Check if redis is running -> node js

Question

I just wanted to know, at the beginning of my NodeJS process, if Redis is started or not (so users session will be stored or not).

Here is what I have for the moment :

var session = require('express-session');
var RedisStore = require('connect-redis')(session);
var redis = require("redis");
var client = redis.createClient(global.redis.host, global.redis.port);

// Check if redis is running
var redisIsReady = false;
client.on('error', function(err) {
    redisIsReady = false;
    console.log('redis is not running');
    console.log(err);
});
client.on('ready', function() {
    redisIsReady = true;
    console.log('redis is running');
});

// Here I use express-session, but I want to set a store only if redis is ready
    sessOptions = {
        [...]
    }
    // Store setting
    if (redisIsReady) {
        sessOptions.store = new RedisStore({
            host: global.redis.host,
            port: global.redis.port
        });
    } else {
        console.log("redis is not running - sessions won't be written to disk");
    }
// app.use(session(sessOptions))

Here is what it's output in both cases (when Redis is running or not) :

redis is not running - sessions won't be written to disk
redis is not running
Error: Redis connection to 6379:localhost failed - connect ENOENT

---

So I have 2 questions :

1. How can I do to check if redis is running before setting my SessionStore (is there anyway to check synchronously if redis is running) ?

2. Why does it giving me an error even when redis is running ?

THANKS!

---

Note : I'm using default host/port (localhost, 6379) and the RedisStore works as expected.

Note 2 : I'm using Windows... but don't be affraid, it should have the same behavior!

Update : Question #2 answered by vmx => Thanks!

Update 2 : Question #1 answered by Nathan => Thanks!

Answer 1

How I have done this in the past is in between setting up the redis connection via

var client = redis.createClient(global.redis.port, global.redis.host);

and actually starting my application, whether that be express or a custom app, I just do a very simple query, such as:

client.get(this.testKey, function(err,res) {
  if(err) 
    throw err;

  if(res === expectedValue)
    return startApp();
});

Essentially just put the code to start your app inside of the callback to a redis query, and you will then know if redis is running based on the result.