Docker2Caddy

This tool automatically generates configuration files for reverse proxy functionality between Caddy and Docker containers. It provides something like auto-discoverability, so if a new Docker container is spun up, it will be scanned sooner or later for specific labels. If they match the tool's expectations, Caddy configuration for this host will be generated.

Container configuration

To allow caddy to be a reverse proxy for a docker container, and docker2caddy find the necessary information, you'll have to add labels to the docker container. In a docker-compose.yml file, this could look like the following:

webservice:
  container_name: webservice
  image: httpd:2.4
  restart: always
  ports:
    - "12345:8080"
  labels:
    proxy.host: "example.com"
    proxy.port: "12345"
    proxy.host_alias: "example.org,www.example.com"

In this example, the exposed port in the Docker container is 8080, and we map it to port 12345 on the host.

The labels can be configured in config.cfg.

Install

docker2caddy

To deploy docker2caddy on a host, these files should be handled.

• One of the caddy config templates in caddy_host_templates_/ or an own one -> /etc/docker2caddy/caddy_host.j2 (basic.j2 is the simplest)
• config.cfg -> /etc/docker2caddy/ (rename from .sample)
• docker2caddy.py -> /usr/local/bin/docker2caddy
• logrotate.d/docker2caddy -> /etc/logrotate.d/ (must be root:root, 0644)
• systemd/docker2caddy.service -> /etc/systemd/system/

caddy

Within caddy, you need to import the new directory in which the configs are created:

import /etc/caddy/docker2caddy/*

Troubleshooting

Docker rootless

If you have a rootless Docker setup, you should set the DOCKER_HOST config variable, e.g. to unix:///run/user/1001/docker.sock. Please note that a system-wide environment (not only from .bashrc) or one that is directly called with the program (e.g. DOCKER_HOST=foobar docker2caddy.py or a prior export) always takes precedence.

Logs and Debug

Logging will take place in /var/log/docker2caddy.log. Logs are rotated daily, and kept back for the last 7 days.

Also check systemd's journal: journalctl -u docker2caddy