[jira] [Resolved] (HDFS-6019) Standby NN might not checkpoint when processing the rolling upgrade marker

["Jing Zhao (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HDFS-6019?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Jing Zhao resolved HDFS-6019.
-----------------------------

      Resolution: Fixed
    Hadoop Flags: Reviewed

I've committed this.

> Standby NN might not checkpoint when processing the rolling upgrade marker
> --------------------------------------------------------------------------
>
>                 Key: HDFS-6019
>                 URL: https://issues.apache.org/jira/browse/HDFS-6019
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>          Components: datanode, ha, hdfs-client, namenode
>            Reporter: Haohui Mai
>            Assignee: Haohui Mai
>         Attachments: HDFS-6019.000.patch, HDFS-6019.001.patch
>
>
> {{FsEditlogLoader}} will call {{FSNameSystem#triggerRollbackCheckpoint()}} when processing the rollback marker, which looks like the following:
> {code}
> void triggerRollbackCheckpoint() {
>   if (standbyCheckpointer != null) {
>     standbyCheckpointer.triggerRollbackCheckpoint();
>   }
> }
> {code}
> There is a race condition where {{standbyCheckpointer}} can be {{null}}, because in the constructor of the {{NameNode}}, the {{initialize()}} method eventually starts the edit log tailer, but the standby checkpointer is created in {{HAState#enterState()}}. Therefore, the checkpointer might not be able to checkpoint when it sees the marker.



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