fix redis cache chat model (#8041)

Redis cache currently stores model outputs as strings. Chat generations
have Messages which contain more information than just a string. Until
Redis cache supports fully storing messages, cache should not interact
with chat generations.

langchain/cache.py

@@ -5,6 +5,7 @@ import hashlib
 import inspect
 import json
 import logging
+import warnings
 from abc import ABC, abstractmethod
 from datetime import timedelta
 from typing import (
@@ -34,7 +35,7 @@ except ImportError:
 from langchain.embeddings.base import Embeddings
 from langchain.load.dump import dumps
 from langchain.load.load import loads
-from langchain.schema import Generation
+from langchain.schema import ChatGeneration, Generation
 from langchain.vectorstores.redis import Redis as RedisVectorstore
 
 logger = logging.getLogger(__file__)
@@ -232,6 +233,12 @@ class RedisCache(BaseCache):
                     "RedisCache only supports caching of normal LLM generations, "
                     f"got {type(gen)}"
                 )
+            if isinstance(gen, ChatGeneration):
+                warnings.warn(
+                    "NOTE: Generation has not been cached. RedisCache does not"
+                    " support caching ChatModel outputs."
+                )
+                return
         # Write to a Redis HASH
         key = self._key(prompt, llm_string)
         self.redis.hset(
@@ -345,6 +352,12 @@ class RedisSemanticCache(BaseCache):
                     "RedisSemanticCache only supports caching of "
                     f"normal LLM generations, got {type(gen)}"
                 )
+            if isinstance(gen, ChatGeneration):
+                warnings.warn(
+                    "NOTE: Generation has not been cached. RedisSentimentCache does not"
+                    " support caching ChatModel outputs."
+                )
+                return
         llm_cache = self._get_llm_cache(llm_string)
         # Write to vectorstore
         metadata = {

tests/integration_tests/cache/test_redis_cache.py

@@ -1,10 +1,12 @@
 """Test Redis cache functionality."""
+import pytest
 import redis
 
 import langchain
 from langchain.cache import RedisCache, RedisSemanticCache
 from langchain.schema import Generation, LLMResult
 from tests.integration_tests.vectorstores.fake_embeddings import FakeEmbeddings
+from tests.unit_tests.llms.fake_chat_model import FakeChatModel
 from tests.unit_tests.llms.fake_llm import FakeLLM
 
 REDIS_TEST_URL = "redis://localhost:6379"
@@ -28,6 +30,17 @@ def test_redis_cache() -> None:
     langchain.llm_cache.redis.flushall()
 
 
+def test_redis_cache_chat() -> None:
+    langchain.llm_cache = RedisCache(redis_=redis.Redis.from_url(REDIS_TEST_URL))
+    llm = FakeChatModel()
+    params = llm.dict()
+    params["stop"] = None
+    with pytest.warns():
+        llm.predict("foo")
+    llm.predict("foo")
+    langchain.llm_cache.redis.flushall()
+
+
 def test_redis_semantic_cache() -> None:
     langchain.llm_cache = RedisSemanticCache(
         embedding=FakeEmbeddings(), redis_url=REDIS_TEST_URL, score_threshold=0.1
@@ -53,3 +66,14 @@ def test_redis_semantic_cache() -> None:
     # expect different output now without cached result
     assert output != expected_output
     langchain.llm_cache.clear(llm_string=llm_string)
+
+
+def test_redis_semantic_cache_chat() -> None:
+    langchain.llm_cache = RedisCache(redis_=redis.Redis.from_url(REDIS_TEST_URL))
+    llm = FakeChatModel()
+    params = llm.dict()
+    params["stop"] = None
+    with pytest.warns():
+        llm.predict("foo")
+    llm.predict("foo")
+    langchain.llm_cache.redis.flushall()