[jira] [Commented] (CASSANDRA-1391) Allow Concurrent Schema Migrations

["Jonathan Ellis (Commented) (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-1391?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13180527#comment-13180527 ] 

Jonathan Ellis commented on CASSANDRA-1391:
-------------------------------------------

While getting rid of avro is great, replacing "serialize to avro" with "serialize to thrift" isn't as much improvement as I was hoping for.  I thought we were on board with modeling the schema "natively" in system columnfamilies as sketched in https://issues.apache.org/jira/browse/CASSANDRA-1391?focusedCommentId=13149875&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-13149875.  Which would allow the apply/diff design I keep talking about instead of having to do that manually in UCF, allow dropping the last_migration_key indirection, pave the way for CASSANDRA-2477, and probably more simplifications.

Is there a reason that doesn't work?
                
> Allow Concurrent Schema Migrations
> ----------------------------------
>
>                 Key: CASSANDRA-1391
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-1391
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>    Affects Versions: 0.7.0
>            Reporter: Stu Hood
>            Assignee: Pavel Yaskevich
>             Fix For: 1.1
>
>         Attachments: 0001-new-migration-schema-and-avro-methods-cleanup.patch, 0002-avro-removal.patch, 0003-oldVersion-removed-new-migration-distribution-schema.patch, CASSANDRA-1391.patch
>
>
> 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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