Скачать или смотреть How to Efficiently Use repeatWhenEmpty in Spring Webflux

Learn how to effectively utilize `repeatWhenEmpty` instead of `retryWhen` in Spring Webflux to optimize your reactive programming, ensuring your endpoint calls are correctly repeated.
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This video is based on the question https://stackoverflow.com/q/62641880/ asked by the user 'Matley' ( https://stackoverflow.com/u/6022333/ ) and on the answer https://stackoverflow.com/a/62642680/ provided by the user 'Phil Clay' ( https://stackoverflow.com/u/11248746/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Efficiently Use repeatWhenEmpty in Spring Webflux: A Comprehensive Guide

In the world of reactive programming, particularly when utilizing Spring Webflux, developers often face complex challenges when it comes to handling data fetching and validating responses. One frequent scenario is needing to repeatedly call an endpoint until specific data criteria are met. This guide dives into how to effectively use repeatWhenEmpty to achieve this without unnecessarily restarting entire chains of reactive calls.

The Problem: Repeating Calls to the Endpoint

Imagine that you are building a Spring Boot application that requires interaction with a remote service. You need to call the findById method of commandControllerApi, with the intention of receiving a response with a status of SUCCESS. However, as you develop, you notice that there’s a flaw in your current implementation that leads to the entire reactive chain restarting instead of just the specific part where the call is made; this is not ideal.

Key Questions:

How can you repeat only the findById call when an endpoint returns an empty or unsuccessful result?

How can you avoid accidentally re-executing the upstream chain of calls, such as fetching the user or saving a command?

The Solution: The Power of repeatWhenEmpty

To streamline the process of checking responses from findById, we can leverage repeatWhenEmpty. Here’s a step-by-step guide on how to implement this change effectively.

Refactoring the Current Code

The original code snippet implements a retryWhen strategy that may inadvertently re-trigger the entire upstream calls. Here’s how you can refactor it to solely resubscribe to the findById call:

[[See Video to Reveal this Text or Code Snippet]]

Explanation of Code Changes

Positioning repeatWhenEmpty:

Placing repeatWhenEmpty directly after the findById call ensures only this specific call is retried.

This prevents the entire upstream chain from being re-executed when an empty or unsuccessful result is returned.

Use of filter:

The filter checks the status and confirms that we only proceed with valid responses.

Exponential Backoff:

The defined exponential backoff strategy with Duration.ofSeconds(5) adds a delay between attempts, gracefully managing the repeated calls.

Conclusion: Enhancing Your Reactive Programming with Webflux

Utilizing repeatWhenEmpty over retryWhen allows your Spring Webflux application to be more efficient and responsive. By restructuring your code to isolate retries to specific calls, you enhance performance while minimizing overhead. By following this guide, you will be better equipped to handle situations where data availability is uncertain and ensure the calls to your APIs are done efficiently.

Key Takeaways:

Isolate the retryable logic to prevent unnecessary re-executions of upstream services.

Control retries with strategies such as exponential backoff to manage network load gracefully.

Ensure that status checks are in place to continue validating the right conditions.

Implementing these strategies will greatly improve your application’s responsiveness and reliability.