There could be a large amount of data to delete so I decided to handle the deletes behind the scenes with jobs. This worked well and during all my testing, there was never an issue. If an issue does occur a notification gets sent and I can fix the issue.
However, after release, I tested with a throwaway account, and it wasn’t working. As a user I could reset my state but when I signed in again all my data was still showing.
For a little while I was perplexed. The API wasn’t erroring, the data was being removed but Budget still showed the old state. The first hint happened when I tried to do something in Budget; I immediately got an error from the API, a budget item couldn’t be created because the resource didn’t exist.
Aha! I knew what the problem was. I said to myself, “Budget has data, the API doesn’t, there must be a cache issue somewhere.”
Budget doesn’t retain a cache so it can only be the API. I rush (really, I did) to my IDE and low and behold, my jobs don’t clear the cache after deleting the requested data – oops!
How did this happen?
Well, that’s easy. During development, I turn off the cache on my local instance of the API as I don’t want the cache getting in the way of any new features I’m writing or debugging. I test before I make a new release, manually and automatically. Though clearly, I’m not always turning cache back on.
The solution is easy – do a better job of testing but it isn’t quite as simple as that. I’m going to update my automatic tests to include testing with and without caching enabled. More importantly though, I’m going to expose the API cache status.
It isn’t unusual for the development or staging version of your Apps to highlight their status – a bar at the top, a different background, a visual notifier of some kind. I’m going to update Budget and all the other Costs to Expect Apps to include this notifier and show the state of the API, is caching enabled? Is it in debug mode? That way when I’m testing a data state feature, I’m more likely to spot that status and think about the extra steps.