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Posted to commits@cassandra.apache.org by "Brandon Williams (Jira)" <ji...@apache.org> on 2021/08/18 12:39:00 UTC
[jira] [Commented] (CASSANDRA-16856) Prevent broken concurrent
schema pulls
[ https://issues.apache.org/jira/browse/CASSANDRA-16856?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17401020#comment-17401020 ]
Brandon Williams commented on CASSANDRA-16856:
----------------------------------------------
+1
> Prevent broken concurrent schema pulls
> --------------------------------------
>
> Key: CASSANDRA-16856
> URL: https://issues.apache.org/jira/browse/CASSANDRA-16856
> Project: Cassandra
> Issue Type: Bug
> Components: Cluster/Gossip
> Reporter: Berenguer Blasi
> Assignee: Berenguer Blasi
> Priority: Normal
> Fix For: 4.1, 3.11.x, 4.0.x
>
>
> There's a race condition around pulling schema changes, that can occur in case the schema changes push/propagation mechanism is not immediately effective (e.g. because of network delay, or because of the pulling node being down, etc.).
> If schema changes happen on node 1, these changes do not reach node 2 immediately through the SCHEMA.PUSH mechanism, and are first recognized during gossiping, the corresponding SCHEMA.PULL request from node 2 can catch the node 1 schema in the middle of it being modified by another schema change request. This can easily lead to problems (e.g. if a new table is being added, and the node 2 request reads the changes that need to be applied to system_schema.tables, but not the ones that need to be applied to system_schema.columns).
> This PR addresses that by synchronizing the SCHEMA.PULL "RPC call" executed in node 1 by a request from node 2 with the method for applying schema changes in node 1.
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