main.ts

import { checkPendingCrons } from "./src/cron";
import { Cron, close, watchUpdateEvent } from "./src/database";
import { log } from "./src/log";
import { drain } from "./src/nats";

function wait(ms: number) {
  return new Promise((resolve) => setTimeout(resolve, ms));
}

log("Starting cron service");

process.on("SIGINT", () => teardown());
process.on("SIGTERM", () => teardown());

async function teardown() {
  log("Shutting down cron service");

  await close();
  await drain();

  process.exit(0);
}

while (true) {
  await checkPendingCrons();

  const now = Date.now();
  const next = await Cron.findNext();

  const nextRun = next?.nextRun?.getTime();
  if (!nextRun) {
    log("No pending cron jobs, waiting for update event");
    await watchUpdateEvent();
    continue;
  }

  const delay = nextRun - now;

  log("Next check in", delay, "ms");

  const waitUpdate = watchUpdateEvent();

  await Promise.race([wait(delay), waitUpdate]);

  waitUpdate.abort();
}