Announcement Proxy

A small reverse proxy that shows an announcement page to users before letting them through to the target application. Once acknowledged, a cookie is stored in the user's browser so the announcement isn't shown again.

Requests without a browser-like User-Agent (e.g. API clients, health checks) skip the announcement and are proxied straight through.

How it works

1. A browser request comes in without the acknowledgement cookie set.
2. The proxy responds with an announcement page instead of forwarding the request.
3. The user submits the acknowledgement form (POST /acknowledge), which sets a cookie and redirects back to the referring page.
4. On subsequent requests, the cookie is present, so the proxy forwards traffic to TARGET_BASE_URL via http-proxy.

Environment variables

Variable	Description	Default
PORT	Port the server listens on	3000
TARGET_BASE_URL	Base URL of the application being proxied to	required — the server refuses to start without it
ANNOUNCEMENT	Message displayed on the announcement page	No anouncement message provided
COOKIE_NAME	Name of the cookie used to track acknowledgement	anouncement_aknowledged
COOKIE_MAX_AGE_DAYS	Number of days the acknowledgement cookie lasts	365

A .env file may be used to set these locally (see dotenv).

Running locally

npm install
npm run dev

Building and running

npm install
npm run build
npm run start

Docker

docker build -t announcement-proxy .
docker run -p 3000:3000 \
  -e TARGET_BASE_URL=https://example.com \
  -e ANNOUNCEMENT="Scheduled maintenance this weekend" \
  announcement-proxy