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https://issues.apache.org/jira/browse/HDFS-8163?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Junping Du updated HDFS-8163:
-----------------------------
    Fix Version/s: 2.8.0

> Using monotonicNow for block report scheduling causes test failures on 
> recently restarted systems
> -------------------------------------------------------------------------------------------------
>
>                 Key: HDFS-8163
>                 URL: https://issues.apache.org/jira/browse/HDFS-8163
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: datanode
>    Affects Versions: 2.6.1
>            Reporter: Arpit Agarwal
>            Assignee: Arpit Agarwal
>            Priority: Blocker
>             Fix For: 2.8.0, 2.7.1, 3.0.0-alpha1
>
>         Attachments: HDFS-8163.01.patch, HDFS-8163.02.patch, 
> HDFS-8163.03.patch
>
>
> {{BPServiceActor#blockReport}} has the following check:
> {code}
>   List<DatanodeCommand> blockReport() throws IOException {
>     // send block report if timer has expired.
>     final long startTime = monotonicNow();
>     if (startTime - lastBlockReport <= dnConf.blockReportInterval) {
>       return null;
>     }
> {code}
> Many tests trigger an immediate block report via 
> {{BPServiceActor#triggerBlockReportForTests}} which sets {{lastBlockReport = 
> 0}}. However if the machine was restarted recently then startTime may be less 
> than {{dnConf.blockReportInterval}} and the block report is not sent.
> {{Time#monotonicNow}} uses {{System#nanoTime}} which represents time elapsed 
> since an arbitrary origin. The time should be used only for comparison with 
> other values returned by {{System#nanoTime}}.



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