Consider schema cache state on the ready check

* empty schema cache when it fails loading so the ready check can pick
  its new state

src/PostgREST/Admin.hs

@@ -21,16 +21,16 @@ import Protolude
 -- | PostgREST admin application
 postgrestAdmin :: AppState.AppState -> AppConfig -> Wai.Application
 postgrestAdmin appState appConfig req respond  = do
-  isMainAppReachable <- isRight <$> reachMainApp appConfig
+  isMainAppReachable  <- isRight <$> reachMainApp appConfig
+  isSchemaCacheLoaded <- isJust <$> AppState.getDbStructure appState
+  isConnectionUp      <-
+    if configDbChannelEnabled appConfig
+      then AppState.getIsListenerOn appState
+      else isRight <$> SQL.use (AppState.getPool appState) (SQL.sql "SELECT 1")
 
   case Wai.pathInfo req of
     ["ready"] ->
-      if configDbChannelEnabled appConfig then do
-        listenerOn <- AppState.getIsListenerOn appState
-        respond $ Wai.responseLBS (if listenerOn && isMainAppReachable then HTTP.status200 else HTTP.status503) [] mempty
-      else do
-        result <- SQL.use (AppState.getPool appState) $ SQL.sql "SELECT 1"
-        respond $ Wai.responseLBS (if isRight result && isMainAppReachable then HTTP.status200 else HTTP.status503) [] mempty
+      respond $ Wai.responseLBS (if isMainAppReachable && isConnectionUp && isSchemaCacheLoaded then HTTP.status200 else HTTP.status503) [] mempty
     ["live"] ->
       respond $ Wai.responseLBS (if isMainAppReachable then HTTP.status200 else HTTP.status503) [] mempty
     _ ->

src/PostgREST/AppState.hs

@@ -108,9 +108,8 @@ putPgVersion = atomicWriteIORef . statePgVersion
 getDbStructure :: AppState -> IO (Maybe DbStructure)
 getDbStructure = readIORef . stateDbStructure
 
-putDbStructure :: AppState -> DbStructure -> IO ()
-putDbStructure appState structure =
-  atomicWriteIORef (stateDbStructure appState) $ Just structure
+putDbStructure :: AppState -> Maybe DbStructure -> IO ()
+putDbStructure appState = atomicWriteIORef (stateDbStructure appState)
 
 getJsonDbS :: AppState -> IO ByteString
 getJsonDbS = readIORef . stateJsonDbS

src/PostgREST/Workers.hs

@@ -91,6 +91,7 @@ connectionWorker appState = do
               -- do nothing and proceed if the load was successful
               return ()
             SCOnRetry ->
+              -- retry reloading the schema cache
               work
             SCFatalFail ->
               -- die if our schema cache query has an error
@@ -169,12 +170,13 @@ loadSchemaCache appState = do
           AppState.logWithZTime appState hint
           return SCFatalFail
         Nothing -> do
+          AppState.putDbStructure appState Nothing
           AppState.logWithZTime appState "An error ocurred when loading the schema cache"
           putErr
           return SCOnRetry
 
     Right dbStructure -> do
-      AppState.putDbStructure appState dbStructure
+      AppState.putDbStructure appState (Just dbStructure)
       when (isJust configDbRootSpec) .
         AppState.putJsonDbS appState . LBS.toStrict $ JSON.encode dbStructure
       AppState.logWithZTime appState "Schema cache loaded"
@@ -247,7 +249,7 @@ reReadConfig startingUp appState = do
               AppState.logWithZTime appState hint
               killThread (AppState.getMainThreadId appState)
             Nothing -> do
-              AppState.logWithZTime appState $ show e
+              putErr
           pure []
         Right x -> pure x
     else
@@ -257,10 +259,10 @@ reReadConfig startingUp appState = do
       if startingUp then
         panic err -- die on invalid config if the program is starting up
       else
-        AppState.logWithZTime appState $ "Failed re-loading config: " <> err
+        AppState.logWithZTime appState $ "Failed reloading config: " <> err
     Right newConf -> do
       AppState.putConfig appState newConf
       if startingUp then
         pass
       else
-        AppState.logWithZTime appState "Config re-loaded"
+        AppState.logWithZTime appState "Config reloaded"