Healthchecks and Restart Policies

Part of the Docker course

Your stack is up. docker ps says everything is running, and the site returns errors. You dig in and find the API started before the database was ready, failed its first connection, and has been serving 500s ever since to a process that is technically alive and therefore technically fine.

That is the gap this lesson closes. "The process is running" is a much weaker statement than "the app works," and Docker cannot tell the difference unless you teach it how to ask. Once it can ask, you also get to say what should happen when the answer is no. ...