• Envoy Mobile will need to be aware of certain application lifecycle events (such as backgrounding/foregrounding, termination, etc.) in order to appropriately shut down connections, restart, or tell the OS that the app has requests in flight while it’s backgrounded.
• These should be handled entirely by the native Envoy Mobile layers, and will likely perform the following tasks:
• Upon instantiation/startup, begin observing application-level lifecycle events
  React to changes by restarting Envoy core - shutting down connections, etc. as necessary
• Ensure that the Envoy core is able to make requests when the app is backgrounded

Google doc reference here.
iOS issue: #128