I'm working on an iOS Safari extension that has a ServiceWorker. Lately we've noticed that this ServiceWorker seems to get killed seemingly at random, and there are no logs or crash reports to tell us what happened.
I'm hypothesizing that iOS might be shutting down Safari ServiceWorkers when the ProcessInfo.thermalState approaches .serious. I have circumstantial evidence that our ServiceWorker tends to get killed more often at higher levels of thermalState but can't yet say conclusively that this is the case. I can't find any direct evidence of this on internet searches either.
Is anyone able to shed light onto this topic? The specific symptoms are:
- ServiceWorker stops, and the menu entry for its console window no longer appears on macOS Safari.
- No crash logs via Xcode or Sentry, and no Console messages as far as we could tell (caveat: MobileSafari generates a LOT of messages! We might have missed it.)
- If attached via debugger, the native part of our extension just disappears and the debugger loses connection with no error message.
- ServiceWorker no longer works for the lifetime of the Safari process. Sometimes, when we kill Safari and restart, we can get the ServiceWorker back. This usually requires toggling our extension's "enabled" state in system settings.
- In some cases, even killing/relaunching Safari and toggling the system setting doesn't bring our ServiceWorker back. I'm hypothesizing right now that this happens when the thermal state is high.
I've tried simulating a serious/critical thermal state in the Xcode Devices window, but couldn't repro the ServiceWorker problem. I don't know if that setting affects the whole system, though, or just our own apps.
Help appreciated!
Yuna