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From Robert Newson <robert.new...@gmail.com>
Subject Re: How to know when CouchDB is under heavy load of document writes?
Date Wed, 10 Nov 2010 11:13:05 GMT
One way to detect it is to poll /<dbname> and see how fast the
update_seq is changing. Since you'll need one query per database, this
might not be very useful in general. You can also use iostat (atop,
etc, etc) to detect how hard your disks are working and use that to
determine whether it's ok to start compaction. Of course, once you've
started it you'll have a problem when your write load increases.

What has been done successfully elsewhere is to modify couchdb to
rate-limit compaction processes dynamically, but that's a code fork
and a significant piece of work, though it's surely something that
couchdb will need in a future release.

It sounds like you believe there will be "down time" where few or no
writes are occurring but you are unable to predict when they will be?

B.

On Wed, Nov 10, 2010 at 11:05 AM, Sivan Greenberg <sivan@omniqueue.com> wrote:
> Hi List,
>
>  I would like to find a way to know when CouchDB is under heavy load
> of document writes, to be able to act on this state. What's the way to
> go to achieve this? using _changes or doing anything else that
> requires the spidermoney seems a no go and a performance burden when
> the db is under very high load. My use case is for example, when the
> db is about to be compacted through CRON, I want to disable hits to
> the couchdb to make sure the compaction process does not race with new
> documents being added.
>
> Your feedback greatly appreciated!
>
> Thanks,
>
> -Sivan
>

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