[ACCUMULO-2615] Simplify server configuration caching and ZK watchers

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 1.6.1, 1.7.0
• Assignee: Eric C. Newton
• Reporter: Bill Havanki
• Created: 02/Apr/14 17:13
• Updated: 23/Aug/14 00:38
• Resolved: 01/Aug/14 18:45

Description

The mechanism used for caching server-related configuration objects and processing ZK events could do with some simplification. For example:

• The watcher objects obtain their corresponding configuration objects by reaching through the ServerConfiguration cache, instead of just having a more direct reference.
• The watcher objects set log4j logging levels for both ZK and o.a.hadoop.io.compress to WARN, which prohibits debugging when needed. That should be done in log4j properties/XML instead.
• Possible bug: NamespaceConfWatcher expires table configuration observers, not namespace configuration observers.
• There is high duplication between the static and instance methods of ServerConfiguration. The class serves as both a cache container and a factory. Moreover, despite its name, it isn't actually a configuration object.

I may be missing some subtleties of why things are as they are, so please fill me in as needed.

Issue Links

• breaks: ACCUMULO-3019 Fix ServerConfiguration deprecation
• is depended upon by: ACCUMULO-2603 Create test-friendly way to get Configuration objects
• links to: Review

Sub-Tasks

• Fix ServerConfiguration deprecation: Resolved
• ServerConfigurationFactoryTest is full of commented out and unused code: Resolved