Resetting the db for a deployed Rails application

Unfortunately:

A simple rails db:reset will not work to reset the db for a deployed application.
Servers are not consistent, so no single process will work in all cases.

However, the following should handle most cases:

Stop all services connecting to the db. This can be accomplished by executing the following as ksu on each of the application's servers:

systemctl stop apache2
systemctl stop passenger
systemctl stop sneakers
systemctl stop sidekiq-*

Note: An application may only have some of these services. There is no harm in executing the command if a service is absent.

Drop the database: RAILS_ENV=production bundle exec rails db:drop (If you really mean it, precede this command with: DISABLE_DATABASE_ENVIRONMENT_CHECK=1)

Note:

Rails may complain that there remaining db connections. If so, look for any processes that may be connecting to the db with ps -fu <APP USER> and stop the processes.
The user might not have permissions to drop the database. In that case, connect with psql as the postgres user (psql -U postgres) and drop the database: DROP DATABASE <DB NAME>;
If a peer authentication error occurs when connecting with psql as the postgres user then:

su postgres
psql

Create the database by running puppet on the db server as ksu: puppet agent --test --environment=production. This will create the database with the appropriate settings (as specified in puppet).

Note:

The db server may be local (i.e., the same as the server running the Rails application) or a separate, dedicated server.
If local, execute the following before running puppet: source /etc/profile.d/rvm.sh && rvm use system

Migrate: RAILS_ENV=production bundle exec rails db:migrate
Seed if required by the application: RAILS_ENV=production bundle exec rails db:seed