See the comments for describe_schema_versions. On Wed, Apr 20, 2011 at 4:59 PM, William Oberman <ober...@civicscience.com> 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) ober...@civicscience.com >
-- Jonathan Ellis Project Chair, Apache Cassandra co-founder of DataStax, the source for professional Cassandra support http://www.datastax.com
