Building Serverless Applications with Google Cloud Run

Chapter 7. Task Scheduling

Most applications need to schedule tasks to be executed later, either immediately after handling an HTTP request or after a delay. In this chapter, I’ll show you how to handle task scheduling on Cloud Run—because the usual approaches won’t work like you expect.

On a traditional server, you handle these types of tasks by spawning a background thread or scheduling a cron job, but these approaches are not compatible with serverless environments like Cloud Run: the platform only guarantees CPU access while your container is handling requests, and the containers are disposable. This means your container might disappear, or lose CPU access while handling a task.

I will start with a list of example use cases and introduce you to a way to execute tasks reliably with Cloud Tasks, another Google Cloud product. These include:

• Processing an image—a user uploads a picture and you want to resize and crop the file

• Generating a PDF—for example, an invoice

• Making a screenshot of a web page using a headless browser

• Regenerating a search index after a database record updates

Cloud Tasks

Cloud Tasks is a product that helps you reliably schedule and execute HTTP requests. Take a look at Figure 7-1 to see how you would use it to handle background tasks.

You start with scheduling a task. You might think that Cloud Tasks performs that task, but it’s not going to. Scheduling a task means you hand the recipe for an HTTP request to Cloud Tasks, and executing a task means Cloud ...