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From Suan Aik Yeo <yeosuan...@gmail.com>
Subject Re: Easy way to overload a single node on purpose?
Date Thu, 16 Jun 2011 22:25:32 GMT
> Having a ping column can work if every key is replicated to every node. It
would tell you the cluster is working, sort of. Once the number of nodes is
greater than the RF, it tells you a subset of the nodes works.

The way our check works is that each node checks itself, so in this context
we're not concerned about whether the cluster is "up", but that each
individual node is "up".

So the symptoms I saw, the node actually going "down" etc, were probably due
to many different events happening at the time, and will be very hard to
recreate?

On Thu, Jun 16, 2011 at 6:16 AM, aaron morton <aaron@thelastpickle.com>wrote:

> >     DEBUG 14:36:55,546 ... timed out
>
> Is logged when the coordinator times out waiting for the replicas to
> respond, the timeout setting is rpc_timeout in the yaml file. This results
> in the client getting a TimedOutException.
>
> AFAIK There is no global everything is good / bad flags to check. e.g.
> AFAIK I node will not mark its self down if it runs out of disk space.  So
> you need to monitor the free disk space and alert on that.
>
> Having a ping column can work if every key is replicated to every node. It
> would tell you the cluster is working, sort of. Once the number of nodes is
> greater than the RF, it tells you a subset of the nodes works.
>
> If you google around you'll find discussions about monitoring with munin,
> ganglia, cloud kick and Ops Centre.
>
> If you install mx4j you can access the JMX metrics via HTTP,
>
> Cheers
>
> -----------------
> Aaron Morton
> Freelance Cassandra Developer
> @aaronmorton
> http://www.thelastpickle.com
>
> On 16 Jun 2011, at 10:38, Suan Aik Yeo wrote:
>
> > Here's a weird one... what's the best way to get a Cassandra node into a
> "half-crashed" state?
> >
> > We have a 3-node cluster running 0.7.5. A few days ago this happened
> organically to node1 - the partition the commitlog was on was 100% full and
> there was a "No space left on device" error, and after a while, although the
> cluster and node1 was still up, to the other nodes it was down, and messages
> like:
> >     DEBUG 14:36:55,546 ... timed out
> > started to show up in its debug logs.
> >
> > We have a tool to indicate to the load balancer that a Cassandra node is
> down, but it didn't detect it that time. Now I'm having trouble purposefully
> getting the node back to that state, so that I can try other monitoring
> methods. I've tried to fill up the commitlog partition with other files, and
> although I get the "No space left on device" error, the node still doesn't
> go down and show the other symptoms it showed before.
> >
> > Also, if anyone could recommend a good way for a node itself to detect
> that its in such a state I'd be interested in that too. Currently what we're
> doing is making a "describe_cluster_name()" thrift call, but that still
> worked when the node was "down". I'm thinking of something like
> reading/writing to a fixed value in a keyspace as a check... Unfortunately
> Java-based solutions are out of the question.
> >
> >
> > Thanks,
> > Suan
>
>

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