tomashubelbauer/bun-reverse-proxy

Bun reverse proxy

Bun Reverse Proxy

This repository intends to demonstrate using Bun as a reverse proxy and binding it to port 80 so that multiple other services running at their own ports can be accessed via a plain host name.

The idea is that the Bun reverse proxy binds to port 80 and it keeps a list of services and their corresponding ports that are running on the same macOS system and those services also have their own corresponding /etc/hosts entries all being mapped to the loopback address.

/etc/hosts:

127.0.0.1 service1.localhost # 7001
127.0.0.1 service2.localhost # 7002

The /etc/hosts file can be edited by running sudo code /etc/hosts. The file requires sudo for writing (it can be read without it), but VS Code recognizes this and will offer to retry with sudo when saving.

I am opting to use the end of line comments in the hosts file as the "database" of services for the Bun reverse proxy to discover so there is a single source of truth and not two places that can go out of sync (the hosts file for the mapping to loopback and whatever other mechanism would there be for the reverse proxy to map the host names to port names on localhost).

When the user accesses service1.localhost or service2.localhost in their browser, the reverse proxy will intercept the request (being bound to port 80, the default for HTTP) and will inspect the host name to see what address to forward the request to and proxy the response for.

They all use the *.localhost TLD so they are treated as a secure context by the browser and do not need an HTTPS certificate to use modern web features. https://developer.mozilla.org/en-US/docs/Web/Security/Secure_Contexts

I have added sample service1 and service2 directories for quick testing. Those services can be started by cd service# followed by bun ..

VS Code Integrated Terminal allows doing multiple ones to run these in parallel.

Bun is used because it has a nice built-in HTTP API unlike Node.

In development, run the reverse proxy using bun --hot run .. In "production" (running it in the background on the computer), build it and run the executable and detach: bun build . --compile --outfile reverse-proxy and then ./reverse-proxy &.

If the "production" instance is already running, bun run will fail to start because the server will fail to bind to the already taken port 80. Kill the "production" instance first using pkill reverse-proxy.

I have extracted this command to the start package script so it can be run using bun start.

There is also bun run build for making and starting the "production" instance.

The same way, the "production" instance won't run if the development one is bound to the port 80, so treat running the development instance and building and running the "production" instance as mutually exclusive.

With this setup, it is possible to run several custom local applications each on its own port but access them via user-friendly names and do it using super small tooling (just Bun and the compiled reverse proxy binary) and standard approaches (the hosts file).