dnishimura opened a new pull request #1090: SAMZA-2260: Standalone - 
coordinator stream metadata store lifecycle
URL: https://github.com/apache/samza/pull/1090
 
 
   **Motivation**
   The current implementation of the coordinator stream metadata store's 
`init()` method is an expensive call as it bootstraps the full coordinator 
stream. We want to invoke init() only once during the entire lifecycle of a 
standalone application.
   
   **Implementation**
   This PR instantiates the coordinator stream metadata store from the scope of 
the top-level `LocalApplicationRunner`. This allows other components, such as 
`StreamProcessor`, `JobCoordinator`, `SamzaContainer`, `StartpointManager` and 
other managers, to use the coordinator stream metadata store freely without 
needing to manage its lifecycle.
   
   **Note**
   Currently there are split responsibilities between a ZK metadata store and 
the coordinator stream metadata store. The former is required for JobModel and 
run.id because of the versioning requirements that the coordinator stream 
metadata store cannot provide. The next-gen metadata store will address this 
requirement. The latter is the focus of this PR since its init() call is 
expensive.
   
   Please take a look @shanthoosh 
   CC: @bharathkk 

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