My group has been having intermittent problems with hanging processes. These programs are binaries and we don't have access to the source code to investigate what is causing the problems. The dead processes cause other problems that I won't go into, but suffice to say that we need an automated way of killing them when they hang.

Today I hacked together this wrapper script with the simple idea that if the problem binary's logfile hasn't been updated in 3 minutes, the process is dead, and is safe to kill. This is our standard criteria for killing this process.

It works famously in testing, but before I migrate it, I wanted to get some feedback about using the alarm function the way I am. Is it safe to reset the alarm in the $SIG{ALRM} intercept? Is it possible for $SIG{ALRM} to not get called after the timeout? Are there handy modules I've never stumbled across that account for wacky edge cases?

This is for AIX Unix with Perl 5.6.0. 

my $timeout = 60;
my $logfile = 'logfile.txt';
my @array = ('the_binary -option1', 'the_binary -option2', 'the_binary
+ -option3');

for (@array) {
    print "Running command $_\n";
    eval {
        local $SIG{ALRM} = sub {
            my $mod_time = time - (stat($logfile))[9];
            if ( $mod_time > 180 ) {
                die "alarm\n";
            }
            else {
                alarm 0;
                alarm $timeout;
            }
        };
        alarm $timeout;
        system($_);
        alarm 0;
    };
}

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In reply to Safety of using alarm by delirium

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