Add Tracestate into SpanContext. (#1359)

* Add Tracestate into SpanContext.

* Remove empty constructor from Tracestate.Builder

* Add info in the changelog.

3 files changed, 13 insertions, 4 deletions

diff --git a/impl_core/src/main/java/io/opencensus/implcore/trace/SpanBuilderImpl.java b/impl_core/src/main/java/io/opencensus/implcore/trace/SpanBuilderImpl.java
index 3c5f20c6..d4f7c347 100644
--- a/impl_core/src/main/java/io/opencensus/implcore/trace/SpanBuilderImpl.java
+++ b/impl_core/src/main/java/io/opencensus/implcore/trace/SpanBuilderImpl.java
@@ -31,6 +31,7 @@ import io.opencensus.trace.SpanContext;
 import io.opencensus.trace.SpanId;
 import io.opencensus.trace.TraceId;
 import io.opencensus.trace.TraceOptions;
+import io.opencensus.trace.Tracestate;
 import io.opencensus.trace.config.TraceConfig;
 import io.opencensus.trace.config.TraceParams;
 import java.util.Collections;
@@ -41,8 +42,9 @@ import javax.annotation.Nullable;
 
 /** Implementation of the {@link SpanBuilder}. */
 final class SpanBuilderImpl extends SpanBuilder {
-  private final Options options;
+  private static final Tracestate TRACESTATE_DEFAULT = Tracestate.builder().build();
 
+  private final Options options;
   private final String name;
   @Nullable private final Span parent;
   @Nullable private final SpanContext remoteParentSpanContext;
@@ -66,6 +68,8 @@ final class SpanBuilderImpl extends SpanBuilder {
     SpanId spanId = SpanId.generateRandomId(random);
     SpanId parentSpanId = null;
     TraceOptions.Builder traceOptionsBuilder;
+    // TODO(bdrutu): Handle tracestate correctly not just propagate.
+    Tracestate tracestate = TRACESTATE_DEFAULT;
     if (parent == null || !parent.isValid()) {
       // New root span.
       traceId = TraceId.generateRandomId(random);
@@ -77,6 +81,7 @@ final class SpanBuilderImpl extends SpanBuilder {
       traceId = parent.getTraceId();
       parentSpanId = parent.getSpanId();
       traceOptionsBuilder = TraceOptions.builder(parent.getTraceOptions());
+      tracestate = parent.getTracestate();
     }
     traceOptionsBuilder.setIsSampled(
         makeSamplingDecision(
@@ -95,7 +100,7 @@ final class SpanBuilderImpl extends SpanBuilder {
     }
     SpanImpl span =
         SpanImpl.startSpan(
-            SpanContext.create(traceId, spanId, traceOptions),
+            SpanContext.create(traceId, spanId, traceOptions, tracestate),
             spanOptions,
             name,
             kind,
diff --git a/impl_core/src/main/java/io/opencensus/implcore/trace/propagation/B3Format.java b/impl_core/src/main/java/io/opencensus/implcore/trace/propagation/B3Format.java
index 67c66ea9..d928d93c 100644
--- a/impl_core/src/main/java/io/opencensus/implcore/trace/propagation/B3Format.java
+++ b/impl_core/src/main/java/io/opencensus/implcore/trace/propagation/B3Format.java
@@ -23,6 +23,7 @@ import io.opencensus.trace.SpanContext;
 import io.opencensus.trace.SpanId;
 import io.opencensus.trace.TraceId;
 import io.opencensus.trace.TraceOptions;
+import io.opencensus.trace.Tracestate;
 import io.opencensus.trace.propagation.SpanContextParseException;
 import io.opencensus.trace.propagation.TextFormat;
 import java.util.Arrays;
@@ -38,6 +39,7 @@ import org.checkerframework.checker.nullness.qual.NonNull;
  * href=https://github.com/openzipkin/b3-propagation>b3-propagation</a>.
  */
 final class B3Format extends TextFormat {
+  private static final Tracestate TRACESTATE_DEFAULT = Tracestate.builder().build();
   @VisibleForTesting static final String X_B3_TRACE_ID = "X-B3-TraceId";
   @VisibleForTesting static final String X_B3_SPAN_ID = "X-B3-SpanId";
   @VisibleForTesting static final String X_B3_PARENT_SPAN_ID = "X-B3-ParentSpanId";
@@ -103,7 +105,7 @@ final class B3Format extends TextFormat {
           || FLAGS_VALUE.equals(getter.get(carrier, X_B3_FLAGS))) {
         traceOptions = TraceOptions.builder().setIsSampled(true).build();
       }
-      return SpanContext.create(traceId, spanId, traceOptions);
+      return SpanContext.create(traceId, spanId, traceOptions, TRACESTATE_DEFAULT);
     } catch (IllegalArgumentException e) {
       throw new SpanContextParseException("Invalid input.", e);
     }
diff --git a/impl_core/src/main/java/io/opencensus/implcore/trace/propagation/BinaryFormatImpl.java b/impl_core/src/main/java/io/opencensus/implcore/trace/propagation/BinaryFormatImpl.java
index a2438008..1af24854 100644
--- a/impl_core/src/main/java/io/opencensus/implcore/trace/propagation/BinaryFormatImpl.java
+++ b/impl_core/src/main/java/io/opencensus/implcore/trace/propagation/BinaryFormatImpl.java
@@ -23,6 +23,7 @@ import io.opencensus.trace.SpanContext;
 import io.opencensus.trace.SpanId;
 import io.opencensus.trace.TraceId;
 import io.opencensus.trace.TraceOptions;
+import io.opencensus.trace.Tracestate;
 import io.opencensus.trace.propagation.BinaryFormat;
 import io.opencensus.trace.propagation.SpanContextParseException;
 
@@ -61,6 +62,7 @@ import io.opencensus.trace.propagation.SpanContextParseException;
  * </ul>
  */
 final class BinaryFormatImpl extends BinaryFormat {
+  private static final Tracestate TRACESTATE_DEFAULT = Tracestate.builder().build();
   private static final byte VERSION_ID = 0;
   private static final int VERSION_ID_OFFSET = 0;
   // The version_id/field_id size in bytes.
@@ -141,6 +143,6 @@ final class BinaryFormatImpl extends BinaryFormat {
       }
       traceOptions = TraceOptions.fromBytes(bytes, pos + ID_SIZE);
     }
-    return SpanContext.create(traceId, spanId, traceOptions);
+    return SpanContext.create(traceId, spanId, traceOptions, TRACESTATE_DEFAULT);
   }
 }