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From Marco Monteiro <ma...@textovirtual.com>
Subject Re: CouchDB freezes
Date Fri, 11 May 2012 12:48:25 GMT
Thanks, Robert.

Disabling delayed commits did make the problem start later, but it is still
there.

It's funny that the first think that I checked when I first saw this
problem was to
make sure that delayed commits where enabled.

Thanks,
Marco

On 11 May 2012 13:20, Robert Newson <rnewson@apache.org> wrote:

> 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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