Make the App Robust to Race Conditions

[amalnanavati]

With the app and robot being different devices, our feeding system is fundamentally a distributed system that communicates over the network. As a result of that, we have to consider what race conditions might arise and what our system should do in those circumstances.

For example, say the web app calls a ROS action, it completes, but because of a broken pipe or temporary networking issue the web app doesn't receive the response. In the current system, the user would be stuck on that state forever, which is undesirable. On the other hand, we could add app functionality so that if the response is not received within n seconds, a button appears that lets the user move on to the next state. Or a button appears that lets the user re-try the same action. Or maybe that is not necessary, because the user might just refresh the page.

With that example in mind, the goal of this issue is to:

1. Identify areas in the web app where race conditions might exist and result in undesirable outcomes for the user.
2. Understand what options the user would like out of the system in those scenarios.
3. Implement those features, so the user is never left stuck or without recourse in the case of a race condition.