kaiyou/jinja repository overview

⁠Jinja configuration templates for Docker

Warning: this script is still an early version and should only be used for production with great care and much testing. For instance, exceptions are not handled yet and the container will crash in many cases.

Security warning: this script is mostly intended for devops under the asumption that templates are managed with the same security policy as the script itself. The utils module that is passed to the Jinja renderer makes executing arbitrary code from the template a piece of cake.

⁠Introduction

This project is based on the awesome tiller principle and the amazing docker-gen by jwilder. It ships as a Docker containers that listens on the Docker socket for specific events then walk through a directory and renders each configuration file through the Jinja templating engine.

This behavior can easily be leveraged to dynamically reconfigure other Docker containers or hosts to adapt to changing contexts. For instance :

• run a dynamic DNS server replying to Docker container names ;
• run a dynamic Web reverse proxy (just like jwilder/nginx-proxy does) ;
• run a dynamic [whatever] reverse-proxy ;
• dynamically monitor all containers, build Web pages, or pour coffee based on the list and configuration of running containers.

⁠DNS Resolver for containers

Simply put the following hosts file template inside your source directory:

127.0.0.1	localhost

{% for container in containers %}
{{ container["NetworkSettings"]["IPAddress"] }}	{{ container["Name"][1:] }}
{% endfor %}

Run the configuration parser:

$ docker run -d --name=config-parser -t \
-v /path/to/src:/src \
-v /path/to/dst:/dst \
kaiyou/docker-jinja -n dnsmasq

Then run the appropriate dnsmasq container:

$ docker run --name=dnsmasq \
-v /path/to/dst/hosts:/hosts \
-p 53:53/udp \
yourfavourite/dnsmasq --no-resolv --no-hosts --addn-hosts=/hosts

You may now query your containers:

$ dig A dnsmasq @127.0.0.1
;; QUESTION SECTION:
;dnsmasq.			IN	A

;; ANSWER SECTION:
dnsmasq.		0	IN	A	10.0.0.2

⁠Dynamic reverse proxy

The following configuration mimics the dynamic behavior of jwilder/nginx-proxy.

{% for container in containers %}
{% set env = utils.get_env(container) %}
{% set hosts = env.get("VIRTUAL_HOST", "").split(",") %}

{% if hosts[0] %}

upstream {{ container["Id"] }} {
	server {{ container["NetworkSettings"]["IPAddress"] }}:{{ port }}:80;
}

{% for host in hosts %}

server {
	server_name {{ host }};
	listen [::]:80;

  location / {
		proxy_pass http://{{ container["Id"] }};
	}
}
{% endfor %}
{% endif %}
{% endfor %}