Updated routing logic for no writers

Author: technige

neo4j/v1/bolt.py

@@ -17,8 +17,9 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-from neo4j.bolt import Response, RUN, PULL_ALL, ServiceUnavailable
-from neo4j.bolt.connection import connect, ConnectionPool, DEFAULT_PORT
+
+from neo4j.bolt.connection import connect, ConnectionPool, DEFAULT_PORT, \
+    PULL_ALL, Response, RUN, ServiceUnavailable
 from neo4j.compat import urlparse
 
 from .api import GraphDatabase, Driver, Session, StatementResult, \

neo4j/v1/routing.py

@@ -211,15 +211,9 @@ def fetch_routing_table(self, address):
 
         # No writers
         if num_writers == 0:
-            if num_routers == 1:
-                # No writers are available and only one router was returned. This
-                # likely indicates a broken cluster so signals an error status.
-                raise ServiceUnavailable("No write servers currently available")
-            else:
-                # No writers are available but multiple routers have been returned.
-                # This likely indicates a temporary state, such as leader switching,
-                # so we should not signal an error.
-                return None
+            # No writers are available. This likely indicates a temporary state,
+            # such as leader switching, so we should not signal an error.
+            return None
 
         # At least one of each is fine, so return this table
         return new_routing_table

test/resources/router_no_writers_one_router.script

@@ -367,14 +367,7 @@ def test_no_readers_should_raise_protocol_error(self):
                 with self.assertRaises(ProtocolError):
                     _ = pool.fetch_routing_table(address)
 
-    def test_no_writers_and_one_router_should_raise_signal_service_unavailable(self):
-        with StubCluster({9001: "router_no_writers_one_router.script"}):
-            address = ("127.0.0.1", 9001)
-            with RoutingConnectionPool(connector) as pool:
-                with self.assertRaises(ServiceUnavailable):
-                    _ = pool.fetch_routing_table(address)
-
-    def test_no_writers_and_multiple_routers_should_return_null_table(self):
+    def test_no_writers_should_return_null_table(self):
         with StubCluster({9001: "router_no_writers.script"}):
             address = ("127.0.0.1", 9001)
             with RoutingConnectionPool(connector) as pool: