[HBASE-5980] Scanner responses from RS should include metrics on rows/KVs filtered

• Type: New Feature
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 0.95.2
• Fix Version/s: 1.2.0, 2.0.0
• Component/s: Client, metrics, Operability, regionserver
• Hadoop Flags: Reviewed

Release Note

Adds scan metrics to the result. In the shell, set the ALL_METRICS attribute to true on your scan to see dump of metrics after results (see the scan help for examples).

If you would prefer to see only a subset of the metrics, the METRICS array can be defined to include the names of only the metrics you care about.

• Assignee: Jonathan Lawlor
• Reporter: Todd Lipcon
• Created: 09/May/12 22:53
• Updated: 13/Jun/22 16:22
• Resolved: 21/May/15 18:16

Description

Currently it's difficult to know, when issuing a filter, what percentage of rows were skipped by that filter. We should expose some basic counters back to the client scanner object. For example:

• number of rows filtered by row key alone (filterRowKey())
• number of times each filter response was returned by filterKeyValue() - corresponding to Filter.ReturnCode

What would be slickest is if this could actually return a tree of counters for cases where FilterList or other combining filters are used. But a top-level is a good start.