ConfX created HDFS-17107:
----------------------------
Summary: Null Pointer Exception after turned on detail metric for
namenode lock
Key: HDFS-17107
URL: https://issues.apache.org/jira/browse/HDFS-17107
Project: Hadoop HDFS
Issue Type: Bug
Reporter: ConfX
Attachments: reproduce.sh
h2. What happened
After setting {{{}dfs.namenode.lock.detailed-metrics.enabled=true{}}}, running
test
{{org.apache.hadoop.hdfs.server.namenode.TestFSNamesystemLock#testFSWriteLockReportSuppressed}}
results in a {{{}NullPointerException{}}}.
h2. Where's the bug
In class {{{}FSNameSystemLock{}}}:
{noformat}
if (metricsEnabled) {
String opMetric = getMetricName(operationName, isWrite);
detailedHoldTimeMetrics.add(opMetric, value);{noformat}
here it may be that the metric is enabled but the detailedHoldTimeMetrics is
null.
h2. How to reproduce
# Set {{dfs.namenode.lock.detailed-metrics.enabled=true}}
# Run
{{org.apache.hadoop.hdfs.server.namenode.TestFSNamesystemLock#testFSWriteLockReportSuppressed}}
and the following exception should be observed:
{noformat}
java.lang.NullPointerException
at
org.apache.hadoop.hdfs.server.namenode.FSNamesystemLock.addMetric(FSNamesystemLock.java:359)
at
org.apache.hadoop.hdfs.server.namenode.FSNamesystemLock.writeUnlock(FSNamesystemLock.java:287)
at
org.apache.hadoop.hdfs.server.namenode.FSNamesystemLock.writeUnlock(FSNamesystemLock.java:236)
at
org.apache.hadoop.hdfs.server.namenode.TestFSNamesystemLock.testFSWriteLockReportSuppressed(TestFSNamesystemLock.java:433){noformat}
For an easy reproduction, run the reproduce.sh in the attachment.
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