[HDDS-4525] Replace Hadoop variables and functions in Ozone shell scripts with Ozone-specific ones

• Type: Improvement
• Status: Resolved
• Priority: Critical
• Resolution: Implemented
• Fix Version/s: 1.1.0
• Component/s: Ozone CLI
• Labels: pull-request-available
• Target Version/s: 1.1.0
• Assignee: Attila Doroszlai
• Reporter: Attila Doroszlai
• Created: 30/Nov/20 14:24
• Updated: 01/Jun/23 20:39
• Resolved: 22/Jan/21 08:34

Description

Currently Ozone relies on HADOOP_* environment variables (eg. HADOOP_HOME) for historical and practical reasons (code reuse). This can lead to unexpected results if Hadoop and Ozone are both present on a node and they share their environment. Eg. we had to implement a workaround for finding ozone-config.sh relative to the script being executed when HADOOP_HOME points to Hadoop, not Ozone (HDDS-1912 and HDDS-4450).

Another similar severe problem happens if we would like to access Ozone filesystem both via ozone and hadoop commands. The latter needs shaded Ozone FS JAR in HADOOP_CLASSPATH. The same HADOOP_CLASSPATH results in ClassNotFound for ozone.

The solution proposed in HDDS-1912:

Long-term we may need to replace all the HADOOP_ environment variable with an OZONE_ environment variable, but that would be a significant bigger change.

This would allow using different classpaths, logging parameters, and more.

To be backward compatible, we should use existing HADOOP_ variables as fallback for the corresponding OZONE_ ones, but let OZONE_X take precedence over HADOOP_X if the former is defined.

Issue Links

• fixes: HDDS-2218 Use OZONE_CLASSPATH instead of HADOOP_CLASSPATH
• is required by: IMPALA-9442 Add Ozone to minicluster
• links to: GitHub Pull Request #1667