Add Redis cache implementation (#397)

I'm using a hash function for the key just to make sure its length
doesn't get out of hand, otherwise the implementation is quite similar.

docs/examples/prompts/llm_caching.ipynb

@@ -60,8 +60,8 @@
      "name": "stdout",
      "output_type": "stream",
      "text": [
-      "CPU times: user 30 ms, sys: 10.8 ms, total: 40.8 ms\n",
-      "Wall time: 983 ms\n"
+      "CPU times: user 30.6 ms, sys: 9.95 ms, total: 40.5 ms\n",
+      "Wall time: 730 ms\n"
      ]
     },
     {
@@ -91,8 +91,8 @@
      "name": "stdout",
      "output_type": "stream",
      "text": [
-      "CPU times: user 65 µs, sys: 1 µs, total: 66 µs\n",
-      "Wall time: 70.1 µs\n"
+      "CPU times: user 71 µs, sys: 3 µs, total: 74 µs\n",
+      "Wall time: 78.9 µs\n"
      ]
     },
     {
@@ -142,8 +142,8 @@
      "name": "stdout",
      "output_type": "stream",
      "text": [
-      "CPU times: user 6.76 ms, sys: 2.6 ms, total: 9.36 ms\n",
-      "Wall time: 7.86 ms\n"
+      "CPU times: user 5.27 ms, sys: 2.36 ms, total: 7.63 ms\n",
+      "Wall time: 6.68 ms\n"
      ]
     },
     {
@@ -167,14 +167,16 @@
    "cell_type": "code",
    "execution_count": 8,
    "id": "5bf2f6fd",
-   "metadata": {},
+   "metadata": {
+    "scrolled": true
+   },
    "outputs": [
     {
      "name": "stdout",
      "output_type": "stream",
      "text": [
-      "CPU times: user 2.52 ms, sys: 1.47 ms, total: 3.99 ms\n",
-      "Wall time: 2.98 ms\n"
+      "CPU times: user 3.05 ms, sys: 1.1 ms, total: 4.16 ms\n",
+      "Wall time: 5.58 ms\n"
      ]
     },
     {
@@ -194,6 +196,90 @@
     "llm(\"Tell me a joke\")"
    ]
   },
+  {
+   "cell_type": "markdown",
+   "id": "278ad7ae",
+   "metadata": {},
+   "source": [
+    "### Redis Cache"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 9,
+   "id": "39f6eb0b",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "# We can do the same thing with a Redis cache\n",
+    "# (make sure your local Redis instance is running first before running this example)\n",
+    "from redis import Redis\n",
+    "from langchain.cache import RedisCache\n",
+    "langchain.llm_cache = RedisCache(redis_=Redis())"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 10,
+   "id": "28920749",
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "CPU times: user 6.75 ms, sys: 3.14 ms, total: 9.89 ms\n",
+      "Wall time: 716 ms\n"
+     ]
+    },
+    {
+     "data": {
+      "text/plain": [
+       "'\\n\\nWhy did the chicken cross the road?\\n\\nTo get to the other side!'"
+      ]
+     },
+     "execution_count": 10,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "%%time\n",
+    "# The first time, it is not yet in cache, so it should take longer\n",
+    "llm(\"Tell me a joke\")"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 11,
+   "id": "94bf9415",
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "CPU times: user 1.66 ms, sys: 1.92 ms, total: 3.57 ms\n",
+      "Wall time: 7.56 ms\n"
+     ]
+    },
+    {
+     "data": {
+      "text/plain": [
+       "'\\n\\nWhy did the chicken cross the road?\\n\\nTo get to the other side!'"
+      ]
+     },
+     "execution_count": 11,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "%%time\n",
+    "# The second time it is, so it goes faster\n",
+    "llm(\"Tell me a joke\")"
+   ]
+  },
   {
    "cell_type": "markdown",
    "id": "934943dc",
@@ -459,7 +545,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.10.8"
+   "version": "3.10.4"
   }
  },
  "nbformat": 4,