Fix issue with saving tags when not propagating trace.

Previously, when setting headers as tags, the tags would only be saved if the request was propagated from another trace.

dd-trace-ot/src/main/java/datadog/opentracing/DDTracer.java

@@ -5,6 +5,7 @@ import datadog.opentracing.decorators.DDDecoratorsFactory;
 import datadog.opentracing.propagation.Codec;
 import datadog.opentracing.propagation.ExtractedContext;
 import datadog.opentracing.propagation.HTTPCodec;
+import datadog.opentracing.propagation.TagContext;
 import datadog.opentracing.scopemanager.ContextualScopeManager;
 import datadog.opentracing.scopemanager.ScopeContext;
 import datadog.trace.api.Config;
@@ -545,25 +546,36 @@ public class DDTracer implements io.opentracing.Tracer, Closeable, datadog.trace
           spanType = ddsc.getSpanType();
         }
 
-        // Propagate external trace
-      } else if (parentContext instanceof ExtractedContext) {
-        final ExtractedContext ddsc = (ExtractedContext) parentContext;
-        traceId = ddsc.getTraceId();
-        parentSpanId = ddsc.getSpanId();
-        baggage = ddsc.getBaggage();
-        tags.putAll(ddsc.getTags());
-        tags.put(Config.RUNTIME_ID_TAG, runtimeId);
-        parentTrace = new PendingTrace(DDTracer.this, traceId, serviceNameMappings);
-        samplingPriority = ddsc.getSamplingPriority();
-
-        // Start a new trace
       } else {
+        if (parentContext instanceof ExtractedContext) {
+          // Propagate external trace
+          final ExtractedContext extractedContext = (ExtractedContext) parentContext;
+          traceId = extractedContext.getTraceId();
+          parentSpanId = extractedContext.getSpanId();
+          samplingPriority = extractedContext.getSamplingPriority();
+          baggage = extractedContext.getBaggage();
+        } else {
+          // Start a new trace
           traceId = generateNewId();
           parentSpanId = "0";
-        baggage = null;
-        tags.put(Config.RUNTIME_ID_TAG, runtimeId);
-        parentTrace = new PendingTrace(DDTracer.this, traceId, serviceNameMappings);
           samplingPriority = PrioritySampling.UNSET;
+          baggage = null;
+        }
+
+        // Get header tags whether propagating or not.
+        if (parentContext instanceof TagContext) {
+          final TagContext tagContext = (TagContext) parentContext;
+
+          if (tags.isEmpty() && !tagContext.getTags().isEmpty()) {
+            tags = new HashMap<>();
+          }
+          if (!tagContext.getTags().isEmpty()) {
+            tags.putAll(tagContext.getTags());
+          }
+        }
+        tags.put(Config.RUNTIME_ID_TAG, runtimeId);
+
+        parentTrace = new PendingTrace(DDTracer.this, traceId, serviceNameMappings);
       }
 
       if (serviceName == null) {

dd-trace-ot/src/main/java/datadog/opentracing/propagation/Codec.java

@@ -22,6 +22,7 @@
 package datadog.opentracing.propagation;
 
 import datadog.opentracing.DDSpanContext;
+import io.opentracing.SpanContext;
 
 /** A codec is a simple object that can encode and decode a span context through a carrier */
 public interface Codec<T> {
@@ -41,5 +42,5 @@ public interface Codec<T> {
    * @param carrier
    * @return the span context
    */
-  ExtractedContext extract(T carrier);
+  SpanContext extract(T carrier);
 }

dd-trace-ot/src/main/java/datadog/opentracing/propagation/ExtractedContext.java

@@ -1,15 +1,13 @@
 package datadog.opentracing.propagation;
 
-import io.opentracing.SpanContext;
 import java.util.Map;
 import java.util.concurrent.atomic.AtomicBoolean;
 
-public class ExtractedContext implements SpanContext {
+public class ExtractedContext extends TagContext {
   private final String traceId;
   private final String spanId;
   private final int samplingPriority;
   private final Map<String, String> baggage;
-  private final Map<String, String> tags;
   private final AtomicBoolean samplingPriorityLocked = new AtomicBoolean(false);
 
   public ExtractedContext(
@@ -18,11 +16,11 @@ public class ExtractedContext implements SpanContext {
       final int samplingPriority,
       final Map<String, String> baggage,
       final Map<String, String> tags) {
+    super(tags);
     this.traceId = traceId;
     this.spanId = spanId;
     this.samplingPriority = samplingPriority;
     this.baggage = baggage;
-    this.tags = tags;
   }
 
   @Override
@@ -50,10 +48,6 @@ public class ExtractedContext implements SpanContext {
     return baggage;
   }
 
-  public Map<String, String> getTags() {
-    return tags;
-  }
-
   public boolean getSamplingPriorityLocked() {
     return samplingPriorityLocked.get();
   }

dd-trace-ot/src/main/java/datadog/opentracing/propagation/HTTPCodec.java

@@ -2,6 +2,7 @@ package datadog.opentracing.propagation;
 
 import datadog.opentracing.DDSpanContext;
 import datadog.trace.api.sampling.PrioritySampling;
+import io.opentracing.SpanContext;
 import io.opentracing.propagation.TextMap;
 import java.io.UnsupportedEncodingException;
 import java.math.BigInteger;
@@ -49,7 +50,7 @@ public class HTTPCodec implements Codec<TextMap> {
   }
 
   @Override
-  public ExtractedContext extract(final TextMap carrier) {
+  public SpanContext extract(final TextMap carrier) {
 
     Map<String, String> baggage = Collections.emptyMap();
     Map<String, String> tags = Collections.emptyMap();
@@ -81,12 +82,17 @@ public class HTTPCodec implements Codec<TextMap> {
         tags.put(taggedHeaders.get(key), decode(val));
       }
     }
-    ExtractedContext context = null;
-    if (!"0".equals(traceId)) {
-      context = new ExtractedContext(traceId, spanId, samplingPriority, baggage, tags);
-      context.lockSamplingPriority();
 
-      log.debug("{} - Parent context extracted", context.getTraceId());
+    SpanContext context = null;
+    if (!"0".equals(traceId)) {
+      final ExtractedContext ctx =
+          new ExtractedContext(traceId, spanId, samplingPriority, baggage, tags);
+      ctx.lockSamplingPriority();
+
+      log.debug("{} - Parent context extracted", ctx.getTraceId());
+      context = ctx;
+    } else if (!tags.isEmpty()) {
+      context = new TagContext(tags);
     }
 
     return context;

dd-trace-ot/src/main/java/datadog/opentracing/propagation/TagContext.java

@@ -0,0 +1,22 @@
+package datadog.opentracing.propagation;
+
+import io.opentracing.SpanContext;
+import java.util.Collections;
+import java.util.Map;
+
+public class TagContext implements SpanContext {
+  private final Map<String, String> tags;
+
+  public TagContext(final Map<String, String> tags) {
+    this.tags = tags;
+  }
+
+  public Map<String, String> getTags() {
+    return tags;
+  }
+
+  @Override
+  public Iterable<Map.Entry<String, String>> baggageItems() {
+    return Collections.emptyList();
+  }
+}

dd-trace-ot/src/test/groovy/datadog/opentracing/propagation/HTTPCodecTest.groovy

@@ -186,6 +186,24 @@ class HTTPCodecTest extends Specification {
     PrioritySampling.SAMPLER_KEEP | _
   }
 
+  def "extract header tags with no propagation"() {
+    setup:
+    final Map<String, String> actual = [
+      SOME_HEADER: "my-interesting-info",
+    ]
+
+    TagContext context = codec.extract(new TextMapExtractAdapter(actual))
+
+    expect:
+    !(context instanceof ExtractedContext)
+    context.getTags() == ["some-tag": "my-interesting-info"]
+  }
+
+  def "extract empty headers returns null"() {
+    expect:
+    codec.extract(new TextMapExtractAdapter(["ignored-header": "ignored-value"])) == null
+  }
+
   def "extract http headers with larger than Java long IDs"() {
     setup:
     String largeTraceId = "9523372036854775807"