Added local and disk caching and test targets.

[ddaddy]

Ok, so there's a lot going on here.

I've added your local caching but fixed a few bugs. I also made it generic and not specific to SignalPostBody as was suggested on Twitter. The cache will load any previously unsent signals from disk on initialisation. I've refactored the SignalPayload into it's own struct. There's a new SignalManager that handles the cache, timer etc.. SignalManager will send a new batch of signals every 10 seconds and also once at startup (If any previous signals exist) Signals are sent in batches of 25. Attempting with 50 sometimes resulted in a Payload Too Large error. There's no mitigation if sending 25 gives this error, so maybe increase the payload size server side just to make sure. If signals fail to send, they will be added back to the queue, so if a Payload Too Large error does occur, they will always be stuck in the cache.

The cache is saved to disk at different points depending on device/os:

• iOS will keep everything in memory until the app is completely killed by the system of killed from the App Switcher by the user.
• macOS will keep everything in memory until the app is quit.
• watchOS & tvOS will dump the cache to disk when the app is backgrounded and restore it when foregrounded.

There is a new showDebugLogs option on the TelemetryManagerConfiguration that will show very detailed logs of everything in action.

There are 4 new targets added to the project that I have thoroughly tested:

• iOS: To test the disk caching, you need to swipe the app up from the app switcher. On next run it will load the cache file. Stopping the app running via Xcode results in there being no disk cache file and a clean start next time.
• macOS: To test the disk caching, quit the app from either the menu bar, Cmd + Q or right clicking on the icon. Stopping the app running via Xcode results in there being no disk cache file and a clean start next time.
• watchOS: Disk caching can be tested by simply pressing the home button
• tvOS: Press Esc to background the app and save cache to disk. Use ←→ + Enter to select the app and bring it back to foreground to load the disk cache.

You will notice that in the Xcode project there is a separate framework target for watchOS. This is necessary because building for watchOS builds both the iOS and watchOS targets and results in errors trying to add the iOS framework into a watchOS target. This is purely for the sample targets and shouldn't affect how the SPM package is delivered and built. (Someone else may be able to fix it to use the 1 framework 🤷‍♂️)

I have not updated the README

[winsmith]

Hi Darren.

this looks really good! I'm reading through the code and nodding my head.

One question though: You're copying the ClientTester application into the repository, and I assume that is to directly test the client without having to do the package dance, but I can't get it to work? I was expecting an xcproj file or something, but there's just a Package.swift and it doesn't seem to define a target.

Is this an oversight on your part, or am I just not getting how to use it?

[ddaddy]

There should definitely be an xcode proj file. Maybe it didn't check in. Just out watching the football (Come on England 😬). I'll check it later or in the morning.

[ddaddy]

🥳 The .gitignore that the project had, ignored the Xcode project file. It should be added now.

[winsmith]

Okay, so it looks really good! I just updated the server to accept up to 1MB post requests on that endpoint, so I think we can accept larger numbers of signals at once. I'm going to play around with it a little more :)

[ddaddy]

Great. 100 should be easily achievable and within 10 seconds should be fine. It'll only really hit the limit when the app is used without an internet connection and all signals cached.

[winsmith]

This all works really well in my tests! Thank you very much! I'm going to merge it and layer some docs on top!