Cancel Subscription

Overview

Every events store subscription opens a long-lived stream to the broker — an async task that keeps pulling delivered events until you tell it to stop. Calling sub.unsubscribe().await is how you release that task deliberately: shutting down a worker, rotating consumers, or tearing down a process without leaking connections or leaving a dangling stream on the server.

Internally, unsubscribe() cancels the subscription via a CancellationToken, which unwinds the receive loop and detaches from the broker-side subscription registration.

Gotchas: cancelling only stops this subscriber — the channel keeps storing every event published afterward, so nothing is lost, and a fresh subscription with StartFromFirst or a specific sequence picks up exactly where this one left off. unsubscribe().await completing doesn't guarantee every in-flight callback has finished; treat it as "no new events will start," not an instantaneous hard stop.

Prerequisites

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

Code

use kubemq::prelude::*;
use kubemq::{EventStoreBuilder, EventsStoreSubscription};
use std::time::Duration;

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

    let channel = "rust-events-store.cancel-subscription";

    let sub = client
        .subscribe_to_events_store(
            channel,
            "",
            EventsStoreSubscription::StartNewOnly,
            |event| {
                Box::pin(async move {
                    println!("Received: seq={}", event.sequence);
                })
            },
            None,
        )
        .await?;

    tokio::time::sleep(Duration::from_millis(500)).await;

    let event = EventStoreBuilder::new()
        .channel(channel)
        .body(b"before-cancel".to_vec())
        .build();
    client.send_event_store(event).await?;

    tokio::time::sleep(Duration::from_secs(1)).await;

    sub.unsubscribe().await;
    println!("Subscription cancelled");

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

How It Works

• sub.unsubscribe().await cancels the subscription via CancellationToken.
• Events published after cancellation are stored but not delivered to the cancelled subscriber.
• Review timeouts, channel names, and client IDs before running against shared environments.
• Run the program while the server from the prerequisites is available.

Related

• Events Store overview
• Rust SDK Reference
• Persistent Pub/Sub