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Posted to dev@lucene.apache.org by "Tomás Fernández Löbbe (JIRA)" <ji...@apache.org> on 2019/08/02 17:03:00 UTC

[jira] [Assigned] (SOLR-13257) Enable replica routing affinity for better cache usage

     [ https://issues.apache.org/jira/browse/SOLR-13257?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Tomás Fernández Löbbe reassigned SOLR-13257:
--------------------------------------------

    Assignee: Tomás Fernández Löbbe

> Enable replica routing affinity for better cache usage
> ------------------------------------------------------
>
>                 Key: SOLR-13257
>                 URL: https://issues.apache.org/jira/browse/SOLR-13257
>             Project: Solr
>          Issue Type: New Feature
>          Components: SolrCloud
>            Reporter: Michael Gibney
>            Assignee: Tomás Fernández Löbbe
>            Priority: Minor
>         Attachments: AffinityShardHandlerFactory.java, SOLR-13257.patch, SOLR-13257.patch
>
>          Time Spent: 2h 20m
>  Remaining Estimate: 0h
>
> For each shard in a distributed request, Solr currently routes each request randomly via [ShufflingReplicaListTransformer|https://github.com/apache/lucene-solr/blob/master/solr/core/src/java/org/apache/solr/handler/component/ShufflingReplicaListTransformer.java] to a particular replica. In setups with replication factor >1, this normally results in a situation where subsequent requests (which one would hope/expect to leverage cached results from previous related requests) end up getting routed to a replica that hasn't seen any related requests.
> The problem can be replicated by issuing a relatively expensive query (maybe containing common terms?). The first request initializes the {{queryResultCache}} on the consulted replicas. If replication factor >1 and there are a sufficient number of shards, subsequent requests will likely be routed to at least one replica that _hasn't_ seen the query before. The replicas with uninitialized caches become a bottleneck, and from the client's perspective, many subsequent requests appear not to benefit from caching at all.



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