sockets / signals

[RoyHB]

I have a PHP application that runs as a daemon.  the daemon uses fsockopen to connect to an external server.

When the daemon is terminated, for instance during a reboot, it looks like the connections to the remote server are persistent.  The admin of the remote server tells me that he sees some of these connections for days after a daemon instance on my server has dies.

 

My first thought was to use a linux/unix signal to tell the daemon to close the connections before it dies, but I haven't found a way to do that yet.  The daemon seems to respond only to a sig-kill.

 

In a perfect world I'd discover a way for the daemon to always run a function before it shuts down - within the function I'd close the open connections.

 

I'd be very appreciative if someone could point me at either a way to cause a function to execute upon receipt of a sigkill or else a way to cause the daemon to recognise and act on some other less aggressive signal.

 

Thanks

 

 

[RoyHB]

I discovered that it is necessary to call pcntl_signal_dispatch(); from within the main loop of my daemon in order to check whether any signals have been received -  so the code skeleton that works looks like:

 

Signal handler (Near the beginning of the program):

 

    pcntl_signal(SIGTERM, function ($signo) {
        global $handle;
        fclose($handle);
        exit();
    });

 

Code to fork into a background task:

        $pid = pcntl_fork();
        if($pid === -1) echo "error: unable to fork.";
        else if($pid) {
		exit(0);
	}	
        posix_setsid();
        sleep(1);
        ob_start();

 

Somewhere later:

 

$handle = fsockopen(THE_ADDRESS_TO_COMMUNICATE_WITH, THE_PORT_TO_COMMUNICATE_WITH,$sockErrno,$sockErrStr);

 

Then the main loop:

 

while (TRUE) {
    pcntl_signal_dispatch();
    ....  my code that loops doing something that is (hopefully) useful
}

 

More info at:

http://php.net/manual/en/function.pcntl-signal.php

http://php.net/manual/en/function.pcntl-fork.php

http://php.net/manual/en/function.pcntl-signal-dispatch.php