[jira] [Created] (HDFS-5731) Refactoring to define interfaces between BM and NN and simplify the flow between them

["Amir Langer (JIRA)" <ji...@apache.org>]

Amir Langer created HDFS-5731:
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             Summary: Refactoring to define interfaces between BM and NN and simplify the flow between them
                 Key: HDFS-5731
                 URL: https://issues.apache.org/jira/browse/HDFS-5731
             Project: Hadoop HDFS
          Issue Type: Sub-task
          Components: namenode
            Reporter: Amir Langer


Start the separation of BlockManager (BM) from NameNode (NN) by simplifying the flow between the two components and defining API interfaces between them. 
The two components still exist in the same VM and use the same memory space (using the same instances).
Logic to calls from Datanodes should be in the BM.
NN should interact with BM using few calls and BM should use the return types as much as possible to pass information to the NN.
APIs between them should be defined as interfaces so later it can be improved to not use the same object instances and turned into a real protocol.
This still assumes a one to one relation between NN and BM, same VM and does not handle lifecycle of the service.




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