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Node.js application requirements

A Node.js application must fulfill several requirements before it can run successfully on VIP’s infrastructure. The Node.js skeleton starter repository includes example applications that fulfill all of these requirements.

Restarts are handled automatically for production deployments and process monitors (e.g., nodemon or PM2) are not needed.

Health check endpoint

All Node.js applications must implement the health check endpoint using application code. The VIP Platform sends frequent health checks at this endpoint: /cache-healthcheck?.

Production dependencies

Node.js applications on the VIP Platform must use npm to manage their dependencies. Use VIP-CLI to manage environment variables that need to be present when building and running the application.

VIP uses the dependencies and scripts defined in package.json to install, build, and start an application. Make sure all necessary packages needed for an application to run are publicly accessible and are added as dependencies and not devDependencies.

Only production dependencies are installed:

npm install --production

The build script allows a Node.js application to be compiled or perform any necessary tasks before being started. Even if an app does not require a build step, it is still expected that this script to be present. Use "build": "echo 'No build'" or equivalent to fulfill this requirement. The build script must complete successfully (exit with 0).

npm run build

After a successful build, VIP will start an app using the start script. Not all frameworks supply a start script, so Node.js applications must define one manually.

npm start

Dynamic PORT

VIP assigns a dynamic port to applications using the PORT environment variable. An application needs to start on the assigned port to work correctly.

If an application’s port is declared in code, use process.env.PORT to access the assigned port. Add logic to fall back to a default port if no port is assigned (i.e., in local development):

const PORT = process.env.PORT || 3000;

If an application’s port is defined in the start script in package.json, access the assigned port using $PORT:

"start": "frontity serve --port $PORT"

Stateless, immutable, and multi-container

All Node.js applications on VIP must be able to run across multiple containers and processes simultaneously. This means that each deployment of a Node.js application must be stateless and immutable. An application must not rely on absolute paths.

The file system in the container is read-only. Files can be stored temporarily in a temp directory. Instead of hardcoding /tmp/ to access those files, use os.tmpdir().  

If any data is stored in memory, it will be lost on deployment or when containers are added or removed.

Data can be persisted elsewhere (e.g., in a WordPress application via the REST API or GraphQL). If cache data is needed for later reuse, Redis can be deployed alongside the Node.js application.

Last updated: December 23, 2023

Relevant to

  • Node.js