Adding backpressure design pattern #3233

[sanurah]

Pull Request Template

What does this PR do?

This PR is adding the backpressure design pattern
Relates to #3233

[github-actions]

PR Summary

This PR implements the backpressure design pattern in Java using Reactor. It includes a Publisher that generates a stream of integers, and a Subscriber that processes them with a simulated delay, demonstrating backpressure handling to prevent consumer overload. The implementation uses Reactor's BaseSubscriber to control the request rate and prevent overwhelming the subscriber. The PR also includes comprehensive unit tests and documentation.

Changes

File	Summary
backpressure/README.md	This file provides a comprehensive explanation of the Backpressure design pattern, including real-world examples, a detailed explanation, a programmatic example in Java using Reactor, and when to use or avoid this pattern. It also includes diagrams and references.
backpressure/etc/backpressure.png	New file: Diagram showing the Backpressure pattern architecture.
backpressure/pom.xml	This file configures the Maven project dependencies, including Reactor and testing libraries. It also sets up the main class for execution.
backpressure/src/main/java/com/iluwatar/backpressure/App.java	This Java class serves as the main application entry point. It demonstrates the backpressure pattern by creating a publisher and subscriber, and then subscribing the subscriber to the publisher's stream.
backpressure/src/main/java/com/iluwatar/backpressure/Publisher.java	This Java class implements the Publisher, which generates a stream of integers with a configurable delay. It uses Reactor's Flux to create the stream.
backpressure/src/main/java/com/iluwatar/backpressure/Subscriber.java	This Java class implements the Subscriber, which processes the integer stream from the Publisher. It uses Reactor's BaseSubscriber to implement backpressure, requesting items in batches and simulating processing time.
backpressure/src/test/java/com/iluwatar/backpressure/AppTest.java	This Java class contains a unit test to verify that the main application runs without throwing any exceptions.
backpressure/src/test/java/com/iluwatar/backpressure/LoggerExtension.java	This Java class is a JUnit extension that captures log messages for testing purposes. It uses Logback to capture log events and provides methods to access them.
backpressure/src/test/java/com/iluwatar/backpressure/PublisherTest.java	This Java class contains unit tests for the Publisher class, verifying that it generates the expected stream of integers with the correct delays.
backpressure/src/test/java/com/iluwatar/backpressure/SubscriberTest.java	This Java class contains unit tests for the Subscriber class, verifying that it correctly processes the stream and applies backpressure.
pom.xml	Added a module for the backpressure example to the main pom.xml file.

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[github-actions]

✅ LGTM!

Review Summary

Commits Considered (3)

• 7c3ba8a: Merge branch 'iluwatar:master' into master
• 1fa515f: Adding backpressure pattern #3233
• b8f51f0: Initial commit backpressure

temp

Files Processed (11)

• backpressure/README.md (1 hunk)
• backpressure/etc/backpressure.png (0 hunks)
• backpressure/pom.xml (1 hunk)
• backpressure/src/main/java/com/iluwatar/backpressure/App.java (1 hunk)
• backpressure/src/main/java/com/iluwatar/backpressure/Publisher.java (1 hunk)
• backpressure/src/main/java/com/iluwatar/backpressure/Subscriber.java (1 hunk)
• backpressure/src/test/java/com/iluwatar/backpressure/AppTest.java (1 hunk)
• backpressure/src/test/java/com/iluwatar/backpressure/LoggerExtension.java (1 hunk)
• backpressure/src/test/java/com/iluwatar/backpressure/PublisherTest.java (1 hunk)
• backpressure/src/test/java/com/iluwatar/backpressure/SubscriberTest.java (1 hunk)
• pom.xml (1 hunk)

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[github-actions]

✅ LGTM!

Review Summary

Commits Considered (1)

• b85de31: Fix test case #3233

Files Processed (10)

• backpressure/README.md (1 hunk)
• backpressure/pom.xml (1 hunk)
• backpressure/src/main/java/com/iluwatar/backpressure/App.java (1 hunk)
• backpressure/src/main/java/com/iluwatar/backpressure/Publisher.java (1 hunk)
• backpressure/src/main/java/com/iluwatar/backpressure/Subscriber.java (1 hunk)
• backpressure/src/test/java/com/iluwatar/backpressure/AppTest.java (1 hunk)
• backpressure/src/test/java/com/iluwatar/backpressure/LoggerExtension.java (1 hunk)
• backpressure/src/test/java/com/iluwatar/backpressure/PublisherTest.java (1 hunk)
• backpressure/src/test/java/com/iluwatar/backpressure/SubscriberTest.java (1 hunk)
• pom.xml (1 hunk)

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Skipped Comments (0)

[github-actions]

✅ LGTM!

Review Summary

Commits Considered (1)

• 4552f83: Fix formatting #3233

Files Processed (5)

• backpressure/src/main/java/com/iluwatar/backpressure/App.java (1 hunk)
• backpressure/src/main/java/com/iluwatar/backpressure/Publisher.java (1 hunk)
• backpressure/src/main/java/com/iluwatar/backpressure/Subscriber.java (1 hunk)
• backpressure/src/test/java/com/iluwatar/backpressure/PublisherTest.java (1 hunk)
• backpressure/src/test/java/com/iluwatar/backpressure/SubscriberTest.java (1 hunk)

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Skipped Comments (1)

• backpressure/src/main/java/com/iluwatar/backpressure/Subscriber.java [36-42]

  performance: "Inefficient delay simulation in processItem method."

[iluwatar]

Check out the Sonar issue

[iluwatar]

No need to declare logger like this. With the Lombok annotation you automatically have LOGGER available.

[github-actions]

✅ LGTM!

Review Summary

Commits Considered (1)

• 58af7b3: Changes after review #3233

Files Processed (8)

• backpressure/pom.xml (1 hunk)
• backpressure/src/main/java/com/iluwatar/backpressure/App.java (1 hunk)
• backpressure/src/main/java/com/iluwatar/backpressure/Publisher.java (1 hunk)
• backpressure/src/main/java/com/iluwatar/backpressure/Subscriber.java (1 hunk)
• backpressure/src/test/java/com/iluwatar/backpressure/AppTest.java (1 hunk)
• backpressure/src/test/java/com/iluwatar/backpressure/LoggerExtension.java (1 hunk)
• backpressure/src/test/java/com/iluwatar/backpressure/PublisherTest.java (1 hunk)
• backpressure/src/test/java/com/iluwatar/backpressure/SubscriberTest.java (1 hunk)

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[github-actions]

✅ LGTM!

Review Summary

Commits Considered (1)

• 36131dd: Fix sonar error in leaderfollowers module #3233

Files Processed (1)

• leader-followers/src/main/java/com/iluwatar/leaderfollowers/App.java (1 hunk)

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Skipped Comments (1)

• leader-followers/src/main/java/com/iluwatar/leaderfollowers/App.java [70-76]

  best practice: "Resource Management Improvement"

[github-actions]

✅ LGTM!

Review Summary

Commits Considered (1)

• 817cfbc: Merge branch 'master' into master

Files Processed (0)

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[sonarqubecloud]

Quality Gate passed

Issues
8 New issues
0 Accepted issues

Measures
0 Security Hotspots
81.1% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[iluwatar]

Looks good! Thank you for the contribution 🎉

@all-contributors please add @sanurah for code

[allcontributors]

@iluwatar

@sanurah already contributed before to code