Exporter/Zipkin: Add a note about status tags. (#1931)

* Exporter/Zipkin: Add a note about status tags.

* Set error tag when status is not OK.

Author: songy23

exporters/trace/zipkin/src/main/java/io/opencensus/exporter/trace/zipkin/ZipkinExporterHandler.java

@@ -19,6 +19,7 @@
 import static java.util.concurrent.TimeUnit.NANOSECONDS;
 import static java.util.concurrent.TimeUnit.SECONDS;
 
+import com.google.common.annotations.VisibleForTesting;
 import io.opencensus.common.Duration;
 import io.opencensus.common.Function;
 import io.opencensus.common.Functions;
@@ -53,8 +54,13 @@
 final class ZipkinExporterHandler extends TimeLimitedHandler {
   private static final Logger logger = Logger.getLogger(ZipkinExporterHandler.class.getName());
   private static final String EXPORT_SPAN_NAME = "SendZipkinSpans";
-  private static final String STATUS_CODE = "census.status_code";
-  private static final String STATUS_DESCRIPTION = "census.status_description";
+
+  // The naming follows Zipkin convention. As an example see:
+  // https://github.com/apache/incubator-zipkin-brave/blob/643b7245c462dc14d47afcdb076b2603fd421497/instrumentation/grpc/src/main/java/brave/grpc/GrpcParser.java#L67-L73
+  @VisibleForTesting static final String STATUS_CODE = "census.status_code";
+  @VisibleForTesting static final String STATUS_DESCRIPTION = "census.status_description";
+  @VisibleForTesting static final String STATUS_ERROR = "error";
+
   private final SpanBytesEncoder encoder;
   private final Sender sender;
   private final Endpoint localEndpoint;
@@ -130,6 +136,9 @@ static Span generateSpan(SpanData spanData, Endpoint localEndpoint) {
       if (status.getDescription() != null) {
         spanBuilder.putTag(STATUS_DESCRIPTION, status.getDescription());
       }
+      if (!status.isOk()) {
+        spanBuilder.putTag(STATUS_ERROR, status.getCanonicalCode().toString());
+      }
     }
 
     for (TimedEvent<Annotation> annotation : spanData.getAnnotations().getEvents()) {

exporters/trace/zipkin/src/test/java/io/opencensus/exporter/trace/zipkin/ZipkinExporterHandlerTest.java

@@ -102,7 +102,7 @@ public void generateSpan_NoKindAndRemoteParent() {
                 .localEndpoint(localEndpoint)
                 .addAnnotation(1505855799000000L + 433901068L / 1000, "RECEIVED")
                 .addAnnotation(1505855799000000L + 459486280L / 1000, "SENT")
-                .putTag("census.status_code", "OK")
+                .putTag(ZipkinExporterHandler.STATUS_CODE, "OK")
                 .build());
   }
 
@@ -143,7 +143,7 @@ public void generateSpan_ServerKind() {
                 .localEndpoint(localEndpoint)
                 .addAnnotation(1505855799000000L + 433901068L / 1000, "RECEIVED")
                 .addAnnotation(1505855799000000L + 459486280L / 1000, "SENT")
-                .putTag("census.status_code", "OK")
+                .putTag(ZipkinExporterHandler.STATUS_CODE, "OK")
                 .build());
   }
 
@@ -184,7 +184,7 @@ public void generateSpan_ClientKind() {
                 .localEndpoint(localEndpoint)
                 .addAnnotation(1505855799000000L + 433901068L / 1000, "RECEIVED")
                 .addAnnotation(1505855799000000L + 459486280L / 1000, "SENT")
-                .putTag("census.status_code", "OK")
+                .putTag(ZipkinExporterHandler.STATUS_CODE, "OK")
                 .build());
   }
 
@@ -229,10 +229,53 @@ public void generateSpan_WithAttributes() {
                 .localEndpoint(localEndpoint)
                 .addAnnotation(1505855799000000L + 433901068L / 1000, "RECEIVED")
                 .addAnnotation(1505855799000000L + 459486280L / 1000, "SENT")
-                .putTag("census.status_code", "OK")
+                .putTag(ZipkinExporterHandler.STATUS_CODE, "OK")
                 .putTag("string", "string value")
                 .putTag("boolean", "false")
                 .putTag("long", "9999")
                 .build());
   }
+
+  @Test
+  public void generateSpan_WithErrorStatus() {
+    String errorMessage = "timeout";
+    SpanData data =
+        SpanData.create(
+            SpanContext.create(
+                TraceId.fromLowerBase16(TRACE_ID),
+                SpanId.fromLowerBase16(SPAN_ID),
+                TraceOptions.builder().setIsSampled(true).build()),
+            SpanId.fromLowerBase16(PARENT_SPAN_ID),
+            true, /* hasRemoteParent */
+            "Recv.helloworld.Greeter.SayHello", /* name */
+            Kind.SERVER, /* kind */
+            Timestamp.create(1505855794, 194009601) /* startTimestamp */,
+            Attributes.create(attributes, 0 /* droppedAttributesCount */),
+            TimedEvents.create(annotations, 0 /* droppedEventsCount */),
+            TimedEvents.create(messageEvents, 0 /* droppedEventsCount */),
+            Links.create(Collections.<Link>emptyList(), 0 /* droppedLinksCount */),
+            null, /* childSpanCount */
+            Status.DEADLINE_EXCEEDED.withDescription(errorMessage),
+            Timestamp.create(1505855799, 465726528) /* endTimestamp */);
+
+    assertThat(ZipkinExporterHandler.generateSpan(data, localEndpoint))
+        .isEqualTo(
+            Span.newBuilder()
+                .traceId(TRACE_ID)
+                .parentId(PARENT_SPAN_ID)
+                .id(SPAN_ID)
+                .kind(Span.Kind.SERVER)
+                .name(data.getName())
+                .timestamp(1505855794000000L + 194009601L / 1000)
+                .duration(
+                    (1505855799000000L + 465726528L / 1000)
+                        - (1505855794000000L + 194009601L / 1000))
+                .localEndpoint(localEndpoint)
+                .addAnnotation(1505855799000000L + 433901068L / 1000, "RECEIVED")
+                .addAnnotation(1505855799000000L + 459486280L / 1000, "SENT")
+                .putTag(ZipkinExporterHandler.STATUS_CODE, "DEADLINE_EXCEEDED")
+                .putTag(ZipkinExporterHandler.STATUS_DESCRIPTION, errorMessage)
+                .putTag(ZipkinExporterHandler.STATUS_ERROR, "DEADLINE_EXCEEDED")
+                .build());
+  }
 }