[jira] [Resolved] (SOLR-8973) TX-frenzy on Zookeeper when collection is put to use

["Scott Blum (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/SOLR-8973?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Scott Blum resolved SOLR-8973.
------------------------------
       Resolution: Fixed
    Fix Version/s: 5.6
                   5.5.1

> TX-frenzy on Zookeeper when collection is put to use
> ----------------------------------------------------
>
>                 Key: SOLR-8973
>                 URL: https://issues.apache.org/jira/browse/SOLR-8973
>             Project: Solr
>          Issue Type: Bug
>          Components: SolrCloud
>    Affects Versions: 5.0, 5.1, 5.2, 5.3, 5.4, 5.5, master, 5.6
>            Reporter: Janmejay Singh
>            Assignee: Scott Blum
>              Labels: collections, patch-available, solrcloud, zookeeper
>             Fix For: master, 5.5.1, 6.1, 5.6
>
>         Attachments: SOLR-8973-ZkStateReader.patch, SOLR-8973.patch, SOLR-8973.patch, SOLR-8973.patch
>
>
> This is to do with a distributed data-race. Core-creation happens at a time when collection is not yet visible to the node. In this case a fallback code-path is used which de-references collection-state lazily (on demand) as opposed to setting a watch and keeping it cached locally.
> Due to this, as requests towards the core mount, it generates ZK fetch for collection proportionately. On a large solr-cloud cluster, this generates several Gbps of TX traffic on ZK nodes. This affects indexing throughput(which floors) in addition to running ZK node out of network bandwidth. 
> On smaller solr-cloud clusters its hard to run into, because probability of this race materializing reduces.



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