Q- Fisrt Iteration 

Certainly! Let's create a step-by-step tutorial to build a **Reactive Kafka Consumer and Producer** using **Spring Boot**. This guide will help you set up a project similar to the [example-reactive-spring-kafka-consumer-and-producer](https://github.com/Kevded/example-reactive-spring-kafka-consumer-and-producer) repository.

## Table of Contents

1. [Prerequisites](https://yuntian-deng-o1mini.hf.space/?__theme=light#prerequisites)
2. [Project Setup](https://yuntian-deng-o1mini.hf.space/?__theme=light#project-setup)
3. [Add Necessary Dependencies](https://yuntian-deng-o1mini.hf.space/?__theme=light#add-necessary-dependencies)
4. [Define Data Transfer Objects (DTOs)](https://yuntian-deng-o1mini.hf.space/?__theme=light#define-data-transfer-objects-dtos)
5. [Configure Kafka Consumer and Producer](https://yuntian-deng-o1mini.hf.space/?__theme=light#configure-kafka-consumer-and-producer)
6. [Implement Reactive Services](https://yuntian-deng-o1mini.hf.space/?__theme=light#implement-reactive-services)
7. [Testing the Application](https://yuntian-deng-o1mini.hf.space/?__theme=light#testing-the-application)
8. [Running the Application](https://yuntian-deng-o1mini.hf.space/?__theme=light#running-the-application)
9. [Conclusion](https://yuntian-deng-o1mini.hf.space/?__theme=light#conclusion)

---

## Prerequisites

Before starting, ensure you have the following installed on your machine:

- **Java Development Kit (JDK) 8 or higher**
- **Maven** for project management and build
- **Apache Kafka** running locally or accessible remotely
- An **IDE** like IntelliJ IDEA or Eclipse (optional but recommended)

### Installing Apache Kafka Locally

1. **Download Kafka**: [Apache Kafka Downloads](https://kafka.apache.org/downloads)
2. **Extract the archive**:
    
    `tar -xzf kafka_2.13-3.2.0.tgz
    cd kafka_2.13-3.2.0`
    
3. **Start ZooKeeper**:
    
    `bin/zookeeper-server-start.sh config/zookeeper.properties`
    
4. **Start Kafka Broker**:
    
    `bin/kafka-server-start.sh config/server.properties`
    
5. **Create Kafka Topics**:
    
    `bin/kafka-topics.sh --create --topic fake_producer_dto_topic --bootstrap-server localhost:9092
    bin/kafka-topics.sh --create --topic fake_consumer_dto_topic --bootstrap-server localhost:9092`
    

---

## Project Setup

1. **Initialize a Spring Boot Project**:
    
    You can use [Spring Initializr](https://start.spring.io/) or your IDE to create a new project.
    
    - **Project**: Maven Project
    - **Language**: Java
    - **Spring Boot**: 2.3.9 (as per the example)
    - **Project Metadata**:
        - **Group**: `com.example`
        - **Artifact**: `reactive-kafka-consumer-producer`
        - **Name**: `reactive-kafka-consumer-producer`
        - **Package Name**: `com.example.reactivekafkaconsumerandproducer`
        - **Packaging**: Jar
        - **Java**: 8 or higher
2. **Directory Structure**:
    
    Align your project structure as follows for clarity:
    
    `reactive-kafka-consumer-producer/
    ├── src/
    │   ├── main/
    │   │   ├── java/com/example/reactivekafkaconsumerandproducer/
    │   │   │   ├── config/
    │   │   │   ├── dto/
    │   │   │   ├── service/
    │   │   │   ├── ReactiveKafkaConsumerProducerApplication.java
    │   │   └── resources/
    │   │       └── application.properties
    │   └── test/
    │       └── java/com/example/reactivekafkaconsumerandproducer/
    └── pom.xml`
    

---

## Add Necessary Dependencies

Update your `pom.xml` to include the required dependencies for Spring Boot, Kafka, and Reactor.

`<project xmlns="http://maven.apache.org/POM/4.0.0" ...><modelVersion>4.0.0</modelVersion><groupId>com.example</groupId><artifactId>reactive-kafka-consumer-producer</artifactId><version>0.0.1-SNAPSHOT</version><name>reactive-kafka-consumer-producer</name><description>Reactive Kafka Consumer and Producer with Spring Boot</description><parent><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-parent</artifactId><version>2.3.9.RELEASE</version><relativePath/> <!-- lookup parent from repository -->
    </parent><properties><java.version>1.8</java.version><reactor.kafka.version>1.3.12</reactor.kafka.version> <!-- Update to latest if needed -->
    </properties><dependencies><!-- Spring Boot Starter -->
        <dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter</artifactId></dependency><!-- Spring Kafka -->
        <dependency><groupId>org.springframework.kafka</groupId><artifactId>spring-kafka</artifactId></dependency><!-- Reactor Kafka -->
        <dependency><groupId>io.projectreactor.kafka</groupId><artifactId>reactor-kafka</artifactId><version>${reactor.kafka.version}</version></dependency><!-- JSON Serialization -->
        <dependency><groupId>org.springframework.kafka</groupId><artifactId>spring-kafka</artifactId></dependency><!-- Lombok (optional for reducing boilerplate code) -->
        <dependency><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId><optional>true</optional></dependency><!-- Testing Dependencies -->
        <dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-test</artifactId><scope>test</scope></dependency><!-- Reactor Test (optional) -->
        <dependency><groupId>io.projectreactor</groupId><artifactId>reactor-test</artifactId><scope>test</scope></dependency></dependencies><build><plugins><!-- Spring Boot Maven Plugin -->
            <plugin><groupId>org.springframework.boot</groupId><artifactId>spring-boot-maven-plugin</artifactId></plugin><!-- Lombok Plugin (optional) -->
            <plugin><groupId>org.apache.maven.plugins</groupId><artifactId>maven-compiler-plugin</artifactId><version>3.8.1</version><configuration><annotationProcessorPaths><path><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId><version>${lombok.version}</version></path></annotationProcessorPaths></configuration></plugin></plugins></build></project>`

**Note**: Ensure that the versions are compatible. Adjust the `reactor.kafka.version` to the latest stable version if necessary.

---

## Define Data Transfer Objects (DTOs)

Create DTOs representing the data you intend to send and consume via Kafka.

### 1. `FakeProducerDTO.java`

`package com.example.reactivekafkaconsumerandproducer.dto;

public class FakeProducerDTO {
    private String id;
    private String message;

    // Constructors
    public FakeProducerDTO() {}

    public FakeProducerDTO(String id, String message) {
        this.id = id;
        this.message = message;
    }

    // Getters and Setters
    // (Alternatively, use Lombok annotations like @Data for brevity)
    public String getId() {
        return id;
    }

    public void setId(String id) {
       this.id = id;
    }

    public String getMessage() {
       return message;
    }

    public void setMessage(String message) {
        this.message = message;
    }

    // toString()
    @Override
    public String toString() {
        return "FakeProducerDTO{id='" + id + "', message='" + message + "'}";
    }
}`

### 2. `FakeConsumerDTO.java`

`package com.example.reactivekafkaconsumerandproducer.dto;

public class FakeConsumerDTO {
    private String id;
    private String content;

    // Constructors
    public FakeConsumerDTO() {}

    public FakeConsumerDTO(String id, String content) {
        this.id = id;
        this.content = content;
    }

    // Getters and Setters
    // (Alternatively, use Lombok annotations like @Data for brevity)
    public String getId() {
        return id;
    }

    public void setId(String id) {
       this.id = id;
    }

    public String getContent() {
       return content;
    }

    public void setContent(String content) {
        this.content = content;
    }

    // toString()
    @Override
    public String toString() {
        return "FakeConsumerDTO{id='" + id + "', content='" + content + "'}";
    }
}`

**Optional**: If you're using Lombok, you can simplify these classes with annotations like `@Data`, `@NoArgsConstructor`, and `@AllArgsConstructor`.

---

## Configure Kafka Consumer and Producer

Configuration is essential for setting up Kafka consumers and producers. We'll create separate configuration classes for each.

### 1. `ReactiveKafkaConsumerConfig.java`

`package com.example.reactivekafkaconsumerandproducer.config;

import com.example.reactivekafkaconsumerandproducer.dto.FakeConsumerDTO;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.boot.autoconfigure.kafka.KafkaProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.kafka.core.reactive.ReactiveKafkaConsumerTemplate;
import reactor.kafka.receiver.ReceiverOptions;

import java.util.Collections;

@Configuration
public class ReactiveKafkaConsumerConfig {

    @Bean
    public ReceiverOptions<String, FakeConsumerDTO> kafkaReceiverOptions(
            @Value("${FAKE_CONSUMER_DTO_TOPIC}") String topic,
            KafkaProperties kafkaProperties) {
        
        ReceiverOptions<String, FakeConsumerDTO> basicReceiverOptions = ReceiverOptions.create(kafkaProperties.buildConsumerProperties());
        return basicReceiverOptions.subscription(Collections.singletonList(topic));
    }

    @Bean
    public ReactiveKafkaConsumerTemplate<String, FakeConsumerDTO> reactiveKafkaConsumerTemplate(
            ReceiverOptions<String, FakeConsumerDTO> kafkaReceiverOptions) {
        return new ReactiveKafkaConsumerTemplate<>(kafkaReceiverOptions);
    }
}`

### 2. `ReactiveKafkaProducerConfig.java`

`package com.example.reactivekafkaconsumerandproducer.config;

import com.example.reactivekafkaconsumerandproducer.dto.FakeProducerDTO;
import org.springframework.boot.autoconfigure.kafka.KafkaProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.kafka.core.reactive.ReactiveKafkaProducerTemplate;
import reactor.kafka.sender.SenderOptions;

import java.util.Map;

@Configuration
public class ReactiveKafkaProducerConfig {

    @Bean
    public ReactiveKafkaProducerTemplate<String, FakeProducerDTO> reactiveKafkaProducerTemplate(KafkaProperties properties) {
        Map<String, Object> props = properties.buildProducerProperties();
        return new ReactiveKafkaProducerTemplate<>(SenderOptions.create(props));
    }
}`

### 3. `application.properties`

Configure your Kafka connection and serialization settings.

`# Kafka Broker Address
spring.kafka.bootstrap-servers=localhost:9092

# Producer Configuration
spring.kafka.producer.key-serializer=org.apache.kafka.common.serialization.StringSerializer
spring.kafka.producer.value-serializer=org.springframework.kafka.support.serializer.JsonSerializer

# Consumer Configuration
spring.kafka.consumer.group-id=reactivekafkaconsumerandproducer
spring.kafka.consumer.auto-offset-reset=earliest
spring.kafka.consumer.key-deserializer=org.apache.kafka.common.serialization.StringDeserializer
spring.kafka.consumer.value-deserializer=org.springframework.kafka.support.serializer.JsonDeserializer

# JSON Deserializer Configuration
spring.kafka.properties.spring.json.trusted.packages=*
spring.kafka.consumer.properties.spring.json.use.type.headers=false
spring.kafka.consumer.properties.spring.json.value.default.type=com.example.reactivekafkaconsumerandproducer.dto.FakeConsumerDTO

# Kafka Topics
FAKE_PRODUCER_DTO_TOPIC=fake_producer_dto_topic
FAKE_CONSUMER_DTO_TOPIC=fake_consumer_dto_topic`

**Notes**:

- **Bootstrap Servers**: Ensure this matches your Kafka broker's address and port.
- **Serialization**:
    - Producers serialize keys and values using `StringSerializer` and `JsonSerializer` respectively.
    - Consumers deserialize keys and values using `StringDeserializer` and `JsonDeserializer` respectively, with options to trust all packages for JSON deserialization.

---

## Implement Reactive Services

We'll create two services: one for producing messages to Kafka and another for consuming messages from Kafka.

### 1. `ReactiveProducerService.java`

`package com.example.reactivekafkaconsumerandproducer.service;

import com.example.reactivekafkaconsumerandproducer.dto.FakeProducerDTO;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.kafka.core.reactive.ReactiveKafkaProducerTemplate;
import org.springframework.stereotype.Service;

@Service
public class ReactiveProducerService {

    private static final Logger log = LoggerFactory.getLogger(ReactiveProducerService.class);
    private final ReactiveKafkaProducerTemplate<String, FakeProducerDTO> reactiveKafkaProducerTemplate;

    @Value("${FAKE_PRODUCER_DTO_TOPIC}")
    private String topic;

    public ReactiveProducerService(ReactiveKafkaProducerTemplate<String, FakeProducerDTO> reactiveKafkaProducerTemplate) {
        this.reactiveKafkaProducerTemplate = reactiveKafkaProducerTemplate;
    }

    public void send(FakeProducerDTO fakeProducerDTO) {
        log.info("Sending to topic={}, DTO={}", topic, fakeProducerDTO);
        reactiveKafkaProducerTemplate.send(topic, fakeProducerDTO)
                .doOnSuccess(senderResult -> log.info("Sent DTO={} to offset={}", fakeProducerDTO, senderResult.recordMetadata().offset()))
                .doOnError(e -> log.error("Error sending DTO={} due to {}", fakeProducerDTO, e.getMessage()))
                .subscribe();
    }
}`

### 2. `ReactiveConsumerService.java`

`package com.example.reactivekafkaconsumerandproducer.service;

import com.example.reactivekafkaconsumerandproducer.dto.FakeConsumerDTO;
import org.apache.kafka.clients.consumer.ConsumerRecord;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.boot.CommandLineRunner;
import org.springframework.kafka.core.reactive.ReactiveKafkaConsumerTemplate;
import org.springframework.stereotype.Service;
import reactor.core.publisher.Flux;

@Service
public class ReactiveConsumerService implements CommandLineRunner {

    private static final Logger log = LoggerFactory.getLogger(ReactiveConsumerService.class);
    private final ReactiveKafkaConsumerTemplate<String, FakeConsumerDTO> reactiveKafkaConsumerTemplate;

    public ReactiveConsumerService(ReactiveKafkaConsumerTemplate<String, FakeConsumerDTO> reactiveKafkaConsumerTemplate) {
        this.reactiveKafkaConsumerTemplate = reactiveKafkaConsumerTemplate;
    }

    private Flux<FakeConsumerDTO> consumeFakeConsumerDTO() {
        return reactiveKafkaConsumerTemplate
                .receiveAutoAck()
                // .delayElements(Duration.ofSeconds(2L)) // Uncomment for backpressure simulation
                .doOnNext(record -> log.info("Received key={}, value={} from topic={}, offset={}",
                        record.key(),
                        record.value(),
                        record.topic(),
                        record.offset()))
                .map(ConsumerRecord::value)
                .doOnNext(dto -> log.info("Successfully consumed: {}", dto))
                .doOnError(e -> log.error("Error while consuming: {}", e.getMessage()));
    }

    @Override
    public void run(String... args) {
        // Trigger consumption upon application startup
        consumeFakeConsumerDTO().subscribe();
    }
}`

### 3. Main Application Class

Ensure you have a main application class to bootstrap the Spring Boot application.

`package com.example.reactivekafkaconsumerandproducer;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class ReactiveKafkaConsumerProducerApplication {

    public static void main(String[] args) {
        SpringApplication.run(ReactiveKafkaConsumerProducerApplication.class, args);
    }
}`

---

## Testing the Application

Creating integration tests ensures that your Kafka consumer and producer are functioning as expected.

### 1. `ReactiveProducerServiceIntegrationTest.java`

`package com.example.reactivekafkaconsumerandproducer;

import com.example.reactivekafkaconsumerandproducer.dto.FakeProducerDTO;
import com.example.reactivekafkaconsumerandproducer.service.ReactiveProducerService;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;

// Optionally, you can use embedded Kafka for testing purposes
@SpringBootTest
public class ReactiveProducerServiceIntegrationTest {

    @Autowired
    private ReactiveProducerService reactiveProducerService;

    @Test
    public void testSend() {
        FakeProducerDTO dto = new FakeProducerDTO("1", "Test Message");
        reactiveProducerService.send(dto);
        // Add assertions or verify via logs
    }
}`

### 2. `ReactiveConsumerServiceIntegrationTest.java`

`package com.example.reactivekafkaconsumerandproducer;

import com.example.reactivekafkaconsumerandproducer.dto.FakeConsumerDTO;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import reactor.test.StepVerifier;

// Optionally, you can use embedded Kafka for testing purposes
@SpringBootTest
public class ReactiveConsumerServiceIntegrationTest {

    @Autowired
    private ReactiveKafkaConsumerTemplate<String, FakeConsumerDTO> reactiveKafkaConsumerTemplate;

    @Test
    public void testConsume() {
        StepVerifier.create(reactiveKafkaConsumerTemplate.receiveAutoAck())
                .expectNextMatches(record -> record.value().getId().equals("1")
                        && record.value().getContent().equals("Test Content"))
                .thenCancel()
                .verify();
    }
}`

**Note**: For robust testing, consider using [Embedded Kafka](https://spring.io/projects/spring-kafka#overview) to run Kafka within your tests.

---

## Running the Application

1. **Start Kafka Broker**: Ensure your Kafka broker is running on `localhost:9092`.
2. **Build the Project**:
    
    Navigate to your project's root directory and run:
    
    `mvn clean install`
    
3. **Run the Spring Boot Application**:
    
    `mvn spring-boot:run`
    
    Upon startup, the `ReactiveConsumerService` will begin consuming messages from the `fake_consumer_dto_topic`.
    
4. **Produce Messages**:  
    
    You can trigger the producer service manually or set up a REST controller to send messages.
    
    **Optional Step**: Create a REST Controller to allow sending messages via HTTP requests.
    
    `package com.example.reactivekafkaconsumerandproducer.controller;
    
    import com.example.reactivekafkaconsumerandproducer.dto.FakeProducerDTO;
    import com.example.reactivekafkaconsumerandproducer.service.ReactiveProducerService;
    import org.springframework.http.ResponseEntity;
    import org.springframework.web.bind.annotation.*;
    
    @RestController
    @RequestMapping("/api")
    public class KafkaController {
    
        private final ReactiveProducerService reactiveProducerService;
    
        public KafkaController(ReactiveProducerService reactiveProducerService) {
            this.reactiveProducerService = reactiveProducerService;
        }
    
        @PostMapping("/send")
        public ResponseEntity<String> sendMessage(@RequestBody FakeProducerDTO dto) {
            reactiveProducerService.send(dto);
            return ResponseEntity.ok("Message sent to Kafka topic");
        }
    }`
    
    **Usage**:
    
    Use tools like **Postman** or **cURL** to send POST requests.
    
    `curl -X POST \
      http://localhost:8080/api/send \
      -H 'Content-Type: application/json' \
      -d '{
            "id": "123",
            "message": "Hello, Kafka!"
          }'`
    
    Upon sending, you should see logs indicating the message was sent and subsequently consumed.
    

---

## Conclusion

You've successfully set up a Reactive Kafka Consumer and Producer using Spring Boot. This setup leverages **Project Reactor** for non-blocking, asynchronous processing, making your application highly scalable and efficient.

### Next Steps

- **Error Handling**: Enhance resilience by implementing comprehensive error handling and retry mechanisms.
- **Backpressure Management**: Fine-tune backpressure strategies to handle varying loads.
- **Security**: Secure your Kafka brokers and implement authentication and authorization as needed.
- **Monitoring**: Integrate monitoring tools like **Prometheus** and **Grafana** to observe Kafka metrics.

---

Feel free to explore and extend this setup according to your application's requirements. Happy coding!

Q- just i want you instead of local kafak  server and zookeper just use docker compose oki 

Q- just reriwe the full tutor just make it using docker compose intead of local bin files