Cron: running a long php file without flaws

It sounds like you might be able to do this entirely in SQL, which would probably avoid problems. If it's a simple nested loop situation, a cross join may do the trick.

Barring that, most other languages won't have problems with memory leaks(*) or timeouts, so choosing something other than PHP would also avoid problems.

(*) 'course, if you're loading gigabytes of data into memory at once, you'll run out of memory. But that's what iterators are for.

Hello,

Thank you for your feedback. I can optimize the DB/queries but my main concern is the guarantee that everything is processed without errors.

Suppose each of the 100 processes take 1 minute. Can php with a long timeout and cron only by them self run for 100m without nay problems?

Is there any daemon/cron alternative that controls this type of process?

I'm very worried about the long time that this task can take!

Thanks

PHP does not inherently leak memory, and it's perfect possible to write a long-running PHP app. The problem is that garbage collection was kind of meh before 5.3. In fact, I'm not sure that it's that much better in 5.3, only that they claim it is. Regardless, if you code carefully, you can do long-running PHP apps.

Years ago, I wrote an IRC bot in PHP that would run for days or weeks at a time (I restarted it when I had to make changes, although I used separate processes for the plugins, which accounted for most updates, so those could be changed on the fly).

In fact, the biggest problem was that the most popular feature of my bot was the integration with a chatterbot, written in C (not by me), and THAT had memory leaks; it could only run for a few days at a time before the memory leak got too bad.

If your logic is fairly straight forward, consider using a stored procedure/function in mysql.

You can also create triggers if you don't want to have it running as a cron job

Eric

@nfn:

Hi,

I have a php file that runs a heavy task.

This file needs to make 2 loops, one in one table and for each result it loops again in another table.

At this time, the 1st table has +- 100 records, so and the second loop with take some time because it needs to export some csv.

I'm planning run this cron hourly, but I have some concerns related to memory exhaustion and timou out.

I can adjust php.ini for cli to a longer timeout and for the nedded memory allocation, but I think there is somehow a better way to do this and to control memory and time needed to do this task.

Is there any better option/daemon/language that let me control the memory usage, the time need to run this task and guarantee that in the final I have everything running smooth and export the data without flaws?

Thanks

Isn't php-cli hardcoded to never timeout no matter what you set in php.ini?

And yeah, it definitely sounds like something you should be able to do in SQL faster and better, at least from the vague description you gave us.

@rsk:

Isn't php-cli hardcoded to never timeout no matter what you set in php.ini?
Yes, unless you manually override it from inside the script by calling settimelimit().

One side effect of this behavior is that if your script hangs for whatever reason, like an infinite loop, it will keep running until you kill it. So if you're going to run complicated PHP scripts repeatedly from cron, it's often a good idea to check if the previous run has completed successfully.

As for memory leaks, they are mostly a thing of the past, unless you use a horribly badly written library. In PHP 5.3, calling gc_enable() at the beginning usually helps, even in the case of rogue libraries.