Reactive Systems in Java: Resilient, Event-Driven Architecture with Quarkus

Preface....7 Who Should Read This Book?....8 What About Quarkus?....9 Navigating This Book....9 Getting You Ready....11 Conventions Used in This Book....16 OReilly Online Learning....17 How to Contact Us....18 Acknowledgments....18 I. Reactive and Quarkus Introduction....20 1. Reactive in a Nutshell....21 What Do We Mean by Reactive?....21 Reactive Software Is Not New....22 The Reactive Landscape....23 Why Are Reactive Architectures So Well-Suited for Cloud Native Applications?....27 Reactive Is Not a Silver Bullet....27 2. Introduction to Quarkus....29 Java on the Cloud....29 Thorntail Example....34 Quarkus Example....37 The Quarkus Way....29 Create Your First Quarkus Application....29 Kubernetes with Quarkus in 10 Minutes....29 Going Native....59 Summary....64 II. Reactive and Event-Driven Applications....66 3. The Dark Side of Distributed Systems....67 Whats a Distributed System?....67 The New Kids on the Block: Cloud Native and Kubernetes Native Applications....67 The Dark Side of Distributed Systems....79 Fallacies of Distributed Computing in a Kubernetes World....80 A Question of Timing: The Synchronous Communication Drawback....83 Summary....91 4. Design Principles of Reactive Systems....93 Reactive Systems 101....93 Commands and Events....96 Commands....96 Events....97 Messages....97 Commands Versus Events: An Example....98 Destinations and Space Decoupling....102 Time Decoupling....105 The Role of Nonblocking InputOutput....93 Blocking Network IO, Threads, and Concurrency....107 How Does Nonblocking IO Work?....111 Reactor Pattern and Event Loop....93 Anatomy of Reactive Applications....116 Summary....121 5. Reactive Programming: Taming the Asynchronicity....122 Asynchronous Code and Patterns....122 Using Futures....129 Project Loom: Virtual Threads and Carrier Threads....132 Reactive Programming....122 Streams....137 Operators....139 Reactive Programming Libraries....145 Reactive Streams and the Need for Flow Control....145 Buffering Items....147 Dropping Items....148 What Is Backpressure?....149 Introducing Reactive Streams....149 Be Warned: Its a Trap!....153 Backpressure in Distributed Systems....153 Summary....154 III. Building Reactive Applications and Systems with Quarkus....156 6. Quarkus: Reactive Engine....157 The Imperative Model....157 The Reactive Model....161 Unification of Reactive and Imperative....157 A Reactive Engine....157 A Reactive Programming Model....171 Event-Driven Architecture with Quarkus....172 Summary....173 7. Mutiny: An Event-Driven Reactive Programming API....175 Why Another Reactive Programming Library?....175 What Makes Mutiny Unique?....177 Mutiny Usage in Quarkus....177 Uni and Multi....178 Mutiny and Flow Control....183 Observing Events....184 Transforming Events....185 Chaining Asynchronous Actions....186 Recovering from Failure....189 Combining and Joining Items....190 Selecting Items....192 Collecting Items....193 Summary....194 8. HTTP with Reactive in Mind....195 The Journey of an HTTP Request....196 Say Hello to RESTEasy Reactive!....198 Whats the Benefit?....201 Asynchronous Endpoints Returning Uni....204 Dealing with Failure and Customizing the Response....206 Streaming Data....210 Raw Streaming....210 Streaming JSON Array....212 Using Server-Sent-Events....215 Reactive Score....216 Summary....218 9. Accessing Data Reactively....220 The Problem with Data Access....220 Nonblocking Interactions with Relational Databases....223 Using a Reactive ORM: Hibernate Reactive....227 What About NoSQL?....231 Interacting with Redis....232 Data-Related Events and Change Data Capture....236 Using Debezium to Capture Change....239 Summary....243 IV. Connecting the Dots....245 10. Reactive Messaging: The Connective Tissue....246 From Reactive Applications to Reactive Systems....246 Channels and Messages....247 Producing Messages....248 Consuming Messages....252 Processing Messages....254 Acknowledgments....256 Connectors....258 Building Message-Based Applications....258 Message and Acknowledgment....260 Failures and Negative Acknowledgment....262 Stream Manipulation....263 Blocking Processing....265 Retrying Processing....266 Putting Everything Together....267 Summary....271 11. The Event Bus: The Backbone....272 Kafka or AMQP: Picking the Right Tool....272 Building Reactive Systems with Kafka....273 Apache Kafka....273 Point-to-Point Communication....280 PublishSubscribe....282 Elasticity Patterns....283 Dealing with Failures....284 Backpressure and Performance Considerations....287 Kafka on Kubernetes....272 Building Reactive Systems with AMQP....292 AMQP 1.0....292 Point-to-Point Communication....293 PublishSubscribe....295 Elasticity Patterns....296 Acknowledgment and Redelivery....297 Credit-Flow Backpressure Protocol....298 AMQP on Kubernetes....298 Summary....300 12. Reactive REST Client: Connecting with HTTP Endpoints....302 Interacting with an HTTP Endpoint....302 The REST Client Reactive....305 Mapping HTTP APIs to Java Interfaces....306 Invoking the Service....309 Blocking and Nonblocking....310 Handling Failures....311 Fallback....312 Retries....314 Time-out....315 Bulkheads and Circuit Breaker....315 Building API Gateways with the RESTEasy Reactive Client....317 Using the REST Client in Messaging Applications....324 Summary....328 13. Observing Reactive and Event-Driven Architectures....330 Why Is Observability Important?....330 Health with Messaging....332 Metrics with Messaging....339 Distributed Tracing with Messaging....344 Summary....348 Conclusion....350 A Brief Summary....350 Is That All?....351 The Future of Reactive Systems....352 The End of the Beginning....353 Index....354