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https://issues.apache.org/jira/browse/SOLR-3221?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Erick Erickson reassigned SOLR-3221:
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Assignee: Erick Erickson
> Make Shard handler threadpool configurable
> ------------------------------------------
>
> Key: SOLR-3221
> URL: https://issues.apache.org/jira/browse/SOLR-3221
> Project: Solr
> Issue Type: Improvement
> Affects Versions: 3.6
> Reporter: Greg Bowyer
> Assignee: Erick Erickson
> Labels: distributed, http, shard
> Attachments: SOLR-3221-3x_branch.patch
>
>
> From profiling of monitor contention, as well as observations of the
> 95th and 99th response times for nodes that perform distributed search
> (or ‟aggregator‟ nodes) it would appear that the HttpShardHandler code
> currently does a suboptimal job of managing outgoing shard level
> requests.
> Presently the code contained within lucene 3.5's SearchHandler and
> Lucene trunk / 3x's ShardHandlerFactory create arbitrary threads in
> order to service distributed search requests. This is done presently to
> limit the size of the threadpool such that it does not consume resources
> in deployment configurations that do not use distributed search.
> This unfortunately has two impacts on the response time if the node
> coordinating the distribution is under high load.
> The usage of the MaxConnectionsPerHost configuration option results in
> aggressive activity on semaphores within HttpCommons, it has been
> observed that the aggregator can have a response time far greater than
> that of the searchers. The above monitor contention would appear to
> suggest that in some cases its possible for liveness issues to occur and
> for simple queries to be starved of resources simply due to a lack of
> attention from the viewpoint of context switching.
> With, as mentioned above the http commons connection being hotly
> contended
> The fair, queue based configuration eliminates this, at the cost of
> throughput.
> This patch aims to make the threadpool largely configurable allowing for
> those using solr to choose the throughput vs latency balance they
> desire.
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