CODEWITHSUNDEEP
dockernginx
harryg
harryg

Reputation: 24077

Have nginx set header on response according to environment var

I use a simple Nginx docker container to serve some static files. I deploy this container to different environments (e.g. staging, production etc) using Kubernetes which sets an environment variable on the container (let's say FOO_COUNT).

What's the easiest way of getting Nginx to pass the value of FOO_COUNT as a header on every response without having to build a different container for each environment?

Upvotes: 2

Views: 6338

Answers (2)

Chen A.
Chen A.

Reputation: 11280

This was made possible in nginx 1.19+. This functionality is now builtin.

All you need to do is add your default.conf.template file (it looks for *.template suffix) to /etc/nginx/templates and the startup script will run envsubst on it, and output to /etc/nginx/conf.d.

Read more at the docs, see an example here https://devopsian.net/notes/docker-nginx-template-env-vars/

Upvotes: 1

lifeisfoo
lifeisfoo

Reputation: 16294

Out-of-the-box, nginx doesn't support environment variables inside most configuration blocks. But, you can use envsubst as explained in the official nginx Docker image.

Just create a configuration template that's available inside your nginx container named, e.g. /etc/nginx/conf.d/mysite.template.

It contains your nginx configuration, e.g.:

location / {
    add_header X-Foo-Header "${FOO_COUNT}";
}

Then override the Dockerfile command with

/bin/bash -c "envsubst < /etc/nginx/conf.d/mysite.template > /etc/nginx/conf.d/default.conf && nginx -g 'daemon off;'"

If you're using a docker-compose.yml file, use command.

Kubernetes provides a similar way to override the default command in the image.

Upvotes: 2

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