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https://issues.apache.org/jira/browse/SOLR-6832?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14337866#comment-14337866
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Ayon Sinha commented on SOLR-6832:
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Actually, in our experience, network has been the most flaky piece. So any
network hop saved is a big deal.
And again you are right that the root cause (first domino) of the distributed
deadlock is yet to be identified. What we see is when 1 machine in the cluster
goes for a GC pause or traffic spike, it brings down all the other machines be
quickly. The slow machine currently does not tell ZK that its struggling and
hence all other nodes keep sending it queries. This is being addressed in
another JIRA.
This particular patch buys us some time.
> Queries be served locally rather than being forwarded to another replica
> ------------------------------------------------------------------------
>
> Key: SOLR-6832
> URL: https://issues.apache.org/jira/browse/SOLR-6832
> Project: Solr
> Issue Type: Bug
> Components: SolrCloud
> Affects Versions: 4.10.2
> Reporter: Sachin Goyal
> Assignee: Timothy Potter
> Fix For: Trunk, 5.1
>
> Attachments: SOLR-6832.patch, SOLR-6832.patch, SOLR-6832.patch,
> SOLR-6832.patch
>
>
> Currently, I see that code flow for a query in SolrCloud is as follows:
> For distributed query:
> SolrCore -> SearchHandler.handleRequestBody() -> HttpShardHandler.submit()
> For non-distributed query:
> SolrCore -> SearchHandler.handleRequestBody() -> QueryComponent.process()
> \\
> \\
> \\
> For a distributed query, the request is always sent to all the shards even if
> the originating SolrCore (handling the original distributed query) is a
> replica of one of the shards.
> If the original Solr-Core can check itself before sending http requests for
> any shard, we can probably save some network hopping and gain some
> performance.
> \\
> \\
> We can change SearchHandler.handleRequestBody() or HttpShardHandler.submit()
> to fix this behavior (most likely the former and not the latter).
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