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Revision 1.7 by root, Sat Nov 3 16:25:49 2007 UTC vs.
Revision 1.35 by root, Thu Dec 31 06:59:47 2009 UTC

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

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