Passing Redis Key-value in Routes in Node.js / Express

Question

Passing Redis Key-value in Routes in Node.js / Express

This is similar to this question, but my code has multiple routes.

The code works below for what I want to do, but I want to know if there's a cleaner way to write it as I'm fairly new to Node/Express/Redis.

var express = require('express');
var router = express.Router();
var io = require('socket.io');
var redis = require('./../lib/redis');

redis.get('count', function(err, value) {
    if(err) throw err;

    /* GET Dashboard */
    router.get('/', function(req, res) {
      res.render('dashboard', {title: 'Data Dashboard', count: value });
    });

    /* GET Backend */
    router.get('/backend', function(req, res) {
      res.render('backend', {title: 'Backend', count: value });
    });
});

module.exports = router;

Basically, I'm just passing a single Redis key-value to both of my routes. Any suggestions to clean it up are appreciated.

node.js
express
redis

Answer 1

The way your code is written you'll be passing the same value of the count key for your whole application life-cycle. There's nothing wrong with the code from a cleaning up perspective, but from a service point of view, the routes shouldn't be within the REDIS GET callback.

Getting the value within the route

// Use everytime you need to count the key
function redisCount = function(callback) {
    redis.get('count', function(err, value) {
      if(err) callback(err)
      callback(null, value)
    }
}

/* GET Dashboard */
router.get('/', function(req, res) {
  redisCount(function(err,value) {
    if(err) throw err;
    res.render('dashboard', {title: 'Data Dashboard', count: value });
  })
});

/* GET Backend */
router.get('/backend', function(req, res) {
  redisCount(function(err,value) {
    if(err) throw err;
    res.render('backend', {title: 'Backend', count: value });
  })
});

However if you do this count call for absolutely every single route, I would suggest a piece of middleware that just sets value into the context for every call:

Getting the value in a separate middleware

app.use(function (req, res, next) {
  // using the same function for the redis count
  redisCount(function(err, value) {

    // respond with error
    if (err) res.status("Could not connect to Redis")

    // otherwise set the value in the session
    req.session.value = value

    // and move on to the next middleware
    next()

  });
});

// now simply declare your routes

/* GET Dashboard */
router.get('/', function(req, res) {
  res.render('dashboard', {title: 'Data Dashboard', count: req.session.value });
});

/* GET Backend */
router.get('/backend', function(req, res) {
   res.render('backend', {title: 'Backend', count: req.session.value });
});