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https://issues.apache.org/jira/browse/CASSANDRA-1391?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13064626#comment-13064626
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Gary Dusbabek commented on CASSANDRA-1391:
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bq. Seems like if we could come up with some way of "ordering" schema components
A lamport-ish clock consisting of node name and counter/timestamp would
probably be sufficient for ordering.
This could be used with an approach that quarantines schema changes for a
period of time. This would allow for changes to come in from throughout the
cluster and would allow them to be reordered before being applied.
I think this is sensible, but still gives some rope from which we can hang
ourselves--the strict predecessor relationship is gone and we'd have to trust
that nodes would be doing the right thing (by applying migrations)
independently after the quarantine is over.
> Allow Concurrent Schema Migrations
> ----------------------------------
>
> Key: CASSANDRA-1391
> URL: https://issues.apache.org/jira/browse/CASSANDRA-1391
> Project: Cassandra
> Issue Type: Improvement
> Components: Core
> Reporter: Stu Hood
> Assignee: Gary Dusbabek
>
> CASSANDRA-1292 fixed multiple migrations started from the same node to
> properly queue themselves, but it is still possible for migrations initiated
> on different nodes to conflict and leave the cluster in a bad state. Since
> the system_add/drop/rename methods are accessible directly from the client
> API, they should be completely safe for concurrent use.
> It should be possible to allow for most types of concurrent migrations by
> converting the UUID schema ID into a VersionVectorClock (as provided by
> CASSANDRA-580).
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