TopicMessages

Kind: Interface

Source: packages/microservices/external/kafka.interface.ts

Part of: Microservices

TopicMessages groups a collection of Kafka Message objects under a single topic name. It is used when producing or handling batches of messages that should be sent to the same Kafka topic within the microservices integration layer.

Properties

Diagram

mermaid
graph LR
  T[TopicMessages] --> Topic[topic: string]
  T --> Messages[messages: Message[]]
  Messages --> M1[Kafka Message]
  Messages --> M2[Kafka Message]

Usage

ts
import type { Message } from 'kafkajs';
import type { TopicMessages } from './kafka.interface';

const messages: Message[] = [
  {
    key: 'user-123',
    value: JSON.stringify({
      event: 'user.created',
      userId: 'user-123',
    }),
  },
];

const topicMessages: TopicMessages = {
  topic: 'user-events',
  messages,
};

// Example: pass grouped messages to a Kafka producer operation.
await producer.send({
  topic: topicMessages.topic,
  messages: topicMessages.messages,
});

AI Coding Instructions

• Always provide a non-empty topic that matches the configured Kafka topic naming conventions.
• Populate messages with Kafka-compatible Message objects, including serialized value payloads where required.
• Group only messages targeting the same topic in a single TopicMessages object.
• Preserve message keys when ordering, partition affinity, or consumer routing depends on them.
• Validate payload serialization and topic configuration before passing this object to producer APIs.

How it works

TopicMessages is an exported TypeScript interface in a file intended to represent KafkaJS package types rather than NestJS logic. packages/microservices/external/kafka.interface.ts:1-4 packages/microservices/external/kafka.interface.ts:759-762

It describes one topic’s set of producer messages:

• topic is required and has type string. packages/microservices/external/kafka.interface.ts:759-761
• messages is required and has type Message[]. packages/microservices/external/kafka.interface.ts:759-762
• Each Message requires a value of Buffer, string, or null; it can also contain an optional key, partition, headers, and timestamp. packages/microservices/external/kafka.interface.ts:121-127

ProducerBatch.topicMessages optionally accepts an array of TopicMessages, and sendBatch accepts that ProducerBatch and returns Promise<RecordMetadata[]>. packages/microservices/external/kafka.interface.ts:764-769 packages/microservices/external/kafka.interface.ts:785-788

This interface declares no runtime validation, thrown errors, or side effects. packages/microservices/external/kafka.interface.ts:759-762