[HDFS-5448] Datanode should generate its ID on first registration

• Type: Sub-task
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: Heterogeneous Storage (HDFS-2832)
• Fix Version/s: Heterogeneous Storage (HDFS-2832)
• Component/s: datanode
• Hadoop Flags: Reviewed
• Assignee: Arpit Agarwal
• Reporter: Arpit Agarwal
• Created: 31/Oct/13 21:39
• Updated: 06/Nov/13 03:01
• Resolved: 04/Nov/13 16:00

Description

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:

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