[jira] [Work logged] (BEAM-11832) Time correction by NTP sync can skew metrics

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

     [ https://issues.apache.org/jira/browse/BEAM-11832?focusedWorklogId=554345&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-554345 ]

ASF GitHub Bot logged work on BEAM-11832:
-----------------------------------------

                Author: ASF GitHub Bot
            Created on: 18/Feb/21 17:09
            Start Date: 18/Feb/21 17:09
    Worklog Time Spent: 10m 
      Work Description: pabloem merged pull request #13993:
URL: https://github.com/apache/beam/pull/13993


   


----------------------------------------------------------------
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.

For queries about this service, please contact Infrastructure at:
users@infra.apache.org


Issue Time Tracking
-------------------

            Worklog Id:     (was: 554345)
    Remaining Estimate: 0h
            Time Spent: 10m

> 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
>         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]



--
This message was sent by Atlassian Jira
(v8.3.4#803005)