[KAFKA-7567] Clean up internal metadata usage for consistency and extensibility

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 2.2.0
• Assignee: Jason Gustafson
• Reporter: Jason Gustafson
• Created: 29/Oct/18 23:09
• Updated: 30/Oct/18 20:20
• Resolved: 30/Oct/18 20:20

Description

This refactor has two objectives to improve metadata handling logic and testing:

1. We want to reduce dependence on the public object `Cluster` for internal metadata propagation since it is not easy to evolve. As an example, we need to propagate leader epochs from the metadata response to `Metadata`, but it is not straightforward to do this without exposing it in `PartitionInfo` since that is what `Cluster` uses internally. By doing this change, we are able to remove some redundant `Cluster` building logic.

2. We want to make the metadata handling in `MockClient` simpler and more consistent. Currently we have mix of metadata update mechanisms which are internally inconsistent with each other and also do not match the implementation in `NetworkClient`.

Issue Links

• links to: GitHub Pull Request #5813