[jira] [Created] (HDFS-16029) Divide by zero bug in InstrumentationService.java

["Yiyuan GUO (Jira)" <ji...@apache.org>]

Yiyuan GUO created HDFS-16029:
---------------------------------

             Summary: Divide by zero bug in InstrumentationService.java
                 Key: HDFS-16029
                 URL: https://issues.apache.org/jira/browse/HDFS-16029
             Project: Hadoop HDFS
          Issue Type: Bug
          Components: security
            Reporter: Yiyuan GUO


In the file _lib/service/instrumentation/InstrumentationService.java,_ the method 
_Timer.getValues_ has the following [code|https://github.com/apache/hadoop/blob/trunk/hadoop-hdfs-project/hadoop-hdfs-httpfs/src/main/java/org/apache/hadoop/lib/service/instrumentation/InstrumentationService.java#L236]:
{code:java}
long[] getValues() {
    ......
    int limit = (full) ? size : (last + 1);
    ......
    values[AVG_TOTAL] = values[AVG_TOTAL] / limit;
}
{code}
The variable _limit_ is used as a divisor. However, its value may be equal to _last + 1,_ which can be zero since _last_ is __ initialized to -1 in the [constructor|https://github.com/apache/hadoop/blob/trunk/hadoop-hdfs-project/hadoop-hdfs-httpfs/src/main/java/org/apache/hadoop/lib/service/instrumentation/InstrumentationService.java#L222]:
{code:java}
public Timer(int size) {
    ...
    last = -1;
}
{code}
Thus, a divide by zero problem can happen
 



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