Also, for taking apps to production, there should definitely be a part on high availability.
Also, for taking apps to production, there should definitely be a part on high availability.
It is a review of the most fundamental tools and strategies in Red Hat flavored Linux distros. Things like troubleshooting the entire stack would be far too advanced and specific.
Ad 12-factor. Some makers are better off not to follow everything. For example, it's fine to use server disk space for a single server. So I don't want to include it as dogma.
Ad CI/CD. You either build it yourself (and the book gives you the technical knowledge to do it) or use a vendor (GitHub/GitLab/Circle CI). I actually want to do a bit more on CI/CD, but thinking how to approach it.
There is a reason it's called "from Scratch", because I cover starting out. Some things bootstrapping startups don't need (there are only nice-to-haves). I will update and improve the text based on feedback, though (including the comment above).
As for high availability I discuss whether it's worth it or not in the Scaling chapter. I also show how to use NGINX as a load balancer. I currently don't have HA content written for PG and Redis, but there are planned (as a free update).