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https://issues.apache.org/jira/browse/SOLR-5473?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13984507#comment-13984507
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Timothy Potter commented on SOLR-5473:
--------------------------------------

Hi Mark,

Just wanted to get your input on the watcher approach I described above:

bq. In terms of what's watched and what is not watched, this patch includes 
code from 5474 (as they were too intimately tied together to keep separated) 
which doesn't watch collection state changes on the client side. Instead the 
client relies on a stateVer check during request processing and receives an 
error from the server if the client state is stale. I too think this is a 
little controversial / confusing and maybe we don't have to keep that as part 
of this solution. It was our mistake to merge those two into a single patch. We 
originally were thinking 5474 was needed to keep the number of watchers on a 
znode to a minimum in the event of many clients using many collections. 
However, I do think this feature can be split out and dealt with in a better 
way, if at all. In other words, split state znodes are watched from server and 
client side.

Basically, our approach is that each core on the cluster-side only watches the 
state znode for the collection it is participating in and on the client-side, 
the CloudSolrServer is not watching any state znodes and instead rely on cached 
DocCollections and stale state checks on the server side when processing client 
requests. Do you have any concerns with us moving forward with this approach? 
Alternatively, the CloudSolrServer on the client-side can use watchers on state 
znodes after dynamically fetching them from the server when a request for a new 
collection comes in.

> Make one state.json per collection
> ----------------------------------
>
>                 Key: SOLR-5473
>                 URL: https://issues.apache.org/jira/browse/SOLR-5473
>             Project: Solr
>          Issue Type: Sub-task
>          Components: SolrCloud
>            Reporter: Noble Paul
>            Assignee: Noble Paul
>             Fix For: 5.0
>
>         Attachments: SOLR-5473-74.patch, SOLR-5473-74.patch, 
> SOLR-5473-74.patch, SOLR-5473-74.patch, SOLR-5473-74.patch, 
> SOLR-5473-74.patch, SOLR-5473-74.patch, SOLR-5473-74.patch, 
> SOLR-5473-74.patch, SOLR-5473-74.patch, SOLR-5473-74.patch, 
> SOLR-5473-74.patch, SOLR-5473-74.patch, SOLR-5473-74.patch, 
> SOLR-5473-74.patch, SOLR-5473-74.patch, SOLR-5473-74.patch, 
> SOLR-5473-74.patch, SOLR-5473-74.patch, SOLR-5473-74.patch, 
> SOLR-5473-74.patch, SOLR-5473-74.patch, SOLR-5473-74.patch, 
> SOLR-5473-74.patch, SOLR-5473.patch, SOLR-5473.patch, SOLR-5473.patch, 
> SOLR-5473.patch, SOLR-5473.patch, SOLR-5473.patch, SOLR-5473.patch, 
> SOLR-5473.patch, SOLR-5473.patch, SOLR-5473.patch, SOLR-5473.patch, 
> SOLR-5473.patch, SOLR-5473.patch, SOLR-5473.patch, SOLR-5473.patch, 
> SOLR-5473.patch, SOLR-5473.patch, SOLR-5473.patch, SOLR-5473_undo.patch, 
> ec2-23-20-119-52_solr.log, ec2-50-16-38-73_solr.log
>
>
> As defined in the parent issue, store the states of each collection under 
> /collections/collectionname/state.json node



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