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 1.22 by root, Mon Jan 28 12:24:05 2008 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;
6 7
7 # TIMER 8 # TIMERS
8 9
9 my $w = EV::timer 2, 0, sub { 10 my $w = EV::timer 2, 0, sub {
10 warn "is called after 2s"; 11 warn "is called after 2s";
11 }; 12 };
12 13
13 my $w = EV::timer 2, 1, sub { 14 my $w = EV::timer 2, 2, sub {
14 warn "is called roughly every 2s (repeat = 1)"; 15 warn "is called roughly every 2s (repeat = 2)";
15 }; 16 };
16 17
17 undef $w; # destroy event watcher again 18 undef $w; # destroy event watcher again
18 19
19 my $w = EV::timer_abs 0, 60, sub { 20 my $w = EV::periodic 0, 60, 0, sub {
20 warn "is called every minute, on the minute, exactly"; 21 warn "is called every minute, on the minute, exactly";
21 }; 22 };
22
23 # IO 23
24 24 # IO
25
25 my $w = EV::io \*STDIN, EV::READ | EV::PERSIST, sub { 26 my $w = EV::io *STDIN, EV::READ, sub {
26 my ($w, $events) = @_; # all callbacks get the watcher object and event mask 27 my ($w, $revents) = @_; # all callbacks receive the watcher and event mask
27 if ($events & EV::TIMEOUT) {
28 warn "nothing received on stdin for 10 seconds, retrying";
29 } else {
30 warn "stdin is readable, you entered: ", <STDIN>; 28 warn "stdin is readable, you entered: ", <STDIN>;
31 }
32 }; 29 };
33 $w->timeout (10);
34
35 my $w = EV::timed_io \*STDIN, EV::READ, 30, sub {
36 my ($w, $events) = @_;
37 if ($_[1] & EV::TIMEOUT) {
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 }; 30
45
46 # SIGNALS 31 # SIGNALS
47 32
48 my $w = EV::signal 'QUIT', sub { 33 my $w = EV::signal 'QUIT', sub {
49 warn "sigquit received\n"; 34 warn "sigquit received\n";
50 }; 35 };
51 36
37 # CHILD/PID STATUS CHANGES
38
52 my $w = EV::signal 3, sub { 39 my $w = EV::child 666, 0, sub {
53 warn "sigquit received (this is GNU/Linux, right?)\n"; 40 my ($w, $revents) = @_;
41 my $status = $w->rstatus;
54 }; 42 };
55 43
44 # STAT CHANGES
45 my $w = EV::stat "/etc/passwd", 10, sub {
46 my ($w, $revents) = @_;
47 warn $w->path, " has changed somehow.\n";
48 };
49
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://cvs.schmorp.de/libev/ev.html>) for more subtle
60 details on watcher semantics or some discussion on the available
61 backends, or how to force a specific backend with "LIBEV_FLAGS", or just
62 about in any case because it has much more detailed information.
67 63
68 Please note thta this module disables the libevent EPOLL method by 64EVENT LOOPS
69 default, see BUGS, below, if you need to enable it. 65 EV supports multiple event loops: There is a single "default event loop"
66 that can handle everything including signals and child watchers, and any
67 number of "dynamic event loops" that can use different backends (with
68 various limitations), but no child and signal watchers.
69
70 You do not have to do anything to create the default event loop: When
71 the module is loaded a suitable backend is selected on the premise of
72 selecting a working backend (which for example rules out kqueue on most
73 BSDs). Modules should, unless they have "special needs" always use the
74 default loop as this is fastest (perl-wise), best supported by other
75 modules (e.g. AnyEvent or Coro) and most portable event loop.
76
77 For specific programs you can create additional event loops dynamically.
78
79 $loop = new EV::loop [$flags]
80 Create a new event loop as per the specified flags. Please refer to
81 the "ev_loop_new ()" function description in the libev documentation
82 (<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod#GLOBAL_FUNCTI
83 ONS>) for more info.
84
85 The loop will automatically be destroyed when it is no longer
86 referenced by any watcher and the loop object goes out of scope.
87
88 Using "EV::FLAG_FORKCHECK" is recommended, as only the default event
89 loop is protected by this module.
90
91 $loop->loop_fork
92 Must be called after a fork in the child, before entering or
93 continuing the event loop. An alternative is to use
94 "EV::FLAG_FORKCHECK" which calls this fucntion automatically, at
95 some performance loss (refer to the libev documentation).
96
97 $loop = EV::default_loop [$flags]
98 Return the default loop (which is a singleton object).
70 99
71BASIC INTERFACE 100BASIC INTERFACE
72 $EV::NPRI
73 How many priority levels are available.
74
75 $EV::DIED 101 $EV::DIED
76 Must contain a reference to a function that is called when a 102 Must contain a reference to a function that is called when a
77 callback throws an exception (with $@ containing thr error). The 103 callback throws an exception (with $@ containing the error). The
78 default prints an informative message and continues. 104 default prints an informative message and continues.
79 105
80 If this callback throws an exception it will be silently ignored. 106 If this callback throws an exception it will be silently ignored.
81 107
108 $flags = EV::supported_backends
109 $flags = EV::recommended_backends
110 $flags = EV::embeddable_backends
111 Returns the set (see "EV::BACKEND_*" flags) of backends supported by
112 this instance of EV, the set of recommended backends (supposed to be
113 good) for this platform and the set of embeddable backends (see
114 EMBED WATCHERS).
115
116 EV::sleep $seconds
117 Block the process for the given number of (fractional) seconds.
118
119 $time = EV::time
120 Returns the current time in (fractional) seconds since the epoch.
121
82 $time = EV::now 122 $time = EV::now
83 Returns the time in (fractional) seconds since the epoch. 123 $time = $loop->now
124 Returns the time the last event loop iteration has been started.
125 This is the time that (relative) timers are based on, and refering
126 to it is usually faster then calling EV::time.
84 127
85 $version = EV::version 128 $backend = EV::backend
86 $method = EV::method 129 $backend = $loop->backend
87 Return version string and event polling method used. 130 Returns an integer describing the backend used by libev
131 (EV::METHOD_SELECT or EV::METHOD_EPOLL).
88 132
89 EV::loop $flags # EV::LOOP_ONCE, EV::LOOP_ONESHOT 133 EV::loop [$flags]
90 EV::loopexit $after 134 $loop->loop ([$flags])
91 Exit any active loop or dispatch after $after seconds or immediately 135 Begin checking for events and calling callbacks. It returns when a
92 if $after is missing or zero. 136 callback calls EV::unloop.
93 137
94 EV::dispatch 138 The $flags argument can be one of the following:
95 Same as "EV::loop 0".
96 139
97 EV::event $callback 140 0 as above
98 Creates a new event watcher waiting for nothing, calling the given 141 EV::LOOP_ONESHOT block at most once (wait, but do not loop)
99 callback. 142 EV::LOOP_NONBLOCK do not block at all (fetch/handle events but do not wait)
100 143
144 EV::unloop [$how]
145 $loop->unloop ([$how])
146 When called with no arguments or an argument of EV::UNLOOP_ONE,
147 makes the innermost call to EV::loop return.
148
149 When called with an argument of EV::UNLOOP_ALL, all calls to
150 EV::loop will return as fast as possible.
151
152 $count = EV::loop_count
153 $count = $loop->loop_count
154 Return the number of times the event loop has polled for new events.
155 Sometiems useful as a generation counter.
156
157 EV::once $fh_or_undef, $events, $timeout, $cb->($revents)
158 $loop->once ($fh_or_undef, $events, $timeout, $cb->($revents))
159 This function rolls together an I/O and a timer watcher for a single
160 one-shot event without the need for managing a watcher object.
161
162 If $fh_or_undef is a filehandle or file descriptor, then $events
163 must be a bitset containing either "EV::READ", "EV::WRITE" or
164 "EV::READ | EV::WRITE", indicating the type of I/O event you want to
165 wait for. If you do not want to wait for some I/O event, specify
166 "undef" for $fh_or_undef and 0 for $events).
167
168 If timeout is "undef" or negative, then there will be no timeout.
169 Otherwise a EV::timer with this value will be started.
170
171 When an error occurs or either the timeout or I/O watcher triggers,
172 then the callback will be called with the received event set (in
173 general you can expect it to be a combination of "EV::ERROR",
174 "EV::READ", "EV::WRITE" and "EV::TIMEOUT").
175
176 EV::once doesn't return anything: the watchers stay active till
177 either of them triggers, then they will be stopped and freed, and
178 the callback invoked.
179
180 EV::feed_fd_event ($fd, $revents)
181 $loop->feed_fd_event ($fd, $revents)
182 Feed an event on a file descriptor into EV. EV will react to this
183 call as if the readyness notifications specified by $revents (a
184 combination of "EV::READ" and "EV::WRITE") happened on the file
185 descriptor $fd.
186
187 EV::feed_signal_event ($signal)
188 Feed a signal event into EV. EV will react to this call as if the
189 signal specified by $signal had occured.
190
191 EV::set_io_collect_interval $time
192 $loop->set_io_collect_interval ($time)
193 EV::set_timeout_collect_interval $time
194 $loop->set_timeout_collect_interval ($time)
195 These advanced functions set the minimum block interval when polling
196 for I/O events and the minimum wait interval for timer events. See
197 the libev documentation at
198 <http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod#FUNCTIONS_CONT
199 ROLLING_THE_EVENT_LOOP> for a more detailed discussion.
200
201WATCHER OBJECTS
202 A watcher is an object that gets created to record your interest in some
203 event. For instance, if you want to wait for STDIN to become readable,
204 you would create an EV::io watcher for that:
205
206 my $watcher = EV::io *STDIN, EV::READ, sub {
207 my ($watcher, $revents) = @_;
208 warn "yeah, STDIN should now be readable without blocking!\n"
209 };
210
211 All watchers can be active (waiting for events) or inactive (paused).
212 Only active watchers will have their callbacks invoked. All callbacks
213 will be called with at least two arguments: the watcher and a bitmask of
214 received events.
215
216 Each watcher type has its associated bit in revents, so you can use the
217 same callback for multiple watchers. The event mask is named after the
218 type, i..e. EV::child sets EV::CHILD, EV::prepare sets EV::PREPARE,
219 EV::periodic sets EV::PERIODIC and so on, with the exception of I/O
220 events (which can set both EV::READ and EV::WRITE bits), and EV::timer
221 (which uses EV::TIMEOUT).
222
223 In the rare case where one wants to create a watcher but not start it at
224 the same time, each constructor has a variant with a trailing "_ns" in
225 its name, e.g. EV::io has a non-starting variant EV::io_ns and so on.
226
227 Please note that a watcher will automatically be stopped when the
228 watcher object is destroyed, so you *need* to keep the watcher objects
229 returned by the constructors.
230
231 Also, all methods changing some aspect of a watcher (->set, ->priority,
232 ->fh and so on) automatically stop and start it again if it is active,
233 which means pending events get lost.
234
235 COMMON WATCHER METHODS
236 This section lists methods common to all watchers.
237
238 $w->start
239 Starts a watcher if it isn't active already. Does nothing to an
240 already active watcher. By default, all watchers start out in the
241 active state (see the description of the "_ns" variants if you need
242 stopped watchers).
243
244 $w->stop
245 Stop a watcher if it is active. Also clear any pending events
246 (events that have been received but that didn't yet result in a
247 callback invocation), regardless of whether the watcher was active
248 or not.
249
250 $bool = $w->is_active
251 Returns true if the watcher is active, false otherwise.
252
253 $current_data = $w->data
254 $old_data = $w->data ($new_data)
255 Queries a freely usable data scalar on the watcher and optionally
256 changes it. This is a way to associate custom data with a watcher:
257
258 my $w = EV::timer 60, 0, sub {
259 warn $_[0]->data;
260 };
261 $w->data ("print me!");
262
263 $current_cb = $w->cb
264 $old_cb = $w->cb ($new_cb)
265 Queries the callback on the watcher and optionally changes it. You
266 can do this at any time without the watcher restarting.
267
268 $current_priority = $w->priority
269 $old_priority = $w->priority ($new_priority)
270 Queries the priority on the watcher and optionally changes it.
271 Pending watchers with higher priority will be invoked first. The
272 valid range of priorities lies between EV::MAXPRI (default 2) and
273 EV::MINPRI (default -2). If the priority is outside this range it
274 will automatically be normalised to the nearest valid priority.
275
276 The default priority of any newly-created watcher is 0.
277
278 Note that the priority semantics have not yet been fleshed out and
279 are subject to almost certain change.
280
281 $w->invoke ($revents)
282 Call the callback *now* with the given event mask.
283
284 $w->feed_event ($revents)
285 Feed some events on this watcher into EV. EV will react to this call
286 as if the watcher had received the given $revents mask.
287
288 $revents = $w->clear_pending
289 If the watcher is pending, this function clears its pending status
290 and returns its $revents bitset (as if its callback was invoked). If
291 the watcher isn't pending it does nothing and returns 0.
292
293 $previous_state = $w->keepalive ($bool)
294 Normally, "EV::loop" will return when there are no active watchers
295 (which is a "deadlock" because no progress can be made anymore).
296 This is convinient because it allows you to start your watchers (and
297 your jobs), call "EV::loop" once and when it returns you know that
298 all your jobs are finished (or they forgot to register some watchers
299 for their task :).
300
301 Sometimes, however, this gets in your way, for example when the
302 module that calls "EV::loop" (usually the main program) is not the
303 same module as a long-living watcher (for example a DNS client
304 module written by somebody else even). Then you might want any
305 outstanding requests to be handled, but you would not want to keep
306 "EV::loop" from returning just because you happen to have this
307 long-running UDP port watcher.
308
309 In this case you can clear the keepalive status, which means that
310 even though your watcher is active, it won't keep "EV::loop" from
311 returning.
312
313 The initial value for keepalive is true (enabled), and you cna
314 change it any time.
315
316 Example: Register an I/O watcher for some UDP socket but do not keep
317 the event loop from running just because of that watcher.
318
319 my $udp_socket = ...
320 my $udp_watcher = EV::io $udp_socket, EV::READ, sub { ... };
321 $1000udp_watcher->keepalive (0);
322
323 $loop = $w->loop
324 Return the loop that this watcher is attached to.
325
326WATCHER TYPES
327 Each of the following subsections describes a single watcher type.
328
329 I/O WATCHERS - is this file descriptor readable or writable?
101 my $w = EV::io $fileno_or_fh, $eventmask, $callback 330 $w = EV::io $fileno_or_fh, $eventmask, $callback
102 my $w = EV::io_ns $fileno_or_fh, $eventmask, $callback 331 $w = EV::io_ns $fileno_or_fh, $eventmask, $callback
332 $w = $loop->io ($fileno_or_fh, $eventmask, $callback)
333 $w = $loop->io_ns ($fileno_or_fh, $eventmask, $callback)
103 As long as the returned watcher object is alive, call the $callback 334 As long as the returned watcher object is alive, call the $callback
104 when the events specified in $eventmask happen. Initially, the 335 when at least one of events specified in $eventmask occurs.
105 timeout is disabled.
106 336
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: 337 The $eventmask can be one or more of these constants ORed together:
116 338
117 EV::READ wait until read() wouldn't block anymore 339 EV::READ wait until read() wouldn't block anymore
118 EV::WRITE wait until write() wouldn't block anymore 340 EV::WRITE wait until write() wouldn't block anymore
119 EV::PERSIST stay active after a (non-timeout) event occured
120 341
121 The "io_ns" variant doesn't add/start the newly created watcher. 342 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. 343 watcher.
173 344
174 my $w = EV::signal $signal, $callback 345 $w->set ($fileno_or_fh, $eventmask)
175 my $w = EV::signal_ns $signal, $callback 346 Reconfigures the watcher, see the constructor above for details. Can
176 Call the callback when $signal is received (the signal can be 347 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.
210 348
211 $current_fh = $w->fh 349 $current_fh = $w->fh
212 $old_fh = $w->fh ($new_fh) 350 $old_fh = $w->fh ($new_fh)
213 Returns the previously set filehandle and optionally set a new one 351 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).
220 352
221 $current_eventmask = $w->events 353 $current_eventmask = $w->events
222 $old_eventmask = $w->events ($new_eventmask) 354 $old_eventmask = $w->events ($new_eventmask)
223 Returns the previously set event mask and optionally set a new one. 355 Returns the previously set event mask and optionally set a new one.
224 356
357 TIMER WATCHERS - relative and optionally repeating timeouts
358 $w = EV::timer $after, $repeat, $callback
359 $w = EV::timer_ns $after, $repeat, $callback
360 $w = $loop->timer ($after, $repeat, $callback)
361 $w = $loop->timer_ns ($after, $repeat, $callback)
362 Calls the callback after $after seconds (which may be fractional).
363 If $repeat is non-zero, the timer will be restarted (with the
364 $repeat value as $after) after the callback returns.
365
366 This means that the callback would be called roughly after $after
367 seconds, and then every $repeat seconds. The timer does his best not
368 to drift, but it will not invoke the timer more often then once per
369 event loop iteration, and might drift in other cases. If that isn't
370 acceptable, look at EV::periodic, which can provide long-term stable
371 timers.
372
373 The timer is based on a monotonic clock, that is, if somebody is
374 sitting in front of the machine while the timer is running and
375 changes the system clock, the timer will nevertheless run (roughly)
376 the same time.
377
378 The "timer_ns" variant doesn't start (activate) the newly created
379 watcher.
380
225 $w->timeout ($after, $repeat) 381 $w->set ($after, $repeat)
226 Resets the timeout (see "EV::timer" for details). 382 Reconfigures the watcher, see the constructor above for details. Can
383 be called at any time.
227 384
385 $w->again
386 Similar to the "start" method, but has special semantics for
387 repeating timers:
388
389 If the timer is active and non-repeating, it will be stopped.
390
391 If the timer is active and repeating, reset the timeout to occur
392 $repeat seconds after now.
393
394 If the timer is inactive and repeating, start it using the repeat
395 value.
396
397 Otherwise do nothing.
398
399 This behaviour is useful when you have a timeout for some IO
400 operation. You create a timer object with the same value for $after
401 and $repeat, and then, in the read/write watcher, run the "again"
402 method on the timeout.
403
404 PERIODIC WATCHERS - to cron or not to cron?
405 $w = EV::periodic $at, $interval, $reschedule_cb, $callback
406 $w = EV::periodic_ns $at, $interval, $reschedule_cb, $callback
407 $w = $loop->periodic ($at, $interval, $reschedule_cb, $callback)
408 $w = $loop->periodic_ns ($at, $interval, $reschedule_cb, $callback)
409 Similar to EV::timer, but is not based on relative timeouts but on
410 absolute times. Apart from creating "simple" timers that trigger
411 "at" the specified time, it can also be used for non-drifting
412 absolute timers and more complex, cron-like, setups that are not
413 adversely affected by time jumps (i.e. when the system clock is
414 changed by explicit date -s or other means such as ntpd). It is also
415 the most complex watcher type in EV.
416
417 It has three distinct "modes":
418
419 * absolute timer ($interval = $reschedule_cb = 0)
420
421 This time simply fires at the wallclock time $at and doesn't
422 repeat. It will not adjust when a time jump occurs, that is, if
423 it is to be run at January 1st 2011 then it will run when the
424 system time reaches or surpasses this time.
425
426 * non-repeating interval timer ($interval > 0, $reschedule_cb = 0)
427
428 In this mode the watcher will always be scheduled to time out at
429 the next "$at + N * $interval" time (for some integer N) and
430 then repeat, regardless of any time jumps.
431
432 This can be used to create timers that do not drift with respect
433 to system time:
434
435 my $hourly = EV::periodic 0, 3600, 0, sub { print "once/hour\n" };
436
437 That doesn't mean there will always be 3600 seconds in between
438 triggers, but only that the the clalback will be called when the
439 system time shows a full hour (UTC).
440
441 Another way to think about it (for the mathematically inclined)
442 is that EV::periodic will try to run the callback in this mode
443 at the next possible time where "$time = $at (mod $interval)",
444 regardless of any time jumps.
445
446 * manual reschedule mode ($reschedule_cb = coderef)
447
448 In this mode $interval and $at are both being ignored. Instead,
449 each time the periodic watcher gets scheduled, the reschedule
450 callback ($reschedule_cb) will be called with the watcher as
451 first, and the current time as second argument.
452
453 *This callback MUST NOT stop or destroy this or any other
454 periodic watcher, ever*. If you need to stop it, return 1e30 and
455 stop it afterwards.
456
457 It must return the next time to trigger, based on the passed
458 time value (that is, the lowest time value larger than to the
459 second argument). It will usually be called just before the
460 callback will be triggered, but might be called at other times,
461 too.
462
463 This can be used to create very complex timers, such as a timer
464 that triggers on each midnight, local time (actually 24 hours
465 after the last midnight, to keep the example simple. If you know
466 a way to do it correctly in about the same space (without
467 requiring elaborate modules), drop me a note :):
468
469 my $daily = EV::periodic 0, 0, sub {
470 my ($w, $now) = @_;
471
472 use Time::Local ();
473 my (undef, undef, undef, $d, $m, $y) = localtime $now;
474 86400 + Time::Local::timelocal 0, 0, 0, $d, $m, $y
475 }, sub {
476 print "it's midnight or likely shortly after, now\n";
477 };
478
479 The "periodic_ns" variant doesn't start (activate) the newly created
480 watcher.
481
482 $w->set ($at, $interval, $reschedule_cb)
483 Reconfigures the watcher, see the constructor above for details. Can
484 be called at any time.
485
486 $w->again
487 Simply stops and starts the watcher again.
488
489 $time = $w->at
490 Return the time that the watcher is expected to trigger next.
491
492 SIGNAL WATCHERS - signal me when a signal gets signalled!
493 $w = EV::signal $signal, $callback
494 $w = EV::signal_ns $signal, $callback
495 Call the callback when $signal is received (the signal can be
496 specified by number or by name, just as with "kill" or %SIG).
497
498 EV will grab the signal for the process (the kernel only allows one
499 component to receive a signal at a time) when you start a signal
500 watcher, and removes it again when you stop it. Perl does the same
501 when you add/remove callbacks to %SIG, so watch out.
502
503 You can have as many signal watchers per signal as you want.
504
505 The "signal_ns" variant doesn't start (activate) the newly created
506 watcher.
507
508 $w->set ($signal)
509 Reconfigures the watcher, see the constructor above for details. Can
510 be called at any time.
511
512 $current_signum = $w->signal
513 $old_signum = $w->signal ($new_signal)
514 Returns the previously set signal (always as a number not name) and
515 optionally set a new one.
516
517 CHILD WATCHERS - watch out for process status changes
518 $w = EV::child $pid, $trace, $callback
519 $w = EV::child_ns $pid, $trace, $callback
520 $w = $loop->child ($pid, $trace, $callback)
521 $w = $loop->child_ns ($pid, $trace, $callback)
522 Call the callback when a status change for pid $pid (or any pid if
523 $pid is 0) has been received (a status change happens when the
524 process terminates or is killed, or, when trace is true,
525 additionally when it is stopped or continued). More precisely: when
526 the process receives a "SIGCHLD", EV will fetch the outstanding
527 exit/wait status for all changed/zombie children and call the
528 callback.
529
530 It is valid (and fully supported) to install a child watcher after a
531 child has exited but before the event loop has started its next
532 iteration (for example, first you "fork", then the new child process
533 might exit, and only then do you install a child watcher in the
534 parent for the new pid).
535
536 You can access both exit (or tracing) status and pid by using the
537 "rstatus" and "rpid" methods on the watcher object.
538
539 You can have as many pid watchers per pid as you want, they will all
540 be called.
541
542 The "child_ns" variant doesn't start (activate) the newly created
543 watcher.
544
545 $w->set ($pid, $trace)
546 Reconfigures the watcher, see the constructor above for details. Can
547 be called at any time.
548
549 $current_pid = $w->pid
550 Returns the previously set process id and optionally set a new one.
551
552 $exit_status = $w->rstatus
553 Return the exit/wait status (as returned by waitpid, see the waitpid
554 entry in perlfunc).
555
556 $pid = $w->rpid
557 Return the pid of the awaited child (useful when you have installed
558 a watcher for all pids).
559
560 STAT WATCHERS - did the file attributes just change?
561 $w = EV::stat $path, $interval, $callback
562 $w = EV::stat_ns $path, $interval, $callback
563 $w = $loop->stat ($path, $interval, $callback)
564 $w = $loop->stat_ns ($path, $interval, $callback)
565 Call the callback when a file status change has been detected on
566 $path. The $path does not need to exist, changing from "path exists"
567 to "path does not exist" is a status change like any other.
568
569 The $interval is a recommended polling interval for systems where
570 OS-supported change notifications don't exist or are not supported.
571 If you use 0 then an unspecified default is used (which is highly
572 recommended!), which is to be expected to be around five seconds
573 usually.
574
575 This watcher type is not meant for massive numbers of stat watchers,
576 as even with OS-supported change notifications, this can be
577 resource-intensive.
578
579 The "stat_ns" variant doesn't start (activate) the newly created
580 watcher.
581
582 ... = $w->stat
583 This call is very similar to the perl "stat" built-in: It stats
584 (using "lstat") the path specified in the watcher and sets perls
585 stat cache (as well as EV's idea of the current stat values) to the
586 values found.
587
588 In scalar context, a boolean is return indicating success or failure
589 of the stat. In list context, the same 13-value list as with stat is
590 returned (except that the blksize and blocks fields are not
591 reliable).
592
593 In the case of an error, errno is set to "ENOENT" (regardless of the
594 actual error value) and the "nlink" value is forced to zero (if the
595 stat was successful then nlink is guaranteed to be non-zero).
596
597 See also the next two entries for more info.
598
599 ... = $w->attr
600 Just like "$w->stat", but without the initial stat'ing: this returns
601 the values most recently detected by EV. See the next entry for more
602 info.
603
604 ... = $w->prev
605 Just like "$w->stat", but without the initial stat'ing: this returns
606 the previous set of values, before the change.
607
608 That is, when the watcher callback is invoked, "$w->prev" will be
609 set to the values found *before* a change was detected, while
610 "$w->attr" returns the values found leading to the change detection.
611 The difference (if any) between "prev" and "attr" is what triggered
612 the callback.
613
614 If you did something to the filesystem object and do not want to
615 trigger yet another change, you can call "stat" to update EV's idea
616 of what the current attributes are.
617
228 $w->timeout_abs ($at, $interval) 618 $w->set ($path, $interval)
229 Resets the timeout (see "EV::timer_abs" for details). 619 Reconfigures the watcher, see the constructor above for details. Can
620 be called at any time.
230 621
231 $w->priority_set ($priority) 622 $current_path = $w->path
232 Set the priority of the watcher to $priority (0 <= $priority < 623 $old_path = $w->path ($new_path)
233 $EV::NPRI). 624 Returns the previously set path and optionally set a new one.
234 625
235BUGS 626 $current_interval = $w->interval
236 Lots. Libevent itself isn't well tested and rather buggy, and this 627 $old_interval = $w->interval ($new_interval)
237 module is quite new at the moment. 628 Returns the previously set interval and optionally set a new one.
629 Can be used to query the actual interval used.
238 630
239 Please note that the epoll method is not, in general, reliable in 631 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 632 $w = EV::idle $callback
241 forked process). If your program behaves erratically, try setting the 633 $w = EV::idle_ns $callback
242 environment variable "EVENT_NOEPOLL" first when running the program. 634 $w = $loop->idle ($callback)
635 $w = $loop->idle_ns ($callback)
636 Call the callback when there are no other pending watchers of the
637 same or higher priority (excluding check, prepare and other idle
638 watchers of the same or lower priority, of course). They are called
639 idle watchers because when the watcher is the highest priority
640 pending event in the process, the process is considered to be idle
641 at that priority.
243 642
244 In general, if you fork, then you can only use the EV module in one of 643 If you want a watcher that is only ever called when *no* other
245 the children. 644 events are outstanding you have to set the priority to "EV::MINPRI".
645
646 The process will not block as long as any idle watchers are active,
647 and they will be called repeatedly until stopped.
648
649 For example, if you have idle watchers at priority 0 and 1, and an
650 I/O watcher at priority 0, then the idle watcher at priority 1 and
651 the I/O watcher will always run when ready. Only when the idle
652 watcher at priority 1 is stopped and the I/O watcher at priority 0
653 is not pending with the 0-priority idle watcher be invoked.
654
655 The "idle_ns" variant doesn't start (activate) the newly created
656 watcher.
657
658 PREPARE WATCHERS - customise your event loop!
659 $w = EV::prepare $callback
660 $w = EV::prepare_ns $callback
661 $w = $loop->prepare ($callback)
662 $w = $loop->prepare_ns ($callback)
663 Call the callback just before the process would block. You can still
664 create/modify any watchers at this point.
665
666 See the EV::check watcher, below, for explanations and an example.
667
668 The "prepare_ns" variant doesn't start (activate) the newly created
669 watcher.
670
671 CHECK WATCHERS - customise your event loop even more!
672 $w = EV::check $callback
673 $w = EV::check_ns $callback
674 $w = $loop->check ($callback)
675 $w = $loop->check_ns ($callback)
676 Call the callback just after the process wakes up again (after it
677 has gathered events), but before any other callbacks have been
678 invoked.
679
680 This is used to integrate other event-based software into the EV
681 mainloop: You register a prepare callback and in there, you create
682 io and timer watchers as required by the other software. Here is a
683 real-world example of integrating Net::SNMP (with some details left
684 out):
685
686 our @snmp_watcher;
687
688 our $snmp_prepare = EV::prepare sub {
689 # do nothing unless active
690 $dispatcher->{_event_queue_h}
691 or return;
692
693 # make the dispatcher handle any outstanding stuff
694 ... not shown
695
696 # create an I/O watcher for each and every socket
697 @snmp_watcher = (
698 (map { EV::io $_, EV::READ, sub { } }
699 keys %{ $dispatcher->{_descriptors} }),
700
701 EV::timer +($event->[Net::SNMP::Dispatcher::_ACTIVE]
702 ? $event->[Net::SNMP::Dispatcher::_TIME] - EV::now : 0),
703 0, sub { },
704 );
705 };
706
707 The callbacks are irrelevant (and are not even being called), the
708 only purpose of those watchers is to wake up the process as soon as
709 one of those events occurs (socket readable, or timer timed out).
710 The corresponding EV::check watcher will then clean up:
711
712 our $snmp_check = EV::check sub {
713 # destroy all watchers
714 @snmp_watcher = ();
715
716 # make the dispatcher handle any new stuff
717 ... not shown
718 };
719
720 The callbacks of the created watchers will not be called as the
721 watchers are destroyed before this cna happen (remember EV::check
722 gets called first).
723
724 The "check_ns" variant doesn't start (activate) the newly created
725 watcher.
726
727 FORK WATCHERS - the audacity to resume the event loop after a fork
728 Fork watchers are called when a "fork ()" was detected. The invocation
729 is done before the event loop blocks next and before "check" watchers
730 are being called, and only in the child after the fork.
731
732 $w = EV::fork $callback
733 $w = EV::fork_ns $callback
734 $w = $loop->fork ($callback)
735 $w = $loop->fork_ns ($callback)
736 Call the callback before the event loop is resumed in the child
737 process after a fork.
738
739 The "fork_ns" variant doesn't start (activate) the newly created
740 watcher.
741
742 EMBED WATCHERS - when one backend isn't enough...
743 This is a rather advanced watcher type that lets you embed one event
744 loop into another (currently only IO events are supported in the
745 embedded loop, other types of watchers might be handled in a delayed or
746 incorrect fashion and must not be used).
747
748 See the libev documentation at
749 <http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod#code_ev_embed_code
750 _when_one_backend_> for more details.
751
752 In short, this watcher is most useful on BSD systems without working
753 kqueue to still be able to handle a large number of sockets:
754
755 my $socket_loop;
756
757 # check wether we use SELECT or POLL _and_ KQUEUE is supported
758 if (
759 (EV::backend & (EV::BACKEND_POLL | EV::BACKEND_SELECT))
760 && (EV::supported_backends & EV::embeddable_backends & EV::BACKEND_KQUEUE)
761 ) {
762 # use kqueue for sockets
763 $socket_loop = new EV::Loop EV::BACKEND_KQUEUE | EV::FLAG_NOENV;
764 }
765
766 # use the default loop otherwise
767 $socket_loop ||= EV::default_loop;
768
769 $w = EV::embed $otherloop, $callback
770 $w = EV::embed_ns $otherloop, $callback
771 $w = $loop->embed ($otherloop, $callback)
772 $w = $loop->embed_ns ($otherloop, $callback)
773 Call the callback when the embedded event loop ($otherloop) has any
774 I/O activity. The $callback should alwas be specified as "undef" in
775 this version of EV, which means the embedded event loop will be
776 managed automatically.
777
778 The "embed_ns" variant doesn't start (activate) the newly created
779 watcher.
780
781PERL SIGNALS
782 While Perl signal handling (%SIG) is not affected by EV, the behaviour
783 with EV is as the same as any other C library: Perl-signals will only be
784 handled when Perl runs, which means your signal handler might be invoked
785 only the next time an event callback is invoked.
786
787 The solution is to use EV signal watchers (see "EV::signal"), which will
788 ensure proper operations with regards to other event watchers.
789
790 If you cannot do this for whatever reason, you can also force a watcher
791 to be called on every event loop iteration by installing a "EV::check"
792 watcher:
793
794 my $async_check = EV::check sub { };
795
796 This ensures that perl gets into control for a short time to handle any
797 pending signals, and also ensures (slightly) slower overall operation.
798
799THREADS
800 Threads are not supported by this module in any way. Perl pseudo-threads
801 is evil stuff and must die. As soon as Perl gains real threads I will
802 work on thread support for it.
803
804FORK
805 Most of the "improved" event delivering mechanisms of modern operating
806 systems have quite a few problems with fork(2) (to put it bluntly: it is
807 not supported and usually destructive). Libev makes it possible to work
808 around this by having a function that recreates the kernel state after
809 fork in the child.
810
811 On non-win32 platforms, this module requires the pthread_atfork
812 functionality to do this automatically for you. This function is quite
813 buggy on most BSDs, though, so YMMV. The overhead for this is quite
814 negligible, because everything the function currently does is set a flag
815 that is checked only when the event loop gets used the next time, so
816 when you do fork but not use EV, the overhead is minimal.
817
818 On win32, there is no notion of fork so all this doesn't apply, of
819 course.
246 820
247SEE ALSO 821SEE ALSO
248 L<EV::DNS>, L<event(3)>, L<event.h>, L<evdns.h>. 822 EV::ADNS (asynchronous DNS), Glib::EV (makes Glib/Gtk2 use EV as event
249 L<EV::AnyEvent>. 823 loop), EV::Glib (embed Glib into EV), Coro::EV (efficient coroutines
824 with EV), Net::SNMP::EV (asynchronous SNMP).
250 825
251AUTHOR 826AUTHOR
252 Marc Lehmann <schmorp@schmorp.de> 827 Marc Lehmann <schmorp@schmorp.de>
253 http://home.schmorp.de/ 828 http://home.schmorp.de/
254 829

Diff Legend

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