Avoid allocations when advice doesn't remove any attributes (open-tel…

…emetry#6629)

sdk/metrics/src/main/java/io/opentelemetry/sdk/metrics/internal/view/AdviceAttributesProcessor.java

@@ -23,11 +23,28 @@ final class AdviceAttributesProcessor extends AttributesProcessor {
 
  @Override
  public Attributes process(Attributes incoming, Context context) {
+ // Exit early to avoid allocations if the incoming attributes do not have extra keys to be
+ // filtered
+ if (!hasExtraKeys(incoming)) {
+ return incoming;
+ }
  AttributesBuilder builder = incoming.toBuilder();
  builder.removeIf(key -> !attributeKeys.contains(key));
  return builder.build();
  }
 
+ /** Returns true if {@code attributes} has keys not contained in {@link #attributeKeys}. */
+ private boolean hasExtraKeys(Attributes attributes) {
+ boolean[] result = {false};
+ attributes.forEach(
+ (key, value) -> {
+ if (!result[0] && !attributeKeys.contains(key)) {
+ result[0] = true;
+ }
+ });
+ return result[0];
+ }
+
  @Override
  public boolean usesContext() {
  return false;

sdk/metrics/src/test/java/io/opentelemetry/sdk/metrics/internal/view/AdviceAttributesProcessorTest.java

@@ -24,6 +24,19 @@ void doesNotUseContext() {
  assertThat(new AdviceAttributesProcessor(emptyList()).usesContext()).isFalse();
  }
 
+ @Test
+ void noExtraAttributes() {
+ AttributesProcessor processor =
+ new AdviceAttributesProcessor(asList(stringKey("abc"), stringKey("def")));
+
+ Attributes result =
+ processor.process(
+ Attributes.builder().put(stringKey("abc"), "abc").put(stringKey("def"), "def").build(),
+ Context.root());
+
+ assertThat(result).containsOnly(entry(stringKey("abc"), "abc"), entry(stringKey("def"), "def"));
+ }
+
  @Test
  void removeUnwantedAttributes() {
  AttributesProcessor processor =