Background Processing and Scheduling

In the previous lesson, we explored how mobile applications are managed throughout their life cycle. In this lesson, we will focus on how tasks can continue to run reliably and efficiently, even when the app is no longer in the foreground.

Mobile applications are expected to be responsive and efficient, even when they aren’t actively being used. From syncing emails to performing routine maintenance tasks, background processing plays a crucial role in enabling applications to perform essential functions without requiring user intervention. However, designing this functionality is not as straightforward as scheduling tasks. It involves a fine balance between functionality and conserving limited resources such as battery life, CPU time, and network bandwidth.

In mobile System Design, background task execution must comply with the operating system’s life cycle management policies. Today’s mobile platforms offer sophisticated tools and APIs that facilitate this (as discussed in the previous lesson), but they also impose strict limitations to prevent abuse and preserve device performance. Developers must skillfully design background workflows within these boundaries.

Let’s start by exploring how platforms such as Android and iOS facilitate task execution in the background.

Platform facilities for background execution

To support background tasks, both iOS and Android provide dedicated frameworks. However, their mechanisms differ in how they schedule and execute these tasks.

iOS: Background App Refresh and Task Scheduler

iOS is designed with a user-first philosophy, which includes tight control over background activities to preserve battery life and performance. Developers must work within these constraints using system-approved mechanisms to ensure their apps remain efficient, yet responsive. Two primary options for handling background work (tasks) in iOS are Background App Refresh and the BGTaskScheduler framework. Let’s discuss them one by one:

Background App Refresh

Background App Refresh allows apps to periodically wake in the background to fetch small amounts of data and update content. This feature is ideal for apps like news readers, weather apps, or social media platforms that need to present fresh information when the user opens them.

When enabled, the system uses machine learning to determine the optimal time to refresh content based on usage patterns, device state (such as whether it’s on Wi-Fi or charging), and available resources. Apps don’t control the exact timing, but they can register to perform lightweight operations.

Key characteristics of the Background App Refresh are as mentioned below.

• Unpredictable schedule: The system, not the developer, chooses when to wake the app.

• Limited execution time: Apps typically receive only a few seconds to complete their task.

• There are no guarantees: Tasks might not run if the system is under heavy load or the user disables the feature.

The following is a pseudocode for ...