ClientKafka

Kind: Class

Source: packages/microservices/client/client-kafka.ts

Part of: Microservices

ClientKafka is a NestJS microservices client proxy for producing Kafka messages and consuming response messages for request-response patterns. It manages Kafka producer and consumer lifecycle, topic subscriptions, response callbacks, offset commits, and access to the underlying Kafka client.

Extends: ClientProxy

Implements: ClientKafkaProxy

Methods

Properties

Where it refuses work

• ClientKafka stops the work with Error when !this._consumer — “No consumer initialized. Please, call the "connect" method first.”.
• ClientKafka stops the work with Error when !this._producer — “No producer initialized. Please, call the "connect" method first.”.
• ClientKafka stops the work with Error when !this.client — “Not initialized. Please call the "connect" method first.”.
• ClientKafka stops the work with InvalidKafkaClientTopicException when isUndefined(minimumPartition).
• ClientKafka stops the work with an early return when this.initialized.
• ClientKafka stops the work with an early return when !this._consumer.

When something fails

• ClientKafka handles failure in 1 place: it turns it into a return value in all 1.

Diagram

mermaid
graph LR
  A[Application Service] --> B[ClientKafka]
  B --> C[Kafka Producer]
  B --> D[Kafka Consumer]
  C --> E[Request / Event Topics]
  E --> F[Kafka Brokers]
  F --> G[Response Topics]
  G --> D
  D --> H[Response Callback]
  H --> A

AI Coding Instructions

• Call subscribeToResponseOf(pattern) before connect() when using send() for Kafka request-response messaging.
• Use send() for request-response flows and emit() or emitBatch() for event-driven, fire-and-forget publishing.
• Always close the client during application shutdown to disconnect the Kafka producer and consumer cleanly.
• Keep Kafka client and consumer settings, especially clientId, broker addresses, and consumer groupId, consistent with deployment configuration.
• Use unwrap() only when direct access to the underlying KafkaJS client is required; prefer the ClientKafka APIs for normal messaging.

Relationships

• IMPORTS → Logger
• IMPORTS → loadPackage
• IMPORTS → isNil
• IMPORTS → isUndefined

Used by

2 references from 2 files. Each is a place in this repository where the symbol is actually used — go read one rather than trusting an example.

Imported by (2)

• KafkaController — integration/microservices/src/kafka/kafka.controller.ts:15
• KafkaConcurrentController — integration/microservices/src/kafka-concurrent/kafka-concurrent.controller.ts:24