[jira] [Commented] (SOLR-7819) ZkController.ensureReplicaInLeaderInitiatedRecovery does not respect retryOnConnLoss

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

    [ https://issues.apache.org/jira/browse/SOLR-7819?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14639380#comment-14639380 ] 

Shalin Shekhar Mangar commented on SOLR-7819:
---------------------------------------------

[~andyetitmoves] - It looks like the commits for SOLR-7245 only added a retryOnConnLoss parameter but it was never used inside the ZkController.updateLeaderInitiatedRecoveryState method?

Also, now that I am thinking about this change, is it really safe? For example, if a leader was not able to write to a 'live' replica, and during the LIR process if the leader couldn't complete a ZK operation (because retryOnConnLoss=false) then  LIR won't be set and updates can be missed. Also, the code as it is currently written, bails on a ConnectionLossException and doesn't even start a LIR thread which is bad.

I think not having a thread wait for LIR related activity is a noble cause but we should move the entire LIR logic to a background thread which must retry on connection loss until it either succeeds or a session expired exception is thrown.

Thoughts?

> ZkController.ensureReplicaInLeaderInitiatedRecovery does not respect retryOnConnLoss
> ------------------------------------------------------------------------------------
>
>                 Key: SOLR-7819
>                 URL: https://issues.apache.org/jira/browse/SOLR-7819
>             Project: Solr
>          Issue Type: Bug
>          Components: SolrCloud
>    Affects Versions: 5.2, 5.2.1
>            Reporter: Shalin Shekhar Mangar
>              Labels: Jepsen
>             Fix For: 5.3, Trunk
>
>
> SOLR-7245 added a retryOnConnLoss parameter to ZkController.ensureReplicaInLeaderInitiatedRecovery so that indexing threads do not hang during a partition on ZK operations. However, some of those changes were unintentionally reverted by SOLR-7336 in 5.2.
> I found this while running Jepsen tests on 5.2.1 where a hung update managed to put a leader into a 'down' state (I'm still investigating and will open a separate issue about this problem).



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