[HDFS-8992] Balancer throws NPE

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Duplicate
• Affects Version/s: 2.4.1
• Component/s: balancer & mover
• Assignee: Unassigned
• Reporter: Xiaoqiao He
• Created: 29/Aug/15 08:11
• Updated: 29/Aug/15 09:04
• Resolved: 29/Aug/15 09:01

Description

Balancer may throw NPE because the following if Statements at line 709 of Balancer.java

          synchronized (block) {
            // update locations
            for (String datanodeUuid : blk.getDatanodeUuids()) {
              final BalancerDatanode d = datanodeMap.get(datanodeUuid);
              if (datanode != null) { // not an unknown datanode
                block.addLocation(d);
              }
            }
          }

Before moving block, Balancer divides into two step to get all DNs info & some blocks of DN from NN. Regarding one DN commission after getDatanodeReport then getBlockList and one block's target is above DN just right, It will throw NPE when dispatcher.

Issue Links

• duplicates: HDFS-8993 Balancer throws NPE
• is duplicated by: HDFS-6364 Incorrect check for unknown datanode in Balancer