Expiration Policy

Overview

An expiration policy puts a hard time limit on how long a queue message may sit unconsumed. It solves a different problem than a dead-letter policy — this isn't about messages that fail processing, it's about messages that go stale: a price quote, a one-time code, a cache-invalidation signal, where late delivery is actively wrong, not just delayed. Instead of every consumer re-checking timestamps itself, the deadline lives on the message and the broker enforces it.

At the API level, .expiration_seconds(30) attaches a per-message TTL when you build the message via QueueMessageBuilder, and the clock starts the moment the broker accepts it via send_queue_message, not when a consumer picks it up. Let the TTL elapse unconsumed and the broker silently removes it — a later poll just comes back empty, no error, no trace.

Gotchas: expiration is silent — no DLQ routing, no event, just a message that vanishes — so pair it with monitoring if you need visibility into how much work is being dropped. The timer starts at send time, not when a consumer picks up the work, so a message can expire mid-backlog even while a consumer is actively polling. And setting the TTL too short for your real consumer lag just turns ordinary slowness into silent data loss.

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 msg = QueueMessageBuilder::new()
        .channel("rust-queues.expiration-policy")
        .body(b"expires-soon".to_vec())
        .expiration_seconds(30)
        .build();

    let result = client.send_queue_message(msg).await?;
    println!(
        "Sent with expiration: id={}, expiration_at={}",
        result.message_id, result.expiration_at
    );

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

How It Works

• expiration_seconds(30) sets the message to expire after 30 seconds.
• Expired messages are automatically discarded by the server and not delivered.
• The expiration_at field in the result shows the Unix timestamp when the message expires.
• 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
• Delay Policy