Hide default context propagators implementation behind interface.

api/src/main/java/io/opentelemetry/api/DefaultOpenTelemetry.java

@@ -10,7 +10,6 @@
 import io.opentelemetry.api.metrics.MeterProvider;
 import io.opentelemetry.api.trace.TracerProvider;
 import io.opentelemetry.context.propagation.ContextPropagators;
-import io.opentelemetry.context.propagation.DefaultContextPropagators;
 import io.opentelemetry.spi.OpenTelemetryFactory;
 import io.opentelemetry.spi.metrics.MeterProviderFactory;
 import io.opentelemetry.spi.trace.TracerProviderFactory;
@@ -124,7 +123,7 @@ public Builder toBuilder() {
  }
 
  protected static class Builder implements OpenTelemetryBuilder<Builder> {
- protected ContextPropagators propagators = DefaultContextPropagators.builder().build();
+ protected ContextPropagators propagators = ContextPropagators.noop();
 
  protected TracerProvider tracerProvider;
  protected MeterProvider meterProvider;

api/src/test/java/io/opentelemetry/api/OpenTelemetryTest.java

@@ -27,7 +27,6 @@
 import io.opentelemetry.api.trace.Tracer;
 import io.opentelemetry.api.trace.TracerProvider;
 import io.opentelemetry.context.propagation.ContextPropagators;
-import io.opentelemetry.context.propagation.DefaultContextPropagators;
 import io.opentelemetry.spi.metrics.MeterProviderFactory;
 import io.opentelemetry.spi.trace.TracerProviderFactory;
 import java.io.File;
@@ -64,7 +63,6 @@ void testDefault() {
  .isEqualTo("DefaultMeterProvider");
  assertThat(OpenTelemetry.getGlobalMeterProvider())
  .isSameAs(OpenTelemetry.getGlobalMeterProvider());
- assertThat(OpenTelemetry.getGlobalPropagators()).isInstanceOf(DefaultContextPropagators.class);
  assertThat(OpenTelemetry.getGlobalPropagators()).isSameAs(OpenTelemetry.getGlobalPropagators());
  }
 
@@ -156,14 +154,14 @@ void testMeterNotFound() {
 
  @Test
  void testGlobalPropagatorsSet() {
- ContextPropagators propagators = DefaultContextPropagators.builder().build();
+ ContextPropagators propagators = ContextPropagators.noop();
  OpenTelemetry.setGlobalPropagators(propagators);
  assertThat(OpenTelemetry.getGlobalPropagators()).isEqualTo(propagators);
  }
 
  @Test
  void testPropagatorsSet() {
- ContextPropagators propagators = DefaultContextPropagators.builder().build();
+ ContextPropagators propagators = ContextPropagators.noop();
  OpenTelemetry instance = DefaultOpenTelemetry.builder().build();
  instance.setPropagators(propagators);
  assertThat(instance.getPropagators()).isEqualTo(propagators);

context/src/main/java/io/opentelemetry/context/propagation/ContextPropagators.java

@@ -5,6 +5,8 @@
 
 package io.opentelemetry.context.propagation;
 
+import static java.util.Objects.requireNonNull;
+
 import javax.annotation.concurrent.ThreadSafe;
 
 /**
@@ -70,6 +72,32 @@
 @ThreadSafe
 public interface ContextPropagators {
 
+ /**
+ * Returns a {@link ContextPropagators} which can be used to extract and inject context in text
+ * payloads with the given {@link TextMapPropagator}. Use {@link
+ * TextMapPropagator#composite(TextMapPropagator...)} to register multiple propagators, which will
+ * all be executed when extracting or injecting.
+ *
+ * <pre>{@code
+ * ContextPropagators propagators = ContextPropagators.create(
+ * TextMapPropagator.composite(
+ * HttpTraceContext.getInstance(),
+ * W3CBaggagePropagator.getInstance(),
+ * new MyCustomContextPropagator()));
+ * }</pre>
+ */
+ @SuppressWarnings("deprecation")
+ static ContextPropagators create(TextMapPropagator textPropagator) {
+ requireNonNull(textPropagator, "textPropagator");
+ return new DefaultContextPropagators(textPropagator);
+ }
+
+ /** Returns a {@link ContextPropagators} which performs no injection or extraction. */
+ @SuppressWarnings("deprecation")
+ static ContextPropagators noop() {
+ return DefaultContextPropagators.noop();
+ }
+
  /**
  * Returns a {@link TextMapPropagator} propagator.
  *

context/src/main/java/io/opentelemetry/context/propagation/DefaultContextPropagators.java

@@ -5,13 +5,8 @@
 
 package io.opentelemetry.context.propagation;
 
-import io.opentelemetry.context.Context;
 import java.util.ArrayList;
-import java.util.Collections;
-import java.util.LinkedHashSet;
 import java.util.List;
-import java.util.Set;
-import javax.annotation.Nullable;
 
 /**
  * {@code DefaultContextPropagators} is the default, built-in implementation of {@link
@@ -21,8 +16,19 @@
  * synchronically upon injection and extraction.
  *
  * <p>The propagation fields retrieved from all registered propagators are de-duplicated.
+ *
+ * @deprecated Use {@link ContextPropagators#create(TextMapPropagator)}
  */
+@Deprecated
 public final class DefaultContextPropagators implements ContextPropagators {
+
+ private static final ContextPropagators NOOP =
+ new DefaultContextPropagators(NoopTextMapPropagator.getInstance());
+
+ static ContextPropagators noop() {
+ return NOOP;
+ }
+
  private final TextMapPropagator textMapPropagator;
 
  @Override
@@ -35,45 +41,32 @@ public TextMapPropagator getTextMapPropagator() {
  * object.
  *
  * @return a {@link DefaultContextPropagators.Builder}.
+ * @deprecated Use {@link ContextPropagators#create(TextMapPropagator)}
  */
+ @Deprecated
  public static Builder builder() {
  return new Builder();
  }
 
- private DefaultContextPropagators(TextMapPropagator textMapPropagator) {
+ DefaultContextPropagators(TextMapPropagator textMapPropagator) {
  this.textMapPropagator = textMapPropagator;
  }
 
  /**
- * {@link Builder} is used to construct a new {@code ContextPropagators} object with the specified
- * propagators.
+ * A builder of {@link DefaultContextPropagators}.
  *
- * <p>Invocation order of {@code TextMapPropagator#inject()} and {@code
- * TextMapPropagator#extract()} for registered trace propagators is undefined.
- *
- * <p>This is a example of a {@code ContextPropagators} object being created:
- *
- * <pre>{@code
- * ContextPropagators propagators = DefaultContextPropagators.builder()
- * .addTextMapPropagator(new HttpTraceContext())
- * .addTextMapPropagator(new HttpBaggage())
- * .addTextMapPropagator(new MyCustomContextPropagator())
- * .build();
- * }</pre>
+ * @deprecated Use {@link ContextPropagators#create(TextMapPropagator)}
  */
+ @Deprecated
  public static final class Builder {
  List<TextMapPropagator> textPropagators = new ArrayList<>();
 
  /**
- * Adds a {@link TextMapPropagator} propagator.
+ * Add a {@link TextMapPropagator}.
  *
- * <p>One propagator per concern (traces, correlations, etc) should be added if this format is
- * supported.
- *
- * @param textMapPropagator the propagator to be added.
- * @return this.
- * @throws NullPointerException if {@code textMapPropagator} is {@code null}.
+ * @deprecated Use {@link ContextPropagators#create(TextMapPropagator)}
  */
+ @Deprecated
  public Builder addTextMapPropagator(TextMapPropagator textMapPropagator) {
  if (textMapPropagator == null) {
  throw new NullPointerException("textMapPropagator");
@@ -84,73 +77,13 @@ public Builder addTextMapPropagator(TextMapPropagator textMapPropagator) {
  }
 
  /**
- * Builds a new {@code ContextPropagators} with the specified propagators.
+ * Returns a {@link ContextPropagators}.
  *
- * @return the newly created {@code ContextPropagators} instance.
+ * @deprecated Use {@link ContextPropagators#create(TextMapPropagator)}
  */
+ @Deprecated
  public ContextPropagators build() {
- if (textPropagators.isEmpty()) {
- return new DefaultContextPropagators(NoopTextMapPropagator.INSTANCE);
- }
-
- return new DefaultContextPropagators(new MultiTextMapPropagator(textPropagators));
- }
- }
-
- private static final class MultiTextMapPropagator implements TextMapPropagator {
- private final TextMapPropagator[] textPropagators;
- private final List<String> allFields;
-
- private MultiTextMapPropagator(List<TextMapPropagator> textPropagators) {
- this.textPropagators = new TextMapPropagator[textPropagators.size()];
- textPropagators.toArray(this.textPropagators);
- this.allFields = Collections.unmodifiableList(getAllFields(this.textPropagators));
- }
-
- @Override
- public List<String> fields() {
- return allFields;
- }
-
- private static List<String> getAllFields(TextMapPropagator[] textPropagators) {
- Set<String> fields = new LinkedHashSet<>();
- for (int i = 0; i < textPropagators.length; i++) {
- fields.addAll(textPropagators[i].fields());
- }
-
- return new ArrayList<>(fields);
- }
-
- @Override
- public <C> void inject(Context context, @Nullable C carrier, Setter<C> setter) {
- for (int i = 0; i < textPropagators.length; i++) {
- textPropagators[i].inject(context, carrier, setter);
- }
- }
-
- @Override
- public <C> Context extract(Context context, @Nullable C carrier, Getter<C> getter) {
- for (int i = 0; i < textPropagators.length; i++) {
- context = textPropagators[i].extract(context, carrier, getter);
- }
- return context;
- }
- }
-
- private static final class NoopTextMapPropagator implements TextMapPropagator {
- private static final NoopTextMapPropagator INSTANCE = new NoopTextMapPropagator();
-
- @Override
- public List<String> fields() {
- return Collections.emptyList();
- }
-
- @Override
- public <C> void inject(Context context, @Nullable C carrier, Setter<C> setter) {}
-
- @Override
- public <C> Context extract(Context context, @Nullable C carrier, Getter<C> getter) {
- return context;
+ return ContextPropagators.create(TextMapPropagator.composite(textPropagators));
  }
  }
 }

context/src/main/java/io/opentelemetry/context/propagation/MultiTextMapPropagator.java

@@ -0,0 +1,54 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.context.propagation;
+
+import io.opentelemetry.context.Context;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.LinkedHashSet;
+import java.util.List;
+import java.util.Set;
+import javax.annotation.Nullable;
+
+final class MultiTextMapPropagator implements TextMapPropagator {
+ private final TextMapPropagator[] textPropagators;
+ private final List<String> allFields;
+
+ MultiTextMapPropagator(List<TextMapPropagator> textPropagators) {
+ this.textPropagators = new TextMapPropagator[textPropagators.size()];
+ textPropagators.toArray(this.textPropagators);
+ this.allFields = Collections.unmodifiableList(getAllFields(this.textPropagators));
+ }
+
+ @Override
+ public List<String> fields() {
+ return allFields;
+ }
+
+ private static List<String> getAllFields(TextMapPropagator[] textPropagators) {
+ Set<String> fields = new LinkedHashSet<>();
+ for (int i = 0; i < textPropagators.length; i++) {
+ fields.addAll(textPropagators[i].fields());
+ }
+
+ return new ArrayList<>(fields);
+ }
+
+ @Override
+ public <C> void inject(Context context, @Nullable C carrier, Setter<C> setter) {
+ for (int i = 0; i < textPropagators.length; i++) {
+ textPropagators[i].inject(context, carrier, setter);
+ }
+ }
+
+ @Override
+ public <C> Context extract(Context context, @Nullable C carrier, Getter<C> getter) {
+ for (int i = 0; i < textPropagators.length; i++) {
+ context = textPropagators[i].extract(context, carrier, getter);
+ }
+ return context;
+ }
+}

context/src/main/java/io/opentelemetry/context/propagation/NoopTextMapPropagator.java

@@ -0,0 +1,32 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.context.propagation;
+
+import io.opentelemetry.context.Context;
+import java.util.Collections;
+import java.util.List;
+import javax.annotation.Nullable;
+
+final class NoopTextMapPropagator implements TextMapPropagator {
+ private static final NoopTextMapPropagator INSTANCE = new NoopTextMapPropagator();
+
+ static TextMapPropagator getInstance() {
+ return INSTANCE;
+ }
+
+ @Override
+ public List<String> fields() {
+ return Collections.emptyList();
+ }
+
+ @Override
+ public <C> void inject(Context context, @Nullable C carrier, Setter<C> setter) {}
+
+ @Override
+ public <C> Context extract(Context context, @Nullable C carrier, Getter<C> getter) {
+ return context;
+ }
+}

context/src/main/java/io/opentelemetry/context/propagation/TextMapPropagator.java

@@ -6,6 +6,8 @@
 package io.opentelemetry.context.propagation;
 
 import io.opentelemetry.context.Context;
+import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.List;
 import javax.annotation.Nullable;
 import javax.annotation.concurrent.ThreadSafe;
@@ -39,6 +41,39 @@
  */
 @ThreadSafe
 public interface TextMapPropagator {
+
+ /**
+ * Returns a {@link TextMapPropagator} which simply delegates injection and extraction to the
+ * provided propagators.
+ *
+ * <p>Invocation order of {@code TextMapPropagator#inject()} and {@code
+ * TextMapPropagator#extract()} for registered trace propagators is undefined.
+ */
+ static TextMapPropagator composite(TextMapPropagator... propagators) {
+ return composite(Arrays.asList(propagators));
+ }
+
+ /**
+ * Returns a {@link TextMapPropagator} which simply delegates injection and extraction to the
+ * provided propagators.
+ *
+ * <p>Invocation order of {@code TextMapPropagator#inject()} and {@code
+ * TextMapPropagator#extract()} for registered trace propagators is undefined.
+ */
+ static TextMapPropagator composite(Iterable<TextMapPropagator> propagators) {
+ List<TextMapPropagator> propagatorsList = new ArrayList<>();
+ for (TextMapPropagator propagator : propagators) {
+ propagatorsList.add(propagator);
+ }
+ if (propagatorsList.isEmpty()) {
+ return NoopTextMapPropagator.getInstance();
+ }
+ if (propagatorsList.size() == 1) {
+ return propagatorsList.get(0);
+ }
+ return new MultiTextMapPropagator(propagatorsList);
+ }
+
  /**
  * The propagation fields defined. If your carrier is reused, you should delete the fields here
  * before calling {@link #inject(Context, Object, Setter)} )}.