Perl process controller

0
votes

I want to create a program in perl which is able to start and kill child processes.

Specifics: When given a command, the parent will spawn a new child process and pass it arguments as needed via command line. Once the child process has started the parent will move on and wait for another command. The commands are either to start a process or stop a specific process.

The parent should never wait on the child processes. All children will be able to exit gracefully and cleanup as needed. However, the parent will need to track and kill any individual child process as desired.

I am currently building this parent script but would like to know if I am using the correct perl functions and what's the best practice for doing this.

I will use one of the following Perl functions and a combination of waitpid($pid, WNOHANG) and kill('TERM', $pid). Is this the right approach? Is there a ready-built solution for this? What's the best practice here?

system function exec function backticks (``) operator open function

Here is my working code.

sub spawnNewProcess
{
    my $message = shift;

    # Create a new process
    my $pid = fork;
    if (!$pid)
    {
        # We're in the child process here. We'll spawn an instance and exit once done
        &startInstance( $message );
        die "Instance process for $message->{'instance'} has completed.";
    }
    elsif($pid)
    {
        # We're in the parent here. Let's save the child pid.
        $INSTANCES->{ $message->{'instance'} } = $pid;
    }
}


sub stopInstance
{
    my $message = shift;

    # Check to see if we started the specified instnace 
    my $pid = $INSTANCES->{$message->{'instance'}};
    if( $pid )
    {
        # If we did, then check to see if it's still running
        while( !waitpid($pid, WNOHANG) )
        {
            # If it is, then kill it gently
            kill('TERM', $pid);

            # Wait a couple seconds
            sleep(3);

            # Kill it forceably if gently didn't work
            kill('KILL', $pid) if( !waitpid($pid, WNOHANG) );
        }
    }  
}
1
multithreadingperl
What are you trying to accomplish with this? Maybe you want something like daemontools or supervisord? – jordanm
At first glance I am not sure these programs fit, but will investigate further. They seem like much more than I need and would require more work to get them to do what I want. I really just want a simple start/stop process mechanism in all Perl. Would love to know what others think. – MadHacker

1 Answers