[jira] [Created] (CASSANDRA-15032) Adjust transient replication keyspace replication options to be more friendly to naive clients

["Andy Tolbert (JIRA)" <ji...@apache.org>]

Andy Tolbert created CASSANDRA-15032:
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             Summary: Adjust transient replication keyspace replication options to be more friendly to naive clients
                 Key: CASSANDRA-15032
                 URL: https://issues.apache.org/jira/browse/CASSANDRA-15032
             Project: Cassandra
          Issue Type: Improvement
          Components: Feature/Transient Replication
            Reporter: Andy Tolbert


To specify the number of transient replicas, replication options are specified like:

{code}
ALTER KEYSPACE foo WITH REPLICATION = {'class' : 'NetworkTopologyStrategy', 'DC1' : '3/1'}; ALTER KEYSPACE foo WITH REPLICATION = {'class' : 'SimpleStrategy', 'replication_factor' : '3/1'}
{code}

It occurred to me that existing client drivers that parse keyspace options may not handle this gracefully.

For example, the datastax java driver tries to parse {{3/1}} as a number and fails.  In this case, the parsing error is not fatal, its just that the metadata for that keyspace in the driver is incomplete, and things like token aware routing can't be utilized.

It is possible that other libraries may not handle this as well.

As an alternative, I propose adding a separate option like: {{'transient_replicas': 1}}.  {{replication_factor}} would represent the total number of replicas (full and transient) in this case.

This would allow existing client libraries to continue working, and while things like routing may be suboptimal (i.e. driver won't know to differentiate between replicas and transient replicas), at least parsing won't fail in possibly fatal ways.





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