Support Redis Sentinel database connections (#5196)

# Support Redis Sentinel database connections

This PR adds the support to connect not only to Redis standalone servers
but High Availability Replication sets too
(https://redis.io/docs/management/sentinel/)
Redis Replica Sets have on Master allowing to write data and 2+ replicas
with read-only access to the data. The additional Redis Sentinel
instances monitor all server and reconfigure the RW-Master on the fly if
it comes unavailable.

Therefore all connections must be made through the Sentinels the query
the current master for a read-write connection. This PR adds basic
support to also allow a redis connection url specifying a Sentinel as
Redis connection.

Redis documentation and Jupyter notebook with Redis examples are updated
to mention how to connect to a redis Replica Set with Sentinels

        - 

Remark - i did not found test cases for Redis server connections to add
new cases here. Therefor i tests the new utility class locally with
different kind of setups to make sure different connection urls are
working as expected. But no test case here as part of this PR.

docs/extras/ecosystem/integrations/redis.mdx

@@ -8,6 +8,36 @@ It is broken into two parts: installation and setup, and then references to spec
 
 ## Wrappers
 
+All wrappers needing a redis url connection string to connect to the database support either a stand alone Redis server
+or a High-Availability setup with Replication and Redis Sentinels.
+
+### Redis Standalone connection url
+For standalone Redis server the official redis connection url formats can be used as describe in the python redis modules
+"from_url()" method [Redis.from_url](https://redis-py.readthedocs.io/en/stable/connections.html#redis.Redis.from_url)
+
+Example: `redis_url = "redis://:secret-pass@localhost:6379/0"`
+
+### Redis Sentinel connection url
+
+For [Redis sentinel setups](https://redis.io/docs/management/sentinel/) the connection scheme is "redis+sentinel". 
+This is an un-offical extensions to the official IANA registered protocol schemes as long as there is no connection url
+for Sentinels available.
+
+Example: `redis_url = "redis+sentinel://:secret-pass@sentinel-host:26379/mymaster/0"`
+
+The format is  `redis+sentinel://[[username]:[password]]@[host-or-ip]:[port]/[service-name]/[db-number]`
+with the default values of "service-name = mymaster" and "db-number = 0" if not set explicit.
+The service-name is the redis server monitoring group name as configured within the Sentinel. 
+
+The current url format limits the connection string to one sentinel host only (no list can be given) and
+booth Redis server and sentinel must have the same password set (if used).
+
+### Redis Cluster connection url
+
+Redis cluster is not supported right now for all methods requiring a "redis_url" parameter.
+The only way to use a Redis Cluster is with LangChain classes accepting a preconfigured Redis client like `RedisCache`
+(example below).
+
 ### Cache
 
 The Cache wrapper allows for [Redis](https://redis.io) to be used as a remote, low-latency, in-memory cache for LLM prompts and responses.

docs/extras/modules/data_connection/vectorstores/integrations/redis.ipynb

@@ -8,7 +8,11 @@
     "\n",
     ">[Redis (Remote Dictionary Server)](https://en.wikipedia.org/wiki/Redis) is an in-memory data structure store, used as a distributed, in-memory key–value database, cache and message broker, with optional durability.\n",
     "\n",
-    "This notebook shows how to use functionality related to the [Redis vector database](https://redis.com/solutions/use-cases/vector-database/)."
+    "This notebook shows how to use functionality related to the [Redis vector database](https://redis.com/solutions/use-cases/vector-database/).\n",
+    "\n",
+    "As database either Redis standalone server or Redis Sentinel HA setups are supported for connections with the \"redis_url\"\n",
+    "parameter. More information about the different formats of the redis connection url can be found in the LangChain\n",
+    "[Redis Readme](../../../../integrations/redis.md) file"
    ]
   },
   {
@@ -258,6 +262,52 @@
    "source": [
     "Redis.delete(keys, redis_url=\"redis://localhost:6379\")"
    ]
+  },
+  {
+   "cell_type": "markdown",
+   "source": [
+    "### Redis connection Url examples\n",
+    "\n",
+    "Valid Redis Url scheme are:\n",
+    "1. `redis://`  - Connection to Redis standalone, unencrypted\n",
+    "2. `rediss://` - Connection to Redis standalone, with TLS encryption\n",
+    "3. `redis+sentinel://`  - Connection to Redis server via Redis Sentinel, unencrypted\n",
+    "4. `rediss+sentinel://` - Connection to Redis server via Redis Sentinel, booth connections with TLS encryption\n",
+    "\n",
+    "More information about additional connection parameter can be found in the redis-py documentation at https://redis-py.readthedocs.io/en/stable/connections.html"
+   ],
+   "metadata": {
+    "collapsed": false
+   }
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "outputs": [],
+   "source": [
+    "# connection to redis standalone at localhost, db 0, no password\n",
+    "redis_url=\"redis://localhost:6379\"\n",
+    "# connection to host \"redis\" port 7379 with db 2 and password \"secret\" (old style authentication scheme without username / pre 6.x)\n",
+    "redis_url=\"redis://:secret@redis:7379/2\"\n",
+    "# connection to host redis on default port with user \"joe\", pass \"secret\" using redis version 6+ ACLs\n",
+    "redis_url=\"redis://joe:secret@redis/0\"\n",
+    "\n",
+    "# connection to sentinel at localhost with default group mymaster and db 0, no password\n",
+    "redis_url=\"redis+sentinel://localhost:26379\"\n",
+    "# connection to sentinel at host redis with default port 26379 and user \"joe\" with password \"secret\" with default group mymaster and db 0\n",
+    "redis_url=\"redis+sentinel://joe:secret@redis\"\n",
+    "# connection to sentinel, no auth with sentinel monitoring group \"zone-1\" and database 2\n",
+    "redis_url=\"redis+sentinel://redis:26379/zone-1/2\"\n",
+    "\n",
+    "# connection to redis standalone at localhost, db 0, no password but with TLS support\n",
+    "redis_url=\"rediss://localhost:6379\"\n",
+    "# connection to redis sentinel at localhost and default port, db 0, no password\n",
+    "# but with TLS support for booth Sentinel and Redis server\n",
+    "redis_url=\"rediss+sentinel://localhost\"\n"
+   ],
+   "metadata": {
+    "collapsed": false
+   }
   }
  ],
  "metadata": {