Add AttributeKeyValue abstraction to common otlp exporters (#7026)

exporters/otlp/common/build.gradle.kts

@@ -15,6 +15,8 @@ val versions: Map<String, String> by project
 dependencies {
   protoSource("io.opentelemetry.proto:opentelemetry-proto:${versions["io.opentelemetry.proto"]}")
 
+  annotationProcessor("com.google.auto.value:auto-value")
+
   api(project(":exporters:common"))
 
   compileOnly(project(":sdk:metrics"))

exporters/otlp/common/src/main/java/io/opentelemetry/exporter/internal/otlp/AttributeKeyValue.java

@@ -0,0 +1,50 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.exporter.internal.otlp;
+
+import io.opentelemetry.api.common.AttributeKey;
+import io.opentelemetry.api.common.Attributes;
+import io.opentelemetry.api.common.KeyValue;
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * Key-value pair of {@link AttributeKey} key and its corresponding value.
+ *
+ * <p>Conceptually if {@link Attributes} is a Map, then this is a Map.Entry. Note that whilst {@link
+ * KeyValue} is similar, this class holds type information on the Key rather than the value.
+ *
+ * <p>NOTE: This class is only used in the profiling signal, and exists in this module and package
+ * because its a common dependency of the modules that use it. Long term, it probably makes more
+ * sense to live in {@code opentelemetry-sdk-profiles} once such a module exists.
+ *
+ * <p>This class is internal and is hence not for public use. Its APIs are unstable and can change
+ * at any time.
+ */
+public interface AttributeKeyValue<T> {
+
+  /** Returns a {@link AttributeKeyValue} for the given {@link AttributeKey} and {@code value}. */
+  static <T> AttributeKeyValue<T> of(AttributeKey<T> attributeKey, T value) {
+    return AttributeKeyValueImpl.create(attributeKey, value);
+  }
+
+  /** Returns a List corresponding to the provided Map. This is a copy, not a view. */
+  @SuppressWarnings("unchecked")
+  static <T> List<AttributeKeyValue<?>> of(Attributes attributes) {
+    List<AttributeKeyValue<?>> result = new ArrayList<>(attributes.size());
+    attributes.forEach(
+        (key, value) -> {
+          result.add(of((AttributeKey<T>) key, (T) value));
+        });
+    return result;
+  }
+
+  /** Returns the key. */
+  AttributeKey<T> getAttributeKey();
+
+  /** Returns the value. */
+  T getValue();
+}

exporters/otlp/common/src/main/java/io/opentelemetry/exporter/internal/otlp/AttributeKeyValueImpl.java

@@ -0,0 +1,19 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.exporter.internal.otlp;
+
+import com.google.auto.value.AutoValue;
+import io.opentelemetry.api.common.AttributeKey;
+
+@AutoValue
+abstract class AttributeKeyValueImpl<T> implements AttributeKeyValue<T> {
+
+  AttributeKeyValueImpl() {}
+
+  static <T> AttributeKeyValueImpl<T> create(AttributeKey<T> attributeKey, T value) {
+    return new AutoValue_AttributeKeyValueImpl<T>(attributeKey, value);
+  }
+}

exporters/otlp/common/src/main/java/io/opentelemetry/exporter/internal/otlp/KeyValueMarshaler.java

@@ -17,6 +17,7 @@
 import java.nio.charset.StandardCharsets;
 import java.util.List;
 import java.util.function.BiConsumer;
+import java.util.function.Consumer;
 
 /**
  * A Marshaler of key value pairs.
@@ -65,6 +66,28 @@ public void accept(AttributeKey<?> attributeKey, Object o) {
     return marshalers;
   }
 
+  @SuppressWarnings("AvoidObjectArrays")
+  public static KeyValueMarshaler[] createRepeated(List<AttributeKeyValue<?>> items) {
+    if (items.isEmpty()) {
+      return EMPTY_REPEATED;
+    }
+
+    KeyValueMarshaler[] keyValueMarshalers = new KeyValueMarshaler[items.size()];
+    items.forEach(
+        item ->
+            new Consumer<AttributeKeyValue<?>>() {
+              int index = 0;
+
+              @Override
+              public void accept(AttributeKeyValue<?> attributeKeyValue) {
+                keyValueMarshalers[index++] =
+                    KeyValueMarshaler.create(
+                        attributeKeyValue.getAttributeKey(), attributeKeyValue.getValue());
+              }
+            });
+    return keyValueMarshalers;
+  }
+
   @SuppressWarnings("unchecked")
   private static KeyValueMarshaler create(AttributeKey<?> attributeKey, Object value) {
     byte[] keyUtf8;

exporters/otlp/common/src/test/java/io/opentelemetry/exporter/internal/otlp/AttributeKeyValueTest.java

@@ -0,0 +1,49 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.exporter.internal.otlp;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import io.opentelemetry.api.common.AttributeKey;
+import io.opentelemetry.api.common.AttributeType;
+import io.opentelemetry.api.common.Attributes;
+import java.util.Collections;
+import java.util.List;
+import nl.jqno.equalsverifier.EqualsVerifier;
+import org.assertj.core.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+class AttributeKeyValueTest {
+
+  @Test
+  void equalsVerifier() {
+    EqualsVerifier.forClass(AttributeKeyValue.class).verify();
+  }
+
+  @Test
+  void ofEmpty() {
+    assertThat(AttributeKeyValue.of(Attributes.empty())).isEmpty();
+  }
+
+  @Test
+  void ofOne() {
+    AttributeKeyValue<String> input = AttributeKeyValue.of(AttributeKey.stringKey("foo"), "bar");
+    Attributes attributes = Attributes.of(input.getAttributeKey(), input.getValue());
+    List<AttributeKeyValue<?>> list = AttributeKeyValue.of(attributes);
+    Assertions.assertThat(list).hasSize(1);
+    assertThat(list.get(0)).isEqualTo(input);
+  }
+
+  @Test
+  void ofList() {
+    AttributeKeyValue<List<Long>> input =
+        AttributeKeyValue.of(AttributeKey.longArrayKey("foo"), Collections.emptyList());
+    Attributes attributes = Attributes.of(input.getAttributeKey(), input.getValue());
+    List<AttributeKeyValue<?>> list = AttributeKeyValue.of(attributes);
+    Assertions.assertThat(list).hasSize(1);
+    assertThat(list.get(0).getAttributeKey().getType()).isEqualTo(AttributeType.LONG_ARRAY);
+  }
+}