Start New Only

Overview

Start-from-new turns a durable Events Store channel into a live-only feed — reach for it when a consumer only cares what happens from this moment forward and would rather skip a large backlog than pay to replay it. Dashboards, live notification fan-outs, and freshly-deployed services that don't need to catch up on history are the classic cases: any of the replay-from-start variants would mean churning through every historical event just to reach the live tail.

It works by passing EventsStoreSubscription::StartNewOnly to subscribe_to_events_store — the broker stamps the subscription's registration time as a watermark and delivers only events published after it, ignoring everything already stored. Gotchas: there's a race between registering and the publisher sending — a publish that lands before the broker fully registers you is silently skipped, so give the subscription a moment to settle before publishing; this position can never see anything published earlier, so use a start-from-first or start-from-sequence variant when you need guaranteed replay; and reconnecting doesn't resume where you left off — a fresh StartNewOnly subscription starts from "now" again, with no cursor persisted across restarts.

Prerequisites

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

Code

use kubemq::prelude::*;
use kubemq::EventsStoreSubscription;
use std::time::Duration;

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

    let sub = client.subscribe_to_events_store(
        "rust-events-store.start-new-only", "",
        EventsStoreSubscription::StartNewOnly,
        |event| Box::pin(async move {
            println!("New event: seq={}, body={}", event.sequence, String::from_utf8_lossy(&event.body));
        }),
        None,
    ).await?;

    tokio::time::sleep(Duration::from_secs(10)).await;
    sub.unsubscribe().await;
    client.close().await?;
    Ok(())
}

How It Works

• StartNewOnly skips all historical events and only delivers events published after subscribing.
• This is the lightest start mode — no replay overhead.
• 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
• Start from First