system fallback for span name

Author: zeitlinger

instrumentation-api-incubator/src/main/java/io/opentelemetry/instrumentation/api/incubator/semconv/rpc/RpcSpanNameExtractor.java

@@ -31,10 +31,14 @@ private RpcSpanNameExtractor(RpcAttributesGetter<REQUEST, Object> getter) {
   public String extract(REQUEST request) {
     if (SemconvStability.emitStableRpcSemconv()) {
       String method = getter.getRpcMethod(request);
-      if (method == null) {
-        return "RPC request";
+      if (method != null) {
+        return method;
       }
-      return method;
+      String system = getter.getSystem(request);
+      if (system != null) {
+        return system;
+      }
+      return "RPC request";
     }
 
     String service = getter.getService(request);

instrumentation-api-incubator/src/test/java/io/opentelemetry/instrumentation/api/incubator/semconv/rpc/RpcSpanNameExtractorTest.java

@@ -6,6 +6,7 @@
 package io.opentelemetry.instrumentation.api.incubator.semconv.rpc;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.jupiter.api.Assumptions.assumeTrue;
 import static org.mockito.Mockito.when;
 
 import io.opentelemetry.instrumentation.api.instrumenter.SpanNameExtractor;
@@ -39,23 +40,45 @@ void normal() {
   @Test
   @SuppressWarnings("deprecation") // testing deprecated method
   void serviceNull() {
+    assumeTrue(!SemconvStability.emitStableRpcSemconv());
+
     RpcRequest request = new RpcRequest();
 
-    if (!SemconvStability.emitStableRpcSemconv()) {
-      when(getter.getMethod(request)).thenReturn("Method");
-    }
+    when(getter.getMethod(request)).thenReturn("Method");
 
     SpanNameExtractor<RpcRequest> extractor = RpcSpanNameExtractor.create(getter);
     assertThat(extractor.extract(request)).isEqualTo("RPC request");
   }
 
   @Test
   void methodNull() {
+    assumeTrue(!SemconvStability.emitStableRpcSemconv());
+
     RpcRequest request = new RpcRequest();
 
-    if (!SemconvStability.emitStableRpcSemconv()) {
-      when(getter.getService(request)).thenReturn("my.Service");
-    }
+    when(getter.getService(request)).thenReturn("my.Service");
+
+    SpanNameExtractor<RpcRequest> extractor = RpcSpanNameExtractor.create(getter);
+    assertThat(extractor.extract(request)).isEqualTo("RPC request");
+  }
+
+  @Test
+  void rpcMethodSystemFallback() {
+    assumeTrue(SemconvStability.emitStableRpcSemconv());
+
+    RpcRequest request = new RpcRequest();
+
+    when(getter.getSystem(request)).thenReturn("system");
+
+    SpanNameExtractor<RpcRequest> extractor = RpcSpanNameExtractor.create(getter);
+    assertThat(extractor.extract(request)).isEqualTo("system");
+  }
+
+  @Test
+  void rpcMethodNull() {
+    assumeTrue(SemconvStability.emitStableRpcSemconv());
+
+    RpcRequest request = new RpcRequest();
 
     SpanNameExtractor<RpcRequest> extractor = RpcSpanNameExtractor.create(getter);
     assertThat(extractor.extract(request)).isEqualTo("RPC request");