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https://issues.apache.org/jira/browse/SOLR-5474?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13828662#comment-13828662
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Noble Paul commented on SOLR-5474:
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The parent issue is to enable Solr to deal with a large no:of collections and
hence we are going to see an explosion of the no:of nodeswatching ZK. Assuming
that there will be many more clients than the nodes themselves,
* There will be too many watchers on the main clusterstate
* If there are are multiple state nodes , clients would need to watch those ZK
nodes as well
We want to minimize the load on ZK . Moreover, all clients don't need to be
aware of all collections and their states. It can be fetched lazily on demand
This will be another class extending SolrServer
{code:java}
class LazyCloudSolrServer extends SolrServer {
}
{code}
> Have a new mode for SolrJ to not watch any ZKNode
> -------------------------------------------------
>
> Key: SOLR-5474
> URL: https://issues.apache.org/jira/browse/SOLR-5474
> Project: Solr
> Issue Type: Sub-task
> Components: SolrCloud
> Reporter: Noble Paul
>
> In this mode SolrJ would not watch any ZK node
> It fetches the state on demand and cache the most recently used n
> collections in memory.
> SolrJ would not listen to any ZK node. When a request comes for a collection
> ‘xcoll’
> it would first check if such a collection exists
> If yes it first looks up the details in the local cache for that collection
> If not found in cache , it fetches the node /collections/xcoll/state.json and
> caches the information
> Any query/update will be sent with extra query param specifying the
> collection name , shard name, Role (Leader/Replica), and range (example
> \_target_=xcoll:shard1:L:80000000-b332ffff) . A node would throw an error
> (INVALID_NODE) if it does not the serve the collection/shard/Role/range combo.
> If SolrJ gets INVALID_NODE error it would invalidate the cache and fetch
> fresh state information for that collection (and caches it again)
> If there is a connection timeout, SolrJ assumes the node is down and re-fetch
> the state for the collection and try again
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