ViewVC Help
View File | Revision Log | Show Annotations | Download File
/cvs/EV/README
(Generate patch)

Comparing EV/README (file contents):
Revision 1.7 by root, Sat Nov 3 16:25:49 2007 UTC vs.
Revision 1.28 by root, Tue Jul 8 18:56:48 2008 UTC

1NAME 1NAME
2 EV - perl interface to libev, a high performance full-featured event 2 EV - perl interface to libev, a high performance full-featured event
3 loop 3 loop
4 4
5SYNOPSIS 5SYNOPSIS
6 use EV; 6 use EV;
7 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 23
24 # IO 24 # IO
25 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
37 my $w = EV::signal 3, sub {
38 warn "sigquit received (this is GNU/Linux, right?)\n";
39 }; 36
40
41 # CHILD/PID STATUS CHANGES 37 # CHILD/PID STATUS CHANGES
42 38
43 my $w = EV::child 666, sub { 39 my $w = EV::child 666, 0, sub {
44 my ($w, $revents) = @_; 40 my ($w, $revents) = @_;
45 # my $pid = $w->rpid;
46 my $status = $w->rstatus; 41 my $status = $w->rstatus;
47 }; 42 };
48 43
44 # STAT CHANGES
45 my $w = EV::stat "/etc/passwd", 10, sub {
46 my ($w, $revents) = @_;
47 warn $w->path, " has changed somehow.\n";
48 };
49
49 # MAINLOOP 50 # MAINLOOP
50 EV::loop; # loop until EV::loop_done is called 51 EV::loop; # loop until EV::unloop is called or all watchers stop
51 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
52 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
53 54
54DESCRIPTION 55DESCRIPTION
55 This module provides an interface to libev 56 This module provides an interface to libev
56 (<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 If you want to take avdantage of kqueue (which often works properly for
87 sockets only) even though the default loop doesn't enable it, you can
88 *embed* a kqueue loop into the default loop: running the default loop
89 will then also service the kqueue loop to some extent. See the example
90 in the section about embed watchers for an example on how to achieve
91 that.
92
93 $loop = new EV::loop [$flags]
94 Create a new event loop as per the specified flags. Please refer to
95 the "ev_loop_new ()" function description in the libev documentation
96 (<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod#GLOBAL_FUNCTI
97 ONS>) for more info.
98
99 The loop will automatically be destroyed when it is no longer
100 referenced by any watcher and the loop object goes out of scope.
101
102 Using "EV::FLAG_FORKCHECK" is recommended, as only the default event
103 loop is protected by this module.
104
105 $loop->loop_fork
106 Must be called after a fork in the child, before entering or
107 continuing the event loop. An alternative is to use
108 "EV::FLAG_FORKCHECK" which calls this function automatically, at
109 some performance loss (refer to the libev documentation).
110
111 $loop->loop_verify
112 Calls "ev_verify" to make internal consistency checks (for debugging
113 libev) and abort the program if any data structures were found to be
114 corrupted.
115
116 $loop = EV::default_loop [$flags]
117 Return the default loop (which is a singleton object). Since this
118 module already creates the default loop with default flags,
119 specifying flags here will not have any effect unless you destroy
120 the default loop first, which isn't supported. So in short: don't do
121 it, and if you break it, you get to keep the pieces.
57 122
58BASIC INTERFACE 123BASIC INTERFACE
59 $EV::DIED 124 $EV::DIED
60 Must contain a reference to a function that is called when a 125 Must contain a reference to a function that is called when a
61 callback throws an exception (with $@ containing thr error). The 126 callback throws an exception (with $@ containing the error). The
62 default prints an informative message and continues. 127 default prints an informative message and continues.
63 128
64 If this callback throws an exception it will be silently ignored. 129 If this callback throws an exception it will be silently ignored.
130
131 $flags = EV::supported_backends
132 $flags = EV::recommended_backends
133 $flags = EV::embeddable_backends
134 Returns the set (see "EV::BACKEND_*" flags) of backends supported by
135 this instance of EV, the set of recommended backends (supposed to be
136 good) for this platform and the set of embeddable backends (see
137 EMBED WATCHERS).
138
139 EV::sleep $seconds
140 Block the process for the given number of (fractional) seconds.
65 141
66 $time = EV::time 142 $time = EV::time
67 Returns the current time in (fractional) seconds since the epoch. 143 Returns the current time in (fractional) seconds since the epoch.
68 144
69 $time = EV::now 145 $time = EV::now
146 $time = $loop->now
70 Returns the time the last event loop iteration has been started. 147 Returns the time the last event loop iteration has been started.
71 This is the time that (relative) timers are based on, and refering 148 This is the time that (relative) timers are based on, and refering
72 to it is usually faster then calling EV::time. 149 to it is usually faster then calling EV::time.
73 150
74 $method = EV::ev_method 151 $backend = EV::backend
152 $backend = $loop->backend
75 Returns an integer describing the backend used by libev 153 Returns an integer describing the backend used by libev
76 (EV::METHOD_SELECT or EV::METHOD_EPOLL). 154 (EV::METHOD_SELECT or EV::METHOD_EPOLL).
77 155
78 EV::loop [$flags] 156 EV::loop [$flags]
157 $loop->loop ([$flags])
79 Begin checking for events and calling callbacks. It returns when a 158 Begin checking for events and calling callbacks. It returns when a
80 callback calls EV::loop_done. 159 callback calls EV::unloop.
81 160
82 The $flags argument can be one of the following: 161 The $flags argument can be one of the following:
83 162
84 0 as above 163 0 as above
85 EV::LOOP_ONESHOT block at most once (wait, but do not loop) 164 EV::LOOP_ONESHOT block at most once (wait, but do not loop)
86 EV::LOOP_NONBLOCK do not block at all (fetch/handle events but do not wait) 165 EV::LOOP_NONBLOCK do not block at all (fetch/handle events but do not wait)
87 166
88 EV::loop_done [$how] 167 EV::unloop [$how]
168 $loop->unloop ([$how])
89 When called with no arguments or an argument of 1, makes the 169 When called with no arguments or an argument of EV::UNLOOP_ONE,
90 innermost call to EV::loop return. 170 makes the innermost call to EV::loop return.
91 171
92 When called with an agrument of 2, all calls to EV::loop will return 172 When called with an argument of EV::UNLOOP_ALL, all calls to
93 as fast as possible. 173 EV::loop will return as fast as possible.
94 174
95 WATCHER 175 $count = EV::loop_count
176 $count = $loop->loop_count
177 Return the number of times the event loop has polled for new events.
178 Sometiems useful as a generation counter.
179
180 EV::once $fh_or_undef, $events, $timeout, $cb->($revents)
181 $loop->once ($fh_or_undef, $events, $timeout, $cb->($revents))
182 This function rolls together an I/O and a timer watcher for a single
183 one-shot event without the need for managing a watcher object.
184
185 If $fh_or_undef is a filehandle or file descriptor, then $events
186 must be a bitset containing either "EV::READ", "EV::WRITE" or
187 "EV::READ | EV::WRITE", indicating the type of I/O event you want to
188 wait for. If you do not want to wait for some I/O event, specify
189 "undef" for $fh_or_undef and 0 for $events).
190
191 If timeout is "undef" or negative, then there will be no timeout.
192 Otherwise a EV::timer with this value will be started.
193
194 When an error occurs or either the timeout or I/O watcher triggers,
195 then the callback will be called with the received event set (in
196 general you can expect it to be a combination of "EV::ERROR",
197 "EV::READ", "EV::WRITE" and "EV::TIMEOUT").
198
199 EV::once doesn't return anything: the watchers stay active till
200 either of them triggers, then they will be stopped and freed, and
201 the callback invoked.
202
203 EV::feed_fd_event ($fd, $revents)
204 $loop->feed_fd_event ($fd, $revents)
205 Feed an event on a file descriptor into EV. EV will react to this
206 call as if the readyness notifications specified by $revents (a
207 combination of "EV::READ" and "EV::WRITE") happened on the file
208 descriptor $fd.
209
210 EV::feed_signal_event ($signal)
211 Feed a signal event into EV. EV will react to this call as if the
212 signal specified by $signal had occured.
213
214 EV::set_io_collect_interval $time
215 $loop->set_io_collect_interval ($time)
216 EV::set_timeout_collect_interval $time
217 $loop->set_timeout_collect_interval ($time)
218 These advanced functions set the minimum block interval when polling
219 for I/O events and the minimum wait interval for timer events. See
220 the libev documentation at
221 <http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod#FUNCTIONS_CONT
222 ROLLING_THE_EVENT_LOOP> for a more detailed discussion.
223
224WATCHER OBJECTS
96 A watcher is an object that gets created to record your interest in some 225 A watcher is an object that gets created to record your interest in some
97 event. For instance, if you want to wait for STDIN to become readable, 226 event. For instance, if you want to wait for STDIN to become readable,
98 you would create an EV::io watcher for that: 227 you would create an EV::io watcher for that:
99 228
100 my $watcher = EV::io *STDIN, EV::READ, sub { 229 my $watcher = EV::io *STDIN, EV::READ, sub {
101 my ($watcher, $revents) = @_; 230 my ($watcher, $revents) = @_;
102 warn "yeah, STDIN should not be readable without blocking!\n" 231 warn "yeah, STDIN should now be readable without blocking!\n"
103 }; 232 };
104 233
105 All watchers can be active (waiting for events) or inactive (paused). 234 All watchers can be active (waiting for events) or inactive (paused).
106 Only active watchers will have their callbacks invoked. All callbacks 235 Only active watchers will have their callbacks invoked. All callbacks
107 will be called with at least two arguments: the watcher and a bitmask of 236 will be called with at least two arguments: the watcher and a bitmask of
108 received events. 237 received events.
109 238
110 Each watcher type has its associated bit in revents, so you can use the 239 Each watcher type has its associated bit in revents, so you can use the
111 same callback for multiple watchers. The event mask is named after the 240 same callback for multiple watchers. The event mask is named after the
112 type, i..e. EV::child sets EV::CHILD, EV::prepare sets EV::PREPARE, 241 type, i..e. EV::child sets EV::CHILD, EV::prepare sets EV::PREPARE,
113 EV::periodic sets EV::PERIODIC and so on, with the exception of IO 242 EV::periodic sets EV::PERIODIC and so on, with the exception of I/O
114 events (which can set both EV::READ and EV::WRITE bits), and EV::timer 243 events (which can set both EV::READ and EV::WRITE bits), and EV::timer
115 (which uses EV::TIMEOUT). 244 (which uses EV::TIMEOUT).
116 245
117 In the rare case where one wants to create a watcher but not start it at 246 In the rare case where one wants to create a watcher but not start it at
118 the same time, each constructor has a variant with a trailing "_ns" in 247 the same time, each constructor has a variant with a trailing "_ns" in
… …
124 253
125 Also, all methods changing some aspect of a watcher (->set, ->priority, 254 Also, all methods changing some aspect of a watcher (->set, ->priority,
126 ->fh and so on) automatically stop and start it again if it is active, 255 ->fh and so on) automatically stop and start it again if it is active,
127 which means pending events get lost. 256 which means pending events get lost.
128 257
129 WATCHER TYPES 258 COMMON WATCHER METHODS
130 Now lets move to the existing watcher types and asociated methods. 259 This section lists methods common to all watchers.
131
132 The following methods are available for all watchers. Then followes a
133 description of each watcher constructor (EV::io, EV::timer,
134 EV::periodic, EV::signal, EV::child, EV::idle, EV::prepare and
135 EV::check), followed by any type-specific methods (if any).
136 260
137 $w->start 261 $w->start
138 Starts a watcher if it isn't active already. Does nothing to an 262 Starts a watcher if it isn't active already. Does nothing to an
139 already active watcher. By default, all watchers start out in the 263 already active watcher. By default, all watchers start out in the
140 active state (see the description of the "_ns" variants if you need 264 active state (see the description of the "_ns" variants if you need
141 stopped watchers). 265 stopped watchers).
142 266
143 $w->stop 267 $w->stop
144 Stop a watcher if it is active. Also clear any pending events 268 Stop a watcher if it is active. Also clear any pending events
145 (events that have been received but that didn't yet result in a 269 (events that have been received but that didn't yet result in a
146 callback invocation), regardless of wether the watcher was active or 270 callback invocation), regardless of whether the watcher was active
147 not. 271 or not.
148 272
149 $bool = $w->is_active 273 $bool = $w->is_active
150 Returns true if the watcher is active, false otherwise. 274 Returns true if the watcher is active, false otherwise.
275
276 $current_data = $w->data
277 $old_data = $w->data ($new_data)
278 Queries a freely usable data scalar on the watcher and optionally
279 changes it. This is a way to associate custom data with a watcher:
280
281 my $w = EV::timer 60, 0, sub {
282 warn $_[0]->data;
283 };
284 $w->data ("print me!");
151 285
152 $current_cb = $w->cb 286 $current_cb = $w->cb
153 $old_cb = $w->cb ($new_cb) 287 $old_cb = $w->cb ($new_cb)
154 Queries the callback on the watcher and optionally changes it. You 288 Queries the callback on the watcher and optionally changes it. You
155 can do this at any time without the watcher restarting. 289 can do this at any time without the watcher restarting.
… …
160 Pending watchers with higher priority will be invoked first. The 294 Pending watchers with higher priority will be invoked first. The
161 valid range of priorities lies between EV::MAXPRI (default 2) and 295 valid range of priorities lies between EV::MAXPRI (default 2) and
162 EV::MINPRI (default -2). If the priority is outside this range it 296 EV::MINPRI (default -2). If the priority is outside this range it
163 will automatically be normalised to the nearest valid priority. 297 will automatically be normalised to the nearest valid priority.
164 298
165 The default priority of any newly-created weatcher is 0. 299 The default priority of any newly-created watcher is 0.
166 300
301 Note that the priority semantics have not yet been fleshed out and
302 are subject to almost certain change.
303
167 $w->trigger ($revents) 304 $w->invoke ($revents)
168 Call the callback *now* with the given event mask. 305 Call the callback *now* with the given event mask.
169 306
307 $w->feed_event ($revents)
308 Feed some events on this watcher into EV. EV will react to this call
309 as if the watcher had received the given $revents mask.
310
311 $revents = $w->clear_pending
312 If the watcher is pending, this function clears its pending status
313 and returns its $revents bitset (as if its callback was invoked). If
314 the watcher isn't pending it does nothing and returns 0.
315
316 $previous_state = $w->keepalive ($bool)
317 Normally, "EV::loop" will return when there are no active watchers
318 (which is a "deadlock" because no progress can be made anymore).
319 This is convinient because it allows you to start your watchers (and
320 your jobs), call "EV::loop" once and when it returns you know that
321 all your jobs are finished (or they forgot to register some watchers
322 for their task :).
323
324 Sometimes, however, this gets in your way, for example when the
325 module that calls "EV::loop" (usually the main program) is not the
326 same module as a long-living watcher (for example a DNS client
327 module written by somebody else even). Then you might want any
328 outstanding requests to be handled, but you would not want to keep
329 "EV::loop" from returning just because you happen to have this
330 long-running UDP port watcher.
331
332 In this case you can clear the keepalive status, which means that
333 even though your watcher is active, it won't keep "EV::loop" from
334 returning.
335
336 The initial value for keepalive is true (enabled), and you cna
337 change it any time.
338
339 Example: Register an I/O watcher for some UDP socket but do not keep
340 the event loop from running just because of that watcher.
341
342 my $udp_socket = ...
343 my $udp_watcher = EV::io $udp_socket, EV::READ, sub { ... };
344 $udp_watcher->keepalive (0);
345
346 $loop = $w->loop
347 Return the loop that this watcher is attached to.
348
349WATCHER TYPES
350 Each of the following subsections describes a single watcher type.
351
352 I/O WATCHERS - is this file descriptor readable or writable?
170 $w = EV::io $fileno_or_fh, $eventmask, $callback 353 $w = EV::io $fileno_or_fh, $eventmask, $callback
171 $w = EV::io_ns $fileno_or_fh, $eventmask, $callback 354 $w = EV::io_ns $fileno_or_fh, $eventmask, $callback
355 $w = $loop->io ($fileno_or_fh, $eventmask, $callback)
356 $w = $loop->io_ns ($fileno_or_fh, $eventmask, $callback)
172 As long as the returned watcher object is alive, call the $callback 357 As long as the returned watcher object is alive, call the $callback
173 when the events specified in $eventmask. 358 when at least one of events specified in $eventmask occurs.
174 359
175 The $eventmask can be one or more of these constants ORed together: 360 The $eventmask can be one or more of these constants ORed together:
176 361
177 EV::READ wait until read() wouldn't block anymore 362 EV::READ wait until read() wouldn't block anymore
178 EV::WRITE wait until write() wouldn't block anymore 363 EV::WRITE wait until write() wouldn't block anymore
… …
190 375
191 $current_eventmask = $w->events 376 $current_eventmask = $w->events
192 $old_eventmask = $w->events ($new_eventmask) 377 $old_eventmask = $w->events ($new_eventmask)
193 Returns the previously set event mask and optionally set a new one. 378 Returns the previously set event mask and optionally set a new one.
194 379
380 TIMER WATCHERS - relative and optionally repeating timeouts
195 $w = EV::timer $after, $repeat, $callback 381 $w = EV::timer $after, $repeat, $callback
196 $w = EV::timer_ns $after, $repeat, $callback 382 $w = EV::timer_ns $after, $repeat, $callback
197 Calls the callback after $after seconds. If $repeat is non-zero, the 383 $w = $loop->timer ($after, $repeat, $callback)
198 timer will be restarted (with the $repeat value as $after) after the 384 $w = $loop->timer_ns ($after, $repeat, $callback)
199 callback returns. 385 Calls the callback after $after seconds (which may be fractional).
386 If $repeat is non-zero, the timer will be restarted (with the
387 $repeat value as $after) after the callback returns.
200 388
201 This means that the callback would be called roughly after $after 389 This means that the callback would be called roughly after $after
202 seconds, and then every $repeat seconds. "Roughly" because the time 390 seconds, and then every $repeat seconds. The timer does his best not
203 of callback processing is not taken into account, so the timer will 391 to drift, but it will not invoke the timer more often then once per
204 slowly drift. If that isn't acceptable, look at EV::periodic. 392 event loop iteration, and might drift in other cases. If that isn't
393 acceptable, look at EV::periodic, which can provide long-term stable
394 timers.
205 395
206 The timer is based on a monotonic clock, that is if somebody is 396 The timer is based on a monotonic clock, that is, if somebody is
207 sitting in front of the machine while the timer is running and 397 sitting in front of the machine while the timer is running and
208 changes the system clock, the timer will nevertheless run (roughly) 398 changes the system clock, the timer will nevertheless run (roughly)
209 the same time. 399 the same time.
210 400
211 The "timer_ns" variant doesn't start (activate) the newly created 401 The "timer_ns" variant doesn't start (activate) the newly created
212 watcher. 402 watcher.
213 403
214 $w->set ($after, $repeat) 404 $w->set ($after, $repeat)
215 Reconfigures the watcher, see the constructor above for details. Can 405 Reconfigures the watcher, see the constructor above for details. Can
216 be at any time. 406 be called at any time.
217 407
218 $w->again 408 $w->again
219 Similar to the "start" method, but has special semantics for 409 Similar to the "start" method, but has special semantics for
220 repeating timers: 410 repeating timers:
221 411
412 If the timer is active and non-repeating, it will be stopped.
413
222 If the timer is active and repeating, reset the timeout to occur 414 If the timer is active and repeating, reset the timeout to occur
223 $repeat seconds after now. 415 $repeat seconds after now.
224 416
225 If the timer is active and non-repeating, it will be stopped.
226
227 If the timer is in active and repeating, start it. 417 If the timer is inactive and repeating, start it using the repeat
418 value.
228 419
229 Otherwise do nothing. 420 Otherwise do nothing.
230 421
231 This behaviour is useful when you have a timeout for some IO 422 This behaviour is useful when you have a timeout for some IO
232 operation. You create a timer object with the same value for $after 423 operation. You create a timer object with the same value for $after
233 and $repeat, and then, in the read/write watcher, run the "again" 424 and $repeat, and then, in the read/write watcher, run the "again"
234 method on the timeout. 425 method on the timeout.
235 426
427 PERIODIC WATCHERS - to cron or not to cron?
236 $w = EV::periodic $at, $interval, $callback 428 $w = EV::periodic $at, $interval, $reschedule_cb, $callback
237 $w = EV::periodic_ns $at, $interval, $callback 429 $w = EV::periodic_ns $at, $interval, $reschedule_cb, $callback
238 Similar to EV::timer, but the time is given as an absolute point in 430 $w = $loop->periodic ($at, $interval, $reschedule_cb, $callback)
239 time ($at), plus an optional $interval. 431 $w = $loop->periodic_ns ($at, $interval, $reschedule_cb, $callback)
432 Similar to EV::timer, but is not based on relative timeouts but on
433 absolute times. Apart from creating "simple" timers that trigger
434 "at" the specified time, it can also be used for non-drifting
435 absolute timers and more complex, cron-like, setups that are not
436 adversely affected by time jumps (i.e. when the system clock is
437 changed by explicit date -s or other means such as ntpd). It is also
438 the most complex watcher type in EV.
240 439
241 If the $interval is zero, then the callback will be called at the 440 It has three distinct "modes":
242 time $at if that is in the future, or as soon as possible if it is
243 in the past. It will not automatically repeat.
244 441
245 If the $interval is nonzero, then the watcher will always be 442 * absolute timer ($interval = $reschedule_cb = 0)
246 scheduled to time out at the next "$at + N * $interval" time.
247 443
248 This can be used to schedule a callback to run at very regular 444 This time simply fires at the wallclock time $at and doesn't
249 intervals, as long as the processing time is less then the interval 445 repeat. It will not adjust when a time jump occurs, that is, if
250 (otherwise obviously events will be skipped). 446 it is to be run at January 1st 2011 then it will run when the
447 system time reaches or surpasses this time.
251 448
449 * repeating interval timer ($interval > 0, $reschedule_cb = 0)
450
451 In this mode the watcher will always be scheduled to time out at
452 the next "$at + N * $interval" time (for some integer N) and
453 then repeat, regardless of any time jumps.
454
455 This can be used to create timers that do not drift with respect
456 to system time:
457
458 my $hourly = EV::periodic 0, 3600, 0, sub { print "once/hour\n" };
459
460 That doesn't mean there will always be 3600 seconds in between
461 triggers, but only that the the clalback will be called when the
462 system time shows a full hour (UTC).
463
252 Another way to think about it (for the mathematically inclined) is 464 Another way to think about it (for the mathematically inclined)
253 that EV::periodic will try to run the callback at the next possible 465 is that EV::periodic will try to run the callback in this mode
254 time where "$time = $at (mod $interval)", regardless of any time 466 at the next possible time where "$time = $at (mod $interval)",
255 jumps. 467 regardless of any time jumps.
256 468
257 This periodic timer is based on "wallclock time", that is, if the 469 * manual reschedule mode ($reschedule_cb = coderef)
258 clock changes ("ntp", "date -s" etc.), then the timer will 470
259 nevertheless run at the specified time. This means it will never 471 In this mode $interval and $at are both being ignored. Instead,
260 drift (it might jitter, but it will not drift). 472 each time the periodic watcher gets scheduled, the reschedule
473 callback ($reschedule_cb) will be called with the watcher as
474 first, and the current time as second argument.
475
476 *This callback MUST NOT stop or destroy this or any other
477 periodic watcher, ever, and MUST NOT call any event loop
478 functions or methods*. If you need to stop it, return 1e30 and
479 stop it afterwards. You may create and start a "EV::prepare"
480 watcher for this task.
481
482 It must return the next time to trigger, based on the passed
483 time value (that is, the lowest time value larger than or equal
484 to to the second argument). It will usually be called just
485 before the callback will be triggered, but might be called at
486 other times, too.
487
488 This can be used to create very complex timers, such as a timer
489 that triggers on each midnight, local time (actually 24 hours
490 after the last midnight, to keep the example simple. If you know
491 a way to do it correctly in about the same space (without
492 requiring elaborate modules), drop me a note :):
493
494 my $daily = EV::periodic 0, 0, sub {
495 my ($w, $now) = @_;
496
497 use Time::Local ();
498 my (undef, undef, undef, $d, $m, $y) = localtime $now;
499 86400 + Time::Local::timelocal 0, 0, 0, $d, $m, $y
500 }, sub {
501 print "it's midnight or likely shortly after, now\n";
502 };
261 503
262 The "periodic_ns" variant doesn't start (activate) the newly created 504 The "periodic_ns" variant doesn't start (activate) the newly created
263 watcher. 505 watcher.
264 506
265 $w->set ($at, $interval) 507 $w->set ($at, $interval, $reschedule_cb)
266 Reconfigures the watcher, see the constructor above for details. Can 508 Reconfigures the watcher, see the constructor above for details. Can
267 be at any time. 509 be called at any time.
268 510
511 $w->again
512 Simply stops and starts the watcher again.
513
514 $time = $w->at
515 Return the time that the watcher is expected to trigger next.
516
517 SIGNAL WATCHERS - signal me when a signal gets signalled!
269 $w = EV::signal $signal, $callback 518 $w = EV::signal $signal, $callback
270 $w = EV::signal_ns $signal, $callback 519 $w = EV::signal_ns $signal, $callback
271 Call the callback when $signal is received (the signal can be 520 Call the callback when $signal is received (the signal can be
272 specified by number or by name, just as with kill or %SIG). 521 specified by number or by name, just as with "kill" or %SIG).
273 522
274 EV will grab the signal for the process (the kernel only allows one 523 EV will grab the signal for the process (the kernel only allows one
275 component to receive a signal at a time) when you start a signal 524 component to receive a signal at a time) when you start a signal
276 watcher, and removes it again when you stop it. Perl does the same 525 watcher, and removes it again when you stop it. Perl does the same
277 when you add/remove callbacks to %SIG, so watch out. 526 when you add/remove callbacks to %SIG, so watch out.
… …
281 The "signal_ns" variant doesn't start (activate) the newly created 530 The "signal_ns" variant doesn't start (activate) the newly created
282 watcher. 531 watcher.
283 532
284 $w->set ($signal) 533 $w->set ($signal)
285 Reconfigures the watcher, see the constructor above for details. Can 534 Reconfigures the watcher, see the constructor above for details. Can
286 be at any time. 535 be called at any time.
287 536
288 $current_signum = $w->signal 537 $current_signum = $w->signal
289 $old_signum = $w->signal ($new_signal) 538 $old_signum = $w->signal ($new_signal)
290 Returns the previously set signal (always as a number not name) and 539 Returns the previously set signal (always as a number not name) and
291 optionally set a new one. 540 optionally set a new one.
292 541
542 CHILD WATCHERS - watch out for process status changes
293 $w = EV::child $pid, $callback 543 $w = EV::child $pid, $trace, $callback
294 $w = EV::child_ns $pid, $callback 544 $w = EV::child_ns $pid, $trace, $callback
545 $w = $loop->child ($pid, $trace, $callback)
546 $w = $loop->child_ns ($pid, $trace, $callback)
295 Call the callback when a status change for pid $pid (or any pid if 547 Call the callback when a status change for pid $pid (or any pid if
296 $pid is 0) has been received. More precisely: when the process 548 $pid is 0) has been received (a status change happens when the
549 process terminates or is killed, or, when trace is true,
550 additionally when it is stopped or continued). More precisely: when
297 receives a SIGCHLD, EV will fetch the outstanding exit/wait status 551 the process receives a "SIGCHLD", EV will fetch the outstanding
298 for all changed/zombie children and call the callback. 552 exit/wait status for all changed/zombie children and call the
553 callback.
299 554
300 You can access both status and pid by using the "rstatus" and "rpid" 555 It is valid (and fully supported) to install a child watcher after a
556 child has exited but before the event loop has started its next
557 iteration (for example, first you "fork", then the new child process
558 might exit, and only then do you install a child watcher in the
559 parent for the new pid).
560
561 You can access both exit (or tracing) status and pid by using the
301 methods on the watcher object. 562 "rstatus" and "rpid" methods on the watcher object.
302 563
303 You can have as many pid watchers per pid as you want. 564 You can have as many pid watchers per pid as you want, they will all
565 be called.
304 566
305 The "child_ns" variant doesn't start (activate) the newly created 567 The "child_ns" variant doesn't start (activate) the newly created
306 watcher. 568 watcher.
307 569
308 $w->set ($pid) 570 $w->set ($pid, $trace)
309 Reconfigures the watcher, see the constructor above for details. Can 571 Reconfigures the watcher, see the constructor above for details. Can
310 be at any time. 572 be called at any time.
311 573
312 $current_pid = $w->pid 574 $current_pid = $w->pid
313 $old_pid = $w->pid ($new_pid)
314 Returns the previously set process id and optionally set a new one. 575 Returns the previously set process id and optionally set a new one.
315 576
316 $exit_status = $w->rstatus 577 $exit_status = $w->rstatus
317 Return the exit/wait status (as returned by waitpid, see the waitpid 578 Return the exit/wait status (as returned by waitpid, see the waitpid
318 entry in perlfunc). 579 entry in perlfunc).
319 580
320 $pid = $w->rpid 581 $pid = $w->rpid
321 Return the pid of the awaited child (useful when you have installed 582 Return the pid of the awaited child (useful when you have installed
322 a watcher for all pids). 583 a watcher for all pids).
323 584
585 STAT WATCHERS - did the file attributes just change?
586 $w = EV::stat $path, $interval, $callback
587 $w = EV::stat_ns $path, $interval, $callback
588 $w = $loop->stat ($path, $interval, $callback)
589 $w = $loop->stat_ns ($path, $interval, $callback)
590 Call the callback when a file status change has been detected on
591 $path. The $path does not need to exist, changing from "path exists"
592 to "path does not exist" is a status change like any other.
593
594 The $interval is a recommended polling interval for systems where
595 OS-supported change notifications don't exist or are not supported.
596 If you use 0 then an unspecified default is used (which is highly
597 recommended!), which is to be expected to be around five seconds
598 usually.
599
600 This watcher type is not meant for massive numbers of stat watchers,
601 as even with OS-supported change notifications, this can be
602 resource-intensive.
603
604 The "stat_ns" variant doesn't start (activate) the newly created
605 watcher.
606
607 ... = $w->stat
608 This call is very similar to the perl "stat" built-in: It stats
609 (using "lstat") the path specified in the watcher and sets perls
610 stat cache (as well as EV's idea of the current stat values) to the
611 values found.
612
613 In scalar context, a boolean is return indicating success or failure
614 of the stat. In list context, the same 13-value list as with stat is
615 returned (except that the blksize and blocks fields are not
616 reliable).
617
618 In the case of an error, errno is set to "ENOENT" (regardless of the
619 actual error value) and the "nlink" value is forced to zero (if the
620 stat was successful then nlink is guaranteed to be non-zero).
621
622 See also the next two entries for more info.
623
624 ... = $w->attr
625 Just like "$w->stat", but without the initial stat'ing: this returns
626 the values most recently detected by EV. See the next entry for more
627 info.
628
629 ... = $w->prev
630 Just like "$w->stat", but without the initial stat'ing: this returns
631 the previous set of values, before the change.
632
633 That is, when the watcher callback is invoked, "$w->prev" will be
634 set to the values found *before* a change was detected, while
635 "$w->attr" returns the values found leading to the change detection.
636 The difference (if any) between "prev" and "attr" is what triggered
637 the callback.
638
639 If you did something to the filesystem object and do not want to
640 trigger yet another change, you can call "stat" to update EV's idea
641 of what the current attributes are.
642
643 $w->set ($path, $interval)
644 Reconfigures the watcher, see the constructor above for details. Can
645 be called at any time.
646
647 $current_path = $w->path
648 $old_path = $w->path ($new_path)
649 Returns the previously set path and optionally set a new one.
650
651 $current_interval = $w->interval
652 $old_interval = $w->interval ($new_interval)
653 Returns the previously set interval and optionally set a new one.
654 Can be used to query the actual interval used.
655
656 IDLE WATCHERS - when you've got nothing better to do...
324 $w = EV::idle $callback 657 $w = EV::idle $callback
325 $w = EV::idle_ns $callback 658 $w = EV::idle_ns $callback
659 $w = $loop->idle ($callback)
660 $w = $loop->idle_ns ($callback)
326 Call the callback when there are no pending io, timer/periodic, 661 Call the callback when there are no other pending watchers of the
327 signal or child events, i.e. when the process is idle. 662 same or higher priority (excluding check, prepare and other idle
663 watchers of the same or lower priority, of course). They are called
664 idle watchers because when the watcher is the highest priority
665 pending event in the process, the process is considered to be idle
666 at that priority.
667
668 If you want a watcher that is only ever called when *no* other
669 events are outstanding you have to set the priority to "EV::MINPRI".
328 670
329 The process will not block as long as any idle watchers are active, 671 The process will not block as long as any idle watchers are active,
330 and they will be called repeatedly until stopped. 672 and they will be called repeatedly until stopped.
331 673
674 For example, if you have idle watchers at priority 0 and 1, and an
675 I/O watcher at priority 0, then the idle watcher at priority 1 and
676 the I/O watcher will always run when ready. Only when the idle
677 watcher at priority 1 is stopped and the I/O watcher at priority 0
678 is not pending with the 0-priority idle watcher be invoked.
679
332 The "idle_ns" variant doesn't start (activate) the newly created 680 The "idle_ns" variant doesn't start (activate) the newly created
333 watcher. 681 watcher.
334 682
683 PREPARE WATCHERS - customise your event loop!
335 $w = EV::prepare $callback 684 $w = EV::prepare $callback
336 $w = EV::prepare_ns $callback 685 $w = EV::prepare_ns $callback
686 $w = $loop->prepare ($callback)
687 $w = $loop->prepare_ns ($callback)
337 Call the callback just before the process would block. You can still 688 Call the callback just before the process would block. You can still
338 create/modify any watchers at this point. 689 create/modify any watchers at this point.
339 690
340 See the EV::check watcher, below, for explanations and an example. 691 See the EV::check watcher, below, for explanations and an example.
341 692
342 The "prepare_ns" variant doesn't start (activate) the newly created 693 The "prepare_ns" variant doesn't start (activate) the newly created
343 watcher. 694 watcher.
344 695
696 CHECK WATCHERS - customise your event loop even more!
345 $w = EV::check $callback 697 $w = EV::check $callback
346 $w = EV::check_ns $callback 698 $w = EV::check_ns $callback
699 $w = $loop->check ($callback)
700 $w = $loop->check_ns ($callback)
347 Call the callback just after the process wakes up again (after it 701 Call the callback just after the process wakes up again (after it
348 has gathered events), but before any other callbacks have been 702 has gathered events), but before any other callbacks have been
349 invoked. 703 invoked.
350 704
351 This is used to integrate other event-based software into the EV 705 This is used to integrate other event-based software into the EV
… …
360 # do nothing unless active 714 # do nothing unless active
361 $dispatcher->{_event_queue_h} 715 $dispatcher->{_event_queue_h}
362 or return; 716 or return;
363 717
364 # make the dispatcher handle any outstanding stuff 718 # make the dispatcher handle any outstanding stuff
719 ... not shown
365 720
366 # create an IO watcher for each and every socket 721 # create an I/O watcher for each and every socket
367 @snmp_watcher = ( 722 @snmp_watcher = (
368 (map { EV::io $_, EV::READ, sub { } } 723 (map { EV::io $_, EV::READ, sub { } }
369 keys %{ $dispatcher->{_descriptors} }), 724 keys %{ $dispatcher->{_descriptors} }),
725
726 EV::timer +($event->[Net::SNMP::Dispatcher::_ACTIVE]
727 ? $event->[Net::SNMP::Dispatcher::_TIME] - EV::now : 0),
728 0, sub { },
370 ); 729 );
371
372 # if there are any timeouts, also create a timer
373 push @snmp_watcher, EV::timer $event->[Net::SNMP::Dispatcher::_TIME] - EV::now, 0, sub { }
374 if $event->[Net::SNMP::Dispatcher::_ACTIVE];
375 }; 730 };
376 731
377 The callbacks are irrelevant, the only purpose of those watchers is 732 The callbacks are irrelevant (and are not even being called), the
378 to wake up the process as soon as one of those events occurs (socket 733 only purpose of those watchers is to wake up the process as soon as
379 readable, or timer timed out). The corresponding EV::check watcher 734 one of those events occurs (socket readable, or timer timed out).
380 will then clean up: 735 The corresponding EV::check watcher will then clean up:
381 736
382 our $snmp_check = EV::check sub { 737 our $snmp_check = EV::check sub {
383 # destroy all watchers 738 # destroy all watchers
384 @snmp_watcher = (); 739 @snmp_watcher = ();
385 740
386 # make the dispatcher handle any new stuff 741 # make the dispatcher handle any new stuff
742 ... not shown
387 }; 743 };
388 744
389 The callbacks of the created watchers will not be called as the 745 The callbacks of the created watchers will not be called as the
390 watchers are destroyed before this cna happen (remember EV::check 746 watchers are destroyed before this cna happen (remember EV::check
391 gets called first). 747 gets called first).
392 748
393 The "check_ns" variant doesn't start (activate) the newly created 749 The "check_ns" variant doesn't start (activate) the newly created
394 watcher. 750 watcher.
395 751
752 FORK WATCHERS - the audacity to resume the event loop after a fork
753 Fork watchers are called when a "fork ()" was detected. The invocation
754 is done before the event loop blocks next and before "check" watchers
755 are being called, and only in the child after the fork.
756
757 $w = EV::fork $callback
758 $w = EV::fork_ns $callback
759 $w = $loop->fork ($callback)
760 $w = $loop->fork_ns ($callback)
761 Call the callback before the event loop is resumed in the child
762 process after a fork.
763
764 The "fork_ns" variant doesn't start (activate) the newly created
765 watcher.
766
767 EMBED WATCHERS - when one backend isn't enough...
768 This is a rather advanced watcher type that lets you embed one event
769 loop into another (currently only IO events are supported in the
770 embedded loop, other types of watchers might be handled in a delayed or
771 incorrect fashion and must not be used).
772
773 See the libev documentation at
774 <http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod#code_ev_embed_code
775 _when_one_backend_> for more details.
776
777 In short, this watcher is most useful on BSD systems without working
778 kqueue to still be able to handle a large number of sockets:
779
780 my $socket_loop;
781
782 # check wether we use SELECT or POLL _and_ KQUEUE is supported
783 if (
784 (EV::backend & (EV::BACKEND_POLL | EV::BACKEND_SELECT))
785 && (EV::supported_backends & EV::embeddable_backends & EV::BACKEND_KQUEUE)
786 ) {
787 # use kqueue for sockets
788 $socket_loop = new EV::Loop EV::BACKEND_KQUEUE | EV::FLAG_NOENV;
789 }
790
791 # use the default loop otherwise
792 $socket_loop ||= EV::default_loop;
793
794 $w = EV::embed $otherloop, $callback
795 $w = EV::embed_ns $otherloop, $callback
796 $w = $loop->embed ($otherloop, $callback)
797 $w = $loop->embed_ns ($otherloop, $callback)
798 Call the callback when the embedded event loop ($otherloop) has any
799 I/O activity. The $callback should alwas be specified as "undef" in
800 this version of EV, which means the embedded event loop will be
801 managed automatically.
802
803 The "embed_ns" variant doesn't start (activate) the newly created
804 watcher.
805
806 ASYNC WATCHERS - how to wake up another event loop
807 Async watchers are provided by EV, but have little use in perl directly,
808 as perl neither supports threads nor direct access to signal handlers or
809 other contexts where they could be of value.
810
811 It is, however, possible to use them from the XS level.
812
813 Please see the libev documentation for further details.
814
815 $w = EV::async $callback
816 $w = EV::async_ns $callback
817 $w->send
818 $bool = $w->async_pending
819
820PERL SIGNALS
821 While Perl signal handling (%SIG) is not affected by EV, the behaviour
822 with EV is as the same as any other C library: Perl-signals will only be
823 handled when Perl runs, which means your signal handler might be invoked
824 only the next time an event callback is invoked.
825
826 The solution is to use EV signal watchers (see "EV::signal"), which will
827 ensure proper operations with regards to other event watchers.
828
829 If you cannot do this for whatever reason, you can also force a watcher
830 to be called on every event loop iteration by installing a "EV::check"
831 watcher:
832
833 my $async_check = EV::check sub { };
834
835 This ensures that perl gets into control for a short time to handle any
836 pending signals, and also ensures (slightly) slower overall operation.
837
396THREADS 838THREADS
397 Threads are not supported by this in any way. Perl pseudo-threads is 839 Threads are not supported by this module in any way. Perl pseudo-threads
398 evil stuff and must die. 840 is evil stuff and must die. As soon as Perl gains real threads I will
841 work on thread support for it.
842
843FORK
844 Most of the "improved" event delivering mechanisms of modern operating
845 systems have quite a few problems with fork(2) (to put it bluntly: it is
846 not supported and usually destructive). Libev makes it possible to work
847 around this by having a function that recreates the kernel state after
848 fork in the child.
849
850 On non-win32 platforms, this module requires the pthread_atfork
851 functionality to do this automatically for you. This function is quite
852 buggy on most BSDs, though, so YMMV. The overhead for this is quite
853 negligible, because everything the function currently does is set a flag
854 that is checked only when the event loop gets used the next time, so
855 when you do fork but not use EV, the overhead is minimal.
856
857 On win32, there is no notion of fork so all this doesn't apply, of
858 course.
399 859
400SEE ALSO 860SEE ALSO
401 L<EV::DNS>, L<EV::AnyEvent>. 861 EV::ADNS (asynchronous DNS), Glib::EV (makes Glib/Gtk2 use EV as event
862 loop), EV::Glib (embed Glib into EV), Coro::EV (efficient coroutines
863 with EV), Net::SNMP::EV (asynchronous SNMP), AnyEvent for event-loop
864 agnostic and portable event driven programming.
402 865
403AUTHOR 866AUTHOR
404 Marc Lehmann <schmorp@schmorp.de> 867 Marc Lehmann <schmorp@schmorp.de>
405 http://home.schmorp.de/ 868 http://home.schmorp.de/
406 869

Diff Legend

– Removed lines
+ Added lines
< Changed lines
> Changed lines