[HDFS-16704] Datanode return empty response instead of NPE for GetVolumeInfo during restarting

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 3.4.0
• Fix Version/s: 3.4.0
• Component/s: datanode
• Labels: pull-request-available
• Target Version/s: 3.4.0
• Hadoop Flags: Reviewed
• Assignee: ZanderXu
• Reporter: ZanderXu
• Created: 30/Jul/22 03:37
• Updated: 28/Jan/24 08:20
• Resolved: 15/Aug/22 12:58

Description

During datanode starting, I found some NPE in logs:

Caused by: java.lang.NullPointerException: Storage not yet initialized
    at org.apache.hadoop.thirdparty.com.google.common.base.Preconditions.checkNotNull(Preconditions.java:899)
    at org.apache.hadoop.hdfs.server.datanode.DataNode.getVolumeInfo(DataNode.java:3533)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at sun.reflect.misc.Trampoline.invoke(MethodUtil.java:72)
    at sun.reflect.GeneratedMethodAccessor7.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at sun.reflect.misc.MethodUtil.invoke(MethodUtil.java:276)
    at com.sun.jmx.mbeanserver.ConvertingMethod.invokeWithOpenReturn(ConvertingMethod.java:193)
    at com.sun.jmx.mbeanserver.ConvertingMethod.invokeWithOpenReturn(ConvertingMethod.java:175) 

Because the storage of datanode not yet initialized when we trying to get metrics of datanode, and related code as below:

@Override // DataNodeMXBean
public String getVolumeInfo() {
  Preconditions.checkNotNull(data, "Storage not yet initialized");
  return JSON.toString(data.getVolumeInfoMap());
} 

The logic is ok, but I feel that the more reasonable logic should be return an empty response instead of NPE, because InfoServer will be started before initBlockPool.

Issue Links

• links to: GitHub Pull Request #4661