Engineering Reliable Mobile Applications

Modern mobile apps are complex systems. They mix multitiered server architecture run in data centers, messaging stacks, and networks with sophisticated on-device functionality both foreground and background. However elaborate, users perceive the reliability of the service through the devices in their hands. Did the application do what was expected quickly and flawlessly? At Google, the shift to a mobile focus brought SRE to emphasize the true end-to-end user experience and the specific reliability problems presented on mobile. We’ve seen a number of production incidents in which server-side instrumentation taken by itself would have shown no trouble, but where a view inclusive of the user experience reflected end-user problems. For example:

• Your serving stack is successfully returning what it thinks are perfectly valid responses, but users of your app see blank screens.

• Users opening your maps app in a new city for the first time would see a crash, before the servers received any requests at all.

• After your application receives an update, although nothing has visibly changed, users experience significantly worse battery life from their devices than before.

These are all issues that cannot be detected by just monitoring our servers and datacenters. For many products, the user experience (UX) does not start or reach the server at all; it starts at the mobile application that the user employs to address their particular use case, such ...