Don't automatically enable processes
When a Rails app is deployed for the first time with a Procfile (and I think also when a processing server is added), 1 process is automatically booted for each entry in the Procfile.
This is bad for at least two reasons:
Testing - processing may begin before you can verify deployment was configured correctly (e.g all correct environment variables have been set, connecting to correct DB, etc)
Resource exhaustion - deployments with many Procfile entries could lead to lots of unnecessary connections being made to databases, and preventing other applications from accessing these resources.
We have about 3 dozen Sidekiq queues with 20 Procfile entries targeting specific queues (in case we need to temporarily divert processing). Deploying a new stack will immediately spawn 500 database connections (20 process X 25 Sidekiq workers) exhausting our allocation.
It would make more sense to allows us to scale up the processes as we need them.