[HADOOP-18215] Enhance WritableName to be able to return aliases for classes that use serializers

• Type: Improvement
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 3.4.0, 3.3.6
• Fix Version/s: 3.4.0, 3.3.6
• Component/s: common
• Labels: pull-request-available
• Target Version/s: 3.4.0, 3.3.6
• Hadoop Flags: Reviewed

Release Note

If you have a SequenceFile with an old key or value class which has been renamed, you can use WritableName.addName to add an alias class. This functionality previously existed, but only worked for classes which extend Writable. It now works for any class, notably key or value classes which use io.serializations.

• Assignee: Bryan Beaudreault
• Reporter: Bryan Beaudreault
• Created: 21/Apr/22 20:50
• Updated: 28/Jan/24 08:26
• Resolved: 17/Feb/23 06:07

Description

WritableName allows users shim in aliases for writables, in the case where a SequenceFile was written with a Writable class that has since been renamed or moved to another package. However, this requires that the aliased class extend Writable. 

Separately it's possible to configure jobs with keys and values which don't actually extend Writable. Instead they are meant to be serialized/deserialized using the serialization classes defined in io.serializations config.

Unfortunately, the current implementation does not support these key/value classes. All we need to do to support this is remove the .asSubclass(Writable.class) as is already the case for the default.

Issue Links

• links to: GitHub Pull Request #4215