[HDFS-14072] DataNode runs async disk checks maybe throws NullPointerException, and DataNode failed to register to NameSpace.

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Duplicate
• Affects Version/s: 2.8.0, 3.0.0
• Component/s: hdfs
• Labels: HDFS HDFS-11114

Environment

hadoop-2.7.3, hadoop-2.8.0

• Target Version/s: 2.8.0
• Hadoop Flags: Reviewed

Release Note

 this.completedChecks = new ReferenceMap(1, 1);
or
 this.completedChecks = new HashMap<>();

• Tags: HDFS, DiskChecks
• Flags: Patch
• External issue URL: https://issues.apache.org/jira/browse/HDFS-11114
• External issue ID: HDFS-11114
• Assignee: Unassigned
• Reporter: guangyi lu
• Created: 13/Nov/18 12:34
• Updated: 14/Nov/18 22:43
• Resolved: 14/Nov/18 22:43

Description

In ThrottledAsyncChecker class，it members of the completedChecks is WeakHashMap, its definition is as follows：
     this.completedChecks = new WeakHashMap<>();

and one of its uses is as follows in schedule method:
    if (completedChecks.containsKey(target))

{         // here may be happen garbage collection，and result may be null.          final LastCheckResult<V> result = completedChecks.get(target);          final long msSinceLastCheck = timer.monotonicNow() - result.completedAt;     }

after  "completedChecks.containsKey(target)"，  may be happen garbage collection，  and result may be null.

 

Issue Links

• duplicates: HDFS-14074 DataNode runs async disk checks maybe throws NullPointerException, and DataNode failed to register to NameSpace.