# KafkaJSTopicMetadataNotLoadedMetadata

**Kind:** Interface

**Source:** [`packages/microservices/external/kafka.interface.ts`](https://github.com/nestjs/nest/blob/master/packages/microservices/external/kafka.interface.ts#L1313)

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

`KafkaJSTopicMetadataNotLoadedMetadata` identifies a Kafka topic whose metadata has not yet been loaded by the KafkaJS integration. It is used as lightweight context for metadata-loading errors, retries, or diagnostic logging within the microservices Kafka transport layer.

## Properties

| Property | Type |
|---|---|
| `topic` | `string` |

## Diagram

```mermaid
graph LR
  A[Kafka Client Operation] --> B{Topic metadata loaded?}
  B -->|Yes| C[Use topic metadata]
  B -->|No| D[KafkaJSTopicMetadataNotLoadedMetadata]
  D --> E[topic: string]
  D --> F[Error handling, retry, or logging]
```

## Usage

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

function reportMissingTopicMetadata(
  metadata: KafkaJSTopicMetadataNotLoadedMetadata,
): void {
  console.warn(
    `Kafka metadata has not been loaded for topic: ${metadata.topic}`,
  );
}

const missingMetadata: KafkaJSTopicMetadataNotLoadedMetadata = {
  topic: 'orders.created',
};

reportMissingTopicMetadata(missingMetadata);
```

## AI Coding Instructions

- Provide a non-empty Kafka topic name through the required `topic` field.
- Use this interface only for contexts where topic metadata is unavailable or not yet initialized.
- Preserve the exact topic name used by Kafka; avoid transforming or normalizing it before logging or error reporting.
- Integrate instances with KafkaJS metadata lookup, retry, and diagnostic error-handling paths.