make nginx redirect to random port - node.js

Question

I'm working on setting up a load balancer for my website. I want to do it manually so that I have full control over how the requests are rerouted. Im using AWS EBS to load balance between 2 ec2 instances, and that works fine. Each ec2 instance uses nginx as a reverse proxy for nodejs.
Currently, I only have 1 node app running on each server, but Ideally I would like to have 4 node apps on each server (1 for each core).
I was thinking that a really easy way to manage this would be to allow nginx to pick a random port between 8081, and 8084 and redirect to one of the apps. In theory this way I would be balancing the load as evenly as possible.
Currently this is my nginx reverse proxy set up:
server {
client_max_body_size 200M;
listen 80 default_server;
listen [::]:80 default_server;
server_name _;
location / {
client_max_body_size 200M;
proxy_pass http://localhost:8080;
proxy_http_version 1.1;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header Real-User-Agent $http_user_agent;
proxy_set_header Connection 'upgrade';
proxy_set_header X-serv-ip 'my.server.ip';
proxy_set_header Host $host;
proxy_cache_bypass $http_upgrade;
}
}
Basically, my question boils down to if there's some way to make a variable like $rand_port and every time a request is made, $rand_port is set to 8081, 8082, 8083, or 8084, and then in my proxy_pass I could do something like:
proxy_pass http://localhost:{$rand_port} #not sure if the syntax is right.
Is there anything that lets me do something like this, or otherwise what other solutions are there?

Answer 1

nginx load balancing allows you to determine the algorithm ... if you just need each server to be equally loaded use this
upstream myproject {
server 127.0.0.1:8081;
server 127.0.0.1:8082;
server 127.0.0.1:8083;
server 127.0.0.1:8084;
}
server {
client_max_body_size 200M;
listen 80 default_server;
listen [::]:80 default_server;
server_name _;
location / {
client_max_body_size 200M;
proxy_pass http://myproject;
proxy_http_version 1.1;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header Real-User-Agent $http_user_agent;
proxy_set_header Connection 'upgrade';
proxy_set_header X-serv-ip 'my.server.ip';
proxy_set_header Host $host;
proxy_cache_bypass $http_upgrade;
}
}