ConfX created HDFS-17876:
----------------------------
Summary: NameNode.stop() missing null check for tracer.close() can
cause NPE during shutdown
Key: HDFS-17876
URL: https://issues.apache.org/jira/browse/HDFS-17876
Project: Hadoop HDFS
Issue Type: Bug
Components: namenode
Affects Versions: 3.3.6, 3.3.5
Reporter: ConfX
The NameNode.stop() method acks a null check for the tracer field before
calling tracer.close().
This is inconsistent with how all other resources are handled in the same
method and can lead to a NPE during shutdown if the NameNode is stopped before
fully initializing.
{code:java}
public void stop() {
synchronized(this) {
if (stopRequested)
return;
stopRequested = true;
}
try {
if (state != null) { // NULL CHECK
state.exitState(haContext);
}
} catch (ServiceFailedException e) {
LOG.warn("Encountered exception while exiting state", e);
} finally {
stopMetricsLogger();
stopCommonServices();
if (metrics != null) { // NULL CHECK
metrics.shutdown();
}
if (namesystem != null) { // NULL CHECK
namesystem.shutdown();
}
if (nameNodeStatusBeanName != null) { // NULL CHECK
MBeans.unregister(nameNodeStatusBeanName);
nameNodeStatusBeanName = null;
}
if (levelDBAliasMapServer != null) { // NULL CHECK
levelDBAliasMapServer.close();
}
}
tracer.close(); // NO NULL CHECK
} {code}
How tracer Can Be Null
1. Exception in parent constructor: If super(conf) at line 1007 throws before
tracer is initialized at line 1008, tracer remains null.
2. Early shutdown during initialization: The stopAtException() method (line
1048) calls this.stop() when exceptions occur during initialization. If
initialization fails early, tracer may not be set.
3. Subclass or future refactoring: A subclass could override initialization
behavior or future code changes could introduce paths where tracer isn't
initialized before stop() is called.
{code:java}
java.lang.NullPointerException
at
org.apache.hadoop.hdfs.server.namenode.NameNode.stop(NameNode.java:1116)
at
org.apache.hadoop.hdfs.server.namenode.NameNode.stopAtException(NameNode.java:1050)
at
org.apache.hadoop.hdfs.server.namenode.NameNode.(NameNode.java:1036){code}
Proposed Fix
Add a null check for tracer consistent with the other resources in the method:
{code:java}
if (tracer != null) {
tracer.close();
} {code}
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