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From "Pavel Yaskevich (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-5025) Schema push/pull race
Date Mon, 10 Dec 2012 00:57:21 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-5025?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13527671#comment-13527671
] 

Pavel Yaskevich commented on CASSANDRA-5025:
--------------------------------------------

bq. Since Schema.updateVersion actually reads rows, I wondered if this will be equivalent
to Schema.emptyVersion (perhaps Schema tables themselves are represented already by this point
in time?) Brandon said that he would check this.

If that is bootstrap and node is completely empty thus has newly created system tables Schema.updateVersion
would emit "emptyVersion" as there is no data to be read and empty digest has a constant value.
                
> Schema push/pull race
> ---------------------
>
>                 Key: CASSANDRA-5025
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-5025
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Core
>    Affects Versions: 1.1.0
>            Reporter: Jonathan Ellis
>            Assignee: Jonathan Ellis
>            Priority: Minor
>             Fix For: 1.1.8
>
>         Attachments: 5025.txt, 5025-v2.txt, 5025-v3.txt, 5025-v4.txt, 5025-v5.txt
>
>
> When a schema change is made, the coordinator pushes the delta to the other nodes in
the cluster.  This is more efficient than sending the entire schema.  But the coordinator
also announces the new schema version, so the other nodes' reception of the new version races
with processing the delta, and usually seeing the new schema wins.  So the other nodes also
issue a pull to the coordinator for the entire schema.
> Thus, schema changes tend to become O(n) in the number of KS and CF present.

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