...

1. Set apache::service_ensure: false, heat::api::enabled: false, heat::engine::enabled: false and heat::api_cfn::enabled: false in hiera to stop all services
2. Add the following to the node-specific hiera file for heat-api nodes:
   1. apache::mod::wsgi::package_name: 'libapache2-mod-wsgi-py3'
   2. apache::mod::wsgi::mod_path: '/usr/lib/apache2/modules/mod_wsgi.so'
3. Do one of:
   1. Run puppet with zed modules/tags, Run apt-get update && apt-get dist-upgrade && apt-get autoremove
   2. Reinstall the nodes with zed modules/tags
4. Run heat-manage db_sync on one of the api-nodes.

5. Remove the hiera keys that disabled the services and re-run puppet

Barbican

Barbican must be stopped for upgrades, and can thus be performed on all barbican hosts at the same time. It might be an idea to keep one set of hosts stopped at old code in case of the need for a sudden roll-back.

1. Stop all barbican-services by adding the following keys to node-specific hiera, and then make sure to run puppet on the barbican hosts:

   1. barbican::worker::enabled: false

   2. apache::service_ensure: 'stopped'

2. Run puppet with the zed modules/tags

3. Run apt dist-upgrade && apt-get autoremove

4. Run barbican-db-manage upgrade

5. Re-start barbican services by removing the keys added in step 1 and re-run puppet.