Implement the text format so that w3c trace context headers are propagated.

sdk/src/main/java/io/opentelemetry/sdk/distributedcontext/DistributedContextHttpTextFormat.java

@@ -0,0 +1,69 @@
+/*
+ * Copyright 2019, OpenTelemetry Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.opentelemetry.sdk.distributedcontext;
+
+import io.opentelemetry.context.propagation.HttpTextFormat;
+import io.opentelemetry.distributedcontext.DistributedContext;
+import io.opentelemetry.distributedcontext.Entry;
+import io.opentelemetry.distributedcontext.EntryKey;
+import io.opentelemetry.distributedcontext.EntryValue;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+
+/** W3C Trace Context implementation of the HttpTextFormat for a DistributedContext. */
+class DistributedContextHttpTextFormat implements HttpTextFormat<DistributedContext> {
+  static final String TRACEPARENT = "traceparent";
+  static final String TRACESTATE = "tracestate";
+  private static final List<String> FIELDS =
+      Collections.unmodifiableList(Arrays.asList(TRACEPARENT, TRACESTATE));
+
+  private static final DistributedContextHttpTextFormat INSTANCE =
+      new DistributedContextHttpTextFormat();
+
+  public static DistributedContextHttpTextFormat getInstance() {
+    return INSTANCE;
+  }
+
+  @Override
+  public List<String> fields() {
+    return FIELDS;
+  }
+
+  @Override
+  public <C> void inject(DistributedContext value, C carrier, Setter<C> setter) {
+    for (String field : fields()) {
+      final EntryValue entryValue = value.getEntryValue(EntryKey.create(field));
+      if (entryValue != null) {
+        setter.put(carrier, field, entryValue.asString());
+      }
+    }
+  }
+
+  @Override
+  public <C> DistributedContext extract(C carrier, Getter<C> getter) {
+    final DistributedContextSdk.Builder builder = new DistributedContextSdk.Builder();
+    for (String field : fields()) {
+      final String value = getter.get(carrier, field);
+      if (value != null) {
+        builder.put(
+            EntryKey.create(field), EntryValue.create(value), Entry.METADATA_UNLIMITED_PROPAGATION);
+      }
+    }
+    return builder.build();
+  }
+}

sdk/src/main/java/io/opentelemetry/sdk/distributedcontext/DistributedContextManagerSdk.java

@@ -50,6 +50,6 @@ public BinaryFormat<DistributedContext> getBinaryFormat() {
 
   @Override
   public HttpTextFormat<DistributedContext> getHttpTextFormat() {
-    throw new UnsupportedOperationException("to be implemented");
+    return DistributedContextHttpTextFormat.getInstance();
   }
 }

sdk/src/test/java/io/opentelemetry/sdk/distributedcontext/DistributedContextHttpTextFormatTest.java

@@ -0,0 +1,145 @@
+/*
+ * Copyright 2019, OpenTelemetry Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.opentelemetry.sdk.distributedcontext;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+import io.opentelemetry.context.propagation.HttpTextFormat;
+import io.opentelemetry.distributedcontext.DistributedContext;
+import io.opentelemetry.distributedcontext.Entry;
+import io.opentelemetry.distributedcontext.EntryKey;
+import io.opentelemetry.distributedcontext.EntryValue;
+import java.util.HashMap;
+import java.util.Map;
+import javax.annotation.Nullable;
+import org.junit.Test;
+
+public class DistributedContextHttpTextFormatTest {
+
+  @Test
+  public void inject() {
+    DistributedContextHttpTextFormat httpTextFormat =
+        DistributedContextHttpTextFormat.getInstance();
+
+    Map<String, String> dataCarrier = new HashMap<>();
+    DistributedContext distributedContext =
+        new DistributedContextSdk.Builder()
+            .put(
+                EntryKey.create("foo"),
+                EntryValue.create("bar"),
+                Entry.METADATA_UNLIMITED_PROPAGATION)
+            .put(
+                EntryKey.create(DistributedContextHttpTextFormat.TRACEPARENT),
+                EntryValue.create("traceParentData"),
+                Entry.METADATA_UNLIMITED_PROPAGATION)
+            .put(
+                EntryKey.create(DistributedContextHttpTextFormat.TRACESTATE),
+                EntryValue.create("traceStateData"),
+                Entry.METADATA_UNLIMITED_PROPAGATION)
+            .build();
+
+    httpTextFormat.inject(
+        distributedContext,
+        dataCarrier,
+        new HttpTextFormat.Setter<Map<String, String>>() {
+          @Override
+          public void put(Map<String, String> carrier, String key, String value) {
+            carrier.put(key, value);
+          }
+        });
+
+    assertEquals(2, dataCarrier.size());
+    assertEquals("traceParentData", dataCarrier.get(DistributedContextHttpTextFormat.TRACEPARENT));
+    assertEquals("traceStateData", dataCarrier.get(DistributedContextHttpTextFormat.TRACESTATE));
+  }
+
+  @Test
+  public void inject_nullValues() {
+    DistributedContextHttpTextFormat httpTextFormat =
+        DistributedContextHttpTextFormat.getInstance();
+
+    Map<String, String> dataCarrier = new HashMap<>();
+    DistributedContext distributedContext =
+        new DistributedContextSdk.Builder()
+            .put(
+                EntryKey.create("foo"),
+                EntryValue.create("bar"),
+                Entry.METADATA_UNLIMITED_PROPAGATION)
+            .build();
+
+    httpTextFormat.inject(
+        distributedContext,
+        dataCarrier,
+        new HttpTextFormat.Setter<Map<String, String>>() {
+          @Override
+          public void put(Map<String, String> carrier, String key, String value) {
+            carrier.put(key, value);
+          }
+        });
+
+    assertTrue(dataCarrier.isEmpty());
+  }
+
+  @Test
+  public void extract() throws Exception {
+    DistributedContextHttpTextFormat httpTextFormat =
+        DistributedContextHttpTextFormat.getInstance();
+    Map<String, String> dataCarrier = new HashMap<>();
+    dataCarrier.put(DistributedContextHttpTextFormat.TRACESTATE, "traceStateData");
+    dataCarrier.put(DistributedContextHttpTextFormat.TRACEPARENT, "traceParentData");
+
+    DistributedContext context =
+        httpTextFormat.extract(
+            dataCarrier,
+            new HttpTextFormat.Getter<Map<String, String>>() {
+              @Nullable
+              @Override
+              public String get(Map<String, String> carrier, String key) {
+                return carrier.get(key);
+              }
+            });
+
+    assertEquals(2, context.getEntries().size());
+    assertEquals(
+        EntryValue.create("traceStateData"),
+        context.getEntryValue(EntryKey.create(DistributedContextHttpTextFormat.TRACESTATE)));
+    assertEquals(
+        EntryValue.create("traceParentData"),
+        context.getEntryValue(EntryKey.create(DistributedContextHttpTextFormat.TRACEPARENT)));
+  }
+
+  @Test
+  public void extract_missingValues() throws Exception {
+    DistributedContextHttpTextFormat httpTextFormat =
+        DistributedContextHttpTextFormat.getInstance();
+    Map<String, String> dataCarrier = new HashMap<>();
+
+    DistributedContext context =
+        httpTextFormat.extract(
+            dataCarrier,
+            new HttpTextFormat.Getter<Map<String, String>>() {
+              @Nullable
+              @Override
+              public String get(Map<String, String> carrier, String key) {
+                return carrier.get(key);
+              }
+            });
+
+    assertEquals(0, context.getEntries().size());
+  }
+}