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From "Aleksey Yeschenko (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-6862) Schema versions mismatch on large ring
Date Tue, 04 Nov 2014 09:29:34 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-6862?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14195950#comment-14195950
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Aleksey Yeschenko commented on CASSANDRA-6862:
----------------------------------------------

bq. Also I think you are saying that 2.0 code will have a schema change and there will be
a schema disagreement after first node is upgraded. But that will settle after all machines
have the new schema.

They won't. They will only settle on a single schema once every single node has been upgraded
- because we don't exchange schema (no push, no pull) between nodes with different major versions
- because of internal migrations like that (if you try to push those new columns created from
aliases to 1.2 nodes, your 1.2 node will not be able to handle it).

So this issue doesn't introduce the problem you are talking about - because it's already there,
since CASSANDRA-5125, which we aren't going to revert.

The only solution is to wait until CASSANDRA-6038 happens - after that, we'll have schema
push/pull/digests done in a separately versioned manner (and instead of having a single current
schema version, have a map {3.0 : f8d559cd7fc723fc176e914d6d71c6f3, 3.1 : f6b405436ca4cb04fd2b4b7be3e8571e}).

> Schema versions mismatch on large ring
> --------------------------------------
>
>                 Key: CASSANDRA-6862
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-6862
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Core
>         Environment: 2.0
>            Reporter: Oleg Anastasyev
>            Assignee: Oleg Anastasyev
>             Fix For: 2.0.7
>
>         Attachments: 6862-v2.txt, SchemaVersionLiveColumns.txt
>
>
> We have a large cluster with several hundreds nodes in 1 ring. Sometimes, especially
after massive restarts, schema versions reported on different nodes mismatch.
> Investigated and found, that difference is not in schema itsself, but in thombstones
(different nodes have different set of thombstones applied to system tables).
> Fixed by digesting schema with thombstones removed first.



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