CPS-821 Spike: Support Async read-write operations on CPS-NCMP interface

This spike is a WIP

CPS-821 - Getting issue details... STATUS

Description/Scope

The scope of this spike is to ascertain:

How to use messaging (producer, agree topic etc))
Using existing rest endpoint with additional flag indicating async response
Also consider asynchronous request option using messaging in the proposal

Associated Jira Created for Implementation

Key	Summary	T	Created	Updated	Due	Assignee	Reporter	P	Status	Resolution

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Issues/Decisions

#	Issue	Notes/Jira
1	What topic to use? proposed ncmp-async-xxx
2	Are adding a new REST endpoint for async or modifying an existing endpoint?	CPS-830 - Getting issue details... STATUS
3	Agree URL for async once #2 is clarified
4	passthrough request need to be able to handle different response types (using accept header) but the async option would have a fixed and possibly different response type.
5	How many messages are we expecting at peak time?
6	Should we create a standalone app to demo or are tests sufficient?
7	Do we need to persist the generated requestID?
8	Will cps-temporal require the requestID?

Proposed Diagram

Rest Endpoint with Async Flag

Current	Proposed
<ncmp>/v1/ch/PNFDemo/data/ds/ncmp-datastore:passthrough-running?resourceIdentifier=stores:bookstore	<ncmp>/v1/ch/PNFDemo/data/async/ds/ncmp-datastore:passthrough-running?resourceIdentifier=stores:bookstore

Kafka config & Implementation

Example of Existing Consumer (Java)

The below code snippet taken from cps-temporal can be used in the same way in NCMP to listen to message from DMI substituting the topics and errorHandler

Example Listener (Java, cps-temporal)

 /**
     * Consume the specified event.
     *
     * @param cpsDataUpdatedEvent the data updated event to be consumed and persisted.
     */
    @KafkaListener(topics = "${app.listener.data-updated.topic}", errorHandler = "dataUpdatedEventListenerErrorHandler")
    public void consume(final CpsDataUpdatedEvent cpsDataUpdatedEvent) {

        log.debug("Receiving {} ...", cpsDataUpdatedEvent);

        // Validate event envelop
        validateEventEnvelop(cpsDataUpdatedEvent);

        // Map event to entity
        final var networkData = this.cpsDataUpdatedEventMapper.eventToEntity(cpsDataUpdatedEvent);
        log.debug("Persisting {} ...", networkData);

        // Persist entity
        final var persistedNetworkData = this.networkDataService.addNetworkData(networkData);
        log.debug("Persisted {}", persistedNetworkData);

    }

Example of Existing Consumer (Config)

Example of Existing Consumer (Config)

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# Spring profile configuration for sasl ssl Kafka

spring:
    kafka:
        bootstrap-servers: ${KAFKA_BOOTSTRAP_SERVER}
        security:
            protocol: SASL_SSL
        ssl:
            trust-store-type: JKS
            trust-store-location: ${KAFKA_SSL_TRUST_STORE_LOCATION}
            trust-store-password: ${KAFKA_SSL_TRUST_STORE_PASSWORD}
        properties:
            sasl.mechanism: SCRAM-SHA-512
            sasl.jaas.config: ${KAFKA_SASL_JAAS_CONFIG}
            ssl.endpoint.identification.algorithm:

Example of Existing Producer (Java)

Example of Existing Producer (Config)

Example of Kafka Docker-Compose

Kafka Docker Example

  kafka:
    image: confluentinc/cp-kafka:6.1.1
    container_name: kafka
    ports:
      - "19092:19092"
    depends_on:
      - zookeeper
    environment:
      KAFKA_BROKER_ID: 1
      KAFKA_ZOOKEEPER_CONNECT: zookeeper:2181
      KAFKA_ADVERTISED_LISTENERS: PLAINTEXT://kafka:9092,CONNECTIONS_FROM_HOST://localhost:19092
      KAFKA_LISTENER_SECURITY_PROTOCOL_MAP: PLAINTEXT:PLAINTEXT,CONNECTIONS_FROM_HOST:PLAINTEXT
      KAFKA_OFFSETS_TOPIC_REPLICATION_FACTOR: 1

Response types for passthrough

Will we be able to handle everything "as-is"?

Future (or alternative)

What are Futures?

CompletableFuture (Java8+)

Java 8 introduced the CompletableFuture class. Along with the Future interface, it also implemented the CompletionStage interface. This interface defines the contract for an asynchronous computation step that we can combine with other steps.

CompletableFuture is at the same time a building block and a framework, with about 50 different methods for composing, combining, and executing asynchronous computation steps and handling errors.

Simple Future Example

public Future<String> calculateAsync() throws InterruptedException {
    CompletableFuture<String> completableFuture = new CompletableFuture<>();

    Executors.newCachedThreadPool().submit(() -> {
        Thread.sleep(500);
        completableFuture.complete("Hello");
        return null;
    });

    return completableFuture;
}

source: https://www.baeldung.com/java-completablefuture

Alternatives

Thread Example

int number = 20;
Thread newThread = new Thread(() -> {
    System.out.println("Factorial of " + number + " is: " + factorial(number));
});
newThread.start();

#	Type	Pros	Cons	Recommend
1	Future
2	Thread

RequestID Generation

Type	Method	Ease of implementation	Recommend
UUID	`String uniqueID = UUID.randomUUID().toString();`	Easy	Y
Custom	We generate our own	Medium - Hard	N

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