Data returned from promises with AWS-SDK for node and bluebird - node.js

Question

I'm trying to fetch for each region in AWS all their Elastic IPs registered. The piece of code that I'm currently handling is the following:
logger.info('About to fetch Regions');
ec2.describeRegionsPromised({}).then(function (data) {
var addressesPromises = [];
logger.info('Fetched Regions');
logger.info(data);
_.forEach(data.Regions, function (region) {
var ec2Addresses = _.create(ec2, {region: region.RegionName});
addressesPromises.push(ec2Addresses.describeAddressesPromised());
});
logger.info('About to fetch addresses per region');
return Promise.all(addressesPromises);
}).then(function (data) {
logger.info('Fetched addresses per region');
logger.debug(data);
}).catch(function (err) {
logger.error('There was an error when fetching regions and addresses');
logger.error(err);
});
This works ok, but my problem is that I'm looking at the second .then promised-callback function data parameter and its data is an array with the same length of the regions returned on the first request.
I know that I'm only using 1 Elastic IP in one region. For alll the other regions I don't have any associated.
The Regions returned are the following (it's actually a formatted JSON):
Regions=[RegionName=eu-west-1, Endpoint=ec2.eu-west-1.amazonaws.com, RegionName=ap-southeast-1, Endpoint=ec2.ap-southeast-1.amazonaws.com, RegionName=ap-southeast-2, Endpoint=ec2.ap-southeast-2.amazonaws.com, RegionName=eu-central-1, Endpoint=ec2.eu-central-1.amazonaws.com, RegionName=ap-northeast-1, Endpoint=ec2.ap-northeast-1.amazonaws.com, RegionName=us-east-1, Endpoint=ec2.us-east-1.amazonaws.com, RegionName=sa-east-1, Endpoint=ec2.sa-east-1.amazonaws.com, RegionName=us-west-1, Endpoint=ec2.us-west-1.amazonaws.com, RegionName=us-west-2, Endpoint=ec2.us-west-2.amazonaws.com]
In JSON it would be:
{ Regions: [] } //and so on
And the Elastic IP returned are the following:
[ { Addresses: [ [PublicIp=XX.XX.XXX.XXX, AllocationId=eipalloc-XXXXXXXX, Domain=vpc] ] },
{ Addresses: [ [PublicIp=XX.XX.XXX.XXX, AllocationId=eipalloc-XXXXXXXX, Domain=vpc] ] },
{ Addresses: [ [PublicIp=XX.XX.XXX.XXX, AllocationId=eipalloc-XXXXXXXX, Domain=vpc] ] },
{ Addresses: [ [PublicIp=XX.XX.XXX.XXX, AllocationId=eipalloc-XXXXXXXX, Domain=vpc] ] },
{ Addresses: [ [PublicIp=XX.XX.XXX.XXX, AllocationId=eipalloc-XXXXXXXX, Domain=vpc] ] },
{ Addresses: [ [PublicIp=XX.XX.XXX.XXX, AllocationId=eipalloc-XXXXXXXX, Domain=vpc] ] },
{ Addresses: [ [PublicIp=XX.XX.XXX.XXX, AllocationId=eipalloc-XXXXXXXX, Domain=vpc] ] },
{ Addresses: [ [PublicIp=XX.XX.XXX.XXX, AllocationId=eipalloc-XXXXXXXX, Domain=vpc] ] },
{ Addresses: [ [PublicIp=XX.XX.XXX.XXX, AllocationId=eipalloc-XXXXXXXX, Domain=vpc] ] } ]
On the response, I have an array of objects where their object key-values are all the same per each region request, which is false.
I would have expected in the second response the values resolution per each region, having the rest of them set to null, undefined, or similar.
To sum up. I don't get why resolving the values of an array of promises (using .all) will get an array of identical values in each spot - not being the expected result.
What's going on here? Thanks in advance!

Answer 1

I found the issue.
As #Roamer-1888 indicated the creation of the ec2Addresses object was incorrect. Instead, I should have created a new instance using the AWS SDK constructor for EC2 objects. However, the key-point of the issue was another one. Firstly the code...
logger.info('About to fetch Regions');
ec2.describeRegionsPromised({}).then(function (data) {
var addressesPromises = [];
logger.info('Fetched Regions');
_.forEach(data.Regions, function (region) {
var ec2Addresses = AWS.ec2(
{
region: region.RegionName,
endpoint: region.Endpoint
}
);
addressesPromises.push(ec2Addresses.describeAddressesPromised());
});
logger.info('About to fetch addresses per region');
return Promise.all(addressesPromises);
}).then(function (data) {
logger.info(arguments);
logger.info('Fetched addresses per region');
logger.debug(data);
}).catch(function (err) {
logger.error('There was an error when fetching regions and addresses');
logger.error(err);
});
As you can notice here, ec2Addresses is created invoking AWS.ec2() and not new AWS.ec2(), this is because the AWS-promised module creates the object and return it back promisifying it. (https://github.com/davidpelayo/aws-promised/blob/master/ecs.js):
'use strict';
var AWS = require('aws-sdk');
var memoize = require('lodash/function/memoize');
var promisifyAll = require('./lib/util/promisifyAll');
function ecs(options) {
return promisifyAll(new AWS.ECS(options));
}
/**
* Returns an instance of AWS.ECS which has Promise methods
* suffixed by "Promised"
*
* e.g.
* createService => createServicePromised
*
* #param options
*/
module.exports = memoize(ecs);
The issue was the last line of code:
module.exports = memoize(ecs)
This line of code was caching the previous execution including its previous configuration.
It turns out I ended up debugging the application and I realise the regions and endpoints were the array of promises were being executed were the same, and there was an error there.
By deleting the memoize(ecs) the expected result is the one I'm getting:
info: Fetched addresses per region
debug: Addresses=[], Addresses=[], Addresses=[], Addresses=[], Addresses=[], Addresses=[PublicIp=XX.XXX.XXX.XXX, AllocationId=eipalloc-XXXXXX, Domain=vpc], Addresses=[], Addresses=[], Addresses=[]
Thanks for reading and helping.

Answer 2

I found out a way of requesting addresses of different regions without creating a new EC2 object. In other words, by reusing the existing EC2 instance, by switching the endpoint like follows:
_.forEach(data.Regions, function (region) {
//var ec2Addresses = AWS.ec2(
// {
// region: region.RegionName,
// endpoint: region.Endpoint
// }
//);
var ep = new AWS.Endpoint(region.Endpoint);
ec2.config.region = region.RegionName;
ec2.endpoint = ep;
addressesPromises.push(ec2.describeAddressesPromised());
});
logger.info('About to fetch addresses per region');