add grpc mappings for blocking status code (#399)

Author: shashank11p

instrumentation/grpc-1.6/src/main/java/io/opentelemetry/javaagent/instrumentation/hypertrace/grpc/v1_6/server/GrpcServerInterceptor.java

@@ -61,9 +61,9 @@ public <ReqT, RespT> ServerCall.Listener<ReqT> interceptCall(
       FilterResult filterResult =
           FilterRegistry.getFilter().evaluateRequestHeaders(currentSpan, mapHeaders);
       if (filterResult.shouldBlock()) {
+        // map http codes with grpc codes
         // We cannot send custom message in grpc calls
-        // TODO: map http codes with grpc codes. filterResult.getBlockingStatusCode()
-        call.close(Status.PERMISSION_DENIED, new Metadata());
+        call.close(mapHttpToGrpcStatus(filterResult.getBlockingStatusCode()), new Metadata());
         @SuppressWarnings("unchecked")
         ServerCall.Listener<ReqT> noop = NoopServerCallListener.INSTANCE;
         return noop;
@@ -78,6 +78,32 @@ public <ReqT, RespT> ServerCall.Listener<ReqT> interceptCall(
     }
   }
 
+  /**
+   * Mapping according to https://github.com/grpc/grpc/blob/master/doc/http-grpc-status-mapping.md
+   */
+  private static Status mapHttpToGrpcStatus(int httpStatus) {
+    switch (httpStatus) {
+      case 400:
+        return Status.INTERNAL;
+      case 401:
+        return Status.UNAUTHENTICATED;
+      case 403:
+        return Status.PERMISSION_DENIED;
+      case 404:
+        return Status.UNIMPLEMENTED;
+      case 429:
+        return Status.UNAVAILABLE;
+      case 502:
+        return Status.UNAVAILABLE;
+      case 503:
+        return Status.UNAVAILABLE;
+      case 504:
+        return Status.UNAVAILABLE;
+      default:
+        return Status.UNKNOWN;
+    }
+  }
+
   static final class TracingServerCall<ReqT, RespT>
       extends ForwardingServerCall.SimpleForwardingServerCall<ReqT, RespT> {