Reproduce MySQL error: The server closed the connection (node.js) - mysql

I'm trying to reproduce a MySQL error I'm seeing in my node.js app on EC2 with the node mysql library:
Connection lost: The server closed the connection.
I am unable to reproduce the error locally- killing the database is handled just fine by my code- it just rechecks every few seconds and reconnects to the db once it is restarted. On EC2, it happens around 4am Pacific, but the db is still up and running fine.
I'd like to
Reproduce the crash with my local mysql
Add whatever logic I need in my mysql helper module to handle this
Here's the error in my node.js app:
2012-10-22T08:45:40.518Z - error: uncaughtException date=Mon Oct 22
2012 08:45:40 GMT+0000 (UTC), pid=14184, uid=0, gid=0,
cwd=/home/ec2-user/my-app, execPath=/usr/bin/nodejs,
version=v0.6.18, argv=[/usr/local/bin/node,
/home/ec2-user/my-app/app.js, --my-app], rss=15310848,
heapTotal=6311392, heapUsed=5123292, loadavg=[0.0029296875,
0.0146484375, 0.04541015625], uptime=3238343.511107486, trace=[column=13,
file=/home/ec2-user/my-app/node_modules/mysql/lib/protocol/Protocol.js,
function=Protocol.end, line=63, method=end, native=false, column=10,
file=stream.js, function=Socket.onend, line=80, method=onend,
native=false, column=20, file=events.js, function=Socket.emit,
line=88, method=emit, native=false, column=51, file=net.js,
function=TCP.onread, line=388, method=onread, native=false],
stack=[Error: Connection lost: The server closed the connection.,
at Protocol.end
(/home/ec2-user/my-app/node_modules/mysql/lib/protocol/Protocol.js:63:13), at Socket.onend (stream.js:80:10), at Socket.emit
(events.js:88:20), at TCP.onread (net.js:388:51)]
Here's my code (mysql helper module):
module.exports = function (conf,logger) {
var mysql = require('mysql');
var connectionState = false;
var connection = mysql.createConnection({
host: conf.db.hostname,
user: conf.db.user,
password: conf.db.pass,
database: conf.db.schema,
insecureAuth: true
});
function attemptConnection(connection) {
if(!connectionState){
connection = mysql.createConnection(connection.config);
connection.connect(function (err) {
// connected! (unless `err` is set)
if (err) {
logger.error('mysql db unable to connect: ' + err);
connectionState = false;
} else {
logger.info('mysql connect!');
connectionState = true;
}
});
connection.on('close', function (err) {
logger.error('mysqldb conn close');
connectionState = false;
});
connection.on('error', function (err) {
logger.error('mysqldb error: ' + err);
connectionState = false;
/*
if (!err.fatal) {
return;
}
if (err.code !== 'PROTOCOL_CONNECTION_LOST') {
throw err;
}
*/
});
}
}
attemptConnection(connection);
var dbConnChecker = setInterval(function(){
if(!connectionState){
logger.info('not connected, attempting reconnect');
attemptConnection(connection);
}
}, conf.db.checkInterval);
return connection;
};

Check out mysql pool feature in node-mysql
var mysql = require('mysql');
var pool = mysql.createPool({
host : 'example.org',
user : 'bob',
password : 'secret'
});
pool.getConnection(function(err, connection) {
// connected! (unless `err` is set)
connection.end();
});

I was having similar problems and created a getConnection() wrapper function that checks the health of the mysql connection before returning it to the caller and re-establishes the connection as necessary. In my testing it has handled fatal and non-fatal connection issues transparently for the application. If the connection simply timed out, the application recovers without experiencing any errors. If there is a transient but fatal database connection problem, the application will resume functioning automatically as soon as database connectivity is available again.
As far as reproducing the problem for testing, add the following two lines to the my.ini or my.cnf file under the [mysqld] block:
interactive_timeout=30
wait_timeout=30
Here is the contents of a file I have named "database.js":
var mysql = require("mysql");
var CONFIG = require(__dirname + "/configuration");
module.exports.getConnection = function() {
// Test connection health before returning it to caller.
if ((module.exports.connection) && (module.exports.connection._socket)
&& (module.exports.connection._socket.readable)
&& (module.exports.connection._socket.writable)) {
return module.exports.connection;
}
console.log(((module.exports.connection) ?
"UNHEALTHY SQL CONNECTION; RE" : "") + "CONNECTING TO SQL.");
var connection = mysql.createConnection({
host : CONFIG.db.host,
user : CONFIG.db.user,
password : CONFIG.db.password,
database : CONFIG.db.database,
port : CONFIG.db.port
});
connection.connect(function(err) {
if (err) {
console.log("SQL CONNECT ERROR: " + err);
} else {
console.log("SQL CONNECT SUCCESSFUL.");
}
});
connection.on("close", function (err) {
console.log("SQL CONNECTION CLOSED.");
});
connection.on("error", function (err) {
console.log("SQL CONNECTION ERROR: " + err);
});
module.exports.connection = connection;
return module.exports.connection;
}
// Open a connection automatically at app startup.
module.exports.getConnection();
// If you've saved this file as database.js, then get and use the
// connection as in the following example:
// var database = require(__dirname + "/database");
// var connection = database.getConnection();
// connection.query(query, function(err, results) { ....

Here's what I ended up using, and it worked pretty well. On the occasional connection lost/restart it recovered nicely. I have a database.js file which establishes connections and checks them periodically.
To make a request:
var conn = require('./database');
var sql = 'SELECT foo FROM bar;';
conn.query(sql, [userId, plugId], function (err, rows) {
// logic
}
Here's my databbase.js
var mysql = require('mysql');
var Common = require('./common');
var conf = Common.conf;
var logger = Common.logger;
var connectionState = false;
var connection = mysql.createConnection({
host: conf.db.hostname,
user: conf.db.user,
password: conf.db.pass,
database: conf.db.schema,
insecureAuth: true
});
connection.on('close', function (err) {
logger.error('mysqldb conn close');
connectionState = false;
});
connection.on('error', function (err) {
logger.error('mysqldb error: ' + err);
connectionState = false;
});
function attemptConnection(connection) {
if(!connectionState){
connection = mysql.createConnection(connection.config);
connection.connect(function (err) {
// connected! (unless `err` is set)
if (err) {
logger.error('mysql db unable to connect: ' + err);
connectionState = false;
} else {
logger.info('mysql connect!');
connectionState = true;
}
});
connection.on('close', function (err) {
logger.error('mysqldb conn close');
connectionState = false;
});
connection.on('error', function (err) {
logger.error('mysqldb error: ' + err);
if (!err.fatal) {
//throw err;
}
if (err.code !== 'PROTOCOL_CONNECTION_LOST') {
//throw err;
} else {
connectionState = false;
}
});
}
}
attemptConnection(connection);
var dbConnChecker = setInterval(function(){
if(!connectionState){
logger.info('not connected, attempting reconnect');
attemptConnection(connection);
}
}, conf.db.checkInterval);
// Mysql query wrapper. Gives us timeout and db conn refreshal!
var queryTimeout = conf.db.queryTimeout;
var query = function(sql,params,callback){
if(connectionState) {
// 1. Set timeout
var timedOut = false;
var timeout = setTimeout(function () {
timedOut = true;
callback('MySQL timeout', null);
}, queryTimeout);
// 2. Make query
connection.query(sql, params, function (err, rows) {
clearTimeout(timeout);
if(!timedOut) callback(err,rows);
});
} else {
// 3. Fail if no mysql conn (obviously)
callback('MySQL not connected', null);
}
}
// And we present the same interface as the node-mysql library!
// NOTE: The escape may be a trickier for other libraries to emulate because it looks synchronous
exports.query = query;
exports.escape = connection.escape;

Using generic-pool, I wrote something that works locally. I guess I'll test it and see if it doesn't crash in bizarre manner on the server side.
// Test node connection pool stuff
// Create a MySQL connection pool with
// a max of 10 connections, a min of 2, and a 30 second max idle time
var poolModule = require('generic-pool');
var pool = poolModule.Pool({
name : 'mysql',
create : function(callback) {
var Client = require('mysql').Client; // use node-mysql library in all it's dubious glory
var c = new Client();
c.user = 'root';
c.password = 'xxx';
c.database = 'test';
c.on('close', function (err) {
console.log('mysqldb conn close');
});
c.on('error', function (err) {
console.log('mysqldb error: ' + err);
});
// parameter order: err, resource
// new in 1.0.6
callback(null, c);
},
destroy : function(client) { client.end(); },
max : 10,
// optional. if you set this, make sure to drain() (see step 3)
min : 2,
// specifies how long a resource can stay idle in pool before being removed
idleTimeoutMillis : 30000,
// if true, logs via console.log - can also be a function
log : true
});
var http = require('http');
http.createServer(function (req, res) {
// Get db conn
pool.acquire(function(err, client) {
if (err) {
// handle error - this is generally the err from your
// factory.create function
console.log('pool.acquire err: ' + err);
res.writeHead(500, {'Content-Type': 'application/json'});
out = {
err: err
}
res.end(JSON.stringify(out));
}
else {
client.query("select * from foo", [], function(err, results) {
if(err){
res.writeHead(500, {'Content-Type': 'application/json'});
out = {
err: err
}
res.end(JSON.stringify(out));
} else {
res.writeHead(500, {'Content-Type': 'application/json'});
out = {
results: results
}
res.end(JSON.stringify(out));
}
// return object back to pool
pool.release(client);
});
}
});
}).listen(9615);
Pretty please don't die at 4am for no apparent reason!

The solution is use pooling connection !
You can wrote code to handle connection manually, it works.
However pooling is design for this, use pooling connection solved connection drop error.
var mysql = require('mysql');
var pool = mysql.createPool({
connectionLimit : 10,
host : 'example.org',
user : 'bob',
password : 'secret',
database : 'my_db'
});
pool.query('SELECT 1 + 1 AS solution', function (error, results, fields) {
if (error) throw error;
console.log('The solution is: ', results[0].solution);
});
pooling mysql connection

Related

Mysql connection closed after some time in node js and gives PROTOCOL_CONNECTION_LOST'

I am new in node mysql and I am facing an issue. My node js server gets closed and gives connection closed PROTOCOL_CONNECTION_LOST.I don't understand where I am going wrong. Please resolve if any one has knowledge about it.Thanks in advance
var sockjs = require('sockjs');
var mysql = require('mysql');
var connection = mysql.createConnection({
host : process.env.IP,
user : 'root',
port : '80',
password : '123456',
database : 'test',
});
connection.connect(function(err) {
if(err){
console.log('error in connection is : ',err);
}else{
console.log("Connected!");
}
});
var echo = sockjs.createServer();
var connections = [];
echo.on('connection', function (conn) {
connections.push(conn);
conn.on('data', function (message) {
var sql1 = "SELECT count(`id`) as counting FROM `complaints_chat` WHERE `createby`='client' and `read`='0'";
connection.query(sql1, function(err, rows, fields) {
if (err) throw err;
if (rows.length > 0) {
counting=rows[0]['counting'];
}else{ counting=0; }
});
});
});
you can recover connect,when it's unconnect.such as
connection.on('error', err => {
if (err.code === 'PROTOCOL_CONNECTION_LOST') {
// db error reconnect
disconnect_handler();
} else {
throw err;
}
});

How to provide a mysql database connection in single file in nodejs

I need to provide the mysql connection for modules. I have a code like this.
var express = require('express'),
app = express(),
server = require('http').createServer(app);
var mysql = require('mysql');
var connection = mysql.createConnection({
host : '127.0.0.1',
user : 'root',
password : '',
database : 'chat'
});
connection.connect(function(err) {
if (err) {
console.error('error connecting: ' + err.stack);
return;
}
});
app.get('/save', function(req,res){
var post = {from:'me', to:'you', msg:'hi'};
var query = connection.query('INSERT INTO messages SET ?', post, function(err, result) {
if (err) throw err;
});
});
server.listen(3000);
But how we provide one time mysql connection for all the modules.
You could create a db wrapper then require it. node's require returns the same instance of a module every time, so you can perform your connection and return a handler. From the Node.js docs:
every call to require('foo') will get exactly the same object returned, if it would resolve to the same file.
You could create db.js:
var mysql = require('mysql');
var connection = mysql.createConnection({
host : '127.0.0.1',
user : 'root',
password : '',
database : 'chat'
});
connection.connect(function(err) {
if (err) throw err;
});
module.exports = connection;
Then in your app.js, you would simply require it.
var express = require('express');
var app = express();
var db = require('./db');
app.get('/save',function(req,res){
var post = {from:'me', to:'you', msg:'hi'};
db.query('INSERT INTO messages SET ?', post, function(err, result) {
if (err) throw err;
});
});
server.listen(3000);
This approach allows you to abstract any connection details, wrap anything else you want to expose and require db throughout your application while maintaining one connection to your db thanks to how node require works :)
I took a similar approach as Sean3z but instead I have the connection closed everytime i make a query.
His way works if it's only executed on the entry point of your app, but let's say you have controllers that you want to do a var db = require('./db'). You can't because otherwise everytime you access that controller you will be creating a new connection.
To avoid that, i think it's safer, in my opinion, to open and close the connection everytime.
here is a snippet of my code.
mysq_query.js
// Dependencies
var mysql = require('mysql'),
config = require("../config");
/*
* #sqlConnection
* Creates the connection, makes the query and close it to avoid concurrency conflicts.
*/
var sqlConnection = function sqlConnection(sql, values, next) {
// It means that the values hasnt been passed
if (arguments.length === 2) {
next = values;
values = null;
}
var connection = mysql.createConnection(config.db);
connection.connect(function(err) {
if (err !== null) {
console.log("[MYSQL] Error connecting to mysql:" + err+'\n');
}
});
connection.query(sql, values, function(err) {
connection.end(); // close the connection
if (err) {
throw err;
}
// Execute the callback
next.apply(this, arguments);
});
}
module.exports = sqlConnection;
Than you can use it anywhere just doing like
var mysql_query = require('path/to/your/mysql_query');
mysql_query('SELECT * from your_table where ?', {id: '1'}, function(err, rows) {
console.log(rows);
});
UPDATED:
config.json looks like
{
"db": {
"user" : "USERNAME",
"password" : "PASSWORD",
"database" : "DATABASE_NAME",
"socketPath": "/tmp/mysql.sock"
}
}
Hope this helps.
I think that you should use a connection pool instead of share a single connection. A connection pool would provide a much better performance, as you can check here.
As stated in the library documentation, it occurs because the MySQL protocol is sequential (this means that you need multiple connections to execute queries in parallel).
Connection Pool Docs
From the node.js documentation, "To have a module execute code multiple times, export a function, and call that function", you could use node.js module.export and have a single file to manage the db connections.You can find more at Node.js documentation. Let's say db.js file be like:
const mysql = require('mysql');
var connection;
module.exports = {
dbConnection: function () {
connection = mysql.createConnection({
host: "127.0.0.1",
user: "Your_user",
password: "Your_password",
database: 'Your_bd'
});
connection.connect();
return connection;
}
};
Then, the file where you are going to use the connection could be like useDb.js:
const dbConnection = require('./db');
var connection;
function callDb() {
try {
connection = dbConnectionManager.dbConnection();
connection.query('SELECT 1 + 1 AS solution', function (error, results, fields) {
if (!error) {
let response = "The solution is: " + results[0].solution;
console.log(response);
} else {
console.log(error);
}
});
connection.end();
} catch (err) {
console.log(err);
}
}
var mysql = require('mysql');
var pool = mysql.createPool({
host : 'yourip',
port : 'yourport',
user : 'dbusername',
password : 'dbpwd',
database : 'database schema name',
dateStrings: true,
multipleStatements: true
});
// TODO - if any pool issues need to try this link for connection management
// https://stackoverflow.com/questions/18496540/node-js-mysql-connection-pooling
module.exports = function(qry, qrytype, msg, callback) {
if(qrytype != 'S') {
console.log(qry);
}
pool.getConnection(function(err, connection) {
if(err) {
if(connection)
connection.release();
throw err;
}
// Use the connection
connection.query(qry, function (err, results, fields) {
connection.release();
if(err) {
callback('E#connection.query-Error occurred.#'+ err.sqlMessage);
return;
}
if(qrytype==='S') {
//for Select statement
// setTimeout(function() {
callback(results);
// }, 500);
} else if(qrytype==='N'){
let resarr = results[results.length-1];
let newid= '';
if(resarr.length)
newid = resarr[0]['#eid'];
callback(msg + newid);
} else if(qrytype==='U'){
//let ret = 'I#' + entity + ' updated#Updated rows count: ' + results[1].changedRows;
callback(msg);
} else if(qrytype==='D'){
//let resarr = results[1].affectedRows;
callback(msg);
}
});
connection.on('error', function (err) {
connection.release();
callback('E#connection.on-Error occurred.#'+ err.sqlMessage);
return;
});
});
}
try this
var express = require('express');
var mysql = require('mysql');
var path = require('path');
var favicon = require('serve-favicon');
var logger = require('morgan');
var cookieParser = require('cookie-parser');
var bodyParser = require('body-parser');
var routes = require('./routes/index');
var users = require('./routes/users');
var app = express();
// view engine setup
app.set('views', path.join(__dirname, 'views'));
app.set('view engine', 'jade');
// uncomment after placing your favicon in /public
//app.use(favicon(path.join(__dirname, 'public', 'favicon.ico')));
app.use(logger('dev'));
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: false }));
app.use(cookieParser());
app.use(express.static(path.join(__dirname, 'public')));
app.use('/', routes);
app.use('/users', users);
// catch 404 and forward to error handler
app.use(function(req, res, next) {
var err = new Error('Not Found');
err.status = 404;
next(err);
});
// error handlers
// development error handler
// will print stacktrace
console.log(app);
if (app.get('env') === 'development') {
app.use(function(err, req, res, next) {
res.status(err.status || 500);
res.render('error', {
message: err.message,
error: err
});
});
}
// production error handler
// no stacktraces leaked to user
app.use(function(err, req, res, next) {
res.status(err.status || 500);
res.render('error', {
message: err.message,
error: {}
});
});
var con = mysql.createConnection({
host: "localhost",
user: "root",
password: "admin123",
database: "sitepoint"
});
con.connect(function(err){
if(err){
console.log('Error connecting to Db');
return;
}
console.log('Connection established');
});
module.exports = app;
you can create a global variable and then access that variable in other files.
here is my code, I have created a separate file for MySQL database connection called db.js
const mysql = require('mysql');
var conn = mysql.createConnection({
host: "localhost",
user: "root",
password: "xxxxx",
database: "test"
});
conn.connect((err) => {
if (err) throw err;
console.log('Connected to the MySql DB');
});
module.exports = conn;
Then in the app.js file
const express = require('express');
const router = express.Router();
// MySql Db connection and set in globally
global.db = require('../config/db');
Now you can use it in any other file
const express = require('express');
const router = express.Router();
router.post('/signin', (req, res) => {
try {
var param = req.body;
var sql = `select * from user`;
// db is global variable
db.query(sql, (err, data) => {
if (err) throw new SyntaxError(err);
res.status(200).json({ 'auth': true, 'data': data });
});
} catch (err) {
res.status(400).json({ 'auth': false, 'data': err.message });
}
});

Simple server handling routes and giving error nodejs mysql

I'm trying to write a simple server using nodejs and have the server ship back different queries and/or custom headers/responses based on the routes. However, in the getUsers() function the error keeps getting hit and printing the 'Error querying' to the console instead of printing the email rows. I know the server is connected fine, because I can return a query when I just use the db and return a query with createConnection only using the second example. Any help spotting the error is greatly appreciated. Thanks.
What I'm trying to get done:
var http = require('http');
var mysql = require('mysql');
var url = require('url');
var util = require('util');
var db = mysql.createConnection({
host : "*********",
user : "*********",
password : "*********",
port : '****',
database : '*********'
});
db.connect(function(err) {
console.log('connected');
if (err)
console.error('Error connecting to db' + err.stack);
});
function getUsers() {
db.query('SELECT * FROM users', function(err, rows, fields) {
if (err)
// changed console.error('Error querying');
console.error(err);
if (rows)
console.log('Rows not null');
for (var i in rows) {
console.log(rows[i].email)
}
});
}
var server = http.createServer(function(req, res) {
console.log(req.url);
if (req.url == '/signup') {
console.log("User signing up");
} else if (req.url == '/signin') {
console.log("User signing in");
} else if (req.url == '/new') {
console.log("User request new game");
getUsers();
}
//res.writeHead(200);
//res.end('Hello Http');
});
server.listen(3000);
// changed and commented out db.end();
What does work with querying the db:
var connection = mysql.createConnection({
host : "********",
user : "********",
password : "********",
port : '****',
database : '********'
});
connection.connect();
var queryString = 'SELECT * FROM users';
connection.query(queryString, function(err, rows, fields) {
if (err) throw err;
for (var i in rows) {
console.log('Users: ', rows[i].email);
}
});
connection.end();
The code has been updated with the changes, and the problem was I was closing the database. After changing the error logs as was suggested in the comments, this was the error received.
{ [Error: Cannot enqueue Query after invoking quit.] code: 'PROTOCOL_ENQUEUE_AFTER_QUIT', fatal: false }
I then commented out the
db.end()
and the queries were returned fine.
Thanks for the help.

node.js + mysql connection pooling

I'm trying to figure out how to structure my application to use MySQL most efficent way. I'm using node-mysql module. Other threads here suggested to use connection pooling so i set up a little module mysql.js
var mysql = require('mysql');
var pool = mysql.createPool({
host : 'localhost',
user : 'root',
password : 'root',
database : 'guess'
});
exports.pool = pool;
Now whenever I want to query mysql I require this module and then query the databse
var mysql = require('../db/mysql').pool;
var test = function(req, res) {
mysql.getConnection(function(err, conn){
conn.query("select * from users", function(err, rows) {
res.json(rows);
})
})
}
Is this good approach? I couldn't really find too much examples of using mysql connections besides very simple one where everything is done in main app.js script so I don't really know what the convention / best practices are.
Should I always use connection.end() after each query? What if I forget about it somewhere?
How to rewrite the exports part of my mysql module to return just a connection so I don't have to write getConnection() every time?
It's a good approach.
If you just want to get a connection add the following code to your module where the pool is in:
var getConnection = function(callback) {
pool.getConnection(function(err, connection) {
callback(err, connection);
});
};
module.exports = getConnection;
You still have to write getConnection every time. But you could save the connection in the module the first time you get it.
Don't forget to end the connection when you are done using it:
connection.release();
You should avoid using pool.getConnection() if you can. If you call pool.getConnection(), you must call connection.release() when you are done using the connection. Otherwise, your application will get stuck waiting forever for connections to be returned to the pool once you hit the connection limit.
For simple queries, you can use pool.query(). This shorthand will automatically call connection.release() for you—even in error conditions.
function doSomething(cb) {
pool.query('SELECT 2*2 "value"', (ex, rows) => {
if (ex) {
cb(ex);
} else {
cb(null, rows[0].value);
}
});
}
However, in some cases you must use pool.getConnection(). These cases include:
Making multiple queries within a transaction.
Sharing data objects such as temporary tables between subsequent queries.
If you must use pool.getConnection(), ensure you call connection.release() using a pattern similar to below:
function doSomething(cb) {
pool.getConnection((ex, connection) => {
if (ex) {
cb(ex);
} else {
// Ensure that any call to cb releases the connection
// by wrapping it.
cb = (cb => {
return function () {
connection.release();
cb.apply(this, arguments);
};
})(cb);
connection.beginTransaction(ex => {
if (ex) {
cb(ex);
} else {
connection.query('INSERT INTO table1 ("value") VALUES (\'my value\');', ex => {
if (ex) {
cb(ex);
} else {
connection.query('INSERT INTO table2 ("value") VALUES (\'my other value\')', ex => {
if (ex) {
cb(ex);
} else {
connection.commit(ex => {
cb(ex);
});
}
});
}
});
}
});
}
});
}
I personally prefer to use Promises and the useAsync() pattern. This pattern combined with async/await makes it a lot harder to accidentally forget to release() the connection because it turns your lexical scoping into an automatic call to .release():
async function usePooledConnectionAsync(actionAsync) {
const connection = await new Promise((resolve, reject) => {
pool.getConnection((ex, connection) => {
if (ex) {
reject(ex);
} else {
resolve(connection);
}
});
});
try {
return await actionAsync(connection);
} finally {
connection.release();
}
}
async function doSomethingElse() {
// Usage example:
const result = await usePooledConnectionAsync(async connection => {
const rows = await new Promise((resolve, reject) => {
connection.query('SELECT 2*4 "value"', (ex, rows) => {
if (ex) {
reject(ex);
} else {
resolve(rows);
}
});
});
return rows[0].value;
});
console.log(`result=${result}`);
}
You will find this wrapper usefull :)
var pool = mysql.createPool(config.db);
exports.connection = {
query: function () {
var queryArgs = Array.prototype.slice.call(arguments),
events = [],
eventNameIndex = {};
pool.getConnection(function (err, conn) {
if (err) {
if (eventNameIndex.error) {
eventNameIndex.error();
}
}
if (conn) {
var q = conn.query.apply(conn, queryArgs);
q.on('end', function () {
conn.release();
});
events.forEach(function (args) {
q.on.apply(q, args);
});
}
});
return {
on: function (eventName, callback) {
events.push(Array.prototype.slice.call(arguments));
eventNameIndex[eventName] = callback;
return this;
}
};
}
};
Require it, use it like this:
db.connection.query("SELECT * FROM `table` WHERE `id` = ? ", row_id)
.on('result', function (row) {
setData(row);
})
.on('error', function (err) {
callback({error: true, err: err});
});
I am using this base class connection with mysql:
"base.js"
var mysql = require("mysql");
var pool = mysql.createPool({
connectionLimit : 10,
host: Config.appSettings().database.host,
user: Config.appSettings().database.username,
password: Config.appSettings().database.password,
database: Config.appSettings().database.database
});
var DB = (function () {
function _query(query, params, callback) {
pool.getConnection(function (err, connection) {
if (err) {
connection.release();
callback(null, err);
throw err;
}
connection.query(query, params, function (err, rows) {
connection.release();
if (!err) {
callback(rows);
}
else {
callback(null, err);
}
});
connection.on('error', function (err) {
connection.release();
callback(null, err);
throw err;
});
});
};
return {
query: _query
};
})();
module.exports = DB;
Just use it like that:
var DB = require('../dal/base.js');
DB.query("select * from tasks", null, function (data, error) {
callback(data, error);
});
When you are done with a connection, just call connection.release() and the connection will return to the pool, ready to be used again by someone else.
var mysql = require('mysql');
var pool = mysql.createPool(...);
pool.getConnection(function(err, connection) {
// Use the connection
connection.query('SELECT something FROM sometable', function (error, results, fields) {
// And done with the connection.
connection.release();
// Handle error after the release.
if (error) throw error;
// Don't use the connection here, it has been returned to the pool.
});
});
If you would like to close the connection and remove it from the pool, use connection.destroy() instead. The pool will create a new connection the next time one is needed.
Source: https://github.com/mysqljs/mysql
You can use this format as I used
const mysql = require('mysql');
const { HOST, USERNAME, PASSWORD, DBNAME, PORT } = process.env;
console.log();
const conn = mysql.createPool({
host: HOST,
user: USERNAME,
password: PASSWORD,
database: DBNAME
}, { debug: true });
conn.query('SELECT 1 + 1 AS solution', function (error, results, fields) {
if (error) throw error;
console.log('Db is connected - The solution is: ', results[0].solution);
});
module.exports = conn;
Using the standard mysql.createPool(), connections are lazily created by the pool. If you configure the pool to allow up to 100 connections, but only ever use 5 simultaneously, only 5 connections will be made. However if you configure it for 500 connections and use all 500 they will remain open for the durations of the process, even if they are idle!
This means if your MySQL Server max_connections is 510 your system will only have 10 mySQL connections available until your MySQL Server closes them (depends on what you have set your wait_timeout to) or your application closes! The only way to free them up is to manually close the connections via the pool instance or close the pool.
mysql-connection-pool-manager module was created to fix this issue and automatically scale the number of connections dependant on the load. Inactive connections are closed and idle connection pools are eventually closed if there has not been any activity.
// Load modules
const PoolManager = require('mysql-connection-pool-manager');
// Options
const options = {
...example settings
}
// Initialising the instance
const mySQL = PoolManager(options);
// Accessing mySQL directly
var connection = mySQL.raw.createConnection({
host : 'localhost',
user : 'me',
password : 'secret',
database : 'my_db'
});
// Initialising connection
connection.connect();
// Performing query
connection.query('SELECT 1 + 1 AS solution', function (error, results, fields) {
if (error) throw error;
console.log('The solution is: ', results[0].solution);
});
// Ending connection
connection.end();
Ref: https://www.npmjs.com/package/mysql-connection-pool-manager
i always use connection.relase(); after pool.getconnetion like
pool.getConnection(function (err, connection) {
connection.release();
if (!err)
{
console.log('*** Mysql Connection established with ', config.database, ' and connected as id ' + connection.threadId);
//CHECKING USERNAME EXISTENCE
email = receivedValues.email
connection.query('SELECT * FROM users WHERE email = ?', [email],
function (err, rows) {
if (!err)
{
if (rows.length == 1)
{
if (bcrypt.compareSync(req.body.password, rows[0].password))
{
var alldata = rows;
var userid = rows[0].id;
var tokendata = (receivedValues, userid);
var token = jwt.sign(receivedValues, config.secret, {
expiresIn: 1440 * 60 * 30 // expires in 1440 minutes
});
console.log("*** Authorised User");
res.json({
"code": 200,
"status": "Success",
"token": token,
"userData": alldata,
"message": "Authorised User!"
});
logger.info('url=', URL.url, 'Responce=', 'User Signin, username', req.body.email, 'User Id=', rows[0].id);
return;
}
else
{
console.log("*** Redirecting: Unauthorised User");
res.json({"code": 200, "status": "Fail", "message": "Unauthorised User!"});
logger.error('*** Redirecting: Unauthorised User');
return;
}
}
else
{
console.error("*** Redirecting: No User found with provided name");
res.json({
"code": 200,
"status": "Error",
"message": "No User found with provided name"
});
logger.error('url=', URL.url, 'No User found with provided name');
return;
}
}
else
{
console.log("*** Redirecting: Error for selecting user");
res.json({"code": 200, "status": "Error", "message": "Error for selecting user"});
logger.error('url=', URL.url, 'Error for selecting user', req.body.email);
return;
}
});
connection.on('error', function (err) {
console.log('*** Redirecting: Error Creating User...');
res.json({"code": 200, "status": "Error", "message": "Error Checking Username Duplicate"});
return;
});
}
else
{
Errors.Connection_Error(res);
}
});

Node.js MySQL Needing Persistent Connection

I need a persistent MySQL connection for my Node web app. The problem is that this happens about a few times a day:
Error: Connection lost: The server closed the connection.
at Protocol.end (/var/www/n/node_modules/mysql/lib/protocol/Protocol.js:73:13)
at Socket.onend (stream.js:79:10)
at Socket.EventEmitter.emit (events.js:117:20)
at _stream_readable.js:895:16
at process._tickCallback (node.js:415:13)
error: Forever detected script exited with code: 8
error: Forever restarting script for 2 time
info: socket.io started
Here is my connection code:
// Yes I know multipleStatements can be dangerous in the wrong hands.
var sql = mysql.createConnection({
host: 'localhost',
user: 'my_username',
password: 'my_password',
database: 'my_database',
multipleStatements: true
});
sql.connect();
function handleDisconnect(connection) {
connection.on('error', function(err) {
if (!err.fatal) {
return;
}
if (err.code !== 'PROTOCOL_CONNECTION_LOST') {
throw err;
}
console.log('Re-connecting lost connection: ' + err.stack);
sql = mysql.createConnection(connection.config);
handleDisconnect(sql);
sql.connect();
});
}
handleDisconnect(sql);
As you can see, the handleDisconnect code does not work..
Use the mysql connection pool. It will reconnect when a connection dies and you get the added benefit of being able to make multiple sql queries at the same time. If you don't use the database pool, your app will block database requests while waiting for currently running database requests to finish.
I usually define a database module where I keep my queries separate from my routes. It looks something like this...
var mysql = require('mysql');
var pool = mysql.createPool({
host : 'example.org',
user : 'bob',
password : 'secret'
});
exports.getUsers = function(callback) {
pool.getConnection(function(err, connection) {
if(err) {
console.log(err);
callback(true);
return;
}
var sql = "SELECT id,name FROM users";
connection.query(sql, [], function(err, results) {
connection.release(); // always put connection back in pool after last query
if(err) {
console.log(err);
callback(true);
return;
}
callback(false, results);
});
});
});
I know this is super delayed, but I've written a solution to this that I think might be a bit more generic and usable. I had written an app entirely dependent on connection.query() and switching to a pool broke those calls.
Here's my solution:
var mysql = require('mysql');
var pool = mysql.createPool({
host : 'localhost',
user : 'user',
password : 'secret',
database : 'test',
port : 3306
});
module.exports = {
query: function(){
var sql_args = [];
var args = [];
for(var i=0; i<arguments.length; i++){
args.push(arguments[i]);
}
var callback = args[args.length-1]; //last arg is callback
pool.getConnection(function(err, connection) {
if(err) {
console.log(err);
return callback(err);
}
if(args.length > 2){
sql_args = args[1];
}
connection.query(args[0], sql_args, function(err, results) {
connection.release(); // always put connection back in pool after last query
if(err){
console.log(err);
return callback(err);
}
callback(null, results);
});
});
}
};
This instantiates the pool once, then exports a method named query. Now, when connection.query() is called anywhere, it calls this method, which first grabs a connection from the pool, then passes the arguments to the connection. It has the added effect of grabbing the callback first, so it can callback any errors in grabbing a connection from the pool.
To use this, simply require it as module in place of mysql. Example:
var connection = require('../middleware/db');
function get_active_sessions(){
connection.query('Select * from `sessions` where `Active`=1 and Expires>?;', [~~(new Date()/1000)], function(err, results){
if(err){
console.log(err);
}
else{
console.log(results);
}
});
}
This looks just like the normal query, but actually opens a pool and grabs a connection from the pool in the background.
In response to #gladsocc question:
Is there a way to use pools without refactoring everything? I have
dozens of SQL queries in the app.
This is what I ended up building. It's a wrapper for the query function. It will grab the connection, do the query, then release the connection.
var pool = mysql.createPool(config.db);
exports.connection = {
query: function () {
var queryArgs = Array.prototype.slice.call(arguments),
events = [],
eventNameIndex = {};
pool.getConnection(function (err, conn) {
if (err) {
if (eventNameIndex.error) {
eventNameIndex.error();
}
}
if (conn) {
var q = conn.query.apply(conn, queryArgs);
q.on('end', function () {
conn.release();
});
events.forEach(function (args) {
q.on.apply(q, args);
});
}
});
return {
on: function (eventName, callback) {
events.push(Array.prototype.slice.call(arguments));
eventNameIndex[eventName] = callback;
return this;
}
};
}
};
And I use it like I would normally.
db.connection.query("SELECT * FROM `table` WHERE `id` = ? ", row_id)
.on('result', function (row) {
setData(row);
})
.on('error', function (err) {
callback({error: true, err: err});
});