Silent pushes not delivered to the app on iOS 11

So the release notes of iOS 11.1 beta 1 say

iOS 11.1 beta 1 was just released and they mention: "Notifications Resolved Issues • Silent push notifications are processed more frequently. (33278611)

I did some tests and it seems to be indeed fixed:

Suspended State

When I launch the app in a suspended mode and send a silent push, the app is brought back to background and the didReceiveRemoteNotification:fetchCompletionHandler delegate is called.

Foreground State

In the same way, when the application is in foreground and a silent push is sent, the delegate seems to be called as expected. This was randomly not working in previous iOS 11 versions so I will confirm this after more testing.

Just wanted to add my 2 cents in here as I've been hit by this issue too and I've noticed that Apple has closed several radars on this issue saying they couldn't reproduce. An interesting thing I found is that the pushes will get delivered if the app is backgrounded while it's attached to the debugger.

If I kill the debugger, unplug my phone, launch the app, and send the silent push payload I see the app NOT getting woken. I do see the in the Console log that the system cancels delivery of the payload to my app.

I've submitted a radar with a small sample app that reproduces the problem. I've also explicitly noted in the radar that the person working on my ticket must not be running the app attached to the debugger to reproduce the issue. Here's the link: https://bugreport.apple.com/web/?problemID=34461063

Hopefully this will cause some progress to be made on this issue.

Looks like a new behaviour of iOS 11. iOS 11 beta 10 provides some descriptive logs regarding this issue:

default 23:18:51.806011 +0200   dasd    com.apple.pushLaunch.com.acme.Acme:F7E7D0:[
    {name: ApplicationPolicy, policyWeight: 50.000, response: {Decision: Can Proceed, Score: 0.50}}
    {name: BatteryLevelPolicy, policyWeight: 1.000, response: {Decision: Can Proceed, Score: 0.87, Rationale: [{batteryLevel == 62}]}}
    {name: DeviceActivityPolicy, policyWeight: 5.000, response: {Decision: Can Proceed, Score: 0.20}}
 ] sumScores:52.279483, denominator:81.410000, FinalDecision: Can Proceed FinalScore: 0.642175}
default 23:18:51.806386 +0200   dasd    'com.apple.pushLaunch.com.acme.Acme:F7E7D0' has compatibility score of 1.000000 with 'com.apple.CFNetwork-cc-111-79:E7272D'. Relaxing scores.
default 23:18:51.806855 +0200   dasd    'com.apple.pushLaunch.com.acme.Acme:F7E7D0' CurrentScore: 0.642175, ThresholdScore: 0.738454 DecisionToRun:0

Looks like every silent push is delivered to the iOS, but dasd daemon uses couple of policies to decide if silent push should be delivered to the app (e.g. battery level). I managed to receive one silent push yesterday night, but my iPhone was connected to charger at that time – probably BatteryLevelPolicy score was high enough to receive that one silent push.

Apple gives no official information about this iOS-side behaviour, there is only information about server-side throttling:

Silent notifications are not meant as a way to keep your app awake in the background, nor are they meant for high priority updates. APNs treats silent notifications as low priority and may throttle their delivery altogether if the total number becomes excessive. The actual limits are dynamic and can change based on conditions, but try not to send more than a few notifications per hour.

I keep my fingers crossed they changed that behaviour, because that would fix my app :) On the other hand, this change is good – one among many things making iPhone battery lasting longer that Android phones.

iOS 11.1 beta release notes include: Notifications Resolved Issues Silent push notifications are processed more frequently. (33278611)