How to use Bluebird promisification with generators + parallel promises - arrays

Question

Trying to fire off mutiple requests off to the beats api using bluebird as well as koa for generators.
After reading some documentation I figured the following would work
var request = require('co-request'),
_ = require('lodash'),
Promise = require('bluebird');
request = Promise.promisifyAll(request);
module.exports.getTracks = function *tracks(){
firstCall = yield makeAPICall('users/' + me + '/mymusic/tracks?limit=150');
total = firstCall.body.info.total;
total -= 150;
tracks = firstCall.body.data;
//Beats only allows a maximum of 150 tracks per call
//If more tracks are needed then the remainder is called in sets of 150
var offset = 150;
while (total > 0) {
promises.push(makeAPICall('users/' + me + '/mymusic/tracks?limit=150&offset=' + offset));
offset += 150;
total -= 150;
}
var responses = yield(Promise.all(promises));
}
function makeAPICall (query){
var authOptions = {
url: 'https://partner.api.beatsmusic.com/v1/api/' + query,
headers: { 'Authorization': 'Bearer ' + accessToken },
json: true
};
return request.get(authOptions);
}
The method makeAPI call works as expected used with firstCall, but for some reason when I start placing the makeAPICall method into the array they never seem to execute. The variable responses yields out just an array of functions instead of an array of responses from the beats api. What do I need to change to make responses return an array of objects similar to that of firstCall?

Answer 1

Your using co-request which already converts callbacks to thunks, so there is no need to try and promisify things.
Here is a simplified runnable example, similar to your code, showing how to run api calls in parallel with Koa (which uses co under the hood).
When you yield an array, co will run any thunks/promises/generators etc in parallel.
var request = require('co-request'),
co = require('co');
co(function *(){
var results = yield getTracks();
results.forEach(function(result){
console.log(result.body);
})
}).then();
function * getTracks () {
var queries = [];
// swap out your queries here
queries.push(makeAPICall('5185415ba171ea3a00704eed'));
queries.push(makeAPICall('54fdc3c9862a3aab01dc95cf'));
queries.push(makeAPICall('54fdc3da862a3aa501dc95d0'));
// yielding an array returns an array of results
var results = yield queries;
return results;
}
function makeAPICall (query) {
var options = {
url: 'http://www.mocky.io/v2/' + query,
json: true
}
return request.get(options)
}