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Posted to commits@cassandra.apache.org by "Richard Low (JIRA)" <ji...@apache.org> on 2016/03/05 01:17:40 UTC
[jira] [Commented] (CASSANDRA-10726) Read repair inserts should not
be blocking
[ https://issues.apache.org/jira/browse/CASSANDRA-10726?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15181335#comment-15181335 ]
Richard Low commented on CASSANDRA-10726:
-----------------------------------------
What do you think [~jbellis] [~slebresne]?
> Read repair inserts should not be blocking
> ------------------------------------------
>
> Key: CASSANDRA-10726
> URL: https://issues.apache.org/jira/browse/CASSANDRA-10726
> Project: Cassandra
> Issue Type: Improvement
> Components: Coordination
> Reporter: Richard Low
>
> Today, if there’s a digest mismatch in a foreground read repair, the insert to update out of date replicas is blocking. This means, if it fails, the read fails with a timeout. If a node is dropping writes (maybe it is overloaded or the mutation stage is backed up for some other reason), all reads to a replica set could fail. Further, replicas dropping writes get more out of sync so will require more read repair.
> The comment on the code for why the writes are blocking is:
> {code}
> // wait for the repair writes to be acknowledged, to minimize impact on any replica that's
> // behind on writes in case the out-of-sync row is read multiple times in quick succession
> {code}
> but the bad side effect is that reads timeout. Either the writes should not be blocking or we should return success for the read even if the write times out.
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