CPU usage / Connection problems and sharding - mongodb-user

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Message from discussion CPU usage / Connection problems and sharding
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Subject: Re: [mongodb-user] CPU usage / Connection problems and sharding
From: =?iso-8859-1?Q?Stephan_B=F6sebeck?= <sboeseb...@googlemail.com>
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Date: Wed, 30 May 2012 13:33:26 +0200
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To: mongodb-user@googlegroups.com

Hi Scott,

Lets just answer the questions you asked:
- there are no expensive operations/queries running - the same queries =
work now and in 5 minutes they end in a timeout.
- yes, we us MMS and Munin...
- Version 2.0.2 of MongoDB is installed on all nodes

I was thinking about dropping the sharded collection in order to have it =
re-created as unsharded one getting rid of the balancing issue.

Thanks for the docs you mentioned, I try to configure the balancer only =
to work in the night.




Am 29.05.2012 um 15:15 schrieb Scott Hernandez:

> When there is high cpu are there lots of slow operations? Have you
> checked to make sure there are indexes for these queries and that they
> are efficient? (generally high cpu is caused by queries which cannot
> use an index (efficiently).
>=20
> Are you monitoring with MMS + Munin, or can you provide iostat -xm 2
> data during this periods along with mongostat numbers from each
> primary?
>=20
> You may want to turn off the balancer and see how far out of balance
> your shards gets, or to eliminate balancing as the root cause:
> =
http://www.mongodb.org/display/DOCS/Sharding+Administration#ShardingAdmini=
stration-Balancing
>=20
> In general you don't want to drop a sharded collection as they will
> not only get rid of all the data, but also the sharded metadata about
> the shard key, and will make the collection be un-sharded. There is a
> bug related to dropping a sharded collection, and then adding it back
> -- what version are you using?
>=20
> On Tue, May 29, 2012 at 9:07 AM, Stephan <sboeseb...@googlemail.com> =
wrote:
>> Hi everybody,
>>=20
>> we're using Mongo in our productive environment with 2 shards (each =
part of
>> a replica set). Almost every day I see that several of these nodes do =
have a
>> 100% cpu usage and for some time do not respond to queries. This =
results in
>> Erros and strange behavior of our website. When taking a closer look =
at the
>> mongodb logs, it seems that there is shard reorganizing going on.
>> Unfortunately this causes the java driver to end with an exception =
("can't
>> call something")
>>=20
>> We're actually not sure, if sharing is the right approach here. We =
have a
>> collection where business related events and profiling information is =
being
>> stored. This tend to be several per second and will be processed =
offline.
>> Right now there are about 112847590 entries in this collection, half =
of
>> which in each shard.
>>=20
>> So, my question is: is it possible to optimize sharding so that the
>> reorganization of it does not bring the whole server to stop?
>> And: what happens if i delete a sharded collection in an environment =
where
>> several entries are made in a second? will this work or bring us =
down?
>>=20
>> I was thinking about exporting the data, dropping the sharded =
collection and
>> re-importing the needed data, keep the historic stuff safe.
>>=20
>> Any ideas?
>>=20
>> Thanks
>>=20
>>=20
>> --
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>=20
> --=20
> You received this message because you are subscribed to the Google
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