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https://issues.apache.org/jira/browse/SOLR-8973?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15241697#comment-15241697
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Scott Blum commented on SOLR-8973:
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I'll need to look at the code again and run it to verify, but I'm 99% sure
adding a collection watch to a non-existent collection will cause it to get
mapped as soon as the collection's state node appears. That was for sure my
design intent, so if it doesn't work that way, it's a bug and I'll fix it ASAP.
I'll check it out and get back.
> 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: Shalin Shekhar Mangar
> Labels: collections, patch-available, solrcloud, zookeeper
> Attachments: 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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