KafkaRequestSerializer

Kind: Class

Source: packages/microservices/serializers/kafka-request.serializer.ts

Part of: Microservices

KafkaRequestSerializer prepares outbound Kafka messages for transport by normalizing payloads into Kafka-compatible message objects. It JSON-encodes object and array values while preserving strings, Buffer instances, and null, and applies the same encoding rules to message keys and headers.

Implements: Serializer

Methods

Where it refuses work

• KafkaRequestSerializer stops the work with an early return when isUndefined(value).

Diagram

mermaid
graph LR
  A[Application payload] --> B[KafkaRequestSerializer.serialize]
  B --> C{Kafka message shape?}
  C -- No --> D[Wrap as { value: payload }]
  C -- Yes --> E[Use key, value, and headers]
  D --> F[encode value]
  E --> F
  E --> G[encode key]
  E --> H[encode headers]
  F --> I[Kafka-compatible message]
  G --> I
  H --> I

Usage

ts
import { KafkaRequestSerializer } from '@nestjs/microservices';

const serializer = new KafkaRequestSerializer();

const message = serializer.serialize({
  key: { tenantId: 'tenant-42' },
  value: {
    event: 'order.created',
    orderId: 'order-123',
  },
  headers: {
    correlationId: 'request-abc',
    metadata: { source: 'checkout' },
  },
});

console.log(message);
// {
//   key: '{"tenantId":"tenant-42"}',
//   value: '{"event":"order.created","orderId":"order-123"}',
//   headers: {
//     correlationId: 'request-abc',
//     metadata: '{"source":"checkout"}'
//   }
// }

AI Coding Instructions

• Pass plain payloads or Kafka message-shaped objects containing value, optionally with key and headers.
• Keep string values and Buffer values as-is; objects and arrays are automatically serialized with JSON.stringify.
• Ensure objects placed in key, value, or headers are JSON-serializable to avoid runtime serialization failures.
• Use Buffer explicitly when producing binary Kafka payloads rather than relying on JSON encoding.
• Preserve Kafka message fields when extending this serializer, especially key, value, and headers.