julie-ng / hello-welt

Simple containerized Node.js app for demos.

Hello Welt

Simple Hello World Fastify Node.js app with JSON based logging incl. log levels, graceful shutdown, readiness probes and built-in crash triggers, etc. for container orchestration demos.

   

Configuration

The following variables can be configured

Environment Variable	Default
VERSION	Version from package.json
HELLO_GREETING	Hello
HELLO_NAME	Welt
HELLO_COLOR	#ff5757
EARTH_COLOR	#57ffd1
PORT	3000
HOST	localhost in development and 0.0.0.0 in production

Demo

This image can be used to demo the following for learning about container orchestration.

Note

These demo routes use z-pages covention based on Google's internal practices to indicate that these endpoints are not part of the app's expected functionality.

Best Practices

Best Practice	Route	Description
Health Check	/healthz	Health check page with info for debugging. Returns 200.
Graceful Shutdown	N/A	See app/server.js, which responds to SIGINT and SIGTERM to shutdown database, etc.

Problems

Problem	Route	Description
Error 500	/failz	Returns 500 response and logs error to stdout. App continunes to run.
Crash	/crashz	Simulate a crash. App needs to be restarted.
Memory Leak	/slowz	Simulate a memory leak. App continues to function.

Usage

Pull from Docker Hub

Pull the julieio/hello public image from Docker Hub and then run it:

docker pull julieio/hello:latest
docker run -p 3000:3000 julieio/hello:latest

Optionally - pass configuration via environment variables:

docker run -p 3000:3000 -e HELLO_NAME=Julie julieio/hello:latest

or build from scratch

docker build . -t hello-welt
docker run -p 3000:3000 hello-welt

Local Development

To use this image locally, clone this repo, install dependencies and run the app:

git clone https://github.com/julie-ng/hello-welt
npm install
npm start

Then open http://localhost:3000 in your browser.

Logging

For local development, we will use pino-pretty to format logs with color

npm install -g pino-pretty

We also also use nodemon to automatically restart the app when code changes. Use the dev command to put everything together

npm run dev

References

• Heroku Blog: Let It Crash: Best Practices for Handling Node.js Errors on Shutdown by Julián Duque
• Snyk Blog: 10 best practices to containerize Node.js web applications with Docker by Liran Tal and Yoni Goldberg

License

MIT