[NO ISSUE][RT] Allow getting the value of a span duration

- user model changes: no
- storage format changes: no
- interface changes: no

Details:
- Enable getting the duration for spans. This is useful for
  delay calculations.

Change-Id: Icce0ac0a0d47a26655bf640f3f1a92506d87c30e
Reviewed-on: https://asterix-gerrit.ics.uci.edu/2940
Sonar-Qube: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Tested-by: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Integration-Tests: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Reviewed-by: Till Westmann <tillw@apache.org>
diff --git a/hyracks-fullstack/hyracks/hyracks-util/src/main/java/org/apache/hyracks/util/Span.java b/hyracks-fullstack/hyracks/hyracks-util/src/main/java/org/apache/hyracks/util/Span.java
index e75a961..183cb6f 100644
--- a/hyracks-fullstack/hyracks/hyracks-util/src/main/java/org/apache/hyracks/util/Span.java
+++ b/hyracks-fullstack/hyracks/hyracks-util/src/main/java/org/apache/hyracks/util/Span.java
@@ -29,6 +29,10 @@
         spanNanos = unit.toNanos(span);
     }
 
+    public long getSpanNanos() {
+        return spanNanos;
+    }
+
     public static Span start(long span, TimeUnit unit) {
         return new Span(span, unit);
     }