Run Function if Different Function Fails to Complete Within Time Frame - php

Question

I already have a function on a website for a client that grabs data from a live server to save it locally, but something I didn't expect was that sometimes these local servers aren't in an area with good service, so every now and then the script dies after a certain amount of time because it failed to connect.
I already have a system implemented to disable external calls for these types of situations, but the clients can't get to the option to set this "Offline Mode" to begin with because the service is bad and the server is trying to reach the live server.
So what I need to do, is wrap my SyncTable function with a function like set_time_limit(8) that calls a different function that sets the "Offline Mode" automatically if the SyncTable Function fails to complete in the 8 seconds.
Is something like this possible? If so, I would love to know how so I can save these clients some time in areas with rough service.

Answer 1

You can accomplish this using proc_open, proc_get_status, and proc_terminate to start the SyncTable operation as a process, monitor it, and terminate it if necessary. Note: You may need to create a simple wrapper script so you can start the SyncTable function as a standalone process.
Here's a function I use to do this and enforce a timeout:
/// Executes a command and returns the output
/// If the timeout value (in seconds) is reached, it terminates the process
/// and returns FALSE
function exec_timeout($cmd, $timeout=30)
{
$descriptors = array(
0 => array('pipe', 'r'), // stdin
1 => array('pipe', 'w'), // stdout
2 => array('pipe', 'w') // stderr
);
$pipes = Array();
$process = proc_open($cmd, $descriptors, $pipes);
$result = '';
$end_time = time() + $timeout;
if (is_resource($process))
{
// set the streams to non-blocking
stream_set_blocking($pipes[0], 0);
stream_set_blocking($pipes[1], 0);
stream_set_blocking($pipes[2], 0);
$timeleft = $end_time - time();
while ($timeleft > 0)
{
$status = proc_get_status($process);
$result .= stream_get_contents($pipes[1]);
// leave the loop if the process has already finished
if (!$status['running'])
break;
$timeleft = $end_time - time();
}
if ($timeleft <= 0)
{
proc_terminate($process);
$result = FALSE;
}
}
// check for errors
$errors = stream_get_contents($pipes[2]);
if (!empty($errors))
fwrite(STDERR, "$errors\n");
// close streams
fclose($pipes[0]);
fclose($pipes[1]);
fclose($pipes[2]);
proc_close($process);
return $result;
}