Connection.connectTimeout is not cleared when connect error happens

Timeout connectTimeout which is created in Connection constructor (node_modules/mysql2/lib/connection.js) is not cleared when error happens. It should be cleared for example in callback _handleNetworkError.

Run this without mysqld listening on 127.0.0.1:3306:

let mysql = require("mysql2");
let connection = mysql.createConnection({});
connection.on("error", err => console.log(new Date(), "error", err))
process.on("exit", () => console.log(new Date(), "exit"));

Possible output:

2019-08-06T20:05:27.571Z error Error: connect ECONNREFUSED 127.0.0.1:3306
    at TCPConnectWrap.afterConnect [as oncomplete] (net.js:1056:14) {
  errno: 'ECONNREFUSED',
  code: 'ECONNREFUSED',
  syscall: 'connect',
  address: '127.0.0.1',
  port: 3306,
  fatal: true
}
2019-08-06T20:05:37.573Z exit

Notice that it takes 10 seconds to exit which is default for connect timeout.

Without error event handler on repl.it:

let mysql = require("mysql2");
let connection = mysql.createConnection({});

Process crashed with: Error: connect ECONNREFUSED 127.0.0.1:3306
    at TCPConnectWrap.afterConnect [as oncomplete] (net.js:1106:14)
Process crashed with: Error: Connection lost: The server closed the connection.
    at Socket.Connection.stream.on (/home/runner/node_modules/mysql2/lib/connection.js:88:31)
    at Socket.emit (events.js:198:13)
    at TCP._handle.close (net.js:606:12)
Process crashed with: Error: connect ETIMEDOUT
    at Connection._handleTimeoutError (/home/runner/node_modules/mysql2/lib/connection.js:171:17)
    at ontimeout (timers.js:436:11)
    at tryOnTimeout (timers.js:300:5)
    at listOnTimeout (timers.js:263:5)
    at Timer.processTimers (timers.js:223:10)

This change solves this problem: Before:

  _handleNetworkError(err) {
    // Do not throw an error when a connection ends with a RST,ACK packet
    if (err.errno === 'ECONNRESET' && this._closing) {
      return;
    }
    this._handleFatalError(err);
  }

After:

  _handleNetworkError(err) {
    if (this.connectTimeout) {
      Timers.clearTimeout(this.connectTimeout);
      this.connectTimeout = null;
    }
    // Do not throw an error when a connection ends with a RST,ACK packet
    if (err.errno === 'ECONNRESET' && this._closing) {
      return;
    }
    this._handleFatalError(err);
  }

Now it exits immediately:

2019-08-06T20:11:31.459Z error Error: connect ECONNREFUSED 127.0.0.1:3306
    at TCPConnectWrap.afterConnect [as oncomplete] (net.js:1056:14) {
  errno: 'ECONNREFUSED',
  code: 'ECONNREFUSED',
  syscall: 'connect',
  address: '127.0.0.1',
  port: 3306,
  fatal: true
}
2019-08-06T20:11:31.464Z exit

Maybe it should be cleared also in _handleFatalError.

[misos1]

@dvisztempacct It is basically leak. What if someone uses really long timeout? These leaked timeouts can add up and cause real problems. It is like leaking files by not closing stream created by fs.createReadStream.

[jacobbogers]

I will do PR, i need this fixed in my project