Suhan Mao created HDFS-12416:
--------------------------------
Summary: BlockPlacementPolicyDefault will cause NN shutdown if log
level is changed
Key: HDFS-12416
URL: https://issues.apache.org/jira/browse/HDFS-12416
Project: Hadoop HDFS
Issue Type: Bug
Components: block placement
Affects Versions: 3.0.0-alpha3, 2.7.4
Reporter: Suhan Mao
In BlockPlacementPolicyDefault.chooseRandom method.
The code are in below structure:
{code:java}
StringBuilder builder = null;
if (LOG.isDebugEnabled()) {
builder = debugLoggingBuilder.get();
builder.setLength(0);
builder.append("[");
}
while(numOfReplicas > 0){
chooseDataNode(scope, excludedNodes)
if (LOG.isDebugEnabled()) {
builder.append("\nNode ").append(NodeBase.getPath(chosenNode))
.append(" [");
}
}
{code}
There's a possibility that the loglevel is INFO before entering while loop, but
the loglevel is changed to DEBUG inside the loop through web UI.
In that case, builder is not initialized in the beginning and
NullPointerException will throw and this will cause NN exiting.
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