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import { forever, queue } from 'async'
const db = require('../../initializers/database')
import {
JOBS_FETCHING_INTERVAL,
JOBS_FETCH_LIMIT_PER_CYCLE,
JOB_STATES
} from '../../initializers'
import { logger } from '../../helpers'
import { jobHandlers } from './handlers'
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)
// Finish processing jobs from a previous start
const state = JOB_STATES.PROCESSING
db.Job.listWithLimit(limit, state, (err, jobs) => {
this.enqueueJobs(err, 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, (err, jobs) => {
if (err) {
logger.error('Cannot list pending jobs.', { error: err })
} else {
jobs.forEach(job => {
jobsQueue.push(job)
})
}
// Optimization: we could use "drain" from queue object
return setTimeout(next, JOBS_FETCHING_INTERVAL)
})
},
err => { logger.error('Error in job scheduler queue.', { error: err }) }
)
})
}
createJob (transaction, handlerName, handlerInputData, callback) {
const createQuery = {
state: JOB_STATES.PENDING,
handlerName,
handlerInputData
}
const options = { transaction }
db.Job.create(createQuery, options).asCallback(callback)
}
private enqueueJobs (err, jobsQueue, jobs) {
if (err) {
logger.error('Cannot list pending jobs.', { error: err })
} else {
jobs.forEach(job => {
jobsQueue.push(job)
})
}
}
private processJob (job, callback) {
const jobHandler = jobHandlers[job.handlerName]
logger.info('Processing job %d with handler %s.', job.id, job.handlerName)
job.state = JOB_STATES.PROCESSING
job.save().asCallback(err => {
if (err) return this.cannotSaveJobError(err, callback)
if (jobHandler === undefined) {
logger.error('Unknown job handler for job %s.', jobHandler.handlerName)
return callback()
}
return jobHandler.process(job.handlerInputData, (err, result) => {
if (err) {
logger.error('Error in job handler %s.', job.handlerName, { error: err })
return this.onJobError(jobHandler, job, result, callback)
}
return this.onJobSuccess(jobHandler, job, result, callback)
})
})
}
private onJobError (jobHandler, job, jobResult, callback) {
job.state = JOB_STATES.ERROR
job.save().asCallback(err => {
if (err) return this.cannotSaveJobError(err, callback)
return jobHandler.onError(err, job.id, jobResult, callback)
})
}
private onJobSuccess (jobHandler, job, jobResult, callback) {
job.state = JOB_STATES.SUCCESS
job.save().asCallback(err => {
if (err) return this.cannotSaveJobError(err, callback)
return jobHandler.onSuccess(err, job.id, jobResult, callback)
})
}
private cannotSaveJobError (err, callback) {
logger.error('Cannot save new job state.', { error: err })
return callback(err)
}
}
// ---------------------------------------------------------------------------
export {
JobScheduler
}
|
