Log and return 500 when handler flag persistence fails

src/HttpServer.hs

@@ -11,7 +11,7 @@ import Servant.API ((:>), Capture, Get, QueryParam, (:-), MimeRender (..), Accep
 import Data.ByteString (ByteString)
 import GHC.Generics (Generic)
 import Servant (Handler, err404)
-import Control.Monad.Catch (throwM, MonadCatch, MonadThrow)
+import Control.Monad.Catch (throwM, catch, MonadCatch, MonadThrow, SomeException)
 import Servant.Server (err500, ServerT)
 import Data.Maybe (fromMaybe)
 import Data.Map.Strict (Map)
@@ -49,7 +49,9 @@ putFlagHandler :: Flags -> Text -> Bool -> LoggingHandler (Map Text Bool)
 putFlagHandler flags name val
   | name `S.notMember` validNames flags = throwM err404
   | otherwise = do
-      setEnabled flags name val
+      setEnabled flags name val `catch` \e -> do
+        logFM ErrorS (ls ("failed to persist handler flag: " <> show (e :: SomeException)))
+        throwM err500
       allFlags flags