1 |
=head1 NAME |
2 |
|
3 |
EV - perl interface to libev, a high performance full-featured event loop |
4 |
|
5 |
=head1 SYNOPSIS |
6 |
|
7 |
use EV; |
8 |
|
9 |
# TIMERS |
10 |
|
11 |
my $w = EV::timer 2, 0, sub { |
12 |
warn "is called after 2s"; |
13 |
}; |
14 |
|
15 |
my $w = EV::timer 2, 2, sub { |
16 |
warn "is called roughly every 2s (repeat = 2)"; |
17 |
}; |
18 |
|
19 |
undef $w; # destroy event watcher again |
20 |
|
21 |
my $w = EV::periodic 0, 60, 0, sub { |
22 |
warn "is called every minute, on the minute, exactly"; |
23 |
}; |
24 |
|
25 |
# IO |
26 |
|
27 |
my $w = EV::io *STDIN, EV::READ, sub { |
28 |
my ($w, $revents) = @_; # all callbacks receive the watcher and event mask |
29 |
warn "stdin is readable, you entered: ", <STDIN>; |
30 |
}; |
31 |
|
32 |
# SIGNALS |
33 |
|
34 |
my $w = EV::signal 'QUIT', sub { |
35 |
warn "sigquit received\n"; |
36 |
}; |
37 |
|
38 |
# CHILD/PID STATUS CHANGES |
39 |
|
40 |
my $w = EV::child 666, sub { |
41 |
my ($w, $revents) = @_; |
42 |
my $status = $w->rstatus; |
43 |
}; |
44 |
|
45 |
# STAT CHANGES |
46 |
my $w = EV::stat "/etc/passwd", 10, sub { |
47 |
my ($w, $revents) = @_; |
48 |
warn $w->path, " has changed somehow.\n"; |
49 |
}; |
50 |
|
51 |
# MAINLOOP |
52 |
EV::loop; # loop until EV::unloop is called or all watchers stop |
53 |
EV::loop EV::LOOP_ONESHOT; # block until at least one event could be handled |
54 |
EV::loop EV::LOOP_NONBLOCK; # try to handle same events, but do not block |
55 |
|
56 |
=head1 DESCRIPTION |
57 |
|
58 |
This module provides an interface to libev |
59 |
(L<http://software.schmorp.de/pkg/libev.html>). While the documentation |
60 |
below is comprehensive, one might also consult the documentation of libev |
61 |
itself (L<http://cvs.schmorp.de/libev/ev.html>) for more subtle details on |
62 |
watcher semantics or some discussion on the available backends, or how to |
63 |
force a specific backend with C<LIBEV_FLAGS>. |
64 |
|
65 |
=cut |
66 |
|
67 |
package EV; |
68 |
|
69 |
use strict; |
70 |
|
71 |
BEGIN { |
72 |
our $VERSION = '1.4'; |
73 |
use XSLoader; |
74 |
XSLoader::load "EV", $VERSION; |
75 |
} |
76 |
|
77 |
@EV::IO::ISA = |
78 |
@EV::Timer::ISA = |
79 |
@EV::Periodic::ISA = |
80 |
@EV::Signal::ISA = |
81 |
@EV::Idle::ISA = |
82 |
@EV::Prepare::ISA = |
83 |
@EV::Check::ISA = |
84 |
@EV::Child::ISA = |
85 |
@EV::Embed::ISA = |
86 |
@EV::Stat::ISA = "EV::Watcher"; |
87 |
|
88 |
=head1 BASIC INTERFACE |
89 |
|
90 |
=over 4 |
91 |
|
92 |
=item $EV::DIED |
93 |
|
94 |
Must contain a reference to a function that is called when a callback |
95 |
throws an exception (with $@ containing thr error). The default prints an |
96 |
informative message and continues. |
97 |
|
98 |
If this callback throws an exception it will be silently ignored. |
99 |
|
100 |
=item $time = EV::time |
101 |
|
102 |
Returns the current time in (fractional) seconds since the epoch. |
103 |
|
104 |
=item $time = EV::now |
105 |
|
106 |
Returns the time the last event loop iteration has been started. This |
107 |
is the time that (relative) timers are based on, and refering to it is |
108 |
usually faster then calling EV::time. |
109 |
|
110 |
=item $method = EV::method |
111 |
|
112 |
Returns an integer describing the backend used by libev (EV::METHOD_SELECT |
113 |
or EV::METHOD_EPOLL). |
114 |
|
115 |
=item EV::loop [$flags] |
116 |
|
117 |
Begin checking for events and calling callbacks. It returns when a |
118 |
callback calls EV::unloop. |
119 |
|
120 |
The $flags argument can be one of the following: |
121 |
|
122 |
0 as above |
123 |
EV::LOOP_ONESHOT block at most once (wait, but do not loop) |
124 |
EV::LOOP_NONBLOCK do not block at all (fetch/handle events but do not wait) |
125 |
|
126 |
=item EV::unloop [$how] |
127 |
|
128 |
When called with no arguments or an argument of EV::UNLOOP_ONE, makes the |
129 |
innermost call to EV::loop return. |
130 |
|
131 |
When called with an argument of EV::UNLOOP_ALL, all calls to EV::loop will return as |
132 |
fast as possible. |
133 |
|
134 |
=item EV::once $fh_or_undef, $events, $timeout, $cb->($revents) |
135 |
|
136 |
This function rolls together an I/O and a timer watcher for a single |
137 |
one-shot event without the need for managing a watcher object. |
138 |
|
139 |
If C<$fh_or_undef> is a filehandle or file descriptor, then C<$events> |
140 |
must be a bitset containing either C<EV::READ>, C<EV::WRITE> or C<EV::READ |
141 |
| EV::WRITE>, indicating the type of I/O event you want to wait for. If |
142 |
you do not want to wait for some I/O event, specify C<undef> for |
143 |
C<$fh_or_undef> and C<0> for C<$events>). |
144 |
|
145 |
If timeout is C<undef> or negative, then there will be no |
146 |
timeout. Otherwise a EV::timer with this value will be started. |
147 |
|
148 |
When an error occurs or either the timeout or I/O watcher triggers, then |
149 |
the callback will be called with the received event set (in general |
150 |
you can expect it to be a combination of C<EV:ERROR>, C<EV::READ>, |
151 |
C<EV::WRITE> and C<EV::TIMEOUT>). |
152 |
|
153 |
EV::once doesn't return anything: the watchers stay active till either |
154 |
of them triggers, then they will be stopped and freed, and the callback |
155 |
invoked. |
156 |
|
157 |
=back |
158 |
|
159 |
=head2 WATCHER OBJECTS |
160 |
|
161 |
A watcher is an object that gets created to record your interest in some |
162 |
event. For instance, if you want to wait for STDIN to become readable, you |
163 |
would create an EV::io watcher for that: |
164 |
|
165 |
my $watcher = EV::io *STDIN, EV::READ, sub { |
166 |
my ($watcher, $revents) = @_; |
167 |
warn "yeah, STDIN should not be readable without blocking!\n" |
168 |
}; |
169 |
|
170 |
All watchers can be active (waiting for events) or inactive (paused). Only |
171 |
active watchers will have their callbacks invoked. All callbacks will be |
172 |
called with at least two arguments: the watcher and a bitmask of received |
173 |
events. |
174 |
|
175 |
Each watcher type has its associated bit in revents, so you can use the |
176 |
same callback for multiple watchers. The event mask is named after the |
177 |
type, i..e. EV::child sets EV::CHILD, EV::prepare sets EV::PREPARE, |
178 |
EV::periodic sets EV::PERIODIC and so on, with the exception of IO events |
179 |
(which can set both EV::READ and EV::WRITE bits), and EV::timer (which |
180 |
uses EV::TIMEOUT). |
181 |
|
182 |
In the rare case where one wants to create a watcher but not start it at |
183 |
the same time, each constructor has a variant with a trailing C<_ns> in |
184 |
its name, e.g. EV::io has a non-starting variant EV::io_ns and so on. |
185 |
|
186 |
Please note that a watcher will automatically be stopped when the watcher |
187 |
object is destroyed, so you I<need> to keep the watcher objects returned by |
188 |
the constructors. |
189 |
|
190 |
Also, all methods changing some aspect of a watcher (->set, ->priority, |
191 |
->fh and so on) automatically stop and start it again if it is active, |
192 |
which means pending events get lost. |
193 |
|
194 |
=head2 COMMON WATCHER METHODS |
195 |
|
196 |
This section lists methods common to all watchers. |
197 |
|
198 |
=over 4 |
199 |
|
200 |
=item $w->start |
201 |
|
202 |
Starts a watcher if it isn't active already. Does nothing to an already |
203 |
active watcher. By default, all watchers start out in the active state |
204 |
(see the description of the C<_ns> variants if you need stopped watchers). |
205 |
|
206 |
=item $w->stop |
207 |
|
208 |
Stop a watcher if it is active. Also clear any pending events (events that |
209 |
have been received but that didn't yet result in a callback invocation), |
210 |
regardless of wether the watcher was active or not. |
211 |
|
212 |
=item $bool = $w->is_active |
213 |
|
214 |
Returns true if the watcher is active, false otherwise. |
215 |
|
216 |
=item $current_data = $w->data |
217 |
|
218 |
=item $old_data = $w->data ($new_data) |
219 |
|
220 |
Queries a freely usable data scalar on the watcher and optionally changes |
221 |
it. This is a way to associate custom data with a watcher: |
222 |
|
223 |
my $w = EV::timer 60, 0, sub { |
224 |
warn $_[0]->data; |
225 |
}; |
226 |
$w->data ("print me!"); |
227 |
|
228 |
=item $current_cb = $w->cb |
229 |
|
230 |
=item $old_cb = $w->cb ($new_cb) |
231 |
|
232 |
Queries the callback on the watcher and optionally changes it. You can do |
233 |
this at any time without the watcher restarting. |
234 |
|
235 |
=item $current_priority = $w->priority |
236 |
|
237 |
=item $old_priority = $w->priority ($new_priority) |
238 |
|
239 |
Queries the priority on the watcher and optionally changes it. Pending |
240 |
watchers with higher priority will be invoked first. The valid range of |
241 |
priorities lies between EV::MAXPRI (default 2) and EV::MINPRI (default |
242 |
-2). If the priority is outside this range it will automatically be |
243 |
normalised to the nearest valid priority. |
244 |
|
245 |
The default priority of any newly-created watcher is 0. |
246 |
|
247 |
Note that the priority semantics have not yet been fleshed out and are |
248 |
subject to almost certain change. |
249 |
|
250 |
=item $w->trigger ($revents) |
251 |
|
252 |
Call the callback *now* with the given event mask. |
253 |
|
254 |
=item $previous_state = $w->keepalive ($bool) |
255 |
|
256 |
Normally, C<EV::loop> will return when there are no active watchers |
257 |
(which is a "deadlock" because no progress can be made anymore). This is |
258 |
convinient because it allows you to start your watchers (and your jobs), |
259 |
call C<EV::loop> once and when it returns you know that all your jobs are |
260 |
finished (or they forgot to register some watchers for their task :). |
261 |
|
262 |
Sometimes, however, this gets in your way, for example when you the module |
263 |
that calls C<EV::loop> (usually the main program) is not the same module |
264 |
as a long-living watcher (for example a DNS client module written by |
265 |
somebody else even). Then you might want any outstanding requests to be |
266 |
handled, but you would not want to keep C<EV::loop> from returning just |
267 |
because you happen to have this long-running UDP port watcher. |
268 |
|
269 |
In this case you can clear the keepalive status, which means that even |
270 |
though your watcher is active, it won't keep C<EV::loop> from returning. |
271 |
|
272 |
The initial value for keepalive is true (enabled), and you cna change it |
273 |
any time. |
274 |
|
275 |
Example: Register an IO watcher for some UDP socket but do not keep the |
276 |
event loop from running just because of that watcher. |
277 |
|
278 |
my $udp_socket = ... |
279 |
my $udp_watcher = EV::io $udp_socket, EV::READ, sub { ... }; |
280 |
$udp_watcher->keepalive (0); |
281 |
|
282 |
=back |
283 |
|
284 |
|
285 |
=head2 WATCHER TYPES |
286 |
|
287 |
Each of the following subsections describes a single watcher type. |
288 |
|
289 |
=head3 IO WATCHERS - is this file descriptor readable or writable? |
290 |
|
291 |
=over 4 |
292 |
|
293 |
=item $w = EV::io $fileno_or_fh, $eventmask, $callback |
294 |
|
295 |
=item $w = EV::io_ns $fileno_or_fh, $eventmask, $callback |
296 |
|
297 |
As long as the returned watcher object is alive, call the C<$callback> |
298 |
when at least one of events specified in C<$eventmask> occurs. |
299 |
|
300 |
The $eventmask can be one or more of these constants ORed together: |
301 |
|
302 |
EV::READ wait until read() wouldn't block anymore |
303 |
EV::WRITE wait until write() wouldn't block anymore |
304 |
|
305 |
The C<io_ns> variant doesn't start (activate) the newly created watcher. |
306 |
|
307 |
=item $w->set ($fileno_or_fh, $eventmask) |
308 |
|
309 |
Reconfigures the watcher, see the constructor above for details. Can be |
310 |
called at any time. |
311 |
|
312 |
=item $current_fh = $w->fh |
313 |
|
314 |
=item $old_fh = $w->fh ($new_fh) |
315 |
|
316 |
Returns the previously set filehandle and optionally set a new one. |
317 |
|
318 |
=item $current_eventmask = $w->events |
319 |
|
320 |
=item $old_eventmask = $w->events ($new_eventmask) |
321 |
|
322 |
Returns the previously set event mask and optionally set a new one. |
323 |
|
324 |
=back |
325 |
|
326 |
|
327 |
=head3 TIMER WATCHERS - relative and optionally repeating timeouts |
328 |
|
329 |
=over 4 |
330 |
|
331 |
=item $w = EV::timer $after, $repeat, $callback |
332 |
|
333 |
=item $w = EV::timer_ns $after, $repeat, $callback |
334 |
|
335 |
Calls the callback after C<$after> seconds (which may be fractional). If |
336 |
C<$repeat> is non-zero, the timer will be restarted (with the $repeat |
337 |
value as $after) after the callback returns. |
338 |
|
339 |
This means that the callback would be called roughly after C<$after> |
340 |
seconds, and then every C<$repeat> seconds. The timer does his best not |
341 |
to drift, but it will not invoke the timer more often then once per event |
342 |
loop iteration, and might drift in other cases. If that isn't acceptable, |
343 |
look at EV::periodic, which can provide long-term stable timers. |
344 |
|
345 |
The timer is based on a monotonic clock, that is, if somebody is sitting |
346 |
in front of the machine while the timer is running and changes the system |
347 |
clock, the timer will nevertheless run (roughly) the same time. |
348 |
|
349 |
The C<timer_ns> variant doesn't start (activate) the newly created watcher. |
350 |
|
351 |
=item $w->set ($after, $repeat) |
352 |
|
353 |
Reconfigures the watcher, see the constructor above for details. Can be called at |
354 |
any time. |
355 |
|
356 |
=item $w->again |
357 |
|
358 |
Similar to the C<start> method, but has special semantics for repeating timers: |
359 |
|
360 |
If the timer is active and non-repeating, it will be stopped. |
361 |
|
362 |
If the timer is active and repeating, reset the timeout to occur |
363 |
C<$repeat> seconds after now. |
364 |
|
365 |
If the timer is inactive and repeating, start it using the repeat value. |
366 |
|
367 |
Otherwise do nothing. |
368 |
|
369 |
This behaviour is useful when you have a timeout for some IO |
370 |
operation. You create a timer object with the same value for C<$after> and |
371 |
C<$repeat>, and then, in the read/write watcher, run the C<again> method |
372 |
on the timeout. |
373 |
|
374 |
=back |
375 |
|
376 |
|
377 |
=head3 PERIODIC WATCHERS - to cron or not to cron? |
378 |
|
379 |
=over 4 |
380 |
|
381 |
=item $w = EV::periodic $at, $interval, $reschedule_cb, $callback |
382 |
|
383 |
=item $w = EV::periodic_ns $at, $interval, $reschedule_cb, $callback |
384 |
|
385 |
Similar to EV::timer, but is not based on relative timeouts but on |
386 |
absolute times. Apart from creating "simple" timers that trigger "at" the |
387 |
specified time, it can also be used for non-drifting absolute timers and |
388 |
more complex, cron-like, setups that are not adversely affected by time |
389 |
jumps (i.e. when the system clock is changed by explicit date -s or other |
390 |
means such as ntpd). It is also the most complex watcher type in EV. |
391 |
|
392 |
It has three distinct "modes": |
393 |
|
394 |
=over 4 |
395 |
|
396 |
=item * absolute timer ($interval = $reschedule_cb = 0) |
397 |
|
398 |
This time simply fires at the wallclock time C<$at> and doesn't repeat. It |
399 |
will not adjust when a time jump occurs, that is, if it is to be run |
400 |
at January 1st 2011 then it will run when the system time reaches or |
401 |
surpasses this time. |
402 |
|
403 |
=item * non-repeating interval timer ($interval > 0, $reschedule_cb = 0) |
404 |
|
405 |
In this mode the watcher will always be scheduled to time out at the |
406 |
next C<$at + N * $interval> time (for some integer N) and then repeat, |
407 |
regardless of any time jumps. |
408 |
|
409 |
This can be used to create timers that do not drift with respect to system |
410 |
time: |
411 |
|
412 |
my $hourly = EV::periodic 0, 3600, 0, sub { print "once/hour\n" }; |
413 |
|
414 |
That doesn't mean there will always be 3600 seconds in between triggers, |
415 |
but only that the the clalback will be called when the system time shows a |
416 |
full hour (UTC). |
417 |
|
418 |
Another way to think about it (for the mathematically inclined) is that |
419 |
EV::periodic will try to run the callback in this mode at the next |
420 |
possible time where C<$time = $at (mod $interval)>, regardless of any time |
421 |
jumps. |
422 |
|
423 |
=item * manual reschedule mode ($reschedule_cb = coderef) |
424 |
|
425 |
In this mode $interval and $at are both being ignored. Instead, each |
426 |
time the periodic watcher gets scheduled, the reschedule callback |
427 |
($reschedule_cb) will be called with the watcher as first, and the current |
428 |
time as second argument. |
429 |
|
430 |
I<This callback MUST NOT stop or destroy this or any other periodic |
431 |
watcher, ever>. If you need to stop it, return 1e30 and stop it |
432 |
afterwards. |
433 |
|
434 |
It must return the next time to trigger, based on the passed time value |
435 |
(that is, the lowest time value larger than to the second argument). It |
436 |
will usually be called just before the callback will be triggered, but |
437 |
might be called at other times, too. |
438 |
|
439 |
This can be used to create very complex timers, such as a timer that |
440 |
triggers on each midnight, local time (actually 24 hours after the last |
441 |
midnight, to keep the example simple. If you know a way to do it correctly |
442 |
in about the same space (without requiring elaborate modules), drop me a |
443 |
note :): |
444 |
|
445 |
my $daily = EV::periodic 0, 0, sub { |
446 |
my ($w, $now) = @_; |
447 |
|
448 |
use Time::Local (); |
449 |
my (undef, undef, undef, $d, $m, $y) = localtime $now; |
450 |
86400 + Time::Local::timelocal 0, 0, 0, $d, $m, $y |
451 |
}, sub { |
452 |
print "it's midnight or likely shortly after, now\n"; |
453 |
}; |
454 |
|
455 |
=back |
456 |
|
457 |
The C<periodic_ns> variant doesn't start (activate) the newly created watcher. |
458 |
|
459 |
=item $w->set ($at, $interval, $reschedule_cb) |
460 |
|
461 |
Reconfigures the watcher, see the constructor above for details. Can be called at |
462 |
any time. |
463 |
|
464 |
=item $w->again |
465 |
|
466 |
Simply stops and starts the watcher again. |
467 |
|
468 |
=back |
469 |
|
470 |
|
471 |
=head3 SIGNAL WATCHERS - signal me when a signal gets signalled! |
472 |
|
473 |
=over 4 |
474 |
|
475 |
=item $w = EV::signal $signal, $callback |
476 |
|
477 |
=item $w = EV::signal_ns $signal, $callback |
478 |
|
479 |
Call the callback when $signal is received (the signal can be specified by |
480 |
number or by name, just as with C<kill> or C<%SIG>). |
481 |
|
482 |
EV will grab the signal for the process (the kernel only allows one |
483 |
component to receive a signal at a time) when you start a signal watcher, |
484 |
and removes it again when you stop it. Perl does the same when you |
485 |
add/remove callbacks to C<%SIG>, so watch out. |
486 |
|
487 |
You can have as many signal watchers per signal as you want. |
488 |
|
489 |
The C<signal_ns> variant doesn't start (activate) the newly created watcher. |
490 |
|
491 |
=item $w->set ($signal) |
492 |
|
493 |
Reconfigures the watcher, see the constructor above for details. Can be |
494 |
called at any time. |
495 |
|
496 |
=item $current_signum = $w->signal |
497 |
|
498 |
=item $old_signum = $w->signal ($new_signal) |
499 |
|
500 |
Returns the previously set signal (always as a number not name) and |
501 |
optionally set a new one. |
502 |
|
503 |
=back |
504 |
|
505 |
|
506 |
=head3 CHILD WATCHERS - watch out for process status changes |
507 |
|
508 |
=over 4 |
509 |
|
510 |
=item $w = EV::child $pid, $callback |
511 |
|
512 |
=item $w = EV::child_ns $pid, $callback |
513 |
|
514 |
Call the callback when a status change for pid C<$pid> (or any pid if |
515 |
C<$pid> is 0) has been received. More precisely: when the process receives |
516 |
a C<SIGCHLD>, EV will fetch the outstanding exit/wait status for all |
517 |
changed/zombie children and call the callback. |
518 |
|
519 |
It is valid (and fully supported) to install a child watcher after a child |
520 |
has exited but before the event loop has started its next iteration (for |
521 |
example, first you C<fork>, then the new child process might exit, and |
522 |
only then do you install a child watcher in the parent for the new pid). |
523 |
|
524 |
You can access both exit (or tracing) status and pid by using the |
525 |
C<rstatus> and C<rpid> methods on the watcher object. |
526 |
|
527 |
You can have as many pid watchers per pid as you want, they will all be |
528 |
called. |
529 |
|
530 |
The C<child_ns> variant doesn't start (activate) the newly created watcher. |
531 |
|
532 |
=item $w->set ($pid) |
533 |
|
534 |
Reconfigures the watcher, see the constructor above for details. Can be called at |
535 |
any time. |
536 |
|
537 |
=item $current_pid = $w->pid |
538 |
|
539 |
=item $old_pid = $w->pid ($new_pid) |
540 |
|
541 |
Returns the previously set process id and optionally set a new one. |
542 |
|
543 |
=item $exit_status = $w->rstatus |
544 |
|
545 |
Return the exit/wait status (as returned by waitpid, see the waitpid entry |
546 |
in perlfunc). |
547 |
|
548 |
=item $pid = $w->rpid |
549 |
|
550 |
Return the pid of the awaited child (useful when you have installed a |
551 |
watcher for all pids). |
552 |
|
553 |
=back |
554 |
|
555 |
|
556 |
=head3 IDLE WATCHERS - when you've got nothing better to do... |
557 |
|
558 |
=over 4 |
559 |
|
560 |
=item $w = EV::idle $callback |
561 |
|
562 |
=item $w = EV::idle_ns $callback |
563 |
|
564 |
Call the callback when there are no pending io, timer/periodic, signal or |
565 |
child events, i.e. when the process is idle. |
566 |
|
567 |
The process will not block as long as any idle watchers are active, and |
568 |
they will be called repeatedly until stopped. |
569 |
|
570 |
The C<idle_ns> variant doesn't start (activate) the newly created watcher. |
571 |
|
572 |
=back |
573 |
|
574 |
|
575 |
=head3 PREPARE WATCHERS - customise your event loop! |
576 |
|
577 |
=over 4 |
578 |
|
579 |
=item $w = EV::prepare $callback |
580 |
|
581 |
=item $w = EV::prepare_ns $callback |
582 |
|
583 |
Call the callback just before the process would block. You can still |
584 |
create/modify any watchers at this point. |
585 |
|
586 |
See the EV::check watcher, below, for explanations and an example. |
587 |
|
588 |
The C<prepare_ns> variant doesn't start (activate) the newly created watcher. |
589 |
|
590 |
=back |
591 |
|
592 |
|
593 |
=head3 CHECK WATCHERS - customise your event loop even more! |
594 |
|
595 |
=over 4 |
596 |
|
597 |
=item $w = EV::check $callback |
598 |
|
599 |
=item $w = EV::check_ns $callback |
600 |
|
601 |
Call the callback just after the process wakes up again (after it has |
602 |
gathered events), but before any other callbacks have been invoked. |
603 |
|
604 |
This is used to integrate other event-based software into the EV |
605 |
mainloop: You register a prepare callback and in there, you create io and |
606 |
timer watchers as required by the other software. Here is a real-world |
607 |
example of integrating Net::SNMP (with some details left out): |
608 |
|
609 |
our @snmp_watcher; |
610 |
|
611 |
our $snmp_prepare = EV::prepare sub { |
612 |
# do nothing unless active |
613 |
$dispatcher->{_event_queue_h} |
614 |
or return; |
615 |
|
616 |
# make the dispatcher handle any outstanding stuff |
617 |
... not shown |
618 |
|
619 |
# create an IO watcher for each and every socket |
620 |
@snmp_watcher = ( |
621 |
(map { EV::io $_, EV::READ, sub { } } |
622 |
keys %{ $dispatcher->{_descriptors} }), |
623 |
|
624 |
EV::timer +($event->[Net::SNMP::Dispatcher::_ACTIVE] |
625 |
? $event->[Net::SNMP::Dispatcher::_TIME] - EV::now : 0), |
626 |
0, sub { }, |
627 |
); |
628 |
}; |
629 |
|
630 |
The callbacks are irrelevant (and are not even being called), the |
631 |
only purpose of those watchers is to wake up the process as soon as |
632 |
one of those events occurs (socket readable, or timer timed out). The |
633 |
corresponding EV::check watcher will then clean up: |
634 |
|
635 |
our $snmp_check = EV::check sub { |
636 |
# destroy all watchers |
637 |
@snmp_watcher = (); |
638 |
|
639 |
# make the dispatcher handle any new stuff |
640 |
... not shown |
641 |
}; |
642 |
|
643 |
The callbacks of the created watchers will not be called as the watchers |
644 |
are destroyed before this cna happen (remember EV::check gets called |
645 |
first). |
646 |
|
647 |
The C<check_ns> variant doesn't start (activate) the newly created watcher. |
648 |
|
649 |
=back |
650 |
|
651 |
=head3 STAT WATCHERS - did the file attributes just change? |
652 |
|
653 |
=over 4 |
654 |
|
655 |
=item $w = EV::stat $path, $interval, $callback |
656 |
|
657 |
=item $w = EV::stat_ns $path, $interval, $callback |
658 |
|
659 |
Call the callback when a file status change has been detected on |
660 |
C<$path>. The C<$path> does not need to exist, changing from "path exists" |
661 |
to "path does not exist" is a status change like any other. |
662 |
|
663 |
The C<$interval> is a recommended polling interval for systems where |
664 |
OS-supported change notifications don't exist or are not supported. If |
665 |
you use C<0> then an unspecified default is used (which is highly |
666 |
recommended!), which is to be expected to be around five seconds usually. |
667 |
|
668 |
This watcher type is not meant for massive numbers of stat watchers, |
669 |
as even with OS-supported change notifications, this can be |
670 |
resource-intensive. |
671 |
|
672 |
The C<stat_ns> variant doesn't start (activate) the newly created watcher. |
673 |
|
674 |
=item $w->set ($path, $interval) |
675 |
|
676 |
Reconfigures the watcher, see the constructor above for details. Can be |
677 |
called at any time. |
678 |
|
679 |
=item $current_path = $w->path |
680 |
|
681 |
=item $old_path = $w->path ($new_path) |
682 |
|
683 |
Returns the previously set path and optionally set a new one. |
684 |
|
685 |
=item $current_interval = $w->interval |
686 |
|
687 |
=item $old_interval = $w->interval ($new_interval) |
688 |
|
689 |
Returns the previously set interval and optionally set a new one. Can be |
690 |
used to query the actual interval used. |
691 |
|
692 |
=back |
693 |
|
694 |
|
695 |
=head1 THREADS |
696 |
|
697 |
Threads are not supported by this module in any way. Perl pseudo-threads |
698 |
is evil stuff and must die. As soon as Perl gains real threads I will work |
699 |
on thread support for it. |
700 |
|
701 |
=head1 FORK |
702 |
|
703 |
Most of the "improved" event delivering mechanisms of modern operating |
704 |
systems have quite a few problems with fork(2) (to put it bluntly: it is |
705 |
not supported and usually destructive). Libev makes it possible to work |
706 |
around this by having a function that recreates the kernel state after |
707 |
fork in the child. |
708 |
|
709 |
On non-win32 platforms, this module requires the pthread_atfork |
710 |
functionality to do this automatically for you. This function is quite |
711 |
buggy on most BSDs, though, so YMMV. The overhead for this is quite |
712 |
negligible, because everything the function currently does is set a flag |
713 |
that is checked only when the event loop gets used the next time, so when |
714 |
you do fork but not use EV, the overhead is minimal. |
715 |
|
716 |
On win32, there is no notion of fork so all this doesn't apply, of course. |
717 |
|
718 |
=cut |
719 |
|
720 |
our $DIED = sub { |
721 |
warn "EV: error in callback (ignoring): $@"; |
722 |
}; |
723 |
|
724 |
default_loop |
725 |
or die 'EV: cannot initialise libev backend. bad $ENV{LIBEV_METHODS}?'; |
726 |
|
727 |
1; |
728 |
|
729 |
=head1 SEE ALSO |
730 |
|
731 |
L<EV::DNS>. |
732 |
|
733 |
=head1 AUTHOR |
734 |
|
735 |
Marc Lehmann <schmorp@schmorp.de> |
736 |
http://home.schmorp.de/ |
737 |
|
738 |
=cut |
739 |
|