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From "Jonathan Ellis (JIRA)" <j...@apache.org>
Subject [jira] [Created] (CASSANDRA-2715) simplify schema reconciliation
Date Thu, 26 May 2011 20:32:47 GMT
simplify schema reconciliation
------------------------------

                 Key: CASSANDRA-2715
                 URL: https://issues.apache.org/jira/browse/CASSANDRA-2715
             Project: Cassandra
          Issue Type: Improvement
          Components: Core
    Affects Versions: 0.7.0
            Reporter: Jonathan Ellis
            Assignee: Jonathan Ellis
            Priority: Minor
             Fix For: 0.7.7, 0.8.1


Currently, schema migrations can be replayed from one node to another in any of three ways:

- a node processes a migration from a client, and pushes it to all live nodes (Migration.announce
on the source)
- a node sees that another node's schema version is older than his (MigrationManager.onChange
on the source)
- a node sees that his own schema version is older than another's and makes an explicit request
(MigrationManager.onChange on the target, DefinitionsAnnounceVerbHandler on the source)

The last of these is an optimization that isn't worth the extra complexity -- under normal
conditions, the initial announce from the coordinator updates everyone, and in recovery situations
the latency gain of #3 over #2 is only a few seconds.

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