How to properly use node-mysql? - mysql

Question

I just started using node-mysql2 and I am confused how to use it properly. Examples:
(Implicitly established connection)
var express = require("express"),
app = express();
var mysql = require("mysql2");
var conn = mysql.createConnection({ ... });
app.VERB("/", function(req, res){
conn.query('SELECT 1+1 as test1', function(err, rows) {
// Show data to user...
// No .end() needed?
});
});
app.listen(8000);
second example:
var express = require("express"),
app = express();
var mysql = require("mysql2");
var conn = mysql.createConnection({ ... });
conn.connect(function(err){ ... }); // Is it right place to put it here? Or it has to go inside the callback below?
app.VERB("/", function(req, res){
conn.query("SELECT 1+1 as test1", function(err, rows){
// Show data to user...
conn.end(); // .end() necessary?
});
});
app.listen(8000);

Answer 1

Although I haven’t used node-mysql2, it is compatible with the original node-mysql module, so the same usage patterns apply.
The best way to use it is with connection pooling. That way, the MySQL client will create and destroy connections as needed. Your job is to call connection.release() when you no longer need a connection:
var express = require("express"),
app = express();
var mysql = require("mysql2");
var pool = mysql.createPool({ ... });
app.VERB("/", function(req, res){
pool.getConnection(function(err, conn) {
if (err) { /* handle the error and bail out */ }
conn.query('SELECT 1+1 as test1', function(err, rows) {
conn.release(); /* the connection is released back to the pool */
if (err) { /* handle the error */ }
else { /* show data to user */ }
});
});
});
app.listen(8000);
If your app runs “forever” (a web site for example) then you don’t need to call pool.end(). If you’re not using a connection pool, you don’t need to call connection.end() after each request. You wouldn’t want to: that would give you the overhead of establishing/tearing down the MySQL connection on every request!
If your app does not run “forever” (a command-line utility, for example), then call pool.end() or connection.end() just before you exit back to the command-line.