README.md

A progressive Node.js framework for building efficient and scalable server-side applications.

Description

Process and Publish Kafka message by batch in NestJS. Cross compatible with ServerKafka and ClientKafka from @nestjs/microservices package.

Installation

$ npm i --save @tawkto/nestjs-batch-kafka

Overview

To use the batch kafka consumer, initialize BatchKafkaServer in your main.ts file by connecting the microservice to your app.

const app = await NestFactory.createMicroservice<MicroserviceOptions>(AppModule, {
	// The config is the same as the KafkaOptions from the @nestjs/microservices package
	strategy: new KafkaBatchServer({
		client: {
			brokers: ['localhost:52800', 'localhost:52801'],
        },
        consumer: {
          groupId: 'test',
          heartbeatInterval: 5000,
          sessionTimeout: 30000,
        },
        run: {
          autoCommitInterval: 5000,
          autoCommitThreshold: 100,
          partitionsConsumedConcurrently: 4,
        },
	})
})

Then you can start consuming the events in batches as follow

@BatchProcessor('test')
  async test(
    @Payload() data: any[],
    @Ctx() context: KafkaBatchContext,
  ) {
    const heartbeat = context.getHeartbeat();
    const resolveOffset = context.getResolveOffset();
    const commitOffsetsIfNecessary = context.getCommitOffsetsIfNecessary();

    await heartbeat();

    for (const message of data) {
      console.log(message);
    }

    resolveOffset(context.getMessages().at(-1).offset);
    console.log("Batch resolved");

    await heartbeat();
    await commitOffsetsIfNecessary();
  }

Context

The KafkaBatchContext object provides the necessary components from kafkajs's EachBatchPayload:

Method	Type	Description
getMessages	KafkaMessage[]	Get the raw messages from Kafka in the batch
getConsumer	KafkaConsumer	Get the consumer instance
getResolveOffset	function	Get the resolve offset method
getHeartbeat	function	Get the heartbeat method
getPause	function	Get the pause method
getCommitOffsetsIfNecessary	function	Get the commit offsets if necessary method
getUncommittedOffsets	OffsetsByTopicPartition	Get the uncommitted offsets
getIsRunning	boolean	Indicate if the consumer is still running
getIsStale	boolean	Indicate if the consumer is stale

Client

The KafkaBatchClient is exactly the same as the KafkaClient from the @nestjs/microservices package, except that client.send method is removed from the client as batch messages should not be used for request-response communication. On top of that, KafkaBatchClient also have the capability to publish batch messages or publish to multiple topics just like in kafkajs.

@Module({
	imports: [
		ClientsModule.register([{
			name: 'KAFKA_BATCH_CLIENT',
			customClass: KafkaBatchClient,
			options: {
				client: {
				brokers: ['localhost:52800', 'localhost:52801'],
				},
				consumer: {
				groupId: 'test',
				heartbeatInterval: 5000,
				sessionTimeout: 30000,
				},
			},
		}]),
	],
})
export class AppModule {}

Then you can inject and use the KafkaBatchClient in your service as follow

@Injectable()
export class AppService {
	constructor(
		@Inject('KAFKA_BATCH_CLIENT')
		private kafkaClient: KafkaBatchClient,
	) {}

	async eventToBatch() {
		this.kafkaClient.emit('test', { example: 'data'});
	}

	async publishBatch() {
		// equivalent to kafkajs producer.send
		this.kafkaClient.emitBatch('test', [{
			example: 'data1'
		}, {
			example: 'data2'
		}])
	}

	async publishBatchTopics() {
		// will publish to two topics, topic1 and topic2
		// equivalent to kafkajs producer.publishBatch
		this.kafkaClient.emitBatchTopics([{
			pattern: 'topic1',
			data: [{ example: 'data11' }, { example: 'data12' }]
		}, {
			pattern: 'topic2',
			data: [{ example: 'data21' }, { example: 'data22' }]
		}])
	}
}

Calling send with the KafkaBatchClient will result in an error.

this.kafkaClient.send('send', { data: 'data'}); // Error