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https://issues.apache.org/jira/browse/SOLR-8973?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15249310#comment-15249310
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Anshum Gupta commented on SOLR-8973:
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+1 Scott!

> 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, 6.1
>
>         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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