Dear Apache Pulsar community members, I have developed a Reactive Streams adapter for the Apache Pulsar Java Client. It uses Project Reactor as the Reactive Streams implementation.
The repository is here: https://github.com/lhotari/reactive-pulsar and library is available in Maven Central: https://search.maven.org/search?q=g:com.github.lhotari%20a:reactive-pulsar* I would like to contribute this library to the Apache Pulsar project. I would suggest that the library is committed to a separate repository, for example https://github.com/apache/pulsar-reactive . # Motivation There's a need to "go reactive from end-to-end" when building modern reactive applications with platforms such as Spring Reactive. There are ways to adapt the Apache Pulsar Java client async API calls to Reactive Streams with a few lines of code. However, a lot will be missing and achieving the complete solution will require much more effort. The primary goal of this library is to provide a Reactive Streams adapter that wraps the Apache Pulsar Java client with Reactive APIs for sending, reading and consuming messages. The secondary goal is to provide a Spring Boot starter for easily adopting the power of Apache Pulsar for Spring Boot applications. It is currently out of scope for this library to build a reactive client all the way from the binary protocol handling. This library builds upon the existing Apache Pulsar Java client and uses the async API for operations. # Features - Simple and intuitive reactive APIs for sending, reading and consuming messages. - Non-blocking backpressure support for the provided reactive APIs - Pulsar client resource lifecycle management that integrates with the Reactive programming model - Additional producer caching that caches producers. - Useful for API backends since the Pulsar client producer resource can be shared and cached across multiple REST calls. - Support for in-order parallel (concurrent) processing at the application level - I/O intensive message processing can leverage Project Reactor's capabilities to efficiently handle thousands of simultaneous I/O calls to external REST APIs and resources that have Reactive clients/drivers. - In-order parallel processing support can retain key-order at the level of a single consumer. I'm presenting the library and it's features tomorrow on September 2nd in the SpringOne virtual conference, which is free to attend. The session details and schedule are at https://springone.io/2021/sessions/reactive-applications-with-apache-pulsar-and-spring-boot . # Licenses The Reactive Pulsar Adapter library is under the Apache Licence Version 2.0 . The main dependencies are reactor-core (https://github.com/reactor/reactor-core) and jctools-core ( https://github.com/JCTools/JCTools) which are also ASL 2.0 licensed. There's also a dependency to Caffeine (https://github.com/ben-manes/caffeine) and the Spring Boot Starter depends on Spring Boot and Spring Framework. These are all ASL 2.0 licensed libraries. The additional Spring integration testing support library depends on Testcontainers, which is also ASL 2.0 licensed. I'm looking forward to the discussion about this. Best regards, Lari Hotari
