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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, 1, sub { 14 my $w = EV::timer 2, 2, sub {
15 warn "is called roughly every 2s (repeat = 1)"; 15 warn "is called roughly every 2s (repeat = 2)";
16 }; 16 };
17 17
18 undef $w; # destroy event watcher again 18 undef $w; # destroy event watcher again
19 19
20 my $w = EV::periodic 0, 60, sub { 20 my $w = EV::periodic 0, 60, 0, sub {
21 warn "is called every minute, on the minute, exactly"; 21 warn "is called every minute, on the minute, exactly";
22 }; 22 };
23
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, $revents) = @_; # all callbacks get the watcher object and event mask 27 my ($w, $revents) = @_; # all callbacks receive the watcher and event mask
28 warn "stdin is readable, you entered: ", <STDIN>; 28 warn "stdin is readable, you entered: ", <STDIN>;
29 }; 29 };
30 30
31 # SIGNALS 31 # SIGNALS
32 32
33 my $w = EV::signal 'QUIT', sub { 33 my $w = EV::signal 'QUIT', sub {
34 warn "sigquit received\n"; 34 warn "sigquit received\n";
35 }; 35 };
36 36
37 # CHILD/PID STATUS CHANGES
38
37 my $w = EV::signal 3, sub { 39 my $w = EV::child 666, 0, sub {
38 warn "sigquit received (this is GNU/Linux, right?)\n"; 40 my ($w, $revents) = @_;
41 my $status = $w->rstatus;
39 }; 42 };
40 43
41 # CHILD/PID STATUS CHANGES 44 # STAT CHANGES
42 45 my $w = EV::stat "/etc/passwd", 10, sub {
43 my $w = EV::child 666, sub {
44 my ($w, $revents, $status) = @_; 46 my ($w, $revents) = @_;
47 warn $w->path, " has changed somehow.\n";
45 }; 48 };
46 49
47 # MAINLOOP 50 # MAINLOOP
48 EV::loop; # loop until EV::loop_done is called 51 EV::loop; # loop until EV::unloop is called or all watchers stop
49 EV::loop EV::LOOP_ONESHOT; # block until at least one event could be handled 52 EV::loop EV::LOOP_ONESHOT; # block until at least one event could be handled
50 EV::loop EV::LOOP_NONBLOCK; # try to handle same events, but do not block 53 EV::loop EV::LOOP_NONBLOCK; # try to handle same events, but do not block
51 54
52DESCRIPTION 55DESCRIPTION
53 This module provides an interface to libev 56 This module provides an interface to libev
54 (<http://software.schmorp.de/pkg/libev.html>). 57 (<http://software.schmorp.de/pkg/libev.html>). While the documentation
58 below is comprehensive, one might also consult the documentation of
59 libev itself (<http://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).
55 106
56BASIC INTERFACE 107BASIC INTERFACE
57 $EV::DIED 108 $EV::DIED
58 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
59 callback throws an exception (with $@ containing thr error). The 110 callback throws an exception (with $@ containing the error). The
60 default prints an informative message and continues. 111 default prints an informative message and continues.
61 112
62 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.
63 125
64 $time = EV::time 126 $time = EV::time
65 Returns the current time in (fractional) seconds since the epoch. 127 Returns the current time in (fractional) seconds since the epoch.
66 128
67 $time = EV::now 129 $time = EV::now
130 $time = $loop->now
68 Returns the time the last event loop iteration has been started. 131 Returns the time the last event loop iteration has been started.
69 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
70 to it is usually faster then calling EV::time. 133 to it is usually faster then calling EV::time.
71 134
72 $method = EV::ev_method 135 $backend = EV::backend
136 $backend = $loop->backend
73 Returns an integer describing the backend used by libev 137 Returns an integer describing the backend used by libev
74 (EV::METHOD_SELECT or EV::METHOD_EPOLL). 138 (EV::METHOD_SELECT or EV::METHOD_EPOLL).
75 139
76 EV::loop [$flags] 140 EV::loop [$flags]
141 $loop->loop ([$flags])
77 Begin checking for events and calling callbacks. It returns when a 142 Begin checking for events and calling callbacks. It returns when a
78 callback calls EV::loop_done. 143 callback calls EV::unloop.
79 144
80 The $flags argument can be one of the following: 145 The $flags argument can be one of the following:
81 146
82 0 as above 147 0 as above
83 EV::LOOP_ONESHOT block at most once (wait, but do not loop) 148 EV::LOOP_ONESHOT block at most once (wait, but do not loop)
84 EV::LOOP_NONBLOCK do not block at all (fetch/handle events but do not wait) 149 EV::LOOP_NONBLOCK do not block at all (fetch/handle events but do not wait)
85 150
86 EV::loop_done [$how] 151 EV::unloop [$how]
152 $loop->unloop ([$how])
87 When called with no arguments or an argument of 1, makes the 153 When called with no arguments or an argument of EV::UNLOOP_ONE,
88 innermost call to EV::loop return. 154 makes the innermost call to EV::loop return.
89 155
90 When called with an agrument of 2, all calls to EV::loop will return 156 When called with an argument of EV::UNLOOP_ALL, all calls to
91 as fast as possible. 157 EV::loop will return as fast as possible.
92 158
93 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
94 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
95 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,
96 you would create an EV::io watcher for that: 211 you would create an EV::io watcher for that:
97 212
98 my $watcher = EV::io *STDIN, EV::READ, sub { 213 my $watcher = EV::io *STDIN, EV::READ, sub {
99 my ($watcher, $revents) = @_; 214 my ($watcher, $revents) = @_;
100 warn "yeah, STDIN should not be readable without blocking!\n" 215 warn "yeah, STDIN should now be readable without blocking!\n"
101 }; 216 };
102 217
103 All watchers can be active (waiting for events) or inactive (paused). 218 All watchers can be active (waiting for events) or inactive (paused).
104 Only active watchers will have their callbacks invoked. All callbacks 219 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 220 will be called with at least two arguments: the watcher and a bitmask of
106 received events. 221 received events.
107 222
108 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
109 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
110 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,
111 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
112 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
113 (which uses EV::TIMEOUT). 228 (which uses EV::TIMEOUT).
114 229
115 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
116 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
117 its name, e.g. EV::io has a non-starting variant EV::io_ns and so on. 232 its name, e.g. EV::io has a non-starting variant EV::io_ns and so on.
118 233
119 Please note that a watcher will automatically be stopped when the 234 Please note that a watcher will automatically be stopped when the
120 watcher object is returned, so you *need* to keep the watcher objects 235 watcher object is destroyed, so you *need* to keep the watcher objects
121 returned by the constructors. 236 returned by the constructors.
122 237
123 WATCHER TYPES 238 Also, all methods changing some aspect of a watcher (->set, ->priority,
124 Now lets move to the existing watcher types and asociated methods. 239 ->fh and so on) automatically stop and start it again if it is active,
240 which means pending events get lost.
125 241
126 The following methods are available for all watchers. Then followes a 242 COMMON WATCHER METHODS
127 description of each watcher constructor (EV::io, EV::timer, 243 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).
130 244
131 $w->start 245 $w->start
132 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
133 already active watcher. By default, all watchers start out in the 247 already active watcher. By default, all watchers start out in the
134 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
135 stopped watchers). 249 stopped watchers).
136 250
137 $w->stop 251 $w->stop
138 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
139 (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
140 callback invocation), regardless of wether the watcher was active or 254 callback invocation), regardless of whether the watcher was active
141 not. 255 or not.
142 256
143 $bool = $w->is_active 257 $bool = $w->is_active
144 Returns true if the watcher is active, false otherwise. 258 Returns true if the watcher is active, false otherwise.
259
260 $current_data = $w->data
261 $old_data = $w->data ($new_data)
262 Queries a freely usable data scalar on the watcher and optionally
263 changes it. This is a way to associate custom data with a watcher:
264
265 my $w = EV::timer 60, 0, sub {
266 warn $_[0]->data;
267 };
268 $w->data ("print me!");
145 269
146 $current_cb = $w->cb 270 $current_cb = $w->cb
147 $old_cb = $w->cb ($new_cb) 271 $old_cb = $w->cb ($new_cb)
148 Queries the callback on the watcher and optionally changes it. You 272 Queries the callback on the watcher and optionally changes it. You
149 cna do this at any time. 273 can do this at any time without the watcher restarting.
150 274
275 $current_priority = $w->priority
276 $old_priority = $w->priority ($new_priority)
277 Queries the priority on the watcher and optionally changes it.
278 Pending watchers with higher priority will be invoked first. The
279 valid range of priorities lies between EV::MAXPRI (default 2) and
280 EV::MINPRI (default -2). If the priority is outside this range it
281 will automatically be normalised to the nearest valid priority.
282
283 The default priority of any newly-created watcher is 0.
284
285 Note that the priority semantics have not yet been fleshed out and
286 are subject to almost certain change.
287
151 $w->trigger ($revents) 288 $w->invoke ($revents)
152 Call the callback *now* with the given event mask. 289 Call the callback *now* with the given event mask.
153 290
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?
154 $w = EV::io $fileno_or_fh, $eventmask, $callback 337 $w = EV::io $fileno_or_fh, $eventmask, $callback
155 $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)
156 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
157 when the events specified in $eventmask. 342 when at least one of events specified in $eventmask occurs.
158 343
159 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:
160 345
161 EV::READ wait until read() wouldn't block anymore 346 EV::READ wait until read() wouldn't block anymore
162 EV::WRITE wait until write() wouldn't block anymore 347 EV::WRITE wait until write() wouldn't block anymore
… …
174 359
175 $current_eventmask = $w->events 360 $current_eventmask = $w->events
176 $old_eventmask = $w->events ($new_eventmask) 361 $old_eventmask = $w->events ($new_eventmask)
177 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.
178 363
364 TIMER WATCHERS - relative and optionally repeating timeouts
179 $w = EV::timer $after, $repeat, $callback 365 $w = EV::timer $after, $repeat, $callback
180 $w = EV::timer_ns $after, $repeat, $callback 366 $w = EV::timer_ns $after, $repeat, $callback
181 Calls the callback after $after seconds. If $repeat is non-zero, the 367 $w = $loop->timer ($after, $repeat, $callback)
182 timer will be restarted (with the $repeat value as $after) after the 368 $w = $loop->timer_ns ($after, $repeat, $callback)
183 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.
184 372
185 This means that the callback would be called roughly after $after 373 This means that the callback would be called roughly after $after
186 seconds, and then every $repeat seconds. "Roughly" because the time 374 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 375 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. 376 event loop iteration, and might drift in other cases. If that isn't
377 acceptable, look at EV::periodic, which can provide long-term stable
378 timers.
189 379
190 The timer is based on a monotonic clock, that is if somebody is 380 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 381 sitting in front of the machine while the timer is running and
192 changes the system clock, the timer will nevertheless run (roughly) 382 changes the system clock, the timer will nevertheless run (roughly)
193 the same time. 383 the same time.
194 384
195 The "timer_ns" variant doesn't start (activate) the newly created 385 The "timer_ns" variant doesn't start (activate) the newly created
196 watcher. 386 watcher.
197 387
198 $w->set ($after, $repeat) 388 $w->set ($after, $repeat)
199 Reconfigures the watcher, see the constructor above for details. Can 389 Reconfigures the watcher, see the constructor above for details. Can
200 be at any time. 390 be called at any time.
201 391
202 $w->again 392 $w->again
203 Similar to the "start" method, but has special semantics for 393 Similar to the "start" method, but has special semantics for
204 repeating timers: 394 repeating timers:
205 395
396 If the timer is active and non-repeating, it will be stopped.
397
206 If the timer is active and repeating, reset the timeout to occur 398 If the timer is active and repeating, reset the timeout to occur
207 $repeat seconds after now. 399 $repeat seconds after now.
208 400
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. 401 If the timer is inactive and repeating, start it using the repeat
402 value.
212 403
213 Otherwise do nothing. 404 Otherwise do nothing.
214 405
215 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
216 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
217 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"
218 method on the timeout. 409 method on the timeout.
219 410
411 PERIODIC WATCHERS - to cron or not to cron?
220 $w = EV::periodic $at, $interval, $callback 412 $w = EV::periodic $at, $interval, $reschedule_cb, $callback
221 $w = EV::periodic_ns $at, $interval, $callback 413 $w = EV::periodic_ns $at, $interval, $reschedule_cb, $callback
222 Similar to EV::timer, but the time is given as an absolute point in 414 $w = $loop->periodic ($at, $interval, $reschedule_cb, $callback)
223 time ($at), plus an optional $interval. 415 $w = $loop->periodic_ns ($at, $interval, $reschedule_cb, $callback)
416 Similar to EV::timer, but is not based on relative timeouts but on
417 absolute times. Apart from creating "simple" timers that trigger
418 "at" the specified time, it can also be used for non-drifting
419 absolute timers and more complex, cron-like, setups that are not
420 adversely affected by time jumps (i.e. when the system clock is
421 changed by explicit date -s or other means such as ntpd). It is also
422 the most complex watcher type in EV.
224 423
225 If the $interval is zero, then the callback will be called at the 424 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.
228 425
229 If the $interval is nonzero, then the watcher will always be 426 * absolute timer ($interval = $reschedule_cb = 0)
230 scheduled to time out at the next "$at + N * $interval" time.
231 427
232 This can be used to schedule a callback to run at very regular 428 This time simply fires at the wallclock time $at and doesn't
233 intervals, as long as the processing time is less then the interval 429 repeat. It will not adjust when a time jump occurs, that is, if
234 (otherwise obviously events will be skipped). 430 it is to be run at January 1st 2011 then it will run when the
431 system time reaches or surpasses this time.
235 432
433 * repeating interval timer ($interval > 0, $reschedule_cb = 0)
434
435 In this mode the watcher will always be scheduled to time out at
436 the next "$at + N * $interval" time (for some integer N) and
437 then repeat, regardless of any time jumps.
438
439 This can be used to create timers that do not drift with respect
440 to system time:
441
442 my $hourly = EV::periodic 0, 3600, 0, sub { print "once/hour\n" };
443
444 That doesn't mean there will always be 3600 seconds in between
445 triggers, but only that the the clalback will be called when the
446 system time shows a full hour (UTC).
447
236 Another way to think about it (for the mathematically inclined) is 448 Another way to think about it (for the mathematically inclined)
237 that EV::periodic will try to run the callback at the next possible 449 is that EV::periodic will try to run the callback in this mode
238 time where "$time = $at (mod $interval)", regardless of any time 450 at the next possible time where "$time = $at (mod $interval)",
239 jumps. 451 regardless of any time jumps.
240 452
241 This periodic timer is based on "wallclock time", that is, if the 453 * manual reschedule mode ($reschedule_cb = coderef)
242 clock changes ("ntp", "date -s" etc.), then the timer will 454
243 nevertheless run at the specified time. This means it will never 455 In this mode $interval and $at are both being ignored. Instead,
244 drift (it might jitter, but it will not drift). 456 each time the periodic watcher gets scheduled, the reschedule
457 callback ($reschedule_cb) will be called with the watcher as
458 first, and the current time as second argument.
459
460 *This callback MUST NOT stop or destroy this or any other
461 periodic watcher, ever*. If you need to stop it, return 1e30 and
462 stop it afterwards.
463
464 It must return the next time to trigger, based on the passed
465 time value (that is, the lowest time value larger than to the
466 second argument). It will usually be called just before the
467 callback will be triggered, but might be called at other times,
468 too.
469
470 This can be used to create very complex timers, such as a timer
471 that triggers on each midnight, local time (actually 24 hours
472 after the last midnight, to keep the example simple. If you know
473 a way to do it correctly in about the same space (without
474 requiring elaborate modules), drop me a note :):
475
476 my $daily = EV::periodic 0, 0, sub {
477 my ($w, $now) = @_;
478
479 use Time::Local ();
480 my (undef, undef, undef, $d, $m, $y) = localtime $now;
481 86400 + Time::Local::timelocal 0, 0, 0, $d, $m, $y
482 }, sub {
483 print "it's midnight or likely shortly after, now\n";
484 };
245 485
246 The "periodic_ns" variant doesn't start (activate) the newly created 486 The "periodic_ns" variant doesn't start (activate) the newly created
247 watcher. 487 watcher.
248 488
249 $w->set ($at, $interval) 489 $w->set ($at, $interval, $reschedule_cb)
250 Reconfigures the watcher, see the constructor above for details. Can 490 Reconfigures the watcher, see the constructor above for details. Can
251 be at any time. 491 be called at any time.
252 492
493 $w->again
494 Simply stops and starts the watcher again.
495
496 $time = $w->at
497 Return the time that the watcher is expected to trigger next.
498
499 SIGNAL WATCHERS - signal me when a signal gets signalled!
253 $w = EV::signal $signal, $callback 500 $w = EV::signal $signal, $callback
254 $w = EV::signal_ns $signal, $callback 501 $w = EV::signal_ns $signal, $callback
255 Call the callback when $signal is received (the signal can be 502 Call the callback when $signal is received (the signal can be
256 specified by number or by name, just as with kill or %SIG). 503 specified by number or by name, just as with "kill" or %SIG).
257 504
258 EV will grab the signal for the process (the kernel only allows one 505 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 506 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 507 watcher, and removes it again when you stop it. Perl does the same
261 when you add/remove callbacks to %SIG, so watch out. 508 when you add/remove callbacks to %SIG, so watch out.
… …
265 The "signal_ns" variant doesn't start (activate) the newly created 512 The "signal_ns" variant doesn't start (activate) the newly created
266 watcher. 513 watcher.
267 514
268 $w->set ($signal) 515 $w->set ($signal)
269 Reconfigures the watcher, see the constructor above for details. Can 516 Reconfigures the watcher, see the constructor above for details. Can
270 be at any time. 517 be called at any time.
271 518
519 $current_signum = $w->signal
520 $old_signum = $w->signal ($new_signal)
521 Returns the previously set signal (always as a number not name) and
522 optionally set a new one.
523
524 CHILD WATCHERS - watch out for process status changes
272 $w = EV::child $pid, $callback 525 $w = EV::child $pid, $trace, $callback
273 $w = EV::child_ns $pid, $callback 526 $w = EV::child_ns $pid, $trace, $callback
527 $w = $loop->child ($pid, $trace, $callback)
528 $w = $loop->child_ns ($pid, $trace, $callback)
274 Call the callback when a status change for pid $pid (or any pid if 529 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 530 $pid is 0) has been received (a status change happens when the
531 process terminates or is killed, or, when trace is true,
532 additionally when it is stopped or continued). More precisely: when
276 receives a SIGCHLD, EV will fetch the outstanding exit/wait status 533 the process receives a "SIGCHLD", EV will fetch the outstanding
277 for all changed/zombie children and call the callback. 534 exit/wait status for all changed/zombie children and call the
535 callback.
278 536
279 Unlike all other callbacks, this callback will be called with an 537 It is valid (and fully supported) to install a child watcher after a
280 additional third argument which is the exit status. See the 538 child has exited but before the event loop has started its next
281 "waitpid" function for details. 539 iteration (for example, first you "fork", then the new child process
540 might exit, and only then do you install a child watcher in the
541 parent for the new pid).
282 542
543 You can access both exit (or tracing) status and pid by using the
544 "rstatus" and "rpid" methods on the watcher object.
545
283 You can have as many pid watchers per pid as you want. 546 You can have as many pid watchers per pid as you want, they will all
547 be called.
284 548
285 The "child_ns" variant doesn't start (activate) the newly created 549 The "child_ns" variant doesn't start (activate) the newly created
286 watcher. 550 watcher.
287 551
288 $w->set ($pid) 552 $w->set ($pid, $trace)
289 Reconfigures the watcher, see the constructor above for details. Can 553 Reconfigures the watcher, see the constructor above for details. Can
290 be at any time. 554 be called at any time.
291 555
556 $current_pid = $w->pid
557 Returns the previously set process id and optionally set a new one.
558
559 $exit_status = $w->rstatus
560 Return the exit/wait status (as returned by waitpid, see the waitpid
561 entry in perlfunc).
562
563 $pid = $w->rpid
564 Return the pid of the awaited child (useful when you have installed
565 a watcher for all pids).
566
567 STAT WATCHERS - did the file attributes just change?
568 $w = EV::stat $path, $interval, $callback
569 $w = EV::stat_ns $path, $interval, $callback
570 $w = $loop->stat ($path, $interval, $callback)
571 $w = $loop->stat_ns ($path, $interval, $callback)
572 Call the callback when a file status change has been detected on
573 $path. The $path does not need to exist, changing from "path exists"
574 to "path does not exist" is a status change like any other.
575
576 The $interval is a recommended polling interval for systems where
577 OS-supported change notifications don't exist or are not supported.
578 If you use 0 then an unspecified default is used (which is highly
579 recommended!), which is to be expected to be around five seconds
580 usually.
581
582 This watcher type is not meant for massive numbers of stat watchers,
583 as even with OS-supported change notifications, this can be
584 resource-intensive.
585
586 The "stat_ns" variant doesn't start (activate) the newly created
587 watcher.
588
589 ... = $w->stat
590 This call is very similar to the perl "stat" built-in: It stats
591 (using "lstat") the path specified in the watcher and sets perls
592 stat cache (as well as EV's idea of the current stat values) to the
593 values found.
594
595 In scalar context, a boolean is return indicating success or failure
596 of the stat. In list context, the same 13-value list as with stat is
597 returned (except that the blksize and blocks fields are not
598 reliable).
599
600 In the case of an error, errno is set to "ENOENT" (regardless of the
601 actual error value) and the "nlink" value is forced to zero (if the
602 stat was successful then nlink is guaranteed to be non-zero).
603
604 See also the next two entries for more info.
605
606 ... = $w->attr
607 Just like "$w->stat", but without the initial stat'ing: this returns
608 the values most recently detected by EV. See the next entry for more
609 info.
610
611 ... = $w->prev
612 Just like "$w->stat", but without the initial stat'ing: this returns
613 the previous set of values, before the change.
614
615 That is, when the watcher callback is invoked, "$w->prev" will be
616 set to the values found *before* a change was detected, while
617 "$w->attr" returns the values found leading to the change detection.
618 The difference (if any) between "prev" and "attr" is what triggered
619 the callback.
620
621 If you did something to the filesystem object and do not want to
622 trigger yet another change, you can call "stat" to update EV's idea
623 of what the current attributes are.
624
625 $w->set ($path, $interval)
626 Reconfigures the watcher, see the constructor above for details. Can
627 be called at any time.
628
629 $current_path = $w->path
630 $old_path = $w->path ($new_path)
631 Returns the previously set path and optionally set a new one.
632
633 $current_interval = $w->interval
634 $old_interval = $w->interval ($new_interval)
635 Returns the previously set interval and optionally set a new one.
636 Can be used to query the actual interval used.
637
638 IDLE WATCHERS - when you've got nothing better to do...
292 $w = EV::idle $callback 639 $w = EV::idle $callback
293 $w = EV::idle_ns $callback 640 $w = EV::idle_ns $callback
641 $w = $loop->idle ($callback)
642 $w = $loop->idle_ns ($callback)
294 Call the callback when there are no pending io, timer/periodic, 643 Call the callback when there are no other pending watchers of the
295 signal or child events, i.e. when the process is idle. 644 same or higher priority (excluding check, prepare and other idle
645 watchers of the same or lower priority, of course). They are called
646 idle watchers because when the watcher is the highest priority
647 pending event in the process, the process is considered to be idle
648 at that priority.
649
650 If you want a watcher that is only ever called when *no* other
651 events are outstanding you have to set the priority to "EV::MINPRI".
296 652
297 The process will not block as long as any idle watchers are active, 653 The process will not block as long as any idle watchers are active,
298 and they will be called repeatedly until stopped. 654 and they will be called repeatedly until stopped.
299 655
656 For example, if you have idle watchers at priority 0 and 1, and an
657 I/O watcher at priority 0, then the idle watcher at priority 1 and
658 the I/O watcher will always run when ready. Only when the idle
659 watcher at priority 1 is stopped and the I/O watcher at priority 0
660 is not pending with the 0-priority idle watcher be invoked.
661
300 The "idle_ns" variant doesn't start (activate) the newly created 662 The "idle_ns" variant doesn't start (activate) the newly created
301 watcher. 663 watcher.
302 664
665 PREPARE WATCHERS - customise your event loop!
303 $w = EV::prepare $callback 666 $w = EV::prepare $callback
304 $w = EV::prepare_ns $callback 667 $w = EV::prepare_ns $callback
668 $w = $loop->prepare ($callback)
669 $w = $loop->prepare_ns ($callback)
305 Call the callback just before the process would block. You can still 670 Call the callback just before the process would block. You can still
306 create/modify any watchers at this point. 671 create/modify any watchers at this point.
307 672
308 See the EV::check watcher, below, for explanations and an example. 673 See the EV::check watcher, below, for explanations and an example.
309 674
310 The "prepare_ns" variant doesn't start (activate) the newly created 675 The "prepare_ns" variant doesn't start (activate) the newly created
311 watcher. 676 watcher.
312 677
678 CHECK WATCHERS - customise your event loop even more!
313 $w = EV::check $callback 679 $w = EV::check $callback
314 $w = EV::check_ns $callback 680 $w = EV::check_ns $callback
681 $w = $loop->check ($callback)
682 $w = $loop->check_ns ($callback)
315 Call the callback just after the process wakes up again (after it 683 Call the callback just after the process wakes up again (after it
316 has gathered events), but before any other callbacks have been 684 has gathered events), but before any other callbacks have been
317 invoked. 685 invoked.
318 686
319 This is used to integrate other event-based software into the EV 687 This is used to integrate other event-based software into the EV
… …
328 # do nothing unless active 696 # do nothing unless active
329 $dispatcher->{_event_queue_h} 697 $dispatcher->{_event_queue_h}
330 or return; 698 or return;
331 699
332 # make the dispatcher handle any outstanding stuff 700 # make the dispatcher handle any outstanding stuff
701 ... not shown
333 702
334 # create an IO watcher for each and every socket 703 # create an I/O watcher for each and every socket
335 @snmp_watcher = ( 704 @snmp_watcher = (
336 (map { EV::io $_, EV::READ, sub { } } 705 (map { EV::io $_, EV::READ, sub { } }
337 keys %{ $dispatcher->{_descriptors} }), 706 keys %{ $dispatcher->{_descriptors} }),
707
708 EV::timer +($event->[Net::SNMP::Dispatcher::_ACTIVE]
709 ? $event->[Net::SNMP::Dispatcher::_TIME] - EV::now : 0),
710 0, sub { },
338 ); 711 );
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 }; 712 };
344 713
345 The callbacks are irrelevant, the only purpose of those watchers is 714 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 715 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 716 one of those events occurs (socket readable, or timer timed out).
348 will then clean up: 717 The corresponding EV::check watcher will then clean up:
349 718
350 our $snmp_check = EV::check sub { 719 our $snmp_check = EV::check sub {
351 # destroy all watchers 720 # destroy all watchers
352 @snmp_watcher = (); 721 @snmp_watcher = ();
353 722
354 # make the dispatcher handle any new stuff 723 # make the dispatcher handle any new stuff
724 ... not shown
355 }; 725 };
356 726
357 The callbacks of the created watchers will not be called as the 727 The callbacks of the created watchers will not be called as the
358 watchers are destroyed before this cna happen (remember EV::check 728 watchers are destroyed before this cna happen (remember EV::check
359 gets called first). 729 gets called first).
360 730
361 The "check_ns" variant doesn't start (activate) the newly created 731 The "check_ns" variant doesn't start (activate) the newly created
362 watcher. 732 watcher.
363 733
734 FORK WATCHERS - the audacity to resume the event loop after a fork
735 Fork watchers are called when a "fork ()" was detected. The invocation
736 is done before the event loop blocks next and before "check" watchers
737 are being called, and only in the child after the fork.
738
739 $w = EV::fork $callback
740 $w = EV::fork_ns $callback
741 $w = $loop->fork ($callback)
742 $w = $loop->fork_ns ($callback)
743 Call the callback before the event loop is resumed in the child
744 process after a fork.
745
746 The "fork_ns" variant doesn't start (activate) the newly created
747 watcher.
748
749 EMBED WATCHERS - when one backend isn't enough...
750 This is a rather advanced watcher type that lets you embed one event
751 loop into another (currently only IO events are supported in the
752 embedded loop, other types of watchers might be handled in a delayed or
753 incorrect fashion and must not be used).
754
755 See the libev documentation at
756 <http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod#code_ev_embed_code
757 _when_one_backend_> for more details.
758
759 In short, this watcher is most useful on BSD systems without working
760 kqueue to still be able to handle a large number of sockets:
761
762 my $socket_loop;
763
764 # check wether we use SELECT or POLL _and_ KQUEUE is supported
765 if (
766 (EV::backend & (EV::BACKEND_POLL | EV::BACKEND_SELECT))
767 && (EV::supported_backends & EV::embeddable_backends & EV::BACKEND_KQUEUE)
768 ) {
769 # use kqueue for sockets
770 $socket_loop = new EV::Loop EV::BACKEND_KQUEUE | EV::FLAG_NOENV;
771 }
772
773 # use the default loop otherwise
774 $socket_loop ||= EV::default_loop;
775
776 $w = EV::embed $otherloop, $callback
777 $w = EV::embed_ns $otherloop, $callback
778 $w = $loop->embed ($otherloop, $callback)
779 $w = $loop->embed_ns ($otherloop, $callback)
780 Call the callback when the embedded event loop ($otherloop) has any
781 I/O activity. The $callback should alwas be specified as "undef" in
782 this version of EV, which means the embedded event loop will be
783 managed automatically.
784
785 The "embed_ns" variant doesn't start (activate) the newly created
786 watcher.
787
788 ASYNC WATCHERS - how to wake up another event loop
789 Async watchers are provided by EV, but have little use in perl directly,
790 as perl neither supports threads nor direct access to signal handlers or
791 other contexts where they could be of value.
792
793 It is, however, possible to use them from the XS level.
794
795 Please see the libev documentation for further details.
796
797 $w = EV::async $callback
798 $w = EV::async_ns $callback
799 $w->send
800 $bool = $w->async_pending
801
802PERL SIGNALS
803 While Perl signal handling (%SIG) is not affected by EV, the behaviour
804 with EV is as the same as any other C library: Perl-signals will only be
805 handled when Perl runs, which means your signal handler might be invoked
806 only the next time an event callback is invoked.
807
808 The solution is to use EV signal watchers (see "EV::signal"), which will
809 ensure proper operations with regards to other event watchers.
810
811 If you cannot do this for whatever reason, you can also force a watcher
812 to be called on every event loop iteration by installing a "EV::check"
813 watcher:
814
815 my $async_check = EV::check sub { };
816
817 This ensures that perl gets into control for a short time to handle any
818 pending signals, and also ensures (slightly) slower overall operation.
819
364THREADS 820THREADS
365 Threads are not supported by this in any way. Perl pseudo-threads is 821 Threads are not supported by this module in any way. Perl pseudo-threads
366 evil stuff and must die. 822 is evil stuff and must die. As soon as Perl gains real threads I will
823 work on thread support for it.
824
825FORK
826 Most of the "improved" event delivering mechanisms of modern operating
827 systems have quite a few problems with fork(2) (to put it bluntly: it is
828 not supported and usually destructive). Libev makes it possible to work
829 around this by having a function that recreates the kernel state after
830 fork in the child.
831
832 On non-win32 platforms, this module requires the pthread_atfork
833 functionality to do this automatically for you. This function is quite
834 buggy on most BSDs, though, so YMMV. The overhead for this is quite
835 negligible, because everything the function currently does is set a flag
836 that is checked only when the event loop gets used the next time, so
837 when you do fork but not use EV, the overhead is minimal.
838
839 On win32, there is no notion of fork so all this doesn't apply, of
840 course.
367 841
368SEE ALSO 842SEE ALSO
369 L<EV::DNS>, L<EV::AnyEvent>. 843 EV::ADNS (asynchronous DNS), Glib::EV (makes Glib/Gtk2 use EV as event
844 loop), EV::Glib (embed Glib into EV), Coro::EV (efficient coroutines
845 with EV), Net::SNMP::EV (asynchronous SNMP), AnyEvent for event-loop
846 agnostic and portable event driven programming.
370 847
371AUTHOR 848AUTHOR
372 Marc Lehmann <schmorp@schmorp.de> 849 Marc Lehmann <schmorp@schmorp.de>
373 http://home.schmorp.de/ 850 http://home.schmorp.de/
374 851

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