Merge pull request #57 from diogob/shutdown-on-connection-failure

Shutdown server if listener connection dies

Author: diogob

app/Main.hs

@@ -52,25 +52,32 @@ main = do
                <> " / Connects websockets to PostgreSQL asynchronous notifications."
 
   conf <- loadSecretFile =<< readOptions
+  shutdownSignal <- newEmptyMVar
   let host = configHost conf
       port = configPort conf
       listenChannel = toS $ configListenChannel conf
       pgSettings = toS (configDatabase conf)
+      waitForShutdown cl = void $ forkIO (takeMVar shutdownSignal >> cl >> die "Shutting server down...")
+
       appSettings = setHost ((fromString . toS) host)
                   . setPort port
                   . setServerName (toS $ "postgres-websockets/" <> prettyVersion)
                   . setTimeout 3600
+                  . setInstallShutdownHandler waitForShutdown
+                  . setGracefulShutdownTimeout (Just 5)
                   $ defaultSettings
 
   putStrLn $ ("Listening on port " :: Text) <> show (configPort conf)
 
+  let shutdown = putErrLn ("Broadcaster connection is dead" :: Text) >> putMVar shutdownSignal ()
   pool <- P.acquire (configPool conf, 10, pgSettings)
-  multi <- newHasqlBroadcaster listenChannel pgSettings
+  multi <- newHasqlBroadcaster shutdown listenChannel pgSettings
   getTime <- mkGetTime
 
   runSettings appSettings $
     postgresWsMiddleware getTime listenChannel (configJwtSecret conf) pool multi $
     logStdout $ maybe dummyApp staticApp' (configPath conf)
+
   where
     mkGetTime :: IO (IO UTCTime)
     mkGetTime = mkAutoUpdate defaultUpdateSettings {updateAction = getCurrentTime}

src/PostgresWebsockets/HasqlBroadcast.hs

@@ -26,19 +26,19 @@ import PostgresWebsockets.Broadcast
 {- | Returns a multiplexer from a connection URI, keeps trying to connect in case there is any error.
    This function also spawns a thread that keeps relaying the messages from the database to the multiplexer's listeners
 -}
-newHasqlBroadcaster :: Text -> ByteString -> IO Multiplexer
-newHasqlBroadcaster ch = newHasqlBroadcasterForConnection . tryUntilConnected
+newHasqlBroadcaster :: IO () -> Text -> ByteString -> IO Multiplexer
+newHasqlBroadcaster onConnectionFailure ch = newHasqlBroadcasterForConnection . tryUntilConnected
   where
-    newHasqlBroadcasterForConnection = newHasqlBroadcasterForChannel ch
+    newHasqlBroadcasterForConnection = newHasqlBroadcasterForChannel onConnectionFailure ch
 
 {- | Returns a multiplexer from a connection URI or an error message on the left case
    This function also spawns a thread that keeps relaying the messages from the database to the multiplexer's listeners
 -}
-newHasqlBroadcasterOrError :: Text -> ByteString -> IO (Either ByteString Multiplexer)
-newHasqlBroadcasterOrError ch =
+newHasqlBroadcasterOrError :: IO () -> Text -> ByteString -> IO (Either ByteString Multiplexer)
+newHasqlBroadcasterOrError onConnectionFailure ch =
   acquire >=> (sequence . mapBoth show (newHasqlBroadcasterForConnection . return))
   where
-    newHasqlBroadcasterForConnection = newHasqlBroadcasterForChannel ch
+    newHasqlBroadcasterForConnection = newHasqlBroadcasterForChannel onConnectionFailure ch
 
 tryUntilConnected :: ByteString -> IO Connection
 tryUntilConnected =
@@ -78,13 +78,12 @@ tryUntilConnected =
    @
 
 -}
-newHasqlBroadcasterForChannel :: Text -> IO Connection -> IO Multiplexer
-newHasqlBroadcasterForChannel ch getCon = do
-  multi <- newMultiplexer openProducer closeProducer
+newHasqlBroadcasterForChannel :: IO () -> Text -> IO Connection -> IO Multiplexer
+newHasqlBroadcasterForChannel onConnectionFailure ch getCon = do
+  multi <- newMultiplexer openProducer $ const onConnectionFailure
   void $ relayMessagesForever multi
   return multi
   where
-    closeProducer _ = putErrLn "Broadcaster is dead"
     toMsg :: ByteString -> ByteString -> Message
     toMsg c m = case decode (toS m) of
                    Just v -> Message (channelDef c v) m

test/HasqlBroadcastSpec.hs

@@ -15,7 +15,7 @@ spec = describe "newHasqlBroadcaster" $ do
             <$> acquire connStr
 
     it "relay messages sent to the appropriate database channel" $ do
-      multi <- either (panic .show) id <$> newHasqlBroadcasterOrError "postgres-websockets" "postgres://localhost/postgres_ws_test"
+      multi <- either (panic .show) id <$> newHasqlBroadcasterOrError (pure ()) "postgres-websockets" "postgres://localhost/postgres_ws_test"
       msg <- liftIO newEmptyMVar
       onMessage multi "test" $ putMVar msg