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From "Alejandro Fernandez" <>
Subject Review Request 38788: RU - HDFS_Client restart and hdp-select causes dfs_data_dir_mount.hist to be lost
Date Sat, 26 Sep 2015 21:03:59 GMT

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Review request for Ambari, Dmytro Sen, Jayush Luniya, Mahadev Konar, and Sumit Mohanty.

Bugs: AMBARI-13251

Repository: ambari


During the Clients group of RU, restarting hdfs_client changes changes the symlink /usr/hdp/current/hadoop-client/
from the old version to the new version.

Because the Data Dir Mount History file is stored at /etc/hadoop/conf/dfs_data_dir_mount.hist
/etc/hadoop/conf symlinks to /usr/hdp/current/hadoop-client/conf 
it means that the file must be copied to the new location.

Multiple clients (HDFS, HBase, Hive, YARN, MapReduce, Pig, Slider, Tez) actually end up calling
{code}"hadoop-client", params.version)
that changes the symlink, so the first one to be ran during RU must copy the file. If DataNode
is present, it means that HDFS Client is guaranteed to be there, and from all of those clients
it is the first one in the Upgrade Pack.

During a Rolling Downgrade, the file should already exist in the previous version, and the
file is only written to when DataNode is restarted, so we are ok.





Tested the alert during RU, and the mount history file was copied to the new location, so
no warnings were generated.

Python unit tests passed,
Total run:805
Total errors:0
Total failures:0


Alejandro Fernandez

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