[jira] [Created] (SOLR-7129) CloudSolrClient can put excessive load on ZooKeeper for collections with stateFormat=2

["Shalin Shekhar Mangar (JIRA)" <ji...@apache.org>]

Shalin Shekhar Mangar created SOLR-7129:
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             Summary: CloudSolrClient can put excessive load on ZooKeeper for collections with stateFormat=2
                 Key: SOLR-7129
                 URL: https://issues.apache.org/jira/browse/SOLR-7129
             Project: Solr
          Issue Type: Bug
          Components: SolrCloud, SolrJ
    Affects Versions: 5.0
            Reporter: Shalin Shekhar Mangar
             Fix For: Trunk, 5.1


Each stale state response from the server causes CloudSolrClient to evict the requested collection from the local cache. At this point, the request is retried and the latest collection state is fetched live from ZooKeeper. There is nothing preventing multiple request threads to simultaneously hit ZooKeeper and cause a thundering herd effect.

We must not only synchronise such refreshes but also use the past and current znode version of the cluster state to make sure that redundant fetches from ZooKeeper are never possible.



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