Shalin Shekhar Mangar created SOLR-6524:
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Summary: Collections left in recovery state after node restart
because recovery sleep time increases exponentially between retries
Key: SOLR-6524
URL: https://issues.apache.org/jira/browse/SOLR-6524
Project: Solr
Issue Type: Bug
Components: SolrCloud
Reporter: Shalin Shekhar Mangar
Fix For: 4.11
The RecoveryStrategy has a retry wait which is exponential in nature. The first
time it waits for 1 second before retrying recovery, then 2 seconds, then 4
seconds and so on.
This causes problems when running a large number of collections in SolrCloud.
We saw a case where there were 500 collections on 3 nodes (1 shard, 3 replicas)
and after a node is restarted, many collections can't come back up from
recovery because:
# The overseer is slow to process events (I'll create another issue for it)
# Because the overseer is slow, cluster state updates are delayed and therefore
recovery cannot succeed (WaitForState hangs while waiting to see recovery state
on replicas)
# Because recovery can't succeed immediately, the recovery thread sleeps for
larger and larger amounts of time
# Even after the whole overseer queue is cleared up, many recovery threads have
such a long sleep that they won't even attempt to recover for many minutes
(upto 10 minutes).
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