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https://issues.apache.org/jira/browse/SOLR-6832?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14242231#comment-14242231
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Shawn Heisey commented on SOLR-6832:
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I have concerns, but I don't want to derail the work. There are use-cases for
which this would be very useful, but many other use-cases where it would cause
a single machine to crumble under the load while other machines in the cloud
are nearly idle.
Duplicating what I said on the dev@l.a.o thread:
Consider a SolrCloud that is handling 5000 requests per second with a
replicationFactor of 20 or 30. This could be one shard or multiple shards.
Currently, those requests will be load balanced to the entire cluster. If this
option is implemented, suddenly EVERY request will have at least one part
handled locally ... and unless the index is very tiny or 99 percent of the
queries hit a Solr cache, one index core simply won't be able to handle 5000
queries per second. Getting a single machine capable of handling that load
MIGHT be possible, but it would likely be *VERY* expensive.
This would be great as an *OPTION* that can be enabled when the index
composition and query patterns dictate it will be beneficial ... but it
definitely should not be default behavior.
> 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
>
> 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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