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 1.19 by root, Tue Dec 18 01:37:46 2007 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
23 # IO 24 # IO
24 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 };
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 }; 29 };
45 30
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 $w = EV::child 666, sub {
53 warn "sigquit received (this is GNU/Linux, right?)\n"; 40 my ($w, $revents) = @_;
41 my $status = $w->rstatus;
54 }; 42 };
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 };
55 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
67 60 details on watcher semantics or some discussion on the available
68 Please note thta this module disables the libevent EPOLL method by 61 backends, or how to force a specific backend with "LIBEV_FLAGS", or just
69 default, see BUGS, below, if you need to enable it. 62 about in any case because it has much more detailed information.
70 63
71BASIC INTERFACE 64BASIC INTERFACE
72 $EV::NPRI
73 How many priority levels are available.
74
75 $EV::DIED 65 $EV::DIED
76 Must contain a reference to a function that is called when a 66 Must contain a reference to a function that is called when a
77 callback throws an exception (with $@ containing thr error). The 67 callback throws an exception (with $@ containing the error). The
78 default prints an informative message and continues. 68 default prints an informative message and continues.
79 69
80 If this callback throws an exception it will be silently ignored. 70 If this callback throws an exception it will be silently ignored.
81 71
72 $time = EV::time
73 Returns the current time in (fractional) seconds since the epoch.
74
82 $time = EV::now 75 $time = EV::now
83 Returns the time in (fractional) seconds since the epoch. 76 Returns the time the last event loop iteration has been started.
77 This is the time that (relative) timers are based on, and refering
78 to it is usually faster then calling EV::time.
84 79
85 $version = EV::version
86 $method = EV::method 80 $method = EV::method
87 Return version string and event polling method used. 81 Returns an integer describing the backend used by libev
82 (EV::METHOD_SELECT or EV::METHOD_EPOLL).
88 83
89 EV::loop $flags # EV::LOOP_ONCE, EV::LOOP_ONESHOT 84 EV::loop [$flags]
90 EV::loopexit $after 85 Begin checking for events and calling callbacks. It returns when a
91 Exit any active loop or dispatch after $after seconds or immediately 86 callback calls EV::unloop.
92 if $after is missing or zero.
93 87
94 EV::dispatch 88 The $flags argument can be one of the following:
95 Same as "EV::loop 0".
96 89
97 EV::event $callback 90 0 as above
98 Creates a new event watcher waiting for nothing, calling the given 91 EV::LOOP_ONESHOT block at most once (wait, but do not loop)
99 callback. 92 EV::LOOP_NONBLOCK do not block at all (fetch/handle events but do not wait)
100 93
94 EV::unloop [$how]
95 When called with no arguments or an argument of EV::UNLOOP_ONE,
96 makes the innermost call to EV::loop return.
97
98 When called with an argument of EV::UNLOOP_ALL, all calls to
99 EV::loop will return as fast as possible.
100
101 $count = EV::loop_count
102 Return the number of times the event loop has polled for new events.
103 Sometiems useful as a generation counter.
104
105 EV::once $fh_or_undef, $events, $timeout, $cb->($revents)
106 This function rolls together an I/O and a timer watcher for a single
107 one-shot event without the need for managing a watcher object.
108
109 If $fh_or_undef is a filehandle or file descriptor, then $events
110 must be a bitset containing either "EV::READ", "EV::WRITE" or
111 "EV::READ | EV::WRITE", indicating the type of I/O event you want to
112 wait for. If you do not want to wait for some I/O event, specify
113 "undef" for $fh_or_undef and 0 for $events).
114
115 If timeout is "undef" or negative, then there will be no timeout.
116 Otherwise a EV::timer with this value will be started.
117
118 When an error occurs or either the timeout or I/O watcher triggers,
119 then the callback will be called with the received event set (in
120 general you can expect it to be a combination of "EV:ERROR",
121 "EV::READ", "EV::WRITE" and "EV::TIMEOUT").
122
123 EV::once doesn't return anything: the watchers stay active till
124 either of them triggers, then they will be stopped and freed, and
125 the callback invoked.
126
127 EV::feed_fd_event ($fd, $revents)
128 Feed an event on a file descriptor into EV. EV will react to this
129 call as if the readyness notifications specified by $revents (a
130 combination of "EV::READ" and "EV::WRITE") happened on the file
131 descriptor $fd.
132
133 EV::feed_signal_event ($signal)
134 Feed a signal event into EV. EV will react to this call as if the
135 signal specified by $signal had occured.
136
137 WATCHER OBJECTS
138 A watcher is an object that gets created to record your interest in some
139 event. For instance, if you want to wait for STDIN to become readable,
140 you would create an EV::io watcher for that:
141
142 my $watcher = EV::io *STDIN, EV::READ, sub {
143 my ($watcher, $revents) = @_;
144 warn "yeah, STDIN should not be readable without blocking!\n"
145 };
146
147 All watchers can be active (waiting for events) or inactive (paused).
148 Only active watchers will have their callbacks invoked. All callbacks
149 will be called with at least two arguments: the watcher and a bitmask of
150 received events.
151
152 Each watcher type has its associated bit in revents, so you can use the
153 same callback for multiple watchers. The event mask is named after the
154 type, i..e. EV::child sets EV::CHILD, EV::prepare sets EV::PREPARE,
155 EV::periodic sets EV::PERIODIC and so on, with the exception of I/O
156 events (which can set both EV::READ and EV::WRITE bits), and EV::timer
157 (which uses EV::TIMEOUT).
158
159 In the rare case where one wants to create a watcher but not start it at
160 the same time, each constructor has a variant with a trailing "_ns" in
161 its name, e.g. EV::io has a non-starting variant EV::io_ns and so on.
162
163 Please note that a watcher will automatically be stopped when the
164 watcher object is destroyed, so you *need* to keep the watcher objects
165 returned by the constructors.
166
167 Also, all methods changing some aspect of a watcher (->set, ->priority,
168 ->fh and so on) automatically stop and start it again if it is active,
169 which means pending events get lost.
170
171 COMMON WATCHER METHODS
172 This section lists methods common to all watchers.
173
174 $w->start
175 Starts a watcher if it isn't active already. Does nothing to an
176 already active watcher. By default, all watchers start out in the
177 active state (see the description of the "_ns" variants if you need
178 stopped watchers).
179
180 $w->stop
181 Stop a watcher if it is active. Also clear any pending events
182 (events that have been received but that didn't yet result in a
183 callback invocation), regardless of whether the watcher was active
184 or not.
185
186 $bool = $w->is_active
187 Returns true if the watcher is active, false otherwise.
188
189 $current_data = $w->data
190 $old_data = $w->data ($new_data)
191 Queries a freely usable data scalar on the watcher and optionally
192 changes it. This is a way to associate custom data with a watcher:
193
194 my $w = EV::timer 60, 0, sub {
195 warn $_[0]->data;
196 };
197 $w->data ("print me!");
198
199 $current_cb = $w->cb
200 $old_cb = $w->cb ($new_cb)
201 Queries the callback on the watcher and optionally changes it. You
202 can do this at any time without the watcher restarting.
203
204 $current_priority = $w->priority
205 $old_priority = $w->priority ($new_priority)
206 Queries the priority on the watcher and optionally changes it.
207 Pending watchers with higher priority will be invoked first. The
208 valid range of priorities lies between EV::MAXPRI (default 2) and
209 EV::MINPRI (default -2). If the priority is outside this range it
210 will automatically be normalised to the nearest valid priority.
211
212 The default priority of any newly-created watcher is 0.
213
214 Note that the priority semantics have not yet been fleshed out and
215 are subject to almost certain change.
216
217 $w->invoke ($revents)
218 Call the callback *now* with the given event mask.
219
220 $w->feed_event ($revents)
221 Feed some events on this watcher into EV. EV will react to this call
222 as if the watcher had received the given $revents mask.
223
224 $revents = $w->clear_pending
225 If the watcher is pending, this function returns clears its pending
226 status and returns its $revents bitset (as if its callback was
227 invoked). If the watcher isn't pending it does nothing and returns
228 0.
229
230 $previous_state = $w->keepalive ($bool)
231 Normally, "EV::loop" will return when there are no active watchers
232 (which is a "deadlock" because no progress can be made anymore).
233 This is convinient because it allows you to start your watchers (and
234 your jobs), call "EV::loop" once and when it returns you know that
235 all your jobs are finished (or they forgot to register some watchers
236 for their task :).
237
238 Sometimes, however, this gets in your way, for example when you the
239 module that calls "EV::loop" (usually the main program) is not the
240 same module as a long-living watcher (for example a DNS client
241 module written by somebody else even). Then you might want any
242 outstanding requests to be handled, but you would not want to keep
243 "EV::loop" from returning just because you happen to have this
244 long-running UDP port watcher.
245
246 In this case you can clear the keepalive status, which means that
247 even though your watcher is active, it won't keep "EV::loop" from
248 returning.
249
250 The initial value for keepalive is true (enabled), and you cna
251 change it any time.
252
253 Example: Register an I/O watcher for some UDP socket but do not keep
254 the event loop from running just because of that watcher.
255
256 my $udp_socket = ...
257 my $udp_watcher = EV::io $udp_socket, EV::READ, sub { ... };
258 $udp_watcher->keepalive (0);
259
260 WATCHER TYPES
261 Each of the following subsections describes a single watcher type.
262
263 I/O WATCHERS - is this file descriptor readable or writable?
101 my $w = EV::io $fileno_or_fh, $eventmask, $callback 264 $w = EV::io $fileno_or_fh, $eventmask, $callback
102 my $w = EV::io_ns $fileno_or_fh, $eventmask, $callback 265 $w = EV::io_ns $fileno_or_fh, $eventmask, $callback
103 As long as the returned watcher object is alive, call the $callback 266 As long as the returned watcher object is alive, call the $callback
104 when the events specified in $eventmask happen. Initially, the 267 when at least one of events specified in $eventmask occurs.
105 timeout is disabled.
106 268
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: 269 The $eventmask can be one or more of these constants ORed together:
116 270
117 EV::READ wait until read() wouldn't block anymore 271 EV::READ wait until read() wouldn't block anymore
118 EV::WRITE wait until write() wouldn't block anymore 272 EV::WRITE wait until write() wouldn't block anymore
119 EV::PERSIST stay active after a (non-timeout) event occured
120 273
121 The "io_ns" variant doesn't add/start the newly created watcher. 274 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. 275 watcher.
173 276
174 my $w = EV::signal $signal, $callback 277 $w->set ($fileno_or_fh, $eventmask)
175 my $w = EV::signal_ns $signal, $callback 278 Reconfigures the watcher, see the constructor above for details. Can
176 Call the callback when $signal is received (the signal can be 279 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.
210 280
211 $current_fh = $w->fh 281 $current_fh = $w->fh
212 $old_fh = $w->fh ($new_fh) 282 $old_fh = $w->fh ($new_fh)
213 Returns the previously set filehandle and optionally set a new one 283 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).
220 284
221 $current_eventmask = $w->events 285 $current_eventmask = $w->events
222 $old_eventmask = $w->events ($new_eventmask) 286 $old_eventmask = $w->events ($new_eventmask)
223 Returns the previously set event mask and optionally set a new one. 287 Returns the previously set event mask and optionally set a new one.
224 288
289 TIMER WATCHERS - relative and optionally repeating timeouts
290 $w = EV::timer $after, $repeat, $callback
291 $w = EV::timer_ns $after, $repeat, $callback
292 Calls the callback after $after seconds (which may be fractional).
293 If $repeat is non-zero, the timer will be restarted (with the
294 $repeat value as $after) after the callback returns.
295
296 This means that the callback would be called roughly after $after
297 seconds, and then every $repeat seconds. The timer does his best not
298 to drift, but it will not invoke the timer more often then once per
299 event loop iteration, and might drift in other cases. If that isn't
300 acceptable, look at EV::periodic, which can provide long-term stable
301 timers.
302
303 The timer is based on a monotonic clock, that is, if somebody is
304 sitting in front of the machine while the timer is running and
305 changes the system clock, the timer will nevertheless run (roughly)
306 the same time.
307
308 The "timer_ns" variant doesn't start (activate) the newly created
309 watcher.
310
225 $w->timeout ($after, $repeat) 311 $w->set ($after, $repeat)
226 Resets the timeout (see "EV::timer" for details). 312 Reconfigures the watcher, see the constructor above for details. Can
313 be called at any time.
227 314
315 $w->again
316 Similar to the "start" method, but has special semantics for
317 repeating timers:
318
319 If the timer is active and non-repeating, it will be stopped.
320
321 If the timer is active and repeating, reset the timeout to occur
322 $repeat seconds after now.
323
324 If the timer is inactive and repeating, start it using the repeat
325 value.
326
327 Otherwise do nothing.
328
329 This behaviour is useful when you have a timeout for some IO
330 operation. You create a timer object with the same value for $after
331 and $repeat, and then, in the read/write watcher, run the "again"
332 method on the timeout.
333
334 PERIODIC WATCHERS - to cron or not to cron?
335 $w = EV::periodic $at, $interval, $reschedule_cb, $callback
336 $w = EV::periodic_ns $at, $interval, $reschedule_cb, $callback
337 Similar to EV::timer, but is not based on relative timeouts but on
338 absolute times. Apart from creating "simple" timers that trigger
339 "at" the specified time, it can also be used for non-drifting
340 absolute timers and more complex, cron-like, setups that are not
341 adversely affected by time jumps (i.e. when the system clock is
342 changed by explicit date -s or other means such as ntpd). It is also
343 the most complex watcher type in EV.
344
345 It has three distinct "modes":
346
347 * absolute timer ($interval = $reschedule_cb = 0)
348 This time simply fires at the wallclock time $at and doesn't
349 repeat. It will not adjust when a time jump occurs, that is, if
350 it is to be run at January 1st 2011 then it will run when the
351 system time reaches or surpasses this time.
352
353 * non-repeating interval timer ($interval > 0, $reschedule_cb = 0)
354 In this mode the watcher will always be scheduled to time out at
355 the next "$at + N * $interval" time (for some integer N) and
356 then repeat, regardless of any time jumps.
357
358 This can be used to create timers that do not drift with respect
359 to system time:
360
361 my $hourly = EV::periodic 0, 3600, 0, sub { print "once/hour\n" };
362
363 That doesn't mean there will always be 3600 seconds in between
364 triggers, but only that the the clalback will be called when the
365 system time shows a full hour (UTC).
366
367 Another way to think about it (for the mathematically inclined)
368 is that EV::periodic will try to run the callback in this mode
369 at the next possible time where "$time = $at (mod $interval)",
370 regardless of any time jumps.
371
372 * manual reschedule mode ($reschedule_cb = coderef)
373 In this mode $interval and $at are both being ignored. Instead,
374 each time the periodic watcher gets scheduled, the reschedule
375 callback ($reschedule_cb) will be called with the watcher as
376 first, and the current time as second argument.
377
378 *This callback MUST NOT stop or destroy this or any other
379 periodic watcher, ever*. If you need to stop it, return 1e30 and
380 stop it afterwards.
381
382 It must return the next time to trigger, based on the passed
383 time value (that is, the lowest time value larger than to the
384 second argument). It will usually be called just before the
385 callback will be triggered, but might be called at other times,
386 too.
387
388 This can be used to create very complex timers, such as a timer
389 that triggers on each midnight, local time (actually 24 hours
390 after the last midnight, to keep the example simple. If you know
391 a way to do it correctly in about the same space (without
392 requiring elaborate modules), drop me a note :):
393
394 my $daily = EV::periodic 0, 0, sub {
395 my ($w, $now) = @_;
396
397 use Time::Local ();
398 my (undef, undef, undef, $d, $m, $y) = localtime $now;
399 86400 + Time::Local::timelocal 0, 0, 0, $d, $m, $y
400 }, sub {
401 print "it's midnight or likely shortly after, now\n";
402 };
403
404 The "periodic_ns" variant doesn't start (activate) the newly created
405 watcher.
406
407 $w->set ($at, $interval, $reschedule_cb)
408 Reconfigures the watcher, see the constructor above for details. Can
409 be called at any time.
410
411 $w->again
412 Simply stops and starts the watcher again.
413
414 $time = $w->at
415 Return the time that the watcher is expected to trigger next.
416
417 SIGNAL WATCHERS - signal me when a signal gets signalled!
418 $w = EV::signal $signal, $callback
419 $w = EV::signal_ns $signal, $callback
420 Call the callback when $signal is received (the signal can be
421 specified by number or by name, just as with "kill" or %SIG).
422
423 EV will grab the signal for the process (the kernel only allows one
424 component to receive a signal at a time) when you start a signal
425 watcher, and removes it again when you stop it. Perl does the same
426 when you add/remove callbacks to %SIG, so watch out.
427
428 You can have as many signal watchers per signal as you want.
429
430 The "signal_ns" variant doesn't start (activate) the newly created
431 watcher.
432
433 $w->set ($signal)
434 Reconfigures the watcher, see the constructor above for details. Can
435 be called at any time.
436
437 $current_signum = $w->signal
438 $old_signum = $w->signal ($new_signal)
439 Returns the previously set signal (always as a number not name) and
440 optionally set a new one.
441
442 CHILD WATCHERS - watch out for process status changes
443 $w = EV::child $pid, $callback
444 $w = EV::child_ns $pid, $callback
445 Call the callback when a status change for pid $pid (or any pid if
446 $pid is 0) has been received. More precisely: when the process
447 receives a "SIGCHLD", EV will fetch the outstanding exit/wait status
448 for all changed/zombie children and call the callback.
449
450 It is valid (and fully supported) to install a child watcher after a
451 child has exited but before the event loop has started its next
452 iteration (for example, first you "fork", then the new child process
453 might exit, and only then do you install a child watcher in the
454 parent for the new pid).
455
456 You can access both exit (or tracing) status and pid by using the
457 "rstatus" and "rpid" methods on the watcher object.
458
459 You can have as many pid watchers per pid as you want, they will all
460 be called.
461
462 The "child_ns" variant doesn't start (activate) the newly created
463 watcher.
464
465 $w->set ($pid)
466 Reconfigures the watcher, see the constructor above for details. Can
467 be called at any time.
468
469 $current_pid = $w->pid
470 $old_pid = $w->pid ($new_pid)
471 Returns the previously set process id and optionally set a new one.
472
473 $exit_status = $w->rstatus
474 Return the exit/wait status (as returned by waitpid, see the waitpid
475 entry in perlfunc).
476
477 $pid = $w->rpid
478 Return the pid of the awaited child (useful when you have installed
479 a watcher for all pids).
480
481 STAT WATCHERS - did the file attributes just change?
482 $w = EV::stat $path, $interval, $callback
483 $w = EV::stat_ns $path, $interval, $callback
484 Call the callback when a file status change has been detected on
485 $path. The $path does not need to exist, changing from "path exists"
486 to "path does not exist" is a status change like any other.
487
488 The $interval is a recommended polling interval for systems where
489 OS-supported change notifications don't exist or are not supported.
490 If you use 0 then an unspecified default is used (which is highly
491 recommended!), which is to be expected to be around five seconds
492 usually.
493
494 This watcher type is not meant for massive numbers of stat watchers,
495 as even with OS-supported change notifications, this can be
496 resource-intensive.
497
498 The "stat_ns" variant doesn't start (activate) the newly created
499 watcher.
500
501 ... = $w->stat
502 This call is very similar to the perl "stat" built-in: It stats
503 (using "lstat") the path specified in the watcher and sets perls
504 stat cache (as well as EV's idea of the current stat values) to the
505 values found.
506
507 In scalar context, a boolean is return indicating success or failure
508 of the stat. In list context, the same 13-value list as with stat is
509 returned (except that the blksize and blocks fields are not
510 reliable).
511
512 In the case of an error, errno is set to "ENOENT" (regardless of the
513 actual error value) and the "nlink" value is forced to zero (if the
514 stat was successful then nlink is guaranteed to be non-zero).
515
516 See also the next two entries for more info.
517
518 ... = $w->attr
519 Just like "$w->stat", but without the initial stat'ing: this returns
520 the values most recently detected by EV. See the next entry for more
521 info.
522
523 ... = $w->prev
524 Just like "$w->stat", but without the initial stat'ing: this returns
525 the previous set of values, before the change.
526
527 That is, when the watcher callback is invoked, "$w->prev" will be
528 set to the values found *before* a change was detected, while
529 "$w->attr" returns the values found leading to the change detection.
530 The difference (if any) between "prev" and "attr" is what triggered
531 the callback.
532
533 If you did something to the filesystem object and do not want to
534 trigger yet another change, you can call "stat" to update EV's idea
535 of what the current attributes are.
536
228 $w->timeout_abs ($at, $interval) 537 $w->set ($path, $interval)
229 Resets the timeout (see "EV::timer_abs" for details). 538 Reconfigures the watcher, see the constructor above for details. Can
539 be called at any time.
230 540
231 $w->priority_set ($priority) 541 $current_path = $w->path
232 Set the priority of the watcher to $priority (0 <= $priority < 542 $old_path = $w->path ($new_path)
233 $EV::NPRI). 543 Returns the previously set path and optionally set a new one.
234 544
235BUGS 545 $current_interval = $w->interval
236 Lots. Libevent itself isn't well tested and rather buggy, and this 546 $old_interval = $w->interval ($new_interval)
237 module is quite new at the moment. 547 Returns the previously set interval and optionally set a new one.
548 Can be used to query the actual interval used.
238 549
239 Please note that the epoll method is not, in general, reliable in 550 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 551 $w = EV::idle $callback
241 forked process). If your program behaves erratically, try setting the 552 $w = EV::idle_ns $callback
242 environment variable "EVENT_NOEPOLL" first when running the program. 553 Call the callback when there are no other pending watchers of the
554 same or higher priority (excluding check, prepare and other idle
555 watchers of the same or lower priority, of course). They are called
556 idle watchers because when the watcher is the highest priority
557 pending event in the process, the process is considered to be idle
558 at that priority.
243 559
244 In general, if you fork, then you can only use the EV module in one of 560 If you want a watcher that is only ever called when *no* other
245 the children. 561 events are outstanding you have to set the priority to "EV::MINPRI".
562
563 The process will not block as long as any idle watchers are active,
564 and they will be called repeatedly until stopped.
565
566 For example, if you have idle watchers at priority 0 and 1, and an
567 I/O watcher at priority 0, then the idle watcher at priority 1 and
568 the I/O watcher will always run when ready. Only when the idle
569 watcher at priority 1 is stopped and the I/O watcher at priority 0
570 is not pending with the 0-priority idle watcher be invoked.
571
572 The "idle_ns" variant doesn't start (activate) the newly created
573 watcher.
574
575 PREPARE WATCHERS - customise your event loop!
576 $w = EV::prepare $callback
577 $w = EV::prepare_ns $callback
578 Call the callback just before the process would block. You can still
579 create/modify any watchers at this point.
580
581 See the EV::check watcher, below, for explanations and an example.
582
583 The "prepare_ns" variant doesn't start (activate) the newly created
584 watcher.
585
586 CHECK WATCHERS - customise your event loop even more!
587 $w = EV::check $callback
588 $w = EV::check_ns $callback
589 Call the callback just after the process wakes up again (after it
590 has gathered events), but before any other callbacks have been
591 invoked.
592
593 This is used to integrate other event-based software into the EV
594 mainloop: You register a prepare callback and in there, you create
595 io and timer watchers as required by the other software. Here is a
596 real-world example of integrating Net::SNMP (with some details left
597 out):
598
599 our @snmp_watcher;
600
601 our $snmp_prepare = EV::prepare sub {
602 # do nothing unless active
603 $dispatcher->{_event_queue_h}
604 or return;
605
606 # make the dispatcher handle any outstanding stuff
607 ... not shown
608
609 # create an I/O watcher for each and every socket
610 @snmp_watcher = (
611 (map { EV::io $_, EV::READ, sub { } }
612 keys %{ $dispatcher->{_descriptors} }),
613
614 EV::timer +($event->[Net::SNMP::Dispatcher::_ACTIVE]
615 ? $event->[Net::SNMP::Dispatcher::_TIME] - EV::now : 0),
616 0, sub { },
617 );
618 };
619
620 The callbacks are irrelevant (and are not even being called), the
621 only purpose of those watchers is to wake up the process as soon as
622 one of those events occurs (socket readable, or timer timed out).
623 The corresponding EV::check watcher will then clean up:
624
625 our $snmp_check = EV::check sub {
626 # destroy all watchers
627 @snmp_watcher = ();
628
629 # make the dispatcher handle any new stuff
630 ... not shown
631 };
632
633 The callbacks of the created watchers will not be called as the
634 watchers are destroyed before this cna happen (remember EV::check
635 gets called first).
636
637 The "check_ns" variant doesn't start (activate) the newly created
638 watcher.
639
640 FORK WATCHERS - the audacity to resume the event loop after a fork
641 Fork watchers are called when a "fork ()" was detected. The invocation
642 is done before the event loop blocks next and before "check" watchers
643 are being called, and only in the child after the fork.
644
645 $w = EV::fork $callback
646 $w = EV::fork_ns $callback
647 Call the callback before the event loop is resumed in the child
648 process after a fork.
649
650 The "fork_ns" variant doesn't start (activate) the newly created
651 watcher.
652
653PERL SIGNALS
654 While Perl signal handling (%SIG) is not affected by EV, the behaviour
655 with EV is as the same as any other C library: Perl-signals will only be
656 handled when Perl runs, which means your signal handler might be invoked
657 only the next time an event callback is invoked.
658
659 The solution is to use EV signal watchers (see "EV::signal"), which will
660 ensure proper operations with regards to other event watchers.
661
662 If you cannot do this for whatever reason, you can also force a watcher
663 to be called on every event loop iteration by installing a "EV::check"
664 watcher:
665
666 my $async_check = EV::check sub { };
667
668 This ensures that perl shortly gets into control for a short time, and
669 also ensures slower overall operation.
670
671THREADS
672 Threads are not supported by this module in any way. Perl pseudo-threads
673 is evil stuff and must die. As soon as Perl gains real threads I will
674 work on thread support for it.
675
676FORK
677 Most of the "improved" event delivering mechanisms of modern operating
678 systems have quite a few problems with fork(2) (to put it bluntly: it is
679 not supported and usually destructive). Libev makes it possible to work
680 around this by having a function that recreates the kernel state after
681 fork in the child.
682
683 On non-win32 platforms, this module requires the pthread_atfork
684 functionality to do this automatically for you. This function is quite
685 buggy on most BSDs, though, so YMMV. The overhead for this is quite
686 negligible, because everything the function currently does is set a flag
687 that is checked only when the event loop gets used the next time, so
688 when you do fork but not use EV, the overhead is minimal.
689
690 On win32, there is no notion of fork so all this doesn't apply, of
691 course.
246 692
247SEE ALSO 693SEE ALSO
248 L<EV::DNS>, L<event(3)>, L<event.h>, L<evdns.h>. 694 EV::ADNS (asynchronous dns), Glib::EV (makes Glib/Gtk2 use EV as event
249 L<EV::AnyEvent>. 695 loop), Coro::EV (efficient coroutines with EV).
250 696
251AUTHOR 697AUTHOR
252 Marc Lehmann <schmorp@schmorp.de> 698 Marc Lehmann <schmorp@schmorp.de>
253 http://home.schmorp.de/ 699 http://home.schmorp.de/
254 700

Diff Legend

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