node-redis promisification using bluebird - node.js

Question

I'm trying to use promises with node-redis package, but I can't use on.connect() method.
var redis = require("redis");
var client = redis.createClient();
bluebird.promisifyAll(redis.RedisClient.prototype);
bluebird.promisifyAll(redis.Multi.prototype);
// callback version
app.get('/redis', function(req, res) {
client.set("foo_rand000000000000", "some fantastic value", function(err, reply) {
if (err) {
console.log(err);
} else {
console.log(reply);
}
res.end();
});
});
// promisified version
app.get('/redis', function(req, res) {
return client.setAsync("foo_rand000000000000", "some fantastic value").then(function(return) {
console.log(return); // returns OK
client.quit();
});
});
But I am stuck with the one below, how can I promisify it?
// example
client.on("connect", function () {
client.set("foo_rand000000000000", "some fantastic value", redis.print);
client.get("foo_rand000000000000", redis.print);
});
I tried the one below but it doesn't work, I can't see the response on the command line:
app.get('/redis', function(req, res) {
return client.onAsync("connect").then(function(res) {
console.log(res);
res.end();
});
});

Answer 1

like Freyday siad, on is not async method, but an event emitter, so I would strongly discourage you from promisfying it, but hey, if you are insistant you could do something like:
let _connectResolve, _connectReject, onConnected = new Promise((resolve, reject) => {
_connectResolve = resolve;
_connectReject = reject;
}), redis = require("redis"),
client = redis.createClient();
client.on('connect', _connectResolve);
// usage example:
onConnected.then(() => {
client.setAsync("foo_rand000000000000", "some fantastic value").then(redis.print);
client.getAsync("foo_rand000000000000").then(redis.print);
});
if your worry is, you have to wait for client to connect before you get/ set stuff, you can chain all your calls to onConnected promise. e.g:
app.get('/redis', (req, res) => {
onConnected
.then(() => client.setAsync("foo_rand000000000000", "some fantastic value"))
.then(() => res.end());
});

Answer 2

The client.on() method is coming from the EventEmitter prototype which the redis client likely inherits from. You could try to walk the prototype chain and promisify it as well, but I'd probably just handle it myself like this:
function onConnect(client) {
return new Promise(function(resolve, reject) {
client.on('connect', function(err) {
if (err) return reject(err)
return resolve()
})
})
}
Then you'll be able to use it like this:
app.get('/redis', function(req, res) {
return onConnect(client)
.then(function() {
return client.setAsync("foo_rand000000000000", "some fantastic value")
})
.then(function(result) {
console.log(result); // returns OK
client.quit();
res.end();
});
});
});