Perl TIMEOUT output message - perl

Question

I'm programming a perl script to monitorize a DB with Nagios.
I'm using alarm function from Time::HiRes library for the timeout.
use Time::HiRes qw[ time alarm ];
alarm $timeout;
Everything works fine. The thing is I want to change the output message cause it returns "Temporizador" and if I do an
echo $?
Returns 142. I want to change the message in order to make an "exit 3" so it can be recognized by Nagios.
Already tried 'eval' but doesn't work.

Answer 1

The function that's taking the time is written in C, which precludes you from using a custom signal handler safely.
You don't appear worried about terminating your program forcefully, so I suggest you use alarm without a signal handler to terminate your program forcefully if it takes too long to run, and using a wrapper to provide the correct response to Nagios.
Change
/path/to/program some args
to
/path/to/timeout_wrapper 30 /path/to/program some args
The following is timeout_wrapper:
#!/usr/bin/perl
use strict;
use warnings;
use POSIX qw( WNOHANG );
use Time::HiRes qw( sleep time );
sub wait_for_child_to_complete {
my ($pid, $timeout) = #_;
my $wait_until = time + $timeout;
while (time < $wait_until) {
waitpid($pid, WNOHANG)
and return $?;
sleep(0.5);
}
return undef;
}
{
my $timeout = shift(#ARGV);
defined( my $pid = fork() )
or exit(3);
if (!$pid) {
alarm($timeout); # Optional. The parent will handle this anyway.
exec(#ARGV)
or exit(3);
}
my $timed_out = 0;
my $rv = wait_for_child_to_complete($pid, $timeout);
if (!defined($rv)) {
$timed_out = 1;
if (kill(ALRM => $pid)) {
$rv = wait_for_child_to_complete($pid, 5);
if (!defined($rv)) {
kill(KILL => $pid)
}
}
}
exit(2) if $timed_out;
exit(3) if $rv & 0x7F; # Killed by some signal.
exit($rv >> 8); # Expect the exit code to comply with the spec.
}
Uses the Nagios Plugin Return Codes. Timeouts should actually return 2.

Answer 2

You should handle the ALRM signal. For example:
#!/usr/bin/env perl
use strict;
use warnings;
use Time::HiRes qw[ time alarm ];
$SIG{ALRM} = sub {print "Custom message\n"; exit 3};
alarm 2;
sleep 10; # this line represents the rest of your program, don't include it
This will output:
18:08:20-eballes#urth:~/$ ./test.pl
Custom message
18:08:23-eballes#urth:~/$ echo $?
3
For an extended explanation about handling signals check this nice tutorial on perltricks.