防止PHP脚本同时运行多次的最佳方法？

Question

I have a long running script (anywhere from 30 to 160 seconds, based on settings) that requests data from an API using NuSOAP, based on this data it builds one big ~1000-4000 row insert query. It than truncates a table and inserts the big query.

When I run the scripts too closely timed one after the other it creates a problem where it loses data. I want to prevent this script from being run twice simultaneously.

This script will in the future also be run every ~5-10 minutes via cron/task scheduler.

Currently I block running the script simultaneously by checking if a file exists:

<?php
    header('content-type: application/json');
    ignore_user_abort(true);

    if (!file_exists('lock.txt')) {
        $lock = fopen('lock.txt','w');
        fclose($lock);

        //~450 API requests using NuSOAP.
        //TRUNCATE `table`
        //INSERT ~1000-4000 rows into `table

        $jsonArray = array(utf8_encode('script')=>utf8_encode('finished'));
        unlink('lock.txt');
    } else {
        $jsonArray = array(utf8_encode('script')=>utf8_encode('locked'));
    }
    echo json_encode($jsonArray);
?>

Is this a secure way of blocking a script from being run simultaneously? Is is better to check wether a MySQL column contains 'true' or 'false, instead of a file?

Is there a Better way?

Answer 1

I reckon lock file may not be the ideal, I would rather create a temporary session variable to check 'True' or 'False' to find whether the script running or not.

Optionally, I would also keep track of the actual time taken to execute each script which can be useful to check unnecessary time days and overall average time.

You should be still able to use the session even if you running the script via CRON Scheduler by manually assigning the session_id() before using session_start().

However, the Cookies will be browser dependent and it will not work with Cron.