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From "Matt Foley (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-1879) disambiguate "datanode dead" vs "datanode heartbeat expired"
Date Tue, 03 May 2011 06:10:03 GMT

    [ https://issues.apache.org/jira/browse/HDFS-1879?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13028059#comment-13028059
] 

Matt Foley commented on HDFS-1879:
----------------------------------

The suggested change is:
* rename FSNamesystem.isDatanodeDead() to FSNamesystem.isDatanodeExpired() (This method compares
DatanodeInfo.getLastUpdate() to current time.)
* create a new FSNamesystem.isDatanodeDead(), which queries DatanodeDescriptor.isAlive instead
* change FSNamesystem.heartbeatCheck() to call isDatanodeExpired()
* review other current calls to isDatanodeDead() to see whether intended semantics is best
fit by "datanode has been recognized as dead" (the new isDatanodeDead()) vs "datanode is expired
and might be dead" (the proposed isDatanodeExpired()).

The calls used to build the status web page should probably use the new version of isDatanodeDead().

> disambiguate "datanode dead" vs "datanode heartbeat expired"
> ------------------------------------------------------------
>
>                 Key: HDFS-1879
>                 URL: https://issues.apache.org/jira/browse/HDFS-1879
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: name-node
>    Affects Versions: 0.23.0
>            Reporter: Matt Foley
>            Priority: Minor
>
> HDFS-1541 changed FSNamesystem.heartbeatCheck() so it would not call removeDatanode()
while the name system is in Safe Mode.  However, calls to FSNamesystem.isDatanodeDead() still
show datanodes as dead if their heartbeat is expired, so the Namenode status web page is not
consistent with the intent of HDFS-1541.

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