Outbound state-update pushes for channels: drop no-op updates, and optionally coalesce bursts into one message.

State events re-send the current state of an object the subscriber already has, so two things are worth doing before pushing:

• Deduplicate. If nothing changed since the last push on this connection, send nothing at all.
• Debounce. When REALTIME_DEBOUNCE_MS is set, hold updates for that long and push only the latest state per object when the timer fires. A burst of ten writes to one lobby becomes one message.

Debouncing is off by default (0), which pushes immediately and only deduplicates.

Coalescing beats shrinking here: each WebSocket message costs roughly 76 bytes of framing, TLS, TCP and IP headers before any payload, and the server runs with TCP_NODELAY, so every message is its own packet. Removing a message saves more than compressing one ever can.

Usage

def handle_info({:lobby_updated, lobby}, socket) do
  payload = Serializers.serialize_lobby(lobby)
  {:noreply, ChannelUpdates.push(socket, "lobby_updated", payload.id, payload)}
end

# required once per channel that pushes updates
def handle_info({:channel_updates_flush, _}, socket),
  do: {:noreply, ChannelUpdates.flush(socket)}

key scopes the dedupe/coalesce slot within the channel. Channels that track one object can pass any constant; channels that multiplex (lobbies, groups, member lists) must pass the object id.