fix: retry grpc UNKNOWN errors (#458)

Fixes #310

Author: Chris Rossi

packages/google-cloud-ndb/google/cloud/ndb/_retry.py

@@ -102,6 +102,7 @@ def retry_wrapper(*args, **kwargs):
     core_exceptions.ServiceUnavailable,
     core_exceptions.InternalServerError,
     core_exceptions.Aborted,
+    core_exceptions.Unknown,
 )
 
 

packages/google-cloud-ndb/tests/unit/test__retry.py

@@ -178,3 +178,11 @@ def test_aborted(core_retry):
         core_retry.if_transient_error.return_value = False
         assert _retry.is_transient_error(error) is True
         core_retry.if_transient_error.assert_called_once_with(error)
+
+    @staticmethod
+    @mock.patch("google.cloud.ndb._retry.core_retry")
+    def test_unknown(core_retry):
+        error = core_exceptions.Unknown("testing")
+        core_retry.if_transient_error.return_value = False
+        assert _retry.is_transient_error(error) is True
+        core_retry.if_transient_error.assert_called_once_with(error)