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Date: Sun, 26 Sep 2010 21:26:21 -0400
Message-ID: <AANLkTi=0cm4TdAzvEZ=LUP2d=Y28r8zGsouxPe1GBvsQ@mail.gmail.com>
Subject: Re: High number of DigestMismatchException
From: Edward Capriolo <edlinuxguru@gmail.com>
To: user@cassandra.apache.org
Content-Type: text/plain; charset=ISO-8859-1

On Sun, Sep 26, 2010 at 5:33 PM, Jonathan Ellis <jbellis@gmail.com> wrote:
> It may be an indication of a lower-level problem in your cluster, e.g.
> flakey network causing FD false positives causing writes to be
> initially replicated to less than all 3 nodes.
>
> On Sun, Sep 26, 2010 at 11:53 AM, Narendra Sharma
> <narendra.sharma@gmail.com> wrote:
>> We are seeing high number of DigestMismatchException on our Cassandra
>> deployment. We have a cluster of 4 nodes with RF=3 and we read/write in
>> Quorum. I understand some DigestMismatchException is normal and is the
>> mechanism for Cassandra to ensure consistency by doing read-repair.
>>
>> In our case, even though we have 4 clients, only the client that writes the
>> data, read the data because of request sharding at client end. So I would
>> expect the replication to happen fast and data be consistent on the 3 copies
>> before the read hits the cluster. The size of column value is approx 128K.
>> We verified multiple times that the timestamp of all the clients is in sync.
>>
>> Is this something to worry about? How do we troubleshoot if this an issue?
>>
>>
>> Thanks,
>> Naren
>>
>
>
>
> --
> Jonathan Ellis
> Project Chair, Apache Cassandra
> co-founder of Riptano, the source for professional Cassandra support
> http://riptano.com
>

Run nodetool ring on all nodes. If some nodes do not have the right
topology the data might not end up getting written to the nodes it is
supposed to.