[HADOOP-6918] Make metrics naming consistent

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.20.2, 0.21.0
• Component/s: metrics
• Hadoop Flags: Incompatible change

Release Note

Harmonizing metrics names to CapitalizedCamelCase.

Examples: bytes_written becomes BytesWritten; threadsBlocked becomes ThreadsBlocked etc.

• Tags: metrics
• Assignee: Luke Lu
• Reporter: Luke Lu
• Created: 23/Aug/10 16:58
• Updated: 30/Jul/14 23:37
• Resolved: 30/Jul/14 23:37

Description

While working HADOOP-6728, I noticed that our metrics naming style is all over the place:

• Capitalized camel case: e.g., "FilesCreated" in namenode metrics and some rpc metrics
• uncapitalized camel case: e.g, "threadsBlocked" in jvm metrics and some rpc metrics
• lowercased underscored: e.g., "bytes_written" in datanode metrics and mapreduce metrics

Let's make them consistent. How about uncapitalized camel case? My main reason for the camel case: some backends have limits on the name length and underscore is wasteful.

Once we have a consistent naming style we can do:
@Metric("Number of INodes created") MutableCounterLong filesCreated;

instead of the more redundant:
@Metric(

{"FilesCreated", "Number of INodes created"}

) MutableCounterLong filesCreated;

Issue Links

• requires: HADOOP-6920 Metrics2: metrics instrumentation
• requires: HDFS-1117 HDFS portion of HADOOP-6728 (ovehaul metrics framework)
• requires: MAPREDUCE-1738 MapReduce portion of HADOOP-6728 (ovehaul metrics framework)