Make DNS error retryable (#1211)

Configuring the driver with a URL that cannot be DNS resolved will raise a
(retryable) `ServiceUnavailable` error instead of a `ValueError`.

Co-authored-by: MaxAake <61233757+MaxAake@users.noreply.github.com>

Author: robsdedude

CHANGELOG.md

@@ -165,6 +165,8 @@ See also https://github.com/neo4j/neo4j-python-driver/wiki for a full changelog.
   - `neo4j.graph.Node`, `neo4j.graph.Relationship`, `neo4j.graph.Path`
   - `neo4j.time.Date`, `neo4j.time.Time`, `neo4j.time.DateTime`
   - `neo4j.spatial.Point` (and subclasses)
+- Configuring the driver with a URL that cannot be DNS resolved will raise a (retryable) `ServiceUnavailable` error
+  instead of a `ValueError`.
 - Separate out log entries that are session-related (including transaction retries)
   form sub-logger `neo4j.pool` to a new sub-logger `neo4j.session`.
 - Notifications:

src/neo4j/_async_compat/network/_util.py

@@ -22,6 +22,7 @@
     Address,
     ResolvedAddress,
 )
+from ...exceptions import ServiceUnavailable
 from ..util import AsyncUtil
 
 
@@ -40,6 +41,14 @@ def _resolved_addresses_from_info(info, host_name):
             yield ResolvedAddress(addr, host_name=host_name)
 
 
+_RETRYABLE_DNS_ERRNOS = {
+    socket.EAI_ADDRFAMILY,
+    socket.EAI_AGAIN,
+    socket.EAI_MEMORY,
+    socket.EAI_NODATA,
+}
+
+
 class AsyncNetworkUtil:
     @staticmethod
     async def get_address_info(
@@ -69,7 +78,16 @@ async def _dns_resolver(address, family=0):
                 type=socket.SOCK_STREAM,
             )
         except OSError as e:
-            raise ValueError(f"Cannot resolve address {address}") from e
+            if e.errno in _RETRYABLE_DNS_ERRNOS or (
+                e.errno == socket.EAI_NONAME
+                and (address.host is not None or address.port is not None)
+            ):
+                raise ServiceUnavailable(
+                    f"Failed to DNS resolve address {address}: {e}"
+                ) from e
+            raise ValueError(
+                f"Failed to DNS resolve address {address}: {e}"
+            ) from e
         return list(_resolved_addresses_from_info(info, address._host_name))
 
     @staticmethod
@@ -151,7 +169,16 @@ def _dns_resolver(address, family=0):
                 type=socket.SOCK_STREAM,
             )
         except OSError as e:
-            raise ValueError(f"Cannot resolve address {address}") from e
+            if e.errno in _RETRYABLE_DNS_ERRNOS or (
+                e.errno == socket.EAI_NONAME
+                and (address.host is not None or address.port is not None)
+            ):
+                raise ServiceUnavailable(
+                    f"Failed to DNS resolve address {address}: {e}"
+                ) from e
+            raise ValueError(
+                f"Failed to DNS resolve address {address}: {e}"
+            ) from e
         return _resolved_addresses_from_info(info, address._host_name)
 
     @staticmethod

tests/integration/async_/async_compat/__init__.py

@@ -0,0 +1,14 @@
+# Copyright (c) "Neo4j"
+# Neo4j Sweden AB [https://neo4j.com]
+#
+# 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
+#
+#     https://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.

tests/integration/async_/async_compat/network/__init__.py

@@ -0,0 +1,14 @@
+# Copyright (c) "Neo4j"
+# Neo4j Sweden AB [https://neo4j.com]
+#
+# 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
+#
+#     https://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.

tests/integration/async_/async_compat/network/test_util.py

@@ -0,0 +1,64 @@
+# Copyright (c) "Neo4j"
+# Neo4j Sweden AB [https://neo4j.com]
+#
+# 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
+#
+#     https://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 __future__ import annotations
+
+import socket
+
+import pytest
+
+from neo4j._addressing import (
+    ResolvedAddress,
+    ResolvedIPv4Address,
+    ResolvedIPv6Address,
+)
+from neo4j._async_compat.network import AsyncNetworkUtil
+from neo4j.addressing import Address
+from neo4j.exceptions import ServiceUnavailable
+
+from ....._async_compat import mark_async_test
+
+
+@mark_async_test
+async def test_resolve_address():
+    resolved = [
+        addr
+        async for addr in AsyncNetworkUtil.resolve_address(
+            Address(("localhost", 1234)),
+        )
+    ]
+    assert all(isinstance(addr, ResolvedAddress) for addr in resolved)
+    for addr in resolved:
+        if isinstance(addr, ResolvedIPv4Address):
+            assert len(addr) == 2
+            assert addr[0].startswith("127.0.0.")
+            assert addr[1] == 1234
+        elif isinstance(addr, ResolvedIPv6Address):
+            assert len(addr) == 4
+            assert addr[:2] == ("::1", 1234)
+
+
+@mark_async_test
+async def test_resolve_invalid_address():
+    with pytest.raises(ServiceUnavailable) as exc:
+        await anext(
+            AsyncNetworkUtil.resolve_address(
+                Address(("example.invalid", 1234)),
+            )
+        )
+    cause = exc.value.__cause__
+    assert isinstance(cause, socket.gaierror)
+    assert cause.errno, socket.EAI_NONAME

tests/integration/sync/async_compat/__init__.py

@@ -24,6 +24,7 @@
 )
 from neo4j._async_compat.network import AsyncNetworkUtil
 from neo4j._async_compat.util import AsyncUtil
+from neo4j.exceptions import ServiceUnavailable
 
 from ..._async_compat import mark_async_test
 
@@ -53,14 +54,19 @@ async def test_address_resolve_with_custom_resolver_none() -> None:
 @pytest.mark.parametrize(
     ("test_input", "expected"),
     [
+        (Address(("example.invalid", "7687")), ServiceUnavailable),
+        (Address(("example.invalid", 7687)), ServiceUnavailable),
         (Address(("127.0.0.1", "abcd")), ValueError),
         (Address((None, None)), ValueError),
+        (Address((1234, "7687")), TypeError),
     ],
 )
 @mark_async_test
 async def test_address_resolve_with_unresolvable_address(
     test_input, expected
 ) -> None:
+    # import contextlib
+    # with contextlib.suppress(Exception):
     with pytest.raises(expected):
         await AsyncUtil.list(
             AsyncNetworkUtil.resolve_address(test_input, resolver=None)