Peek Messages

Overview

Peeking lets you look at what's sitting in a queue without touching it — the messages stay exactly where they are, still waiting for whichever consumer eventually receives them. It's the tool you reach for when you need visibility into queue state — checking backlog depth, inspecting payloads while debugging a stuck pipeline, or building an operational dashboard — without risking a collision with real consumers competing for the same work.

receive_queue_messages(channel, max_messages, wait_timeout_seconds, is_peek) is the same call your consumers use, just with the is_peek flag set to true: the broker returns a snapshot of messages currently queued but never marks them as delivered, locks them, or starts a visibility timeout — so no acknowledgment is needed or even possible.

Gotchas: peeked messages aren't reserved for you — a consumer calling with is_peek=false can remove them the instant after you peek, so treat the count as a point-in-time estimate, not a guarantee. Peek also won't surface messages already locked inside another consumer's in-flight receive, and it's not a substitute for receiving when you actually intend to process what you see.

Prerequisites

• KubeMQ server running on localhost:50000
• Rust SDK installed (cargo add kubemq)

Code

use kubemq::prelude::*;
use kubemq::QueueMessageBuilder;

#[tokio::main]
async fn main() -> kubemq::Result<()> {
    let client = KubemqClient::builder()
        .host("localhost")
        .port(50000)
        .build()
        .await?;

    let channel = "rust-queues.peek-messages";

    let msg = QueueMessageBuilder::new()
        .channel(channel)
        .body(b"peek-at-me".to_vec())
        .build();
    client.send_queue_message(msg).await?;

    let peeked = client.receive_queue_messages(channel, 10, 5, true).await?;
    println!("Peeked {} messages (still in queue)", peeked.len());

    for m in &peeked {
        println!("  id={}, body={}", m.id, String::from_utf8_lossy(&m.body));
    }

    let consumed = client.receive_queue_messages(channel, 10, 5, false).await?;
    println!("Consumed {} messages", consumed.len());

    client.close().await?;
    Ok(())
}

How It Works

• Pass is_peek=true to receive_queue_messages to read without consuming.
• Peeked messages remain in the queue and can be received again.
• Pass is_peek=false to consume and acknowledge the messages.
• Review timeouts, channel names, and client IDs before running against shared environments.
• Run the program while the server from the prerequisites is available.

Related

• Queues overview
• Rust SDK Reference
• Send & Receive