Crash when using coarse relocalization happen randomly on iOS

[tomkrikorian]

Description

In our App, we use coarse relocalization running all the time with a watcher. We stop the watcher when we have to :

• Save a new anchor
• Delete an anchor Since the watcher does not work while we do these two operations while it's running (in our test, it crashes). We start the watcher again when we finish saving the anchor and/or deleting anchors. We noticed a persistent crash that happens randomly when we use coarse relocalization, we think it might be tied to us restarting the watcher like this :

1. We stop the watcher :

   _watcher.Stop();

2. We save an anchor or delete an anchor.
3. We start the watcher again like this (not resetting the session before launching the watcher makes the app crash too) :

   await _spatialAnchorManager.ResetSessionAsync(); _watcher = _spatialAnchorManager.Session.CreateWatcher(_anchorLocateCriteria);

4. After a while, the app might crash randomly.

Steps to reproduce the issue

Don't have a steps to repro since it's not part of the sample. Here is the part of the crash log that might help :

Thread 1 name: Thread 1 Crashed: 0 libsystem_kernel.dylib 0x00000001b7e2b964 __pthread_kill + 8 1 libsystem_pthread.dylib 0x00000001f19e4378 pthread_kill + 268 (pthread.c:1610) 2 libsystem_c.dylib 0x000000018bd02f50 abort + 164 (abort.c:118) 3 libsystem_c.dylib 0x000000018bd5996c __assert_rtn + 300 (assert.c:96) 4 AzureSpatialAnchors 0x00000001049cd0e8 0x104198000 + 8605928 5 AzureSpatialAnchors 0x0000000104687b64 0x104198000 + 5176164 6 AzureSpatialAnchors 0x00000001042e9508 0x104198000 + 1381640 7 AzureSpatialAnchors 0x00000001042e99b0 0x104198000 + 1382832 8 AzureSpatialAnchors 0x000000010432f4d4 0x104198000 + 1668308 9 AzureSpatialAnchors 0x00000001041d2760 0x104198000 + 239456 10 libdispatch.dylib 0x0000000180b3b660 _dispatch_client_callout + 20 (object.m:560) 11 libdispatch.dylib 0x0000000180b4cef0 _dispatch_root_queue_drain + 684 (inline_internal.h:2601) 12 libdispatch.dylib 0x0000000180b4d5f8 _dispatch_worker_thread2 + 164 (queue.c:6930) 13 libsystem_pthread.dylib 0x00000001f19de0b8 _pthread_wqthread + 228 (pthread.c:2554) 14 libsystem_pthread.dylib 0x00000001f19dde94 start_wqthread + 8

Expected behavior

Running coarse relocalization without a crash.

Development information (please complete the following information)

• OS: macOS
• Development Platform\Version: Unity 2021.1.27f1 & Xcode 13.1
• Azure Spatial Anchors SDK version: 2.11.0

AR Device information (please complete the following information):

• Device: iPhone (all versions supporting AR)
• OS: iOS 15.1, iOS 15.0, iOS 15.2

[phamqduc]

Hi @tomkrikorian, Thank you for letting us know the issues that you experienced around coarse relocalization feature. In order of us to better understand and reproduce the issues, could you please try to applying the above mentioned steps similarly onto the Unity/iOS sample (Coarse Reloc demo) to see if it's working and hence, having another point of reference for debugging your app? For example,

• to have the watcher running from beginning, you can set currentWatcher = CreateWatcher() right after the function call ConfigureSensors() in AdvanceDemoAsync function, case AppState.DemoStepConfigureSensors:.
• to stop the watcher before saving, add to AdvanceDemoAsync/case AppState.DemoStepSaveCloudAnchor:

  if (currentWatcher != null)
  {
  currentWatcher.Stop();
  currentWatcher = null;
  }

  before await SaveCurrentObjectAnchorToCloudAsync();

• to avoid anchorLocated events (due to active watcher) to cause skipping app stage while saving anchor is in progress, in OnCloudAnchorLocated function, guard app state change

  if (currentAppState == AppState.DemoStepLookingForAnchorsNearDevice)
  {
     currentAppState = AppState.DemoStepStopWatcher;
  }

  Please let us know if you can reproduce a crash when changing the sample app that way.

Moreover, could you please elaborate your observations/findings w.r.t the following:

• Does the app only crash during query mode with coarse relocalization?
• If you happen to work on Unity/Android as well, do you see a similar crash? (we try to understand if the issue is cross platforms)
• If you work on iOS app (non-Unity version), do you see a similar crash? Thank you for helping us to better understand the issues.

[tomkrikorian]

Little update, someone on my team is going to try your suggestions. We'll get back to you with what we got from our tests.

[Morgane-Minsar]

Hi @phamqduc I am tomkrikorian’s colleague, I am taking the case. I tried your suggestions in your sample by creating a fork from your repository to a new one. You can see the new repository here. I duplicated the scene AzureSpatialAnchorsCoarseRelocDemo to AdvancedAzureSpatialAnchorsCoarseRelocDemo as well as the script AzureSpatialAnchorsCoarseRelocDemoScript for AzureSpatialAnchorsCoarseRelocDemoScriptAdvanced I use in my new scene.

I tried then to build and test on my iPhone 12 pro. See all steps I did:

1. open the scene AdvancedAzureSpatialAnchorsCoarseRelocDemo
2. create, configure and start Azure Spatial Anchor session
3. create location provider and configure sensors
4. start watcher -> it finds anchors
5. spawn an object
6. stop watcher
7. save anchor, stop Azure Spatial Anchor session
8. create and start Azure Spatial Anchor session
9. start watcher -> it finds anchors
10. stop watcher, stop Azure Spatial Anchor session
11. reset demo -> it deletes anchors
12. create, configure and start Azure Spatial Anchor session
13. create location provider and configure sensors
14. start watcher -> it doesn’t find anchors
15. spawn an object
16. stop watcher
17. save anchor, stop Azure Spatial Anchor session
18. create and start Azure Spatial Anchor session
19. start watcher -> it finally finds anchors

I create a videoshot for you to understand better all steps and the issue. The video is too big for GitHub, let me know if you want it and how I can send it to you. I don’t have any crash, except once but I didn’t know what I was doing. However, you can see that the step 14 is an issue. I have to add an anchor to be able to discover other anchor as I have done steps 15 to 19.

To answer your questions

Does the app only crash during query mode with coarse relocalization?

We only use coarse relocalization, so I don’t know.

If you happen to work on Unity/Android as well, do you see a similar crash? (we try to understand if the issue is cross platforms)

We only work on Unity/iOS and so, our code would not work good enough on Unity/Android to test if there are similar crashes on this platform too.

If you work on iOS app (non-Unity version), do you see a similar crash?

We don’t have enough time to work on iOS app without Unity to test theses crashes. We are focusing the platform iOS with Unity as a development tool.

We really appreciate your reactivity on our issue. Let me know if I can do something else.

[msftradford]

Hi @Morgane-Minsar, thanks so much for the detailed description and source code! It sounds like you are no longer hitting the original reported crash, is that correct? As far as making sure that your watcher returns anchors in step 14, I think that all you need to do is add a call to await CloudManager.ResetSessionAsync(); after you've stopped the previous session in step 10. In your script, that change should look like this:

case AppState.DemoStepStopSessionForQuery:
    CloudManager.StopSession();
    await CloudManager.ResetSessionAsync();
    currentWatcher = null;
    locationProvider = null;
    currentAppState = AppState.DemoStepComplete;
    break;

Let us know if that works. Thanks!

[Morgane-Minsar]

Hi @msftradford, I can confirm that I don't have the original reported crash and also, the reset session solves the issue step 14. Thank you !