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Spring Cloud Stream - demystified and simplified

This is the first post in a series of blog posts meant to clarify and preview what’s coming in the upcoming releases of spring-cloud-stream and spring-cloud-function (both 3.0.0).

Recently, I had a discussion with a user and heard something that prompted me to begin a series of blog posts (starting with this one) with the goal of both demystifying the true goals of Spring Cloud Stream and Spring Cloud Function projects as well as demonstrating their new features.

Spring Integration Wrapper?

The specific phrase that prompted all this was - "Spring Cloud Stream, being a light Spring Integration input/output router…”. That’s an interesting perception, but I have to disagree. While it may have been inspired by Enterprise Integration Patterns (EIP) and builds on top of Spring Integration (SI), that last part is really just an implementation detail. Spring Cloud Stream (SCSt) as a framework was never about “being a light Spring Integration input/output router”. In fact, this statement shows part of the problem, where SI (the framework of choice to support some of the internal requirements of SCSt) was somehow perceived to be the core of SCSt in such way that many perceive SCSt to be an extension or a wrapper to SI. It is not. It has always been about pure microservices and binding them to sources and targets of data (i.e., messaging systems) . Simple as that.
If you abstract yourself far enough from knowing the internals of SCSt, you quickly realize that it is really a binding and activation framework. It binds a piece of code (provided by the user) to source/target of data exposed by the binder and activates such code according to binder implementation (for example, message arrival and so on). That is pretty much it.

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Spring Initializr 0.8.0 available now

On behalf of the team and everyone who has contributed, I’m happy to announce that Spring Initializr 0.8.0 has been released and is now available from repo.spring.io. For the first time, the release is also available from Maven Central!

This release includes 90 fixes, improvements and dependency upgrades. Thanks to all those who have contributed with issue reports and pull requests.

Spring Initializr 0.8 brings a complete rewrite of the project generation API with dedicated abstractions for common assets of JVM-based projects:

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This Week in Spring (SpringOne Platform 2019 edition) - October 8th, 2019

It’s here it’s finally here! My favorite time of the year! Happy SpringOne Platform week! This week I’m in amazing Austin, TX talking to anybody who wants to about all things Spring. There have been a ton of amazing things announced at this show but one thing I’ve been excited to share with y’all is that we just announced the new Azure Spring Cloud runtime. (More on that in the links below)

I’ve been busy! I’m doing one talk with Microsoft on Azure Spring Cloud, and another with Okta / Google on simplifying the dev lifecycle. Also, I’m hosting the keynote tomorrow morning. So much to do, so little time!

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What's new in Spring Data Moore?

Spring Data Moore ships with 16 modules and over 700 tickets completed. It includes tons of improvements and new features across the portfolio and has a strong focus on three major topics: Reactive, Kotlin, and Performance. The release adds features such as declarative reactive transactions and Coroutines/Flow support and comes with up to 60%* faster finder methods.

Let’s start with a look at some of the Reactive features of Moore.

Declarative, reactive transactions

The Lovelace Release introduced early support for reactive transactions in a closure-fashioned style that left some room for improvements. The following listing shows that style:

Reactive Transactions in Lovelace (with MongoDB)
public Mono<Process> doSomething(Long id) {

  return template.inTransaction().execute(txTemplate -> {

    return txTemplate.findById(id)
      .flatMap(it -> start(txTemplate, it))
      .flatMap(it -> verify(it))
      .flatMap(it -> finish(txTemplate, it));

  }).next();
}

In the preceding snippet, the transaction has to be initiated by explicitly calling inTransaction() with a transaction-aware template within the closure, calling next() at the end to turn the returned Flux into a Mono to satisfy the method signature, even though findById(…) already emits only a single element.

Obviously, this is not the most intuitive way of doing reactive transactions. So let’s have a look at the same flow using declarative reactive transaction support. As with Spring’s transaction support, you need a component to handle the transaction for you. For reactive transactions, a ReactiveTransactionManager is currently provided by the MongoDB and R2DBC modules. The following listing shows such a component:

@EnableTransactionManagement
class Config extends AbstractReactiveMongoConfiguration {

  // …

  @Bean
  ReactiveTransactionManager mgr(ReactiveMongoDatabaseFactory f) {
    return new ReactiveMongoTransactionManager(f);
  }
}

From there, you can annotate methods with @Transactional and rely on the infrastructure to start, commit, and roll back transactional flows to handle the lifecycle via the Reactor Context. This lets you turn the code from Lovelace into the following listing, removing the need for the closure with its scoped template and the superfluous Flux to Mono transformation:

Declarative Reactive Transactions in Moore (with MongoDB)
@Transactional
public Mono<Process> doSomething(Long id) {

  return template.findById(id)
    .flatMap(it -> start(template, it))
    .flatMap(it -> verify(it))
    .flatMap(it -> finish(template, it));
}
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Spring Cloud Hoxton.M3 is now available

On behalf of the community, I am pleased to announce that Milestone 3 (M3) of the Spring Cloud Hoxton Release Train is available today. The release can be found in the Spring Milestone repository. You can check out the Hoxton release notes for more information.

Notable Changes in the Hoxton Release Train

This milestone release is compatible with Spring Boot 2.2.0.RC1.

Spring Cloud Circuit Breaker

We welcome Spring Cloud Circuit Breaker as a new project under the Spring Cloud release train. This project provides an abstraction API for adding circuit breakers to your application. At the time of this blog post, there are four supported implementations:

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Spring Boot for Apache Geode & Pivotal GemFire 1.1.2.RELEASE and 1.2.0.RC1 Available

On behalf of the Spring, Apache Geode, Pivotal GemFire and Pivotal Cloud Cache communities, I am pleased to announce the release of Spring Boot for Apache Geode, Pivotal GemFire and Pivotal Cloud Cache (PCC) 1.1.2.RELEASE as well as 1.2.0.RC1.

SBDG 1.1.2.RELEASE builds on Spring Boot 2.1.9.RELEASE and is available in Maven Central.

SBDG 1.2.0.RC1 builds on Spring Boot 2.2.0.RC1 and is available in the Spring Milestone Repository.

Additionally, SBDG 1.2.0.RC1 bits can be included in a project generated with the Spring Initializer at https://start.spring.io. Simply type "Geode" in the "Search dependencies to add" input field and you will see the "Spring for Apache Geode" dependency appear as an option you can add. This includes the spring-geode-starter dependency in your project Maven or Gradle build files when you generate a project using the Initializer. Check it out!

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Reactor Dysprosium (3.3.x) goes GA

Hello Reactor community,

On behalf of the Reactor team and its heroic new contributors, I am delighted to announce that Reactor Dysprosium can now be found on your preferred Maven repositories, like this one.

It is the fourth release train since Reactor Core 3.x and it includes Reactor Core 3.3, Reactor Netty 0.9 and a newcomer, Reactor Pool 0.1. Check out the major change logs and release notes:
- reactor-core 3.3.0.RELEASE
- reactor-netty 0.9.0.RELEASE
- reactor-pool 0.1.0.RELEASE

Reactor Dysprosium modules still require JDK 8 or higher. They come with many performance improvements and we even have identified more areas to focus on the next patches and major releases. Please join me in giving a warm welcome to a new module to the family, Reactor Pool. It is the generic embeddable reactive object pool you were waiting for. It is used by Reactor Netty and we plan to build more features on top of it. As with Reactor Netty, we haven’t qualified a major “1.x” release as we expect tweaks before considering it API stable.

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Reactor Californium-SR12 is out

The 12th Service Release for Californium is out. As per tradition, it fixes several issues and bring improvements all around.

The release is available on your preferred maven central repository.

Change logs and release notes:
- reactor-core 3.2.12.RELEASE
- reactor-netty 0.8.12.RELEASE

Bismuth EOL

With Dysprosium-RELEASE, our reactor-core 3.1.x and reactor-netty 0.7.x lines will not receive further patches. We encourage our users to update to Californium releases trains, which match Spring Boot 2.1.x and Spring Framework 5.1.x.

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