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https://issues.apache.org/jira/browse/HDFS-16704?focusedWorklogId=797095&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-797095
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ASF GitHub Bot logged work on HDFS-16704:
-----------------------------------------
Author: ASF GitHub Bot
Created on: 02/Aug/22 02:31
Start Date: 02/Aug/22 02:31
Worklog Time Spent: 10m
Work Description: ZanderXu commented on PR #4661:
URL: https://github.com/apache/hadoop/pull/4661#issuecomment-1201945547
@ayushtkn Thank you very much for helping me review it.
Yes, you are right, we should return an empty value for this case. How about
change it same with `getDiskBalancerStatus`, such as:
```
@Override // DataNodeMXBean
public String getVolumeInfo() {
if (data == null) {
LOG.debug("Storage not yet initialized.");
return ""; // it's different with JSON.toString(new HashMap<String,
Object>())
}
return JSON.toString(data.getVolumeInfoMap());
}
```
Developers or SREs are very sensitive to NPE, so I feel we shouldn't out put
it in this expected situation.
> Extra Stuff: This log line just below is wrong, incorrect placeholder, can
fix in a separate jira if interested. :-)
Copy, sir. I will fix it in a separate Jira.
Issue Time Tracking
-------------------
Worklog Id: (was: 797095)
Time Spent: 0.5h (was: 20m)
> Datanode return empty response instead of NPE for GetVolumeInfo during
> restarting
> ---------------------------------------------------------------------------------
>
> Key: HDFS-16704
> URL: https://issues.apache.org/jira/browse/HDFS-16704
> Project: Hadoop HDFS
> Issue Type: Improvement
> Reporter: ZanderXu
> Assignee: ZanderXu
> Priority: Major
> Labels: pull-request-available
> Time Spent: 0.5h
> Remaining Estimate: 0h
>
> During datanode starting, I found some NPE in logs:
> {code:java}
> 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)
> {code}
> Because the storage of datanode not yet initialized when we trying to get
> metrics of datanode, and related code as below:
> {code:java}
> @Override // DataNodeMXBean
> public String getVolumeInfo() {
> Preconditions.checkNotNull(data, "Storage not yet initialized");
> return JSON.toString(data.getVolumeInfoMap());
> } {code}
> 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.
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