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1NAME 1NAME
2 EV - perl interface to libev, a high performance full-featured event 2 EV - perl interface to libev, a high performance full-featured event
3 loop 3 loop
4 4
5SYNOPSIS 5SYNOPSIS
6 use EV; 6 use EV;
7
8 # TIMERS
9
10 my $w = EV::timer 2, 0, sub {
11 warn "is called after 2s";
12 };
13
14 my $w = EV::timer 2, 2, sub {
15 warn "is called roughly every 2s (repeat = 2)";
16 };
17
18 undef $w; # destroy event watcher again
19
20 my $w = EV::periodic 0, 60, 0, sub {
21 warn "is called every minute, on the minute, exactly";
22 };
23
24 # IO
25
26 my $w = EV::io *STDIN, EV::READ, sub {
27 my ($w, $revents) = @_; # all callbacks receive the watcher and event mask
28 warn "stdin is readable, you entered: ", <STDIN>;
29 };
30
31 # SIGNALS
32
33 my $w = EV::signal 'QUIT', sub {
34 warn "sigquit received\n";
35 };
36
37 # CHILD/PID STATUS CHANGES
7 38
8 # TIMERS 39 my $w = EV::child 666, 0, sub {
40 my ($w, $revents) = @_;
41 my $status = $w->rstatus;
42 };
9 43
10 my $w = EV::timer 2, 0, sub {
11 warn "is called after 2s";
12 };
13
14 my $w = EV::timer 2, 2, sub {
15 warn "is called roughly every 2s (repeat = 2)";
16 };
17
18 undef $w; # destroy event watcher again
19
20 my $w = EV::periodic 0, 60, 0, sub {
21 warn "is called every minute, on the minute, exactly";
22 };
23
24 # IO
25
26 my $w = EV::io *STDIN, EV::READ, sub {
27 my ($w, $revents) = @_; # all callbacks receive the watcher and event mask
28 warn "stdin is readable, you entered: ", <STDIN>;
29 };
30
31 # SIGNALS
32
33 my $w = EV::signal 'QUIT', sub {
34 warn "sigquit received\n";
35 };
36
37 # CHILD/PID STATUS CHANGES 44 # STAT CHANGES
38 45 my $w = EV::stat "/etc/passwd", 10, sub {
39 my $w = EV::child 666, sub {
40 my ($w, $revents) = @_; 46 my ($w, $revents) = @_;
41 my $status = $w->rstatus; 47 warn $w->path, " has changed somehow.\n";
42 }; 48 };
43 49
44 # MAINLOOP 50 # MAINLOOP
45 EV::loop; # loop until EV::unloop is called or all watchers stop 51 EV::loop; # loop until EV::unloop is called or all watchers stop
46 EV::loop EV::LOOP_ONESHOT; # block until at least one event could be handled 52 EV::loop EV::LOOP_ONESHOT; # block until at least one event could be handled
47 EV::loop EV::LOOP_NONBLOCK; # try to handle same events, but do not block 53 EV::loop EV::LOOP_NONBLOCK; # try to handle same events, but do not block
54
55BEFORE YOU START USING THIS MODULE
56 If you only need timer, I/O, signal, child and idle watchers and not the
57 advanced functionality of this module, consider using AnyEvent instead,
58 specifically the simplified API described in AE.
59
60 When used with EV as backend, the AE API is as fast as the native EV
61 API, but your programs/modules will still run with many other event
62 loops.
48 63
49DESCRIPTION 64DESCRIPTION
50 This module provides an interface to libev 65 This module provides an interface to libev
51 (<http://software.schmorp.de/pkg/libev.html>). 66 (<http://software.schmorp.de/pkg/libev.html>). While the documentation
67 below is comprehensive, one might also consult the documentation of
68 libev itself (<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod> or
69 perldoc EV::libev) for more subtle details on watcher semantics or some
70 discussion on the available backends, or how to force a specific backend
71 with "LIBEV_FLAGS", or just about in any case because it has much more
72 detailed information.
73
74 This module is very fast and scalable. It is actually so fast that you
75 can use it through the AnyEvent module, stay portable to other event
76 loops (if you don't rely on any watcher types not available through it)
77 and still be faster than with any other event loop currently supported
78 in Perl.
79
80 MODULE EXPORTS
81 This module does not export any symbols.
82
83EVENT LOOPS
84 EV supports multiple event loops: There is a single "default event loop"
85 that can handle everything including signals and child watchers, and any
86 number of "dynamic event loops" that can use different backends (with
87 various limitations), but no child and signal watchers.
88
89 You do not have to do anything to create the default event loop: When
90 the module is loaded a suitable backend is selected on the premise of
91 selecting a working backend (which for example rules out kqueue on most
92 BSDs). Modules should, unless they have "special needs" always use the
93 default loop as this is fastest (perl-wise), best supported by other
94 modules (e.g. AnyEvent or Coro) and most portable event loop.
95
96 For specific programs you can create additional event loops dynamically.
97
98 If you want to take advantage of kqueue (which often works properly for
99 sockets only) even though the default loop doesn't enable it, you can
100 *embed* a kqueue loop into the default loop: running the default loop
101 will then also service the kqueue loop to some extent. See the example
102 in the section about embed watchers for an example on how to achieve
103 that.
104
105 $loop = new EV::Loop [$flags]
106 Create a new event loop as per the specified flags. Please refer to
107 the "ev_loop_new ()" function description in the libev documentation
108 (<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod#GLOBAL_FUNCTI
109 ONS>, or locally-installed as EV::libev manpage) for more info.
110
111 The loop will automatically be destroyed when it is no longer
112 referenced by any watcher and the loop object goes out of scope.
113
114 If you are not embedding the loop, then Using "EV::FLAG_FORKCHECK"
115 is recommended, as only the default event loop is protected by this
116 module. If you *are* embedding this loop in the default loop, this
117 is not necessary, as "EV::embed" automatically does the right thing
118 on fork.
119
120 $loop->loop_fork
121 Must be called after a fork in the child, before entering or
122 continuing the event loop. An alternative is to use
123 "EV::FLAG_FORKCHECK" which calls this function automatically, at
124 some performance loss (refer to the libev documentation).
125
126 $loop->loop_verify
127 Calls "ev_verify" to make internal consistency checks (for debugging
128 libev) and abort the program if any data structures were found to be
129 corrupted.
130
131 $loop = EV::default_loop [$flags]
132 Return the default loop (which is a singleton object). Since this
133 module already creates the default loop with default flags,
134 specifying flags here will not have any effect unless you destroy
135 the default loop first, which isn't supported. So in short: don't do
136 it, and if you break it, you get to keep the pieces.
52 137
53BASIC INTERFACE 138BASIC INTERFACE
54 $EV::DIED 139 $EV::DIED
55 Must contain a reference to a function that is called when a 140 Must contain a reference to a function that is called when a
56 callback throws an exception (with $@ containing thr error). The 141 callback throws an exception (with $@ containing the error). The
57 default prints an informative message and continues. 142 default prints an informative message and continues.
58 143
59 If this callback throws an exception it will be silently ignored. 144 If this callback throws an exception it will be silently ignored.
145
146 $flags = EV::supported_backends
147 $flags = EV::recommended_backends
148 $flags = EV::embeddable_backends
149 Returns the set (see "EV::BACKEND_*" flags) of backends supported by
150 this instance of EV, the set of recommended backends (supposed to be
151 good) for this platform and the set of embeddable backends (see
152 EMBED WATCHERS).
153
154 EV::sleep $seconds
155 Block the process for the given number of (fractional) seconds.
60 156
61 $time = EV::time 157 $time = EV::time
62 Returns the current time in (fractional) seconds since the epoch. 158 Returns the current time in (fractional) seconds since the epoch.
63 159
64 $time = EV::now 160 $time = EV::now
161 $time = $loop->now
65 Returns the time the last event loop iteration has been started. 162 Returns the time the last event loop iteration has been started.
66 This is the time that (relative) timers are based on, and refering 163 This is the time that (relative) timers are based on, and referring
67 to it is usually faster then calling EV::time. 164 to it is usually faster then calling EV::time.
68 165
69 $method = EV::ev_method 166 EV::now_update
167 $loop->now_update
168 Establishes the current time by querying the kernel, updating the
169 time returned by "EV::now" in the progress. This is a costly
170 operation and is usually done automatically within "EV::loop".
171
172 This function is rarely useful, but when some event callback runs
173 for a very long time without entering the event loop, updating
174 libev's idea of the current time is a good idea.
175
176 EV::suspend
177 $loop->suspend
178 EV::resume
179 $loop->resume
180 These two functions suspend and resume a loop, for use when the loop
181 is not used for a while and timeouts should not be processed.
182
183 A typical use case would be an interactive program such as a game:
184 When the user presses "^Z" to suspend the game and resumes it an
185 hour later it would be best to handle timeouts as if no time had
186 actually passed while the program was suspended. This can be
187 achieved by calling "suspend" in your "SIGTSTP" handler, sending
188 yourself a "SIGSTOP" and calling "resume" directly afterwards to
189 resume timer processing.
190
191 Effectively, all "timer" watchers will be delayed by the time spend
192 between "suspend" and "resume", and all "periodic" watchers will be
193 rescheduled (that is, they will lose any events that would have
194 occured while suspended).
195
196 After calling "suspend" you must not call *any* function on the
197 given loop other than "resume", and you must not call "resume"
198 without a previous call to "suspend".
199
200 Calling "suspend"/"resume" has the side effect of updating the event
201 loop time (see "now_update").
202
203 $backend = EV::backend
204 $backend = $loop->backend
70 Returns an integer describing the backend used by libev 205 Returns an integer describing the backend used by libev
71 (EV::METHOD_SELECT or EV::METHOD_EPOLL). 206 (EV::BACKEND_SELECT or EV::BACKEND_EPOLL).
72 207
73 EV::loop [$flags] 208 EV::loop [$flags]
209 $loop->loop ([$flags])
74 Begin checking for events and calling callbacks. It returns when a 210 Begin checking for events and calling callbacks. It returns when a
75 callback calls EV::unloop. 211 callback calls EV::unloop.
76 212
77 The $flags argument can be one of the following: 213 The $flags argument can be one of the following:
78 214
79 0 as above 215 0 as above
80 EV::LOOP_ONESHOT block at most once (wait, but do not loop) 216 EV::LOOP_ONESHOT block at most once (wait, but do not loop)
81 EV::LOOP_NONBLOCK do not block at all (fetch/handle events but do not wait) 217 EV::LOOP_NONBLOCK do not block at all (fetch/handle events but do not wait)
82 218
83 EV::unloop [$how] 219 EV::unloop [$how]
220 $loop->unloop ([$how])
84 When called with no arguments or an argument of EV::UNLOOP_ONE, 221 When called with no arguments or an argument of EV::UNLOOP_ONE,
85 makes the innermost call to EV::loop return. 222 makes the innermost call to EV::loop return.
86 223
87 When called with an argument of EV::UNLOOP_ALL, all calls to 224 When called with an argument of EV::UNLOOP_ALL, all calls to
88 EV::loop will return as fast as possible. 225 EV::loop will return as fast as possible.
89 226
90 WATCHER 227 $count = EV::loop_count
228 $count = $loop->loop_count
229 Return the number of times the event loop has polled for new events.
230 Sometimes useful as a generation counter.
231
232 EV::once $fh_or_undef, $events, $timeout, $cb->($revents)
233 $loop->once ($fh_or_undef, $events, $timeout, $cb->($revents))
234 This function rolls together an I/O and a timer watcher for a single
235 one-shot event without the need for managing a watcher object.
236
237 If $fh_or_undef is a filehandle or file descriptor, then $events
238 must be a bitset containing either "EV::READ", "EV::WRITE" or
239 "EV::READ | EV::WRITE", indicating the type of I/O event you want to
240 wait for. If you do not want to wait for some I/O event, specify
241 "undef" for $fh_or_undef and 0 for $events).
242
243 If timeout is "undef" or negative, then there will be no timeout.
244 Otherwise a EV::timer with this value will be started.
245
246 When an error occurs or either the timeout or I/O watcher triggers,
247 then the callback will be called with the received event set (in
248 general you can expect it to be a combination of "EV::ERROR",
249 "EV::READ", "EV::WRITE" and "EV::TIMER").
250
251 EV::once doesn't return anything: the watchers stay active till
252 either of them triggers, then they will be stopped and freed, and
253 the callback invoked.
254
255 EV::feed_fd_event ($fd, $revents)
256 $loop->feed_fd_event ($fd, $revents)
257 Feed an event on a file descriptor into EV. EV will react to this
258 call as if the readyness notifications specified by $revents (a
259 combination of "EV::READ" and "EV::WRITE") happened on the file
260 descriptor $fd.
261
262 EV::feed_signal_event ($signal)
263 Feed a signal event into EV. EV will react to this call as if the
264 signal specified by $signal had occured.
265
266 EV::set_io_collect_interval $time
267 $loop->set_io_collect_interval ($time)
268 EV::set_timeout_collect_interval $time
269 $loop->set_timeout_collect_interval ($time)
270 These advanced functions set the minimum block interval when polling
271 for I/O events and the minimum wait interval for timer events. See
272 the libev documentation at
273 <http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod#FUNCTIONS_CONT
274 ROLLING_THE_EVENT_LOOP> (locally installed as EV::libev) for a more
275 detailed discussion.
276
277 $count = EV::pending_count
278 $count = $loop->pending_count
279 Returns the number of currently pending watchers.
280
281 EV::invoke_pending
282 $loop->invoke_pending
283 Invoke all currently pending watchers.
284
285WATCHER OBJECTS
91 A watcher is an object that gets created to record your interest in some 286 A watcher is an object that gets created to record your interest in some
92 event. For instance, if you want to wait for STDIN to become readable, 287 event. For instance, if you want to wait for STDIN to become readable,
93 you would create an EV::io watcher for that: 288 you would create an EV::io watcher for that:
94 289
95 my $watcher = EV::io *STDIN, EV::READ, sub { 290 my $watcher = EV::io *STDIN, EV::READ, sub {
96 my ($watcher, $revents) = @_; 291 my ($watcher, $revents) = @_;
97 warn "yeah, STDIN should not be readable without blocking!\n" 292 warn "yeah, STDIN should now be readable without blocking!\n"
98 }; 293 };
99 294
100 All watchers can be active (waiting for events) or inactive (paused). 295 All watchers can be active (waiting for events) or inactive (paused).
101 Only active watchers will have their callbacks invoked. All callbacks 296 Only active watchers will have their callbacks invoked. All callbacks
102 will be called with at least two arguments: the watcher and a bitmask of 297 will be called with at least two arguments: the watcher and a bitmask of
103 received events. 298 received events.
104 299
105 Each watcher type has its associated bit in revents, so you can use the 300 Each watcher type has its associated bit in revents, so you can use the
106 same callback for multiple watchers. The event mask is named after the 301 same callback for multiple watchers. The event mask is named after the
107 type, i..e. EV::child sets EV::CHILD, EV::prepare sets EV::PREPARE, 302 type, i.e. EV::child sets EV::CHILD, EV::prepare sets EV::PREPARE,
108 EV::periodic sets EV::PERIODIC and so on, with the exception of IO 303 EV::periodic sets EV::PERIODIC and so on, with the exception of I/O
109 events (which can set both EV::READ and EV::WRITE bits), and EV::timer 304 events (which can set both EV::READ and EV::WRITE bits).
110 (which uses EV::TIMEOUT).
111 305
112 In the rare case where one wants to create a watcher but not start it at 306 In the rare case where one wants to create a watcher but not start it at
113 the same time, each constructor has a variant with a trailing "_ns" in 307 the same time, each constructor has a variant with a trailing "_ns" in
114 its name, e.g. EV::io has a non-starting variant EV::io_ns and so on. 308 its name, e.g. EV::io has a non-starting variant EV::io_ns and so on.
115 309
… …
119 313
120 Also, all methods changing some aspect of a watcher (->set, ->priority, 314 Also, all methods changing some aspect of a watcher (->set, ->priority,
121 ->fh and so on) automatically stop and start it again if it is active, 315 ->fh and so on) automatically stop and start it again if it is active,
122 which means pending events get lost. 316 which means pending events get lost.
123 317
124 WATCHER TYPES 318 COMMON WATCHER METHODS
125 Now lets move to the existing watcher types and asociated methods. 319 This section lists methods common to all watchers.
126
127 The following methods are available for all watchers. Then followes a
128 description of each watcher constructor (EV::io, EV::timer,
129 EV::periodic, EV::signal, EV::child, EV::idle, EV::prepare and
130 EV::check), followed by any type-specific methods (if any).
131 320
132 $w->start 321 $w->start
133 Starts a watcher if it isn't active already. Does nothing to an 322 Starts a watcher if it isn't active already. Does nothing to an
134 already active watcher. By default, all watchers start out in the 323 already active watcher. By default, all watchers start out in the
135 active state (see the description of the "_ns" variants if you need 324 active state (see the description of the "_ns" variants if you need
136 stopped watchers). 325 stopped watchers).
137 326
138 $w->stop 327 $w->stop
139 Stop a watcher if it is active. Also clear any pending events 328 Stop a watcher if it is active. Also clear any pending events
140 (events that have been received but that didn't yet result in a 329 (events that have been received but that didn't yet result in a
141 callback invocation), regardless of wether the watcher was active or 330 callback invocation), regardless of whether the watcher was active
142 not. 331 or not.
143 332
144 $bool = $w->is_active 333 $bool = $w->is_active
145 Returns true if the watcher is active, false otherwise. 334 Returns true if the watcher is active, false otherwise.
146 335
147 $current_data = $w->data 336 $current_data = $w->data
… …
165 Pending watchers with higher priority will be invoked first. The 354 Pending watchers with higher priority will be invoked first. The
166 valid range of priorities lies between EV::MAXPRI (default 2) and 355 valid range of priorities lies between EV::MAXPRI (default 2) and
167 EV::MINPRI (default -2). If the priority is outside this range it 356 EV::MINPRI (default -2). If the priority is outside this range it
168 will automatically be normalised to the nearest valid priority. 357 will automatically be normalised to the nearest valid priority.
169 358
170 The default priority of any newly-created weatcher is 0. 359 The default priority of any newly-created watcher is 0.
171 360
361 Note that the priority semantics have not yet been fleshed out and
362 are subject to almost certain change.
363
172 $w->trigger ($revents) 364 $w->invoke ($revents)
173 Call the callback *now* with the given event mask. 365 Call the callback *now* with the given event mask.
174 366
367 $w->feed_event ($revents)
368 Feed some events on this watcher into EV. EV will react to this call
369 as if the watcher had received the given $revents mask.
370
371 $revents = $w->clear_pending
372 If the watcher is pending, this function clears its pending status
373 and returns its $revents bitset (as if its callback was invoked). If
374 the watcher isn't pending it does nothing and returns 0.
375
376 $previous_state = $w->keepalive ($bool)
377 Normally, "EV::loop" will return when there are no active watchers
378 (which is a "deadlock" because no progress can be made anymore).
379 This is convenient because it allows you to start your watchers (and
380 your jobs), call "EV::loop" once and when it returns you know that
381 all your jobs are finished (or they forgot to register some watchers
382 for their task :).
383
384 Sometimes, however, this gets in your way, for example when the
385 module that calls "EV::loop" (usually the main program) is not the
386 same module as a long-living watcher (for example a DNS client
387 module written by somebody else even). Then you might want any
388 outstanding requests to be handled, but you would not want to keep
389 "EV::loop" from returning just because you happen to have this
390 long-running UDP port watcher.
391
392 In this case you can clear the keepalive status, which means that
393 even though your watcher is active, it won't keep "EV::loop" from
394 returning.
395
396 The initial value for keepalive is true (enabled), and you can
397 change it any time.
398
399 Example: Register an I/O watcher for some UDP socket but do not keep
400 the event loop from running just because of that watcher.
401
402 my $udp_socket = ...
403 my $udp_watcher = EV::io $udp_socket, EV::READ, sub { ... };
404 $udp_watcher->keepalive (0);
405
406 $loop = $w->loop
407 Return the loop that this watcher is attached to.
408
409WATCHER TYPES
410 Each of the following subsections describes a single watcher type.
411
412 I/O WATCHERS - is this file descriptor readable or writable?
175 $w = EV::io $fileno_or_fh, $eventmask, $callback 413 $w = EV::io $fileno_or_fh, $eventmask, $callback
176 $w = EV::io_ns $fileno_or_fh, $eventmask, $callback 414 $w = EV::io_ns $fileno_or_fh, $eventmask, $callback
415 $w = $loop->io ($fileno_or_fh, $eventmask, $callback)
416 $w = $loop->io_ns ($fileno_or_fh, $eventmask, $callback)
177 As long as the returned watcher object is alive, call the $callback 417 As long as the returned watcher object is alive, call the $callback
178 when the events specified in $eventmask. 418 when at least one of events specified in $eventmask occurs.
179 419
180 The $eventmask can be one or more of these constants ORed together: 420 The $eventmask can be one or more of these constants ORed together:
181 421
182 EV::READ wait until read() wouldn't block anymore 422 EV::READ wait until read() wouldn't block anymore
183 EV::WRITE wait until write() wouldn't block anymore 423 EV::WRITE wait until write() wouldn't block anymore
… …
195 435
196 $current_eventmask = $w->events 436 $current_eventmask = $w->events
197 $old_eventmask = $w->events ($new_eventmask) 437 $old_eventmask = $w->events ($new_eventmask)
198 Returns the previously set event mask and optionally set a new one. 438 Returns the previously set event mask and optionally set a new one.
199 439
440 TIMER WATCHERS - relative and optionally repeating timeouts
200 $w = EV::timer $after, $repeat, $callback 441 $w = EV::timer $after, $repeat, $callback
201 $w = EV::timer_ns $after, $repeat, $callback 442 $w = EV::timer_ns $after, $repeat, $callback
202 Calls the callback after $after seconds. If $repeat is non-zero, the 443 $w = $loop->timer ($after, $repeat, $callback)
203 timer will be restarted (with the $repeat value as $after) after the 444 $w = $loop->timer_ns ($after, $repeat, $callback)
204 callback returns. 445 Calls the callback after $after seconds (which may be fractional).
446 If $repeat is non-zero, the timer will be restarted (with the
447 $repeat value as $after) after the callback returns.
205 448
206 This means that the callback would be called roughly after $after 449 This means that the callback would be called roughly after $after
207 seconds, and then every $repeat seconds. The timer does his best not 450 seconds, and then every $repeat seconds. The timer does his best not
208 to drift, but it will not invoke the timer more often then once per 451 to drift, but it will not invoke the timer more often then once per
209 event loop iteration, and might drift in other cases. If that isn't 452 event loop iteration, and might drift in other cases. If that isn't
… …
218 The "timer_ns" variant doesn't start (activate) the newly created 461 The "timer_ns" variant doesn't start (activate) the newly created
219 watcher. 462 watcher.
220 463
221 $w->set ($after, $repeat) 464 $w->set ($after, $repeat)
222 Reconfigures the watcher, see the constructor above for details. Can 465 Reconfigures the watcher, see the constructor above for details. Can
223 be at any time. 466 be called at any time.
224 467
225 $w->again 468 $w->again
226 Similar to the "start" method, but has special semantics for 469 Similar to the "start" method, but has special semantics for
227 repeating timers: 470 repeating timers:
228 471
… …
239 This behaviour is useful when you have a timeout for some IO 482 This behaviour is useful when you have a timeout for some IO
240 operation. You create a timer object with the same value for $after 483 operation. You create a timer object with the same value for $after
241 and $repeat, and then, in the read/write watcher, run the "again" 484 and $repeat, and then, in the read/write watcher, run the "again"
242 method on the timeout. 485 method on the timeout.
243 486
487 PERIODIC WATCHERS - to cron or not to cron?
244 $w = EV::periodic $at, $interval, $reschedule_cb, $callback 488 $w = EV::periodic $at, $interval, $reschedule_cb, $callback
245 $w = EV::periodic_ns $at, $interval, $reschedule_cb, $callback 489 $w = EV::periodic_ns $at, $interval, $reschedule_cb, $callback
490 $w = $loop->periodic ($at, $interval, $reschedule_cb, $callback)
491 $w = $loop->periodic_ns ($at, $interval, $reschedule_cb, $callback)
246 Similar to EV::timer, but is not based on relative timeouts but on 492 Similar to EV::timer, but is not based on relative timeouts but on
247 absolute times. Apart from creating "simple" timers that trigger 493 absolute times. Apart from creating "simple" timers that trigger
248 "at" the specified time, it can also be used for non-drifting 494 "at" the specified time, it can also be used for non-drifting
249 absolute timers and more complex, cron-like, setups that are not 495 absolute timers and more complex, cron-like, setups that are not
250 adversely affected by time jumps (i.e. when the system clock is 496 adversely affected by time jumps (i.e. when the system clock is
251 changed by explicit date -s or other means such as ntpd). It is also 497 changed by explicit date -s or other means such as ntpd). It is also
252 the most complex watcher type in EV. 498 the most complex watcher type in EV.
253 499
254 It has three distinct "modes": 500 It has three distinct "modes":
255 501
256 * absolute timer ($interval = $reschedule_cb = 0) 502 * absolute timer ($interval = $reschedule_cb = 0)
503
257 This time simply fires at the wallclock time $at and doesn't 504 This time simply fires at the wallclock time $at and doesn't
258 repeat. It will not adjust when a time jump occurs, that is, if 505 repeat. It will not adjust when a time jump occurs, that is, if
259 it is to be run at January 1st 2011 then it will run when the 506 it is to be run at January 1st 2011 then it will run when the
260 system time reaches or surpasses this time. 507 system time reaches or surpasses this time.
261 508
262 * non-repeating interval timer ($interval > 0, $reschedule_cb = 0) 509 * repeating interval timer ($interval > 0, $reschedule_cb = 0)
510
263 In this mode the watcher will always be scheduled to time out at 511 In this mode the watcher will always be scheduled to time out at
264 the next "$at + N * $interval" time (for some integer N) and 512 the next "$at + N * $interval" time (for some integer N) and
265 then repeat, regardless of any time jumps. 513 then repeat, regardless of any time jumps.
266 514
267 This can be used to create timers that do not drift with respect 515 This can be used to create timers that do not drift with respect
… …
276 Another way to think about it (for the mathematically inclined) 524 Another way to think about it (for the mathematically inclined)
277 is that EV::periodic will try to run the callback in this mode 525 is that EV::periodic will try to run the callback in this mode
278 at the next possible time where "$time = $at (mod $interval)", 526 at the next possible time where "$time = $at (mod $interval)",
279 regardless of any time jumps. 527 regardless of any time jumps.
280 528
281 * manual reschedule mode ($reschedule_cb = coderef) 529 * manual reschedule mode ($reschedule_cb = coderef)
530
282 In this mode $interval and $at are both being ignored. Instead, 531 In this mode $interval and $at are both being ignored. Instead,
283 each time the periodic watcher gets scheduled, the reschedule 532 each time the periodic watcher gets scheduled, the reschedule
284 callback ($reschedule_cb) will be called with the watcher as 533 callback ($reschedule_cb) will be called with the watcher as
285 first, and the current time as second argument. 534 first, and the current time as second argument.
286 535
287 *This callback MUST NOT stop or destroy this or any other 536 *This callback MUST NOT stop or destroy this or any other
537 periodic watcher, ever, and MUST NOT call any event loop
288 periodic watcher, ever*. If you need to stop it, return 1e30 and 538 functions or methods*. If you need to stop it, return 1e30 and
289 stop it afterwards. 539 stop it afterwards. You may create and start a "EV::prepare"
540 watcher for this task.
290 541
291 It must return the next time to trigger, based on the passed 542 It must return the next time to trigger, based on the passed
292 time value (that is, the lowest time value larger than to the 543 time value (that is, the lowest time value larger than or equal
293 second argument). It will usually be called just before the 544 to to the second argument). It will usually be called just
294 callback will be triggered, but might be called at other times, 545 before the callback will be triggered, but might be called at
295 too. 546 other times, too.
296 547
297 This can be used to create very complex timers, such as a timer 548 This can be used to create very complex timers, such as a timer
298 that triggers on each midnight, local time (actually 24 hours 549 that triggers on each midnight, local time (actually 24 hours
299 after the last midnight, to keep the example simple. If you know 550 after the last midnight, to keep the example simple. If you know
300 a way to do it correctly in about the same space (without 551 a way to do it correctly in about the same space (without
… …
313 The "periodic_ns" variant doesn't start (activate) the newly created 564 The "periodic_ns" variant doesn't start (activate) the newly created
314 watcher. 565 watcher.
315 566
316 $w->set ($at, $interval, $reschedule_cb) 567 $w->set ($at, $interval, $reschedule_cb)
317 Reconfigures the watcher, see the constructor above for details. Can 568 Reconfigures the watcher, see the constructor above for details. Can
318 be at any time. 569 be called at any time.
319 570
320 $w->again 571 $w->again
321 Simply stops and starts the watcher again. 572 Simply stops and starts the watcher again.
322 573
574 $time = $w->at
575 Return the time that the watcher is expected to trigger next.
576
577 SIGNAL WATCHERS - signal me when a signal gets signalled!
323 $w = EV::signal $signal, $callback 578 $w = EV::signal $signal, $callback
324 $w = EV::signal_ns $signal, $callback 579 $w = EV::signal_ns $signal, $callback
580 $w = $loop->signal ($signal, $callback)
581 $w = $loop->signal_ns ($signal, $callback)
325 Call the callback when $signal is received (the signal can be 582 Call the callback when $signal is received (the signal can be
326 specified by number or by name, just as with kill or %SIG). 583 specified by number or by name, just as with "kill" or %SIG).
584
585 Only one event loop can grab a given signal - attempting to grab the
586 same signal from two EV loops will crash the program immediately or
587 cause data corruption.
327 588
328 EV will grab the signal for the process (the kernel only allows one 589 EV will grab the signal for the process (the kernel only allows one
329 component to receive a signal at a time) when you start a signal 590 component to receive a signal at a time) when you start a signal
330 watcher, and removes it again when you stop it. Perl does the same 591 watcher, and removes it again when you stop it. Perl does the same
331 when you add/remove callbacks to %SIG, so watch out. 592 when you add/remove callbacks to %SIG, so watch out.
… …
335 The "signal_ns" variant doesn't start (activate) the newly created 596 The "signal_ns" variant doesn't start (activate) the newly created
336 watcher. 597 watcher.
337 598
338 $w->set ($signal) 599 $w->set ($signal)
339 Reconfigures the watcher, see the constructor above for details. Can 600 Reconfigures the watcher, see the constructor above for details. Can
340 be at any time. 601 be called at any time.
341 602
342 $current_signum = $w->signal 603 $current_signum = $w->signal
343 $old_signum = $w->signal ($new_signal) 604 $old_signum = $w->signal ($new_signal)
344 Returns the previously set signal (always as a number not name) and 605 Returns the previously set signal (always as a number not name) and
345 optionally set a new one. 606 optionally set a new one.
346 607
608 CHILD WATCHERS - watch out for process status changes
347 $w = EV::child $pid, $callback 609 $w = EV::child $pid, $trace, $callback
348 $w = EV::child_ns $pid, $callback 610 $w = EV::child_ns $pid, $trace, $callback
611 $w = $loop->child ($pid, $trace, $callback)
612 $w = $loop->child_ns ($pid, $trace, $callback)
349 Call the callback when a status change for pid $pid (or any pid if 613 Call the callback when a status change for pid $pid (or any pid if
350 $pid is 0) has been received. More precisely: when the process 614 $pid is 0) has been received (a status change happens when the
615 process terminates or is killed, or, when trace is true,
616 additionally when it is stopped or continued). More precisely: when
351 receives a SIGCHLD, EV will fetch the outstanding exit/wait status 617 the process receives a "SIGCHLD", EV will fetch the outstanding
352 for all changed/zombie children and call the callback. 618 exit/wait status for all changed/zombie children and call the
619 callback.
353 620
354 You can access both status and pid by using the "rstatus" and "rpid" 621 It is valid (and fully supported) to install a child watcher after a
622 child has exited but before the event loop has started its next
623 iteration (for example, first you "fork", then the new child process
624 might exit, and only then do you install a child watcher in the
625 parent for the new pid).
626
627 You can access both exit (or tracing) status and pid by using the
355 methods on the watcher object. 628 "rstatus" and "rpid" methods on the watcher object.
356 629
357 You can have as many pid watchers per pid as you want. 630 You can have as many pid watchers per pid as you want, they will all
631 be called.
358 632
359 The "child_ns" variant doesn't start (activate) the newly created 633 The "child_ns" variant doesn't start (activate) the newly created
360 watcher. 634 watcher.
361 635
362 $w->set ($pid) 636 $w->set ($pid, $trace)
363 Reconfigures the watcher, see the constructor above for details. Can 637 Reconfigures the watcher, see the constructor above for details. Can
364 be at any time. 638 be called at any time.
365 639
366 $current_pid = $w->pid 640 $current_pid = $w->pid
367 $old_pid = $w->pid ($new_pid)
368 Returns the previously set process id and optionally set a new one. 641 Returns the previously set process id and optionally set a new one.
369 642
370 $exit_status = $w->rstatus 643 $exit_status = $w->rstatus
371 Return the exit/wait status (as returned by waitpid, see the waitpid 644 Return the exit/wait status (as returned by waitpid, see the waitpid
372 entry in perlfunc). 645 entry in perlfunc).
373 646
374 $pid = $w->rpid 647 $pid = $w->rpid
375 Return the pid of the awaited child (useful when you have installed 648 Return the pid of the awaited child (useful when you have installed
376 a watcher for all pids). 649 a watcher for all pids).
377 650
651 STAT WATCHERS - did the file attributes just change?
652 $w = EV::stat $path, $interval, $callback
653 $w = EV::stat_ns $path, $interval, $callback
654 $w = $loop->stat ($path, $interval, $callback)
655 $w = $loop->stat_ns ($path, $interval, $callback)
656 Call the callback when a file status change has been detected on
657 $path. The $path does not need to exist, changing from "path exists"
658 to "path does not exist" is a status change like any other.
659
660 The $interval is a recommended polling interval for systems where
661 OS-supported change notifications don't exist or are not supported.
662 If you use 0 then an unspecified default is used (which is highly
663 recommended!), which is to be expected to be around five seconds
664 usually.
665
666 This watcher type is not meant for massive numbers of stat watchers,
667 as even with OS-supported change notifications, this can be
668 resource-intensive.
669
670 The "stat_ns" variant doesn't start (activate) the newly created
671 watcher.
672
673 ... = $w->stat
674 This call is very similar to the perl "stat" built-in: It stats
675 (using "lstat") the path specified in the watcher and sets perls
676 stat cache (as well as EV's idea of the current stat values) to the
677 values found.
678
679 In scalar context, a boolean is return indicating success or failure
680 of the stat. In list context, the same 13-value list as with stat is
681 returned (except that the blksize and blocks fields are not
682 reliable).
683
684 In the case of an error, errno is set to "ENOENT" (regardless of the
685 actual error value) and the "nlink" value is forced to zero (if the
686 stat was successful then nlink is guaranteed to be non-zero).
687
688 See also the next two entries for more info.
689
690 ... = $w->attr
691 Just like "$w->stat", but without the initial stat'ing: this returns
692 the values most recently detected by EV. See the next entry for more
693 info.
694
695 ... = $w->prev
696 Just like "$w->stat", but without the initial stat'ing: this returns
697 the previous set of values, before the change.
698
699 That is, when the watcher callback is invoked, "$w->prev" will be
700 set to the values found *before* a change was detected, while
701 "$w->attr" returns the values found leading to the change detection.
702 The difference (if any) between "prev" and "attr" is what triggered
703 the callback.
704
705 If you did something to the filesystem object and do not want to
706 trigger yet another change, you can call "stat" to update EV's idea
707 of what the current attributes are.
708
709 $w->set ($path, $interval)
710 Reconfigures the watcher, see the constructor above for details. Can
711 be called at any time.
712
713 $current_path = $w->path
714 $old_path = $w->path ($new_path)
715 Returns the previously set path and optionally set a new one.
716
717 $current_interval = $w->interval
718 $old_interval = $w->interval ($new_interval)
719 Returns the previously set interval and optionally set a new one.
720 Can be used to query the actual interval used.
721
722 IDLE WATCHERS - when you've got nothing better to do...
378 $w = EV::idle $callback 723 $w = EV::idle $callback
379 $w = EV::idle_ns $callback 724 $w = EV::idle_ns $callback
725 $w = $loop->idle ($callback)
726 $w = $loop->idle_ns ($callback)
380 Call the callback when there are no pending io, timer/periodic, 727 Call the callback when there are no other pending watchers of the
381 signal or child events, i.e. when the process is idle. 728 same or higher priority (excluding check, prepare and other idle
729 watchers of the same or lower priority, of course). They are called
730 idle watchers because when the watcher is the highest priority
731 pending event in the process, the process is considered to be idle
732 at that priority.
733
734 If you want a watcher that is only ever called when *no* other
735 events are outstanding you have to set the priority to "EV::MINPRI".
382 736
383 The process will not block as long as any idle watchers are active, 737 The process will not block as long as any idle watchers are active,
384 and they will be called repeatedly until stopped. 738 and they will be called repeatedly until stopped.
385 739
740 For example, if you have idle watchers at priority 0 and 1, and an
741 I/O watcher at priority 0, then the idle watcher at priority 1 and
742 the I/O watcher will always run when ready. Only when the idle
743 watcher at priority 1 is stopped and the I/O watcher at priority 0
744 is not pending with the 0-priority idle watcher be invoked.
745
386 The "idle_ns" variant doesn't start (activate) the newly created 746 The "idle_ns" variant doesn't start (activate) the newly created
387 watcher. 747 watcher.
388 748
749 PREPARE WATCHERS - customise your event loop!
389 $w = EV::prepare $callback 750 $w = EV::prepare $callback
390 $w = EV::prepare_ns $callback 751 $w = EV::prepare_ns $callback
752 $w = $loop->prepare ($callback)
753 $w = $loop->prepare_ns ($callback)
391 Call the callback just before the process would block. You can still 754 Call the callback just before the process would block. You can still
392 create/modify any watchers at this point. 755 create/modify any watchers at this point.
393 756
394 See the EV::check watcher, below, for explanations and an example. 757 See the EV::check watcher, below, for explanations and an example.
395 758
396 The "prepare_ns" variant doesn't start (activate) the newly created 759 The "prepare_ns" variant doesn't start (activate) the newly created
397 watcher. 760 watcher.
398 761
762 CHECK WATCHERS - customise your event loop even more!
399 $w = EV::check $callback 763 $w = EV::check $callback
400 $w = EV::check_ns $callback 764 $w = EV::check_ns $callback
765 $w = $loop->check ($callback)
766 $w = $loop->check_ns ($callback)
401 Call the callback just after the process wakes up again (after it 767 Call the callback just after the process wakes up again (after it
402 has gathered events), but before any other callbacks have been 768 has gathered events), but before any other callbacks have been
403 invoked. 769 invoked.
404 770
405 This is used to integrate other event-based software into the EV 771 This is used to integrate other event-based software into the EV
… …
414 # do nothing unless active 780 # do nothing unless active
415 $dispatcher->{_event_queue_h} 781 $dispatcher->{_event_queue_h}
416 or return; 782 or return;
417 783
418 # make the dispatcher handle any outstanding stuff 784 # make the dispatcher handle any outstanding stuff
785 ... not shown
419 786
420 # create an IO watcher for each and every socket 787 # create an I/O watcher for each and every socket
421 @snmp_watcher = ( 788 @snmp_watcher = (
422 (map { EV::io $_, EV::READ, sub { } } 789 (map { EV::io $_, EV::READ, sub { } }
423 keys %{ $dispatcher->{_descriptors} }), 790 keys %{ $dispatcher->{_descriptors} }),
791
792 EV::timer +($event->[Net::SNMP::Dispatcher::_ACTIVE]
793 ? $event->[Net::SNMP::Dispatcher::_TIME] - EV::now : 0),
794 0, sub { },
424 ); 795 );
425
426 # if there are any timeouts, also create a timer
427 push @snmp_watcher, EV::timer $event->[Net::SNMP::Dispatcher::_TIME] - EV::now, 0, sub { }
428 if $event->[Net::SNMP::Dispatcher::_ACTIVE];
429 }; 796 };
430 797
431 The callbacks are irrelevant, the only purpose of those watchers is 798 The callbacks are irrelevant (and are not even being called), the
432 to wake up the process as soon as one of those events occurs (socket 799 only purpose of those watchers is to wake up the process as soon as
433 readable, or timer timed out). The corresponding EV::check watcher 800 one of those events occurs (socket readable, or timer timed out).
434 will then clean up: 801 The corresponding EV::check watcher will then clean up:
435 802
436 our $snmp_check = EV::check sub { 803 our $snmp_check = EV::check sub {
437 # destroy all watchers 804 # destroy all watchers
438 @snmp_watcher = (); 805 @snmp_watcher = ();
439 806
440 # make the dispatcher handle any new stuff 807 # make the dispatcher handle any new stuff
808 ... not shown
441 }; 809 };
442 810
443 The callbacks of the created watchers will not be called as the 811 The callbacks of the created watchers will not be called as the
444 watchers are destroyed before this cna happen (remember EV::check 812 watchers are destroyed before this can happen (remember EV::check
445 gets called first). 813 gets called first).
446 814
447 The "check_ns" variant doesn't start (activate) the newly created 815 The "check_ns" variant doesn't start (activate) the newly created
448 watcher. 816 watcher.
449 817
818 FORK WATCHERS - the audacity to resume the event loop after a fork
819 Fork watchers are called when a "fork ()" was detected. The invocation
820 is done before the event loop blocks next and before "check" watchers
821 are being called, and only in the child after the fork.
822
823 $w = EV::fork $callback
824 $w = EV::fork_ns $callback
825 $w = $loop->fork ($callback)
826 $w = $loop->fork_ns ($callback)
827 Call the callback before the event loop is resumed in the child
828 process after a fork.
829
830 The "fork_ns" variant doesn't start (activate) the newly created
831 watcher.
832
833 EMBED WATCHERS - when one backend isn't enough...
834 This is a rather advanced watcher type that lets you embed one event
835 loop into another (currently only IO events are supported in the
836 embedded loop, other types of watchers might be handled in a delayed or
837 incorrect fashion and must not be used).
838
839 See the libev documentation at
840 <http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod#code_ev_embed_code
841 _when_one_backend_> (locally installed as EV::libev) for more details.
842
843 In short, this watcher is most useful on BSD systems without working
844 kqueue to still be able to handle a large number of sockets:
845
846 my $socket_loop;
847
848 # check wether we use SELECT or POLL _and_ KQUEUE is supported
849 if (
850 (EV::backend & (EV::BACKEND_POLL | EV::BACKEND_SELECT))
851 && (EV::supported_backends & EV::embeddable_backends & EV::BACKEND_KQUEUE)
852 ) {
853 # use kqueue for sockets
854 $socket_loop = new EV::Loop EV::BACKEND_KQUEUE | EV::FLAG_NOENV;
855 }
856
857 # use the default loop otherwise
858 $socket_loop ||= EV::default_loop;
859
860 $w = EV::embed $otherloop[, $callback]
861 $w = EV::embed_ns $otherloop[, $callback]
862 $w = $loop->embed ($otherloop[, $callback])
863 $w = $loop->embed_ns ($otherloop[, $callback])
864 Call the callback when the embedded event loop ($otherloop) has any
865 I/O activity. The $callback is optional: if it is missing, then the
866 embedded event loop will be managed automatically (which is
867 recommended), otherwise you have to invoke "sweep" yourself.
868
869 The "embed_ns" variant doesn't start (activate) the newly created
870 watcher.
871
872 ASYNC WATCHERS - how to wake up another event loop
873 Async watchers are provided by EV, but have little use in perl directly,
874 as perl neither supports threads running in parallel nor direct access
875 to signal handlers or other contexts where they could be of value.
876
877 It is, however, possible to use them from the XS level.
878
879 Please see the libev documentation for further details.
880
881 $w = EV::async $callback
882 $w = EV::async_ns $callback
883 $w->send
884 $bool = $w->async_pending
885
886PERL SIGNALS
887 While Perl signal handling (%SIG) is not affected by EV, the behaviour
888 with EV is as the same as any other C library: Perl-signals will only be
889 handled when Perl runs, which means your signal handler might be invoked
890 only the next time an event callback is invoked.
891
892 The solution is to use EV signal watchers (see "EV::signal"), which will
893 ensure proper operations with regards to other event watchers.
894
895 If you cannot do this for whatever reason, you can also force a watcher
896 to be called on every event loop iteration by installing a "EV::check"
897 watcher:
898
899 my $async_check = EV::check sub { };
900
901 This ensures that perl gets into control for a short time to handle any
902 pending signals, and also ensures (slightly) slower overall operation.
903
450THREADS 904ITHREADS
451 Threads are not supported by this in any way. Perl pseudo-threads is 905 Ithreads are not supported by this module in any way. Perl
452 evil stuff and must die. 906 pseudo-threads is evil stuff and must die. Real threads as provided by
907 Coro are fully supported (and enhanced support is available via
908 Coro::EV).
909
910FORK
911 Most of the "improved" event delivering mechanisms of modern operating
912 systems have quite a few problems with fork(2) (to put it bluntly: it is
913 not supported and usually destructive). Libev makes it possible to work
914 around this by having a function that recreates the kernel state after
915 fork in the child.
916
917 On non-win32 platforms, this module requires the pthread_atfork
918 functionality to do this automatically for you. This function is quite
919 buggy on most BSDs, though, so YMMV. The overhead for this is quite
920 negligible, because everything the function currently does is set a flag
921 that is checked only when the event loop gets used the next time, so
922 when you do fork but not use EV, the overhead is minimal.
923
924 On win32, there is no notion of fork so all this doesn't apply, of
925 course.
453 926
454SEE ALSO 927SEE ALSO
455 L<EV::DNS>, L<EV::AnyEvent>. 928 EV::ADNS (asynchronous DNS), Glib::EV (makes Glib/Gtk2 use EV as event
929 loop), EV::Glib (embed Glib into EV), Coro::EV (efficient coroutines
930 with EV), Net::SNMP::EV (asynchronous SNMP), AnyEvent for event-loop
931 agnostic and portable event driven programming.
456 932
457AUTHOR 933AUTHOR
458 Marc Lehmann <schmorp@schmorp.de> 934 Marc Lehmann <schmorp@schmorp.de>
459 http://home.schmorp.de/ 935 http://home.schmorp.de/
460 936

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