...

-> DMaaP (Kafka/Zookeeper backend)
-> Kafka (Kafka/Strimzi backend)
-> UEB
-> NOOP
-> Http Servers
-> Http Clients

What changes are needed in Policy framework application properties?

Following are the properties for topicSources and topicSinks used across all the applications in policy-framework to communicate with certain endpoints. 

...

Changing topicCommInfrastructure: kafka in application propertiesshould be able to allow messaging to be carried over Kafka.

Additional optional kafka properties needed in application properties of any spring-boot application

spring:
  kafka:
    template:
      default-topic: POLICY-PDP-PAP
    consumer:
      bootstrap-servers: localhost:9092,localhost:9093,localhost:9094
      key-deserializer: org.apache.kafka.common.serialization.IntegerDeserializer
      value-deserializer: org.apache.kafka.common.serialization.StringDeserializer
      group-id: pap-group
    producer:
      bootstrap-servers: localhost:9092,localhost:9093,localhost:9094
      key-serializer: org.apache.kafka.common.serialization.IntegerSerializer
      value-serializer: org.apache.kafka.common.serialization.StringSerializer

...

How to run Kafka?

Kafka dependencies to be added in policy-endpoints/pom.xml of policy/common repoInstall any latest stable version of Kafka, edit the server.properties as desired and run

~/ONAP/kafka_2.12-3.1.0# ls
bin  config  data  libs  LICENSE  licenses  logs  NOTICE  site-docs
~/ONAP/kafka_2.12-3.1.0# bin/kafka-server-start.sh config/server.properties

POLICY-ENDPOINTS

Kafka dependencies to be added in policy-endpoints/pom.xml of policy/common repo

 bin/kafka-server-start.sh config/server.properties

What changes are needed in POLICY-ENDPOINTS codebase?

Kafka dependencies to be added in policy-endpoints/pom.xml of policy/common repo

       <dependency>
            <groupId>org.springframework.kafka</groupId>
            <artifactId>spring-kafka</artifactId>
            <version>2.7.2</version>
        </dependency>
       <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot<kafka</groupId>
            <artifactId>spring-boot-starter-test<kafka</artifactId>
            <scope>test</scope><version>2.7.2</version>
        </dependency>

New communciation communication infrastructure type to be introduced in policy-endpoints/src/main/java/org/onap/policy/common/endpoints/event/comm/Topic.java

...

        policy-endpoints/src/main/java/org/onap/policy/common/endpoints/event/comm/bus/KafkaTopicEndpoint.java
        policy-endpoints/src/main/java/org/onap/policy/common/endpoints/event/comm/bus/KafkaTopicFactories.java
        policy-endpoints/src/main/java/org/onap/policy/common/endpoints/event/comm/bus/KafkaTopicFactory.java
        policy-endpoints/src/main/java/org/onap/policy/common/endpoints/event/comm/bus/KafkaTopicSink.java
        policy-endpoints/src/main/java/org/onap/policy/common/endpoints/event/comm/bus/KafkaTopicSinkFactory.java
        policy-endpoints/src/main/java/org/onap/policy/common/endpoints/event/comm/bus/KafkaTopicSource.java
        policy-endpoints/src/main/java/org/onap/policy/common/endpoints/event/comm/bus/KafkaTopicSourceFactory.java

Why Spring Kafka?

Spring Kafka brings the simple Spring template programming model with a KafkaTemplate and Message-driven POJOs via @KafkaListener annotation.

...

kafkaTemplate.send(<topic>, <message>);

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How to start a sample policy participant application with Kafka?

@SpringBootApplication
@ComponentScan({
    "org.onap.policy.clamp.controlloop.participant.policy",
    "org.onap.policy.clamp.controlloop.participant.intermediary",
    "org.onap.policy.common.endpoints.event.comm.kafka"})
@ConfigurationPropertiesScan("org.onap.policy.clamp.controlloop.participant.policy.main.parameters")
public class PolicyParticipantApplication {
    public static void main(String[] args) {
        SpringApplication.run(PolicyParticipantApplication.class, args);
    }
}

...

• policy-common is not converted to Springboot.
• Policy-endpoint classes are being converted to Springboot components to acheive achieve reuse.

Summary

• Policy-framework applications and current communication infrastructure will-not experience any code changes
• Include Kafka properties and change topicCommInfrastructure to Kafka, if communication if desired over Kafka then current Dmaap communication
• Run Kafka with needed server properties instead of Dmaap
• This endpoint will be a managed end-point and lifecycle management will be taken care by repsective respective changes in policy-common repo.

...