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From William Oberman <>
Subject Re: system_* consistency level?
Date Thu, 21 Apr 2011 01:16:26 GMT
That was the trick.  Thanks!

On Apr 20, 2011, at 6:05 PM, Jonathan Ellis <> wrote:

> See the comments for describe_schema_versions.
> On Wed, Apr 20, 2011 at 4:59 PM, William Oberman
> <> wrote:
>> Hi,
>> My unit tests started failing once I upgraded from a single node cassandra
>> cluster to a full "N" node cluster (I'm starting with 4).  I had a few
>> various bugs, mostly due to forgetting to read/write at a quorum level in
>> places I needed stronger consistency guarantees.  But, I kept getting
>> random, intermittent failure (the worst kind).  I'm 99% sure I see why,
>> after some painful debugging, but I don't know what to do about it.  The
>> basic flaw in my understanding of cassandra seems to boil down to: I thought
>> system mutations of keyspaces/column families where of a stronger
>> consistency than ONE, but that appears to not be true.  Any way for me to
>> update a cluster at something more like QUORUM?
>> The basic idea is in my unit test.setup() I clone my real keyspace as
>> keyspace_UUID (with all of the exact same CFs) to get a fresh space to play
>> in.  In a single node environment, no issues.  But, in a cluster, it seems
>> that it takes a while for the system_add_keyspace call to propagate.  No
>> worries I think, I just modify my setup() to do
>> describe_keyspace(keyspace_UUID) in a while loop until the cluster is
>> ready.  My random failures drop considerably, but every once and awhile I
>> see a similar kind of failure.  Then I find out that schema updates seem to
>> propagate on a per node basis.  At least, that's what I have to assume as
>> I'm using phpcassa which uses a connection pool, and I see in my logging
>> that my setup() succeeds because one connection in the pool sees the new
>> keyspace, but when my tests run I grab a connection from the pool that is
>> missing it!
>> Do I have a solution other than changing my setup yet again to loop over all
>> cassandra servers doing a describe_keyspace()?
>> --
>> Will Oberman
>> Civic Science, Inc.
>> 3030 Penn Avenue., First Floor
>> Pittsburgh, PA 15201
>> (M) 412-480-7835
>> (E)
> --
> Jonathan Ellis
> Project Chair, Apache Cassandra
> co-founder of DataStax, the source for professional Cassandra support

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