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 |
|
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# TIMERS |
10 |
|
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my $w = EV::timer 2, 0, sub { |
12 |
warn "is called after 2s"; |
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}; |
14 |
|
15 |
my $w = EV::timer 2, 2, sub { |
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warn "is called roughly every 2s (repeat = 2)"; |
17 |
}; |
18 |
|
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undef $w; # destroy event watcher again |
20 |
|
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my $w = EV::periodic 0, 60, 0, sub { |
22 |
warn "is called every minute, on the minute, exactly"; |
23 |
}; |
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|
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# 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 |
}; |
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|
32 |
# SIGNALS |
33 |
|
34 |
my $w = EV::signal 'QUIT', sub { |
35 |
warn "sigquit received\n"; |
36 |
}; |
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|
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# 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 |
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EV::loop EV::LOOP_ONESHOT; # block until at least one event could be handled |
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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>, or just about in any case |
64 |
because it has much more detailed information. |
65 |
|
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=cut |
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|
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package EV; |
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|
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use strict; |
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|
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BEGIN { |
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our $VERSION = '2.0'; |
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use XSLoader; |
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XSLoader::load "EV", $VERSION; |
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} |
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|
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@EV::IO::ISA = |
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@EV::Timer::ISA = |
80 |
@EV::Periodic::ISA = |
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@EV::Signal::ISA = |
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@EV::Child::ISA = |
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@EV::Stat::ISA = |
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@EV::Idle::ISA = |
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@EV::Prepare::ISA = |
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@EV::Check::ISA = |
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@EV::Embed::ISA = |
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@EV::Fork::ISA = |
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"EV::Watcher"; |
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|
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@EV::Loop::Default::ISA = "EV::Loop"; |
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|
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=head1 EVENT LOOPS |
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|
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EV supports multiple event loops: There is a single "default event loop" |
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that can handle everything including signals and child watchers, and any |
97 |
number of "dynamic event loops" that can use different backends (with |
98 |
various limitations), but no child and signal watchers. |
99 |
|
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You do not have to do anything to create the default event loop: When |
101 |
the module is loaded a suitable backend is selected on the premise of |
102 |
selecting a working backend (which for example rules out kqueue on most |
103 |
BSDs). Modules should, unless they have "special needs" always use the |
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default loop as this is fastest (perl-wise), best supported by other |
105 |
modules (e.g. AnyEvent or Coro) and most portable event loop. |
106 |
|
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For specific programs you cna create additional event loops dynamically. |
108 |
|
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=over 4 |
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|
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=item $loop = new EV::loop [$flags] |
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|
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Create a new event loop as per the specified flags. Please refer to the |
114 |
C<ev_loop_new ()> function description in the libev documentation |
115 |
(L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod#GLOBAL_FUNCTIONS>) |
116 |
for more info. |
117 |
|
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The loop will automatically be destroyed when it is no longer referenced |
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by any watcher and the loop object goes out of scope. |
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|
121 |
Using C<EV::FLAG_FORKCHECK> is recommended, as only the default event loop |
122 |
is protected by this module. |
123 |
|
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=item $loop->loop_fork |
125 |
|
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Must be called after a fork in the child, before entering or continuing |
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the event loop. An alternative is to use C<EV::FLAG_FORKCHECK> which calls |
128 |
this fucntion automatically, at some performance loss (refer to the libev |
129 |
documentation). |
130 |
|
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=back |
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|
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|
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=head1 BASIC INTERFACE |
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|
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=over 4 |
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|
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=item $EV::DIED |
139 |
|
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Must contain a reference to a function that is called when a callback |
141 |
throws an exception (with $@ containing the error). The default prints an |
142 |
informative message and continues. |
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|
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If this callback throws an exception it will be silently ignored. |
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|
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=item $time = EV::time |
147 |
|
148 |
Returns the current time in (fractional) seconds since the epoch. |
149 |
|
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=item $time = EV::now |
151 |
|
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=item $time = $loop->now |
153 |
|
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Returns the time the last event loop iteration has been started. This |
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is the time that (relative) timers are based on, and refering to it is |
156 |
usually faster then calling EV::time. |
157 |
|
158 |
=item $backend = EV::backend |
159 |
|
160 |
=item $backend = $loop->backend |
161 |
|
162 |
Returns an integer describing the backend used by libev (EV::METHOD_SELECT |
163 |
or EV::METHOD_EPOLL). |
164 |
|
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=item EV::loop [$flags] |
166 |
|
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=item $loop->loop ([$flags]) |
168 |
|
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Begin checking for events and calling callbacks. It returns when a |
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callback calls EV::unloop. |
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|
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The $flags argument can be one of the following: |
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|
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0 as above |
175 |
EV::LOOP_ONESHOT block at most once (wait, but do not loop) |
176 |
EV::LOOP_NONBLOCK do not block at all (fetch/handle events but do not wait) |
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|
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=item EV::unloop [$how] |
179 |
|
180 |
=item $loop->unloop ([$how]) |
181 |
|
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When called with no arguments or an argument of EV::UNLOOP_ONE, makes the |
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innermost call to EV::loop return. |
184 |
|
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When called with an argument of EV::UNLOOP_ALL, all calls to EV::loop will return as |
186 |
fast as possible. |
187 |
|
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=item $count = EV::loop_count |
189 |
|
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=item $count = $loop->loop_count |
191 |
|
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Return the number of times the event loop has polled for new |
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events. Sometiems useful as a generation counter. |
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|
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=item EV::once $fh_or_undef, $events, $timeout, $cb->($revents) |
196 |
|
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=item $loop->once ($fh_or_undef, $events, $timeout, $cb->($revents)) |
198 |
|
199 |
This function rolls together an I/O and a timer watcher for a single |
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one-shot event without the need for managing a watcher object. |
201 |
|
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If C<$fh_or_undef> is a filehandle or file descriptor, then C<$events> |
203 |
must be a bitset containing either C<EV::READ>, C<EV::WRITE> or C<EV::READ |
204 |
| EV::WRITE>, indicating the type of I/O event you want to wait for. If |
205 |
you do not want to wait for some I/O event, specify C<undef> for |
206 |
C<$fh_or_undef> and C<0> for C<$events>). |
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|
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If timeout is C<undef> or negative, then there will be no |
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timeout. Otherwise a EV::timer with this value will be started. |
210 |
|
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When an error occurs or either the timeout or I/O watcher triggers, then |
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the callback will be called with the received event set (in general |
213 |
you can expect it to be a combination of C<EV:ERROR>, C<EV::READ>, |
214 |
C<EV::WRITE> and C<EV::TIMEOUT>). |
215 |
|
216 |
EV::once doesn't return anything: the watchers stay active till either |
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of them triggers, then they will be stopped and freed, and the callback |
218 |
invoked. |
219 |
|
220 |
=item EV::feed_fd_event ($fd, $revents) |
221 |
|
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=item $loop->feed_fd_event ($fd, $revents) |
223 |
|
224 |
Feed an event on a file descriptor into EV. EV will react to this call as |
225 |
if the readyness notifications specified by C<$revents> (a combination of |
226 |
C<EV::READ> and C<EV::WRITE>) happened on the file descriptor C<$fd>. |
227 |
|
228 |
=item EV::feed_signal_event ($signal) |
229 |
|
230 |
Feed a signal event into EV. EV will react to this call as if the signal |
231 |
specified by C<$signal> had occured. |
232 |
|
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=back |
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|
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|
236 |
=head1 WATCHER OBJECTS |
237 |
|
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A watcher is an object that gets created to record your interest in some |
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event. For instance, if you want to wait for STDIN to become readable, you |
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would create an EV::io watcher for that: |
241 |
|
242 |
my $watcher = EV::io *STDIN, EV::READ, sub { |
243 |
my ($watcher, $revents) = @_; |
244 |
warn "yeah, STDIN should not be readable without blocking!\n" |
245 |
}; |
246 |
|
247 |
All watchers can be active (waiting for events) or inactive (paused). Only |
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active watchers will have their callbacks invoked. All callbacks will be |
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called with at least two arguments: the watcher and a bitmask of received |
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events. |
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|
252 |
Each watcher type has its associated bit in revents, so you can use the |
253 |
same callback for multiple watchers. The event mask is named after the |
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type, i..e. EV::child sets EV::CHILD, EV::prepare sets EV::PREPARE, |
255 |
EV::periodic sets EV::PERIODIC and so on, with the exception of I/O events |
256 |
(which can set both EV::READ and EV::WRITE bits), and EV::timer (which |
257 |
uses EV::TIMEOUT). |
258 |
|
259 |
In the rare case where one wants to create a watcher but not start it at |
260 |
the same time, each constructor has a variant with a trailing C<_ns> in |
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its name, e.g. EV::io has a non-starting variant EV::io_ns and so on. |
262 |
|
263 |
Please note that a watcher will automatically be stopped when the watcher |
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object is destroyed, so you I<need> to keep the watcher objects returned by |
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the constructors. |
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|
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Also, all methods changing some aspect of a watcher (->set, ->priority, |
268 |
->fh and so on) automatically stop and start it again if it is active, |
269 |
which means pending events get lost. |
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|
271 |
=head2 COMMON WATCHER METHODS |
272 |
|
273 |
This section lists methods common to all watchers. |
274 |
|
275 |
=over 4 |
276 |
|
277 |
=item $w->start |
278 |
|
279 |
Starts a watcher if it isn't active already. Does nothing to an already |
280 |
active watcher. By default, all watchers start out in the active state |
281 |
(see the description of the C<_ns> variants if you need stopped watchers). |
282 |
|
283 |
=item $w->stop |
284 |
|
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Stop a watcher if it is active. Also clear any pending events (events that |
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have been received but that didn't yet result in a callback invocation), |
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regardless of whether the watcher was active or not. |
288 |
|
289 |
=item $bool = $w->is_active |
290 |
|
291 |
Returns true if the watcher is active, false otherwise. |
292 |
|
293 |
=item $current_data = $w->data |
294 |
|
295 |
=item $old_data = $w->data ($new_data) |
296 |
|
297 |
Queries a freely usable data scalar on the watcher and optionally changes |
298 |
it. This is a way to associate custom data with a watcher: |
299 |
|
300 |
my $w = EV::timer 60, 0, sub { |
301 |
warn $_[0]->data; |
302 |
}; |
303 |
$w->data ("print me!"); |
304 |
|
305 |
=item $current_cb = $w->cb |
306 |
|
307 |
=item $old_cb = $w->cb ($new_cb) |
308 |
|
309 |
Queries the callback on the watcher and optionally changes it. You can do |
310 |
this at any time without the watcher restarting. |
311 |
|
312 |
=item $current_priority = $w->priority |
313 |
|
314 |
=item $old_priority = $w->priority ($new_priority) |
315 |
|
316 |
Queries the priority on the watcher and optionally changes it. Pending |
317 |
watchers with higher priority will be invoked first. The valid range of |
318 |
priorities lies between EV::MAXPRI (default 2) and EV::MINPRI (default |
319 |
-2). If the priority is outside this range it will automatically be |
320 |
normalised to the nearest valid priority. |
321 |
|
322 |
The default priority of any newly-created watcher is 0. |
323 |
|
324 |
Note that the priority semantics have not yet been fleshed out and are |
325 |
subject to almost certain change. |
326 |
|
327 |
=item $w->invoke ($revents) |
328 |
|
329 |
Call the callback *now* with the given event mask. |
330 |
|
331 |
=item $w->feed_event ($revents) |
332 |
|
333 |
Feed some events on this watcher into EV. EV will react to this call as if |
334 |
the watcher had received the given C<$revents> mask. |
335 |
|
336 |
=item $revents = $w->clear_pending |
337 |
|
338 |
If the watcher is pending, this function returns clears its pending status |
339 |
and returns its C<$revents> bitset (as if its callback was invoked). If the |
340 |
watcher isn't pending it does nothing and returns C<0>. |
341 |
|
342 |
=item $previous_state = $w->keepalive ($bool) |
343 |
|
344 |
Normally, C<EV::loop> will return when there are no active watchers |
345 |
(which is a "deadlock" because no progress can be made anymore). This is |
346 |
convinient because it allows you to start your watchers (and your jobs), |
347 |
call C<EV::loop> once and when it returns you know that all your jobs are |
348 |
finished (or they forgot to register some watchers for their task :). |
349 |
|
350 |
Sometimes, however, this gets in your way, for example when you the module |
351 |
that calls C<EV::loop> (usually the main program) is not the same module |
352 |
as a long-living watcher (for example a DNS client module written by |
353 |
somebody else even). Then you might want any outstanding requests to be |
354 |
handled, but you would not want to keep C<EV::loop> from returning just |
355 |
because you happen to have this long-running UDP port watcher. |
356 |
|
357 |
In this case you can clear the keepalive status, which means that even |
358 |
though your watcher is active, it won't keep C<EV::loop> from returning. |
359 |
|
360 |
The initial value for keepalive is true (enabled), and you cna change it |
361 |
any time. |
362 |
|
363 |
Example: Register an I/O watcher for some UDP socket but do not keep the |
364 |
event loop from running just because of that watcher. |
365 |
|
366 |
my $udp_socket = ... |
367 |
my $udp_watcher = EV::io $udp_socket, EV::READ, sub { ... }; |
368 |
$udp_watcher->keepalive (0); |
369 |
|
370 |
=back |
371 |
|
372 |
|
373 |
=head1 WATCHER TYPES |
374 |
|
375 |
Each of the following subsections describes a single watcher type. |
376 |
|
377 |
=head3 I/O WATCHERS - is this file descriptor readable or writable? |
378 |
|
379 |
=over 4 |
380 |
|
381 |
=item $w = EV::io $fileno_or_fh, $eventmask, $callback |
382 |
|
383 |
=item $w = EV::io_ns $fileno_or_fh, $eventmask, $callback |
384 |
|
385 |
=item $w = $loop->io 8$fileno_or_fh, $eventmask, $callback) |
386 |
|
387 |
=item $w = $loop->io_ns ($fileno_or_fh, $eventmask, $callback) |
388 |
|
389 |
As long as the returned watcher object is alive, call the C<$callback> |
390 |
when at least one of events specified in C<$eventmask> occurs. |
391 |
|
392 |
The $eventmask can be one or more of these constants ORed together: |
393 |
|
394 |
EV::READ wait until read() wouldn't block anymore |
395 |
EV::WRITE wait until write() wouldn't block anymore |
396 |
|
397 |
The C<io_ns> variant doesn't start (activate) the newly created watcher. |
398 |
|
399 |
=item $w->set ($fileno_or_fh, $eventmask) |
400 |
|
401 |
Reconfigures the watcher, see the constructor above for details. Can be |
402 |
called at any time. |
403 |
|
404 |
=item $current_fh = $w->fh |
405 |
|
406 |
=item $old_fh = $w->fh ($new_fh) |
407 |
|
408 |
Returns the previously set filehandle and optionally set a new one. |
409 |
|
410 |
=item $current_eventmask = $w->events |
411 |
|
412 |
=item $old_eventmask = $w->events ($new_eventmask) |
413 |
|
414 |
Returns the previously set event mask and optionally set a new one. |
415 |
|
416 |
=back |
417 |
|
418 |
|
419 |
=head3 TIMER WATCHERS - relative and optionally repeating timeouts |
420 |
|
421 |
=over 4 |
422 |
|
423 |
=item $w = EV::timer $after, $repeat, $callback |
424 |
|
425 |
=item $w = EV::timer_ns $after, $repeat, $callback |
426 |
|
427 |
=item $w = $loop->timer ($after, $repeat, $callback) |
428 |
|
429 |
=item $w = $loop->timer_ns ($after, $repeat, $callback) |
430 |
|
431 |
Calls the callback after C<$after> seconds (which may be fractional). If |
432 |
C<$repeat> is non-zero, the timer will be restarted (with the $repeat |
433 |
value as $after) after the callback returns. |
434 |
|
435 |
This means that the callback would be called roughly after C<$after> |
436 |
seconds, and then every C<$repeat> seconds. The timer does his best not |
437 |
to drift, but it will not invoke the timer more often then once per event |
438 |
loop iteration, and might drift in other cases. If that isn't acceptable, |
439 |
look at EV::periodic, which can provide long-term stable timers. |
440 |
|
441 |
The timer is based on a monotonic clock, that is, if somebody is sitting |
442 |
in front of the machine while the timer is running and changes the system |
443 |
clock, the timer will nevertheless run (roughly) the same time. |
444 |
|
445 |
The C<timer_ns> variant doesn't start (activate) the newly created watcher. |
446 |
|
447 |
=item $w->set ($after, $repeat) |
448 |
|
449 |
Reconfigures the watcher, see the constructor above for details. Can be called at |
450 |
any time. |
451 |
|
452 |
=item $w->again |
453 |
|
454 |
Similar to the C<start> method, but has special semantics for repeating timers: |
455 |
|
456 |
If the timer is active and non-repeating, it will be stopped. |
457 |
|
458 |
If the timer is active and repeating, reset the timeout to occur |
459 |
C<$repeat> seconds after now. |
460 |
|
461 |
If the timer is inactive and repeating, start it using the repeat value. |
462 |
|
463 |
Otherwise do nothing. |
464 |
|
465 |
This behaviour is useful when you have a timeout for some IO |
466 |
operation. You create a timer object with the same value for C<$after> and |
467 |
C<$repeat>, and then, in the read/write watcher, run the C<again> method |
468 |
on the timeout. |
469 |
|
470 |
=back |
471 |
|
472 |
|
473 |
=head3 PERIODIC WATCHERS - to cron or not to cron? |
474 |
|
475 |
=over 4 |
476 |
|
477 |
=item $w = EV::periodic $at, $interval, $reschedule_cb, $callback |
478 |
|
479 |
=item $w = EV::periodic_ns $at, $interval, $reschedule_cb, $callback |
480 |
|
481 |
=item $w = $loop->periodic ($at, $interval, $reschedule_cb, $callback) |
482 |
|
483 |
=item $w = $loop->periodic_ns ($at, $interval, $reschedule_cb, $callback) |
484 |
|
485 |
Similar to EV::timer, but is not based on relative timeouts but on |
486 |
absolute times. Apart from creating "simple" timers that trigger "at" the |
487 |
specified time, it can also be used for non-drifting absolute timers and |
488 |
more complex, cron-like, setups that are not adversely affected by time |
489 |
jumps (i.e. when the system clock is changed by explicit date -s or other |
490 |
means such as ntpd). It is also the most complex watcher type in EV. |
491 |
|
492 |
It has three distinct "modes": |
493 |
|
494 |
=over 4 |
495 |
|
496 |
=item * absolute timer ($interval = $reschedule_cb = 0) |
497 |
|
498 |
This time simply fires at the wallclock time C<$at> and doesn't repeat. It |
499 |
will not adjust when a time jump occurs, that is, if it is to be run |
500 |
at January 1st 2011 then it will run when the system time reaches or |
501 |
surpasses this time. |
502 |
|
503 |
=item * non-repeating interval timer ($interval > 0, $reschedule_cb = 0) |
504 |
|
505 |
In this mode the watcher will always be scheduled to time out at the |
506 |
next C<$at + N * $interval> time (for some integer N) and then repeat, |
507 |
regardless of any time jumps. |
508 |
|
509 |
This can be used to create timers that do not drift with respect to system |
510 |
time: |
511 |
|
512 |
my $hourly = EV::periodic 0, 3600, 0, sub { print "once/hour\n" }; |
513 |
|
514 |
That doesn't mean there will always be 3600 seconds in between triggers, |
515 |
but only that the the clalback will be called when the system time shows a |
516 |
full hour (UTC). |
517 |
|
518 |
Another way to think about it (for the mathematically inclined) is that |
519 |
EV::periodic will try to run the callback in this mode at the next |
520 |
possible time where C<$time = $at (mod $interval)>, regardless of any time |
521 |
jumps. |
522 |
|
523 |
=item * manual reschedule mode ($reschedule_cb = coderef) |
524 |
|
525 |
In this mode $interval and $at are both being ignored. Instead, each |
526 |
time the periodic watcher gets scheduled, the reschedule callback |
527 |
($reschedule_cb) will be called with the watcher as first, and the current |
528 |
time as second argument. |
529 |
|
530 |
I<This callback MUST NOT stop or destroy this or any other periodic |
531 |
watcher, ever>. If you need to stop it, return 1e30 and stop it |
532 |
afterwards. |
533 |
|
534 |
It must return the next time to trigger, based on the passed time value |
535 |
(that is, the lowest time value larger than to the second argument). It |
536 |
will usually be called just before the callback will be triggered, but |
537 |
might be called at other times, too. |
538 |
|
539 |
This can be used to create very complex timers, such as a timer that |
540 |
triggers on each midnight, local time (actually 24 hours after the last |
541 |
midnight, to keep the example simple. If you know a way to do it correctly |
542 |
in about the same space (without requiring elaborate modules), drop me a |
543 |
note :): |
544 |
|
545 |
my $daily = EV::periodic 0, 0, sub { |
546 |
my ($w, $now) = @_; |
547 |
|
548 |
use Time::Local (); |
549 |
my (undef, undef, undef, $d, $m, $y) = localtime $now; |
550 |
86400 + Time::Local::timelocal 0, 0, 0, $d, $m, $y |
551 |
}, sub { |
552 |
print "it's midnight or likely shortly after, now\n"; |
553 |
}; |
554 |
|
555 |
=back |
556 |
|
557 |
The C<periodic_ns> variant doesn't start (activate) the newly created watcher. |
558 |
|
559 |
=item $w->set ($at, $interval, $reschedule_cb) |
560 |
|
561 |
Reconfigures the watcher, see the constructor above for details. Can be called at |
562 |
any time. |
563 |
|
564 |
=item $w->again |
565 |
|
566 |
Simply stops and starts the watcher again. |
567 |
|
568 |
=item $time = $w->at |
569 |
|
570 |
Return the time that the watcher is expected to trigger next. |
571 |
|
572 |
=back |
573 |
|
574 |
|
575 |
=head3 SIGNAL WATCHERS - signal me when a signal gets signalled! |
576 |
|
577 |
=over 4 |
578 |
|
579 |
=item $w = EV::signal $signal, $callback |
580 |
|
581 |
=item $w = EV::signal_ns $signal, $callback |
582 |
|
583 |
Call the callback when $signal is received (the signal can be specified by |
584 |
number or by name, just as with C<kill> or C<%SIG>). |
585 |
|
586 |
EV will grab the signal for the process (the kernel only allows one |
587 |
component to receive a signal at a time) when you start a signal watcher, |
588 |
and removes it again when you stop it. Perl does the same when you |
589 |
add/remove callbacks to C<%SIG>, so watch out. |
590 |
|
591 |
You can have as many signal watchers per signal as you want. |
592 |
|
593 |
The C<signal_ns> variant doesn't start (activate) the newly created watcher. |
594 |
|
595 |
=item $w->set ($signal) |
596 |
|
597 |
Reconfigures the watcher, see the constructor above for details. Can be |
598 |
called at any time. |
599 |
|
600 |
=item $current_signum = $w->signal |
601 |
|
602 |
=item $old_signum = $w->signal ($new_signal) |
603 |
|
604 |
Returns the previously set signal (always as a number not name) and |
605 |
optionally set a new one. |
606 |
|
607 |
=back |
608 |
|
609 |
|
610 |
=head3 CHILD WATCHERS - watch out for process status changes |
611 |
|
612 |
=over 4 |
613 |
|
614 |
=item $w = EV::child $pid, $callback |
615 |
|
616 |
=item $w = EV::child_ns $pid, $callback |
617 |
|
618 |
=item $w = $loop->child ($pid, $callback) |
619 |
|
620 |
=item $w = $loop->child_ns ($pid, $callback) |
621 |
|
622 |
Call the callback when a status change for pid C<$pid> (or any pid if |
623 |
C<$pid> is 0) has been received. More precisely: when the process receives |
624 |
a C<SIGCHLD>, EV will fetch the outstanding exit/wait status for all |
625 |
changed/zombie children and call the callback. |
626 |
|
627 |
It is valid (and fully supported) to install a child watcher after a child |
628 |
has exited but before the event loop has started its next iteration (for |
629 |
example, first you C<fork>, then the new child process might exit, and |
630 |
only then do you install a child watcher in the parent for the new pid). |
631 |
|
632 |
You can access both exit (or tracing) status and pid by using the |
633 |
C<rstatus> and C<rpid> methods on the watcher object. |
634 |
|
635 |
You can have as many pid watchers per pid as you want, they will all be |
636 |
called. |
637 |
|
638 |
The C<child_ns> variant doesn't start (activate) the newly created watcher. |
639 |
|
640 |
=item $w->set ($pid) |
641 |
|
642 |
Reconfigures the watcher, see the constructor above for details. Can be called at |
643 |
any time. |
644 |
|
645 |
=item $current_pid = $w->pid |
646 |
|
647 |
=item $old_pid = $w->pid ($new_pid) |
648 |
|
649 |
Returns the previously set process id and optionally set a new one. |
650 |
|
651 |
=item $exit_status = $w->rstatus |
652 |
|
653 |
Return the exit/wait status (as returned by waitpid, see the waitpid entry |
654 |
in perlfunc). |
655 |
|
656 |
=item $pid = $w->rpid |
657 |
|
658 |
Return the pid of the awaited child (useful when you have installed a |
659 |
watcher for all pids). |
660 |
|
661 |
=back |
662 |
|
663 |
|
664 |
=head3 STAT WATCHERS - did the file attributes just change? |
665 |
|
666 |
=over 4 |
667 |
|
668 |
=item $w = EV::stat $path, $interval, $callback |
669 |
|
670 |
=item $w = EV::stat_ns $path, $interval, $callback |
671 |
|
672 |
=item $w = $loop->stat ($path, $interval, $callback) |
673 |
|
674 |
=item $w = $loop->stat_ns ($path, $interval, $callback) |
675 |
|
676 |
Call the callback when a file status change has been detected on |
677 |
C<$path>. The C<$path> does not need to exist, changing from "path exists" |
678 |
to "path does not exist" is a status change like any other. |
679 |
|
680 |
The C<$interval> is a recommended polling interval for systems where |
681 |
OS-supported change notifications don't exist or are not supported. If |
682 |
you use C<0> then an unspecified default is used (which is highly |
683 |
recommended!), which is to be expected to be around five seconds usually. |
684 |
|
685 |
This watcher type is not meant for massive numbers of stat watchers, |
686 |
as even with OS-supported change notifications, this can be |
687 |
resource-intensive. |
688 |
|
689 |
The C<stat_ns> variant doesn't start (activate) the newly created watcher. |
690 |
|
691 |
=item ... = $w->stat |
692 |
|
693 |
This call is very similar to the perl C<stat> built-in: It stats (using |
694 |
C<lstat>) the path specified in the watcher and sets perls stat cache (as |
695 |
well as EV's idea of the current stat values) to the values found. |
696 |
|
697 |
In scalar context, a boolean is return indicating success or failure of |
698 |
the stat. In list context, the same 13-value list as with stat is returned |
699 |
(except that the blksize and blocks fields are not reliable). |
700 |
|
701 |
In the case of an error, errno is set to C<ENOENT> (regardless of the |
702 |
actual error value) and the C<nlink> value is forced to zero (if the stat |
703 |
was successful then nlink is guaranteed to be non-zero). |
704 |
|
705 |
See also the next two entries for more info. |
706 |
|
707 |
=item ... = $w->attr |
708 |
|
709 |
Just like C<< $w->stat >>, but without the initial stat'ing: this returns |
710 |
the values most recently detected by EV. See the next entry for more info. |
711 |
|
712 |
=item ... = $w->prev |
713 |
|
714 |
Just like C<< $w->stat >>, but without the initial stat'ing: this returns |
715 |
the previous set of values, before the change. |
716 |
|
717 |
That is, when the watcher callback is invoked, C<< $w->prev >> will be set |
718 |
to the values found I<before> a change was detected, while C<< $w->attr >> |
719 |
returns the values found leading to the change detection. The difference (if any) |
720 |
between C<prev> and C<attr> is what triggered the callback. |
721 |
|
722 |
If you did something to the filesystem object and do not want to trigger |
723 |
yet another change, you can call C<stat> to update EV's idea of what the |
724 |
current attributes are. |
725 |
|
726 |
=item $w->set ($path, $interval) |
727 |
|
728 |
Reconfigures the watcher, see the constructor above for details. Can be |
729 |
called at any time. |
730 |
|
731 |
=item $current_path = $w->path |
732 |
|
733 |
=item $old_path = $w->path ($new_path) |
734 |
|
735 |
Returns the previously set path and optionally set a new one. |
736 |
|
737 |
=item $current_interval = $w->interval |
738 |
|
739 |
=item $old_interval = $w->interval ($new_interval) |
740 |
|
741 |
Returns the previously set interval and optionally set a new one. Can be |
742 |
used to query the actual interval used. |
743 |
|
744 |
=back |
745 |
|
746 |
|
747 |
=head3 IDLE WATCHERS - when you've got nothing better to do... |
748 |
|
749 |
=over 4 |
750 |
|
751 |
=item $w = EV::idle $callback |
752 |
|
753 |
=item $w = EV::idle_ns $callback |
754 |
|
755 |
=item $w = $loop->idle ($callback) |
756 |
|
757 |
=item $w = $loop->idle_ns ($callback) |
758 |
|
759 |
Call the callback when there are no other pending watchers of the same or |
760 |
higher priority (excluding check, prepare and other idle watchers of the |
761 |
same or lower priority, of course). They are called idle watchers because |
762 |
when the watcher is the highest priority pending event in the process, the |
763 |
process is considered to be idle at that priority. |
764 |
|
765 |
If you want a watcher that is only ever called when I<no> other events are |
766 |
outstanding you have to set the priority to C<EV::MINPRI>. |
767 |
|
768 |
The process will not block as long as any idle watchers are active, and |
769 |
they will be called repeatedly until stopped. |
770 |
|
771 |
For example, if you have idle watchers at priority C<0> and C<1>, and |
772 |
an I/O watcher at priority C<0>, then the idle watcher at priority C<1> |
773 |
and the I/O watcher will always run when ready. Only when the idle watcher |
774 |
at priority C<1> is stopped and the I/O watcher at priority C<0> is not |
775 |
pending with the C<0>-priority idle watcher be invoked. |
776 |
|
777 |
The C<idle_ns> variant doesn't start (activate) the newly created watcher. |
778 |
|
779 |
=back |
780 |
|
781 |
|
782 |
=head3 PREPARE WATCHERS - customise your event loop! |
783 |
|
784 |
=over 4 |
785 |
|
786 |
=item $w = EV::prepare $callback |
787 |
|
788 |
=item $w = EV::prepare_ns $callback |
789 |
|
790 |
=item $w = $loop->prepare ($callback) |
791 |
|
792 |
=item $w = $loop->prepare_ns 8$callback) |
793 |
|
794 |
Call the callback just before the process would block. You can still |
795 |
create/modify any watchers at this point. |
796 |
|
797 |
See the EV::check watcher, below, for explanations and an example. |
798 |
|
799 |
The C<prepare_ns> variant doesn't start (activate) the newly created watcher. |
800 |
|
801 |
=back |
802 |
|
803 |
|
804 |
=head3 CHECK WATCHERS - customise your event loop even more! |
805 |
|
806 |
=over 4 |
807 |
|
808 |
=item $w = EV::check $callback |
809 |
|
810 |
=item $w = EV::check_ns $callback |
811 |
|
812 |
=item $w = $loop->check ($callback) |
813 |
|
814 |
=item $w = $loop->check_ns ($callback) |
815 |
|
816 |
Call the callback just after the process wakes up again (after it has |
817 |
gathered events), but before any other callbacks have been invoked. |
818 |
|
819 |
This is used to integrate other event-based software into the EV |
820 |
mainloop: You register a prepare callback and in there, you create io and |
821 |
timer watchers as required by the other software. Here is a real-world |
822 |
example of integrating Net::SNMP (with some details left out): |
823 |
|
824 |
our @snmp_watcher; |
825 |
|
826 |
our $snmp_prepare = EV::prepare sub { |
827 |
# do nothing unless active |
828 |
$dispatcher->{_event_queue_h} |
829 |
or return; |
830 |
|
831 |
# make the dispatcher handle any outstanding stuff |
832 |
... not shown |
833 |
|
834 |
# create an I/O watcher for each and every socket |
835 |
@snmp_watcher = ( |
836 |
(map { EV::io $_, EV::READ, sub { } } |
837 |
keys %{ $dispatcher->{_descriptors} }), |
838 |
|
839 |
EV::timer +($event->[Net::SNMP::Dispatcher::_ACTIVE] |
840 |
? $event->[Net::SNMP::Dispatcher::_TIME] - EV::now : 0), |
841 |
0, sub { }, |
842 |
); |
843 |
}; |
844 |
|
845 |
The callbacks are irrelevant (and are not even being called), the |
846 |
only purpose of those watchers is to wake up the process as soon as |
847 |
one of those events occurs (socket readable, or timer timed out). The |
848 |
corresponding EV::check watcher will then clean up: |
849 |
|
850 |
our $snmp_check = EV::check sub { |
851 |
# destroy all watchers |
852 |
@snmp_watcher = (); |
853 |
|
854 |
# make the dispatcher handle any new stuff |
855 |
... not shown |
856 |
}; |
857 |
|
858 |
The callbacks of the created watchers will not be called as the watchers |
859 |
are destroyed before this cna happen (remember EV::check gets called |
860 |
first). |
861 |
|
862 |
The C<check_ns> variant doesn't start (activate) the newly created watcher. |
863 |
|
864 |
=back |
865 |
|
866 |
|
867 |
=head3 FORK WATCHERS - the audacity to resume the event loop after a fork |
868 |
|
869 |
Fork watchers are called when a C<fork ()> was detected. The invocation |
870 |
is done before the event loop blocks next and before C<check> watchers |
871 |
are being called, and only in the child after the fork. |
872 |
|
873 |
=over 4 |
874 |
|
875 |
=item $w = EV::fork $callback |
876 |
|
877 |
=item $w = EV::fork_ns $callback |
878 |
|
879 |
=item $w = $loop->fork ($callback) |
880 |
|
881 |
=item $w = $loop->fork_ns ($callback) |
882 |
|
883 |
Call the callback before the event loop is resumed in the child process |
884 |
after a fork. |
885 |
|
886 |
The C<fork_ns> variant doesn't start (activate) the newly created watcher. |
887 |
|
888 |
=back |
889 |
|
890 |
|
891 |
=head1 PERL SIGNALS |
892 |
|
893 |
While Perl signal handling (C<%SIG>) is not affected by EV, the behaviour |
894 |
with EV is as the same as any other C library: Perl-signals will only be |
895 |
handled when Perl runs, which means your signal handler might be invoked |
896 |
only the next time an event callback is invoked. |
897 |
|
898 |
The solution is to use EV signal watchers (see C<EV::signal>), which will |
899 |
ensure proper operations with regards to other event watchers. |
900 |
|
901 |
If you cannot do this for whatever reason, you can also force a watcher |
902 |
to be called on every event loop iteration by installing a C<EV::check> |
903 |
watcher: |
904 |
|
905 |
my $async_check = EV::check sub { }; |
906 |
|
907 |
This ensures that perl shortly gets into control for a short time, and |
908 |
also ensures slower overall operation. |
909 |
|
910 |
=head1 THREADS |
911 |
|
912 |
Threads are not supported by this module in any way. Perl pseudo-threads |
913 |
is evil stuff and must die. As soon as Perl gains real threads I will work |
914 |
on thread support for it. |
915 |
|
916 |
=head1 FORK |
917 |
|
918 |
Most of the "improved" event delivering mechanisms of modern operating |
919 |
systems have quite a few problems with fork(2) (to put it bluntly: it is |
920 |
not supported and usually destructive). Libev makes it possible to work |
921 |
around this by having a function that recreates the kernel state after |
922 |
fork in the child. |
923 |
|
924 |
On non-win32 platforms, this module requires the pthread_atfork |
925 |
functionality to do this automatically for you. This function is quite |
926 |
buggy on most BSDs, though, so YMMV. The overhead for this is quite |
927 |
negligible, because everything the function currently does is set a flag |
928 |
that is checked only when the event loop gets used the next time, so when |
929 |
you do fork but not use EV, the overhead is minimal. |
930 |
|
931 |
On win32, there is no notion of fork so all this doesn't apply, of course. |
932 |
|
933 |
=cut |
934 |
|
935 |
our $DIED = sub { |
936 |
warn "EV: error in callback (ignoring): $@"; |
937 |
}; |
938 |
|
939 |
default_loop |
940 |
or die 'EV: cannot initialise libev backend. bad $ENV{LIBEV_FLAGS}?'; |
941 |
|
942 |
1; |
943 |
|
944 |
=head1 SEE ALSO |
945 |
|
946 |
L<EV::ADNS> (asynchronous DNS), L<Glib::EV> (makes Glib/Gtk2 use EV as |
947 |
event loop), L<EV::Glib> (embed Glib into EV), L<Coro::EV> (efficient |
948 |
coroutines with EV), L<Net::SNMP::EV> (asynchronous SNMP). |
949 |
|
950 |
=head1 AUTHOR |
951 |
|
952 |
Marc Lehmann <schmorp@schmorp.de> |
953 |
http://home.schmorp.de/ |
954 |
|
955 |
=cut |
956 |
|