[jira] [Created] (HDFS-5448) Synchronize NN registrations across block pools

["Arpit Agarwal (JIRA)" <ji...@apache.org>]

Arpit Agarwal created HDFS-5448:
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             Summary: Synchronize NN registrations across block pools
                 Key: HDFS-5448
                 URL: https://issues.apache.org/jira/browse/HDFS-5448
             Project: Hadoop HDFS
          Issue Type: Sub-task
          Components: datanode
    Affects Versions: Heterogeneous Storage (HDFS-2832)
            Reporter: Arpit Agarwal
            Assignee: Arpit Agarwal


Prior to the heterogeneous storage feature, each Datanode had a single storage ID which was generated by the Namenode on first registration. The storage ID used fixed Datanode identifiers like IP address and port, so that in a federated cluster, for example, all NameNodes would generate the same storage ID.

With Heterogeneous storage, we have replaced the storage ID with a per-datanode identifier called the Datanode-UUID. The Datanode UUID is also assigned by a NameNode on first registration. In a federated cluster with multiple namenodes, there are two ways to ensure a unique Datanode UUID allocation:

# Synchronize initial registration requests from the BPServiceActors. If a Datanode UUID is already assigned we don't need to synchronize.
# The datanode assigns itself a UUID on initialization.



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