MultipleRetry policy may retry with an incorrect Consistency level
Description
The MultipleRetry policy always retries with the consistency level coming back from Cassandra, i.e. the one the RetryPolicy callback is called with in onReadTimeout/onUnavailable/etc..
It turns out that in the case of a LWT, Cassandra may return the consistency level it was using during the current phase it encountered the error, e.g. if the error happens during the Paxos phase of a LWT, the consistency lever returned here would be SERIAL or LOCAL_SERIAL, as mentioned here.
So returning a RetryDecision.retry(null) instead of RetryDecision.retry(cl) (cl being the consistency level provided in the callback of the RetryPolicy) would indicate to the Java driver to retry with the statement's original consistency level, and not the one returned by Cassandra.
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Russell Spitzer June 14, 2017 at 10:20 PM
Switched CL to "null" but avoided tryNextHost because of the localNodeFirst policy ... it may make sense to change this in the future ...
Kevin Gallardo May 30, 2017 at 7:29 PM
I also looked at the MultipleRetryPolicy and saw this comment in onUnavailable:
Just wanted to mention that the driver now has a RetryDecision.tryNextHost(ConsistencyLevel cl) in case that may be useful.
The
MultipleRetrypolicy always retries with the consistency level coming back from Cassandra, i.e. the one the RetryPolicy callback is called with inonReadTimeout/onUnavailable/etc..It turns out that in the case of a LWT, Cassandra may return the consistency level it was using during the current phase it encountered the error, e.g. if the error happens during the Paxos phase of a LWT, the consistency lever returned here would be
SERIALorLOCAL_SERIAL, as mentioned here.So returning a
RetryDecision.retry(null)instead ofRetryDecision.retry(cl)(clbeing the consistency level provided in the callback of the RetryPolicy) would indicate to the Java driver to retry with the statement's original consistency level, and not the one returned by Cassandra.