mysql-proxy.js

const mysql = require('mysql2');

const server = mysql.createServer();
server.listen(3307);
let connectionId = 0;

server.on('connection', conn => {
  connectionId++;
  console.log(`New connection ${connectionId}`);
  let acceptSalt = null;
  let acceptAuthToken = null;

  const remote = mysql.createConnection({
    authPlugins: {
      mysql_native_password: () => {
        return pluginData => {
          acceptSalt(pluginData);
          return new Promise(accept => (acceptAuthToken = accept));
        };
      }
    }
  });
  remote.serverConnId = connectionId;

  conn.serverHandshake({
    protocolVersion: 10,
    serverVersion: 'mysql proxy',
    connectionId,
    statusFlags: 2,
    characterSet: 8,
    capabilityFlags: 16777183, // all flags but no compression
    getSalt: () => new Promise(accept => (acceptSalt = accept)),
    authCallback: ({ user, database, authToken }) => {
      remote.config.user = user;
      remote.config.database = database;
      acceptAuthToken(authToken);
      // might worth moving this to remote.on('connected') and add error handler
      conn.writeOk();
      conn.sequenceId = 0;
    }
  });

  conn.on('query', sql => {
    conn.sequenceId = 1;
    console.log(`${remote.serverConnId} proxying query: ${sql}`);
    remote.query(sql, function(err, rows, columns) {
      if (err) {
        console.log(err);
        // TODO: proxy back error response
        return;
      }
      if (Array.isArray(rows)) {
        conn.writeTextResult(rows, columns);
        conn.sequenceId = 0;
      } else {
        // response to an 'insert', 'update' or 'delete'
        const result = rows;
        conn.writeOk(result);
        conn.sequenceId = 0;
      } 
    });
  });

  conn.on('error', err => {
    remote.end();
  });

  conn.on('quit', () => {
    console.log('Client closed connection');
    remote.end();
  });
});