linkedin/camus — pull request #155 by kurtharriger (2014-12-24 19:41:12+00:00)
Title: Per topic partitioning bug fix and additional extension points

* Fixed bug in partitioners by topic
* Added pluggable offset writers - useful for writing plain text offsets
* Added record partition extension point - useful for updating hive metastore
* Update context when new mapper starts
- hadoop reuses committer and will call setupTask with new context when starting new mapper. Verified context is being changed through the lifecycle of committer.
- addCounts uses this possibly old context. Not certain the behavior is incorrect, but it could be since the output path changes when mapper changes.