IO::Async::Timer::CounUsernContributed Perl DocuIO::Async::Timer::Countdown(3)NAME
"IO::Async::Timer::Countdown" - event callback after a fixed delay
SYNOPSIS
use IO::Async::Timer::Countdown;
use IO::Async::Loop;
my $loop = IO::Async::Loop->new();
my $timer = IO::Async::Timer::Countdown->new(
delay => 10,
on_expire => sub {
print "Sorry, your time's up\n";
$loop->loop_stop;
},
);
$timer->start;
$loop->add( $timer );
$loop->loop_forever;
DESCRIPTION
This module provides a subclass of IO::Async::Timer for implementing
one-shot fixed delays. The object implements a countdown timer, which
invokes its callback after the given period from when it was started.
After it has expired the Timer may be started again, when it will wait
the same period then invoke the callback again. A timer that is
currently running may be stopped or reset.
For a "Timer" object that repeatedly runs a callback at regular
intervals, see instead IO::Async::Timer::Periodic.
This object may be used in one of two ways; with a callback function,
or as a base class.
Callbacks
If the "on_expire" key is supplied to the constructor, it should
contain a CODE reference to a callback function to be invoked at
the appropriate time:
$on_expire->( $self )
Base Class
If a subclass is built, then it can override the "on_expire"
method.
$self->on_expire()PARAMETERS
The following named parameters may be passed to "new" or "configure":
on_expire => CODE
CODE reference to callback to invoke when the timer expires. If
not supplied, the subclass method will be called instead.
delay => NUM
The delay in seconds after starting the timer until it expires.
Cannot be changed if the timer is running.
Once constructed, the timer object will need to be added to the "Loop"
before it will work. It will also need to be started by the "start"
method.
$timer->reset
If the timer is running, restart the countdown period from now. If the
timer is not running, this method has no effect.
EXAMPLES
Watchdog Timer
Because the "reset" method restarts a running countdown timer back to
its full period, it can be used to implement a watchdog timer. This is
a timer which will not expire provided the method is called at least as
often as it is configured. If the method fails to be called, the timer
will eventually expire and run its callback.
For example, to expire an accepted connection after 30 seconds of
inactivity:
...
on_accept => sub {
my ( $newclient ) = @_;
my $stream;
my $watchdog = IO::Async::Timer::Countdown->new(
delay => 30,
on_expire => sub { $stream->close },
);
$stream->add_child( $watchdog );
$stream = IO::Async::Stream->new(
handle => $newclient,
on_read => sub {
my ( $self, $buffref, $closed ) = @_;
$watchdog->reset;
...
},
on_closed => sub {
$watchdog->stop;
},
) );
$watchdog->start;
$loop->add( $watchdog );
}
AUTHOR
Paul Evans <leonerd@leonerd.org.uk>
perl v5.14.2 2010-06-09 IO::Async::Timer::Countdown(3)
