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Sean Bridges commented on CASSANDRA-2494:
-----------------------------------------
I think the guarantee of quorum reads not seeing old writes once a quorum read
sees a new write is very useful. I suspect most people already think that
this guarantee occurs, including, it seems, Jonathan Ellis whose quote can be
found in the email thread linked to in the bug,
"The important guarantee this gives you is that once one quorum read sees the
new value, all others will too. You can't see the newest version, then see an
older version on a subsequent write [sic, I
assume he meant read], which is the characteristic of non-strong consistency"
> Quorum reads are not consistent
> -------------------------------
>
> Key: CASSANDRA-2494
> URL: https://issues.apache.org/jira/browse/CASSANDRA-2494
> Project: Cassandra
> Issue Type: Bug
> Reporter: Sean Bridges
>
> As discussed in this thread,
> http://www.mail-archive.com/user@cassandra.apache.org/msg12421.html
> Quorum reads should be consistent. Assume we have a cluster of 3 nodes
> (X,Y,Z) and a replication factor of 3. If a write of N is committed to X, but
> not Y and Z, then a read from X should not return N unless the read is
> committed to at least two nodes. To ensure this, a read from X should wait
> for an ack of the read repair write from either Y or Z before returning.
> Are there system tests for cassandra? If so, there should be a test similar
> to the original post in the email thread. One thread should write 1,2,3...
> at consistency level ONE. Another thread should read at consistency level
> QUORUM from a random host, and verify that each read is >= the last read.
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