A simple project to demonstrate how with a Flask app and an Apache Traffic Server reverse proxy you can leverage ETags in order to keep your cache fresh and your server cool.

There are two components:

• backend is a very simple Flash application which demonstrates the ETag functionality. You can run it by its own to check how the browser behaves or you can run it behind the cache
• cache is the ATS reverse proxy which will serve as a cache in front of your backend.

In order to run the whole thing, you can use Docker Compose:

docker-compose up --build

Then visit http://localhost:9000 with your browser. You should be able to see a page giving you both an ETag and a random string. Between refreshes, both values should be constant:

• The ETag won't change until you click the button
• The random string should stay in cache as long as you don't change the ETag

You should be able to visit this URL from different browser and see the same result out of the cache every single time.

When you click on the "Change ETag" button from any browser, refreshing from any browser should again show you consistent results across all requests, with the cache being refreshed for all clients.