Docker for Rails Developers

Tasks and Swarm’s Scaling Model

Services running on Swarm are self-regulating. That is, we define a desired state for a service in terms of the number of containers that should run for it, and Swarm acts to ensure that this state is achieved and maintained.

It is this self-regulation that is key to how scaling is implemented, as well as Swarm’s self-healing properties, which we’ll see in the next chapter.

Swarm is made up of different parts. We can consider one part to be the orchestrator. Having told Swarm to deploy a service, the orchestrator is responsible for determining whether the service is in the desired state and, if not, taking action to correct this.

If the orchestrator sees that an additional container is needed, it creates a task ...