Implementation:Fede1024 Rust rdkafka BorrowedMessage Detach

Knowledge Sources	rust-rdkafka
Domains	Messaging, Memory_Management
Last Updated	2026-02-07 19:00 GMT

Overview

Concrete message detach operation for converting BorrowedMessage to OwnedMessage provided by rust-rdkafka.

Description

BorrowedMessage::detach() copies all message fields from the consumer's internal buffer into new heap allocations, producing an OwnedMessage with static lifetime. The copied fields include: payload (Option<Vec<u8>>), key (Option<Vec<u8>>), topic (String), timestamp (Timestamp), partition (i32), offset (i64), and headers (Option<OwnedHeaders>).

This is a pure Rust operation with no FFI calls. The cost is proportional to the message size (key + payload + headers).

Usage

Call detach() on a BorrowedMessage when you need to send it to another task or store it beyond the consumer buffer's lifetime.

Code Reference

Source Location

• Repository: rust-rdkafka
• File: src/message.rs
• Lines: L411-422

Signature

impl<'a> BorrowedMessage<'a> {
    /// Clones the content of the `BorrowedMessage` and returns an
    /// `OwnedMessage` that can outlive the consumer.
    ///
    /// This operation requires memory allocation and can be expensive.
    pub fn detach(&self) -> OwnedMessage;
}

Import

use rdkafka::message::{BorrowedMessage, OwnedMessage, Message};

I/O Contract

Inputs

Name	Type	Required	Description
&self	&BorrowedMessage<'a>	Yes	Zero-copy message tied to consumer buffer

Outputs

Name	Type	Description
detach() returns	OwnedMessage	Heap-allocated message with payload: Option<Vec<u8>>, key: Option<Vec<u8>>, topic: String, timestamp: Timestamp, partition: i32, offset: i64, headers: Option<OwnedHeaders>

Usage Examples

Detach for Cross-Task Transfer

use rdkafka::consumer::{Consumer, StreamConsumer};
use rdkafka::message::Message;

let borrowed_msg = consumer.recv().await.expect("recv failed");
let owned_msg = borrowed_msg.detach();

// owned_msg can now be sent to another task
tokio::task::spawn_blocking(move || {
    let payload = owned_msg.payload().unwrap_or(&[]);
    // Process payload in blocking context
    expensive_computation(payload)
});

Related Pages

Implements Principle

• Principle:Fede1024_Rust_rdkafka_Message_Ownership_Transfer

Requires Environment

• Environment:Fede1024_Rust_rdkafka_Rust_Librdkafka_Build_Environment