Benedict created CASSANDRA-14779:
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Summary: Changing EndpointSnitch via JMX has problems
Key: CASSANDRA-14779
URL: https://issues.apache.org/jira/browse/CASSANDRA-14779
Project: Cassandra
Issue Type: Bug
Components: Distributed Metadata
Reporter: Benedict
Fix For: 4.x
The snitch can be set via StorageProxy over JMX, for what reason I’m unsure.
If this were to happen, we might encounter the following problems:
* If the effective local DC were to change, we would not update it. Perhaps
changing the local DC of a node should be rejected and cause it to fail, but
presently, it would simply result in our disagreeing with the snitch.
* During the transition, routing of queries might be broken, as we fetch the
snitch multiple times in different locations when deciding where to route our
query and writes. It’s not clear what the outcome of a discordant view of the
ring would be.
Probably, changing this information in a live cluster is dangerous and we
should actually reject any effective changes to rack, or DC for any node. But
presently we don’t seem to corroborate that this information remains the same.
We don’t seem to perform any cluster wide confirmation that this data is
consistent, generally, which perhaps we should also consider.
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