CODEWITHSUNDEEP
phpprocessshared-hosting
Greeso
Greeso

Reputation: 8219

How to detect if PHP script is running on a shared server

I have a PHP script that runs on a shared hosting environment server. This PHP script takes a long time to run. It may take 20 to 30 minutes to finish a run. It is a recurring background process. However I do not have control over when the process starts (it could be triggered every five minutes, or every three hours, no one knows).

Anyway, at the beginnin of this script I would like to detect if the previous process is still running, if the earlier run is still running and has not finished, then I would not run the script again. If it is not running, then I run the new process.

In other words, here is a pseudo code. Let's call the script abc.php

1. Start script abc.php
2. Check if an older version of abc.phh is still running. If it is running, then terminate
3. If it is not running, then continue with abc.php and do your work which might take 30 minutes or more

How can I do that? Please keep in mind this is shared hosting.

UPDATE: I was thinking of using a DB detection mechanism. So, when the script starts, it will set a value in a DB as 'STARTED=TRUE', when done, it will set 'STARTED=FALSE'. However this solution is not proper, because there is no garantee that the script will terminate properly. It might get interrupted, and therefore may not update the STARTED value to FALSE. So the DB solution is out of the question. It has to be a process detection of some sort, or maybe a different solution that I did not think off. Thanks.

Upvotes: 1

Views: 743

Answers (2)

dhavald
dhavald

Reputation: 554

You can implement a simple locking mechanism: Create a tmp lock file when script starts and check before if the lock file already exists. If it does, dont run the script, it it doesnt create a lock file and run the script. At then end of successful run, delete the lock file so that it will run properly next time. 

if(!locked()) {
    lock();
    // your code here
    unlock();
} else {
    echo "script already running";
}

function lock()   { file_put_contents("write.lock", 'running'); }
function locked() { return file_exists("write.lock"); }
function unlock() { return unlink("write.lock"); }

Upvotes: 0

Madbreaks
Madbreaks

Reputation: 19539

If this is a CGI process, I would try using exec + ps, if the latter is available in your environment. A quick SO search turns up this answer: https://stackoverflow.com/a/7182595/177920

You'll need to have a script that is responsible for (and separate from) checking to see if your target script is running, of course, otherwise you'll always see that your target script is running based on the order of ops in your "psuedo code".

Upvotes: 1

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