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https://issues.apache.org/jira/browse/CASSANDRA-2662?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13035431#comment-13035431
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Brandon Williams commented on CASSANDRA-2662:
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To clarify what this patch does: on the first round, behavior is unchanged, it
will fall back to the subsnitch as usual. On the second round however, the
nodes will have scores so the dynamic snitch will determine the best host.
This seems like a good idea, but I think we should proceed cautiously with
regard to CASSANDRA-1314. This is certainly going to blow the cache on the
second round, since the unpinned hosts at zero are guaranteed to be ranked
higher than the pinned one. However, in the current implementation, the
badness threshold in CASSANDRA-1519 can never take effect at RR = 0 since the
scores of the other replicas will always be null, and thus diversion to the
subsnitch will always occur, returning the pinned replica. With this patch,
the second replica is likely to end up being the pinned one, which I think will
be ok, as long as all coordinators agree, though this might not always be the
case.
> Nodes get ignored by dynamic snitch when read repair chance is zero
> -------------------------------------------------------------------
>
> Key: CASSANDRA-2662
> URL: https://issues.apache.org/jira/browse/CASSANDRA-2662
> Project: Cassandra
> Issue Type: Bug
> Components: Core
> Affects Versions: 0.7.6
> Reporter: Daniel Doubleday
> Priority: Trivial
> Attachments: dynsnitch.patch
>
>
> DynamicEndpointSnitch falls back to subsnitch when one of the scores of the
> endpoints being compared is missing.
> This leads to a stable order of hosts until reads will lead to recorded
> scores.
> If setting read repair chance to 0 and reads are performed with quorum then
> (rf - # quorum nodes) will never get reads.
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