cloudflare-domain-manager/apps/api/src/services/weighted-dns-scheduler.ts

import type { FastifyInstance } from "fastify";
import { AsyncTask, SimpleIntervalJob } from "toad-scheduler";
import * as serviceConfigService from "./service-config-service.js";
import { WEIGHTED_SLOT_MS } from "./routing/weighted.js";

export const WEIGHTED_DNS_JOB_ID = "weighted-dns";

export function createWeightedDnsTask(app: FastifyInstance): AsyncTask {
  return new AsyncTask(
    WEIGHTED_DNS_JOB_ID,
    async () => {
      const n = await serviceConfigService.reconcileWeightedDns(app.db, app.cf);
      if (n > 0) {
        app.log.info({ reconciled: n }, "weighted dns rotated");
      }
    },
    (err) => {
      app.log.warn({ err }, "weighted dns rotate failed");
    },
  );
}

export function scheduleWeightedDnsJob(
  app: FastifyInstance,
  task: AsyncTask,
): void {
  const scheduler = app.scheduler;
  if (!scheduler) return;
  if (scheduler.existsById(WEIGHTED_DNS_JOB_ID)) {
    scheduler.removeById(WEIGHTED_DNS_JOB_ID);
  }
  scheduler.addSimpleIntervalJob(
    new SimpleIntervalJob(
      { seconds: WEIGHTED_SLOT_MS / 1000, runImmediately: true },
      task,
      { id: WEIGHTED_DNS_JOB_ID, preventOverrun: true },
    ),
  );
}