I wrote and am using this program to automatically rebuild and restart a NextJS app whenever a commit is pushed to the app’s git repo on Gitlab.

There is actually nothing specific to either Gitlab (besides the X-Gitlab-Token header in the authenticate() function) or NextJS, and the program can be modified to work with any header, and to kill any process (not only npm start) based on the port the process occupies.

Build

make build

Setup

First do a git clone of your repo on the machine where your NextJS app will run.

Edit run_webhook.sh and provide the following environment variables:

• GIT_REPO_PATH: the on-disk location of your cloned repo,
• WEBHOOK_SECRET_TOKEN: the secret token you generated on Gitlab for authorizing webhook requests,
• WEBHOOK_PORT: the port on which the webhook handler will run (default: 8000), and
• NEXTJS_PORT: the port which NextJS will use (default: 3000).

Copy run_webhook.sh and the webhook binary somewhere on the same machine where the NextJS app will run.

Execute ./webhook, possibly in tmux or screen.

Usage

Upon launch, the program performs a git pull and, if needed, will install dependencies, will build, and will finally start the NextJS app in a coroutine.

If your app has already been running, it keeps running, except if the git pull indicates that there are updates.

Each webhook request triggers a git pull. Upon that: if there are changes, the program terminates any running process occupying the specified port (default: 3000) and does the following:

1. npm install
2. npm run build, and
3. npm start in a goroutine.

Example output

$ ./run_webhook.sh
2023-12-08T00:42:54+02:00       🛋️ Performing initial setup…
2023-12-08T00:42:54+02:00       🔎 Checking whether 'npm start' is already running on port 3000
2023-12-08T00:42:54+02:00       ✅ Found PID of process running on port 3000: 14140
2023-12-08T00:42:54+02:00       🤷 The app was running already; will not update
2023-12-08T00:42:54+02:00       🚀 Starting the webhook server on port 8000
2023-12-08T00:51:07+02:00       🤝 Received a valid secret token from Gitlab
2023-12-08T00:51:07+02:00       ⚠️ 'git push' detected
2023-12-08T00:51:07+02:00       📡 Performing 'git pull'…
2023-12-08T00:51:09+02:00       ✅ 'git pull' completed
2023-12-08T00:51:09+02:00       🔃 Rebuilding required
2023-12-08T00:51:09+02:00       💣 Killing 'npm start'…
2023-12-08T00:51:09+02:00       ✅ Found PID of process running on port 3000: 14140
2023-12-08T00:51:09+02:00       💣 Killing process with PID 14140
2023-12-08T00:51:09+02:00       🛠️ Running 'npm install'…
2023-12-08T00:51:11+02:00       ✅ 'npm install' completed
2023-12-08T00:51:11+02:00       🏗️ Running 'npm run build'…
2023-12-08T00:51:40+02:00       ✅ 'npm run build' completed
2023-12-08T00:51:40+02:00       🥳 Update completed and 'npm start' issued