use spring-webflux-5.1+ ClientResponse.rawStatusCode when available (DataDog/dd-trace-java#1711)

instrumentation/spring/spring-webflux-5.0/spring-webflux-5.0-auto/spring-webflux-5.0-auto.gradle

@@ -7,6 +7,16 @@ apply from: "$rootDir/gradle/instrumentation.gradle"
 
 muzzle {
   pass {
+    name = "webflux_5.0.0+_with_netty_0.8.0"
+    group = "org.springframework"
+    module = "spring-webflux"
+    versions = "[5.0.0.RELEASE,)"
+    assertInverse = true
+    extraDependency "io.projectreactor.netty:reactor-netty:0.8.0.RELEASE"
+  }
+
+  pass {
+    name = "webflux_5.0.0_with_ipc_0.7.0"
     group = "org.springframework"
     module = "spring-webflux"
     versions = "[5.0.0.RELEASE,)"
@@ -15,6 +25,15 @@ muzzle {
   }
 
   pass {
+    name = "netty_0.8.0+_with_spring-webflux:5.1.0"
+    group = "io.projectreactor.netty"
+    module = "reactor-netty"
+    versions = "[0.8.0.RELEASE,)"
+    extraDependency "org.springframework:spring-webflux:5.1.0.RELEASE"
+  }
+
+  pass {
+    name = "ipc_0.7.0+_with_spring-webflux:5.0.0"
     group = "io.projectreactor.ipc"
     module = "reactor-netty"
     versions = "[0.7.0.RELEASE,)"

instrumentation/spring/spring-webflux-5.0/spring-webflux-5.0-library/src/main/java/io/opentelemetry/instrumentation/spring/webflux/client/SpringWebfluxHttpClientTracer.java

@@ -22,6 +22,9 @@ import io.opentelemetry.context.propagation.TextMapPropagator.Setter;
 import io.opentelemetry.instrumentation.api.tracer.HttpClientTracer;
 import io.opentelemetry.trace.Span;
 import io.opentelemetry.trace.Tracer;
+import java.lang.invoke.MethodHandle;
+import java.lang.invoke.MethodHandles;
+import java.lang.invoke.MethodType;
 import java.net.URI;
 import java.util.List;
 import org.springframework.web.reactive.function.client.ClientRequest;
@@ -32,6 +35,8 @@ public class SpringWebfluxHttpClientTracer
 
   public static final SpringWebfluxHttpClientTracer TRACER = new SpringWebfluxHttpClientTracer();
 
+  private static final MethodHandle RAW_STATUS_CODE = findRawStatusCode();
+
   public void onCancel(Span span) {
     span.setAttribute("event", "cancelled");
     span.setAttribute("message", "The subscription was cancelled");
@@ -49,6 +54,15 @@ public class SpringWebfluxHttpClientTracer
 
   @Override
   protected Integer status(ClientResponse httpResponse) {
+    if (RAW_STATUS_CODE != null) {
+      // rawStatusCode() method was introduced in webflux 5.1
+      try {
+        return (int) RAW_STATUS_CODE.invokeExact(httpResponse);
+      } catch (Throwable ignored) {
+      }
+    }
+    // prior to webflux 5.1, the best we can get is HttpStatus enum, which only covers standard
+    // status codes
     return httpResponse.statusCode().value();
   }
 
@@ -76,4 +90,16 @@ public class SpringWebfluxHttpClientTracer
   public Tracer getTracer() {
     return tracer;
   }
+
+  // rawStatusCode() method was introduced in webflux 5.1
+  // prior to this method, the best we can get is HttpStatus enum, which only covers standard status
+  // codes (see usage above)
+  private static MethodHandle findRawStatusCode() {
+    try {
+      return MethodHandles.publicLookup()
+          .findVirtual(ClientResponse.class, "rawStatusCode", MethodType.methodType(int.class));
+    } catch (IllegalAccessException | NoSuchMethodException e) {
+      return null;
+    }
+  }
 }