Systemd vs. Docker

Posted Feb 25, 2016 11:25 UTC (Thu) by Cyberax (✭ supporter ✭, #52523)
In reply to: Systemd vs. Docker by federico3
Parent article: Systemd vs. Docker

> Please tell us this was a joke.
Why? That's a correct way to design a service.

If you're building fault-tolerant systems then you should be prepared to survive failures of individual nodes - hardware is not perfect, even if your software is. And if you have a failover mechanism in place, then why not just use it?

Obviously, you need to keep persistent state somewhere, but that can often be moved to a few dedicated and specialized nodes/containers. It's possible to use Docker with stateful services, just not as easy as with stateless ones.

Systemd vs. Docker

Posted Feb 25, 2016 11:33 UTC (Thu) by smurf (subscriber, #17840) [Link] (2 responses)

Having to restart a service, just because it cannot cope with running indefinitely, is in NO way "correct".

Running a process not designed for running as PID-1 in that role does not work. Yet, Docker does that. Therefore Docker has a (serious IMHO) design bug.

This is not a question of keeping persistent state.

Systemd vs. Docker

Posted Feb 25, 2016 11:54 UTC (Thu) by Cyberax (✭ supporter ✭, #52523) [Link] (1 responses)

This is a minor issue in practice. There are ways to install a minimal process manager as PID1 that simply reaps children. Launching systemd or anything of similar complexity is not a good idea inside a container.

What would help, is systemd acquiring a notion of externally-managed services. It'll help to declare dependencies between systemd units and Docker instances.

Systemd vs. Docker

Posted Feb 25, 2016 17:45 UTC (Thu) by rahvin (guest, #16953) [Link]

What would help, is systemd acquiring a notion of externally-managed services.

According to the article systemd is already capable of that through it's messaging and socket activation protocols. I see no reason you couldn't run systemd inside the container, in fact I believe that's the significant difference in opinion between Docker and Redhat that's driving this article.

Though docker has the marketshare at this point there are alternatives developing that appear to take security and other things a lot more seriously than the docker folks. Time will tell but I believe ultimately Docker is going to lose this war.