[jira] [Created] (AMBARI-13251) RU - HDFS_Client restart and hdp-select causes dfs_data_dir_mount.hist to be lost

["Alejandro Fernandez (JIRA)" <ji...@apache.org>]

Alejandro Fernandez created AMBARI-13251:
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             Summary: RU - HDFS_Client restart and hdp-select causes dfs_data_dir_mount.hist to be lost
                 Key: AMBARI-13251
                 URL: https://issues.apache.org/jira/browse/AMBARI-13251
             Project: Ambari
          Issue Type: Bug
          Components: ambari-server
    Affects Versions: 2.1.2
            Reporter: Alejandro Fernandez
            Assignee: Alejandro Fernandez
            Priority: Blocker
             Fix For: 2.1.2


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 and
/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}
hdp_select.select("hadoop-client", params.version)
{code}
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.



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