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Re: [overpass] [Overpass] Is there a default limit on concurrency?

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  • From: mmd <>
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  • Subject: Re: [overpass] [Overpass] Is there a default limit on concurrency?
  • Date: Mon, 22 Feb 2016 19:24:59 +0100


Am 17.02.2016 um 05:18 schrieb :
> Hi ,
> I have local setup of overpass-api, i face concurrency issues, for 100
> threads with each one query it takes around 18-19 seconds, though
> individually
> each query takes less than a second.
> Can this be altered, lots of requests reach my server at a time, and this is
> causing a lot of time delay :( .Also i came across this field
> max_num_processes
> (
> )
> does this have anything to do with concurrency.

I think max_num_processes sets the maximum number of connections the
dispatcher unix domain socket would accept. You can try to bump up that

In addition, I would suggest to reduce the sleep times in
around line 662 to have faster dispatcher responses. With 100 threads
you just spend too much time waiting otherwise.

if (command == 0)
millisleep(idle_counter < 10 ? idle_counter*10 : 100); <<< replace

Right now, this is at least 10ms or a multiple of 10ms. At the expense
of having a higher CPU consumption of your dispatcher process, you could
try to decrease that value to just 1 ms:


The current polling approach unfortunately doesn't scale perfectly well
to a higher number of concurrent clients. Maybe we'll discuss something
like libevent and an epoll based approach as an alternative.


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