[HDFS-10540] Diskbalancer: The CLI error message for disk balancer is not enabled is not clear.

• Type: Sub-task
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: HDFS-1312
• Component/s: datanode
• Hadoop Flags: Reviewed
• Assignee: Anu Engineer
• Reporter: Lei (Eddy) Xu
• Created: 17/Jun/16 01:12
• Updated: 24/Jun/16 06:19
• Resolved: 18/Jun/16 16:56

Description

When running the hdfs diskbalancer against a DN whose disk balancer feature is not enabled, it reports:

$ hdfs diskbalancer -plan 127.0.0.1 -uri hdfs://localhost
16/06/16 18:03:29 WARN util.NativeCodeLoader: Unable to load native-hadoop library for your platform... using builtin-java classes where applicable
Internal error, Unable to create JSON string.
	at org.apache.hadoop.hdfs.server.datanode.DiskBalancer.getVolumeNames(DiskBalancer.java:260)
	at org.apache.hadoop.hdfs.server.datanode.DataNode.getDiskBalancerSetting(DataNode.java:3105)
	at org.apache.hadoop.hdfs.protocolPB.ClientDatanodeProtocolServerSideTranslatorPB.getDiskBalancerSetting(ClientDatanodeProtocolServerSideTranslatorPB.java:359)
	at org.apache.hadoop.hdfs.protocol.proto.ClientDatanodeProtocolProtos$ClientDatanodeProtocolService$2.callBlockingMethod(ClientDatanodeProtocolProtos.java:17515)
	at org.apache.hadoop.ipc.ProtobufRpcEngine$Server$ProtoBufRpcInvoker.call(ProtobufRpcEngine.java:617)
	at org.apache.hadoop.ipc.RPC$Server.call(RPC.java:1073)
	at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:2086)
	at org.apache.hadoop.ipc.Server$Handler$1.run(Server.java:2082)
	at java.security.AccessController.doPrivileged(Native Method)
	at javax.security.auth.Subject.doAs(Subject.java:415)
	at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1693)
	at org.apache.hadoop.ipc.Server$Handler.run(Server.java:2080)
Caused by: org.apache.hadoop.hdfs.server.diskbalancer.DiskBalancerException: Disk Balancer is not enabled.
	at org.apache.hadoop.hdfs.server.datanode.DiskBalancer.checkDiskBalancerEnabled(DiskBalancer.java:293)
	at org.apache.hadoop.hdfs.server.datanode.DiskBalancer.getVolumeNames(DiskBalancer.java:251)
	... 11 more

We should not directly throw IOE to the user. And it should explicitly explain the reason that the operation fails.