import { forever, queue } from 'async' import * as Sequelize from 'sequelize' import { database as db } from '../../initializers/database' import { JOBS_FETCHING_INTERVAL, JOBS_FETCH_LIMIT_PER_CYCLE, JOB_STATES } from '../../initializers' import { logger } from '../../helpers' import { JobInstance } from '../../models' import { JobHandler, jobHandlers } from './handlers' type JobQueueCallback = (err: Error) => void class JobScheduler { private static instance: JobScheduler private constructor () { } static get Instance () { return this.instance || (this.instance = new this()) } activate () { const limit = JOBS_FETCH_LIMIT_PER_CYCLE logger.info('Jobs scheduler activated.') const jobsQueue = queue(this.processJob.bind(this)) // Finish processing jobs from a previous start const state = JOB_STATES.PROCESSING db.Job.listWithLimit(limit, state) .then(jobs => { this.enqueueJobs(jobsQueue, jobs) forever( next => { if (jobsQueue.length() !== 0) { // Finish processing the queue first return setTimeout(next, JOBS_FETCHING_INTERVAL) } const state = JOB_STATES.PENDING db.Job.listWithLimit(limit, state) .then(jobs => { this.enqueueJobs(jobsQueue, jobs) // Optimization: we could use "drain" from queue object return setTimeout(next, JOBS_FETCHING_INTERVAL) }) .catch(err => logger.error('Cannot list pending jobs.', err)) }, err => logger.error('Error in job scheduler queue.', err) ) }) .catch(err => logger.error('Cannot list pending jobs.', err)) } createJob (transaction: Sequelize.Transaction, handlerName: string, handlerInputData: object) { const createQuery = { state: JOB_STATES.PENDING, handlerName, handlerInputData } const options = { transaction } return db.Job.create(createQuery, options) } private enqueueJobs (jobsQueue: AsyncQueue, jobs: JobInstance[]) { jobs.forEach(job => jobsQueue.push(job)) } private processJob (job: JobInstance, callback: (err: Error) => void) { const jobHandler = jobHandlers[job.handlerName] if (jobHandler === undefined) { logger.error('Unknown job handler for job %s.', job.handlerName) return callback(null) } logger.info('Processing job %d with handler %s.', job.id, job.handlerName) job.state = JOB_STATES.PROCESSING return job.save() .then(() => { return jobHandler.process(job.handlerInputData) }) .then( result => { return this.onJobSuccess(jobHandler, job, result) }, err => { logger.error('Error in job handler %s.', job.handlerName, err) return this.onJobError(jobHandler, job, err) } ) .then(() => callback(null)) .catch(err => { this.cannotSaveJobError(err) return callback(err) }) } private onJobError (jobHandler: JobHandler, job: JobInstance, err: Error) { job.state = JOB_STATES.ERROR return job.save() .then(() => jobHandler.onError(err, job.id)) .catch(err => this.cannotSaveJobError(err)) } private onJobSuccess (jobHandler: JobHandler, job: JobInstance, jobResult: any) { job.state = JOB_STATES.SUCCESS return job.save() .then(() => jobHandler.onSuccess(job.id, jobResult)) .catch(err => this.cannotSaveJobError(err)) } private cannotSaveJobError (err: Error) { logger.error('Cannot save new job state.', err) } } // --------------------------------------------------------------------------- export { JobScheduler }