[MAPREDUCE-5288] ResourceEstimator#getEstimatedTotalMapOutputSize suffers from divide by zero issues

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.2.0
• Fix Version/s: 1.3.0
• Component/s: mrv1
• Hadoop Flags: Reviewed
• Assignee: Karthik Kambatla
• Reporter: Harsh J
• Created: 01/Jun/13 15:40
• Updated: 03/Nov/14 18:05
• Resolved: 24/Jul/13 22:26

Description

The computation in the above mentioned class-method is below:

      long estimate = Math.round(((double)inputSize * 
          completedMapsOutputSize * 2.0)/completedMapsInputSize);

Given http://docs.oracle.com/javase/6/docs/api/java/lang/Math.html#round(double), its possible that the returned estimate could be Long.MAX_VALUE if completedMapsInputSize is determined to be zero.

This can be proven with a simple code snippet:

class Foo {
    public static void main(String... args) {
        long inputSize = 600L + 2;
        long estimate = Math.round(((double)inputSize *
                              1L * 2.0)/0L);
        System.out.println(estimate);
    }
}

The above conveniently prints out: 9223372036854775807, which is Long.MAX_VALUE (or 8 Exbibytes per MapReduce).