Sharing sample -> User joins session but never joins room

[Holo-Krzysztof]

I've noticed a strange bug which seems like a race condition: sometimes, when looking at the debug output of the Sharing sample you get a "User joining session" debug print but after that it seems to be stuck forever in the AnchorStore_Initialized state because the sharing service never gets marked as ready. This happens because SharingSessionTracker.SendJoinEvent() is called before ImportExportAnchorManager gets to subscribe to this event.

The problem went away after moving SharingSessionTracker.Instance.SessionJoined += Instance_SessionJoined; from SharingManagerConnected() to Start() , so I'd propose that as a solution. Can anyone else reproduce this issue and give me some more insight?

[NeerajW]

I can believe this. Were you in Debug mode? This was a relatively recent change by @alexdrenea inside SharingStage. Seems reasonable to move SharingSessionTracker.Instance.SessionJoined += Instance_SessionJoined; to Start().

@alexdrenea any thoughts on this?

[alexdrenea]

I checked the code as well and I agree that the event should be hooked up in Start, there's no good reason for it to be in the SharingManagerConnected() method.

I can't validate it on a real device at the moment though (due to lack of availability 😞).

[NeerajW]

@Holo-Krzysztof would you like to make the change?

[Holo-Krzysztof]

I'm not entirely sure yet, because after that change I've got a NullReferenceException in InitRoomApi() once, but that could be due to other changes in the project. I'll investigate that and if there are no issues, I'll make a pull request.

On Di. Okt. 18 19:54:43 2016 GMT+0200, Neeraj Wadhwa wrote:

@Holo-Krzysztof would you like to make the change?

You are receiving this because you were mentioned. Reply to this email directly or view it on GitHub: https://github.com/Microsoft/HoloToolkit-Unity/issues/292#issuecomment-25458708

[Holo-Krzysztof]

Btw, it was in release mode, @NeerajW.

[Holo-Krzysztof]

Alright, I discovered another bug related to my change: Sometimes SharingManagerConnected never gets called and thus roomManager is null, leading to exceptions in InitRoomApi().

Let's look at a sample execution:

• SharingStage calls Awake(), which in turn calls Connect() (in my case, because auto discovery is off)
• Connect() does some config steps and creates a SharingManager from native and then says "Wait a second and check if we're connected" with the Invoke() call below (which seems like asking for trouble, not to mention that it's hard to find in the editor -> no references in Shift+F12 because it's not a direct call, but uses reflection)
• In the meantime, Awake() methods of other scripts are running too, and after that each script's Start() method is called, such as that of ImportExportAnchorManager, which sets up the event handler SharingManagerConnected.
• If the above step didn't complete within approx. 1 second (or the time Unity decides to invoke SendConnectedNotification()), the event handler in ImportExportAnchorManager is never called, which leaves us with NullReferenceExceptions all over the place instead of a valid RoomManager.

I'm currently thinking of a good way to solve this and will edit this comment accordingly. Any thoughts on this, @NeerajW @alexdrenea?

EDIT: I think I've solved it, but don't have time right now to submit my changes. You'll get a pull request next week.

[StephenHodgson]

Yeah I'm no fan of Invoke().

Especially this one:

private void Instance_SessionJoined(object sender, SharingSessionTracker.SessionJoinedEventArgs e)
{
    // We don't need to get this event anymore.
    SharingSessionTracker.Instance.SessionJoined -= Instance_SessionJoined;
     // We still wait to wait a few seconds for everything to settle.
    Invoke("MarkSharingServiceReady", 5);
}

Another issue is that testing in the Editor is difficult because ImportExportAnchorManager only puts you in a room if WorldAnchorStore.GetAsync(AnchorStoreReady); completes successfully (Which it never does because we're not actually on device).