Postgres db service wrapper

service.js

var pg = require('pg');

var Service = function (connectionConfig) {
  this.connectionConfig = connectionConfig;
  this._client = null;
  this._releaseClient = null;
  this.isConnected = false;
};

Service.prototype._connection = function (callback) {
  var self = this;

  if (this.isConnected) {
    return callback(null, this._client);
  }

  pg.connect(this.connectionConfig, function (err, client, done) {
    self._client = client;
    self._releaseClient = done;
    self.isConnected = true;
    callback(err, client);
  });
};

Service.prototyp._disconnect = function () {
  this.isConnected = false;
  this._client = null;
  this._releaseClient();
};

Service.prototy.getSomething = function (params, callback) {
  this._connection(function (err, client) {
    client.query("SELECT * FROM something", params, function (err, result) {
      if (err) {
        return callback(err);
      }
      if (result.rows.lenght === 0) {
        return callback(null, null);
      }
      return callback(null, result.rows);
    });
  });
};

module.exports = Service;