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Posted to dev@lucene.apache.org by "albert vico oton (JIRA)" <ji...@apache.org> on 2017/03/01 11:44:46 UTC
[jira] [Commented] (SOLR-5872) Eliminate overseer queue
[ https://issues.apache.org/jira/browse/SOLR-5872?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15890021#comment-15890021 ]
albert vico oton commented on SOLR-5872:
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Hello, we are currently trying to do a deploy of around 200 collections and solrcloud can't handle it, it just dies due update_status messages propagation everytime we try to add a new collection, each collection has 3 replicas, and sizes are not very large. Also, I do not see why collection A should be aware of collection B state.
But moving to the topic, overseer node dies since he can not handle all the stress due the flooding of messages. IMHO we have here a single point of failure in a distributed system, which is not very recommended.
since it would be useful for big fat shards, my suggestion would be to make this optional behavior, so people like use who need to have a more distributed approach can make use of solrcloud. Since right now it is impossible to. and I'm not talking about "thousands" of collections actually with as few as 100 we are seeing very bad performance.
> Eliminate overseer queue
> -------------------------
>
> Key: SOLR-5872
> URL: https://issues.apache.org/jira/browse/SOLR-5872
> Project: Solr
> Issue Type: Improvement
> Components: SolrCloud
> Reporter: Noble Paul
> Assignee: Noble Paul
>
> The overseer queue is one of the busiest points in the entire system. The raison d'être of the queue is
> * Provide batching of operations for the main clusterstate,json so that state updates are minimized
> * Avoid race conditions and ensure order
> Now , as we move the individual collection states out of the main clusterstate.json, the batching is not useful anymore.
> Race conditions can easily be solved by using a compare and set in Zookeeper.
> The proposed solution is , whenever an operation is required to be performed on the clusterstate, the same thread (and of course the same JVM)
> # read the fresh state and version of zk node
> # construct the new state
> # perform a compare and set
> # if compare and set fails go to step 1
> This should be limited to all operations performed on external collections because batching would be required for others
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