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https://issues.apache.org/jira/browse/SOLR-11932?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16352678#comment-16352678
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Shalin Shekhar Mangar edited comment on SOLR-11932 at 2/5/18 5:41 PM:
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ZkCmdExecutor cannot work on session expiry because the command sent to the
ZkCmdExecutor has an instance of SolrZooKeeper which is no longer usable after
expiry. A new SolrZooKeeper instance must be created after session expiry. The
right way to handle session expiry is to use the OnReconnect hook in
ZkController.addOnReconnectListener and re-initialize state as needed.
was (Author: shalinmangar):
ZkCmdExecutor cannot work on session expiry because the command sent to the
ZkCmdExecutor has an instance of SolrZooKeeper instance is no longer usable
after expiry. A new SolrZooKeeper instance must be created after session
expiry. The right way to handle session expiry is to use the OnReconnect hook
in ZkController.addOnReconnectListener and re-initialize state as needed.
> ZkCmdExecutor: Retry ZkOperation on SessionExpired
> ---------------------------------------------------
>
> Key: SOLR-11932
> URL: https://issues.apache.org/jira/browse/SOLR-11932
> Project: Solr
> Issue Type: Bug
> Security Level: Public(Default Security Level. Issues are Public)
> Affects Versions: 7.2
> Reporter: John Gallagher
> Assignee: Ishan Chattopadhyaya
> Priority: Major
> Attachments: SessionExpiredLog.txt, zk_retry.patch
>
>
> We are seeing situations where an operation, such as changing a replica's
> state to active after a recovery, fails because the zk session has expired.
> However, these operations seem like they are retryable, because the
> ZookeeperConnect receives an event that the session expired and tries to
> reconnect.
> That makes the SessionExpired handling scenario seem very similar to the
> ConnectionLoss handling scenario, so the ZkCmdExecutor seems like it could
> handle them in the same way.
>
> Here's an example stack trace with some slight redactions:
> [^SessionExpiredLog.txt] In this case, a zk operation (a read) failed with a
> SessionExpired event, which seems retriable. The exception kicked off a
> reconnection, but seems like the subsequent operation, (publishing as active)
> failed (perhaps it was using a stale connection handle at that point?)
>
> Regardless, the watch mechanism that reestablishes connection on
> SessionExpired seems sufficient to allow the ZkCmdExecutor to retry that
> operation at a later time and have hope of succeeding.
>
> I have included a simple patch we are trying that catches both exceptions
> instead of just ConnectionLossException: [^zk_retry.patch]
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