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https://issues.apache.org/jira/browse/HDFS-13189?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16831694#comment-16831694
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star commented on HDFS-13189:
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I‘ve proposed a improvement issue HDFS-14378 to put things right once and for
all. The main idea is to make ANN rolling its edit log and download fsimage
randomly from one SNN. SNN will just do checkpointing and tail editlogs. You
are welcome to make a review or make contributions.
> Standby NameNode should roll active edit log when checkpointing
> ---------------------------------------------------------------
>
> Key: HDFS-13189
> URL: https://issues.apache.org/jira/browse/HDFS-13189
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: namenode
> Reporter: Chao Sun
> Priority: Minor
>
> When the SBN is doing checkpointing, it will hold the {{cpLock}}. In the
> current implementation of edit log tailer thread, it will first check and
> roll active edit log, and then tail and apply edits. In the case of
> checkpointing, it will be blocked on the {{cpLock}} and will not roll the
> edit log.
> It seems there is no dependency between the edit log roll and tailing edits,
> so a better may be to do these in separate threads. This will be helpful for
> people who uses the observer feature without in-progress edit log tailing.
> An alternative is to configure
> {{dfs.namenode.edit.log.autoroll.multiplier.threshold}} and
> {{dfs.namenode.edit.log.autoroll.check.interval.ms}} to let ANN roll its own
> log more frequently in case SBN is stuck on the lock.
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