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satvantsingh_190085 avatar image
satvantsingh_190085 asked ·

What is "schema version" and why does a cluster report schema version mismatch?

What means by schema version and why we see schema version mismatch warning in Cassandra ? What happen in background which change the schema version ?


Schema versions:        45ad6427-30a8-3381-9e2c-266b446c6ea7: [192.168.1.2, 192.168.1.3, 192.168.1.4]         c2a2bb4f-7d31-3fb8-a216-00b41a643650: [10.10.1.10]
schema
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1 Answer

bettina.swynnerton avatar image
bettina.swynnerton answered ·

When you change the cassandra schema, for example by adding tables or altering tables, a new schema version is generated to uniquely identify the schema, and the schema change is propagated throughout the cluster. All nodes need to agree on the schema version for proper operation.

If you see more than one schema version in nodetool describecluster, you have a schema disagreement in the cluster, which can cause all sorts of issues.

If only one node has a different schema, try a restart of the node and see if you can achieve schema agreement when it comes back online. In many cases the restart will resolve the schema disagreement.

Check nodetool describecluster: https://docs.datastax.com/en/cassandra-oss/3.0/cassandra/tools/toolsDescribeCluster.html

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