module Network.Wai.Middleware.Cache.Redis (
redisBackend,
lookupETag
) where
import Control.Monad (void)
import Control.Monad.IO.Class (liftIO)
import qualified Control.Arrow as A (first)
import qualified Data.ByteString as B
import qualified Data.ByteString.Char8 as BS8
import Data.ByteString.Lazy (fromChunks)
import Data.CaseInsensitive (original, mk)
import qualified Data.Serialize as S
import Data.Conduit (ResourceT, runResourceT, resourceThrow, ($$), ($=),
Flush(..))
import qualified Data.Conduit.List as CL
import Data.Conduit.Blaze (builderToByteStringFlush)
import qualified Crypto.Hash.SHA1 as SHA
import Data.Hex (hex)
import Network.Wai (Request(..), Response(..), responseSource, responseLBS)
import Network.Wai.Middleware.Cache (CacheBackend, CacheBackendError(..))
import Network.HTTP.Types (Status(..))
import qualified Database.Redis as R
import Database.Redis.Pile (pile)
import Control.Monad.Trans.Class (lift)
redisBackend ::
R.ConnectInfo
-> Integer
-> B.ByteString
-> (Request -> Maybe Integer)
-> (Request -> [B.ByteString])
-> (Request -> B.ByteString)
-> (Request -> Maybe B.ByteString)
-> CacheBackend
redisBackend cInfo db cachePrefix ttlFn tagsFn keyFn eTagFn app req = do
rawRes <- liftIO $ do
conn <- R.connect cInfo
R.runRedis conn $ do
void $ R.select db
pile cachePrefix key eTag (Just "response") $ runResourceT $ do
res <- app req
case res of
(ResponseFile _ _ fp part) -> lift $
resourceThrow $ CacheBackendError $ BS8.pack $
"Can't cache files : " ++ fp ++ ":" ++ show part
_ -> do
d <- parseResponse res
return (d, ttl, tags)
case buildResponse rawRes of
Left e -> lift $ resourceThrow $ CacheBackendError e
Right r -> return r
where
(ttl, tags, key) = (ttlFn req, tagsFn req, keyFn req)
eTag = case eTagFn req of
Nothing -> Nothing
Just v -> Just ("header:ETag", v)
lookupETag :: Request -> Maybe B.ByteString
lookupETag = lookup "If-None-Match" . requestHeaders
buildResponse :: Maybe [(B.ByteString, B.ByteString)]
-> Either B.ByteString (Maybe Response)
buildResponse Nothing = Right Nothing
buildResponse (Just raw) = decodeResp raw
where
decodeResp (("response", rawResp):[]) = case S.decode rawResp of
Left sm' -> Left $ BS8.pack sm'
Right (sc', sm', hs', bodyChunks) -> Right $ Just $
responseLBS (Status sc' sm')
(map (A.first mk) hs')
$ fromChunks bodyChunks
decodeResp _ = Left "Data error"
parseResponse :: Response -> ResourceT IO [(B.ByteString, B.ByteString)]
parseResponse res = do
bodyChunks <- b $= builderToByteStringFlush
$= CL.map fromChunk $$ CL.consume
let bodyHash = hex . SHA.finalize . foldl SHA.update SHA.init $ bodyChunks
return [("response",
S.encode (sc, sm, map
(A.first original) (("ETag", bodyHash):hs),
bodyChunks)),
("header:ETag", bodyHash)]
where
(Status sc sm, hs, b) = responseSource res
fromChunk (Chunk a) = a
fromChunk Flush = ""