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https://issues.apache.org/jira/browse/CASSANDRA-10726?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16219254#comment-16219254
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Aleksey Yeschenko commented on CASSANDRA-10726:
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I've been thinking more about this, in particular in context of
deprecating/removing {{read_repair_chance}} and {{dclocal_read_repair_chance}}
options. The question I asked myself was: what kind of tuning do we want for
read repair, once those two are gone?
And I'm leaning towards these three settings:
1. Perform blocking RR (current default, left default)
2. Write hints instead of sending RR mutations, and let hint delivery repair
the inconsistency, in a manner decoupled from the original read request
3. Do nothing, for those who rely on regular repair for one reason or another
(thinking TWCS, DTCS users?)
Any opinions?
> 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
> Assignee: Xiaolong Jiang
> Fix For: 4.x
>
>
> 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 to update out of date replicas is blocking.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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