Assure bull only runs a single instance of a job

bull.js

global.Promise = require('bluebird')

const Queue = require('bull')
const EventEmitter = require('events')

const JOB_NAME = 'testJob'
const PROGRESS_BUS_EVENT_NAME = 'progress'
const COMPLETED_PROGRESS_VALUE = 100

const { log } = console
const q = new Queue('testing')
const progressBus = new EventEmitter()

q.process(JOB_NAME, job => new Promise((resolve, reject) => {
  log('Processing job %s; Counter: %d', job.id, job.data.count)

  progressBus.on(PROGRESS_BUS_EVENT_NAME, (data) => {
    if (job.id === data.job.id && data.progress === COMPLETED_PROGRESS_VALUE) {
      Promise
        .resolve()
        .then(() => {
          // do async job cleanup here (optionally)
        })
        .then(() => resolve({ status: 'superseded' }))
    }
  })

  setTimeout(() => {
    resolve({ status: 'completed' })
  }, 5000)
}))

q.on('progress', (job, progress) => {
  log('Job %s progress changed to %d.', job.id, progress)
  progressBus.emit(PROGRESS_BUS_EVENT_NAME, { job, progress })
})

q.on('completed', (job, res) => {
  log('Job %s had completed with status `%s`.', job.id, res.status)
})

q.add(JOB_NAME, { count: 1 })

setTimeout(() => {
  q
    .getActive()
    .map((job) => {
      if (job.name === JOB_NAME) {
        job.progress(COMPLETED_PROGRESS_VALUE)
      }

      return job
    })
    .then(() => q.add(JOB_NAME, { count: 2 }))
}, 1000)