[HDFS-15115] Namenode crash caused by NPE in BlockPlacementPolicyDefault when dynamically change logger to debug

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 3.3.0, 3.1.4, 3.2.2, 2.10.1
• Hadoop Flags: Reviewed
• Flags: Patch
• Assignee: wangzhixiang
• Reporter: wangzhixiang
• Created: 13/Jan/20 08:15
• Updated: 19/Feb/20 23:17
• Resolved: 08/Feb/20 05:43

Description

To get debug info, we dynamically change the logger of BlockPlacementPolicyDefault to debug when namenode is running. However, the Namenode crashs. From the log, we find some NPE in BlockPlacementPolicyDefault.chooseRandom. Because StringBuilder builder will be used 4 times in BlockPlacementPolicyDefault.chooseRandom method. While the builder only initializes in the first time of this method. If we change the logger of BlockPlacementPolicyDefault to debug after the part, the builder in remaining part is NULL and cause NPE

Issue Links

• relates to: HDFS-14103 Review Logging of BlockPlacementPolicyDefault