Marcus Eriksson updated CASSANDRA-10726:
    Fix Version/s:     (was: 3.0.x)

> 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 to update out of date replicas is blocking.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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