How to properly terminate H3 EventHandler when using Server-Sent Events?

[vicentematus]

I'm working with Server-Sent Events (SSE) in Nitro (behind it's h3). I've encountered an issue where the server continues processing the event handler even after the client disconnects and the onClosed callback is triggered.

When a client disconnects from the SSE connection, the onClosed callback triggers as expected. However, the issue is that the EventHandler continues executing. This means that even though we've closed the client connection, our server is still processing data.

See my following code:

export default defineEventHandler(async (event: H3Event) => {
  const eventStream = createEventStream(event);
  
  eventStream.onClosed(async () => {
    console.log("closing eventstream");
    await eventStream.close();
    // ❓ How to terminate the event handler so it doesn't process anymore?
  });

  // Initialize server-sent events 
  eventStream.send();
  
  // Some async operations...
  const users = await getUsers();
  
  // Here I send the data progressively to the client
   eventStream.push({
    event: "users",
    data: JSON.stringify(users)
  });
  
  // ➡️ Assume that the client disconnect here via `close`

  // ❌ Even if client is disconnected, this code still executes
  const bills = await getBills();
  
  // ❌ Even if client is disconnected, this code still executes
  await someMoreAsyncOperations();
  

 //...
  
});

What's the recommended approach to terminate the entire EventHandler execution when a client disconnects? Or I'm approaching server-side events the correct way?

Im using
node v20.15.1
nitropack: 2.9.7([email protected])
[email protected]
Thank you.