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From Robert Coli <rc...@eventbrite.com>
Subject Re: SchemaDisagreementError when launching a new Cassandra (1.2.2) cluster ?
Date Mon, 09 Sep 2013 16:51:14 GMT
On Mon, Sep 9, 2013 at 8:07 AM, Alex Heneveld <
alex.heneveld@cloudsoftcorp.com> wrote:

> The problem occurs in about 1 in 4 launches when I start a 2-node cluster,
> where the two machines are configured identically with both nodes as the
> seeds (apart from the listen_address being different). On the problematic
> launches, describing schema versions immediately after start shows that the
> two nodes have different schemas (reported at both nodes) and any attempt
> to work with the nodes returns the SDE.  This is before I attempt to do
> anything to the cluster.  After ~60s the nodes reconcile their differences,
> report a single schema used at both nodes, and I can use the cluster
> without problems.
>

How are you defining the schema?


> I have a workaround, which is to use just one node to seed this initial
> set.  When the set of seeds is cardinality 1, the problem does not occur.
>  However the advice is to use 2 seeds and have them be the same across the
> cluster -- so I'd like to get to the bottom of this!
>

Seed nodes "cannot" bootstrap [1], so if you have RF=N and all nodes as
seeds, I'm not surprised that you are experiencing weird behavior. A node
booting with itself as a seed typically just starts up as a cluster of one.


> I am running Cassandra 1.2.2 running in Amazon, using Brooklyn (
> brooklyn.io) to start and manage it.  I can share test cases,
> cassandra.yaml, logs, etc -- but am starting with the above summary in case
> anyone can point me in the right direction from that.
>

Cassandra 1.2.2 has significant bugs. You should launch with 1.2.9.

1.2.9 also has some bootstrap vs. seed fixes which might help your case.

=Rob
[1] https://issues.apache.org/jira/browse/CASSANDRA-5836

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