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https://issues.apache.org/jira/browse/BEAM-11832?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17325196#comment-17325196
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Beam JIRA Bot commented on BEAM-11832:
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This issue is P2 but has been unassigned without any comment for 60 days so it
has been labeled "stale-P2". If this issue is still affecting you, we care!
Please comment and remove the label. Otherwise, in 14 days the issue will be
moved to P3.
Please see https://beam.apache.org/contribute/jira-priorities/ for a detailed
explanation of what these priorities mean.
> Time correction by NTP sync can skew metrics
> --------------------------------------------
>
> Key: BEAM-11832
> URL: https://issues.apache.org/jira/browse/BEAM-11832
> Project: Beam
> Issue Type: Bug
> Components: runner-dataflow
> Reporter: Minbo Bae
> Priority: P2
> Labels: stale-P2
> Attachments: clock_correction.png
>
> Time Spent: 10m
> Remaining Estimate: 0h
>
> GCE VM time can be corrected by NTP sync. If this
> happens,`System.currentTimeMillis()` can set back to the past. You may see
> this [^clock_correction.png] in Cloud Logging for time correction.
> The rolled back clock can cause skewed metrics. For example,
> `ExecutionStateSampler` uses `System.currentTimeMillis` [1]. I guess we can
> mitigate this issue using `System.nanoTime` for elapsed times (maybe not
> perfect as per [2]).
> [1]
> [https://github.com/apache/beam/blob/v2.27.0/runners/core-java/src/main/java/org/apache/beam/runners/core/metrics/ExecutionStateSampler.java#L42]
> [2] [https://bugs.openjdk.java.net/browse/JDK-6458294]
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