How to Process a List String with Synchronous Delays After flatMap in Reactive Programming

Discover how to process a List String in a synchronous manner after using flatMap in reactive programming. Learn practical solutions and insights into managing delays effectively.
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Understanding Synchronous Processing in Reactive Programming

Reactive programming can often feel overwhelming, especially when trying to control the flow of operations in a way that feels synchronous. A common challenge is processing a List<String> in a synchronous manner after applying transformations and filters with flatMap in libraries like Project Reactor. Let's explore the problem in detail while providing a clear, step-by-step solution.

The Problem

You may find yourself in a situation where you want to:

Fetch a list of domains from an external service.

Filter out the domains that already exist in your database.

Store any new domain data back into your database.

The key is to ensure that these HTTP requests are made in a synchronous manner, with intentional delays between them.

The Proposed Solution

To achieve your goal without losing the reactive benefits of your code, follow these steps:

Step 1: Fetch the Domain List

Start by fetching the list of domains using the external service. This will return a Flux<DomainListResponse>.

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Step 2: Filter Existing Domains

Next, apply a filter to exclude domains that already exist in your database.

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Step 3: Implement Synchronous Domain Verification

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Step 4: Introduce Delays

To achieve the desired delay between the processing of each domain, use delayElements() appropriately. You can create a delay using a random duration to simulate the time it takes for each HTTP request.

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

Step 5: Store Domain Data

Finally, once you've verified the domains, you’ll need to store the new domain data into your database. This can be done within the last flatMap operator.

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Example Code Implementation

Here’s a simple demonstration of how this could be set up in a minimal example:

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Expected Output

You should see output indicating that the synchronous processing is working as required:

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

Conclusion

By following the steps outlined above, you can handle the need for synchronous processing in reactive programming effectively. You’ve learned how to set up a sequence of filtering and delays to fetch domain information properly without overwhelming your system. Embrace these techniques, and your journey in reactive programming will be all the smoother!