Add baggage span processor

.github/component_owners.yml

@@ -19,6 +19,8 @@ components:
   aws-xray-propagator:
     - wangzlei
     - srprash
+  baggage-procesor:
+    - mikegoldsmith
   compressors:
     - jack-berg
   consistent-sampling:

baggage-processor/README.md

@@ -0,0 +1,19 @@
+# OpenTelemetry Baggage Span Processor
+
+The BaggageActivityProcessor reads entries stored in Baggage from the parent context
+and adds the baggage keys and values to the `Activity` as tags(attributes) on start.
+
+Add this activity processor to a tracer provider.
+
+Warning!
+
+To repeat: a consequence of adding data to Baggage is that the keys and values
+will appear in all outgoing trace context headers from the application.
+
+Do not put sensitive information in Baggage.
+
+## Component owners
+
+- [Mike Golsmith](https://github.com/MikeGoldsmith), Honeycomb
+
+Learn more about component owners in [component_owners.yml](../.github/component_owners.yml).

baggage-processor/build.gradle.kts

@@ -0,0 +1,16 @@
+plugins {
+  id("otel.java-conventions")
+
+  id("otel.publish-conventions")
+}
+
+description = "OpenTelemetry Baggage Span Processor"
+otelJava.moduleName.set("io.opentelemetry.contrib.baggage.processor")
+
+dependencies {
+  api("io.opentelemetry:opentelemetry-api")
+  api("io.opentelemetry:opentelemetry-sdk")
+  api("io.opentelemetry:opentelemetry-sdk-extension-autoconfigure-spi")
+
+  testImplementation("io.opentelemetry:opentelemetry-sdk-extension-autoconfigure")
+}

baggage-processor/gradle.properties

@@ -0,0 +1,2 @@
+# TODO: uncomment when ready to mark as stable
+# otel.stable=true

baggage-processor/src/main/java/io/opentelemetry/contrib/baggage/processor/BaggageSpanProcessor.java

@@ -0,0 +1,37 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.contrib.baggage.processor;
+
+import io.opentelemetry.api.baggage.Baggage;
+import io.opentelemetry.context.Context;
+import io.opentelemetry.sdk.trace.ReadWriteSpan;
+import io.opentelemetry.sdk.trace.ReadableSpan;
+import io.opentelemetry.sdk.trace.SpanProcessor;
+
+/**
+ * This span processor copies attributes stored in {@link Baggage} into each newly created {@link
+ * io.opentelemetry.api.trace.Span}.
+ */
+public class BaggageSpanProcessor implements SpanProcessor {
+  @Override
+  public void onStart(Context parentContext, ReadWriteSpan span) {
+    Baggage.fromContext(parentContext)
+        .forEach((s, baggageEntry) -> span.setAttribute(s, baggageEntry.getValue()));
+  }
+
+  @Override
+  public boolean isStartRequired() {
+    return true;
+  }
+
+  @Override
+  public void onEnd(ReadableSpan span) {}
+
+  @Override
+  public boolean isEndRequired() {
+    return false;
+  }
+}

baggage-processor/src/test/java/io/opentelemetry/contrib/baggage/processor/BaggageSpanProcessorTest.java

@@ -0,0 +1,30 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.contrib.baggage.processor;
+
+import io.opentelemetry.api.baggage.Baggage;
+import io.opentelemetry.context.Context;
+import io.opentelemetry.context.Scope;
+import io.opentelemetry.sdk.trace.ReadWriteSpan;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.Mock;
+import org.mockito.Mockito;
+import org.mockito.junit.jupiter.MockitoExtension;
+
+@ExtendWith(MockitoExtension.class)
+public class BaggageSpanProcessorTest {
+
+  @Test
+  public void test_baggageSpanProcessor_adds_attributes_to_spans(@Mock ReadWriteSpan span) {
+    try (BaggageSpanProcessor processor = new BaggageSpanProcessor()) {
+      try (Scope ignore = Baggage.current().toBuilder().put("key", "value").build().makeCurrent()) {
+        processor.onStart(Context.current(), span);
+        Mockito.verify(span).setAttribute("key", "value");
+      }
+    }
+  }
+}

settings.gradle.kts

@@ -62,6 +62,7 @@ include(":all")
 include(":aws-resources")
 include(":aws-xray")
 include(":aws-xray-propagator")
+include(":baggage-processor")
 include(":compressors:compressor-zstd")
 include(":consistent-sampling")
 include(":dependencyManagement")