Why does sequelize create new connection for each query?

It seems, sequelize creates new connection for each query instead of using existing ones from pool.

What you are doing?

I’m sending sleep queries in every two seconds.

var sequelize = new Sequelize(options.database, options.user, options.password, {
    host: options.host,
    dialect: 'mysql',
    port: options.port,
    pool: {
        max: 10,
        min: 2,
        idle: 10000
    }
});

setInterval(function () {
    sequelize.query('SELECT SLEEP(1);');
}, 2000);

What do you expect to happen?

I would except all these queries to get the same connection from the pool

What is actually happening?

When I check the mysql processes, I see different connection ids for each sleep query.

| 12973820 | admin         | 10.179.195.173:34544 | FieldServices | Query   |    0 | User sleep | SELECT SLEEP(1)  |         0 |             0 |

| 12973822 | admin         | 10.179.195.173:34545 | FieldServices | Query   |    0 | User sleep | SELECT SLEEP(1)  |         0 |             0 |

| 12973818 | admin         | 10.179.195.173:34545 | FieldServices | Query   |    1 | User sleep | SELECT SLEEP(1)  |         0 |             0 |

But when I use default mysql pool, all my queries use the same connection:

var mysql = require('mysql');
var pool  = mysql.createPool({
    connectionLimit : 10,
    host            : !options.tunnel ? options.host : "127.0.0.1",
    user            : options.user,
    password        : options.password,
    database        : options.database,
    port: !options.tunnel ? options.port : config.get('tunnel.' + options.tunnel).localPort,
});

setInterval(function () {
    pool.query('SELECT SLEEP(1);', function (err, rows, fields) {
        if (err) throw err;
        console.log('sleep');
    });
}, 2000);

| 12975966 | admin         | 10.179.195.173:36196 | FieldServices | Query   |    1 | User sleep | SELECT SLEEP(1)  |         0 |             0 |

| 12975966 | admin         | 10.179.195.173:36196 | FieldServices | Query   |    0 | User sleep | SELECT SLEEP(1)  |         0 |             0 |

| 12975966 | admin         | 10.179.195.173:36196 | FieldServices | Query   |    0 | User sleep | SELECT SLEEP(1)  |         0 |             0 |

Dialect: mysql Database version: 5.5.40 Sequelize version: 4.0.0-1

[felixfbecker]

Connections are cycled round-robin style, so it’s not always connection A that gets 90% of the queries while connection B, C, D idle mostly.

[felixfbecker]

Imo tracking bugs for drivers and printing bugs for every version is out of scope for sequelize. The first thing you should do when you encounter a bug is npm update 😃