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From Robert Newson <rnew...@apache.org>
Subject Re: CouchDB freezes
Date Fri, 11 May 2012 12:20:43 GMT
The first thing is to ensure you have disabled delayed commits;

curl -XPUT -d '"false" localhost:5984/_config/couchdb/delayed_commits

This is the production setting anyway (though not the default because
of complaints from incompetent benchmarkers). This will ensure an
fsync for each write and, as a consequence, will greatly smooth your
insert performance. Since you said you were inserting concurrently,
you should not experience a slowdown either.

B.

On 11 May 2012 02:42, Marco Monteiro <marco@textovirtual.com> wrote:
> Hello!
>
> I'm running a load test on CouchDB. I have a cluster of 8 node.js servers
> writing to
> CouchDB. They write about 30000 documents per minute (500 per second).
> There are
> multiple concurrent requests form each server. There are no updates:
> documents are
> created and not modified.
>
> I first tried CouchDB 1.1.1 from Debian 6.4 apt repo. After a few minutes,
> CouchDB
> starts freezing for a period of 1 to 3 seconds about every 10 seconds. It
> keeps this
> behaviour for some time and eventually it starts freezing more frequently
> and for longer
> periods. When the database has about 1.5 million documents, couchdb is
> freezing for
> more than 5 seconds each time.
>
> I then tried CouchDB 1.2, from build-couch. The freezes happen with it
> also, but the
> behavior is much worse: in less than one minute it's freezing for 5 seconds
> or more,
> and it spends more time not doing anything than working.
>
> When testing with 1.1.1 I was writing only to one database. With 1.2 I
> tried with one database
> and then with multiple databases but the problem was exactly the same.
>
> The documents have about 10 properties, only numbers or string and the
> strings are small
> (about 20 chars each). The document IDs are generated in the app and have
> the format
>
>  <milliseconds since epoch>-<random 16 chars string>
>
> When CouchDB freezes, it's processor use (from top) goes to zero. It does
> not reply to read or write
> requests. The disk does not seem to be the  problem as iostat reports near
> 0% utilization.
> CPU is mostly idle, and from the 16 GB of RAM, some of it is free and is
> not even used to
> cache disk.
>
> There are no error message in Couchdb log.
>
> I tried this in two different machines and the problem is the same in both.
>
> I did not change anything in the configuration files expect changing the
> database dir to use
> a RAID partition.
>
> Anyone has any idea of what the problem could be?
>
> Any help solving this issue is greatly appreciated.
>
> Thanks,
> Marco

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