bluebird coroutine with node redis

Question

I'm trying to use node redis with yield and cannot find a proper way to achieve this.

Basically I want to be able to wait for the promise resolution to make my async code looks like sync code (equivalent to c# yield)

I made a simple test like this but it's not working:

const redisLib = require("redis")
const Promise = require("bluebird")

Promise.promisifyAll(redisLib)

var express = require('express'),
    redis = redisLib.createClient({ host: '127.0.0.1', port: 6379 }),

const redisGetYield = Promise.coroutine(function* (key) {
    const redis = app.get("redis")
    let val = yield redis.getAsync(key)
    return val
})

app.get("/test",function(req,res,next)
{
    let val = redisGetYield("test")
    return res.json({'val':val}).end()
})

The displayed output in my browser is :

{"val":{"isFulfilled":false,"isRejected":false}}

Looks like the yield has no effect, the code don't wait for the resolution of the promise.

I know I can use co-redis , but I want to make this with with node redis for compatibility reasons.

Answer 1

Here is a solution that uses Node 8's promisify. With it, you would not need bluebird coroutine:

const Promise = require("bluebird")
const redis = Promise.promisifyAll(require('redis'))
const express = require('express'),

let client = redis.createClient({ 
  host: '127.0.0.1', port: 6379 
}));

app.get('/test', async (req, res, next) => {
    let val = await client.get('test');
    return res.json({ val }).end();
});

Async/await is an extremely powerful JavaScript feature. And with it, I find myself rarely using promises explicitly.

Note: In a production app, make sure to surround all async calls in a try catch block to catch rejected promises.

Note 2: I misspoke above. You will still need to use promisifyAll in bluebird. Node 8 has a promisify function, but I forgot that it only works on a single function at a time.