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express-myconnection

Connect/Express middleware provides a consistent API for MySQL connections during request/response life cycle. It supports three different strategies of managing db connections: single for a singleton connection on an app instance level, pool based connections, and a new connection per each request. It’s also capable of auto closing/releasing connections if configured either with pool or request. It uses node-mysql as a MySQL driver.

Strategies

• single - creates single database connection for an application instance. Connection is never closed. In case of disconnection it will try to reconnect again as described in node-mysql docs.
• pool - creates pool of connections on an app instance level, and serves a single connection from pool per request. The connections is auto released to the pool at the response end.
• request - creates new connection per each request, and automatically closes it at the response end.

Usage

Configuration is straightforward and you use it as any other middleware. First param it accepts is a node-mysql module, second is a db options hash passed to node-mysql module when connection or pool are created. The third is string defining strategy type.

// app.js
...
var mysql = require('mysql'), // node-mysql module
    myConnection = require('express-myconnection'), // express-myconnection module
    dbOptions = {
      host: 'localhost',
      user: 'dbuser',
      password: 'password',
      port: 3306,
      database: 'mydb'
    };
  
app.use(myConnection(mysql, dbOptions, 'single'));
...

express-myconnection extends request object with getConection(callback) function, this way connection instance can be accessed anywhere in routers during request/response life cycle:

// myroute.js
...
module.exports = function(req, res, next) {
    ...
    req.getConnection(function(err, connection) {
      if (err) return next(err);
      
      connection.query('SELECT 1 AS RESULT', [], function(err, results) {
        if (err) return next(err);
        
        results[0].RESULT;
        // -> 1
        
        res.send(200);
      });
      
    });
    ...
}
...

release connection use req.releaseConnection to manual release a connection // myroute.js ... module.exports = function(req, res, next) { ... req.getConnection(function(err, connection) { if (err) return next(err); connection.query('SELECT 1 AS RESULT', [], function(err, results) { connection = null; req.releaseConnection(); //manual to release a connection if (err) return next(err); results[0].RESULT; // -> 1 requestUrl(url, function(err, data) { if (err) return next(err); req.getConnection(function(err, connection) { //get a connection again connection.query('SELECT 2 AS RESULT', [], function(err, results) { res.send(200); }); }); }) });

  });
  ...
}
...