allow getting recoverable_connection_errors without an active transport (#1471)

* allow getting recoverable_connection_errors without an active transport

* move redis transport errors to class

* move consul transport errors to class

* move etcd transport errors to class

* remove redis.Transport._get_errors and references in tests

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* fix flake8 errors

* add integration test for redis ConnectionError

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

7 files changed, 135 insertions, 37 deletions

diff --git a/kombu/connection.py b/kombu/connection.py
index e4558e92..4b2cbd62 100644
--- a/kombu/connection.py
+++ b/kombu/connection.py
@@ -932,7 +932,7 @@ class Connection:
         but where the connection must be closed and re-established first.
         """
         try:
-            return self.transport.recoverable_connection_errors
+            return self.get_transport_cls().recoverable_connection_errors
         except AttributeError:
             # There were no such classification before,
             # and all errors were assumed to be recoverable,
@@ -948,19 +948,19 @@ class Connection:
         recovered from without re-establishing the connection.
         """
         try:
-            return self.transport.recoverable_channel_errors
+            return self.get_transport_cls().recoverable_channel_errors
         except AttributeError:
             return ()
 
     @cached_property
     def connection_errors(self):
         """List of exceptions that may be raised by the connection."""
-        return self.transport.connection_errors
+        return self.get_transport_cls().connection_errors
 
     @cached_property
     def channel_errors(self):
         """List of exceptions that may be raised by the channel."""
-        return self.transport.channel_errors
+        return self.get_transport_cls().channel_errors
 
     @property
     def supports_heartbeats(self):
diff --git a/kombu/transport/consul.py b/kombu/transport/consul.py
index ea275c95..4369b1f8 100644
--- a/kombu/transport/consul.py
+++ b/kombu/transport/consul.py
@@ -276,24 +276,25 @@ class Transport(virtual.Transport):
     driver_type = 'consul'
     driver_name = 'consul'
 
-    def __init__(self, *args, **kwargs):
-        if consul is None:
-            raise ImportError('Missing python-consul library')
-
-        super().__init__(*args, **kwargs)
-
-        self.connection_errors = (
+    if consul:
+        connection_errors = (
             virtual.Transport.connection_errors + (
                 consul.ConsulException, consul.base.ConsulException
             )
         )
 
-        self.channel_errors = (
+        channel_errors = (
             virtual.Transport.channel_errors + (
                 consul.ConsulException, consul.base.ConsulException
             )
         )
 
+    def __init__(self, *args, **kwargs):
+        if consul is None:
+            raise ImportError('Missing python-consul library')
+
+        super().__init__(*args, **kwargs)
+
     def verify_connection(self, connection):
         port = connection.client.port or self.default_port
         host = connection.client.hostname or DEFAULT_HOST
diff --git a/kombu/transport/etcd.py b/kombu/transport/etcd.py
index 4d0b0364..ba9e4150 100644
--- a/kombu/transport/etcd.py
+++ b/kombu/transport/etcd.py
@@ -242,6 +242,15 @@ class Transport(virtual.Transport):
     implements = virtual.Transport.implements.extend(
         exchange_type=frozenset(['direct']))
 
+    if etcd:
+        connection_errors = (
+            virtual.Transport.connection_errors + (etcd.EtcdException, )
+        )
+
+        channel_errors = (
+            virtual.Transport.channel_errors + (etcd.EtcdException, )
+        )
+
     def __init__(self, *args, **kwargs):
         """Create a new instance of etcd.Transport."""
         if etcd is None:
@@ -249,14 +258,6 @@ class Transport(virtual.Transport):
 
         super().__init__(*args, **kwargs)
 
-        self.connection_errors = (
-            virtual.Transport.connection_errors + (etcd.EtcdException, )
-        )
-
-        self.channel_errors = (
-            virtual.Transport.channel_errors + (etcd.EtcdException, )
-        )
-
     def verify_connection(self, connection):
         """Verify the connection works."""
         port = connection.client.port or self.default_port
diff --git a/kombu/transport/redis.py b/kombu/transport/redis.py
index 090b411d..45558641 100644
--- a/kombu/transport/redis.py
+++ b/kombu/transport/redis.py
@@ -1214,13 +1214,14 @@ class Transport(virtual.Transport):
         exchange_type=frozenset(['direct', 'topic', 'fanout'])
     )
 
+    if redis:
+        connection_errors, channel_errors = get_redis_error_classes()
+
     def __init__(self, *args, **kwargs):
         if redis is None:
             raise ImportError('Missing redis library (pip install redis)')
         super().__init__(*args, **kwargs)
 
-        # Get redis-py exceptions.
-        self.connection_errors, self.channel_errors = self._get_errors()
         # All channels share the same poller.
         self.cycle = MultiChannelPoller()
 
@@ -1265,10 +1266,6 @@ class Transport(virtual.Transport):
         """Handle AIO event for one of our file descriptors."""
         self.cycle.on_readable(fileno)
 
-    def _get_errors(self):
-        """Utility to import redis-py's exceptions at runtime."""
-        return get_redis_error_classes()
-
 
 if sentinel:
     class SentinelManagedSSLConnection(
diff --git a/t/integration/test_redis.py b/t/integration/test_redis.py
index 5647bf06..522adf8e 100644
--- a/t/integration/test_redis.py
+++ b/t/integration/test_redis.py
@@ -5,6 +5,7 @@ import pytest
 import redis
 
 import kombu
+from kombu.transport.redis import Transport
 
 from .common import (BaseExchangeTypes, BaseMessage, BasePriority,
                      BasicFunctionality)
@@ -56,7 +57,11 @@ def test_failed_credentials():
 @pytest.mark.env('redis')
 @pytest.mark.flaky(reruns=5, reruns_delay=2)
 class test_RedisBasicFunctionality(BasicFunctionality):
-    pass
+    def test_failed_connection__ConnectionError(self, invalid_connection):
+        # method raises transport exception
+        with pytest.raises(redis.exceptions.ConnectionError) as ex:
+            invalid_connection.connection
+        assert ex.type in Transport.connection_errors
 
 
 @pytest.mark.env('redis')
diff --git a/t/unit/test_connection.py b/t/unit/test_connection.py
index 83f233cf..b65416e8 100644
--- a/t/unit/test_connection.py
+++ b/t/unit/test_connection.py
@@ -293,7 +293,9 @@ class test_Connection:
         assert not c.is_evented
 
     def test_register_with_event_loop(self):
-        c = Connection(transport=Mock)
+        transport = Mock(name='transport')
+        transport.connection_errors = []
+        c = Connection(transport=transport)
         loop = Mock(name='loop')
         c.register_with_event_loop(loop)
         c.transport.register_with_event_loop.assert_called_with(
@@ -477,7 +479,7 @@ class test_Connection:
         def publish():
             raise _ConnectionError('failed connection')
 
-        self.conn.transport.connection_errors = (_ConnectionError,)
+        self.conn.get_transport_cls().connection_errors = (_ConnectionError,)
         ensured = self.conn.ensure(self.conn, publish)
         with pytest.raises(OperationalError):
             ensured()
@@ -485,7 +487,7 @@ class test_Connection:
     def test_autoretry(self):
         myfun = Mock()
 
-        self.conn.transport.connection_errors = (KeyError,)
+        self.conn.get_transport_cls().connection_errors = (KeyError,)
 
         def on_call(*args, **kwargs):
             myfun.side_effect = None
@@ -571,6 +573,18 @@ class test_Connection:
         conn = Connection(transport=MyTransport)
         assert conn.channel_errors == (KeyError, ValueError)
 
+    def test_channel_errors__exception_no_cache(self):
+        """Ensure the channel_errors can be retrieved without an initialized
+        transport.
+        """
+
+        class MyTransport(Transport):
+            channel_errors = (KeyError,)
+
+        conn = Connection(transport=MyTransport)
+        MyTransport.__init__ = Mock(side_effect=Exception)
+        assert conn.channel_errors == (KeyError,)
+
     def test_connection_errors(self):
 
         class MyTransport(Transport):
@@ -579,6 +593,80 @@ class test_Connection:
         conn = Connection(transport=MyTransport)
         assert conn.connection_errors == (KeyError, ValueError)
 
+    def test_connection_errors__exception_no_cache(self):
+        """Ensure the connection_errors can be retrieved without an
+        initialized transport.
+        """
+
+        class MyTransport(Transport):
+            connection_errors = (KeyError,)
+
+        conn = Connection(transport=MyTransport)
+        MyTransport.__init__ = Mock(side_effect=Exception)
+        assert conn.connection_errors == (KeyError,)
+
+    def test_recoverable_connection_errors(self):
+
+        class MyTransport(Transport):
+            recoverable_connection_errors = (KeyError, ValueError)
+
+        conn = Connection(transport=MyTransport)
+        assert conn.recoverable_connection_errors == (KeyError, ValueError)
+
+    def test_recoverable_connection_errors__fallback(self):
+        """Ensure missing recoverable_connection_errors on the Transport does
+        not cause a fatal error.
+        """
+
+        class MyTransport(Transport):
+            connection_errors = (KeyError,)
+            channel_errors = (ValueError,)
+
+        conn = Connection(transport=MyTransport)
+        assert conn.recoverable_connection_errors == (KeyError, ValueError)
+
+    def test_recoverable_connection_errors__exception_no_cache(self):
+        """Ensure the recoverable_connection_errors can be retrieved without
+        an initialized transport.
+        """
+
+        class MyTransport(Transport):
+            recoverable_connection_errors = (KeyError,)
+
+        conn = Connection(transport=MyTransport)
+        MyTransport.__init__ = Mock(side_effect=Exception)
+        assert conn.recoverable_connection_errors == (KeyError,)
+
+    def test_recoverable_channel_errors(self):
+
+        class MyTransport(Transport):
+            recoverable_channel_errors = (KeyError, ValueError)
+
+        conn = Connection(transport=MyTransport)
+        assert conn.recoverable_channel_errors == (KeyError, ValueError)
+
+    def test_recoverable_channel_errors__fallback(self):
+        """Ensure missing recoverable_channel_errors on the Transport does not
+        cause a fatal error.
+        """
+
+        class MyTransport(Transport):
+            pass
+
+        conn = Connection(transport=MyTransport)
+        assert conn.recoverable_channel_errors == ()
+
+    def test_recoverable_channel_errors__exception_no_cache(self):
+        """Ensure the recoverable_channel_errors can be retrieved without an
+        initialized transport.
+        """
+        class MyTransport(Transport):
+            recoverable_channel_errors = (KeyError,)
+
+        conn = Connection(transport=MyTransport)
+        MyTransport.__init__ = Mock(side_effect=Exception)
+        assert conn.recoverable_channel_errors == (KeyError,)
+
     def test_multiple_urls_hostname(self):
         conn = Connection(['example.com;amqp://example.com'])
         assert conn.as_uri() == 'amqp://guest:**@example.com:5672//'
diff --git a/t/unit/transport/test_redis.py b/t/unit/transport/test_redis.py
index 1daaf738..7046cf7b 100644
--- a/t/unit/transport/test_redis.py
+++ b/t/unit/transport/test_redis.py
@@ -269,9 +269,8 @@ class Channel(redis.Channel):
 
 class Transport(redis.Transport):
     Channel = Channel
-
-    def _get_errors(self):
-        return ((KeyError,), (IndexError,))
+    connection_errors = (KeyError,)
+    channel_errors = (IndexError,)
 
 
 class test_Channel:
@@ -907,15 +906,22 @@ class test_Channel:
         redis.Transport.on_readable(transport, 13)
         cycle.on_readable.assert_called_with(13)
 
-    def test_transport_get_errors(self):
-        assert redis.Transport._get_errors(self.connection.transport)
+    def test_transport_connection_errors(self):
+        """Ensure connection_errors are populated."""
+        assert redis.Transport.connection_errors
+
+    def test_transport_channel_errors(self):
+        """Ensure connection_errors are populated."""
+        assert redis.Transport.channel_errors
 
     def test_transport_driver_version(self):
         assert redis.Transport.driver_version(self.connection.transport)
 
-    def test_transport_get_errors_when_InvalidData_used(self):
+    def test_transport_errors_when_InvalidData_used(self):
         from redis import exceptions
 
+        from kombu.transport.redis import get_redis_error_classes
+
         class ID(Exception):
             pass
 
@@ -924,7 +930,7 @@ class test_Channel:
         exceptions.InvalidData = ID
         exceptions.DataError = None
         try:
-            errors = redis.Transport._get_errors(self.connection.transport)
+            errors = get_redis_error_classes()
             assert errors
             assert ID in errors[1]
         finally: