Rancher性能（Docker中的Docker？）

Question

Looking at Rancher, what is the performance like? I guess my main question, is everything deployed in Rancher docker in docker? After reading http://jpetazzo.github.io/2015/09/03/do-not-use-docker-in-docker-for-ci/ I trying to stay away from that idea. It looks like the Rancher CI pipeline with Docker/Jenkins is docker in docker, but what about the rest? If i setup a docker-compose or deploy something from their catalog, is it all docker in docker? I've read through their documentation and this simple question has still just flown over my head. Any guidance would be much appreciated.

Thank you

Answer 1

Rancher itself is not deployed with Docker in Docker (DinD). The main components of Rancher, rancher/server and rancher/agent are both normal containers. The server, in a normal deployment, runs the orchestration piece and a few other key services for the catalog, Docker Machine provisioning, websocket-proxy and MySQL. All of these can be broken out if desired, but for simplicity of getting started, its all in one. We use s6 to manage the orchestration and database processes.

The rancher/agent container is privileged and requires the user to bind mount the hosts Docker socket. We package a Docker binary in the container and use it to communicate with the host on startup. It is similar to the way a Mac talks to Boot2docker, the binary is just a client talking to a remote Docker daemon. Once the agent is bootstrapped, it communicates back to the Rancher server container over a websocket connection. When containers and stacks are deployed Rancher server sends events to the agents which then call the hosts Docker daemon for deployment. The deployed containers are running as normal Docker containers on the host, just as if the user typed docker run ... . In fact, a neat feature of Rancher is that if you do type docker run ... on the host, the resulting container will show up in the Rancher UI.

The Jenkins entry in the Rancher catalog, when using the Swarm plugin is doing a host bind mount of the Docker socket as well. We have some early experiments that used DinD to test out some concepts with Jenkins, but those were not released.