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From " Brian Hess (JIRA)" <j...@apache.org>
Subject [jira] [Created] (CASSANDRA-8519) Mechanism to determine which nodes own which token ranges without Thrift
Date Fri, 19 Dec 2014 16:20:13 GMT
 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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