = EV::timer_ns $after, $repeat, $callback
435 $w = $loop->timer ($after, $repeat, $callback)
436 $w = $loop->timer_ns ($after, $repeat, $callback)
437 Calls the callback after $after seconds (which may be fractional).
438 If $repeat is non-zero, the timer will be restarted (with the
439 $repeat value as $after) after the callback returns.
440
441 This means that the callback would be called roughly after $after
442 seconds, and then every $repeat seconds. The timer does his best not
443 to drift, but it will not invoke the timer more often then once per
444 event loop iteration, and might drift in other cases. If that isn't
445 acceptable, look at EV::periodic, which can provide long-term stable
446 timers.
447
448 The timer is based on a monotonic clock, that is, if somebody is
449 sitting in front of the machine while the timer is running and
450 changes the system clock, the timer will nevertheless run (roughly)
451 the same time.
452
453 The "timer_ns" variant doesn't start (activate) the newly created
454 watcher.
455
225 $w->timeout ($after, $repeat) 456 $w->set ($after, $repeat)
226 Resets the timeout (see "EV::timer" for details). 457 Reconfigures the watcher, see the constructor above for details. Can
458 be called at any time.
227 459
460 $w->again
461 Similar to the "start" method, but has special semantics for
462 repeating timers:
463
464 If the timer is active and non-repeating, it will be stopped.
465
466 If the timer is active and repeating, reset the timeout to occur
467 $repeat seconds after now.
468
469 If the timer is inactive and repeating, start it using the repeat
470 value.
471
472 Otherwise do nothing.
473
474 This behaviour is useful when you have a timeout for some IO
475 operation. You create a timer object with the same value for $after
476 and $repeat, and then, in the read/write watcher, run the "again"
477 method on the timeout.
478
479 PERIODIC WATCHERS - to cron or not to cron?
480 $w = EV::periodic $at, $interval, $reschedule_cb, $callback
481 $w = EV::periodic_ns $at, $interval, $reschedule_cb, $callback
482 $w = $loop->periodic ($at, $interval, $reschedule_cb, $callback)
483 $w = $loop->periodic_ns ($at, $interval, $reschedule_cb, $callback)
484 Similar to EV::timer, but is not based on relative timeouts but on
485 absolute times. Apart from creating "simple" timers that trigger
486 "at" the specified time, it can also be used for non-drifting
487 absolute timers and more complex, cron-like, setups that are not
488 adversely affected by time jumps (i.e. when the system clock is
489 changed by explicit date -s or other means such as ntpd). It is also
490 the most complex watcher type in EV.
491
492 It has three distinct "modes":
493
494 * absolute timer ($interval = $reschedule_cb = 0)
495
496 This time simply fires at the wallclock time $at and doesn't
497 repeat. It will not adjust when a time jump occurs, that is, if
498 it is to be run at January 1st 2011 then it will run when the
499 system time reaches or surpasses this time.
500
501 * repeating interval timer ($interval > 0, $reschedule_cb = 0)
502
503 In this mode the watcher will always be scheduled to time out at
504 the next "$at + N * $interval" time (for some integer N) and
505 then repeat, regardless of any time jumps.
506
507 This can be used to create timers that do not drift with respect
508 to system time:
509
510 my $hourly = EV::periodic 0, 3600, 0, sub { print "once/hour\n" };
511
512 That doesn't mean there will always be 3600 seconds in between
513 triggers, but only that the the clalback will be called when the
514 system time shows a full hour (UTC).
515
516 Another way to think about it (for the mathematically inclined)
517 is that EV::periodic will try to run the callback in this mode
518 at the next possible time where "$time = $at (mod $interval)",
519 regardless of any time jumps.
520
521 * manual reschedule mode ($reschedule_cb = coderef)
522
523 In this mode $interval and $at are both being ignored. Instead,
524 each time the periodic watcher gets scheduled, the reschedule
525 callback ($reschedule_cb) will be called with the watcher as
526 first, and the current time as second argument.
527
528 *This callback MUST NOT stop or destroy this or any other
529 periodic watcher, ever, and MUST NOT call any event loop
530 functions or methods*. If you need to stop it, return 1e30 and
531 stop it afterwards. You may create and start a "EV::prepare"
532 watcher for this task.
533
534 It must return the next time to trigger, based on the passed
535 time value (that is, the lowest time value larger than or equal
536 to to the second argument). It will usually be called just
537 before the callback will be triggered, but might be called at
538 other times, too.
539
540 This can be used to create very complex timers, such as a timer
541 that triggers on each midnight, local time (actually 24 hours
542 after the last midnight, to keep the example simple. If you know
543 a way to do it correctly in about the same space (without
544 requiring elaborate modules), drop me a note :):
545
546 my $daily = EV::periodic 0, 0, sub {
547 my ($w, $now) = @_;
548
549 use Time::Local ();
550 my (undef, undef, undef, $d, $m, $y) = localtime $now;
551 86400 + Time::Local::timelocal 0, 0, 0, $d, $m, $y
552 }, sub {
553 print "it's midnight or likely shortly after, now\n";
554 };
555
556 The "periodic_ns" variant doesn't start (activate) the newly created
557 watcher.
558
559 $w->set ($at, $interval, $reschedule_cb)
560 Reconfigures the watcher, see the constructor above for details. Can
561 be called at any time.
562
563 $w->again
564 Simply stops and starts the watcher again.
565
566 $time = $w->at
567 Return the time that the watcher is expected to trigger next.
568
569 SIGNAL WATCHERS - signal me when a signal gets signalled!
570 $w = EV::signal $signal, $callback
571 $w = EV::signal_ns $signal, $callback
572 $w = $loop->signal ($signal, $callback)
573 $w = $loop->signal_ns ($signal, $callback)
574 Call the callback when $signal is received (the signal can be
575 specified by number or by name, just as with "kill" or %SIG).
576
577 Only one event loop can grab a given signal - attempting to grab the
578 same signal from two EV loops will crash the program immediately or
579 cause data corruption.
580
581 EV will grab the signal for the process (the kernel only allows one
582 component to receive a signal at a time) when you start a signal
583 watcher, and removes it again when you stop it. Perl does the same
584 when you add/remove callbacks to %SIG, so watch out.
585
586 You can have as many signal watchers per signal as you want.
587
588 The "signal_ns" variant doesn't start (activate) the newly created
589 watcher.
590
591 $w->set ($signal)
592 Reconfigures the watcher, see the constructor above for details. Can
593 be called at any time.
594
595 $current_signum = $w->signal
596 $old_signum = $w->signal ($new_signal)
597 Returns the previously set signal (always as a number not name) and
598 optionally set a new one.
599
600 CHILD WATCHERS - watch out for process status changes
601 $w = EV::child $pid, $trace, $callback
602 $w = EV::child_ns $pid, $trace, $callback
603 $w = $loop->child ($pid, $trace, $callback)
604 $w = $loop->child_ns ($pid, $trace, $callback)
605 Call the callback when a status change for pid $pid (or any pid if
606 $pid is 0) has been received (a status change happens when the
607 process terminates or is killed, or, when trace is true,
608 additionally when it is stopped or continued). More precisely: when
609 the process receives a "SIGCHLD", EV will fetch the outstanding
610 exit/wait status for all changed/zombie children and call the
611 callback.
612
613 It is valid (and fully supported) to install a child watcher after a
614 child has exited but before the event loop has started its next
615 iteration (for example, first you "fork", then the new child process
616 might exit, and only then do you install a child watcher in the
617 parent for the new pid).
618
619 You can access both exit (or tracing) status and pid by using the
620 "rstatus" and "rpid" methods on the watcher object.
621
622 You can have as many pid watchers per pid as you want, they will all
623 be called.
624
625 The "child_ns" variant doesn't start (activate) the newly created
626 watcher.
627
628 $w->set ($pid, $trace)
629 Reconfigures the watcher, see the constructor above for details. Can
630 be called at any time.
631
632 $current_pid = $w->pid
633 Returns the previously set process id and optionally set a new one.
634
635 $exit_status = $w->rstatus
636 Return the exit/wait status (as returned by waitpid, see the waitpid
637 entry in perlfunc).
638
639 $pid = $w->rpid
640 Return the pid of the awaited child (useful when you have installed
641 a watcher for all pids).
642
643 STAT WATCHERS - did the file attributes just change?
644 $w = EV::stat $path, $interval, $callback
645 $w = EV::stat_ns $path, $interval, $callback
646 $w = $loop->stat ($path, $interval, $callback)
647 $w = $loop->stat_ns ($path, $interval, $callback)
648 Call the callback when a file status change has been detected on
649 $path. The $path does not need to exist, changing from "path exists"
650 to "path does not exist" is a status change like any other.
651
652 The $interval is a recommended polling interval for systems where
653 OS-supported change notifications don't exist or are not supported.
654 If you use 0 then an unspecified default is used (which is highly
655 recommended!), which is to be expected to be around five seconds
656 usually.
657
658 This watcher type is not meant for massive numbers of stat watchers,
659 as even with OS-supported change notifications, this can be
660 resource-intensive.
661
662 The "stat_ns" variant doesn't start (activate) the newly created
663 watcher.
664
665 ... = $w->stat
666 This call is very similar to the perl "stat" built-in: It stats
667 (using "lstat") the path specified in the watcher and sets perls
668 stat cache (as well as EV's idea of the current stat values) to the
669 values found.
670
671 In scalar context, a boolean is return indicating success or failure
672 of the stat. In list context, the same 13-value list as with stat is
673 returned (except that the blksize and blocks fields are not
674 reliable).
675
676 In the case of an error, errno is set to "ENOENT" (regardless of the
677 actual error value) and the "nlink" value is forced to zero (if the
678 stat was successful then nlink is guaranteed to be non-zero).
679
680 See also the next two entries for more info.
681
682 ... = $w->attr
683 Just like "$w->stat", but without the initial stat'ing: this returns
684 the values most recently detected by EV. See the next entry for more
685 info.
686
687 ... = $w->prev
688 Just like "$w->stat", but without the initial stat'ing: this returns
689 the previous set of values, before the change.
690
691 That is, when the watcher callback is invoked, "$w->prev" will be
692 set to the values found *before* a change was detected, while
693 "$w->attr" returns the values found leading to the change detection.
694 The difference (if any) between "prev" and "attr" is what triggered
695 the callback.
696
697 If you did something to the filesystem object and do not want to
698 trigger yet another change, you can call "stat" to update EV's idea
699 of what the current attributes are.
700
228 $w->timeout_abs ($at, $interval) 701 $w->set ($path, $interval)
229 Resets the timeout (see "EV::timer_abs" for details). 702 Reconfigures the watcher, see the constructor above for details. Can
703 be called at any time.
230 704
231 $w->priority_set ($priority) 705 $current_path = $w->path
232 Set the priority of the watcher to $priority (0 <= $priority < 706 $old_path = $w->path ($new_path)
233 $EV::NPRI). 707 Returns the previously set path and optionally set a new one.
234 708
235BUGS 709 $current_interval = $w->interval
236 Lots. Libevent itself isn't well tested and rather buggy, and this 710 $old_interval = $w->interval ($new_interval)
237 module is quite new at the moment. 711 Returns the previously set interval and optionally set a new one.
712 Can be used to query the actual interval used.
238 713
239 Please note that the epoll method is not, in general, reliable in 714 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 715 $w = EV::idle $callback
241 forked process). If your program behaves erratically, try setting the 716 $w = EV::idle_ns $callback
242 environment variable "EVENT_NOEPOLL" first when running the program. 717 $w = $loop->idle ($callback)
718 $w = $loop->idle_ns ($callback)
719 Call the callback when there are no other pending watchers of the
720 same or higher priority (excluding check, prepare and other idle
721 watchers of the same or lower priority, of course). They are called
722 idle watchers because when the watcher is the highest priority
723 pending event in the process, the process is considered to be idle
724 at that priority.
243 725
244 In general, if you fork, then you can only use the EV module in one of 726 If you want a watcher that is only ever called when *no* other
245 the children. 727 events are outstanding you have to set the priority to "EV::MINPRI".
728
729 The process will not block as long as any idle watchers are active,
730 and they will be called repeatedly until stopped.
731
732 For example, if you have idle watchers at priority 0 and 1, and an
733 I/O watcher at priority 0, then the idle watcher at priority 1 and
734 the I/O watcher will always run when ready. Only when the idle
735 watcher at priority 1 is stopped and the I/O watcher at priority 0
736 is not pending with the 0-priority idle watcher be invoked.
737
738 The "idle_ns" variant doesn't start (activate) the newly created
739 watcher.
740
741 PREPARE WATCHERS - customise your event loop!
742 $w = EV::prepare $callback
743 $w = EV::prepare_ns $callback
744 $w = $loop->prepare ($callback)
745 $w = $loop->prepare_ns ($callback)
746 Call the callback just before the process would block. You can still
747 create/modify any watchers at this point.
748
749 See the EV::check watcher, below, for explanations and an example.
750
751 The "prepare_ns" variant doesn't start (activate) the newly created
752 watcher.
753
754 CHECK WATCHERS - customise your event loop even more!
755 $w = EV::check $callback
756 $w = EV::check_ns $callback
757 $w = $loop->check ($callback)
758 $w = $loop->check_ns ($callback)
759 Call the callback just after the process wakes up again (after it
760 has gathered events), but before any other callbacks have been
761 invoked.
762
763 This is used to integrate other event-based software into the EV
764 mainloop: You register a prepare callback and in there, you create
765 io and timer watchers as required by the other software. Here is a
766 real-world example of integrating Net::SNMP (with some details left
767 out):
768
769 our @snmp_watcher;
770
771 our $snmp_prepare = EV::prepare sub {
772 # do nothing unless active
773 $dispatcher->{_event_queue_h}
774 or return;
775
776 # make the dispatcher handle any outstanding stuff
777 ... not shown
778
779 # create an I/O watcher for each and every socket
780 @snmp_watcher = (
781 (map { EV::io $_, EV::READ, sub { } }
782 keys %{ $dispatcher->{_descriptors} }),
783
784 EV::timer +($event->[Net::SNMP::Dispatcher::_ACTIVE]
785 ? $event->[Net::SNMP::Dispatcher::_TIME] - EV::now : 0),
786 0, sub { },
787 );
788 };
789
790 The callbacks are irrelevant (and are not even being called), the
791 only purpose of those watchers is to wake up the process as soon as
792 one of those events occurs (socket readable, or timer timed out).
793 The corresponding EV::check watcher will then clean up:
794
795 our $snmp_check = EV::check sub {
796 # destroy all watchers
797 @snmp_watcher = ();
798
799 # make the dispatcher handle any new stuff
800 ... not shown
801 };
802
803 The callbacks of the created watchers will not be called as the
804 watchers are destroyed before this can happen (remember EV::check
805 gets called first).
806
807 The "check_ns" variant doesn't start (activate) the newly created
808 watcher.
809
810 FORK WATCHERS - the audacity to resume the event loop after a fork
811 Fork watchers are called when a "fork ()" was detected. The invocation
812 is done before the event loop blocks next and before "check" watchers
813 are being called, and only in the child after the fork.
814
815 $w = EV::fork $callback
816 $w = EV::fork_ns $callback
817 $w = $loop->fork ($callback)
818 $w = $loop->fork_ns ($callback)
819 Call the callback before the event loop is resumed in the child
820 process after a fork.
821
822 The "fork_ns" variant doesn't start (activate) the newly created
823 watcher.
824
825 EMBED WATCHERS - when one backend isn't enough...
826 This is a rather advanced watcher type that lets you embed one event
827 loop into another (currently only IO events are supported in the
828 embedded loop, other types of watchers might be handled in a delayed or
829 incorrect fashion and must not be used).
830
831 See the libev documentation at
832 <http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod#code_ev_embed_code
833 _when_one_backend_> (locally installed as EV::libev) for more details.
834
835 In short, this watcher is most useful on BSD systems without working
836 kqueue to still be able to handle a large number of sockets:
837
838 my $socket_loop;
839
840 # check wether we use SELECT or POLL _and_ KQUEUE is supported
841 if (
842 (EV::backend & (EV::BACKEND_POLL | EV::BACKEND_SELECT))
843 && (EV::supported_backends & EV::embeddable_backends & EV::BACKEND_KQUEUE)
844 ) {
845 # use kqueue for sockets
846 $socket_loop = new EV::Loop EV::BACKEND_KQUEUE | EV::FLAG_NOENV;
847 }
848
849 # use the default loop otherwise
850 $socket_loop ||= EV::default_loop;
851
852 $w = EV::embed $otherloop[, $callback]
853 $w = EV::embed_ns $otherloop[, $callback]
854 $w = $loop->embed ($otherloop[, $callback])
855 $w = $loop->embed_ns ($otherloop[, $callback])
856 Call the callback when the embedded event loop ($otherloop) has any
857 I/O activity. The $callback is optional: if it is missing, then the
858 embedded event loop will be managed automatically (which is
859 recommended), otherwise you have to invoke "sweep" yourself.
860
861 The "embed_ns" variant doesn't start (activate) the newly created
862 watcher.
863
864 ASYNC WATCHERS - how to wake up another event loop
865 Async watchers are provided by EV, but have little use in perl directly,
866 as perl neither supports threads running in parallel nor direct access
867 to signal handlers or other contexts where they could be of value.
868
869 It is, however, possible to use them from the XS level.
870
871 Please see the libev documentation for further details.
872
873 $w = EV::async $callback
874 $w = EV::async_ns $callback
875 $w->send
876 $bool = $w->async_pending
877
878PERL SIGNALS
879 While Perl signal handling (%SIG) is not affected by EV, the behaviour
880 with EV is as the same as any other C library: Perl-signals will only be
881 handled when Perl runs, which means your signal handler might be invoked
882 only the next time an event callback is invoked.
883
884 The solution is to use EV signal watchers (see "EV::signal"), which will
885 ensure proper operations with regards to other event watchers.
886
887 If you cannot do this for whatever reason, you can also force a watcher
888 to be called on every event loop iteration by installing a "EV::check"
889 watcher:
890
891 my $async_check = EV::check sub { };
892
893 This ensures that perl gets into control for a short time to handle any
894 pending signals, and also ensures (slightly) slower overall operation.
895
896ITHREADS
897 Ithreads are not supported by this module in any way. Perl
898 pseudo-threads is evil stuff and must die. Real threads as provided by
899 Coro are fully supported (and enhanced support is available via
900 Coro::EV).
901
902FORK
903 Most of the "improved" event delivering mechanisms of modern operating
904 systems have quite a few problems with fork(2) (to put it bluntly: it is
905 not supported and usually destructive). Libev makes it possible to work
906 around this by having a function that recreates the kernel state after
907 fork in the child.
908
909 On non-win32 platforms, this module requires the pthread_atfork
910 functionality to do this automatically for you. This function is quite
911 buggy on most BSDs, though, so YMMV. The overhead for this is quite
912 negligible, because everything the function currently does is set a flag
913 that is checked only when the event loop gets used the next time, so
914 when you do fork but not use EV, the overhead is minimal.
915
916 On win32, there is no notion of fork so all this doesn't apply, of
917 course.
246 918
247SEE ALSO 919SEE ALSO
248 L<EV::DNS>, L<event(3)>, L<event.h>, L<evdns.h>. 920 EV::ADNS (asynchronous DNS), Glib::EV (makes Glib/Gtk2 use EV as event
249 L<EV::AnyEvent>. 921 loop), EV::Glib (embed Glib into EV), Coro::EV (efficient coroutines
922 with EV), Net::SNMP::EV (asynchronous SNMP), AnyEvent for event-loop
923 agnostic and portable event driven programming.
250 924
251AUTHOR 925AUTHOR
252 Marc Lehmann <schmorp@schmorp.de> 926 Marc Lehmann <schmorp@schmorp.de>
253 http://home.schmorp.de/ 927 http://home.schmorp.de/
254 928

Diff Legend

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