[4.4] Fix pool closing connections too aggressively (#1038)

Whenever a new routing table was fetched, the pool would close all connections
to servers that were not part of the routing table. However, it might well be,
that a missing server is present still in the routing table for another
database. Hence, the pool now checks the routing tables for all databases before
deciding which connections are no longer needed.g

neo4j/io/__init__.py

@@ -1235,7 +1235,13 @@ def update_routing_table(self, *, database, imp_user, bookmarks,
             raise ServiceUnavailable("Unable to retrieve routing information")
 
     def update_connection_pool(self, *, database):
-        servers = self.get_or_create_routing_table(database).servers()
+        with self.refresh_lock:
+            routing_tables = [self.get_or_create_routing_table(database)]
+            for db in self.routing_tables.keys():
+                if db == database:
+                    continue
+                routing_tables.append(self.routing_tables[db])
+        servers = set.union(*(rt.servers() for rt in routing_tables))
         for address in list(self.connections):
             if address.unresolved not in servers:
                 super(Neo4jPool, self).deactivate(address)

tests/unit/conftest.py

@@ -0,0 +1,19 @@
+# Copyright (c) "Neo4j"
+# Neo4j Sweden AB [http://neo4j.com]
+#
+# This file is part of Neo4j.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# 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 .fixtures import *  # necessary for pytest to discover the fixtures

tests/unit/fixtures/__init__.py

@@ -0,0 +1,19 @@
+# Copyright (c) "Neo4j"
+# Neo4j Sweden AB [http://neo4j.com]
+#
+# This file is part of Neo4j.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# 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 ._fake_connection import *

tests/unit/fixtures/_fake_connection.py

@@ -0,0 +1,122 @@
+# Copyright (c) "Neo4j"
+# Neo4j Sweden AB [http://neo4j.com]
+#
+# This file is part of Neo4j.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# 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.
+
+
+import inspect
+
+import pytest
+
+from neo4j import ServerInfo
+from neo4j._deadline import Deadline
+
+
+__all__ = [
+    "fake_connection",
+    "fake_connection_generator",
+]
+
+
+@pytest.fixture
+def fake_connection_generator(session_mocker):
+    mock = session_mocker.mock_module
+
+    class FakeConnection(mock.NonCallableMagicMock):
+        callbacks = []
+        server_info = ServerInfo("127.0.0.1", (4, 3))
+        local_port = 1234
+        bolt_patches = set()
+
+        def __init__(self, *args, **kwargs):
+            super().__init__(*args, **kwargs)
+            self.attach_mock(mock.Mock(return_value=True), "is_reset_mock")
+            self.attach_mock(mock.Mock(return_value=False), "defunct")
+            self.attach_mock(mock.Mock(return_value=False), "stale")
+            self.attach_mock(mock.Mock(return_value=False), "closed")
+            self.attach_mock(mock.Mock(return_value=False), "socket")
+            self.socket.attach_mock(
+                mock.Mock(return_value=None), "get_deadline"
+            )
+
+            def set_deadline_side_effect(deadline):
+                deadline = Deadline.from_timeout_or_deadline(deadline)
+                self.socket.get_deadline.return_value = deadline
+
+            self.socket.attach_mock(
+                mock.Mock(side_effect=set_deadline_side_effect), "set_deadline"
+            )
+
+            def close_side_effect():
+                self.closed.return_value = True
+
+            self.attach_mock(mock.Mock(side_effect=close_side_effect), "close")
+
+        @property
+        def is_reset(self):
+            if self.closed.return_value or self.defunct.return_value:
+                raise AssertionError("is_reset should not be called on a closed or "
+                                     "defunct connection.")
+            return self.is_reset_mock()
+
+        def fetch_message(self, *args, **kwargs):
+            if self.callbacks:
+                cb = self.callbacks.pop(0)
+                cb()
+            return super().__getattr__("fetch_message")(*args, **kwargs)
+
+        def fetch_all(self, *args, **kwargs):
+            while self.callbacks:
+                cb = self.callbacks.pop(0)
+                cb()
+            return super().__getattr__("fetch_all")(*args, **kwargs)
+
+        def __getattr__(self, name):
+            parent = super()
+
+            def build_message_handler(name):
+                def func(*args, **kwargs):
+                    def callback():
+                        for cb_name, param_count in (
+                            ("on_success", 1),
+                            ("on_summary", 0)
+                        ):
+                            cb = kwargs.get(cb_name, None)
+                            if callable(cb):
+                                try:
+                                    param_count = \
+                                        len(inspect.signature(cb).parameters)
+                                except ValueError:
+                                    # e.g. built-in method as cb
+                                    pass
+                                if param_count == 1:
+                                    cb({})
+                                else:
+                                    cb()
+                    self.callbacks.append(callback)
+
+                return func
+
+            method_mock = parent.__getattr__(name)
+            if name in ("run", "commit", "pull", "rollback", "discard"):
+                method_mock.side_effect = build_message_handler(name)
+            return method_mock
+
+    return FakeConnection
+
+
+@pytest.fixture
+def fake_connection(fake_connection_generator):
+    return fake_connection_generator()

tests/unit/io/test__common.py

@@ -25,8 +25,6 @@
     ResetResponse,
 )
 
-from ..work import fake_connection
-
 
 @pytest.mark.parametrize(("chunk_size", "data", "result"), (
     (