The purpose of the health check is to allow docker itself to talk to whatever service is running on the container to make sure it’s always responding happily, connected to everything it needs to be connected to for proper operation, and is not overloaded or stuck somehow.

Docker does this by pretending to be a web browser, and going to the specified “health check URL”. The key thing I think you’re missing here is that the health check URL is supposed to be a URL that, ideally, runs on your container and does some meaningful checks on the health of your service, or at the very least, proves that when you connect to it, it is able to serve up a working static page or login page or something (which doesn’t actually prove it’s working completely, but is often good enough)

Now, you’re probably wondering why this isn’t automatic, and the answer is because there’s no standard “health check URL” that fits all services. Not all services even respond to URLs at all, and the ones that do may have different URLs for their health checks, they may need different hostnames to be used, etc.

By setting health check URL to example.com, basically what you’re doing is constantly testing whether the real-world website https://example.com/ way over there somewhere is working, and as long as it is, docker assumes your container is fine. Which it might be, or it might not be, it has no idea and you have no idea, because it’s not even attempting to connect to the container at all, it’s going to the URL you specified, which is way out there on the internet somewhere, and this effectively does nothing useful for you.

It’s understandable why you probably thought this made sense, that it was testing network connectivity or something, but that is not the purpose of the health check URL, and if you don’t have a meaningful URL to check, you can probably just omit or disable the healthcheck in this case. Docker only uses it to decide if it needs to restart the container or alert you of the failure.