[HADOOP-6105] Provide a way to automatically handle backward compatibility of deprecated keys

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 0.21.0
• Component/s: conf
• Hadoop Flags: Reviewed
• Assignee: V.V.Chaitanya Krishna
• Reporter: Hemanth Yamijala
• Created: 25/Jun/09 09:51
• Updated: 14/May/11 05:13
• Resolved: 07/Sep/09 15:27

Description

There are cases when we have had to deprecate configuration keys. Use cases include, changing the names of variables to better match intent, splitting a single parameter into two - for maps, reduces etc.

In such cases, we typically provide a backwards compatible option for the old keys. The handling of such cases might typically be common enough to actually add support for it in a generic fashion in the Configuration class. Some initial discussion around this started in HADOOP-5919, but since the project split happened in between we decided to open this issue to fix it in common.

Issue Links

• blocks: HADOOP-6233 Changes in common to rename the config keys as detailed in HDFS-531.
• blocks: MAPREDUCE-849 Renaming of configuration property names in mapreduce
• is depended upon by: HDFS-531 Renaming of configuration keys
• relates to: HADOOP-6243 NPE in handling deprecated configuration keys.
• relates to: HADOOP-6439 Shuffle deadlocks on wrong number of maps
• relates to: HADOOP-6234 Permission configuration files should use octal and symbolic