Re: Database queue logic

in reply to Database queue logic

I would add a timestamp column to my process list.
Any process would:

select all processes that have a null timestamp or a timestamp that's older than 10* Minutes
update all selected processes with the timestamp of now.
process all selected processes
delete processed processes

*the 10 Minutes are subject to fiddling

Comment on Re: Database queue logic

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Re^2: Database queue logic by moot (Chaplain) on Jun 14, 2005 at 14:34 UTC
You're still racing between the select and the update, although something like this might work: Update records where 'owner' column is null, with my value and timestamp now(). Select records with my owner value or where timestamp is older than threshold. This catches the case where some records have gone stale because a process died or what-have-you. Process & delete selected records. This way you're letting the database server handle updating the correct records. Depending on how speedily new records are added to the queue, it seems likely that processes will be working with records more than waiting for selects. Of course this approach doesn't help with splitting the records evenly between processes, but neither will a mutex.	[reply]
Re^3: Database queue logic by Marcello (Hermit) on Jun 15, 2005 at 08:05 UTC
Good solution, I will try this approach shortly. Thanks all!	[reply]

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