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From "Mingliang Liu (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HDFS-9129) Move the safemode block count into BlockManager
Date Tue, 27 Oct 2015 04:17:27 GMT

     [ https://issues.apache.org/jira/browse/HDFS-9129?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Mingliang Liu updated HDFS-9129:
    Attachment: HDFS-9129.011.patch

private volatile boolean isInManualSafeMode = false;
private volatile boolean isInResourceLowSafeMode = false;

isInManualSafeMode = !resourcesLow;
isInResourceLowSafeMode = resourcesLow;
How do these two variables synchronize? Is the system in consistent state in the middle of
the execution?

Per offline discussion with [~wheat9], the {{volatile}} keyword is considered premature optimization.
Make {{isInResourceLowSafeMode }} short-circuit {{isInManualSafeMode}} is bad design for incoming
changes. The v11 patch uses synchronized block to make the system stay in consistent state
in the middle of the execution.

The comment for {{BlockManagerSafeMode}} (ahead of the class) is also refined.

> Move the safemode block count into BlockManager
> -----------------------------------------------
>                 Key: HDFS-9129
>                 URL: https://issues.apache.org/jira/browse/HDFS-9129
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>            Reporter: Haohui Mai
>            Assignee: Mingliang Liu
>         Attachments: HDFS-9129.000.patch, HDFS-9129.001.patch, HDFS-9129.002.patch, HDFS-9129.003.patch,
HDFS-9129.004.patch, HDFS-9129.005.patch, HDFS-9129.006.patch, HDFS-9129.007.patch, HDFS-9129.008.patch,
HDFS-9129.009.patch, HDFS-9129.010.patch, HDFS-9129.011.patch
> The {{SafeMode}} needs to track whether there are enough blocks so that the NN can get
out of the safemode. These fields can moved to the {{BlockManager}} class.

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