Keep a room online · Ball2D Docs

A room closes when its host loses the service connection, its key is revoked or expires, or you close it. This host runs forever: whenever its room ends, it opens a new one, backing off when the service asks it to.

host.mjs

import { createRoom, RoomAdmissionError } from 'ball2d/node';

const config = {
  apiKey: process.env.BALL2D_API_KEY,
  roomName: 'Always-on football',
  noPlayer: true,
  public: true,
};

const stopping = new AbortController();
for (const signal of ['SIGINT', 'SIGTERM'])
  process.once(signal, () => stopping.abort());

const sleep = (seconds) =>
  new Promise((resolve) => {
    const timer = setTimeout(resolve, seconds * 1000);
    stopping.signal.addEventListener(
      'abort',
      () => (clearTimeout(timer), resolve()),
      { once: true },
    );
  });

function setUp(room) {
  room.onError = (message) =>
    console.error(`[${room.roomId}]`, message);
  room.onPlayerJoin = (player) =>
    room.setPlayerTeam(player.id, 1);
  return room.setDefaultStadium('Classic');
}

let failures = 0;
while (!stopping.signal.aborted) {
  let room;
  try {
    room = await createRoom(config, {
      signal: stopping.signal,
    });
  } catch (error) {
    if (stopping.signal.aborted) break;
    // Bad configuration.
    if (error instanceof TypeError) throw error;
    if (
      error instanceof RoomAdmissionError &&
      [400, 401, 403].includes(error.status)
    )
      throw error;
    failures++;
    const wait =
      error.retryAfterSeconds ??
      Math.min(300, 2 ** failures) + Math.random() * 3;
    console.warn(
      `Room did not open: ${error.message}.` +
        ` Retrying in ${Math.round(wait)} s.`,
    );
    await sleep(wait);
    continue;
  }

  failures = 0;
  console.log('Room open:', room.roomLink);
  await setUp(room).catch((error) =>
    console.error('Setup failed:', error),
  );

  // Wait until the room ends or we are asked to stop.
  await new Promise((resolve) => {
    room.signal.addEventListener('abort', resolve, {
      once: true,
    });
    stopping.signal.addEventListener('abort', resolve, {
      once: true,
    });
  });
  room.close();
  await room.closed;
  if (!stopping.signal.aborted) await sleep(5);
}

How it works

Stop on permanent errors. Invalid settings and invalid, expired or revoked keys won't fix themselves, so the host exits and your process manager or alerting takes over.
Back off on the rest. Limits (429) wait the retryAfterSeconds the service sends. Other failures wait exponentially longer, up to five minutes, with jitter so many hosts don't retry together.
Wait on the room's own signal. room.signal aborts however the room ends, so one await covers a lost connection, a revocation and an expiry.
Pause before reopening. A short delay avoids spending your per-minute request budget in a loop if rooms keep closing.
Shut down cleanly. SIGTERM closes the room, waits for room.closed and ends the loop.

Players in a closed room are not moved to the new one; the new room has a new link. Publish a stable link on your own site that points at the current room.roomLink, or list the room publicly so players find it in the room list.