# KafkaJSConnectionErrorMetadata

**Kind:** Interface

**Source:** [`packages/microservices/external/kafka.interface.ts`](https://github.com/nestjs/nest/blob/master/packages/microservices/external/kafka.interface.ts#L1299)

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

`KafkaJSConnectionErrorMetadata` describes connection-specific metadata reported when a KafkaJS broker connection fails. It identifies the affected broker endpoint and the associated Kafka error code, allowing microservice error handling and logging to provide actionable diagnostics.

## Properties

| Property | Type |
|---|---|
| `broker` | `string` |
| `code` | `string` |

## Diagram

```mermaid
graph LR
  A[KafkaJS broker connection attempt] --> B{Connection error}
  B --> C[KafkaJSConnectionErrorMetadata]
  C --> D[broker: string]
  C --> E[code: string]
  C --> F[Logging / retry / error handling]
```

## Usage

```ts
import type { KafkaJSConnectionErrorMetadata } from './kafka.interface';

function logKafkaConnectionError(
  metadata: KafkaJSConnectionErrorMetadata,
): void {
  console.error(
    `Kafka connection failed for broker ${metadata.broker} (${metadata.code})`,
  );
}

const connectionError: KafkaJSConnectionErrorMetadata = {
  broker: 'localhost:9092',
  code: 'ECONNREFUSED',
};

logKafkaConnectionError(connectionError);
```

## AI Coding Instructions

- Always provide both `broker` and `code` when creating this metadata object.
- Use the broker value to identify the exact Kafka endpoint, typically in `host:port` format.
- Preserve the original KafkaJS or Node.js connection error code where possible; do not replace it with a generic message.
- Integrate this metadata into structured logs, retry decisions, and exception diagnostics.
- Avoid storing credentials or sensitive connection details in the `broker` field.