Add no-store, no-cache in Cache-Control headers

README.md

@@ -221,6 +221,12 @@ When using the Redis backend, please make sure you pass in a redis client that d
 
 [redis-decode]: https://redis-py.readthedocs.io/en/latest/examples/connection_examples.html#by-default-Redis-return-binary-responses,-to-decode-them-use-decode_responses=True
 
+## Notes on `Cache-Control` header
+The cache behavior can be controlled by the client by passing the `Cache-Control` request header. The behavior is described below: 
+- `no-cache`: doesn't use cache even if the value is present but stores the response in the cache.
+- `no-store`: can use cache if present but will not add/update to cache.
+- `no-cache,no-store`: i.e. both are passed, it will neither store nor use the cache. Will remove the `max-age` and `ETag` as well from the response header.
+
 ## Tests and coverage
 
 ```shell

fastapi_cache/decorator.py

@@ -11,6 +11,7 @@
     TypeVar,
     Union,
     cast,
+    Set,
 )
 
 if sys.version_info >= (3, 10):
@@ -81,7 +82,23 @@ def _uncacheable(request: Optional[Request]) -> bool:
         return False
     if request.method != "GET":
         return True
-    return request.headers.get("Cache-Control") == "no-store"
+    return False
+
+def _extract_cache_control_headers(request: Optional[Request]) -> Set[str]:
+    """Extracts Cache-Control header
+    1. Convert all header to lowercase to make it case insensitive
+    2. Split on comma (,)
+    3. Strip whitespaces
+    4. convert to all lower case
+
+    returns an empty set if header not set
+    """
+    if request is not None:
+        headers = {header_key.lower(): header_val for header_key, header_val in request.headers.items()}
+        cache_control_header = headers.get("cache-control", None)
+        if cache_control_header:
+            return set([cache_control_val.strip().lower() for cache_control_val in cache_control_header.split(",")])
+    return set()
 
 
 def cache(
@@ -161,6 +178,8 @@ async def ensure_async_func(*args: P.args, **kwargs: P.kwargs) -> R:
             key_builder = key_builder or FastAPICache.get_key_builder()
             backend = FastAPICache.get_backend()
             cache_status_header = FastAPICache.get_cache_status_header()
+            cache_control_headers = _extract_cache_control_headers(request=request)
+            response_headers = {"Cache-Control": cache_control_headers.copy()}
 
             cache_key = key_builder(
                 func,
@@ -174,21 +193,30 @@ async def ensure_async_func(*args: P.args, **kwargs: P.kwargs) -> R:
                 cache_key = await cache_key
             assert isinstance(cache_key, str)  # noqa: S101  # assertion is a type guard
 
+            ttl, cached = 0, None
             try:
-                ttl, cached = await backend.get_with_ttl(cache_key)
+                # no-cache: Assume cache is not present. i.e. treat it as a miss
+                if "no-cache" not in cache_control_headers:
+                    ttl, cached = await backend.get_with_ttl(cache_key)
+                    etag = f"W/{hash(cached)}"
+                    response_headers["Cache-Control"].add(f"max-age={ttl}")
+                    response_headers["Etag"] = {f"ETag={etag}"}
             except Exception:
                 logger.warning(
                     f"Error retrieving cache key '{cache_key}' from backend:",
                     exc_info=True,
                 )
-                ttl, cached = 0, None
 
             if cached is None  or (request is not None and request.headers.get("Cache-Control") == "no-cache") :  # cache miss
                 result = await ensure_async_func(*args, **kwargs)
                 to_cache = coder.encode(result)
 
                 try:
-                    await backend.set(cache_key, to_cache, expire)
+                    # no-store: do not store the value in cache
+                    if "no-store" not in cache_control_headers:
+                        await backend.set(cache_key, to_cache, expire)
+                        response_headers["Cache-Control"].add(f"max-age={expire}")
+                        response_headers["Etag"] = {f"W/{hash(to_cache)}"}
                 except Exception:
                     logger.warning(
                         f"Error setting cache key '{cache_key}' in backend:",
@@ -198,25 +226,22 @@ async def ensure_async_func(*args: P.args, **kwargs: P.kwargs) -> R:
                 if response:
                     response.headers.update(
                         {
-                            "Cache-Control": f"max-age={expire}",
-                            "ETag": f"W/{hash(to_cache)}",
+                            **{header_key: ",".join(sorted(header_val)) for header_key, header_val in response_headers.items()},
                             cache_status_header: "MISS",
                         }
                     )
 
             else:  # cache hit
                 if response:
-                    etag = f"W/{hash(cached)}"
                     response.headers.update(
                         {
-                            "Cache-Control": f"max-age={ttl}",
-                            "ETag": etag,
+                            **{header_key: ",".join(sorted(header_val)) for header_key, header_val in response_headers.items()},
                             cache_status_header: "HIT",
                         }
                     )
 
                     if_none_match = request and request.headers.get("if-none-match")
-                    if if_none_match == etag:
+                    if "Etag" in response_headers and if_none_match == response_headers["Etag"]:
                         response.status_code = HTTP_304_NOT_MODIFIED
                         return response
 

tests/test_decorator.py

@@ -135,3 +135,41 @@ def test_cache_control() -> None:
 
         response = client.get("/cached_put")
         assert response.json() == {"value": 2}
+
+def test_cache_control_header() -> None:
+    """Test no-cache, no-store cache control header"""
+    with TestClient(app) as client:
+        # forcing clear to start a clean cache
+        client.get("/clear")
+
+        # no-store, no-cache will always no use or store cache
+        response = client.get("/date", headers={"Cache-Control": "no-store,no-cache"})
+        assert response.headers.get("X-FastAPI-Cache") == "MISS"
+        assert response.headers.get("Cache-Control") == "no-cache,no-store"
+        assert response.headers.get("ETag") is None
+        assert pendulum.parse(response.json()) == pendulum.today()  # type: ignore[attr-defined]
+
+        # do it again to test cache without header
+        response = client.get("/date")
+        assert response.headers.get("X-FastAPI-Cache") == "MISS"
+        assert pendulum.parse(response.json()) == pendulum.today()  # type: ignore[attr-defined]
+
+        # do it again to test cache with no-store. Will not store this response but use the cache
+        response = client.get("/date", headers={"Cache-Control": "no-store"})
+        assert response.headers.get("X-FastAPI-Cache") == "HIT"
+        assert response.headers.get("Cache-Control") == "max-age=10,no-store"
+        assert pendulum.parse(response.json()) == pendulum.today()  # type: ignore[attr-defined]
+
+        # do it again to test cache with no-cache. Will not store use cache but store it
+        response = client.get("/date", headers={"Cache-Control": "no-cache"})
+        assert response.headers.get("X-FastAPI-Cache") == "MISS"
+        assert response.headers.get("Cache-Control") == "max-age=10,no-cache"
+        assert pendulum.parse(response.json()) == pendulum.today()  # type: ignore[attr-defined]
+
+        time.sleep(3)
+
+        # call with no headers now to use the value store in previous step
+        response = client.get("/date")
+        assert response.headers.get("X-FastAPI-Cache") == "HIT"
+        assert response.headers.get("Cache-Control") == "max-age=7"
+        assert pendulum.parse(response.json()) == pendulum.today()  # type: ignore[attr-defined]