What is the @Payload() decorator and how do you use @Ctx() to access transport-specific context in NestJS microservices?

Q: What is the @Payload() decorator and how do you use @Ctx() to access transport-specific context in NestJS microservices?

// @Payload() with ValidationPipe @MessagePattern({ cmd: 'create_order' }) createOrder( @Payload(new ValidationPipe()) data: CreateOrderDto, ): Promise { return this.ordersService.create(data); } // @Ctx() — TCP context for pattern metadata @MessagePattern({ cmd: 'get_order' }) getOrder( @Payload() data: { id: number }, @Ctx() ctx: TcpContext, ): Promise { console.log(ctx.getPattern()); // { cmd: 'get_order' } return this.ordersService.findOne(data.id); } // @Ctx() — RabbitMQ context for manual acknowledgement @EventPattern('order_placed') async handleOrder( @Payload() data: OrderPlacedEvent, @Ctx() ctx: RmqContext, ): Promise { const channel = ctx.getChannelRef(); const originalMsg = ctx.getMessage(); try { await this.ordersService.process(data); channel.ack(originalMsg); } catch { channel.nack(originalMsg, false, true); // requeue } } TcpContext — getPattern() returns the message pattern object. RmqContext — getChannelRef() returns the AMQP channel; getMessage() returns the raw message for ack/nack. KafkaContext — getTopic(), getPartition(), getMessage() with offset and headers. NatsContext — getHeaders() returns NATS message headers. @Payload(new ValidationPipe()) validates message data the same way @Body(new ValidationPipe()) validates HTTP bodies.

Difficulty: 5/10

NestJS microservices, decorators, transport context

@Payload() extracts the message data and can accept a ValidationPipe for automatic validation. @Ctx() injects the transport-specific context object — RmqContext for RabbitMQ, KafkaContext for Kafka, TcpContext for TCP. Context objects expose transport metadata like channel references, partition numbers, and message offsets.

@Payload() with validation and @Ctx() for transport context

Context types by transport:

1
TcpContext — getPattern() returns the message pattern object.
2

What is the @Payload() decorator and how do you use @Ctx() to access transport-specific context in NestJS microservices?

Difficulty: 5/10

NestJS microservices, decorators, transport context

@Payload() extracts the message data and can accept a ValidationPipe for automatic validation. @Ctx() injects the transport-specific context object — RmqContext for RabbitMQ, KafkaContext for Kafka, TcpContext for TCP. Context objects expose transport metadata like channel references, partition numbers, and message offsets.

@Payload() with validation and @Ctx() for transport context

Context types by transport:

1
TcpContext — getPattern() returns the message pattern object.
2

What is the @Payload() decorator and how do you use @Ctx() to access transport-specific context in NestJS microservices?

What is the @Payload() decorator and how do you use @Ctx() to access transport-specific context in NestJS microservices?

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