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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 function automatically, at
102 some performance loss (refer to the libev documentation).
103
104 $loop->loop_verify
105 Calls "ev_verify" to make internal consistency checks (for debugging
106 libev) and abort the program if any data structures wree found to be
107 corrupted.
108
109 $loop = EV::default_loop [$flags]
110 Return the default loop (which is a singleton object). Since this
111 module already creates the default loop with default flags,
112 specifying flags here will not have any effect unless you destroy
113 the default loop.
55 114
56BASIC INTERFACE 115BASIC INTERFACE
57 $EV::DIED 116 $EV::DIED
58 Must contain a reference to a function that is called when a 117 Must contain a reference to a function that is called when a
59 callback throws an exception (with $@ containing thr error). The 118 callback throws an exception (with $@ containing the error). The
60 default prints an informative message and continues. 119 default prints an informative message and continues.
61 120
62 If this callback throws an exception it will be silently ignored. 121 If this callback throws an exception it will be silently ignored.
122
123 $flags = EV::supported_backends
124 $flags = EV::recommended_backends
125 $flags = EV::embeddable_backends
126 Returns the set (see "EV::BACKEND_*" flags) of backends supported by
127 this instance of EV, the set of recommended backends (supposed to be
128 good) for this platform and the set of embeddable backends (see
129 EMBED WATCHERS).
130
131 EV::sleep $seconds
132 Block the process for the given number of (fractional) seconds.
63 133
64 $time = EV::time 134 $time = EV::time
65 Returns the current time in (fractional) seconds since the epoch. 135 Returns the current time in (fractional) seconds since the epoch.
66 136
67 $time = EV::now 137 $time = EV::now
138 $time = $loop->now
68 Returns the time the last event loop iteration has been started. 139 Returns the time the last event loop iteration has been started.
69 This is the time that (relative) timers are based on, and refering 140 This is the time that (relative) timers are based on, and refering
70 to it is usually faster then calling EV::time. 141 to it is usually faster then calling EV::time.
71 142
72 $method = EV::ev_method 143 $backend = EV::backend
144 $backend = $loop->backend
73 Returns an integer describing the backend used by libev 145 Returns an integer describing the backend used by libev
74 (EV::METHOD_SELECT or EV::METHOD_EPOLL). 146 (EV::METHOD_SELECT or EV::METHOD_EPOLL).
75 147
76 EV::loop [$flags] 148 EV::loop [$flags]
149 $loop->loop ([$flags])
77 Begin checking for events and calling callbacks. It returns when a 150 Begin checking for events and calling callbacks. It returns when a
78 callback calls EV::loop_done. 151 callback calls EV::unloop.
79 152
80 The $flags argument can be one of the following: 153 The $flags argument can be one of the following:
81 154
82 0 as above 155 0 as above
83 EV::LOOP_ONESHOT block at most once (wait, but do not loop) 156 EV::LOOP_ONESHOT block at most once (wait, but do not loop)
84 EV::LOOP_NONBLOCK do not block at all (fetch/handle events but do not wait) 157 EV::LOOP_NONBLOCK do not block at all (fetch/handle events but do not wait)
85 158
86 EV::loop_done [$how] 159 EV::unloop [$how]
160 $loop->unloop ([$how])
87 When called with no arguments or an argument of 1, makes the 161 When called with no arguments or an argument of EV::UNLOOP_ONE,
88 innermost call to EV::loop return. 162 makes the innermost call to EV::loop return.
89 163
90 When called with an agrument of 2, all calls to EV::loop will return 164 When called with an argument of EV::UNLOOP_ALL, all calls to
91 as fast as possible. 165 EV::loop will return as fast as possible.
92 166
93 WATCHER 167 $count = EV::loop_count
168 $count = $loop->loop_count
169 Return the number of times the event loop has polled for new events.
170 Sometiems useful as a generation counter.
171
172 EV::once $fh_or_undef, $events, $timeout, $cb->($revents)
173 $loop->once ($fh_or_undef, $events, $timeout, $cb->($revents))
174 This function rolls together an I/O and a timer watcher for a single
175 one-shot event without the need for managing a watcher object.
176
177 If $fh_or_undef is a filehandle or file descriptor, then $events
178 must be a bitset containing either "EV::READ", "EV::WRITE" or
179 "EV::READ | EV::WRITE", indicating the type of I/O event you want to
180 wait for. If you do not want to wait for some I/O event, specify
181 "undef" for $fh_or_undef and 0 for $events).
182
183 If timeout is "undef" or negative, then there will be no timeout.
184 Otherwise a EV::timer with this value will be started.
185
186 When an error occurs or either the timeout or I/O watcher triggers,
187 then the callback will be called with the received event set (in
188 general you can expect it to be a combination of "EV::ERROR",
189 "EV::READ", "EV::WRITE" and "EV::TIMEOUT").
190
191 EV::once doesn't return anything: the watchers stay active till
192 either of them triggers, then they will be stopped and freed, and
193 the callback invoked.
194
195 EV::feed_fd_event ($fd, $revents)
196 $loop->feed_fd_event ($fd, $revents)
197 Feed an event on a file descriptor into EV. EV will react to this
198 call as if the readyness notifications specified by $revents (a
199 combination of "EV::READ" and "EV::WRITE") happened on the file
200 descriptor $fd.
201
202 EV::feed_signal_event ($signal)
203 Feed a signal event into EV. EV will react to this call as if the
204 signal specified by $signal had occured.
205
206 EV::set_io_collect_interval $time
207 $loop->set_io_collect_interval ($time)
208 EV::set_timeout_collect_interval $time
209 $loop->set_timeout_collect_interval ($time)
210 These advanced functions set the minimum block interval when polling
211 for I/O events and the minimum wait interval for timer events. See
212 the libev documentation at
213 <http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod#FUNCTIONS_CONT
214 ROLLING_THE_EVENT_LOOP> for a more detailed discussion.
215
216WATCHER OBJECTS
94 A watcher is an object that gets created to record your interest in some 217 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, 218 event. For instance, if you want to wait for STDIN to become readable,
96 you would create an EV::io watcher for that: 219 you would create an EV::io watcher for that:
97 220
98 my $watcher = EV::io *STDIN, EV::READ, sub { 221 my $watcher = EV::io *STDIN, EV::READ, sub {
99 my ($watcher, $revents) = @_; 222 my ($watcher, $revents) = @_;
100 warn "yeah, STDIN should not be readable without blocking!\n" 223 warn "yeah, STDIN should now be readable without blocking!\n"
101 }; 224 };
102 225
103 All watchers can be active (waiting for events) or inactive (paused). 226 All watchers can be active (waiting for events) or inactive (paused).
104 Only active watchers will have their callbacks invoked. All callbacks 227 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 228 will be called with at least two arguments: the watcher and a bitmask of
106 received events. 229 received events.
107 230
108 Each watcher type has its associated bit in revents, so you can use the 231 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 232 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, 233 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 234 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 235 events (which can set both EV::READ and EV::WRITE bits), and EV::timer
113 (which uses EV::TIMEOUT). 236 (which uses EV::TIMEOUT).
114 237
115 In the rare case where one wants to create a watcher but not start it at 238 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 239 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. 240 its name, e.g. EV::io has a non-starting variant EV::io_ns and so on.
118 241
119 Please note that a watcher will automatically be stopped when the 242 Please note that a watcher will automatically be stopped when the
120 watcher object is returned, so you *need* to keep the watcher objects 243 watcher object is destroyed, so you *need* to keep the watcher objects
121 returned by the constructors. 244 returned by the constructors.
122 245
123 WATCHER TYPES 246 Also, all methods changing some aspect of a watcher (->set, ->priority,
124 Now lets move to the existing watcher types and asociated methods. 247 ->fh and so on) automatically stop and start it again if it is active,
248 which means pending events get lost.
125 249
126 The following methods are available for all watchers. Then followes a 250 COMMON WATCHER METHODS
127 description of each watcher constructor (EV::io, EV::timer, 251 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).
130 252
131 $w->start 253 $w->start
132 Starts a watcher if it isn't active already. Does nothing to an 254 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 255 already active watcher. By default, all watchers start out in the
134 active state (see the description of the "_ns" variants if you need 256 active state (see the description of the "_ns" variants if you need
135 stopped watchers). 257 stopped watchers).
136 258
137 $w->stop 259 $w->stop
138 Stop a watcher if it is active. Also clear any pending events 260 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 261 (events that have been received but that didn't yet result in a
140 callback invocation), regardless of wether the watcher was active or 262 callback invocation), regardless of whether the watcher was active
141 not. 263 or not.
142 264
143 $bool = $w->is_active 265 $bool = $w->is_active
144 Returns true if the watcher is active, false otherwise. 266 Returns true if the watcher is active, false otherwise.
267
268 $current_data = $w->data
269 $old_data = $w->data ($new_data)
270 Queries a freely usable data scalar on the watcher and optionally
271 changes it. This is a way to associate custom data with a watcher:
272
273 my $w = EV::timer 60, 0, sub {
274 warn $_[0]->data;
275 };
276 $w->data ("print me!");
145 277
146 $current_cb = $w->cb 278 $current_cb = $w->cb
147 $old_cb = $w->cb ($new_cb) 279 $old_cb = $w->cb ($new_cb)
148 Queries the callback on the watcher and optionally changes it. You 280 Queries the callback on the watcher and optionally changes it. You
149 cna do this at any time. 281 can do this at any time without the watcher restarting.
150 282
283 $current_priority = $w->priority
284 $old_priority = $w->priority ($new_priority)
285 Queries the priority on the watcher and optionally changes it.
286 Pending watchers with higher priority will be invoked first. The
287 valid range of priorities lies between EV::MAXPRI (default 2) and
288 EV::MINPRI (default -2). If the priority is outside this range it
289 will automatically be normalised to the nearest valid priority.
290
291 The default priority of any newly-created watcher is 0.
292
293 Note that the priority semantics have not yet been fleshed out and
294 are subject to almost certain change.
295
151 $w->trigger ($revents) 296 $w->invoke ($revents)
152 Call the callback *now* with the given event mask. 297 Call the callback *now* with the given event mask.
153 298
299 $w->feed_event ($revents)
300 Feed some events on this watcher into EV. EV will react to this call
301 as if the watcher had received the given $revents mask.
302
303 $revents = $w->clear_pending
304 If the watcher is pending, this function clears its pending status
305 and returns its $revents bitset (as if its callback was invoked). If
306 the watcher isn't pending it does nothing and returns 0.
307
308 $previous_state = $w->keepalive ($bool)
309 Normally, "EV::loop" will return when there are no active watchers
310 (which is a "deadlock" because no progress can be made anymore).
311 This is convinient because it allows you to start your watchers (and
312 your jobs), call "EV::loop" once and when it returns you know that
313 all your jobs are finished (or they forgot to register some watchers
314 for their task :).
315
316 Sometimes, however, this gets in your way, for example when the
317 module that calls "EV::loop" (usually the main program) is not the
318 same module as a long-living watcher (for example a DNS client
319 module written by somebody else even). Then you might want any
320 outstanding requests to be handled, but you would not want to keep
321 "EV::loop" from returning just because you happen to have this
322 long-running UDP port watcher.
323
324 In this case you can clear the keepalive status, which means that
325 even though your watcher is active, it won't keep "EV::loop" from
326 returning.
327
328 The initial value for keepalive is true (enabled), and you cna
329 change it any time.
330
331 Example: Register an I/O watcher for some UDP socket but do not keep
332 the event loop from running just because of that watcher.
333
334 my $udp_socket = ...
335 my $udp_watcher = EV::io $udp_socket, EV::READ, sub { ... };
336 $1000udp_watcher->keepalive (0);
337
338 $loop = $w->loop
339 Return the loop that this watcher is attached to.
340
341WATCHER TYPES
342 Each of the following subsections describes a single watcher type.
343
344 I/O WATCHERS - is this file descriptor readable or writable?
154 $w = EV::io $fileno_or_fh, $eventmask, $callback 345 $w = EV::io $fileno_or_fh, $eventmask, $callback
155 $w = EV::io_ns $fileno_or_fh, $eventmask, $callback 346 $w = EV::io_ns $fileno_or_fh, $eventmask, $callback
347 $w = $loop->io ($fileno_or_fh, $eventmask, $callback)
348 $w = $loop->io_ns ($fileno_or_fh, $eventmask, $callback)
156 As long as the returned watcher object is alive, call the $callback 349 As long as the returned watcher object is alive, call the $callback
157 when the events specified in $eventmask. 350 when at least one of events specified in $eventmask occurs.
158 351
159 The $eventmask can be one or more of these constants ORed together: 352 The $eventmask can be one or more of these constants ORed together:
160 353
161 EV::READ wait until read() wouldn't block anymore 354 EV::READ wait until read() wouldn't block anymore
162 EV::WRITE wait until write() wouldn't block anymore 355 EV::WRITE wait until write() wouldn't block anymore
… …
174 367
175 $current_eventmask = $w->events 368 $current_eventmask = $w->events
176 $old_eventmask = $w->events ($new_eventmask) 369 $old_eventmask = $w->events ($new_eventmask)
177 Returns the previously set event mask and optionally set a new one. 370 Returns the previously set event mask and optionally set a new one.
178 371
372 TIMER WATCHERS - relative and optionally repeating timeouts
179 $w = EV::timer $after, $repeat, $callback 373 $w = EV::timer $after, $repeat, $callback
180 $w = EV::timer_ns $after, $repeat, $callback 374 $w = EV::timer_ns $after, $repeat, $callback
181 Calls the callback after $after seconds. If $repeat is non-zero, the 375 $w = $loop->timer ($after, $repeat, $callback)
182 timer will be restarted (with the $repeat value as $after) after the 376 $w = $loop->timer_ns ($after, $repeat, $callback)
183 callback returns. 377 Calls the callback after $after seconds (which may be fractional).
378 If $repeat is non-zero, the timer will be restarted (with the
379 $repeat value as $after) after the callback returns.
184 380
185 This means that the callback would be called roughly after $after 381 This means that the callback would be called roughly after $after
186 seconds, and then every $repeat seconds. "Roughly" because the time 382 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 383 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. 384 event loop iteration, and might drift in other cases. If that isn't
385 acceptable, look at EV::periodic, which can provide long-term stable
386 timers.
189 387
190 The timer is based on a monotonic clock, that is if somebody is 388 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 389 sitting in front of the machine while the timer is running and
192 changes the system clock, the timer will nevertheless run (roughly) 390 changes the system clock, the timer will nevertheless run (roughly)
193 the same time. 391 the same time.
194 392
195 The "timer_ns" variant doesn't start (activate) the newly created 393 The "timer_ns" variant doesn't start (activate) the newly created
196 watcher. 394 watcher.
197 395
198 $w->set ($after, $repeat) 396 $w->set ($after, $repeat)
199 Reconfigures the watcher, see the constructor above for details. Can 397 Reconfigures the watcher, see the constructor above for details. Can
200 be at any time. 398 be called at any time.
201 399
202 $w->again 400 $w->again
203 Similar to the "start" method, but has special semantics for 401 Similar to the "start" method, but has special semantics for
204 repeating timers: 402 repeating timers:
205 403
404 If the timer is active and non-repeating, it will be stopped.
405
206 If the timer is active and repeating, reset the timeout to occur 406 If the timer is active and repeating, reset the timeout to occur
207 $repeat seconds after now. 407 $repeat seconds after now.
208 408
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. 409 If the timer is inactive and repeating, start it using the repeat
410 value.
212 411
213 Otherwise do nothing. 412 Otherwise do nothing.
214 413
215 This behaviour is useful when you have a timeout for some IO 414 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 415 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" 416 and $repeat, and then, in the read/write watcher, run the "again"
218 method on the timeout. 417 method on the timeout.
219 418
419 PERIODIC WATCHERS - to cron or not to cron?
220 $w = EV::periodic $at, $interval, $callback 420 $w = EV::periodic $at, $interval, $reschedule_cb, $callback
221 $w = EV::periodic_ns $at, $interval, $callback 421 $w = EV::periodic_ns $at, $interval, $reschedule_cb, $callback
222 Similar to EV::timer, but the time is given as an absolute point in 422 $w = $loop->periodic ($at, $interval, $reschedule_cb, $callback)
223 time ($at), plus an optional $interval. 423 $w = $loop->periodic_ns ($at, $interval, $reschedule_cb, $callback)
424 Similar to EV::timer, but is not based on relative timeouts but on
425 absolute times. Apart from creating "simple" timers that trigger
426 "at" the specified time, it can also be used for non-drifting
427 absolute timers and more complex, cron-like, setups that are not
428 adversely affected by time jumps (i.e. when the system clock is
429 changed by explicit date -s or other means such as ntpd). It is also
430 the most complex watcher type in EV.
224 431
225 If the $interval is zero, then the callback will be called at the 432 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.
228 433
229 If the $interval is nonzero, then the watcher will always be 434 * absolute timer ($interval = $reschedule_cb = 0)
230 scheduled to time out at the next "$at + N * $interval" time.
231 435
232 This can be used to schedule a callback to run at very regular 436 This time simply fires at the wallclock time $at and doesn't
233 intervals, as long as the processing time is less then the interval 437 repeat. It will not adjust when a time jump occurs, that is, if
234 (otherwise obviously events will be skipped). 438 it is to be run at January 1st 2011 then it will run when the
439 system time reaches or surpasses this time.
235 440
441 * repeating interval timer ($interval > 0, $reschedule_cb = 0)
442
443 In this mode the watcher will always be scheduled to time out at
444 the next "$at + N * $interval" time (for some integer N) and
445 then repeat, regardless of any time jumps.
446
447 This can be used to create timers that do not drift with respect
448 to system time:
449
450 my $hourly = EV::periodic 0, 3600, 0, sub { print "once/hour\n" };
451
452 That doesn't mean there will always be 3600 seconds in between
453 triggers, but only that the the clalback will be called when the
454 system time shows a full hour (UTC).
455
236 Another way to think about it (for the mathematically inclined) is 456 Another way to think about it (for the mathematically inclined)
237 that EV::periodic will try to run the callback at the next possible 457 is that EV::periodic will try to run the callback in this mode
238 time where "$time = $at (mod $interval)", regardless of any time 458 at the next possible time where "$time = $at (mod $interval)",
239 jumps. 459 regardless of any time jumps.
240 460
241 This periodic timer is based on "wallclock time", that is, if the 461 * manual reschedule mode ($reschedule_cb = coderef)
242 clock changes ("ntp", "date -s" etc.), then the timer will 462
243 nevertheless run at the specified time. This means it will never 463 In this mode $interval and $at are both being ignored. Instead,
244 drift (it might jitter, but it will not drift). 464 each time the periodic watcher gets scheduled, the reschedule
465 callback ($reschedule_cb) will be called with the watcher as
466 first, and the current time as second argument.
467
468 *This callback MUST NOT stop or destroy this or any other
469 periodic watcher, ever, and MUST NOT call any event loop
470 functions or methods*. If you need to stop it, return 1e30 and
471 stop it afterwards. You may create and start a "EV::prepare"
472 watcher for this task.
473
474 It must return the next time to trigger, based on the passed
475 time value (that is, the lowest time value larger than or equal
476 to to the second argument). It will usually be called just
477 before the callback will be triggered, but might be called at
478 other times, too.
479
480 This can be used to create very complex timers, such as a timer
481 that triggers on each midnight, local time (actually 24 hours
482 after the last midnight, to keep the example simple. If you know
483 a way to do it correctly in about the same space (without
484 requiring elaborate modules), drop me a note :):
485
486 my $daily = EV::periodic 0, 0, sub {
487 my ($w, $now) = @_;
488
489 use Time::Local ();
490 my (undef, undef, undef, $d, $m, $y) = localtime $now;
491 86400 + Time::Local::timelocal 0, 0, 0, $d, $m, $y
492 }, sub {
493 print "it's midnight or likely shortly after, now\n";
494 };
245 495
246 The "periodic_ns" variant doesn't start (activate) the newly created 496 The "periodic_ns" variant doesn't start (activate) the newly created
247 watcher. 497 watcher.
248 498
249 $w->set ($at, $interval) 499 $w->set ($at, $interval, $reschedule_cb)
250 Reconfigures the watcher, see the constructor above for details. Can 500 Reconfigures the watcher, see the constructor above for details. Can
251 be at any time. 501 be called at any time.
252 502
503 $w->again
504 Simply stops and starts the watcher again.
505
506 $time = $w->at
507 Return the time that the watcher is expected to trigger next.
508
509 SIGNAL WATCHERS - signal me when a signal gets signalled!
253 $w = EV::signal $signal, $callback 510 $w = EV::signal $signal, $callback
254 $w = EV::signal_ns $signal, $callback 511 $w = EV::signal_ns $signal, $callback
255 Call the callback when $signal is received (the signal can be 512 Call the callback when $signal is received (the signal can be
256 specified by number or by name, just as with kill or %SIG). 513 specified by number or by name, just as with "kill" or %SIG).
257 514
258 EV will grab the signal for the process (the kernel only allows one 515 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 516 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 517 watcher, and removes it again when you stop it. Perl does the same
261 when you add/remove callbacks to %SIG, so watch out. 518 when you add/remove callbacks to %SIG, so watch out.
… …
265 The "signal_ns" variant doesn't start (activate) the newly created 522 The "signal_ns" variant doesn't start (activate) the newly created
266 watcher. 523 watcher.
267 524
268 $w->set ($signal) 525 $w->set ($signal)
269 Reconfigures the watcher, see the constructor above for details. Can 526 Reconfigures the watcher, see the constructor above for details. Can
270 be at any time. 527 be called at any time.
271 528
529 $current_signum = $w->signal
530 $old_signum = $w->signal ($new_signal)
531 Returns the previously set signal (always as a number not name) and
532 optionally set a new one.
533
534 CHILD WATCHERS - watch out for process status changes
272 $w = EV::child $pid, $callback 535 $w = EV::child $pid, $trace, $callback
273 $w = EV::child_ns $pid, $callback 536 $w = EV::child_ns $pid, $trace, $callback
537 $w = $loop->child ($pid, $trace, $callback)
538 $w = $loop->child_ns ($pid, $trace, $callback)
274 Call the callback when a status change for pid $pid (or any pid if 539 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 540 $pid is 0) has been received (a status change happens when the
541 process terminates or is killed, or, when trace is true,
542 additionally when it is stopped or continued). More precisely: when
276 receives a SIGCHLD, EV will fetch the outstanding exit/wait status 543 the process receives a "SIGCHLD", EV will fetch the outstanding
277 for all changed/zombie children and call the callback. 544 exit/wait status for all changed/zombie children and call the
545 callback.
278 546
279 Unlike all other callbacks, this callback will be called with an 547 It is valid (and fully supported) to install a child watcher after a
280 additional third argument which is the exit status. See the 548 child has exited but before the event loop has started its next
281 "waitpid" function for details. 549 iteration (for example, first you "fork", then the new child process
550 might exit, and only then do you install a child watcher in the
551 parent for the new pid).
282 552
553 You can access both exit (or tracing) status and pid by using the
554 "rstatus" and "rpid" methods on the watcher object.
555
283 You can have as many pid watchers per pid as you want. 556 You can have as many pid watchers per pid as you want, they will all
557 be called.
284 558
285 The "child_ns" variant doesn't start (activate) the newly created 559 The "child_ns" variant doesn't start (activate) the newly created
286 watcher. 560 watcher.
287 561
288 $w->set ($pid) 562 $w->set ($pid, $trace)
289 Reconfigures the watcher, see the constructor above for details. Can 563 Reconfigures the watcher, see the constructor above for details. Can
290 be at any time. 564 be called at any time.
291 565
566 $current_pid = $w->pid
567 Returns the previously set process id and optionally set a new one.
568
569 $exit_status = $w->rstatus
570 Return the exit/wait status (as returned by waitpid, see the waitpid
571 entry in perlfunc).
572
573 $pid = $w->rpid
574 Return the pid of the awaited child (useful when you have installed
575 a watcher for all pids).
576
577 STAT WATCHERS - did the file attributes just change?
578 $w = EV::stat $path, $interval, $callback
579 $w = EV::stat_ns $path, $interval, $callback
580 $w = $loop->stat ($path, $interval, $callback)
581 $w = $loop->stat_ns ($path, $interval, $callback)
582 Call the callback when a file status change has been detected on
583 $path. The $path does not need to exist, changing from "path exists"
584 to "path does not exist" is a status change like any other.
585
586 The $interval is a recommended polling interval for systems where
587 OS-supported change notifications don't exist or are not supported.
588 If you use 0 then an unspecified default is used (which is highly
589 recommended!), which is to be expected to be around five seconds
590 usually.
591
592 This watcher type is not meant for massive numbers of stat watchers,
593 as even with OS-supported change notifications, this can be
594 resource-intensive.
595
596 The "stat_ns" variant doesn't start (activate) the newly created
597 watcher.
598
599 ... = $w->stat
600 This call is very similar to the perl "stat" built-in: It stats
601 (using "lstat") the path specified in the watcher and sets perls
602 stat cache (as well as EV's idea of the current stat values) to the
603 values found.
604
605 In scalar context, a boolean is return indicating success or failure
606 of the stat. In list context, the same 13-value list as with stat is
607 returned (except that the blksize and blocks fields are not
608 reliable).
609
610 In the case of an error, errno is set to "ENOENT" (regardless of the
611 actual error value) and the "nlink" value is forced to zero (if the
612 stat was successful then nlink is guaranteed to be non-zero).
613
614 See also the next two entries for more info.
615
616 ... = $w->attr
617 Just like "$w->stat", but without the initial stat'ing: this returns
618 the values most recently detected by EV. See the next entry for more
619 info.
620
621 ... = $w->prev
622 Just like "$w->stat", but without the initial stat'ing: this returns
623 the previous set of values, before the change.
624
625 That is, when the watcher callback is invoked, "$w->prev" will be
626 set to the values found *before* a change was detected, while
627 "$w->attr" returns the values found leading to the change detection.
628 The difference (if any) between "prev" and "attr" is what triggered
629 the callback.
630
631 If you did something to the filesystem object and do not want to
632 trigger yet another change, you can call "stat" to update EV's idea
633 of what the current attributes are.
634
635 $w->set ($path, $interval)
636 Reconfigures the watcher, see the constructor above for details. Can
637 be called at any time.
638
639 $current_path = $w->path
640 $old_path = $w->path ($new_path)
641 Returns the previously set path and optionally set a new one.
642
643 $current_interval = $w->interval
644 $old_interval = $w->interval ($new_interval)
645 Returns the previously set interval and optionally set a new one.
646 Can be used to query the actual interval used.
647
648 IDLE WATCHERS - when you've got nothing better to do...
292 $w = EV::idle $callback 649 $w = EV::idle $callback
293 $w = EV::idle_ns $callback 650 $w = EV::idle_ns $callback
651 $w = $loop->idle ($callback)
652 $w = $loop->idle_ns ($callback)
294 Call the callback when there are no pending io, timer/periodic, 653 Call the callback when there are no other pending watchers of the
295 signal or child events, i.e. when the process is idle. 654 same or higher priority (excluding check, prepare and other idle
655 watchers of the same or lower priority, of course). They are called
656 idle watchers because when the watcher is the highest priority
657 pending event in the process, the process is considered to be idle
658 at that priority.
659
660 If you want a watcher that is only ever called when *no* other
661 events are outstanding you have to set the priority to "EV::MINPRI".
296 662
297 The process will not block as long as any idle watchers are active, 663 The process will not block as long as any idle watchers are active,
298 and they will be called repeatedly until stopped. 664 and they will be called repeatedly until stopped.
299 665
666 For example, if you have idle watchers at priority 0 and 1, and an
667 I/O watcher at priority 0, then the idle watcher at priority 1 and
668 the I/O watcher will always run when ready. Only when the idle
669 watcher at priority 1 is stopped and the I/O watcher at priority 0
670 is not pending with the 0-priority idle watcher be invoked.
671
300 The "idle_ns" variant doesn't start (activate) the newly created 672 The "idle_ns" variant doesn't start (activate) the newly created
301 watcher. 673 watcher.
302 674
675 PREPARE WATCHERS - customise your event loop!
303 $w = EV::prepare $callback 676 $w = EV::prepare $callback
304 $w = EV::prepare_ns $callback 677 $w = EV::prepare_ns $callback
678 $w = $loop->prepare ($callback)
679 $w = $loop->prepare_ns ($callback)
305 Call the callback just before the process would block. You can still 680 Call the callback just before the process would block. You can still
306 create/modify any watchers at this point. 681 create/modify any watchers at this point.
307 682
308 See the EV::check watcher, below, for explanations and an example. 683 See the EV::check watcher, below, for explanations and an example.
309 684
310 The "prepare_ns" variant doesn't start (activate) the newly created 685 The "prepare_ns" variant doesn't start (activate) the newly created
311 watcher. 686 watcher.
312 687
688 CHECK WATCHERS - customise your event loop even more!
313 $w = EV::check $callback 689 $w = EV::check $callback
314 $w = EV::check_ns $callback 690 $w = EV::check_ns $callback
691 $w = $loop->check ($callback)
692 $w = $loop->check_ns ($callback)
315 Call the callback just after the process wakes up again (after it 693 Call the callback just after the process wakes up again (after it
316 has gathered events), but before any other callbacks have been 694 has gathered events), but before any other callbacks have been
317 invoked. 695 invoked.
318 696
319 This is used to integrate other event-based software into the EV 697 This is used to integrate other event-based software into the EV
… …
328 # do nothing unless active 706 # do nothing unless active
329 $dispatcher->{_event_queue_h} 707 $dispatcher->{_event_queue_h}
330 or return; 708 or return;
331 709
332 # make the dispatcher handle any outstanding stuff 710 # make the dispatcher handle any outstanding stuff
711 ... not shown
333 712
334 # create an IO watcher for each and every socket 713 # create an I/O watcher for each and every socket
335 @snmp_watcher = ( 714 @snmp_watcher = (
336 (map { EV::io $_, EV::READ, sub { } } 715 (map { EV::io $_, EV::READ, sub { } }
337 keys %{ $dispatcher->{_descriptors} }), 716 keys %{ $dispatcher->{_descriptors} }),
717
718 EV::timer +($event->[Net::SNMP::Dispatcher::_ACTIVE]
719 ? $event->[Net::SNMP::Dispatcher::_TIME] - EV::now : 0),
720 0, sub { },
338 ); 721 );
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 }; 722 };
344 723
345 The callbacks are irrelevant, the only purpose of those watchers is 724 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 725 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 726 one of those events occurs (socket readable, or timer timed out).
348 will then clean up: 727 The corresponding EV::check watcher will then clean up:
349 728
350 our $snmp_check = EV::check sub { 729 our $snmp_check = EV::check sub {
351 # destroy all watchers 730 # destroy all watchers
352 @snmp_watcher = (); 731 @snmp_watcher = ();
353 732
354 # make the dispatcher handle any new stuff 733 # make the dispatcher handle any new stuff
734 ... not shown
355 }; 735 };
356 736
357 The callbacks of the created watchers will not be called as the 737 The callbacks of the created watchers will not be called as the
358 watchers are destroyed before this cna happen (remember EV::check 738 watchers are destroyed before this cna happen (remember EV::check
359 gets called first). 739 gets called first).
360 740
361 The "check_ns" variant doesn't start (activate) the newly created 741 The "check_ns" variant doesn't start (activate) the newly created
362 watcher. 742 watcher.
363 743
744 FORK WATCHERS - the audacity to resume the event loop after a fork
745 Fork watchers are called when a "fork ()" was detected. The invocation
746 is done before the event loop blocks next and before "check" watchers
747 are being called, and only in the child after the fork.
748
749 $w = EV::fork $callback
750 $w = EV::fork_ns $callback
751 $w = $loop->fork ($callback)
752 $w = $loop->fork_ns ($callback)
753 Call the callback before the event loop is resumed in the child
754 process after a fork.
755
756 The "fork_ns" variant doesn't start (activate) the newly created
757 watcher.
758
759 EMBED WATCHERS - when one backend isn't enough...
760 This is a rather advanced watcher type that lets you embed one event
761 loop into another (currently only IO events are supported in the
762 embedded loop, other types of watchers might be handled in a delayed or
763 incorrect fashion and must not be used).
764
765 See the libev documentation at
766 <http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod#code_ev_embed_code
767 _when_one_backend_> for more details.
768
769 In short, this watcher is most useful on BSD systems without working
770 kqueue to still be able to handle a large number of sockets:
771
772 my $socket_loop;
773
774 # check wether we use SELECT or POLL _and_ KQUEUE is supported
775 if (
776 (EV::backend & (EV::BACKEND_POLL | EV::BACKEND_SELECT))
777 && (EV::supported_backends & EV::embeddable_backends & EV::BACKEND_KQUEUE)
778 ) {
779 # use kqueue for sockets
780 $socket_loop = new EV::Loop EV::BACKEND_KQUEUE | EV::FLAG_NOENV;
781 }
782
783 # use the default loop otherwise
784 $socket_loop ||= EV::default_loop;
785
786 $w = EV::embed $otherloop, $callback
787 $w = EV::embed_ns $otherloop, $callback
788 $w = $loop->embed ($otherloop, $callback)
789 $w = $loop->embed_ns ($otherloop, $callback)
790 Call the callback when the embedded event loop ($otherloop) has any
791 I/O activity. The $callback should alwas be specified as "undef" in
792 this version of EV, which means the embedded event loop will be
793 managed automatically.
794
795 The "embed_ns" variant doesn't start (activate) the newly created
796 watcher.
797
798 ASYNC WATCHERS - how to wake up another event loop
799 Async watchers are provided by EV, but have little use in perl directly,
800 as perl neither supports threads nor direct access to signal handlers or
801 other contexts where they could be of value.
802
803 It is, however, possible to use them from the XS level.
804
805 Please see the libev documentation for further details.
806
807 $w = EV::async $callback
808 $w = EV::async_ns $callback
809 $w->send
810 $bool = $w->async_pending
811
812PERL SIGNALS
813 While Perl signal handling (%SIG) is not affected by EV, the behaviour
814 with EV is as the same as any other C library: Perl-signals will only be
815 handled when Perl runs, which means your signal handler might be invoked
816 only the next time an event callback is invoked.
817
818 The solution is to use EV signal watchers (see "EV::signal"), which will
819 ensure proper operations with regards to other event watchers.
820
821 If you cannot do this for whatever reason, you can also force a watcher
822 to be called on every event loop iteration by installing a "EV::check"
823 watcher:
824
825 my $async_check = EV::check sub { };
826
827 This ensures that perl gets into control for a short time to handle any
828 pending signals, and also ensures (slightly) slower overall operation.
829
364THREADS 830THREADS
365 Threads are not supported by this in any way. Perl pseudo-threads is 831 Threads are not supported by this module in any way. Perl pseudo-threads
366 evil stuff and must die. 832 is evil stuff and must die. As soon as Perl gains real threads I will
833 work on thread support for it.
834
835FORK
836 Most of the "improved" event delivering mechanisms of modern operating
837 systems have quite a few problems with fork(2) (to put it bluntly: it is
838 not supported and usually destructive). Libev makes it possible to work
839 around this by having a function that recreates the kernel state after
840 fork in the child.
841
842 On non-win32 platforms, this module requires the pthread_atfork
843 functionality to do this automatically for you. This function is quite
844 buggy on most BSDs, though, so YMMV. The overhead for this is quite
845 negligible, because everything the function currently does is set a flag
846 that is checked only when the event loop gets used the next time, so
847 when you do fork but not use EV, the overhead is minimal.
848
849 On win32, there is no notion of fork so all this doesn't apply, of
850 course.
367 851
368SEE ALSO 852SEE ALSO
369 L<EV::DNS>, L<EV::AnyEvent>. 853 EV::ADNS (asynchronous DNS), Glib::EV (makes Glib/Gtk2 use EV as event
854 loop), EV::Glib (embed Glib into EV), Coro::EV (efficient coroutines
855 with EV), Net::SNMP::EV (asynchronous SNMP), AnyEvent for event-loop
856 agnostic and portable event driven programming.
370 857
371AUTHOR 858AUTHOR
372 Marc Lehmann <schmorp@schmorp.de> 859 Marc Lehmann <schmorp@schmorp.de>
373 http://home.schmorp.de/ 860 http://home.schmorp.de/
374 861

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