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import cron from 'cron';
import Bluebird from 'bluebird';
import { EventModel, Event } from './event.model';
export type Handler = (event: Event<any>) => void;
const CronJob = cron.CronJob;
const defaultPollingInterval = '*/10 * * * * *';
class Scheduler {
private jobs: cron.CronJob[];
private pollingJob: cron.CronJob;
private handlers: Record<string, Handler>;
public Model: EventModel<any>;
constructor(model: EventModel<any>, pollingInterval = defaultPollingInterval) {
this.Model = model;
this.jobs = [];
this.handlers = {};
this.pollingJob = new CronJob(pollingInterval, () => this.updateJobs());
this.startPolling();
}
public registerHandler(name: string, handler: Handler) {
this.handlers[name] = handler;
}
public startPolling() {
this.pollingJob.start();
}
public stopPolling() {
this.pollingJob.stop();
}
private startAllJobs() {
this.jobs.forEach(job => job.start());
}
private stopAllJobs() {
this.jobs.forEach(job => job.stop());
}
private async rescheduleMissedEvents() {
const missedEvents = await this.Model.findMissedEvents();
return Bluebird.map(missedEvents, event => event.save());
}
private async updateJobs() {
// Reschedule missed events before we stop jobs to avoid
// accidentally stopping the job that has not triggered yet
// (if event schedule resonates with updateJobs schedule)
await this.rescheduleMissedEvents();
this.stopAllJobs();
const events = await this.Model.findNextEvents();
if (!events.length) console.log('WARNING: no upcoming events');
this.jobs = events.map(event => new CronJob(
event.schedule,
() => this.run(event.id)
));
this.startAllJobs();
}
private async run(id: string) {
const event = await this.Model.findById(id);
if (!event) return console.log('WARNING: locked event does not exist');
try {
const handleEvent = this.handlers[event.type];
if (handleEvent) {
event.start();
await handleEvent(event);
return event.complete();
} else throw new Error('No handler found')
} catch (error) {
return event.fail(error);
}
}
}
export default Scheduler;
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