[jira] [Updated] (ZOOKEEPER-4925) Diff sync introduce hole in stale follower's committedLog which cause data loss in leading

["ASF GitHub Bot (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/ZOOKEEPER-4925?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

ASF GitHub Bot updated ZOOKEEPER-4925:
--------------------------------------
    Labels: pull-request-available  (was: )

> Diff sync introduce hole in stale follower's committedLog which cause data loss in leading
> ------------------------------------------------------------------------------------------
>
>                 Key: ZOOKEEPER-4925
>                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-4925
>             Project: ZooKeeper
>          Issue Type: Bug
>          Components: server
>    Affects Versions: 3.9.3
>            Reporter: Kezhu Wang
>            Assignee: Kezhu Wang
>            Priority: Critical
>              Labels: pull-request-available
>          Time Spent: 10m
>  Remaining Estimate: 0h
>
> There are two variants of {{ZooKeeperServer::processTxn}}. Those two variants diverge in behavior since ZOOKEEPER-3484. {{processTxn(Request request)}} pops outstanding change from {{outstandingChanges}} and adds txn to {{committedLog}} for follower to sync in addition to what {{processTxn(TxnHeader hdr, Record txn)}} does. The {{Learner}} uses {{processTxn(TxnHeader hdr, Record txn)}} to commit txn to memory after ZOOKEEPER-4394, which means it leaves {{committedLog}} untouched in {{SYNCHRONIZATION}} phase.
> In above case, a stale follower will have hole in its {{committedLog}} after joining cluster. The stale follower will propagate the in memory hole to other stale nodes after becoming leader. This causes data loss.



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