Check conformance to grpc.GenericRpcHandler type

2 files changed, 23 insertions, 4 deletions

diff --git a/src/python/grpcio/grpc/__init__.py b/src/python/grpcio/grpc/__init__.py
index 0f31119467..5a9762043f 100644
--- a/src/python/grpcio/grpc/__init__.py
+++ b/src/python/grpcio/grpc/__init__.py
@@ -1656,9 +1656,11 @@ def server(thread_pool,
       A Server object.
     """
     from grpc import _server  # pylint: disable=cyclic-import
-    return _server.Server(thread_pool, () if handlers is None else handlers, ()
-                          if interceptors is None else interceptors, () if
-                          options is None else options, maximum_concurrent_rpcs)
+    return _server.create_server(thread_pool, ()
+                                 if handlers is None else handlers, ()
+                                 if interceptors is None else interceptors, ()
+                                 if options is None else options,
+                                 maximum_concurrent_rpcs)
 
 
 ###################################  __all__  #################################
diff --git a/src/python/grpcio/grpc/_server.py b/src/python/grpcio/grpc/_server.py
index d12a2421cd..61d9d70667 100644
--- a/src/python/grpcio/grpc/_server.py
+++ b/src/python/grpcio/grpc/_server.py
@@ -787,7 +787,16 @@ def _start(state):
         thread.start()
 
 
-class Server(grpc.Server):
+def _validate_generic_rpc_handlers(generic_rpc_handlers):
+    for generic_rpc_handler in generic_rpc_handlers:
+        service_attribute = getattr(generic_rpc_handler, 'service', None)
+        if service_attribute is None:
+            raise AttributeError(
+                '"{}" must conform to grpc.GenericRpcHandler type but does '
+                'not have "service" method!'.format(generic_rpc_handler))
+
+
+class _Server(grpc.Server):
 
     # pylint: disable=too-many-arguments
     def __init__(self, thread_pool, generic_handlers, interceptors, options,
@@ -800,6 +809,7 @@ class Server(grpc.Server):
                                    thread_pool, maximum_concurrent_rpcs)
 
     def add_generic_rpc_handlers(self, generic_rpc_handlers):
+        _validate_generic_rpc_handlers(generic_rpc_handlers)
         _add_generic_handlers(self._state, generic_rpc_handlers)
 
     def add_insecure_port(self, address):
@@ -817,3 +827,10 @@ class Server(grpc.Server):
 
     def __del__(self):
         _stop(self._state, None)
+
+
+def create_server(thread_pool, generic_rpc_handlers, interceptors, options,
+                  maximum_concurrent_rpcs):
+    _validate_generic_rpc_handlers(generic_rpc_handlers)
+    return _Server(thread_pool, generic_rpc_handlers, interceptors, options,
+                   maximum_concurrent_rpcs)