Nodejs, mysql 'connection lost the server closed the connection'

Question

I connected mysql to nodejs. After a certain period of time, you will get the error :

'Connection lost the server closed the connection'.

I need your help.

An error has occurred and we added the function handleDisconnect. However, once a disconnect is resolved, the second error occurs again from Connection lost the server closed the connection.

I wonder why it should be only once and not the second one.

ps: The description may not be smooth using a translator.

This is part of the app.js file

// connection to databases
var mysql_dbc = require('./config/db_con')();
var connection = mysql_dbc.init();
mysql_dbc.test_open(connection);

// Added Code
handleDisconnect(connection);
function handleDisconnect(client) {

  client.on('error', function (error) {

    if (!error.fatal) return;

    if (error.code !== 'PROTOCOL_CONNECTION_LOST') throw err;

    console.error('> Re-connecting lost MySQL connection: ' + error.stack);

    mysql_dbc.test_open(connection);

  });

};

Uzair Khan · Accepted Answer · 2019-07-06 10:52:24Z

2

You can try to use this code to handle server disconnect:

var mysql = require("mysql");
var configuration = {
  host: "localhost",
  user: "root",
  password: "mysql",
  database: "blog"
};
var connection;

function handleDisconnect() {
  connection = mysql.createConnection(configuration);

  connection.connect(function(err) {
    if (err) {
      console.log("error when connecting to db:", err);
      setTimeout(handleDisconnect, 2000);
    }else{
        console.log("connection is successfull");
    }
  });
  connection.on("error", function(err) {
    console.log("db error", err);
    if (err.code === "PROTOCOL_CONNECTION_LOST") {
      handleDisconnect();
    } else {
      throw err;
    }
  });
}
handleDisconnect();

You may lose the connection to a MySQL server due to network problems, the server timing you out, the server being restarted, or crashing. All of these events are considered fatal errors.

Re-connecting a connection is done by establishing a new connection. Once terminated, an existing connection object cannot be re-connected by design.

With Pool, disconnected connections will be removed from the pool freeing up space for a new connection to be created on the next getConnection call.

edited Jul 6, 2019 at 10:52

answered Jul 5, 2019 at 9:07

Uzair Khan

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2 Comments

BS Kim Over a year ago

Thank you for your first response. I get an error in this part. Did you have a typo? if(err) { sometimes).

Uzair Khan Over a year ago

yes, sorry removed it. you can check it now. it sould work

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