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Revision 1.6 by root, Thu Nov 1 17:32:39 2007 UTC vs.
Revision 1.19 by root, Tue Dec 18 01:37:46 2007 UTC

… …
9 9
10 my $w = EV::timer 2, 0, sub { 10 my $w = EV::timer 2, 0, sub {
11 warn "is called after 2s"; 11 warn "is called after 2s";
12 }; 12 };
13 13
14 my $w = EV::timer 2, 1, sub { 14 my $w = EV::timer 2, 2, sub {
15 warn "is called roughly every 2s (repeat = 1)"; 15 warn "is called roughly every 2s (repeat = 2)";
16 }; 16 };
17 17
18 undef $w; # destroy event watcher again 18 undef $w; # destroy event watcher again
19 19
20 my $w = EV::periodic 0, 60, sub { 20 my $w = EV::periodic 0, 60, 0, sub {
21 warn "is called every minute, on the minute, exactly"; 21 warn "is called every minute, on the minute, exactly";
22 }; 22 };
23 23
24 # IO 24 # IO
25 25
26 my $w = EV::io *STDIN, EV::READ, sub { 26 my $w = EV::io *STDIN, EV::READ, sub {
27 my ($w, $revents) = @_; # all callbacks get the watcher object and event mask 27 my ($w, $revents) = @_; # all callbacks receive the watcher and event mask
28 warn "stdin is readable, you entered: ", <STDIN>; 28 warn "stdin is readable, you entered: ", <STDIN>;
29 }; 29 };
30 30
31 # SIGNALS 31 # SIGNALS
32 32
33 my $w = EV::signal 'QUIT', sub { 33 my $w = EV::signal 'QUIT', sub {
34 warn "sigquit received\n"; 34 warn "sigquit received\n";
35 }; 35 };
36 36
37 # CHILD/PID STATUS CHANGES
38
37 my $w = EV::signal 3, sub { 39 my $w = EV::child 666, sub {
38 warn "sigquit received (this is GNU/Linux, right?)\n"; 40 my ($w, $revents) = @_;
41 my $status = $w->rstatus;
39 }; 42 };
40 43
41 # CHILD/PID STATUS CHANGES 44 # STAT CHANGES
42 45 my $w = EV::stat "/etc/passwd", 10, sub {
43 my $w = EV::child 666, sub {
44 my ($w, $revents, $status) = @_; 46 my ($w, $revents) = @_;
47 warn $w->path, " has changed somehow.\n";
45 }; 48 };
46 49
47 # MAINLOOP 50 # MAINLOOP
48 EV::loop; # loop until EV::loop_done is called 51 EV::loop; # loop until EV::unloop is called or all watchers stop
49 EV::loop EV::LOOP_ONESHOT; # block until at least one event could be handled 52 EV::loop EV::LOOP_ONESHOT; # block until at least one event could be handled
50 EV::loop EV::LOOP_NONBLOCK; # try to handle same events, but do not block 53 EV::loop EV::LOOP_NONBLOCK; # try to handle same events, but do not block
51 54
52DESCRIPTION 55DESCRIPTION
53 This module provides an interface to libev 56 This module provides an interface to libev
54 (<http://software.schmorp.de/pkg/libev.html>). 57 (<http://software.schmorp.de/pkg/libev.html>). While the documentation
58 below is comprehensive, one might also consult the documentation of
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.
55 63
56BASIC INTERFACE 64BASIC INTERFACE
57 $EV::DIED 65 $EV::DIED
58 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
59 callback throws an exception (with $@ containing thr error). The 67 callback throws an exception (with $@ containing the error). The
60 default prints an informative message and continues. 68 default prints an informative message and continues.
61 69
62 If this callback throws an exception it will be silently ignored. 70 If this callback throws an exception it will be silently ignored.
63 71
64 $time = EV::time 72 $time = EV::time
… …
67 $time = EV::now 75 $time = EV::now
68 Returns the time the last event loop iteration has been started. 76 Returns the time the last event loop iteration has been started.
69 This is the time that (relative) timers are based on, and refering 77 This is the time that (relative) timers are based on, and refering
70 to it is usually faster then calling EV::time. 78 to it is usually faster then calling EV::time.
71 79
72 $method = EV::ev_method 80 $method = EV::method
73 Returns an integer describing the backend used by libev 81 Returns an integer describing the backend used by libev
74 (EV::METHOD_SELECT or EV::METHOD_EPOLL). 82 (EV::METHOD_SELECT or EV::METHOD_EPOLL).
75 83
76 EV::loop [$flags] 84 EV::loop [$flags]
77 Begin checking for events and calling callbacks. It returns when a 85 Begin checking for events and calling callbacks. It returns when a
78 callback calls EV::loop_done. 86 callback calls EV::unloop.
79 87
80 The $flags argument can be one of the following: 88 The $flags argument can be one of the following:
81 89
82 0 as above 90 0 as above
83 EV::LOOP_ONESHOT block at most once (wait, but do not loop) 91 EV::LOOP_ONESHOT block at most once (wait, but do not loop)
84 EV::LOOP_NONBLOCK do not block at all (fetch/handle events but do not wait) 92 EV::LOOP_NONBLOCK do not block at all (fetch/handle events but do not wait)
85 93
86 EV::loop_done [$how] 94 EV::unloop [$how]
87 When called with no arguments or an argument of 1, makes the 95 When called with no arguments or an argument of EV::UNLOOP_ONE,
88 innermost call to EV::loop return. 96 makes the innermost call to EV::loop return.
89 97
90 When called with an agrument of 2, all calls to EV::loop will return 98 When called with an argument of EV::UNLOOP_ALL, all calls to
91 as fast as possible. 99 EV::loop will return as fast as possible.
92 100
93 WATCHER 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
94 A watcher is an object that gets created to record your interest in some 138 A watcher is an object that gets created to record your interest in some
95 event. For instance, if you want to wait for STDIN to become readable, 139 event. For instance, if you want to wait for STDIN to become readable,
96 you would create an EV::io watcher for that: 140 you would create an EV::io watcher for that:
97 141
98 my $watcher = EV::io *STDIN, EV::READ, sub { 142 my $watcher = EV::io *STDIN, EV::READ, sub {
… …
106 received events. 150 received events.
107 151
108 Each watcher type has its associated bit in revents, so you can use the 152 Each watcher type has its associated bit in revents, so you can use the
109 same callback for multiple watchers. The event mask is named after the 153 same callback for multiple watchers. The event mask is named after the
110 type, i..e. EV::child sets EV::CHILD, EV::prepare sets EV::PREPARE, 154 type, i..e. EV::child sets EV::CHILD, EV::prepare sets EV::PREPARE,
111 EV::periodic sets EV::PERIODIC and so on, with the exception of IO 155 EV::periodic sets EV::PERIODIC and so on, with the exception of I/O
112 events (which can set both EV::READ and EV::WRITE bits), and EV::timer 156 events (which can set both EV::READ and EV::WRITE bits), and EV::timer
113 (which uses EV::TIMEOUT). 157 (which uses EV::TIMEOUT).
114 158
115 In the rare case where one wants to create a watcher but not start it at 159 In the rare case where one wants to create a watcher but not start it at
116 the same time, each constructor has a variant with a trailing "_ns" in 160 the same time, each constructor has a variant with a trailing "_ns" in
117 its name, e.g. EV::io has a non-starting variant EV::io_ns and so on. 161 its name, e.g. EV::io has a non-starting variant EV::io_ns and so on.
118 162
119 Please note that a watcher will automatically be stopped when the 163 Please note that a watcher will automatically be stopped when the
120 watcher object is returned, so you *need* to keep the watcher objects 164 watcher object is destroyed, so you *need* to keep the watcher objects
121 returned by the constructors. 165 returned by the constructors.
122 166
123 WATCHER TYPES 167 Also, all methods changing some aspect of a watcher (->set, ->priority,
124 Now lets move to the existing watcher types and asociated methods. 168 ->fh and so on) automatically stop and start it again if it is active,
169 which means pending events get lost.
125 170
126 The following methods are available for all watchers. Then followes a 171 COMMON WATCHER METHODS
127 description of each watcher constructor (EV::io, EV::timer, 172 This section lists methods common to all watchers.
128 EV::periodic, EV::signal, EV::child, EV::idle, EV::prepare and
129 EV::check), followed by any type-specific methods (if any).
130 173
131 $w->start 174 $w->start
132 Starts a watcher if it isn't active already. Does nothing to an 175 Starts a watcher if it isn't active already. Does nothing to an
133 already active watcher. By default, all watchers start out in the 176 already active watcher. By default, all watchers start out in the
134 active state (see the description of the "_ns" variants if you need 177 active state (see the description of the "_ns" variants if you need
135 stopped watchers). 178 stopped watchers).
136 179
137 $w->stop 180 $w->stop
138 Stop a watcher if it is active. Also clear any pending events 181 Stop a watcher if it is active. Also clear any pending events
139 (events that have been received but that didn't yet result in a 182 (events that have been received but that didn't yet result in a
140 callback invocation), regardless of wether the watcher was active or 183 callback invocation), regardless of whether the watcher was active
141 not. 184 or not.
142 185
143 $bool = $w->is_active 186 $bool = $w->is_active
144 Returns true if the watcher is active, false otherwise. 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!");
145 198
146 $current_cb = $w->cb 199 $current_cb = $w->cb
147 $old_cb = $w->cb ($new_cb) 200 $old_cb = $w->cb ($new_cb)
148 Queries the callback on the watcher and optionally changes it. You 201 Queries the callback on the watcher and optionally changes it. You
149 cna do this at any time. 202 can do this at any time without the watcher restarting.
150 203
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
151 $w->trigger ($revents) 217 $w->invoke ($revents)
152 Call the callback *now* with the given event mask. 218 Call the callback *now* with the given event mask.
153 219
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?
154 $w = EV::io $fileno_or_fh, $eventmask, $callback 264 $w = EV::io $fileno_or_fh, $eventmask, $callback
155 $w = EV::io_ns $fileno_or_fh, $eventmask, $callback 265 $w = EV::io_ns $fileno_or_fh, $eventmask, $callback
156 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
157 when the events specified in $eventmask. 267 when at least one of events specified in $eventmask occurs.
158 268
159 The $eventmask can be one or more of these constants ORed together: 269 The $eventmask can be one or more of these constants ORed together:
160 270
161 EV::READ wait until read() wouldn't block anymore 271 EV::READ wait until read() wouldn't block anymore
162 EV::WRITE wait until write() wouldn't block anymore 272 EV::WRITE wait until write() wouldn't block anymore
… …
174 284
175 $current_eventmask = $w->events 285 $current_eventmask = $w->events
176 $old_eventmask = $w->events ($new_eventmask) 286 $old_eventmask = $w->events ($new_eventmask)
177 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.
178 288
289 TIMER WATCHERS - relative and optionally repeating timeouts
179 $w = EV::timer $after, $repeat, $callback 290 $w = EV::timer $after, $repeat, $callback
180 $w = EV::timer_ns $after, $repeat, $callback 291 $w = EV::timer_ns $after, $repeat, $callback
181 Calls the callback after $after seconds. If $repeat is non-zero, the 292 Calls the callback after $after seconds (which may be fractional).
182 timer will be restarted (with the $repeat value as $after) after the 293 If $repeat is non-zero, the timer will be restarted (with the
183 callback returns. 294 $repeat value as $after) after the callback returns.
184 295
185 This means that the callback would be called roughly after $after 296 This means that the callback would be called roughly after $after
186 seconds, and then every $repeat seconds. "Roughly" because the time 297 seconds, and then every $repeat seconds. The timer does his best not
187 of callback processing is not taken into account, so the timer will 298 to drift, but it will not invoke the timer more often then once per
188 slowly drift. If that isn't acceptable, look at EV::periodic. 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.
189 302
190 The timer is based on a monotonic clock, that is if somebody is 303 The timer is based on a monotonic clock, that is, if somebody is
191 sitting in front of the machine while the timer is running and 304 sitting in front of the machine while the timer is running and
192 changes the system clock, the timer will nevertheless run (roughly) 305 changes the system clock, the timer will nevertheless run (roughly)
193 the same time. 306 the same time.
194 307
195 The "timer_ns" variant doesn't start (activate) the newly created 308 The "timer_ns" variant doesn't start (activate) the newly created
196 watcher. 309 watcher.
197 310
198 $w->set ($after, $repeat) 311 $w->set ($after, $repeat)
199 Reconfigures the watcher, see the constructor above for details. Can 312 Reconfigures the watcher, see the constructor above for details. Can
200 be at any time. 313 be called at any time.
201 314
202 $w->again 315 $w->again
203 Similar to the "start" method, but has special semantics for 316 Similar to the "start" method, but has special semantics for
204 repeating timers: 317 repeating timers:
205 318
319 If the timer is active and non-repeating, it will be stopped.
320
206 If the timer is active and repeating, reset the timeout to occur 321 If the timer is active and repeating, reset the timeout to occur
207 $repeat seconds after now. 322 $repeat seconds after now.
208 323
209 If the timer is active and non-repeating, it will be stopped.
210
211 If the timer is in active and repeating, start it. 324 If the timer is inactive and repeating, start it using the repeat
325 value.
212 326
213 Otherwise do nothing. 327 Otherwise do nothing.
214 328
215 This behaviour is useful when you have a timeout for some IO 329 This behaviour is useful when you have a timeout for some IO
216 operation. You create a timer object with the same value for $after 330 operation. You create a timer object with the same value for $after
217 and $repeat, and then, in the read/write watcher, run the "again" 331 and $repeat, and then, in the read/write watcher, run the "again"
218 method on the timeout. 332 method on the timeout.
219 333
334 PERIODIC WATCHERS - to cron or not to cron?
220 $w = EV::periodic $at, $interval, $callback 335 $w = EV::periodic $at, $interval, $reschedule_cb, $callback
221 $w = EV::periodic_ns $at, $interval, $callback 336 $w = EV::periodic_ns $at, $interval, $reschedule_cb, $callback
222 Similar to EV::timer, but the time is given as an absolute point in 337 Similar to EV::timer, but is not based on relative timeouts but on
223 time ($at), plus an optional $interval. 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.
224 344
225 If the $interval is zero, then the callback will be called at the 345 It has three distinct "modes":
226 time $at if that is in the future, or as soon as possible if it is
227 in the past. It will not automatically repeat.
228 346
229 If the $interval is nonzero, then the watcher will always be 347 * absolute timer ($interval = $reschedule_cb = 0)
230 scheduled to time out at the next "$at + N * $interval" time. 348 This time simply fires at the wallclock time $at and doesn't
349 repeat. It will not adjust when a time jump occurs, that is, if
350 it is to be run at January 1st 2011 then it will run when the
351 system time reaches or surpasses this time.
231 352
232 This can be used to schedule a callback to run at very regular 353 * non-repeating interval timer ($interval > 0, $reschedule_cb = 0)
233 intervals, as long as the processing time is less then the interval 354 In this mode the watcher will always be scheduled to time out at
234 (otherwise obviously events will be skipped). 355 the next "$at + N * $interval" time (for some integer N) and
356 then repeat, regardless of any time jumps.
235 357
358 This can be used to create timers that do not drift with respect
359 to system time:
360
361 my $hourly = EV::periodic 0, 3600, 0, sub { print "once/hour\n" };
362
363 That doesn't mean there will always be 3600 seconds in between
364 triggers, but only that the the clalback will be called when the
365 system time shows a full hour (UTC).
366
236 Another way to think about it (for the mathematically inclined) is 367 Another way to think about it (for the mathematically inclined)
237 that EV::periodic will try to run the callback at the next possible 368 is that EV::periodic will try to run the callback in this mode
238 time where "$time = $at (mod $interval)", regardless of any time 369 at the next possible time where "$time = $at (mod $interval)",
239 jumps. 370 regardless of any time jumps.
240 371
241 This periodic timer is based on "wallclock time", that is, if the 372 * manual reschedule mode ($reschedule_cb = coderef)
242 clock changes ("ntp", "date -s" etc.), then the timer will 373 In this mode $interval and $at are both being ignored. Instead,
243 nevertheless run at the specified time. This means it will never 374 each time the periodic watcher gets scheduled, the reschedule
244 drift (it might jitter, but it will not drift). 375 callback ($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 };
245 403
246 The "periodic_ns" variant doesn't start (activate) the newly created 404 The "periodic_ns" variant doesn't start (activate) the newly created
247 watcher. 405 watcher.
248 406
249 $w->set ($at, $interval) 407 $w->set ($at, $interval, $reschedule_cb)
250 Reconfigures the watcher, see the constructor above for details. Can 408 Reconfigures the watcher, see the constructor above for details. Can
251 be at any time. 409 be called at any time.
252 410
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!
253 $w = EV::signal $signal, $callback 418 $w = EV::signal $signal, $callback
254 $w = EV::signal_ns $signal, $callback 419 $w = EV::signal_ns $signal, $callback
255 Call the callback when $signal is received (the signal can be 420 Call the callback when $signal is received (the signal can be
256 specified by number or by name, just as with kill or %SIG). 421 specified by number or by name, just as with "kill" or %SIG).
257 422
258 EV will grab the signal for the process (the kernel only allows one 423 EV will grab the signal for the process (the kernel only allows one
259 component to receive a signal at a time) when you start a signal 424 component to receive a signal at a time) when you start a signal
260 watcher, and removes it again when you stop it. Perl does the same 425 watcher, and removes it again when you stop it. Perl does the same
261 when you add/remove callbacks to %SIG, so watch out. 426 when you add/remove callbacks to %SIG, so watch out.
… …
265 The "signal_ns" variant doesn't start (activate) the newly created 430 The "signal_ns" variant doesn't start (activate) the newly created
266 watcher. 431 watcher.
267 432
268 $w->set ($signal) 433 $w->set ($signal)
269 Reconfigures the watcher, see the constructor above for details. Can 434 Reconfigures the watcher, see the constructor above for details. Can
270 be at any time. 435 be called at any time.
271 436
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
272 $w = EV::child $pid, $callback 443 $w = EV::child $pid, $callback
273 $w = EV::child_ns $pid, $callback 444 $w = EV::child_ns $pid, $callback
274 Call the callback when a status change for pid $pid (or any pid if 445 Call the callback when a status change for pid $pid (or any pid if
275 $pid is 0) has been received. More precisely: when the process 446 $pid is 0) has been received. More precisely: when the process
276 receives a SIGCHLD, EV will fetch the outstanding exit/wait status 447 receives a "SIGCHLD", EV will fetch the outstanding exit/wait status
277 for all changed/zombie children and call the callback. 448 for all changed/zombie children and call the callback.
278 449
279 Unlike all other callbacks, this callback will be called with an 450 It is valid (and fully supported) to install a child watcher after a
280 additional third argument which is the exit status. See the 451 child has exited but before the event loop has started its next
281 "waitpid" function for details. 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).
282 455
456 You can access both exit (or tracing) status and pid by using the
457 "rstatus" and "rpid" methods on the watcher object.
458
283 You can have as many pid watchers per pid as you want. 459 You can have as many pid watchers per pid as you want, they will all
460 be called.
284 461
285 The "child_ns" variant doesn't start (activate) the newly created 462 The "child_ns" variant doesn't start (activate) the newly created
286 watcher. 463 watcher.
287 464
288 $w->set ($pid) 465 $w->set ($pid)
289 Reconfigures the watcher, see the constructor above for details. Can 466 Reconfigures the watcher, see the constructor above for details. Can
290 be at any time. 467 be called at any time.
291 468
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
537 $w->set ($path, $interval)
538 Reconfigures the watcher, see the constructor above for details. Can
539 be called at any time.
540
541 $current_path = $w->path
542 $old_path = $w->path ($new_path)
543 Returns the previously set path and optionally set a new one.
544
545 $current_interval = $w->interval
546 $old_interval = $w->interval ($new_interval)
547 Returns the previously set interval and optionally set a new one.
548 Can be used to query the actual interval used.
549
550 IDLE WATCHERS - when you've got nothing better to do...
292 $w = EV::idle $callback 551 $w = EV::idle $callback
293 $w = EV::idle_ns $callback 552 $w = EV::idle_ns $callback
294 Call the callback when there are no pending io, timer/periodic, 553 Call the callback when there are no other pending watchers of the
295 signal or child events, i.e. when the process is idle. 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.
559
560 If you want a watcher that is only ever called when *no* other
561 events are outstanding you have to set the priority to "EV::MINPRI".
296 562
297 The process will not block as long as any idle watchers are active, 563 The process will not block as long as any idle watchers are active,
298 and they will be called repeatedly until stopped. 564 and they will be called repeatedly until stopped.
299 565
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
300 The "idle_ns" variant doesn't start (activate) the newly created 572 The "idle_ns" variant doesn't start (activate) the newly created
301 watcher. 573 watcher.
302 574
575 PREPARE WATCHERS - customise your event loop!
303 $w = EV::prepare $callback 576 $w = EV::prepare $callback
304 $w = EV::prepare_ns $callback 577 $w = EV::prepare_ns $callback
305 Call the callback just before the process would block. You can still 578 Call the callback just before the process would block. You can still
306 create/modify any watchers at this point. 579 create/modify any watchers at this point.
307 580
308 See the EV::check watcher, below, for explanations and an example. 581 See the EV::check watcher, below, for explanations and an example.
309 582
310 The "prepare_ns" variant doesn't start (activate) the newly created 583 The "prepare_ns" variant doesn't start (activate) the newly created
311 watcher. 584 watcher.
312 585
586 CHECK WATCHERS - customise your event loop even more!
313 $w = EV::check $callback 587 $w = EV::check $callback
314 $w = EV::check_ns $callback 588 $w = EV::check_ns $callback
315 Call the callback just after the process wakes up again (after it 589 Call the callback just after the process wakes up again (after it
316 has gathered events), but before any other callbacks have been 590 has gathered events), but before any other callbacks have been
317 invoked. 591 invoked.
… …
328 # do nothing unless active 602 # do nothing unless active
329 $dispatcher->{_event_queue_h} 603 $dispatcher->{_event_queue_h}
330 or return; 604 or return;
331 605
332 # make the dispatcher handle any outstanding stuff 606 # make the dispatcher handle any outstanding stuff
607 ... not shown
333 608
334 # create an IO watcher for each and every socket 609 # create an I/O watcher for each and every socket
335 @snmp_watcher = ( 610 @snmp_watcher = (
336 (map { EV::io $_, EV::READ, sub { } } 611 (map { EV::io $_, EV::READ, sub { } }
337 keys %{ $dispatcher->{_descriptors} }), 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 { },
338 ); 617 );
339
340 # if there are any timeouts, also create a timer
341 push @snmp_watcher, EV::timer $event->[Net::SNMP::Dispatcher::_TIME] - EV::now, 0, sub { }
342 if $event->[Net::SNMP::Dispatcher::_ACTIVE];
343 }; 618 };
344 619
345 The callbacks are irrelevant, the only purpose of those watchers is 620 The callbacks are irrelevant (and are not even being called), the
346 to wake up the process as soon as one of those events occurs (socket 621 only purpose of those watchers is to wake up the process as soon as
347 readable, or timer timed out). The corresponding EV::check watcher 622 one of those events occurs (socket readable, or timer timed out).
348 will then clean up: 623 The corresponding EV::check watcher will then clean up:
349 624
350 our $snmp_check = EV::check sub { 625 our $snmp_check = EV::check sub {
351 # destroy all watchers 626 # destroy all watchers
352 @snmp_watcher = (); 627 @snmp_watcher = ();
353 628
354 # make the dispatcher handle any new stuff 629 # make the dispatcher handle any new stuff
630 ... not shown
355 }; 631 };
356 632
357 The callbacks of the created watchers will not be called as the 633 The callbacks of the created watchers will not be called as the
358 watchers are destroyed before this cna happen (remember EV::check 634 watchers are destroyed before this cna happen (remember EV::check
359 gets called first). 635 gets called first).
360 636
361 The "check_ns" variant doesn't start (activate) the newly created 637 The "check_ns" variant doesn't start (activate) the newly created
362 watcher. 638 watcher.
363 639
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
364THREADS 671THREADS
365 Threads are not supported by this in any way. Perl pseudo-threads is 672 Threads are not supported by this module in any way. Perl pseudo-threads
366 evil stuff and must die. 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.
367 692
368SEE ALSO 693SEE ALSO
369 L<EV::DNS>, L<EV::AnyEvent>. 694 EV::ADNS (asynchronous dns), Glib::EV (makes Glib/Gtk2 use EV as event
695 loop), Coro::EV (efficient coroutines with EV).
370 696
371AUTHOR 697AUTHOR
372 Marc Lehmann <schmorp@schmorp.de> 698 Marc Lehmann <schmorp@schmorp.de>
373 http://home.schmorp.de/ 699 http://home.schmorp.de/
374 700

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