Suddenly getting many Fabric Out of Memory sessions: Can Fabric OOM Reports ever be false alarms?

Question

I recently added background fetch in my application and it is working well. I recently noticed in Fabric that the amount of OOM free sessions have gradually gone from 100% to a daily average steady in the teens as low as 14%. I only saw a few crashes reported here and there and there is no other evidence of crashes reported by users.

After reading how OOM sessions are detected, it seems like it may be false reports. Users launch the app and later it goes to background state. Then later, the app is launched for background fetch, performs fetches, and is terminated - this happens as often as the OS allows.

Is it possible that the Fabric's OOM detector is falsely detecting OOMs due to the way repeated background fetch launches and terminations happen?

Active

Answer 1

Yes, there are certain instances when OOMs are falsely detected due to the current OOMs heuristics. Background fetching can falsely report OOMs.

Lickspittle

We are seeing the same symptom as @Barrett, but due to background location updates (geofencing). Could we workaround by detecting UIApplicationLaunchOptionsLocationKey in didFinishLaunchingWithOptions and avoiding Fabric initialization in this case? – Erickson

Thanks. You could, but this may cause some issues with reporting in other cases. Feel free to test it out and let me know how it goes :) – Pastis

Hi, could you try and succeed with above method? – Galactometer

What should a target OOM Free Session % look like? I mean, this sounds like it's not entirely within the hands of developers. If a user opens up several other apps, eventually the not recently opened one will close. That being said, I've got a very low % of OOM free sessions, likely also due to background location refreshing it seems. – Jett

Also seeing OOM reports, but is apparently due to background fetch. So frustrating -- spent the last two hours monitoring memory usage because of this false positive. – Yoo

I faced same issue. OOM dropped from 97% to 65%. I am using background fetch. Did you guys figure anything new about it? Any way to be sure its background fetch? We are usign a lot of 3rd parties so not sure which one is causing this. – Mouse

Answer 2

This most probably because of background fetch and one way to test it is to push a build on test flight with BG fetch disabled and test it for couple of days for some users. If your numbers don't drop for that particular build you can be sure it is because of false reporting by fabric and move on. If you still face the issue than you will have to get out your instruments and check.

Unmannered