fix(grpc): Fix large payload handling when using the emulator. (#975)

Align ndb emulator grpc channel overrides with production overrides.

google/cloud/ndb/client.py

@@ -147,7 +147,14 @@ def __init__(
             )
 
         if emulator:
-            channel = grpc.insecure_channel(self.host)
+            channel = grpc.insecure_channel(
+                self.host,
+                options=[
+                    # Default options provided in DatastoreGrpcTransport, but not when we override the channel.
+                    ("grpc.max_send_message_length", -1),
+                    ("grpc.max_receive_message_length", -1),
+                ],
+            )
         else:
             user_agent = self.client_info.to_user_agent()
             channel = _helpers.make_secure_channel(

tests/system/test_crud.py

@@ -401,6 +401,24 @@ def insert(foo):
     thread2.join()
 
 
+@pytest.mark.usefixtures("client_context")
+def test_large_rpc_lookup(dispose_of, ds_client):
+    class SomeKind(ndb.Model):
+        foo = ndb.TextProperty()
+
+    foo = "a" * (500 * 1024)
+
+    keys = []
+    for i in range(15):
+        key = SomeKind(foo=foo).put()
+        dispose_of(key._key)
+        keys.append(key)
+
+    retrieved = ndb.get_multi(keys)
+    for entity in retrieved:
+        assert entity.foo == foo
+
+
 @pytest.mark.usefixtures("client_context")
 def test_large_json_property(dispose_of, ds_client):
     class SomeKind(ndb.Model):