SYMPTOM: HDP upgrade was failed on HDFS startup. Namenode was not able to start and below were log messages -
ERROR:
From the detailed logs we see below error -
ROOT CAUSE: The above log clearly indicates"ClassNotFound" error. Customer has integrated customer jar in hadoop which was causing the issue.
RESOLUTION: There was custom jar which was already in place with Previous HDP version [located in path -
/usr/hdp/2.4.3.0-37/hadoop/sas*.jar ]. Adding the jar from earlier version to the upgraded version path [ie. /usr/hdp/2.5.3.0-37/hadoop/] resolved the issue.
[Note: There was custom implementation of SAS with hadoop for the setup and hence the custom jars were present in path mentioned above ie. /usr/hdp/2.4.3.0-37/hadoop/sas*.jar. Default setup never includes any custom app/jar implementation with hadoop. It usually refers or org.apache.hadoop class.]
