# NatsRecordBuilder

**Kind:** Class

**Source:** [`packages/microservices/record-builders/nats.record-builder.ts`](https://github.com/nestjs/nest/blob/master/packages/microservices/record-builders/nats.record-builder.ts#L14)

**Part of:** [Microservices](subsystem-packages-microservices)

`NatsRecordBuilder` creates a `NatsRecord` for NATS-based microservice messages. Use it to attach message data and optional NATS headers before building the record passed to a NATS client.

## Methods

| Method | Signature | Returns |
|---|---|---|
| `setHeaders` | `setHeaders(headers: THeaders)` | `this` |
| `setData` | `setData(data: TData)` | `this` |
| `build` | `build()` | `NatsRecord` |

## Diagram

```mermaid
graph LR
  A[Application Data] --> B[NatsRecordBuilder]
  C[NATS Headers] --> B
  B -->|setData / setHeaders| D[build()]
  D --> E[NatsRecord]
  E --> F[NATS Client Message]
```

## Usage

```ts
import { NatsRecordBuilder } from '@nestjs/microservices';
import { headers } from 'nats';

const messageHeaders = headers();
messageHeaders.set('x-request-id', 'request-123');
messageHeaders.set('x-source', 'orders-service');

const record = new NatsRecordBuilder()
  .setData({
    orderId: 'order-456',
    status: 'created',
  })
  .setHeaders(messageHeaders)
  .build();

// Example: pass the record to a NATS client
client.emit('orders.created', record);
```

## AI Coding Instructions

- Use `setData()` to provide the payload that NATS consumers should receive.
- Use `setHeaders()` only with valid NATS header objects, not plain JavaScript objects.
- Call `build()` after configuring the builder; send the resulting `NatsRecord` through the NATS client.
- Preserve correlation, tracing, and request metadata in headers when integrating with distributed services.
- Avoid mutating the payload or headers after building when the record may be reused or sent asynchronously.

## Used by

1 reference from 1 file. Each is a place in this repository where the symbol is actually used — go read one rather than trusting an example.

### Imported by (1)

- `NatsController` — `integration/microservices/src/nats/nats.controller.ts`:19