PROTOCOL_ENQUEUE_AFTER_FATAL_ERROR with express-mysql-session

[SDAdham]

Hello,

I have followed https://stackoverflow.com/a/20211143/5224768 to fix PROTOCOL_CONNECTION_LOST which worked but now I am getting PROTOCOL_ENQUEUE_AFTER_FATAL_ERROR

Here is a snapshot of my code:

let connection: mysql.Connection;

  function handleDisconnect() {
    connection = mysql.createConnection(dbConfig); // Recreate the connection, since
    // the old one cannot be reused.

    connection.connect(function (err) {
      // The server is either down
      if (err) {
        // or restarting (takes a while sometimes).
        console.log('error when connecting to db:', err);
        setTimeout(handleDisconnect, 2000); // We introduce a delay before attempting to reconnect,
      } // to avoid a hot loop, and to allow our node script to
    }); // process asynchronous requests in the meantime.
    // If you're also serving http, display a 503 error.
    connection.on('error', function (err) {
      winstonLogger.error('db error', err);
      if (err.code === 'PROTOCOL_CONNECTION_LOST') {
        // Connection to the MySQL server is usually
        handleDisconnect(); // lost due to either server restart, or a
      } else {
        // connection idle timeout (the wait_timeout
        winstonLogger.error('Unexpected database connection error', err);
        // throw err; // server variable configures this)
      }
    });
  }

  handleDisconnect();

  /**
   * Session storage configuration
   */
  const sessionStore = new mySQLStore({} /* session store options */, connection);
  app.use(
    session({
      store: sessionStore,
     ....
    }),
  );

I know I am supposed to use connection pooling based on this comment https://github.com/chill117/express-mysql-session/issues/110#issuecomment-641212842

But I honestly don't know how to do this here. Can someone please help?

[SDAdham]

I am trying:

const pool = mysql.createPool({
    ...dbConfig,
    connectionLimit: 10,
  });

 /**
   * Session storage configuration
   */
  const sessionStore = new mySQLStore({} /* session store options */, pool );
  app.use(
    session({
      store: sessionStore,
     ....
    }),
  );

Hope this works.

[chill117]

I think you should not be trying to handle disconnects in your application code. The mysql pool handles this automatically. The error ("PROTOCOL_ENQUEUE_AFTER_FATAL_ERROR") means you're trying to use a mysql connection after it has already had a fatal error and disconnected. The pool object will discard such connections and open new ones automatically. So just use the pool object as needed for your db calls and disconnects/reconnects are handled for you.

[softcaredesign]

I have the same issues ... {"code":"PROTOCOL_ENQUEUE_AFTER_FATAL_ERROR","fatal":false}....

please give a solution

[chill117]

The latest release of this module uses the mysql2 module. By default, a connection pool will be used. This will handle connection/reconnection automatically so that you don't need to worry about that in your application code. Please see the readme for usage details.