Cache state in localStorage

[baransu]

When we're for some reason reloading page, we lose all state and in the worst case we have to wait 5s for the new state from the server. My idea is to cache state in localStorage and when we're reloading page it will be loaded from cache. If observed node crashes and we're reloading page to reconnect we don't want to display old, cached state so we have to wipe it on WebSocket connection crash.
It's a small change but can be nice quality of life improvement.

[arkgil]

I like the idea of improving our UX 👍 The crucial part here is to make sure old data is cleaned up.

[michalslaski]

If I don't have any browser tabs open, then I restart ./erlangpl script and then again open the browser, the local cache is not cleaned up. The only way to clean it up is to have a tab opened, so that it can discover the WebSocket connection crash. This may be confusing.

[baransu]

We're storing start timestamp in ets and then sending it to client on new connection so client should clean when connection crashes or ./erlangpl was restarted.

[baransu]

I've disabled caching for now: 476688b so it' no longer blocking release.

This issue is still relevant and definitely needs better solution. Unfortunately I don't have time to focus more on Erlang Perf Lab right now, but I hope I'll find more time in the future to work on parts that needs improvement to make it better software :)