Introducing OOM reporting: a new dimension to app quality

by Sean Curran, Software Engineer

Stability issues can derail the success of even the best apps – glitchy software repels people. We know that app quality is one of your top priorities and crashes are your worst nightmare, which is why Crashlytics will always alert you when issues arise. We’ll even help you pinpoint their root cause so you can fix issues fast – we’ve got your back!

Today, we’re extending our crash coverage to include out-of-memory (OOM) reporting on iOS. Now, you can see stability from a whole new angle by understanding the impact OOM events have on your app experience.

What’s an OOM event and when does it occur?

Unexpected app terminations degrade your app experience and interrupt your user’s session. One type of app termination you’re probably familiar with is crashes, but there’s another unexpected termination that warrants your attention called an OOM event.

An OOM event is an app termination that occurs when a mobile device runs out of memory. All apps need memory to work, but there is only a finite amount available on each device. When an app needs more memory and there isn’t any available, the operating system terminates the app session. To your users, this looks like any other crash, however in reality, this is an OOM event.

Our approach to solving a hard problem: intelligent heuristics

OOM events are difficult to report because iOS doesn’t provide any direct mechanism to detect them and they can be caused by factors beyond your app environment and control, such as your app’s memory usage. But because of how important it is to understand your rate of OOM events, we took on this challenge and added OOM reporting to Crashlytics for iOS devices.

Here’s how it works: When you enable the Crashlytics and Answers Kits available on Fabric, we get a stream of live data about your app’s performance. Then, we apply a server-side process of elimination to this data stream to detect OOM events in your app. This detection is based on an intelligent heuristic, inspired by the work of two talented engineers. In other words, we analyze your app’s event stream to come up with an explanation of why it terminated and if we can’t match it up it to a known reason for termination, we count it as an OOM event. And, since no changes to the Answers SDK were required, you will automatically get OOM reporting without needing to do any work (as long as you have both Crashlytics and Answers installed).

This is an example of how your app analytics and stability kits can work together to unlock powerful new insight – something neither kit could do alone.

At Pinterest, we're shipping iOS app updates every two weeks to millions of people. Using the new OOM insights, we've been able to track our memory optimizations and have confidence in the stability of each release.

- Scott Goodson, Head of Core Experience


New line of sight into the impact of OOM events on app quality

Our new OOM reporting dashboard will help you understand if OOM events are a problem for your app. Now, you’ll be able to see the overall percentage of app sessions that were unaffected by OOM events across your builds. You can even drill down and see the percentage of OOM-free sessions for individual builds. This will help you answer important questions like, “Is my app being terminated more on one build than another?” and “Is my app seeing more or less OOM-free sessions over the last week?”

We’ll also give you a sortable, daily device breakdown so you can compare the raw OOM counts and the percent of OOM-free sessions across different iOS devices. Once you know which iOS device experiences the most OOM events, you can better triage and spend your time investigating problems on your most used devices. After you roll out a fix, you can monitor the number of OOM events on that device to see if your solution helped reduce them. You may even learn that there are some low-end devices that you simply can’t support.

This additional information paints a clearer picture of your app stability across devices and provides clues for troubleshooting.

Finally, we’ll show you the total number (i.e., the raw counts) of OOM events across all of your builds versus your top three builds. Use this graph to understand the prevalence and magnitude of OOM events.

Don’t let OOM events crash your app party 🎉

Our mission is to ensure that there are no more sad, unstable apps. By adding OOM reporting into Crashlytics, we’re giving you even more insight into the quality of your app. Don’t be blindsided by OOM issues that disrupt your users’ app experiences (and maybe even cause them to flee!). Monitor your OOM-free sessions, promptly identify when OOM events become a problem, and get valuable direction on where to start your troubleshooting by going to the OOMs page from your Crashlytics dashboard. Check it out and let us know what you think!

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