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Date: Mon, 7 May 2012 18:16:52 +0000 (UTC)
From: "Greg Bowyer (JIRA)" <jira@apache.org>
To: dev@lucene.apache.org
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Subject: [jira] [Commented] (SOLR-3221) Make Shard handler threadpool
 configurable
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    [ https://issues.apache.org/jira/browse/SOLR-3221?page=3Dcom.atlassian.=
jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=3D13269=
834#comment-13269834 ]=20

Greg Bowyer commented on SOLR-3221:
-----------------------------------

Only to support the exacting behaviour that was in solr prior to this patch=
.
               =20
> 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, 4.0
>            Reporter: Greg Bowyer
>            Assignee: Erick Erickson
>              Labels: distributed, http, shard
>             Fix For: 3.6, 4.0
>
>         Attachments: SOLR-3221-3x_branch.patch, SOLR-3221-3x_branch.patch=
, SOLR-3221-3x_branch.patch, SOLR-3221-3x_branch.patch, SOLR-3221-3x_branch=
.patch, SOLR-3221-trunk.patch, SOLR-3221-trunk.patch, SOLR-3221-trunk.patch=
, SOLR-3221-trunk.patch, SOLR-3221-trunk.patch
>
>
> From profiling of monitor contention, as well as observations of the
> 95th and 99th response times for nodes that perform distributed search
> (or =E2=80=9Faggregator=E2=80=9F nodes) it would appear that the HttpShar=
dHandler 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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