PHP- Need a cron for back site processing on user signup... (or fork process)

Question

Whenever a new user signs up on my site, I want to do some pre-processing to shorten their searches in the future. This involves anywhere from 30 to 2 minutes processing time. Obviously I cannot do this when they click the submit button on signup... or on any PHP page they visit. However, I would like this done within 5 minutes of them signing up (or less).

Cron Route I THINK this needs to be in a cron job, and if so, how should I setup the cron job? If so, what should my cron line look like to run every 2 minutes, and how can I insure that I don't have the same cron job overlapping the next?

Event/Fork Route - Preferred If I can possibly throw some event to my server without disrupting my users experience or fork a process off of the users signup (instead of a cron job) how could I do this?

Answer 1

I would recommend neither solution.

Instead, you would be best off with a long running process (daemon) that gets its jobs from a message queue. The message queue itself could be off a database if that is your preferred method.

You will post an identifier for the job to your database, and then a long running process will iterate through them once in a while and act upon them.

This is as simple as:

<?php
while(true) {
   jobs = getListOfJobsFromDatabase();  // get the jobs from the databbase
   foreach (jobs as job) {
      processAJob(job); // do whatever needs to be done for the job
      deleteJobFromDatabase(job); //remember to delete the job once its done!
   }
   sleep(60); // sleep for a while so it doesnt thrash your database when theres nothing to do
}
?>

And just run that script from the command line.

The benefits of this over a cron job are that you wont get a race condition.

You may also want to fork off the actually processing of the jobs so many can be done in parallel, rather than processing sequentially.

Answer 2

Here's what i think. Have a single cron for all your users. This way you can assure no overlapping by putting them in a table that works like a queue. Run the cron every hour but check the queue first if the queue is not empty. If it's not skip the cron job for the hour try again the next.

Answer 3

You can use the following class to invoke a background PHP task.

class BackgroundProcess {
    static function open($exec, $cwd = null) {
     if (!is_string($cwd)) {
      $cwd = @getcwd();
     }

     @chdir($cwd);

     if (strtoupper(substr(PHP_OS, 0, 3)) == 'WIN') {
      $WshShell = new COM("WScript.Shell");
      $WshShell->CurrentDirectory = str_replace('/', '\\', $cwd);
      $WshShell->Run($exec, 0, false);
     } else {
      exec($exec . " > /dev/null 2>&1 &");
     }
    }

    static function fork($phpScript, $phpExec = null) {
     $cwd = dirname($phpScript);

     if (!is_string($phpExec) || !file_exists($phpExec)) {
      if (strtoupper(substr(PHP_OS, 0, 3)) == 'WIN') {
       $phpExec = str_replace('/', '\\', dirname(ini_get('extension_dir'))) . '\php.exe';

       if (@file_exists($phpExec)) {
        BackgroundProcess::open(escapeshellarg($phpExec) . " " . escapeshellarg($phpScript), $cwd);
       }
      } else {
       $phpExec = exec("which php-cli");

       if ($phpExec[0] != '/') {
        $phpExec = exec("which php");
       }

       if ($phpExec[0] == '/') {
        BackgroundProcess::open(escapeshellarg($phpExec) . " " . escapeshellarg($phpScript), $cwd);
       }
      }
     } else {
      if (strtoupper(substr(PHP_OS, 0, 3)) == 'WIN') {
       $phpExec = str_replace('/', '\\', $phpExec);
      }

      BackgroundProcess::open(escapeshellarg($phpExec) . " " . escapeshellarg($phpScript), $cwd);
     }
    }
}

Use as such:

BackgroundProcess::fork('process_user.php');