Brian Hess created CASSANDRA-8519:
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Summary: Mechanism to determine which nodes own which token ranges
without Thrift
Key: CASSANDRA-8519
URL: https://issues.apache.org/jira/browse/CASSANDRA-8519
Project: Cassandra
Issue Type: Improvement
Components: Core
Reporter: Brian Hess
Right now the only way to determine which nodes own which token ranges is via
the Thrift interface. There is not a Java/CQL driver mechanism to determine
this. Applications that make multiple connections to Cassandra to extract data
in parallel need this ability so they can split the data into pieces, and it is
reasonable to want those splits to be on token range boundaries. Of course,
once you split this way, you would want to route those queries to nodes that
own that token range / split, for efficiency.
This applies for both Hadoop and Spark, but other applications, too. Hadoop
and Spark currently use Thrift to determine this topology.
Additionally, different replication strategies and replication factors result
in different token range ownership, so there will have to be a different answer
based on which keyspace is used.
It would be useful if this data was stored in a CQL table and could be simply
queried. A suggestion would be to add a column to the SYSTEM.SCHEMA_KEYSPACES
table (maybe a complex Map of Host to a UDT that has a List of (beginRange,
endRange) pairs - as an example). This table would need to be updated on an
ALTER KEYSPACE command or on a topology change event. This would allow the
server(s) to hold this information and the drivers could simply query it (as
opposed to having each driver manage this separately).
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