µService™ for managing AWS auto-scaling groups and their lifecycle events.
By default, ASGs will forcefully shut your instance down when scaling in. In order to prevent that, the lifecycle must be actively handled by responding to events via lifecycle hooks.
This is mostly for running instances of worker on AWS.
On scale-in we do not want to cancel currently running jobs. Instead, we want to stop accepting new work, finish the existing jobs, and then shut down.
On scale-out we want to do some initial set-up (downloading docker images) before taking on work.
For scaling in, cyclist will receive a termination request via SNS. It will notify the instance that is to be retired to shut down gracefully (all workers poll for this condition). The instance finishes the jobs and notifies cyclist that it is ready to shut down. Cyclist then terminates the instance.
Ensure that you have cloned the repository into your $GOPATH, e.g.
~/go/src/github.com/travis-ci/cyclist.
makemake dev-server