RPLB – Reverse Proxy Load Balancer

Load balance requests based on configured hostname across configured backends. It is primarily meant to be used for learning purposes in a home lab environment.

Read more on Reverse Proxy and Load Balancing.

Related blog post

https://developerschallenges.com/2024/12/09/my-latest-side-project-—-rplb/

Features

• ⚙️ Simple configuration
  • In-line
• ⚡️ Load Balancing
  • Least-Loaded Round Robin
  • Sticky Round Robin
  • Round Robin
  • Random
  • First
• 💪 Resiliency
  • Retries
• 📈 Dashboard
  • Monitor
  • Traffic
• 🧪 Instrumentation
  • /metrics endpoint

Getting started

CLI

Usage of rplb:
  -a string
        Algorithm used for load balancing. Choose from: first, random, roundrobin, sticky or leastloaded. (default "sticky")
  -b string
        Comma-separated list of BackendPool Name and URL pairs. (example "backend,http://10.0.0.1:1234")
  -f string
        Comma-separated list of Frontend Hostname and BackendPool Name pairs. (example "frontend.example.com,backend")

Docker

You can run RPLB with these commands:

docker pull ghcr.io/dalibormesaric/rplb:latest

docker run -d --restart=always -p 8000:8000 -p 8080:8080 -e RPLB_A=roundrobin -e RPLB_F=myapp.example.com,myapp -e RPLB_B=myapp,http://10.0.0.1:1234,myapp,http://10.0.0.2:1234,myapp,http://10.0.0.3:1234 --memory="64m" --memory-reservation="64m" --cpus="1" ghcr.io/dalibormesaric/rplb:latest

Configuration

RPLB_A=roundrobin

• roundrobin is the name of one of the load balancing algorithms

RPLB_F=myapp.example.com,myapp

• myapp.example.com is hostname where RPLB is running, so in this case you would access your backend via http://myapp.example.com:8080 and the Dashboard via http://myapp.example.com:8000
• myapp is name of the Backend Pool that this hostname is connected to

RPLB_B=myapp,http://10.0.0.1:1234,myapp,http://10.0.0.2:1234,myapp,http://10.0.0.3:1234

• myapp is name of the Backend Pool to which the URL is assigned
• http://10.0.0.1:1234, http://10.0.0.2:1234 and http://10.0.0.3:1234 are the URLs of your application

Home Assistant

To run custom docker images, use Advanced SSH & Web Terminal from Community Add-ons.

To resolve custom domains on the same IP where Home Assistant is running, use AdGuard Home and its feature DNS rewrites.

Try it out

Example

There is an /example folder in this repository containing already configured RPLB with tree backends. You can try it our by running:

RPLB_A=first docker compose -f example/compose.yaml up rplb --build

for i in {1..10}; do curl -s localhost:8080 | grep \<h1; sleep 1; done;

docker compose -f example/compose.yaml down

Least-Loaded Round Robin

RPLB_A=leastloaded docker compose -f example/leastloaded/compose.yaml up rplb --build

seq 1000 | parallel -n0 -j8 "curl -s http://localhost:8080 | grep Response"

docker compose -f example/leastloaded/compose.yaml down

Development

Version using Git Tags

git tag

git tag v0.1

git push origin v0.1

go run -ldflags "-X github.com/dalibormesaric/rplb/internal/config.Version=$(git describe --tags --abbrev=0)" cmd/rplb/main.go

docker build --build-arg="VERSION=$(git describe --tags --abbrev=0)" -t rplb .

Build Pipeline

• https://github.com/docker/setup-buildx-action

Testing

go test ./... -count=1

Instrumentation

Using https://prometheus.io/docs/guides/go-application/.

Exposing custom metrics.

What is this?

With this project I wanted to have two things:

1. A simple way to load balance traffic between bare metal kubernetes cluster nodes
2. A fun Go project to work on

Misc

Tools used

• https://coolors.co/palette/ef476f-ffd166-06d6a0
• https://cssgradient.io/

TODO:

• dashboard page title per page (Monitor - RPLB)
• docs
• algorithm state expiration?

Some ideas

• https://stackoverflow.com/questions/37321760/how-to-set-up-lets-encrypt-for-a-go-server-application
• https://stackoverflow.com/questions/23439126/how-to-mount-a-host-directory-in-a-docker-container
• https://bazel-contrib.github.io/SIG-rules-authors/go-tutorial.html
• https://stackoverflow.com/questions/16512840/get-domain-name-from-ip-address-in-go
• https://stackoverflow.com/questions/70442770/infinite-scrolling-carousel-css-only