KafkaRequestDeserializer

Kind: Class

Source: packages/microservices/deserializers/kafka-request.deserializer.ts

Part of: Microservices

KafkaRequestDeserializer converts raw Kafka request records into the internal IncomingRequest or IncomingEvent schema used by the microservices layer. It extracts the Kafka message key as the request pattern and forwards the message value as the payload, allowing downstream handlers to process Kafka messages consistently with other transports.

Extends: IncomingRequestDeserializer

Methods

Where it refuses work

• KafkaRequestDeserializer stops the work with an early return when !options.

Diagram

mermaid
graph LR
  A[Kafka broker message] --> B[KafkaRequestDeserializer]
  B --> C{Message has a value?}
  C -->|Yes| D[IncomingRequest / IncomingEvent]
  D --> E[pattern: Kafka key]
  D --> F[data: Kafka value]
  C -->|No| G[Return original data]

Usage

ts
import { KafkaRequestDeserializer } from '@nestjs/microservices/deserializers/kafka-request.deserializer';

const deserializer = new KafkaRequestDeserializer();

const kafkaMessage = {
  key: Buffer.from('orders.create'),
  value: {
    orderId: 'order-123',
    customerId: 'customer-456',
  },
};

const incomingMessage = deserializer.mapToSchema(kafkaMessage);

console.log(incomingMessage);
// {
//   pattern: 'orders.create',
//   data: {
//     orderId: 'order-123',
//     customerId: 'customer-456'
//   }
// }

AI Coding Instructions

• Preserve the Kafka convention: use the message key as the handler pattern and the message value as the payload.
• Handle malformed or value-less Kafka records defensively; the deserializer should not assume every input has a value property.
• Keep output compatible with the shared IncomingRequest and IncomingEvent contracts used by microservice transport handlers.
• When extending Kafka message handling, avoid mutating the original Kafka record or its payload.
• Configure this deserializer at the Kafka transport boundary so application handlers receive normalized messages.