Hide default context propagators implementation behind interface. (#2089

) * Hide default context propagators implementation behind interface. * Deprecate * Revamp
open-telemetry · Nov 20, 2020 · 0e013e5 · 0e013e5
1 parent d940947
commit 0e013e5
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Showing 11 changed files with 187 additions and 131 deletions.
diff --git a/api/src/main/java/io/opentelemetry/api/DefaultOpenTelemetry.java b/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;

diff --git a/api/src/test/java/io/opentelemetry/api/OpenTelemetryTest.java b/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);

diff --git a/context/src/main/java/io/opentelemetry/context/propagation/ContextPropagators.java b/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.
    *

diff --git a/context/src/main/java/io/opentelemetry/context/propagation/DefaultContextPropagators.java b/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));
     }
   }
 }
diff --git a/context/src/main/java/io/opentelemetry/context/propagation/MultiTextMapPropagator.java b/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;
+  }
+}
diff --git a/context/src/main/java/io/opentelemetry/context/propagation/NoopTextMapPropagator.java b/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;
+  }
+}
diff --git a/context/src/main/java/io/opentelemetry/context/propagation/TextMapPropagator.java b/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)} )}.