fix: log on LISTEN notification

src/PostgREST/AppState.hs

@@ -1,4 +1,5 @@
 {-# LANGUAGE LambdaCase      #-}
+{-# LANGUAGE MultiWayIf      #-}
 {-# LANGUAGE NamedFieldPuns  #-}
 {-# LANGUAGE RecordWildCards #-}
 
@@ -501,6 +502,7 @@ listener appState observer = do
         putIsListenerOn appState True
         SQL.listen db $ SQL.toPgIdentifier dbChannel
         SQL.waitForNotifications handleNotification db
+
       Left err -> do
         observer $ DBListenerFail dbChannel err
         exitFailure
@@ -517,11 +519,11 @@ listener appState observer = do
       -- retry the listener
       listener appState observer
 
-    handleNotification _ msg
-      | BS.null msg            = cacheReloader
-      | msg == "reload schema" = cacheReloader
-      | msg == "reload config" = reReadConfig False appState observer
-      | otherwise              = pure () -- Do nothing if anything else than an empty message is sent
+    handleNotification channel msg =
+      if | BS.null msg            -> observer (DBListenerGotSCacheMsg channel) >> cacheReloader
+         | msg == "reload schema" -> observer (DBListenerGotSCacheMsg channel) >> cacheReloader
+         | msg == "reload config" -> observer (DBListenerGotConfigMsg channel) >> reReadConfig False appState observer
+         | otherwise              -> pure () -- Do nothing if anything else than an empty message is sent
 
     cacheReloader =
       -- reloads the schema cache + restarts pool connections

src/PostgREST/Observation.hs

@@ -40,6 +40,8 @@ data Observation
   | DBListenerStart Text
   | DBListenerFail Text SQL.ConnectionError
   | DBListenerFailRecoverObs Bool Text (Either SomeException ())
+  | DBListenerGotSCacheMsg ByteString
+  | DBListenerGotConfigMsg ByteString
   | ConfigReadErrorObs
   | ConfigReadErrorFatalObs SQL.UsageError Text
   | ConfigReadErrorNotFatalObs SQL.UsageError
@@ -82,11 +84,15 @@ observationMessage = \case
   ConnectionPgVersionErrorObs usageErr ->
     jsonMessage usageErr
   DBListenerStart channel -> do
-    "Listening for notifications on the " <> channel <> " channel"
+    "Listening for notifications on the " <> show channel <> " channel"
   DBListenerFail channel err -> do
     "Could not listen for notifications on the " <> channel <> " channel. " <> show err
   DBListenerFailRecoverObs recover channel err ->
     "Could not listen for notifications on the " <> channel <> " channel. " <> showListenerError err <> (if recover then " Retrying listening for notifications.." else mempty)
+  DBListenerGotSCacheMsg channel ->
+    "Received a schema cache reload message on the " <> show channel <> " channel"
+  DBListenerGotConfigMsg channel ->
+    "Received a config reload message on the " <> show channel <> " channel"
   ConfigReadErrorObs ->
     "An error ocurred when trying to query database settings for the config parameters"
   ConfigReadErrorFatalObs usageErr hint ->