[HBASE-14291] NPE On StochasticLoadBalancer Balance Involving RS With No Regions

• Type: Bug
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 2.0.0
• Fix Version/s: 1.2.0, 1.3.0, 2.0.0
• Component/s: Balancer

Environment

Pseudo-distributed (2 local RegionServers), Hadoop 2.5.1, Java 1.7.0_71

• Hadoop Flags: Reviewed
• Assignee: Ted Yu
• Reporter: Matt Warhaftig
• Created: 22/Aug/15 04:28
• Updated: 01/Jul/22 21:07
• Resolved: 23/Aug/15 01:33

Description

When StochasticLoadBalancer attempts to balance a local RS with multiple regions with another local RS that had no regions the HBase shell call of 'balancer' gets the following NPE:

ERROR: java.io.IOException
	at org.apache.hadoop.hbase.ipc.RpcServer.call(RpcServer.java:2175)
	at org.apache.hadoop.hbase.ipc.CallRunner.run(CallRunner.java:106)
	at org.apache.hadoop.hbase.ipc.RpcExecutor.consumerLoop(RpcExecutor.java:130)
	at org.apache.hadoop.hbase.ipc.RpcExecutor$1.run(RpcExecutor.java:107)
	at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.NullPointerException
	at org.apache.hadoop.hbase.master.balancer.BaseLoadBalancer$Cluster.getLeastLoadedTopServerForRegion(BaseLoadBalancer.java:863)
	at org.apache.hadoop.hbase.master.balancer.StochasticLoadBalancer$LocalityBasedCandidateGenerator.generate(StochasticLoadBalancer.java:724)
	at org.apache.hadoop.hbase.master.balancer.StochasticLoadBalancer.balanceCluster(StochasticLoadBalancer.java:325)
	at org.apache.hadoop.hbase.master.balancer.StochasticLoadBalancer.balanceCluster(StochasticLoadBalancer.java:263)
	at org.apache.hadoop.hbase.master.HMaster.balance(HMaster.java:1264)
	at org.apache.hadoop.hbase.master.MasterRpcServices.balance(MasterRpcServices.java:413)
	at org.apache.hadoop.hbase.protobuf.generated.MasterProtos$MasterService$2.callBlockingMethod(MasterProtos.java:52450)
	at org.apache.hadoop.hbase.ipc.RpcServer.call(RpcServer.java:2133)
	... 4 more

Issue only occurs when one of the RSs has no regions before balancing. Also, unsure if distributed RSs would also have same issue. Attached 'hbase-mwarhaftig-master-Matts-MBP.log' is master's log of the error occurring.

SimpleLoadBalancer rebalances correctly when used in the same situation.

Issue Links

• duplicates: HBASE-14653 Balancer is getting NullPointerExceptions