Add xray propagators that prioritizes xray environment variable

This will allow support for AWS's environment variable with no additional config keys and no changes to instrumentation required.
I included a propagator that did just the env var propagation without the standard xray propagation as well as one that does both but prioritizes xray env propagation first.

aws-xray-propagator/build.gradle.kts

@@ -10,4 +10,5 @@ otelJava.moduleName.set("io.opentelemetry.contrib.awsxray.propagator")
 dependencies {
   api("io.opentelemetry:opentelemetry-api")
   compileOnly("io.opentelemetry:opentelemetry-sdk-extension-autoconfigure-spi")
+  testImplementation("uk.org.webcompere:system-stubs-jupiter:2.0.2")
 }

aws-xray-propagator/src/main/java/io/opentelemetry/contrib/awsxray/propagator/AwsXrayEnvConfigurablePropagator.java

@@ -0,0 +1,26 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.contrib.awsxray.propagator;
+
+import io.opentelemetry.context.propagation.TextMapPropagator;
+import io.opentelemetry.sdk.autoconfigure.spi.ConfigProperties;
+import io.opentelemetry.sdk.autoconfigure.spi.ConfigurablePropagatorProvider;
+
+/**
+ * A {@link ConfigurablePropagatorProvider} which allows enabling the {@link AwsXrayEnvPropagator}
+ * with the propagator name {@code xray-env}.
+ */
+public final class AwsXrayEnvConfigurablePropagator implements ConfigurablePropagatorProvider {
+  @Override
+  public TextMapPropagator getPropagator(ConfigProperties config) {
+    return AwsXrayEnvPropagator.getInstance();
+  }
+
+  @Override
+  public String getName() {
+    return "xray-env";
+  }
+}

aws-xray-propagator/src/main/java/io/opentelemetry/contrib/awsxray/propagator/AwsXrayEnvPropagator.java

@@ -0,0 +1,93 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.contrib.awsxray.propagator;
+
+import io.opentelemetry.context.Context;
+import io.opentelemetry.context.propagation.TextMapGetter;
+import io.opentelemetry.context.propagation.TextMapPropagator;
+import io.opentelemetry.context.propagation.TextMapSetter;
+import java.util.Collections;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import javax.annotation.Nullable;
+
+/**
+ * Implementation of the AWS X-Ray Trace Header propagation protocol only uses Lambda's {@code
+ * _X_AMZN_TRACE_ID} environment variable and {@code com.amazonaws.xray.traceHeader} system property
+ * as the carrier. Carrier passed into {@link #inject(Context, Object, TextMapSetter)} and {@link
+ * #extract(Context, Object, TextMapGetter)} are ignored.
+ *
+ * <p>To register the X-Ray propagator together with default propagator when using the SDK:
+ *
+ * <pre>{@code
+ * OpenTelemetrySdk.builder()
+ *   .setPropagators(
+ *     ContextPropagators.create(
+ *         TextMapPropagator.composite(
+ *             W3CTraceContextPropagator.getInstance(),
+ *             AwsXrayEnvPropagator.getInstance())))
+ *    .build();
+ * }</pre>
+ */
+public final class AwsXrayEnvPropagator implements TextMapPropagator {
+
+  private static final String AWS_TRACE_HEADER_ENV_KEY = "_X_AMZN_TRACE_ID";
+  private static final String AWS_TRACE_HEADER_PROP = "com.amazonaws.xray.traceHeader";
+  private final AwsXrayPropagator xrayPropagator = AwsXrayPropagator.getInstance();
+
+  private static final AwsXrayEnvPropagator INSTANCE = new AwsXrayEnvPropagator();
+
+  private AwsXrayEnvPropagator() {
+    // singleton
+  }
+
+  public static AwsXrayEnvPropagator getInstance() {
+    return INSTANCE;
+  }
+
+  @Override
+  public List<String> fields() {
+    return xrayPropagator.fields();
+  }
+
+  @Override
+  public <C> void inject(Context context, @Nullable C carrier, TextMapSetter<C> setter) {}
+
+  @Override
+  public <C> Context extract(Context context, @Nullable C carrier, TextMapGetter<C> ignored) {
+    String traceHeader = System.getProperty(AWS_TRACE_HEADER_PROP);
+    if (isEmptyOrNull(traceHeader)) {
+      traceHeader = System.getenv(AWS_TRACE_HEADER_ENV_KEY);
+    }
+    if (isEmptyOrNull(traceHeader)) {
+      return context;
+    }
+    return xrayPropagator.extract(
+        context,
+        Collections.singletonMap(AwsXrayPropagator.TRACE_HEADER_KEY, traceHeader),
+        MapGetter.INSTANCE);
+  }
+
+  private static boolean isEmptyOrNull(@Nullable String value) {
+    return value == null || value.isEmpty();
+  }
+
+  private enum MapGetter implements TextMapGetter<Map<String, String>> {
+    INSTANCE;
+
+    @Override
+    public Set<String> keys(Map<String, String> map) {
+      return map.keySet();
+    }
+
+    @Override
+    @Nullable
+    public String get(@Nullable Map<String, String> map, String s) {
+      return map == null ? null : map.get(s);
+    }
+  }
+}

aws-xray-propagator/src/main/java/io/opentelemetry/contrib/awsxray/propagator/AwsXrayLambdaConfigurablePropagator.java

@@ -0,0 +1,26 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.contrib.awsxray.propagator;
+
+import io.opentelemetry.context.propagation.TextMapPropagator;
+import io.opentelemetry.sdk.autoconfigure.spi.ConfigProperties;
+import io.opentelemetry.sdk.autoconfigure.spi.ConfigurablePropagatorProvider;
+
+/**
+ * A {@link ConfigurablePropagatorProvider} which allows enabling the {@link
+ * AwsXrayLambdaPropagator} with the propagator name {@code aws}.
+ */
+public final class AwsXrayLambdaConfigurablePropagator implements ConfigurablePropagatorProvider {
+  @Override
+  public TextMapPropagator getPropagator(ConfigProperties config) {
+    return AwsXrayLambdaPropagator.getInstance();
+  }
+
+  @Override
+  public String getName() {
+    return "aws";
+  }
+}

aws-xray-propagator/src/main/java/io/opentelemetry/contrib/awsxray/propagator/AwsXrayLambdaPropagator.java

@@ -0,0 +1,63 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.contrib.awsxray.propagator;
+
+import io.opentelemetry.context.Context;
+import io.opentelemetry.context.propagation.TextMapGetter;
+import io.opentelemetry.context.propagation.TextMapPropagator;
+import io.opentelemetry.context.propagation.TextMapSetter;
+import java.util.List;
+import javax.annotation.Nullable;
+
+/**
+ * Implementation of the AWS X-Ray Trace Header propagation protocol but with special handling for
+ * Lambda's {@code _X_AMZN_TRACE_ID} environment variable and {@code com.amazonaws.xray.traceHeader}
+ * system property.
+ *
+ * <p>To register the X-Ray propagator together with default propagator when using the SDK:
+ *
+ * <pre>{@code
+ * OpenTelemetrySdk.builder()
+ *   .setPropagators(
+ *     ContextPropagators.create(
+ *         TextMapPropagator.composite(
+ *             W3CTraceContextPropagator.getInstance(),
+ *             AwsXrayLambdaPropagator.getInstance())))
+ *    .build();
+ * }</pre>
+ */
+public final class AwsXrayLambdaPropagator implements TextMapPropagator {
+  private static final AwsXrayPropagator XRAY = AwsXrayPropagator.getInstance();
+  private static final AwsXrayEnvPropagator XRAY_ENV = AwsXrayEnvPropagator.getInstance();
+  private static final AwsXrayLambdaPropagator INSTANCE = new AwsXrayLambdaPropagator();
+
+  private AwsXrayLambdaPropagator() {
+    // singleton
+  }
+
+  public static AwsXrayLambdaPropagator getInstance() {
+    return INSTANCE;
+  }
+
+  @Override
+  public List<String> fields() {
+    return XRAY.fields();
+  }
+
+  @Override
+  public <C> void inject(Context context, @Nullable C carrier, TextMapSetter<C> setter) {
+    XRAY.inject(context, carrier, setter);
+    // XRAY_ENV.inject is a no-op, so no need to invoke.
+  }
+
+  @Override
+  public <C> Context extract(Context context, @Nullable C carrier, TextMapGetter<C> getter) {
+    context = XRAY.extract(context, carrier, getter);
+    // Currently last one wins, so invoke XRAY_ENV second to allow parent to be overwritten.
+    context = XRAY_ENV.extract(context, carrier, getter);
+    return context;
+  }
+}

aws-xray-propagator/src/main/java/io/opentelemetry/contrib/awsxray/propagator/AwsXrayPropagator.java

@@ -38,7 +38,7 @@
  *     ContextPropagators.create(
  *         TextMapPropagator.composite(
  *             W3CTraceContextPropagator.getInstance(),
- *             AWSXrayPropagator.getInstance())))
+ *             AwsXrayPropagator.getInstance())))
  *    .build();
  * }</pre>
  */

aws-xray-propagator/src/test/java/io/opentelemetry/contrib/awsxray/propagator/AwsXrayEnvPropagatorTest.java

@@ -0,0 +1,112 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.contrib.awsxray.propagator;
+
+import static io.opentelemetry.contrib.awsxray.propagator.AwsXrayPropagator.TRACE_HEADER_KEY;
+import static io.opentelemetry.contrib.awsxray.propagator.AwsXrayPropagatorTest.GETTER;
+import static io.opentelemetry.contrib.awsxray.propagator.AwsXrayPropagatorTest.SETTER;
+import static io.opentelemetry.contrib.awsxray.propagator.AwsXrayPropagatorTest.SPAN_ID;
+import static io.opentelemetry.contrib.awsxray.propagator.AwsXrayPropagatorTest.TRACE_ID;
+import static io.opentelemetry.contrib.awsxray.propagator.AwsXrayPropagatorTest.getSpanContext;
+import static io.opentelemetry.contrib.awsxray.propagator.AwsXrayPropagatorTest.withSpanContext;
+import static org.assertj.core.api.Assertions.assertThat;
+
+import io.opentelemetry.api.trace.SpanContext;
+import io.opentelemetry.api.trace.TraceFlags;
+import io.opentelemetry.api.trace.TraceState;
+import io.opentelemetry.context.Context;
+import java.util.Collections;
+import java.util.LinkedHashMap;
+import java.util.Map;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import uk.org.webcompere.systemstubs.environment.EnvironmentVariables;
+import uk.org.webcompere.systemstubs.jupiter.SystemStub;
+import uk.org.webcompere.systemstubs.jupiter.SystemStubsExtension;
+import uk.org.webcompere.systemstubs.properties.SystemProperties;
+
+@ExtendWith(SystemStubsExtension.class)
+class AwsXrayEnvPropagatorTest {
+  private final AwsXrayEnvPropagator subject = AwsXrayEnvPropagator.getInstance();
+
+  @SystemStub final EnvironmentVariables environmentVariables = new EnvironmentVariables();
+  @SystemStub final SystemProperties systemProperties = new SystemProperties();
+
+  @Test
+  void fields_valid() {
+    assertThat(subject.fields()).containsOnly("X-Amzn-Trace-Id");
+  }
+
+  @Test
+  void inject_doesNothing() {
+    Map<String, String> carrier = new LinkedHashMap<>();
+    subject.inject(
+        withSpanContext(
+            SpanContext.create(TRACE_ID, SPAN_ID, TraceFlags.getSampled(), TraceState.getDefault()),
+            Context.current()),
+        carrier,
+        SETTER);
+
+    assertThat(carrier).isEmpty();
+  }
+
+  @Test
+  void extract_carrierIgnored() {
+    Map<String, String> carrier =
+        Collections.singletonMap(
+            TRACE_HEADER_KEY,
+            "Root=1-8a3c60f7-d188f8fa79d48a391a778fa6;Parent=53995c3f42cd8ad8;Sampled=1");
+    assertThat(subject.extract(Context.current(), carrier, GETTER)).isEqualTo(Context.current());
+  }
+
+  @Test
+  void extract_fromEnvironmentVariable() {
+    environmentVariables.set(
+        "_X_AMZN_TRACE_ID",
+        "Root=1-00000000-d188f8fa79d48a391a778fa6;Parent=53995c3f42cd8ad8;Sampled=1;Foo=Bar");
+
+    assertThat(getSpanContext(subject.extract(Context.current(), Collections.emptyMap(), GETTER)))
+        .isEqualTo(
+            SpanContext.createFromRemoteParent(
+                "00000000d188f8fa79d48a391a778fa6",
+                SPAN_ID,
+                TraceFlags.getSampled(),
+                TraceState.getDefault()));
+  }
+
+  @Test
+  void extract_fromSystemProperty() {
+    systemProperties.set(
+        "com.amazonaws.xray.traceHeader",
+        "Root=1-00000000-d188f8fa79d48a391a778fa6;Parent=53995c3f42cd8ad8;Sampled=1;Foo=Bar");
+
+    assertThat(getSpanContext(subject.extract(Context.current(), Collections.emptyMap(), GETTER)))
+        .isEqualTo(
+            SpanContext.createFromRemoteParent(
+                "00000000d188f8fa79d48a391a778fa6",
+                SPAN_ID,
+                TraceFlags.getSampled(),
+                TraceState.getDefault()));
+  }
+
+  @Test
+  void extract_systemPropertyBeforeEnvironmentVariable() {
+    environmentVariables.set(
+        "_X_AMZN_TRACE_ID",
+        "Root=1-00000000-240000000000000000000001;Parent=1600000000000001;Sampled=1;Foo=Bar");
+    systemProperties.set(
+        "com.amazonaws.xray.traceHeader",
+        "Root=1-00000000-240000000000000000000002;Parent=1600000000000002;Sampled=1;Foo=Baz");
+
+    assertThat(getSpanContext(subject.extract(Context.current(), Collections.emptyMap(), GETTER)))
+        .isEqualTo(
+            SpanContext.createFromRemoteParent(
+                "00000000240000000000000000000002",
+                "1600000000000002",
+                TraceFlags.getSampled(),
+                TraceState.getDefault()));
+  }
+}