A brief look at the new Kamal Proxy replacing Traefik
Kamal 2 is coming with a brand new custom proxy that’s replacing Traefik. Let’s have a look at why is that and what it means.
Kamal is a simple deployment tool built around Docker containers. While Docker itself has a Swarm mode allowing for more robust deploys, Kamal keeps things simple by running the containers with straightforward docker run calls. But starting and stopping containers this way comes without their automatic replacement. Kamal needs a way to handle zero-downtime deployment for web containers so it originally incorporated Traefik.
While there are many HTTP proxies around, Kamal was in the market for something of the auto-discovery of Docker containers. Something could make the proxy configuration management minimal. Traefik is such a proxy – it was specifically built as a dynamic reverse proxy for orchestrating container traffic. This meant that Kamal would only need to label the web containers for Traefik to select them. Docker health checks then did the rest by pointing to the healthy containers that should receive new traffic.
There was one problem with Traefik. Kamal had to create a special cord file on the host and bind mount it into the container to be able to control the health check that was responsible for driving traffic alongside the label. By introducing the cord file check Kamal could make any container unhealthy by deleting their associated cord file. And while it mostly worked, it was seen as a hack.
