Services and service definitions

- [Instructor] Let's move on from tasks a bit,…and talk about keeping things running over time,…and talk about how we do deployments well,…with Docker on AWS.…So Services.…Services have a Configuration,…that includes Which task the service should run,…What version of that task is currently running,…Where it's running, and sort of how should be distributed…across that cluster.…Now, they also maintain the current state of the system.…Is it running at all?…How many should be running?…How many are just getting started,…that's called the pending count.…

And also how many are currently running and stable?…If currently there are less running then there should be,…it will start some up.…They'll go into pending,…and eventually they'll reach running,…and hopefully if your system is healthy,…after a short while, current running…will be equal to the desired count.…It also helps manage deployments…to give your service a smooth transition between versions.…This is one of the areas where Immutable tasks,…the idea of creating new versions of tasks…