Add a boolean field to set a Span as asynchronous.

api/src/main/java/openconsensus/trace/NoopTrace.java

@@ -152,6 +152,11 @@ public SpanBuilder setSpanKind(Span.Kind spanKind) {
       return this;
     }
 
+    @Override
+    public SpanBuilder setIsAsynchronous(boolean isAsynchronous) {
+      return this;
+    }
+
     private NoopSpanBuilder(String name) {
       Utils.checkNotNull(name, "name");
     }

api/src/main/java/openconsensus/trace/SpanBuilder.java

@@ -165,6 +165,18 @@ public abstract class SpanBuilder {
    */
   public abstract SpanBuilder setSpanKind(Span.Kind spanKind);
 
+  /**
+   * Sets this {@code Span} as asynchronous. The default value is {@code false}.
+   *
+   * <p>A {@code Span} is considered asynchronous if its parent {@code Span} does not depend in any
+   * way on its result, hence having independent lifetime.
+   *
+   * @param isAsynchronous new value determining if this {@code Span} is asynchronous.
+   * @return this.
+   * @since 0.1.0
+   */
+  public abstract SpanBuilder setIsAsynchronous(boolean isAsynchronous);
+
   /**
    * Starts a new {@link Span}.
    *

api/src/main/java/openconsensus/trace/data/SpanData.java

@@ -72,6 +72,7 @@ public static SpanData create(
       Map<String, AttributeValue> attributes,
       List<TimedEvent> timedEvents,
       List<Link> links,
+      boolean isAsynchronous,
       @Nullable Integer childSpanCount,
       Status status,
       Timestamp endTimestamp) {
@@ -85,6 +86,7 @@ public static SpanData create(
         Collections.unmodifiableList(
             new ArrayList<>(Utils.checkNotNull(timedEvents, "timedEvents"))),
         Collections.unmodifiableList(new ArrayList<>(Utils.checkNotNull(links, "links"))),
+        isAsynchronous,
         childSpanCount,
         status,
         endTimestamp);
@@ -155,6 +157,13 @@ public static SpanData create(
    */
   public abstract List<Link> getLinks();
 
+  /**
+   * Returns true if this {@code Span} represents an asynchronous operation.
+   *
+   * @return true if this {@code Span} represent an asynchronous operation.
+   */
+  public abstract boolean getIsAsynchronous();
+
   /**
    * Returns the number of child spans that were generated while the {@code Span} was running. If
    * not {@code null} allows service implementations to detect missing child spans.