Get socket ids from a room without .in(room).fetchSockets() in a multicluster environment

[Bubuioc]

I’m wondering if there’s a way to retrieve only the socket IDs from a room in a multi-cluster setup, without using .in(room).fetchSockets().
The issue is that I need to perform this operation very frequently, and fetchSockets() returns the full remote socket instances, whereas I only need the socket IDs.
For context, I’m using the Redis Streams adapter.
Thanks!

[darrachequesne]

For future readers, you can use the serverSideEmit() method:

function getLocalSocketIds(room) {
  const ids = io.of("/").adapter.rooms.get(room);
  return ids ? [...ids] : [];
}

io.on("retrieve socket ids", (room, cb) => {
  cb(getLocalSocketIds(room));
});

async function getAllSocketIds(room) {
  const ids = getLocalSocketIds(room);

  const responses = await io.serverSideEmitWithAck("retrieve socket ids", room);
  
  responses.forEach((response) => {
    ids.push(...response);
  });
  
  return ids;
}

See also: https://socket.io/how-to/count-connected-clients