Hi guys,
I'm developing a custom VPN client with NEPacketTunnelProvider which tunnels all device traffic. All is going well so far but I've noticed that iOS battery statistics (Settings -> Battery) is claiming that our client has consumed a significant amount of energy (10%~30%). I though it was true for a while, but then I conducted some basic testing which suggested this is more likely a statistical issue.
I set up my device (rebooted with clean battery cosumption statistics) with ~80% battery capacity and started to watch "NASA Live" channel in Youtube app with 1080p60 quality, for 3 hours, and taking notes every hour. I cross referenced the data of the same scenario (same device as well) collected with our custom VPN provider enabled and disabled. I made sure when the VPN client is enabled, I can actually see the Youtube traffic tunneled. Actually the video feed can generate ~1GiB traffic per hour pretty stably. I can provide detailed numbers if necessary, but generally, after 3 hours, both scenarios showed an overal of ~50% battery consumption (from the battery indicator on the status bar on top of the phone screen), there was no significant difference in the battery consumption. However when I looked at the statistics in Settings -> Battery, the scenario without our VPN client was showing 100% battery consumption from Youtube app (which is expected), and the scenario with VPN was showing 68% for Youtube, and 32% for our VPN client app!
32% battery consumption in statistics is scaring. But what confuses me is that the actual device battery consumption didn't increase. My theory is that without the VPN client, individual apps are sending out their traffic on their own so the battery consumption are calculated on their head. But now with our VPN client, we are actually sending out traffic for every applications so iOS will blame us for that part of energy consumption. I'm not sure if the theory is true but it certainly explains the behavior.
I'm wondering if Apple can look at the issue at if proved to be a statistical issue then fix it. Because 10%+ battery consumption on our app would be enough to scare away our customers. We can explain to them there is no actual extra energy consumption but customers will be suspicious. Whenever they feel their phone's having a shortened battery life they'll come to see the list and they will blame us.
Thanks in advance!
