Principle:Fede1024 Rust rdkafka Topic Subscription And Consumption
| Knowledge Sources | |
|---|---|
| Domains | Messaging, Async_Programming |
| Last Updated | 2026-02-07 19:00 GMT |
Overview
A mechanism for subscribing to Kafka topics and asynchronously receiving messages one at a time with consumer group coordination.
Description
Topic Subscription and Consumption is the consumer-side complement to message production. A consumer joins a consumer group, subscribes to one or more topics, and receives messages that are automatically load-balanced across group members via partition assignment. The consumer group protocol handles membership, heartbeats, and rebalancing.
The async consumption model provides a simple recv() interface that awaits the next available message. Under the hood, the consumer uses a waker-based system to efficiently bridge librdkafka's C event queue with Rust's async runtime. Messages must be consumed at least every max.poll.interval.ms to avoid being kicked from the consumer group.
After processing, messages can be committed (manually or automatically) to track consumption progress.
Usage
Use this principle when you need to consume messages from Kafka topics in an async application. Subscribe to topics using subscribe(), then loop calling recv() to get messages. Commit offsets after processing to track progress. This is the simplest consumption pattern, suitable for most use cases.
Theoretical Basis
Consumer group coordination uses a cooperative protocol:
Pseudo-code logic:
// Abstract algorithm
consumer.subscribe(&["topic-a", "topic-b"])
loop {
message = consumer.recv().await // async wait for next message
process(message)
consumer.commit_message(message, CommitMode::Async)
}
The consumer group protocol ensures each partition is assigned to exactly one consumer in the group, providing both parallelism and ordering guarantees within partitions.