add connection_kwargs for plain redis

Added :paramref:`.RedisBackend.connection_kwargs` parameter, which is a
dictionary of additional keyword arguments that will be passed directly to
``StrictRedis()`` or ``StrictRedis.from_url()``, in the same way that this
parameter works with the :class:`.RedisSentinelBackend` already.

Thanks to Pim Beenes for assistance.

Closes: #221
Pull-request: https://github.com/sqlalchemy/dogpile.cache/pull/221
Pull-request-sha: 26c6cc97ad677d9df4e7387bbae861c15db395de

Change-Id: I0991a25ddf31a64d831d3b7e56b3cb9a41685260

3 files changed, 49 insertions, 11 deletions

diff --git a/docs/build/unreleased/221.rst b/docs/build/unreleased/221.rst
new file mode 100644
index 0000000..9211abf
--- /dev/null
+++ b/docs/build/unreleased/221.rst
@@ -0,0 +1,8 @@
+.. change::
+    :tags: usecase, redis
+    :tickets: 221
+
+    Added :paramref:`.RedisBackend.connection_kwargs` parameter, which is a
+    dictionary of additional keyword arguments that will be passed directly to
+    ``StrictRedis()`` or ``StrictRedis.from_url()``, in the same way that this
+    parameter works with the :class:`.RedisSentinelBackend` already.
diff --git a/dogpile/cache/backends/redis.py b/dogpile/cache/backends/redis.py
index cf646fe..1a6ba09 100644
--- a/dogpile/cache/backends/redis.py
+++ b/dogpile/cache/backends/redis.py
@@ -24,7 +24,7 @@ __all__ = ("RedisBackend", "RedisSentinelBackend")
 
 
 class RedisBackend(BytesBackend):
-    """A `Redis <http://redis.io/>`_ backend, using the
+    r"""A `Redis <http://redis.io/>`_ backend, using the
     `redis-py <http://pypi.python.org/pypi/redis/>`_ backend.
 
     Example configuration::
@@ -88,6 +88,14 @@ class RedisBackend(BytesBackend):
      asynchronous runners, as they run in a different thread than the one
      used to create the lock.
 
+    :param connection_kwargs: dict, additional keyword arguments are passed
+     along to the
+     ``StrictRedis.from_url()`` method or ``StrictRedis()`` constructor
+     directly, including parameters like ``ssl``, ``ssl_certfile``,
+     ``charset``, etc.
+
+     .. versionadded:: 1.1.6  Added ``connection_kwargs`` parameter.
+
     """
 
     def __init__(self, arguments):
@@ -98,12 +106,12 @@ class RedisBackend(BytesBackend):
         self.password = arguments.pop("password", None)
         self.port = arguments.pop("port", 6379)
         self.db = arguments.pop("db", 0)
-        self.distributed_lock = arguments.get("distributed_lock", False)
+        self.distributed_lock = arguments.pop("distributed_lock", False)
         self.socket_timeout = arguments.pop("socket_timeout", None)
-
-        self.lock_timeout = arguments.get("lock_timeout", None)
-        self.lock_sleep = arguments.get("lock_sleep", 0.1)
-        self.thread_local_lock = arguments.get("thread_local_lock", True)
+        self.lock_timeout = arguments.pop("lock_timeout", None)
+        self.lock_sleep = arguments.pop("lock_sleep", 0.1)
+        self.thread_local_lock = arguments.pop("thread_local_lock", True)
+        self.connection_kwargs = arguments.pop("connection_kwargs", {})
 
         if self.distributed_lock and self.thread_local_lock:
             warnings.warn(
@@ -112,7 +120,7 @@ class RedisBackend(BytesBackend):
             )
 
         self.redis_expiration_time = arguments.pop("redis_expiration_time", 0)
-        self.connection_pool = arguments.get("connection_pool", None)
+        self.connection_pool = arguments.pop("connection_pool", None)
         self._create_client()
 
     def _imports(self):
@@ -131,6 +139,7 @@ class RedisBackend(BytesBackend):
             self.reader_client = self.writer_client
         else:
             args = {}
+            args.update(self.connection_kwargs)
             if self.socket_timeout:
                 args["socket_timeout"] = self.socket_timeout
 
@@ -269,9 +278,11 @@ class RedisSentinelBackend(RedisBackend):
      a normal Redis connection can be specified here.
      Default is {}.
 
-    :param connection_kwargs: dict, are keyword arguments that will be used
-     when establishing a connection to a Redis server.
-     Default is {}.
+    :param connection_kwargs: dict, additional keyword arguments are passed
+     along to the
+     ``StrictRedis.from_url()`` method or ``StrictRedis()`` constructor
+     directly, including parameters like ``ssl``, ``ssl_certfile``,
+     ``charset``, etc.
 
     :param lock_sleep: integer, number of seconds to sleep when failed to
      acquire a lock.  This argument is only valid when
@@ -290,7 +301,6 @@ class RedisSentinelBackend(RedisBackend):
         self.sentinels = arguments.pop("sentinels", None)
         self.service_name = arguments.pop("service_name", "mymaster")
         self.sentinel_kwargs = arguments.pop("sentinel_kwargs", {})
-        self.connection_kwargs = arguments.pop("connection_kwargs", {})
 
         super().__init__(
             arguments={
diff --git a/tests/cache/test_redis_backend.py b/tests/cache/test_redis_backend.py
index 5bdadc3..284aa5e 100644
--- a/tests/cache/test_redis_backend.py
+++ b/tests/cache/test_redis_backend.py
@@ -195,3 +195,23 @@ class RedisConnectionTest(TestCase):
     def test_connect_with_url(self, MockStrictRedis):
         arguments = {"url": "redis://redis:password@127.0.0.1:6379/0"}
         self._test_helper(MockStrictRedis.from_url, arguments)
+
+    def test_extra_arbitrary_args(self, MockStrictRedis):
+        arguments = {
+            "url": "redis://redis:password@127.0.0.1:6379/0",
+            "connection_kwargs": {
+                "ssl": True,
+                "encoding": "utf-8",
+                "new_redis_arg": 50,
+            },
+        }
+        self._test_helper(
+            MockStrictRedis.from_url,
+            {
+                "url": "redis://redis:password@127.0.0.1:6379/0",
+                "ssl": True,
+                "encoding": "utf-8",
+                "new_redis_arg": 50,
+            },
+            arguments,
+        )