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 positions would mean churning through every historical event just to reach the live tail.

It works by setting start_position: KubeMQ::PubSub::EventStoreStartPosition::START_NEW_ONLY on the EventsStoreSubscription passed 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-last position when you need guaranteed replay; and reconnecting doesn't resume where you left off — a fresh START_NEW_ONLY subscription starts from "now" again, with no cursor persisted across restarts.

Prerequisites

• KubeMQ server running on localhost:50000
• Ruby SDK installed (gem install kubemq)

Code

require 'kubemq'

address = ENV.fetch('KUBEMQ_ADDRESS', 'localhost:50000')
channel = 'ruby-events-store.start-new-only'

begin
  client = KubeMQ::PubSubClient.new(address: address, client_id: 'es-new-only-example')
  puts "Connected to #{address}"

  cancel = KubeMQ::CancellationToken.new

  sub = KubeMQ::PubSub::EventsStoreSubscription.new(
    channel: channel,
    start_position: KubeMQ::PubSub::EventStoreStartPosition::START_NEW_ONLY
  )
  client.subscribe_to_events_store(sub, cancellation_token: cancel, on_error: lambda { |e|
    puts "Error: #{e.message}"
  }) do |event|
    puts "Received new event: #{event.metadata}"
  end
  puts 'Subscribed with START_NEW_ONLY — only future events will arrive'
  sleep 1

  3.times do |i|
    msg = KubeMQ::PubSub::EventStoreMessage.new(channel: channel, metadata: "new event #{i}", body: "data-#{i}")
    client.send_event_store(msg)
    puts "Sent event #{i}"
  end

  sleep 2
rescue KubeMQ::Error => e
  puts "KubeMQ error: #{e.message}"
ensure
  cancel&.cancel
  client&.close
  puts 'Done'
end

How It Works

• START_NEW_ONLY skips all historical events and only delivers events published after the subscription starts.
• This is the simplest start position — no historical replay, no sequence tracking.
• Review timeouts, channel names, and client IDs before running against shared environments.

Related

• Pattern overview
• Ruby SDK Reference
• Start from First
• Start from Last