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Multithread and locking issue



Op 15/05/20 om 00:36 schreef Stephane Tougard:
> 
> 
> Hello,
> 
> A multithreaded software written in Python is connected with a Postgres
> database. To avoid concurrent access issue with the database, it starts
> a thread who receive all SQL request via queue.put and queue.get (it
> makes only insert, so no issue with the return of the SQL request).
> 
> As long as it runs with 10 threads, no issues. At 100 threads, the
> software is blocked by what I think is a locking issue.
> 
> I guess Python multithreading and queue are working good enough that it
> can handle 100 threads with no issue (give me wrong here), so I guess
> the problem is in my code.

It is not the number of threads in itself that can cause problems. But 
my experience is that if you have an unbounded queue and your producers 
out pace the consumers, that can cause problems. And if you have 100 
times more producers as you have consumers that can easily be the case.

So my advice it to never use an unbounded queue. If the number of 
producers is small I go for a size of 10. If the number of producers 
gets larger, I go for a size between the number of producerers and the
double of that.

-- 
Antoon.