Arvados

Current thinking is:

• You write an Ansible inventory for your existing cluster.
  • In principle we could automate this, but it would be very challenging given the very different ways the Salt and Ansible installers are configured and model the cluster, and the variety of supported configurations. Right now it doesn't feel worth it to write code for this specific part so it stays a manual process.
• You run a one-time playbook that converts an existing Salt-managed cluster. It:
  • Downloads the Arvados config.yml for use by the Ansible installer
  • Moves/removes configuration on cluster servers (nginx sites, crontab entries, etc.) that the Ansible installer will handle differently.
    • We might be able to reduce the need for some of this by changing paths, etc. in the Ansible installer so it automatically takes over stuff currently managed by Salt. That's also acceptable.
• You run install-arvados-cluster.yml.
  • This sets up your existing cluster the way our Ansible playbook expects. Once this succeeds, the conversion is done.