[HBASE-26550] Make sure the master is running normally before accepting a balance command

• Type: Bug
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 2.5.0, 3.0.0-alpha-2
• Component/s: Balancer, master
• Hadoop Flags: Reviewed
• Assignee: Josh Elser
• Reporter: Josh Elser
• Created: 09/Dec/21 00:22
• Updated: 19/Dec/21 06:20
• Resolved: 14/Dec/21 15:35

Description

Noticed this in a unit test from https://github.com/apache/hbase/pull/3851

I believe this is a result of the new balance() implementation in the Master, and a client submitting a request to the master before it's completed its instantiation. Simple fix to avoid the NPE.

Failed after attempts=2, exceptions:
2021-12-07T18:14:19.203Z, java.io.IOException: java.io.IOException
	at org.apache.hadoop.hbase.ipc.RpcServer.call(RpcServer.java:461)
	at org.apache.hadoop.hbase.ipc.CallRunner.run(CallRunner.java:138)
	at org.apache.hadoop.hbase.ipc.RpcExecutor$Handler.run(RpcExecutor.java:354)
	at org.apache.hadoop.hbase.ipc.RpcExecutor$Handler.run(RpcExecutor.java:334)
Caused by: java.lang.NullPointerException
	at org.apache.hadoop.hbase.master.HMaster.getProcedures(HMaster.java:3335)
	at org.apache.hadoop.hbase.master.ServerManager.areDeadServersInProgress(ServerManager.java:505)
	at org.apache.hadoop.hbase.master.HMaster.balance(HMaster.java:1886)
	at org.apache.hadoop.hbase.master.MasterRpcServices.balance(MasterRpcServices.java:740)
	at org.apache.hadoop.hbase.shaded.protobuf.generated.MasterProtos$MasterService$2.callBlockingMethod(MasterProtos.java)
	at org.apache.hadoop.hbase.ipc.RpcServer.call(RpcServer.java:393)
	... 3 more 

Issue Links

• links to: GitHub Pull Request #3928