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https://issues.apache.org/jira/browse/HDFS-15293?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17088924#comment-17088924
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Chen Liang commented on HDFS-15293:
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The reason this check might be too stringent is that, for example, say we
configure fsImage interval to 6 hours, consider the case when SBN uploads image
A at time 00:00, but there is a minor time skew when ANN actually sees this
fsImage, so ANN sees actually at 00:00.010. When next time SBN uploads next
image at 06:00. And ANN sees this one with a smaller skew at 00:00.005. Then
ANN would consider the time delta is smaller than the configured delta of 6
hours and thus ANN would then reject this image. Despite that there is only a
5ms difference, and should acceptable. Essentially, the current check for exact
timestamp can be too susceptible to random timing conditions.
> Relax FSImage upload time delta check restriction
> -------------------------------------------------
>
> Key: HDFS-15293
> URL: https://issues.apache.org/jira/browse/HDFS-15293
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: namenode
> Reporter: Chen Liang
> Assignee: Chen Liang
> Priority: Major
>
> HDFS-12979 introduced the logic that, if ANN sees consecutive fs image upload
> from Standby with a small delta comparing to previous fsImage. ANN would
> reject this image. This is to avoid overly frequent fsImage in case of when
> there are multiple Standby node. However this check could be too stringent.
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