nicholaswmin/job-sequencer

Run strictly sequential jobs in Node.js whilst emitting W3C ProgressEvents

Job sequencer

Run long-running jobs, one at a time, whilst emitting W3C ProgressEvents

Basic Usage

Just inherit from JobSequencer

const JobSequencer = require('job-sequencer')

class LongRunningJobManager extends JobSequencer {
  constructor() {
    super()
  }

  async batchProcessFoo() {
    let batchJobFoo

    try {
      // Create a job with name 'batch-process-foo' that will tick
      // `job.progress()` 5 times
      batchJobFoo = this.createJob('batch-process-foo', 5);
      batchJobFoo.start()
      batchJobFoo.progress()
      batchJobFoo.progress()
      batchJobFoo.progress()
      batchJobFoo.progress()
      batchJobFoo.progress()
      batchJobFoo.success({ foo: 'bar' })  
    } catch (err) {
      job.error(err)
    }
  }
}

const batchProcessor = new LongRunningJobManager()

batchProcessor.on('status', status => {
  switch (status.type) {
    case 'loadstart':
      console.log('started')
      break;
    case 'progress':
      console.log(status.progress) // `{ total: 5, loaded: 2 }`.. etc
      break;
    case 'load':
      console.log(status.payload) // `{ foo: bar }`
      break;
    case 'error':
      console.log(status.payload) // logs any potential error
      break;
    default:
      // do nothing
  }
})

batchProcessor.batchProcessFoo()

Sequential Running

You can only run one job at a time. If any of the following events are called:

• job.success()
• job.error()
• job.abort()
• job.stop()

the Job is considered finished and it's ejected, thus allowing other Job's with the same name to run.

Attempting to run another Job with the same name if the aforementioned methods have not been called on Job will result in an Exception

Events Emitted

All events map to W3C Progress Events

Method	W3C ProgressEvent emitted
job.start()	loadstart
job.progress()	progress
job.error()	error
job.abort()	abort
job.success()	load
job.stop()	loadend

Tests

npm test

Job Sequencer
  ✓ it instantiates
  when a Job is created
    ✓ creates a Running Job
    ✓ returns a Running Job by name if it exists
    ✓ returns true if a Running Job exists by name
    ✓ returns a list of all the last statuses emitted by still running, Running Jobs
    ✓ clears the Running Job if the job has succeeded
    ✓ clears the Running Job if the job is errored
    ✓ clears the Running Job if the job is aborted
    ✓ clears the Running Job if the job is stopped
  when attempting to create a Job whilst another is running
    ✓ throws an exception
    ✓ creates the Job if the Job is done
    ✓ creates the Job if the Job is errored
    ✓ creates the Job if the Job is aborted
    ✓ creates the Job if the Job is stopped

Job Class
  ✓ instantiates in the correct state
  ✓ fires a loadstart event when start is called
  ✓ fires a progress event when progress is called
  ✓ fires an error event when error is called
  ✓ fires an abort event when abort is called
  ✓ fires a load event when success is called
  ✓ fires a loadend event when stop is called
  ✓ increments the loaded count by 1 when a progress event is emitted
  ✓ includes the job name when emitting an event
  ✓ includes any payload passed as arg. when emitting an event
  ✓ returns the last emitted status

License

Copyright 2017 Nicholas Kyriakides

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.