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… …
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 7
8 # TIMERS 8 # TIMERS
9 9
10 my $w = EV::timer 2, 0, sub { 10 my $w = EV::timer 2, 0, sub {
11 warn "is called after 2s"; 11 warn "is called after 2s";
12 }; 12 };
13 13
14 my $w = EV::timer 2, 2, sub { 14 my $w = EV::timer 2, 2, sub {
15 warn "is called roughly every 2s (repeat = 2)"; 15 warn "is called roughly every 2s (repeat = 2)";
16 }; 16 };
17 17
18 undef $w; # destroy event watcher again 18 undef $w; # destroy event watcher again
19 19
20 my $w = EV::periodic 0, 60, 0, sub { 20 my $w = EV::periodic 0, 60, 0, sub {
21 warn "is called every minute, on the minute, exactly"; 21 warn "is called every minute, on the minute, exactly";
22 }; 22 };
23
24 # IO 23
25 24 # IO
25
26 my $w = EV::io *STDIN, EV::READ, sub { 26 my $w = EV::io *STDIN, EV::READ, sub {
27 my ($w, $revents) = @_; # all callbacks receive the watcher and event mask 27 my ($w, $revents) = @_; # all callbacks receive the watcher and event mask
28 warn "stdin is readable, you entered: ", <STDIN>; 28 warn "stdin is readable, you entered: ", <STDIN>;
29 }; 29 };
30 30
31 # SIGNALS 31 # SIGNALS
32 32
33 my $w = EV::signal 'QUIT', sub { 33 my $w = EV::signal 'QUIT', sub {
34 warn "sigquit received\n"; 34 warn "sigquit received\n";
35 }; 35 };
36 36
37 # CHILD/PID STATUS CHANGES 37 # CHILD/PID STATUS CHANGES
38 38
39 my $w = EV::child 666, sub { 39 my $w = EV::child 666, 0, sub {
40 my ($w, $revents) = @_; 40 my ($w, $revents) = @_;
41 my $status = $w->rstatus; 41 my $status = $w->rstatus;
42 }; 42 };
43 43
44 # STAT CHANGES
45 my $w = EV::stat "/etc/passwd", 10, sub {
46 my ($w, $revents) = @_;
47 warn $w->path, " has changed somehow.\n";
48 };
49
44 # MAINLOOP 50 # MAINLOOP
45 EV::loop; # loop until EV::unloop is called or all watchers stop 51 EV::loop; # loop until EV::unloop is called or all watchers stop
46 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
47 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
48 54
49DESCRIPTION 55DESCRIPTION
50 This module provides an interface to libev 56 This module provides an interface to libev
51 (<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>)
60 for more subtle details on watcher semantics or some discussion on the
61 available backends, or how to force a specific backend with
62 "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
71EVENT LOOPS
72 EV supports multiple event loops: There is a single "default event loop"
73 that can handle everything including signals and child watchers, and any
74 number of "dynamic event loops" that can use different backends (with
75 various limitations), but no child and signal watchers.
76
77 You do not have to do anything to create the default event loop: When
78 the module is loaded a suitable backend is selected on the premise of
79 selecting a working backend (which for example rules out kqueue on most
80 BSDs). Modules should, unless they have "special needs" always use the
81 default loop as this is fastest (perl-wise), best supported by other
82 modules (e.g. AnyEvent or Coro) and most portable event loop.
83
84 For specific programs you can create additional event loops dynamically.
85
86 $loop = new EV::loop [$flags]
87 Create a new event loop as per the specified flags. Please refer to
88 the "ev_loop_new ()" function description in the libev documentation
89 (<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod#GLOBAL_FUNCTI
90 ONS>) for more info.
91
92 The loop will automatically be destroyed when it is no longer
93 referenced by any watcher and the loop object goes out of scope.
94
95 Using "EV::FLAG_FORKCHECK" is recommended, as only the default event
96 loop is protected by this module.
97
98 $loop->loop_fork
99 Must be called after a fork in the child, before entering or
100 continuing the event loop. An alternative is to use
101 "EV::FLAG_FORKCHECK" which calls this fucntion automatically, at
102 some performance loss (refer to the libev documentation).
103
104 $loop = EV::default_loop [$flags]
105 Return the default loop (which is a singleton object).
52 106
53BASIC INTERFACE 107BASIC INTERFACE
54 $EV::DIED 108 $EV::DIED
55 Must contain a reference to a function that is called when a 109 Must contain a reference to a function that is called when a
56 callback throws an exception (with $@ containing thr error). The 110 callback throws an exception (with $@ containing the error). The
57 default prints an informative message and continues. 111 default prints an informative message and continues.
58 112
59 If this callback throws an exception it will be silently ignored. 113 If this callback throws an exception it will be silently ignored.
114
115 $flags = EV::supported_backends
116 $flags = EV::recommended_backends
117 $flags = EV::embeddable_backends
118 Returns the set (see "EV::BACKEND_*" flags) of backends supported by
119 this instance of EV, the set of recommended backends (supposed to be
120 good) for this platform and the set of embeddable backends (see
121 EMBED WATCHERS).
122
123 EV::sleep $seconds
124 Block the process for the given number of (fractional) seconds.
60 125
61 $time = EV::time 126 $time = EV::time
62 Returns the current time in (fractional) seconds since the epoch. 127 Returns the current time in (fractional) seconds since the epoch.
63 128
64 $time = EV::now 129 $time = EV::now
130 $time = $loop->now
65 Returns the time the last event loop iteration has been started. 131 Returns the time the last event loop iteration has been started.
66 This is the time that (relative) timers are based on, and refering 132 This is the time that (relative) timers are based on, and refering
67 to it is usually faster then calling EV::time. 133 to it is usually faster then calling EV::time.
68 134
69 $method = EV::ev_method 135 $backend = EV::backend
136 $backend = $loop->backend
70 Returns an integer describing the backend used by libev 137 Returns an integer describing the backend used by libev
71 (EV::METHOD_SELECT or EV::METHOD_EPOLL). 138 (EV::METHOD_SELECT or EV::METHOD_EPOLL).
72 139
73 EV::loop [$flags] 140 EV::loop [$flags]
141 $loop->loop ([$flags])
74 Begin checking for events and calling callbacks. It returns when a 142 Begin checking for events and calling callbacks. It returns when a
75 callback calls EV::unloop. 143 callback calls EV::unloop.
76 144
77 The $flags argument can be one of the following: 145 The $flags argument can be one of the following:
78 146
79 0 as above 147 0 as above
80 EV::LOOP_ONESHOT block at most once (wait, but do not loop) 148 EV::LOOP_ONESHOT block at most once (wait, but do not loop)
81 EV::LOOP_NONBLOCK do not block at all (fetch/handle events but do not wait) 149 EV::LOOP_NONBLOCK do not block at all (fetch/handle events but do not wait)
82 150
83 EV::unloop [$how] 151 EV::unloop [$how]
152 $loop->unloop ([$how])
84 When called with no arguments or an argument of EV::UNLOOP_ONE, 153 When called with no arguments or an argument of EV::UNLOOP_ONE,
85 makes the innermost call to EV::loop return. 154 makes the innermost call to EV::loop return.
86 155
87 When called with an argument of EV::UNLOOP_ALL, all calls to 156 When called with an argument of EV::UNLOOP_ALL, all calls to
88 EV::loop will return as fast as possible. 157 EV::loop will return as fast as possible.
89 158
90 WATCHER 159 $count = EV::loop_count
160 $count = $loop->loop_count
161 Return the number of times the event loop has polled for new events.
162 Sometiems useful as a generation counter.
163
164 EV::once $fh_or_undef, $events, $timeout, $cb->($revents)
165 $loop->once ($fh_or_undef, $events, $timeout, $cb->($revents))
166 This function rolls together an I/O and a timer watcher for a single
167 one-shot event without the need for managing a watcher object.
168
169 If $fh_or_undef is a filehandle or file descriptor, then $events
170 must be a bitset containing either "EV::READ", "EV::WRITE" or
171 "EV::READ | EV::WRITE", indicating the type of I/O event you want to
172 wait for. If you do not want to wait for some I/O event, specify
173 "undef" for $fh_or_undef and 0 for $events).
174
175 If timeout is "undef" or negative, then there will be no timeout.
176 Otherwise a EV::timer with this value will be started.
177
178 When an error occurs or either the timeout or I/O watcher triggers,
179 then the callback will be called with the received event set (in
180 general you can expect it to be a combination of "EV::ERROR",
181 "EV::READ", "EV::WRITE" and "EV::TIMEOUT").
182
183 EV::once doesn't return anything: the watchers stay active till
184 either of them triggers, then they will be stopped and freed, and
185 the callback invoked.
186
187 EV::feed_fd_event ($fd, $revents)
188 $loop->feed_fd_event ($fd, $revents)
189 Feed an event on a file descriptor into EV. EV will react to this
190 call as if the readyness notifications specified by $revents (a
191 combination of "EV::READ" and "EV::WRITE") happened on the file
192 descriptor $fd.
193
194 EV::feed_signal_event ($signal)
195 Feed a signal event into EV. EV will react to this call as if the
196 signal specified by $signal had occured.
197
198 EV::set_io_collect_interval $time
199 $loop->set_io_collect_interval ($time)
200 EV::set_timeout_collect_interval $time
201 $loop->set_timeout_collect_interval ($time)
202 These advanced functions set the minimum block interval when polling
203 for I/O events and the minimum wait interval for timer events. See
204 the libev documentation at
205 <http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod#FUNCTIONS_CONT
206 ROLLING_THE_EVENT_LOOP> for a more detailed discussion.
207
208WATCHER OBJECTS
91 A watcher is an object that gets created to record your interest in some 209 A watcher is an object that gets created to record your interest in some
92 event. For instance, if you want to wait for STDIN to become readable, 210 event. For instance, if you want to wait for STDIN to become readable,
93 you would create an EV::io watcher for that: 211 you would create an EV::io watcher for that:
94 212
95 my $watcher = EV::io *STDIN, EV::READ, sub { 213 my $watcher = EV::io *STDIN, EV::READ, sub {
96 my ($watcher, $revents) = @_; 214 my ($watcher, $revents) = @_;
97 warn "yeah, STDIN should not be readable without blocking!\n" 215 warn "yeah, STDIN should now be readable without blocking!\n"
98 }; 216 };
99 217
100 All watchers can be active (waiting for events) or inactive (paused). 218 All watchers can be active (waiting for events) or inactive (paused).
101 Only active watchers will have their callbacks invoked. All callbacks 219 Only active watchers will have their callbacks invoked. All callbacks
102 will be called with at least two arguments: the watcher and a bitmask of 220 will be called with at least two arguments: the watcher and a bitmask of
103 received events. 221 received events.
104 222
105 Each watcher type has its associated bit in revents, so you can use the 223 Each watcher type has its associated bit in revents, so you can use the
106 same callback for multiple watchers. The event mask is named after the 224 same callback for multiple watchers. The event mask is named after the
107 type, i..e. EV::child sets EV::CHILD, EV::prepare sets EV::PREPARE, 225 type, i..e. EV::child sets EV::CHILD, EV::prepare sets EV::PREPARE,
108 EV::periodic sets EV::PERIODIC and so on, with the exception of IO 226 EV::periodic sets EV::PERIODIC and so on, with the exception of I/O
109 events (which can set both EV::READ and EV::WRITE bits), and EV::timer 227 events (which can set both EV::READ and EV::WRITE bits), and EV::timer
110 (which uses EV::TIMEOUT). 228 (which uses EV::TIMEOUT).
111 229
112 In the rare case where one wants to create a watcher but not start it at 230 In the rare case where one wants to create a watcher but not start it at
113 the same time, each constructor has a variant with a trailing "_ns" in 231 the same time, each constructor has a variant with a trailing "_ns" in
… …
119 237
120 Also, all methods changing some aspect of a watcher (->set, ->priority, 238 Also, all methods changing some aspect of a watcher (->set, ->priority,
121 ->fh and so on) automatically stop and start it again if it is active, 239 ->fh and so on) automatically stop and start it again if it is active,
122 which means pending events get lost. 240 which means pending events get lost.
123 241
124 WATCHER TYPES 242 COMMON WATCHER METHODS
125 Now lets move to the existing watcher types and asociated methods. 243 This section lists methods common to all watchers.
126
127 The following methods are available for all watchers. Then followes a
128 description of each watcher constructor (EV::io, EV::timer,
129 EV::periodic, EV::signal, EV::child, EV::idle, EV::prepare and
130 EV::check), followed by any type-specific methods (if any).
131 244
132 $w->start 245 $w->start
133 Starts a watcher if it isn't active already. Does nothing to an 246 Starts a watcher if it isn't active already. Does nothing to an
134 already active watcher. By default, all watchers start out in the 247 already active watcher. By default, all watchers start out in the
135 active state (see the description of the "_ns" variants if you need 248 active state (see the description of the "_ns" variants if you need
136 stopped watchers). 249 stopped watchers).
137 250
138 $w->stop 251 $w->stop
139 Stop a watcher if it is active. Also clear any pending events 252 Stop a watcher if it is active. Also clear any pending events
140 (events that have been received but that didn't yet result in a 253 (events that have been received but that didn't yet result in a
141 callback invocation), regardless of wether the watcher was active or 254 callback invocation), regardless of whether the watcher was active
142 not. 255 or not.
143 256
144 $bool = $w->is_active 257 $bool = $w->is_active
145 Returns true if the watcher is active, false otherwise. 258 Returns true if the watcher is active, false otherwise.
146 259
147 $current_data = $w->data 260 $current_data = $w->data
… …
165 Pending watchers with higher priority will be invoked first. The 278 Pending watchers with higher priority will be invoked first. The
166 valid range of priorities lies between EV::MAXPRI (default 2) and 279 valid range of priorities lies between EV::MAXPRI (default 2) and
167 EV::MINPRI (default -2). If the priority is outside this range it 280 EV::MINPRI (default -2). If the priority is outside this range it
168 will automatically be normalised to the nearest valid priority. 281 will automatically be normalised to the nearest valid priority.
169 282
170 The default priority of any newly-created weatcher is 0. 283 The default priority of any newly-created watcher is 0.
171 284
285 Note that the priority semantics have not yet been fleshed out and
286 are subject to almost certain change.
287
172 $w->trigger ($revents) 288 $w->invoke ($revents)
173 Call the callback *now* with the given event mask. 289 Call the callback *now* with the given event mask.
174 290
291 $w->feed_event ($revents)
292 Feed some events on this watcher into EV. EV will react to this call
293 as if the watcher had received the given $revents mask.
294
295 $revents = $w->clear_pending
296 If the watcher is pending, this function clears its pending status
297 and returns its $revents bitset (as if its callback was invoked). If
298 the watcher isn't pending it does nothing and returns 0.
299
300 $previous_state = $w->keepalive ($bool)
301 Normally, "EV::loop" will return when there are no active watchers
302 (which is a "deadlock" because no progress can be made anymore).
303 This is convinient because it allows you to start your watchers (and
304 your jobs), call "EV::loop" once and when it returns you know that
305 all your jobs are finished (or they forgot to register some watchers
306 for their task :).
307
308 Sometimes, however, this gets in your way, for example when the
309 module that calls "EV::loop" (usually the main program) is not the
310 same module as a long-living watcher (for example a DNS client
311 module written by somebody else even). Then you might want any
312 outstanding requests to be handled, but you would not want to keep
313 "EV::loop" from returning just because you happen to have this
314 long-running UDP port watcher.
315
316 In this case you can clear the keepalive status, which means that
317 even though your watcher is active, it won't keep "EV::loop" from
318 returning.
319
320 The initial value for keepalive is true (enabled), and you cna
321 change it any time.
322
323 Example: Register an I/O watcher for some UDP socket but do not keep
324 the event loop from running just because of that watcher.
325
326 my $udp_socket = ...
327 my $udp_watcher = EV::io $udp_socket, EV::READ, sub { ... };
328 $1000udp_watcher->keepalive (0);
329
330 $loop = $w->loop
331 Return the loop that this watcher is attached to.
332
333WATCHER TYPES
334 Each of the following subsections describes a single watcher type.
335
336 I/O WATCHERS - is this file descriptor readable or writable?
175 $w = EV::io $fileno_or_fh, $eventmask, $callback 337 $w = EV::io $fileno_or_fh, $eventmask, $callback
176 $w = EV::io_ns $fileno_or_fh, $eventmask, $callback 338 $w = EV::io_ns $fileno_or_fh, $eventmask, $callback
339 $w = $loop->io ($fileno_or_fh, $eventmask, $callback)
340 $w = $loop->io_ns ($fileno_or_fh, $eventmask, $callback)
177 As long as the returned watcher object is alive, call the $callback 341 As long as the returned watcher object is alive, call the $callback
178 when the events specified in $eventmask. 342 when at least one of events specified in $eventmask occurs.
179 343
180 The $eventmask can be one or more of these constants ORed together: 344 The $eventmask can be one or more of these constants ORed together:
181 345
182 EV::READ wait until read() wouldn't block anymore 346 EV::READ wait until read() wouldn't block anymore
183 EV::WRITE wait until write() wouldn't block anymore 347 EV::WRITE wait until write() wouldn't block anymore
… …
195 359
196 $current_eventmask = $w->events 360 $current_eventmask = $w->events
197 $old_eventmask = $w->events ($new_eventmask) 361 $old_eventmask = $w->events ($new_eventmask)
198 Returns the previously set event mask and optionally set a new one. 362 Returns the previously set event mask and optionally set a new one.
199 363
364 TIMER WATCHERS - relative and optionally repeating timeouts
200 $w = EV::timer $after, $repeat, $callback 365 $w = EV::timer $after, $repeat, $callback
201 $w = EV::timer_ns $after, $repeat, $callback 366 $w = EV::timer_ns $after, $repeat, $callback
202 Calls the callback after $after seconds. If $repeat is non-zero, the 367 $w = $loop->timer ($after, $repeat, $callback)
203 timer will be restarted (with the $repeat value as $after) after the 368 $w = $loop->timer_ns ($after, $repeat, $callback)
204 callback returns. 369 Calls the callback after $after seconds (which may be fractional).
370 If $repeat is non-zero, the timer will be restarted (with the
371 $repeat value as $after) after the callback returns.
205 372
206 This means that the callback would be called roughly after $after 373 This means that the callback would be called roughly after $after
207 seconds, and then every $repeat seconds. The timer does his best not 374 seconds, and then every $repeat seconds. The timer does his best not
208 to drift, but it will not invoke the timer more often then once per 375 to drift, but it will not invoke the timer more often then once per
209 event loop iteration, and might drift in other cases. If that isn't 376 event loop iteration, and might drift in other cases. If that isn't
… …
218 The "timer_ns" variant doesn't start (activate) the newly created 385 The "timer_ns" variant doesn't start (activate) the newly created
219 watcher. 386 watcher.
220 387
221 $w->set ($after, $repeat) 388 $w->set ($after, $repeat)
222 Reconfigures the watcher, see the constructor above for details. Can 389 Reconfigures the watcher, see the constructor above for details. Can
223 be at any time. 390 be called at any time.
224 391
225 $w->again 392 $w->again
226 Similar to the "start" method, but has special semantics for 393 Similar to the "start" method, but has special semantics for
227 repeating timers: 394 repeating timers:
228 395
… …
239 This behaviour is useful when you have a timeout for some IO 406 This behaviour is useful when you have a timeout for some IO
240 operation. You create a timer object with the same value for $after 407 operation. You create a timer object with the same value for $after
241 and $repeat, and then, in the read/write watcher, run the "again" 408 and $repeat, and then, in the read/write watcher, run the "again"
242 method on the timeout. 409 method on the timeout.
243 410
411 PERIODIC WATCHERS - to cron or not to cron?
244 $w = EV::periodic $at, $interval, $reschedule_cb, $callback 412 $w = EV::periodic $at, $interval, $reschedule_cb, $callback
245 $w = EV::periodic_ns $at, $interval, $reschedule_cb, $callback 413 $w = EV::periodic_ns $at, $interval, $reschedule_cb, $callback
414 $w = $loop->periodic ($at, $interval, $reschedule_cb, $callback)
415 $w = $loop->periodic_ns ($at, $interval, $reschedule_cb, $callback)
246 Similar to EV::timer, but is not based on relative timeouts but on 416 Similar to EV::timer, but is not based on relative timeouts but on
247 absolute times. Apart from creating "simple" timers that trigger 417 absolute times. Apart from creating "simple" timers that trigger
248 "at" the specified time, it can also be used for non-drifting 418 "at" the specified time, it can also be used for non-drifting
249 absolute timers and more complex, cron-like, setups that are not 419 absolute timers and more complex, cron-like, setups that are not
250 adversely affected by time jumps (i.e. when the system clock is 420 adversely affected by time jumps (i.e. when the system clock is
251 changed by explicit date -s or other means such as ntpd). It is also 421 changed by explicit date -s or other means such as ntpd). It is also
252 the most complex watcher type in EV. 422 the most complex watcher type in EV.
253 423
254 It has three distinct "modes": 424 It has three distinct "modes":
255 425
256 * absolute timer ($interval = $reschedule_cb = 0) 426 * absolute timer ($interval = $reschedule_cb = 0)
427
257 This time simply fires at the wallclock time $at and doesn't 428 This time simply fires at the wallclock time $at and doesn't
258 repeat. It will not adjust when a time jump occurs, that is, if 429 repeat. It will not adjust when a time jump occurs, that is, if
259 it is to be run at January 1st 2011 then it will run when the 430 it is to be run at January 1st 2011 then it will run when the
260 system time reaches or surpasses this time. 431 system time reaches or surpasses this time.
261 432
262 * non-repeating interval timer ($interval > 0, $reschedule_cb = 0) 433 * repeating interval timer ($interval > 0, $reschedule_cb = 0)
434
263 In this mode the watcher will always be scheduled to time out at 435 In this mode the watcher will always be scheduled to time out at
264 the next "$at + N * $interval" time (for some integer N) and 436 the next "$at + N * $interval" time (for some integer N) and
265 then repeat, regardless of any time jumps. 437 then repeat, regardless of any time jumps.
266 438
267 This can be used to create timers that do not drift with respect 439 This can be used to create timers that do not drift with respect
… …
276 Another way to think about it (for the mathematically inclined) 448 Another way to think about it (for the mathematically inclined)
277 is that EV::periodic will try to run the callback in this mode 449 is that EV::periodic will try to run the callback in this mode
278 at the next possible time where "$time = $at (mod $interval)", 450 at the next possible time where "$time = $at (mod $interval)",
279 regardless of any time jumps. 451 regardless of any time jumps.
280 452
281 * manual reschedule mode ($reschedule_cb = coderef) 453 * manual reschedule mode ($reschedule_cb = coderef)
454
282 In this mode $interval and $at are both being ignored. Instead, 455 In this mode $interval and $at are both being ignored. Instead,
283 each time the periodic watcher gets scheduled, the reschedule 456 each time the periodic watcher gets scheduled, the reschedule
284 callback ($reschedule_cb) will be called with the watcher as 457 callback ($reschedule_cb) will be called with the watcher as
285 first, and the current time as second argument. 458 first, and the current time as second argument.
286 459
287 *This callback MUST NOT stop or destroy this or any other 460 *This callback MUST NOT stop or destroy this or any other
461 periodic watcher, ever, and MUST NOT call any event loop
288 periodic watcher, ever*. If you need to stop it, return 1e30 and 462 functions or methods*. If you need to stop it, return 1e30 and
289 stop it afterwards. 463 stop it afterwards. You may create and start a "EV::prepare"
464 watcher for this task.
290 465
291 It must return the next time to trigger, based on the passed 466 It must return the next time to trigger, based on the passed
292 time value (that is, the lowest time value larger than to the 467 time value (that is, the lowest time value larger than or equal
293 second argument). It will usually be called just before the 468 to to the second argument). It will usually be called just
294 callback will be triggered, but might be called at other times, 469 before the callback will be triggered, but might be called at
295 too. 470 other times, too.
296 471
297 This can be used to create very complex timers, such as a timer 472 This can be used to create very complex timers, such as a timer
298 that triggers on each midnight, local time (actually 24 hours 473 that triggers on each midnight, local time (actually 24 hours
299 after the last midnight, to keep the example simple. If you know 474 after the last midnight, to keep the example simple. If you know
300 a way to do it correctly in about the same space (without 475 a way to do it correctly in about the same space (without
… …
313 The "periodic_ns" variant doesn't start (activate) the newly created 488 The "periodic_ns" variant doesn't start (activate) the newly created
314 watcher. 489 watcher.
315 490
316 $w->set ($at, $interval, $reschedule_cb) 491 $w->set ($at, $interval, $reschedule_cb)
317 Reconfigures the watcher, see the constructor above for details. Can 492 Reconfigures the watcher, see the constructor above for details. Can
318 be at any time. 493 be called at any time.
319 494
320 $w->again 495 $w->again
321 Simply stops and starts the watcher again. 496 Simply stops and starts the watcher again.
322 497
498 $time = $w->at
499 Return the time that the watcher is expected to trigger next.
500
501 SIGNAL WATCHERS - signal me when a signal gets signalled!
323 $w = EV::signal $signal, $callback 502 $w = EV::signal $signal, $callback
324 $w = EV::signal_ns $signal, $callback 503 $w = EV::signal_ns $signal, $callback
325 Call the callback when $signal is received (the signal can be 504 Call the callback when $signal is received (the signal can be
326 specified by number or by name, just as with kill or %SIG). 505 specified by number or by name, just as with "kill" or %SIG).
327 506
328 EV will grab the signal for the process (the kernel only allows one 507 EV will grab the signal for the process (the kernel only allows one
329 component to receive a signal at a time) when you start a signal 508 component to receive a signal at a time) when you start a signal
330 watcher, and removes it again when you stop it. Perl does the same 509 watcher, and removes it again when you stop it. Perl does the same
331 when you add/remove callbacks to %SIG, so watch out. 510 when you add/remove callbacks to %SIG, so watch out.
… …
335 The "signal_ns" variant doesn't start (activate) the newly created 514 The "signal_ns" variant doesn't start (activate) the newly created
336 watcher. 515 watcher.
337 516
338 $w->set ($signal) 517 $w->set ($signal)
339 Reconfigures the watcher, see the constructor above for details. Can 518 Reconfigures the watcher, see the constructor above for details. Can
340 be at any time. 519 be called at any time.
341 520
342 $current_signum = $w->signal 521 $current_signum = $w->signal
343 $old_signum = $w->signal ($new_signal) 522 $old_signum = $w->signal ($new_signal)
344 Returns the previously set signal (always as a number not name) and 523 Returns the previously set signal (always as a number not name) and
345 optionally set a new one. 524 optionally set a new one.
346 525
526 CHILD WATCHERS - watch out for process status changes
347 $w = EV::child $pid, $callback 527 $w = EV::child $pid, $trace, $callback
348 $w = EV::child_ns $pid, $callback 528 $w = EV::child_ns $pid, $trace, $callback
529 $w = $loop->child ($pid, $trace, $callback)
530 $w = $loop->child_ns ($pid, $trace, $callback)
349 Call the callback when a status change for pid $pid (or any pid if 531 Call the callback when a status change for pid $pid (or any pid if
350 $pid is 0) has been received. More precisely: when the process 532 $pid is 0) has been received (a status change happens when the
533 process terminates or is killed, or, when trace is true,
534 additionally when it is stopped or continued). More precisely: when
351 receives a SIGCHLD, EV will fetch the outstanding exit/wait status 535 the process receives a "SIGCHLD", EV will fetch the outstanding
352 for all changed/zombie children and call the callback. 536 exit/wait status for all changed/zombie children and call the
537 callback.
353 538
354 You can access both status and pid by using the "rstatus" and "rpid" 539 It is valid (and fully supported) to install a child watcher after a
540 child has exited but before the event loop has started its next
541 iteration (for example, first you "fork", then the new child process
542 might exit, and only then do you install a child watcher in the
543 parent for the new pid).
544
545 You can access both exit (or tracing) status and pid by using the
355 methods on the watcher object. 546 "rstatus" and "rpid" methods on the watcher object.
356 547
357 You can have as many pid watchers per pid as you want. 548 You can have as many pid watchers per pid as you want, they will all
549 be called.
358 550
359 The "child_ns" variant doesn't start (activate) the newly created 551 The "child_ns" variant doesn't start (activate) the newly created
360 watcher. 552 watcher.
361 553
362 $w->set ($pid) 554 $w->set ($pid, $trace)
363 Reconfigures the watcher, see the constructor above for details. Can 555 Reconfigures the watcher, see the constructor above for details. Can
364 be at any time. 556 be called at any time.
365 557
366 $current_pid = $w->pid 558 $current_pid = $w->pid
367 $old_pid = $w->pid ($new_pid)
368 Returns the previously set process id and optionally set a new one. 559 Returns the previously set process id and optionally set a new one.
369 560
370 $exit_status = $w->rstatus 561 $exit_status = $w->rstatus
371 Return the exit/wait status (as returned by waitpid, see the waitpid 562 Return the exit/wait status (as returned by waitpid, see the waitpid
372 entry in perlfunc). 563 entry in perlfunc).
373 564
374 $pid = $w->rpid 565 $pid = $w->rpid
375 Return the pid of the awaited child (useful when you have installed 566 Return the pid of the awaited child (useful when you have installed
376 a watcher for all pids). 567 a watcher for all pids).
377 568
569 STAT WATCHERS - did the file attributes just change?
570 $w = EV::stat $path, $interval, $callback
571 $w = EV::stat_ns $path, $interval, $callback
572 $w = $loop->stat ($path, $interval, $callback)
573 $w = $loop->stat_ns ($path, $interval, $callback)
574 Call the callback when a file status change has been detected on
575 $path. The $path does not need to exist, changing from "path exists"
576 to "path does not exist" is a status change like any other.
577
578 The $interval is a recommended polling interval for systems where
579 OS-supported change notifications don't exist or are not supported.
580 If you use 0 then an unspecified default is used (which is highly
581 recommended!), which is to be expected to be around five seconds
582 usually.
583
584 This watcher type is not meant for massive numbers of stat watchers,
585 as even with OS-supported change notifications, this can be
586 resource-intensive.
587
588 The "stat_ns" variant doesn't start (activate) the newly created
589 watcher.
590
591 ... = $w->stat
592 This call is very similar to the perl "stat" built-in: It stats
593 (using "lstat") the path specified in the watcher and sets perls
594 stat cache (as well as EV's idea of the current stat values) to the
595 values found.
596
597 In scalar context, a boolean is return indicating success or failure
598 of the stat. In list context, the same 13-value list as with stat is
599 returned (except that the blksize and blocks fields are not
600 reliable).
601
602 In the case of an error, errno is set to "ENOENT" (regardless of the
603 actual error value) and the "nlink" value is forced to zero (if the
604 stat was successful then nlink is guaranteed to be non-zero).
605
606 See also the next two entries for more info.
607
608 ... = $w->attr
609 Just like "$w->stat", but without the initial stat'ing: this returns
610 the values most recently detected by EV. See the next entry for more
611 info.
612
613 ... = $w->prev
614 Just like "$w->stat", but without the initial stat'ing: this returns
615 the previous set of values, before the change.
616
617 That is, when the watcher callback is invoked, "$w->prev" will be
618 set to the values found *before* a change was detected, while
619 "$w->attr" returns the values found leading to the change detection.
620 The difference (if any) between "prev" and "attr" is what triggered
621 the callback.
622
623 If you did something to the filesystem object and do not want to
624 trigger yet another change, you can call "stat" to update EV's idea
625 of what the current attributes are.
626
627 $w->set ($path, $interval)
628 Reconfigures the watcher, see the constructor above for details. Can
629 be called at any time.
630
631 $current_path = $w->path
632 $old_path = $w->path ($new_path)
633 Returns the previously set path and optionally set a new one.
634
635 $current_interval = $w->interval
636 $old_interval = $w->interval ($new_interval)
637 Returns the previously set interval and optionally set a new one.
638 Can be used to query the actual interval used.
639
640 IDLE WATCHERS - when you've got nothing better to do...
378 $w = EV::idle $callback 641 $w = EV::idle $callback
379 $w = EV::idle_ns $callback 642 $w = EV::idle_ns $callback
643 $w = $loop->idle ($callback)
644 $w = $loop->idle_ns ($callback)
380 Call the callback when there are no pending io, timer/periodic, 645 Call the callback when there are no other pending watchers of the
381 signal or child events, i.e. when the process is idle. 646 same or higher priority (excluding check, prepare and other idle
647 watchers of the same or lower priority, of course). They are called
648 idle watchers because when the watcher is the highest priority
649 pending event in the process, the process is considered to be idle
650 at that priority.
651
652 If you want a watcher that is only ever called when *no* other
653 events are outstanding you have to set the priority to "EV::MINPRI".
382 654
383 The process will not block as long as any idle watchers are active, 655 The process will not block as long as any idle watchers are active,
384 and they will be called repeatedly until stopped. 656 and they will be called repeatedly until stopped.
385 657
658 For example, if you have idle watchers at priority 0 and 1, and an
659 I/O watcher at priority 0, then the idle watcher at priority 1 and
660 the I/O watcher will always run when ready. Only when the idle
661 watcher at priority 1 is stopped and the I/O watcher at priority 0
662 is not pending with the 0-priority idle watcher be invoked.
663
386 The "idle_ns" variant doesn't start (activate) the newly created 664 The "idle_ns" variant doesn't start (activate) the newly created
387 watcher. 665 watcher.
388 666
667 PREPARE WATCHERS - customise your event loop!
389 $w = EV::prepare $callback 668 $w = EV::prepare $callback
390 $w = EV::prepare_ns $callback 669 $w = EV::prepare_ns $callback
670 $w = $loop->prepare ($callback)
671 $w = $loop->prepare_ns ($callback)
391 Call the callback just before the process would block. You can still 672 Call the callback just before the process would block. You can still
392 create/modify any watchers at this point. 673 create/modify any watchers at this point.
393 674
394 See the EV::check watcher, below, for explanations and an example. 675 See the EV::check watcher, below, for explanations and an example.
395 676
396 The "prepare_ns" variant doesn't start (activate) the newly created 677 The "prepare_ns" variant doesn't start (activate) the newly created
397 watcher. 678 watcher.
398 679
680 CHECK WATCHERS - customise your event loop even more!
399 $w = EV::check $callback 681 $w = EV::check $callback
400 $w = EV::check_ns $callback 682 $w = EV::check_ns $callback
683 $w = $loop->check ($callback)
684 $w = $loop->check_ns ($callback)
401 Call the callback just after the process wakes up again (after it 685 Call the callback just after the process wakes up again (after it
402 has gathered events), but before any other callbacks have been 686 has gathered events), but before any other callbacks have been
403 invoked. 687 invoked.
404 688
405 This is used to integrate other event-based software into the EV 689 This is used to integrate other event-based software into the EV
… …
414 # do nothing unless active 698 # do nothing unless active
415 $dispatcher->{_event_queue_h} 699 $dispatcher->{_event_queue_h}
416 or return; 700 or return;
417 701
418 # make the dispatcher handle any outstanding stuff 702 # make the dispatcher handle any outstanding stuff
703 ... not shown
419 704
420 # create an IO watcher for each and every socket 705 # create an I/O watcher for each and every socket
421 @snmp_watcher = ( 706 @snmp_watcher = (
422 (map { EV::io $_, EV::READ, sub { } } 707 (map { EV::io $_, EV::READ, sub { } }
423 keys %{ $dispatcher->{_descriptors} }), 708 keys %{ $dispatcher->{_descriptors} }),
709
710 EV::timer +($event->[Net::SNMP::Dispatcher::_ACTIVE]
711 ? $event->[Net::SNMP::Dispatcher::_TIME] - EV::now : 0),
712 0, sub { },
424 ); 713 );
425
426 # if there are any timeouts, also create a timer
427 push @snmp_watcher, EV::timer $event->[Net::SNMP::Dispatcher::_TIME] - EV::now, 0, sub { }
428 if $event->[Net::SNMP::Dispatcher::_ACTIVE];
429 }; 714 };
430 715
431 The callbacks are irrelevant, the only purpose of those watchers is 716 The callbacks are irrelevant (and are not even being called), the
432 to wake up the process as soon as one of those events occurs (socket 717 only purpose of those watchers is to wake up the process as soon as
433 readable, or timer timed out). The corresponding EV::check watcher 718 one of those events occurs (socket readable, or timer timed out).
434 will then clean up: 719 The corresponding EV::check watcher will then clean up:
435 720
436 our $snmp_check = EV::check sub { 721 our $snmp_check = EV::check sub {
437 # destroy all watchers 722 # destroy all watchers
438 @snmp_watcher = (); 723 @snmp_watcher = ();
439 724
440 # make the dispatcher handle any new stuff 725 # make the dispatcher handle any new stuff
726 ... not shown
441 }; 727 };
442 728
443 The callbacks of the created watchers will not be called as the 729 The callbacks of the created watchers will not be called as the
444 watchers are destroyed before this cna happen (remember EV::check 730 watchers are destroyed before this cna happen (remember EV::check
445 gets called first). 731 gets called first).
446 732
447 The "check_ns" variant doesn't start (activate) the newly created 733 The "check_ns" variant doesn't start (activate) the newly created
448 watcher. 734 watcher.
449 735
736 FORK WATCHERS - the audacity to resume the event loop after a fork
737 Fork watchers are called when a "fork ()" was detected. The invocation
738 is done before the event loop blocks next and before "check" watchers
739 are being called, and only in the child after the fork.
740
741 $w = EV::fork $callback
742 $w = EV::fork_ns $callback
743 $w = $loop->fork ($callback)
744 $w = $loop->fork_ns ($callback)
745 Call the callback before the event loop is resumed in the child
746 process after a fork.
747
748 The "fork_ns" variant doesn't start (activate) the newly created
749 watcher.
750
751 EMBED WATCHERS - when one backend isn't enough...
752 This is a rather advanced watcher type that lets you embed one event
753 loop into another (currently only IO events are supported in the
754 embedded loop, other types of watchers might be handled in a delayed or
755 incorrect fashion and must not be used).
756
757 See the libev documentation at
758 <http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod#code_ev_embed_code
759 _when_one_backend_> for more details.
760
761 In short, this watcher is most useful on BSD systems without working
762 kqueue to still be able to handle a large number of sockets:
763
764 my $socket_loop;
765
766 # check wether we use SELECT or POLL _and_ KQUEUE is supported
767 if (
768 (EV::backend & (EV::BACKEND_POLL | EV::BACKEND_SELECT))
769 && (EV::supported_backends & EV::embeddable_backends & EV::BACKEND_KQUEUE)
770 ) {
771 # use kqueue for sockets
772 $socket_loop = new EV::Loop EV::BACKEND_KQUEUE | EV::FLAG_NOENV;
773 }
774
775 # use the default loop otherwise
776 $socket_loop ||= EV::default_loop;
777
778 $w = EV::embed $otherloop, $callback
779 $w = EV::embed_ns $otherloop, $callback
780 $w = $loop->embed ($otherloop, $callback)
781 $w = $loop->embed_ns ($otherloop, $callback)
782 Call the callback when the embedded event loop ($otherloop) has any
783 I/O activity. The $callback should alwas be specified as "undef" in
784 this version of EV, which means the embedded event loop will be
785 managed automatically.
786
787 The "embed_ns" variant doesn't start (activate) the newly created
788 watcher.
789
790 ASYNC WATCHERS - how to wake up another event loop
791 Async watchers are provided by EV, but have little use in perl directly,
792 as perl neither supports threads nor direct access to signal handlers or
793 other contexts where they could be of value.
794
795 It is, however, possible to use them from the XS level.
796
797 Please see the libev documentation for further details.
798
799 $w = EV::async $callback
800 $w = EV::async_ns $callback
801 $w->send
802 $bool = $w->async_pending
803
804PERL SIGNALS
805 While Perl signal handling (%SIG) is not affected by EV, the behaviour
806 with EV is as the same as any other C library: Perl-signals will only be
807 handled when Perl runs, which means your signal handler might be invoked
808 only the next time an event callback is invoked.
809
810 The solution is to use EV signal watchers (see "EV::signal"), which will
811 ensure proper operations with regards to other event watchers.
812
813 If you cannot do this for whatever reason, you can also force a watcher
814 to be called on every event loop iteration by installing a "EV::check"
815 watcher:
816
817 my $async_check = EV::check sub { };
818
819 This ensures that perl gets into control for a short time to handle any
820 pending signals, and also ensures (slightly) slower overall operation.
821
450THREADS 822THREADS
451 Threads are not supported by this in any way. Perl pseudo-threads is 823 Threads are not supported by this module in any way. Perl pseudo-threads
452 evil stuff and must die. 824 is evil stuff and must die. As soon as Perl gains real threads I will
825 work on thread support for it.
826
827FORK
828 Most of the "improved" event delivering mechanisms of modern operating
829 systems have quite a few problems with fork(2) (to put it bluntly: it is
830 not supported and usually destructive). Libev makes it possible to work
831 around this by having a function that recreates the kernel state after
832 fork in the child.
833
834 On non-win32 platforms, this module requires the pthread_atfork
835 functionality to do this automatically for you. This function is quite
836 buggy on most BSDs, though, so YMMV. The overhead for this is quite
837 negligible, because everything the function currently does is set a flag
838 that is checked only when the event loop gets used the next time, so
839 when you do fork but not use EV, the overhead is minimal.
840
841 On win32, there is no notion of fork so all this doesn't apply, of
842 course.
453 843
454SEE ALSO 844SEE ALSO
455 L<EV::DNS>, L<EV::AnyEvent>. 845 EV::ADNS (asynchronous DNS), Glib::EV (makes Glib/Gtk2 use EV as event
846 loop), EV::Glib (embed Glib into EV), Coro::EV (efficient coroutines
847 with EV), Net::SNMP::EV (asynchronous SNMP), AnyEvent for event-loop
848 agnostic and portable event driven programming.
456 849
457AUTHOR 850AUTHOR
458 Marc Lehmann <schmorp@schmorp.de> 851 Marc Lehmann <schmorp@schmorp.de>
459 http://home.schmorp.de/ 852 http://home.schmorp.de/
460 853

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