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Revision 1.33 by root, Fri Jul 17 14:49:33 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 { 44 # STAT CHANGES
11 warn "is called after 2s"; 45 my $w = EV::stat "/etc/passwd", 10, sub {
46 my ($w, $revents) = @_;
47 warn $w->path, " has changed somehow.\n";
12 }; 48 };
13 49
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
42
43 my $w = EV::child 666, sub {
44 my ($w, $revents, $status) = @_;
45 };
46
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://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.
55 128
56BASIC INTERFACE 129BASIC INTERFACE
57 $EV::DIED 130 $EV::DIED
58 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
59 callback throws an exception (with $@ containing thr error). The 132 callback throws an exception (with $@ containing the error). The
60 default prints an informative message and continues. 133 default prints an informative message and continues.
61 134
62 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.
63 147
64 $time = EV::time 148 $time = EV::time
65 Returns the current time in (fractional) seconds since the epoch. 149 Returns the current time in (fractional) seconds since the epoch.
66 150
67 $time = EV::now 151 $time = EV::now
152 $time = $loop->now
68 Returns the time the last event loop iteration has been started. 153 Returns the time the last event loop iteration has been started.
69 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
70 to it is usually faster then calling EV::time. 155 to it is usually faster then calling EV::time.
71 156
72 $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 = $loop->backend
73 Returns an integer describing the backend used by libev 196 Returns an integer describing the backend used by libev
74 (EV::METHOD_SELECT or EV::METHOD_EPOLL). 197 (EV::BACKEND_SELECT or EV::BACKEND_EPOLL).
75 198
76 EV::loop [$flags] 199 EV::loop [$flags]
200 $loop->loop ([$flags])
77 Begin checking for events and calling callbacks. It returns when a 201 Begin checking for events and calling callbacks. It returns when a
78 callback calls EV::loop_done. 202 callback calls EV::unloop.
79 203
80 The $flags argument can be one of the following: 204 The $flags argument can be one of the following:
81 205
82 0 as above 206 0 as above
83 EV::LOOP_ONESHOT block at most once (wait, but do not loop) 207 EV::LOOP_ONESHOT block at most once (wait, but do not loop)
84 EV::LOOP_NONBLOCK do not block at all (fetch/handle events but do not wait) 208 EV::LOOP_NONBLOCK do not block at all (fetch/handle events but do not wait)
85 209
86 EV::loop_done [$how] 210 EV::unloop [$how]
211 $loop->unloop ([$how])
87 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,
88 innermost call to EV::loop return. 213 makes the innermost call to EV::loop return.
89 214
90 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
91 as fast as possible. 216 EV::loop will return as fast as possible.
92 217
93 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
94 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
95 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,
96 you would create an EV::io watcher for that: 279 you would create an EV::io watcher for that:
97 280
98 my $watcher = EV::io *STDIN, EV::READ, sub { 281 my $watcher = EV::io *STDIN, EV::READ, sub {
99 my ($watcher, $revents) = @_; 282 my ($watcher, $revents) = @_;
100 warn "yeah, STDIN should not be readable without blocking!\n" 283 warn "yeah, STDIN should now be readable without blocking!\n"
101 }; 284 };
102 285
103 All watchers can be active (waiting for events) or inactive (paused). 286 All watchers can be active (waiting for events) or inactive (paused).
104 Only active watchers will have their callbacks invoked. All callbacks 287 Only active watchers will have their callbacks invoked. All callbacks
105 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
106 received events. 289 received events.
107 290
108 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
109 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
110 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,
111 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
112 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
113 (which uses EV::TIMEOUT). 296 (which uses EV::TIMEOUT).
114 297
115 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
116 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
117 its name, e.g. EV::io has a non-starting variant EV::io_ns and so on. 300 its name, e.g. EV::io has a non-starting variant EV::io_ns and so on.
118 301
119 Please note that a watcher will automatically be stopped when the 302 Please note that a watcher will automatically be stopped when the
120 watcher object is returned, so you *need* to keep the watcher objects 303 watcher object is destroyed, so you *need* to keep the watcher objects
121 returned by the constructors. 304 returned by the constructors.
122 305
123 WATCHER TYPES 306 Also, all methods changing some aspect of a watcher (->set, ->priority,
124 Now lets move to the existing watcher types and asociated methods. 307 ->fh and so on) automatically stop and start it again if it is active,
308 which means pending events get lost.
125 309
126 The following methods are available for all watchers. Then followes a 310 COMMON WATCHER METHODS
127 description of each watcher constructor (EV::io, EV::timer, 311 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).
130 312
131 $w->start 313 $w->start
132 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
133 already active watcher. By default, all watchers start out in the 315 already active watcher. By default, all watchers start out in the
134 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
135 stopped watchers). 317 stopped watchers).
136 318
137 $w->stop 319 $w->stop
138 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
139 (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
140 callback invocation), regardless of wether the watcher was active or 322 callback invocation), regardless of whether the watcher was active
141 not. 323 or not.
142 324
143 $bool = $w->is_active 325 $bool = $w->is_active
144 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!");
145 337
146 $current_cb = $w->cb 338 $current_cb = $w->cb
147 $old_cb = $w->cb ($new_cb) 339 $old_cb = $w->cb ($new_cb)
148 Queries the callback on the watcher and optionally changes it. You 340 Queries the callback on the watcher and optionally changes it. You
149 cna do this at any time. 341 can do this at any time without the watcher restarting.
150 342
343 $current_priority = $w->priority
344 $old_priority = $w->priority ($new_priority)
345 Queries the priority on the watcher and optionally changes it.
346 Pending watchers with higher priority will be invoked first. The
347 valid range of priorities lies between EV::MAXPRI (default 2) and
348 EV::MINPRI (default -2). If the priority is outside this range it
349 will automatically be normalised to the nearest valid priority.
350
351 The default priority of any newly-created watcher is 0.
352
353 Note that the priority semantics have not yet been fleshed out and
354 are subject to almost certain change.
355
151 $w->trigger ($revents) 356 $w->invoke ($revents)
152 Call the callback *now* with the given event mask. 357 Call the callback *now* with the given event mask.
153 358
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 convinient 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?
154 $w = EV::io $fileno_or_fh, $eventmask, $callback 405 $w = EV::io $fileno_or_fh, $eventmask, $callback
155 $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)
156 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
157 when the events specified in $eventmask. 410 when at least one of events specified in $eventmask occurs.
158 411
159 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:
160 413
161 EV::READ wait until read() wouldn't block anymore 414 EV::READ wait until read() wouldn't block anymore
162 EV::WRITE wait until write() wouldn't block anymore 415 EV::WRITE wait until write() wouldn't block anymore
… …
174 427
175 $current_eventmask = $w->events 428 $current_eventmask = $w->events
176 $old_eventmask = $w->events ($new_eventmask) 429 $old_eventmask = $w->events ($new_eventmask)
177 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.
178 431
432 TIMER WATCHERS - relative and optionally repeating timeouts
179 $w = EV::timer $after, $repeat, $callback 433 $w = EV::timer $after, $repeat, $callback
180 $w = EV::timer_ns $after, $repeat, $callback 434 $w = EV::timer_ns $after, $repeat, $callback
181 Calls the callback after $after seconds. If $repeat is non-zero, the 435 $w = $loop->timer ($after, $repeat, $callback)
182 timer will be restarted (with the $repeat value as $after) after the 436 $w = $loop->timer_ns ($after, $repeat, $callback)
183 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.
184 440
185 This means that the callback would be called roughly after $after 441 This means that the callback would be called roughly after $after
186 seconds, and then every $repeat seconds. "Roughly" because the time 442 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 443 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. 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.
189 447
190 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
191 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
192 changes the system clock, the timer will nevertheless run (roughly) 450 changes the system clock, the timer will nevertheless run (roughly)
193 the same time. 451 the same time.
194 452
195 The "timer_ns" variant doesn't start (activate) the newly created 453 The "timer_ns" variant doesn't start (activate) the newly created
196 watcher. 454 watcher.
197 455
198 $w->set ($after, $repeat) 456 $w->set ($after, $repeat)
199 Reconfigures the watcher, see the constructor above for details. Can 457 Reconfigures the watcher, see the constructor above for details. Can
200 be at any time. 458 be called at any time.
201 459
202 $w->again 460 $w->again
203 Similar to the "start" method, but has special semantics for 461 Similar to the "start" method, but has special semantics for
204 repeating timers: 462 repeating timers:
205 463
464 If the timer is active and non-repeating, it will be stopped.
465
206 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
207 $repeat seconds after now. 467 $repeat seconds after now.
208 468
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. 469 If the timer is inactive and repeating, start it using the repeat
470 value.
212 471
213 Otherwise do nothing. 472 Otherwise do nothing.
214 473
215 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
216 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
217 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"
218 method on the timeout. 477 method on the timeout.
219 478
479 PERIODIC WATCHERS - to cron or not to cron?
220 $w = EV::periodic $at, $interval, $callback 480 $w = EV::periodic $at, $interval, $reschedule_cb, $callback
221 $w = EV::periodic_ns $at, $interval, $callback 481 $w = EV::periodic_ns $at, $interval, $reschedule_cb, $callback
222 Similar to EV::timer, but the time is given as an absolute point in 482 $w = $loop->periodic ($at, $interval, $reschedule_cb, $callback)
223 time ($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.
224 491
225 If the $interval is zero, then the callback will be called at the 492 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.
228 493
229 If the $interval is nonzero, then the watcher will always be 494 * absolute timer ($interval = $reschedule_cb = 0)
230 scheduled to time out at the next "$at + N * $interval" time.
231 495
232 This can be used to schedule a callback to run at very regular 496 This time simply fires at the wallclock time $at and doesn't
233 intervals, as long as the processing time is less then the interval 497 repeat. It will not adjust when a time jump occurs, that is, if
234 (otherwise obviously events will be skipped). 498 it is to be run at January 1st 2011 then it will run when the
499 system time reaches or surpasses this time.
235 500
501 * repeating interval timer ($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 $hourly = EV::periodic 0, 3600, 0, sub { print "once/hour\n" };
511
512 That doesn't mean there will always be 3600 seconds in between
513 triggers, but only that the the clalback will be called when the
514 system time shows a full hour (UTC).
515
236 Another way to think about it (for the mathematically inclined) is 516 Another way to think about it (for the mathematically inclined)
237 that EV::periodic will try to run the callback at the next possible 517 is that EV::periodic will try to run the callback in this mode
238 time where "$time = $at (mod $interval)", regardless of any time 518 at the next possible time where "$time = $at (mod $interval)",
239 jumps. 519 regardless of any time jumps.
240 520
241 This periodic timer is based on "wallclock time", that is, if the 521 * manual reschedule mode ($reschedule_cb = coderef)
242 clock changes ("ntp", "date -s" etc.), then the timer will 522
243 nevertheless run at the specified time. This means it will never 523 In this mode $interval and $at are both being ignored. Instead,
244 drift (it might jitter, but it will not drift). 524 each time the periodic watcher gets scheduled, the reschedule
525 callback ($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 };
245 555
246 The "periodic_ns" variant doesn't start (activate) the newly created 556 The "periodic_ns" variant doesn't start (activate) the newly created
247 watcher. 557 watcher.
248 558
249 $w->set ($at, $interval) 559 $w->set ($at, $interval, $reschedule_cb)
250 Reconfigures the watcher, see the constructor above for details. Can 560 Reconfigures the watcher, see the constructor above for details. Can
251 be at any time. 561 be called at any time.
252 562
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!
253 $w = EV::signal $signal, $callback 570 $w = EV::signal $signal, $callback
254 $w = EV::signal_ns $signal, $callback 571 $w = EV::signal_ns $signal, $callback
255 Call the callback when $signal is received (the signal can be 572 Call the callback when $signal is received (the signal can be
256 specified by number or by name, just as with kill or %SIG). 573 specified by number or by name, just as with "kill" or %SIG).
257 574
258 EV will grab the signal for the process (the kernel only allows one 575 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 576 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 577 watcher, and removes it again when you stop it. Perl does the same
261 when you add/remove callbacks to %SIG, so watch out. 578 when you add/remove callbacks to %SIG, so watch out.
… …
265 The "signal_ns" variant doesn't start (activate) the newly created 582 The "signal_ns" variant doesn't start (activate) the newly created
266 watcher. 583 watcher.
267 584
268 $w->set ($signal) 585 $w->set ($signal)
269 Reconfigures the watcher, see the constructor above for details. Can 586 Reconfigures the watcher, see the constructor above for details. Can
270 be at any time. 587 be called at any time.
271 588
589 $current_signum = $w->signal
590 $old_signum = $w->signal ($new_signal)
591 Returns the previously set signal (always as a number not name) and
592 optionally set a new one.
593
594 CHILD WATCHERS - watch out for process status changes
272 $w = EV::child $pid, $callback 595 $w = EV::child $pid, $trace, $callback
273 $w = EV::child_ns $pid, $callback 596 $w = EV::child_ns $pid, $trace, $callback
597 $w = $loop->child ($pid, $trace, $callback)
598 $w = $loop->child_ns ($pid, $trace, $callback)
274 Call the callback when a status change for pid $pid (or any pid if 599 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 600 $pid is 0) has been received (a status change happens when the
601 process terminates or is killed, or, when trace is true,
602 additionally when it is stopped or continued). More precisely: when
276 receives a SIGCHLD, EV will fetch the outstanding exit/wait status 603 the process receives a "SIGCHLD", EV will fetch the outstanding
277 for all changed/zombie children and call the callback. 604 exit/wait status for all changed/zombie children and call the
605 callback.
278 606
279 Unlike all other callbacks, this callback will be called with an 607 It is valid (and fully supported) to install a child watcher after a
280 additional third argument which is the exit status. See the 608 child has exited but before the event loop has started its next
281 "waitpid" function for details. 609 iteration (for example, first you "fork", then the new child process
610 might exit, and only then do you install a child watcher in the
611 parent for the new pid).
282 612
613 You can access both exit (or tracing) status and pid by using the
614 "rstatus" and "rpid" methods on the watcher object.
615
283 You can have as many pid watchers per pid as you want. 616 You can have as many pid watchers per pid as you want, they will all
617 be called.
284 618
285 The "child_ns" variant doesn't start (activate) the newly created 619 The "child_ns" variant doesn't start (activate) the newly created
286 watcher. 620 watcher.
287 621
288 $w->set ($pid) 622 $w->set ($pid, $trace)
289 Reconfigures the watcher, see the constructor above for details. Can 623 Reconfigures the watcher, see the constructor above for details. Can
290 be at any time. 624 be called at any time.
291 625
626 $current_pid = $w->pid
627 Returns the previously set process id and optionally set a new one.
628
629 $exit_status = $w->rstatus
630 Return the exit/wait status (as returned by waitpid, see the waitpid
631 entry in perlfunc).
632
633 $pid = $w->rpid
634 Return the pid of the awaited child (useful when you have installed
635 a watcher for all pids).
636
637 STAT WATCHERS - did the file attributes just change?
638 $w = EV::stat $path, $interval, $callback
639 $w = EV::stat_ns $path, $interval, $callback
640 $w = $loop->stat ($path, $interval, $callback)
641 $w = $loop->stat_ns ($path, $interval, $callback)
642 Call the callback when a file status change has been detected on
643 $path. The $path does not need to exist, changing from "path exists"
644 to "path does not exist" is a status change like any other.
645
646 The $interval is a recommended polling interval for systems where
647 OS-supported change notifications don't exist or are not supported.
648 If you use 0 then an unspecified default is used (which is highly
649 recommended!), which is to be expected to be around five seconds
650 usually.
651
652 This watcher type is not meant for massive numbers of stat watchers,
653 as even with OS-supported change notifications, this can be
654 resource-intensive.
655
656 The "stat_ns" variant doesn't start (activate) the newly created
657 watcher.
658
659 ... = $w->stat
660 This call is very similar to the perl "stat" built-in: It stats
661 (using "lstat") the path specified in the watcher and sets perls
662 stat cache (as well as EV's idea of the current stat values) to the
663 values found.
664
665 In scalar context, a boolean is return indicating success or failure
666 of the stat. In list context, the same 13-value list as with stat is
667 returned (except that the blksize and blocks fields are not
668 reliable).
669
670 In the case of an error, errno is set to "ENOENT" (regardless of the
671 actual error value) and the "nlink" value is forced to zero (if the
672 stat was successful then nlink is guaranteed to be non-zero).
673
674 See also the next two entries for more info.
675
676 ... = $w->attr
677 Just like "$w->stat", but without the initial stat'ing: this returns
678 the values most recently detected by EV. See the next entry for more
679 info.
680
681 ... = $w->prev
682 Just like "$w->stat", but without the initial stat'ing: this returns
683 the previous set of values, before the change.
684
685 That is, when the watcher callback is invoked, "$w->prev" will be
686 set to the values found *before* a change was detected, while
687 "$w->attr" returns the values found leading to the change detection.
688 The difference (if any) between "prev" and "attr" is what triggered
689 the callback.
690
691 If you did something to the filesystem object and do not want to
692 trigger yet another change, you can call "stat" to update EV's idea
693 of what the current attributes are.
694
695 $w->set ($path, $interval)
696 Reconfigures the watcher, see the constructor above for details. Can
697 be called at any time.
698
699 $current_path = $w->path
700 $old_path = $w->path ($new_path)
701 Returns the previously set path and optionally set a new one.
702
703 $current_interval = $w->interval
704 $old_interval = $w->interval ($new_interval)
705 Returns the previously set interval and optionally set a new one.
706 Can be used to query the actual interval used.
707
708 IDLE WATCHERS - when you've got nothing better to do...
292 $w = EV::idle $callback 709 $w = EV::idle $callback
293 $w = EV::idle_ns $callback 710 $w = EV::idle_ns $callback
711 $w = $loop->idle ($callback)
712 $w = $loop->idle_ns ($callback)
294 Call the callback when there are no pending io, timer/periodic, 713 Call the callback when there are no other pending watchers of the
295 signal or child events, i.e. when the process is idle. 714 same or higher priority (excluding check, prepare and other idle
715 watchers of the same or lower priority, of course). They are called
716 idle watchers because when the watcher is the highest priority
717 pending event in the process, the process is considered to be idle
718 at that priority.
719
720 If you want a watcher that is only ever called when *no* other
721 events are outstanding you have to set the priority to "EV::MINPRI".
296 722
297 The process will not block as long as any idle watchers are active, 723 The process will not block as long as any idle watchers are active,
298 and they will be called repeatedly until stopped. 724 and they will be called repeatedly until stopped.
299 725
726 For example, if you have idle watchers at priority 0 and 1, and an
727 I/O watcher at priority 0, then the idle watcher at priority 1 and
728 the I/O watcher will always run when ready. Only when the idle
729 watcher at priority 1 is stopped and the I/O watcher at priority 0
730 is not pending with the 0-priority idle watcher be invoked.
731
300 The "idle_ns" variant doesn't start (activate) the newly created 732 The "idle_ns" variant doesn't start (activate) the newly created
301 watcher. 733 watcher.
302 734
735 PREPARE WATCHERS - customise your event loop!
303 $w = EV::prepare $callback 736 $w = EV::prepare $callback
304 $w = EV::prepare_ns $callback 737 $w = EV::prepare_ns $callback
738 $w = $loop->prepare ($callback)
739 $w = $loop->prepare_ns ($callback)
305 Call the callback just before the process would block. You can still 740 Call the callback just before the process would block. You can still
306 create/modify any watchers at this point. 741 create/modify any watchers at this point.
307 742
308 See the EV::check watcher, below, for explanations and an example. 743 See the EV::check watcher, below, for explanations and an example.
309 744
310 The "prepare_ns" variant doesn't start (activate) the newly created 745 The "prepare_ns" variant doesn't start (activate) the newly created
311 watcher. 746 watcher.
312 747
748 CHECK WATCHERS - customise your event loop even more!
313 $w = EV::check $callback 749 $w = EV::check $callback
314 $w = EV::check_ns $callback 750 $w = EV::check_ns $callback
751 $w = $loop->check ($callback)
752 $w = $loop->check_ns ($callback)
315 Call the callback just after the process wakes up again (after it 753 Call the callback just after the process wakes up again (after it
316 has gathered events), but before any other callbacks have been 754 has gathered events), but before any other callbacks have been
317 invoked. 755 invoked.
318 756
319 This is used to integrate other event-based software into the EV 757 This is used to integrate other event-based software into the EV
… …
328 # do nothing unless active 766 # do nothing unless active
329 $dispatcher->{_event_queue_h} 767 $dispatcher->{_event_queue_h}
330 or return; 768 or return;
331 769
332 # make the dispatcher handle any outstanding stuff 770 # make the dispatcher handle any outstanding stuff
771 ... not shown
333 772
334 # create an IO watcher for each and every socket 773 # create an I/O watcher for each and every socket
335 @snmp_watcher = ( 774 @snmp_watcher = (
336 (map { EV::io $_, EV::READ, sub { } } 775 (map { EV::io $_, EV::READ, sub { } }
337 keys %{ $dispatcher->{_descriptors} }), 776 keys %{ $dispatcher->{_descriptors} }),
777
778 EV::timer +($event->[Net::SNMP::Dispatcher::_ACTIVE]
779 ? $event->[Net::SNMP::Dispatcher::_TIME] - EV::now : 0),
780 0, sub { },
338 ); 781 );
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 }; 782 };
344 783
345 The callbacks are irrelevant, the only purpose of those watchers is 784 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 785 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 786 one of those events occurs (socket readable, or timer timed out).
348 will then clean up: 787 The corresponding EV::check watcher will then clean up:
349 788
350 our $snmp_check = EV::check sub { 789 our $snmp_check = EV::check sub {
351 # destroy all watchers 790 # destroy all watchers
352 @snmp_watcher = (); 791 @snmp_watcher = ();
353 792
354 # make the dispatcher handle any new stuff 793 # make the dispatcher handle any new stuff
794 ... not shown
355 }; 795 };
356 796
357 The callbacks of the created watchers will not be called as the 797 The callbacks of the created watchers will not be called as the
358 watchers are destroyed before this cna happen (remember EV::check 798 watchers are destroyed before this can happen (remember EV::check
359 gets called first). 799 gets called first).
360 800
361 The "check_ns" variant doesn't start (activate) the newly created 801 The "check_ns" variant doesn't start (activate) the newly created
362 watcher. 802 watcher.
363 803
804 FORK WATCHERS - the audacity to resume the event loop after a fork
805 Fork watchers are called when a "fork ()" was detected. The invocation
806 is done before the event loop blocks next and before "check" watchers
807 are being called, and only in the child after the fork.
808
809 $w = EV::fork $callback
810 $w = EV::fork_ns $callback
811 $w = $loop->fork ($callback)
812 $w = $loop->fork_ns ($callback)
813 Call the callback before the event loop is resumed in the child
814 process after a fork.
815
816 The "fork_ns" variant doesn't start (activate) the newly created
817 watcher.
818
819 EMBED WATCHERS - when one backend isn't enough...
820 This is a rather advanced watcher type that lets you embed one event
821 loop into another (currently only IO events are supported in the
822 embedded loop, other types of watchers might be handled in a delayed or
823 incorrect fashion and must not be used).
824
825 See the libev documentation at
826 <http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod#code_ev_embed_code
827 _when_one_backend_> (locally installed as EV::libev) for more details.
828
829 In short, this watcher is most useful on BSD systems without working
830 kqueue to still be able to handle a large number of sockets:
831
832 my $socket_loop;
833
834 # check wether we use SELECT or POLL _and_ KQUEUE is supported
835 if (
836 (EV::backend & (EV::BACKEND_POLL | EV::BACKEND_SELECT))
837 && (EV::supported_backends & EV::embeddable_backends & EV::BACKEND_KQUEUE)
838 ) {
839 # use kqueue for sockets
840 $socket_loop = new EV::Loop EV::BACKEND_KQUEUE | EV::FLAG_NOENV;
841 }
842
843 # use the default loop otherwise
844 $socket_loop ||= EV::default_loop;
845
846 $w = EV::embed $otherloop[, $callback]
847 $w = EV::embed_ns $otherloop[, $callback]
848 $w = $loop->embed ($otherloop[, $callback])
849 $w = $loop->embed_ns ($otherloop[, $callback])
850 Call the callback when the embedded event loop ($otherloop) has any
851 I/O activity. The $callback is optional: if it is missing, then the
852 embedded event loop will be managed automatically (which is
853 recommended), otherwise you have to invoke "sweep" yourself.
854
855 The "embed_ns" variant doesn't start (activate) the newly created
856 watcher.
857
858 ASYNC WATCHERS - how to wake up another event loop
859 Async watchers are provided by EV, but have little use in perl directly,
860 as perl neither supports threads running in parallel nor direct access
861 to signal handlers or other contexts where they could be of value.
862
863 It is, however, possible to use them from the XS level.
864
865 Please see the libev documentation for further details.
866
867 $w = EV::async $callback
868 $w = EV::async_ns $callback
869 $w->send
870 $bool = $w->async_pending
871
872PERL SIGNALS
873 While Perl signal handling (%SIG) is not affected by EV, the behaviour
874 with EV is as the same as any other C library: Perl-signals will only be
875 handled when Perl runs, which means your signal handler might be invoked
876 only the next time an event callback is invoked.
877
878 The solution is to use EV signal watchers (see "EV::signal"), which will
879 ensure proper operations with regards to other event watchers.
880
881 If you cannot do this for whatever reason, you can also force a watcher
882 to be called on every event loop iteration by installing a "EV::check"
883 watcher:
884
885 my $async_check = EV::check sub { };
886
887 This ensures that perl gets into control for a short time to handle any
888 pending signals, and also ensures (slightly) slower overall operation.
889
364THREADS 890ITHREADS
365 Threads are not supported by this in any way. Perl pseudo-threads is 891 Ithreads are not supported by this module in any way. Perl
366 evil stuff and must die. 892 pseudo-threads is evil stuff and must die. Real threads as provided by
893 Coro are fully supported (and enhanced support is available via
894 Coro::EV).
895
896FORK
897 Most of the "improved" event delivering mechanisms of modern operating
898 systems have quite a few problems with fork(2) (to put it bluntly: it is
899 not supported and usually destructive). Libev makes it possible to work
900 around this by having a function that recreates the kernel state after
901 fork in the child.
902
903 On non-win32 platforms, this module requires the pthread_atfork
904 functionality to do this automatically for you. This function is quite
905 buggy on most BSDs, though, so YMMV. The overhead for this is quite
906 negligible, because everything the function currently does is set a flag
907 that is checked only when the event loop gets used the next time, so
908 when you do fork but not use EV, the overhead is minimal.
909
910 On win32, there is no notion of fork so all this doesn't apply, of
911 course.
367 912
368SEE ALSO 913SEE ALSO
369 L<EV::DNS>, L<EV::AnyEvent>. 914 EV::ADNS (asynchronous DNS), Glib::EV (makes Glib/Gtk2 use EV as event
915 loop), EV::Glib (embed Glib into EV), Coro::EV (efficient coroutines
916 with EV), Net::SNMP::EV (asynchronous SNMP), AnyEvent for event-loop
917 agnostic and portable event driven programming.
370 918
371AUTHOR 919AUTHOR
372 Marc Lehmann <schmorp@schmorp.de> 920 Marc Lehmann <schmorp@schmorp.de>
373 http://home.schmorp.de/ 921 http://home.schmorp.de/
374 922

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