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Posted to dev@lucene.apache.org by "Scott Blum (JIRA)" <ji...@apache.org> on 2016/04/14 23:16:25 UTC
[jira] [Comment Edited] (SOLR-8973) TX-frenzy on Zookeeper when
collection is put to use
[ https://issues.apache.org/jira/browse/SOLR-8973?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15241923#comment-15241923 ]
Scott Blum edited comment on SOLR-8973 at 4/14/16 9:16 PM:
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[~shalinmangar] I've come to the conclusion that ZkStateReader isn't doing as well as it could be. Adding watchers in constructState() seems (retroactively) like a hack. It doesn't correctly cover the case where a collection parent node exists (e.g. /solr/collections/coll1) but no state.json child yet appears.
I believe I have a patch and test to fix this. Attached it to this JIRA, but not sure if I should create a new one.
was (Author: dragonsinth):
[~shalinmangar] I've come to the conclusion that ZkStateReader isn't doing as well as it could be. Adding watchers in constructState() seems (retroactively) like a hack. It doesn't correctly cover the case where a collection parent node exists (e.g. /solr/collections/coll1) but no state.json child yet appears.
I believe I have a patch and test to fix this. Not sure whether I should attach to this JIRA or create a new one.
> 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-ZkStateReader.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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