Node LB

A basic HTTP Load Balancer built on Express.js

The Load Balancer

• Based on Express.js as the server framework
• Get requests are balanced with a round-robin method, using rocky proxy (https://github.com/h2non/rocky)
• Post requests are forwarded to All servers, returning response from first server available
• If one of the servers is unavailable during the post request, an infinite retries will be conducted, using an exponential back-off interval - with the help of request-retry module and custom code (https://github.com/FGRibreau/node-request-retry)
• Metrics are exposed for Prometheus using prom-client (https://github.com/siimon/prom-client) and are available at /metrics endpoint

Prerequisites

• Node.js (This was developed and tested on version 8, so use that please :))
• Python 3 for the testing-listener webserver

How to use?

• Clone the repo
• Set the config file located at config/default.json:
  • port: The port the load-balancer should listen on
  • serversList: A backend servers array (See example inside attached config file)
  • postEndpoints - Endpoints for load balancer POST method, seperated by PIPE (See example inside the config file)
  • getEndpoints - Same as post endpoints, just for GET method
• Eventually - Run with: npm start

How to test?

• Inside the Tester folder there is a simple python web server, you can use that or any other backend servers you'd like:
  • Cd into the Tester folder
  • Run with: python3 SimpleWebServer.py
  • Run as many instances as you want to test(using different ports of course)
  • Those instances to be included in the serversList inside the config file
  • Use POSTMAN or any other utility/software to test the get/post requests to the LB
  • Check the node terminal & the web servers terminals to make sure requests were successful

TODO

• Multiple Ports/Listeners
• Make app is more configurable from config file and not code
• Show nicer errors when reaching wrong endpoint (move debug to production)
• Show spinner on retrying post
• Implement some kind of multicast http in the forwarding method instead of sequential loop (if possible)
• Make testing easier - One console with many ports, send all results to one console/log file
• Config validation
• Dockerize