Enhancement/add additionalServerExtractors (#7155)

fixes issue #7153

Co-authored-by: Trask Stalnaker <trask.stalnaker@gmail.com>

instrumentation/grpc-1.6/library/src/main/java/io/opentelemetry/instrumentation/grpc/v1_6/GrpcTelemetryBuilder.java

@@ -48,6 +48,8 @@ public final class GrpcTelemetryBuilder {
       additionalExtractors = new ArrayList<>();
   private final List<AttributesExtractor<? super GrpcRequest, ? super Status>>
       additionalClientExtractors = new ArrayList<>();
+  private final List<AttributesExtractor<? super GrpcRequest, ? super Status>>
+      additionalServerExtractors = new ArrayList<>();
 
   private boolean captureExperimentalSpanAttributes;
 
@@ -78,6 +80,18 @@ public final class GrpcTelemetryBuilder {
     return this;
   }
 
+  /**
+   * Adds an extra server-only {@link AttributesExtractor} to invoke to set attributes to
+   * instrumented items. The {@link AttributesExtractor} will be executed after all default
+   * extractors.
+   */
+  @CanIgnoreReturnValue
+  public GrpcTelemetryBuilder addServerAttributeExtractor(
+      AttributesExtractor<? super GrpcRequest, ? super Status> attributesExtractor) {
+    additionalServerExtractors.add(attributesExtractor);
+    return this;
+  }
+
   /** Sets custom client {@link SpanNameExtractor} via transform function. */
   @CanIgnoreReturnValue
   public GrpcTelemetryBuilder setClientSpanNameExtractor(
@@ -154,6 +168,7 @@ public final class GrpcTelemetryBuilder {
         .addAttributesExtractor(RpcServerAttributesExtractor.create(rpcAttributesGetter))
         .addAttributesExtractor(
             NetServerAttributesExtractor.create(new GrpcNetServerAttributesGetter()))
+        .addAttributesExtractors(additionalServerExtractors)
         .addOperationMetrics(RpcServerMetrics.get());
 
     if (peerService != null) {

instrumentation/grpc-1.6/library/src/test/java/io/opentelemetry/instrumentation/grpc/v1_6/GrpcTest.java

@@ -35,6 +35,7 @@ class GrpcTest extends AbstractGrpcTest {
   static final InstrumentationExtension testing = LibraryInstrumentationExtension.create();
 
   private static final AttributeKey<String> CUSTOM_KEY = AttributeKey.stringKey("customKey");
+  private static final AttributeKey<String> CUSTOM_KEY2 = AttributeKey.stringKey("customKey2");
 
   private static final Metadata.Key<String> CUSTOM_METADATA_KEY =
       Metadata.Key.of("customMetadataKey", Metadata.ASCII_STRING_MARSHALLER);
@@ -56,6 +57,11 @@ class GrpcTest extends AbstractGrpcTest {
     return testing;
   }
 
+  /**
+   * metadataProvided. testing as well 2 extra methods: {@link
+   * GrpcTelemetryBuilder#addClientAttributeExtractor} and {@link
+   * GrpcTelemetryBuilder#addServerAttributeExtractor}
+   */
   @Test
   void metadataProvided() throws Exception {
     BindableService greeter =
@@ -76,6 +82,7 @@ class GrpcTest extends AbstractGrpcTest {
             .intercept(
                 GrpcTelemetry.builder(testing.getOpenTelemetry())
                     .addAttributeExtractor(new CustomAttributesExtractor())
+                    .addServerAttributeExtractor(new CustomAttributesExtractorV2("serverSideValue"))
                     .build()
                     .newServerInterceptor())
             .build()
@@ -87,6 +94,8 @@ class GrpcTest extends AbstractGrpcTest {
                 .intercept(
                     GrpcTelemetry.builder(testing.getOpenTelemetry())
                         .addAttributeExtractor(new CustomAttributesExtractor())
+                        .addClientAttributeExtractor(
+                            new CustomAttributesExtractorV2("clientSideValue"))
                         .build()
                         .newClientInterceptor()));
 
@@ -117,11 +126,13 @@ class GrpcTest extends AbstractGrpcTest {
                         span.hasName("example.Greeter/SayHello")
                             .hasKind(SpanKind.CLIENT)
                             .hasParent(trace.getSpan(0))
+                            .hasAttribute(CUSTOM_KEY2, "clientSideValue")
                             .hasAttribute(CUSTOM_KEY, "customValue"),
                     span ->
                         span.hasName("example.Greeter/SayHello")
                             .hasKind(SpanKind.SERVER)
                             .hasParent(trace.getSpan(1))
+                            .hasAttribute(CUSTOM_KEY2, "serverSideValue")
                             .hasAttribute(CUSTOM_KEY, "customValue")));
   }
 
@@ -149,4 +160,29 @@ class GrpcTest extends AbstractGrpcTest {
       }
     }
   }
+
+  private static class CustomAttributesExtractorV2
+      implements AttributesExtractor<GrpcRequest, Status> {
+
+    private final String valueOfKey2;
+
+    public CustomAttributesExtractorV2(String valueOfKey2) {
+      this.valueOfKey2 = valueOfKey2;
+    }
+
+    @Override
+    public void onStart(
+        AttributesBuilder attributes, Context parentContext, GrpcRequest grpcRequest) {
+
+      attributes.put(CUSTOM_KEY2, valueOfKey2);
+    }
+
+    @Override
+    public void onEnd(
+        AttributesBuilder attributes,
+        Context context,
+        GrpcRequest grpcRequest,
+        @Nullable Status status,
+        @Nullable Throwable error) {}
+  }
 }