[ACCUMULO-729] refactor core to reduce client application dependency version conflicts

• Type: Sub-task
• Status: Resolved
• Priority: Major
• Resolution: Not A Problem
• Component/s: client
• Assignee: Unassigned
• Reporter: Adam Fuchs
• Created: 14/Aug/12 19:42
• Updated: 03/Mar/21 01:19
• Resolved: 03/Mar/21 01:19

Description

Accumulo client applications often include things like thrift servers. If the client application uses a different version of a library (like libthrift) than the Accumulo client library uses then baby Jesus cries (and it doesn't work).

Version conflicts have been common among our users for the following libraries:

• log4j/slf4j
• thrift
• zookeeper
• hadoop

This problem is solvable with a moderate amount of effort. The Accumulo client library should create a separate classloader to load its dependencies. We can then separate the core code into interfaces and implementations. For example, the following methods can load the implementations through reflection, and all of their dependencies can be contained in that ClassLoader:

• Instance.getConnector(...)
• Instance.getConfiguration(...)
• Instance.*

It's probably only the Instance methods that need to do the reflection trick, since everything else is loaded from a connector, whose implementation would be loaded from the other ClassLoader.

This exercise would also make the Accumulo client API more explicit, which would improve accessibility and reduce the false sense of continuity that may be perceived around some of the classes in core.