Atomic and resumable tasks implementation with observable status tracking. Provides two task types: AtomicTask for one-shot operations and ResumableTask for pausable/resumable operations.

Install

• npm

  npm install --save @guanghechen/task

• yarn

  yarn add @guanghechen/task

Usage

AtomicTask

For tasks that run to completion without pause/resume support:

import { AtomicTask, TaskStatusEnum, TaskStrategyEnum } from '@guanghechen/task'
import { Subscriber } from '@guanghechen/subscriber'

class DownloadTask extends AtomicTask {
  private readonly url: string

  constructor(url: string) {
    super('download-task', TaskStrategyEnum.ABORT_ON_ERROR)
    this.url = url
  }

  protected async run(): Promise<void> {
    // Perform the download operation
    console.log(`Downloading from ${this.url}`)
    await fetch(this.url)
    console.log('Download complete')
  }
}

const task = new DownloadTask('https://example.com/file')

// Subscribe to status changes
const subscriber = new Subscriber({
  onNext: (status) => {
    console.log('Status:', TaskStatusEnum[status])
  }
})
task.status.subscribe(subscriber)

// Start the task
await task.start()

// Or run to completion
await task.complete()

// Check for errors
if (task.errors.length > 0) {
  console.error('Task failed:', task.errors)
}

ResumableTask

For tasks that can be paused and resumed:

import { ResumableTask, TaskStatusEnum, TaskStrategyEnum } from '@guanghechen/task'

class BatchProcessTask extends ResumableTask {
  private readonly items: string[]

  constructor(items: string[]) {
    super('batch-process', TaskStrategyEnum.CONTINUE_ON_ERROR, 100) // 100ms poll interval
    this.items = items
  }

  protected *run(): IterableIterator<Promise<void>> {
    for (const item of this.items) {
      yield this.processItem(item)
    }
  }

  private async processItem(item: string): Promise<void> {
    console.log(`Processing: ${item}`)
    await new Promise(resolve => setTimeout(resolve, 500))
  }
}

const task = new BatchProcessTask(['item1', 'item2', 'item3'])

// Start the task
await task.start()

// Pause after some time
setTimeout(async () => {
  await task.pause()
  console.log('Task paused')

  // Resume later
  setTimeout(async () => {
    await task.resume()
    console.log('Task resumed')
  }, 2000)
}, 1000)

Task Status

Tasks have observable status with the following states:

| Status | Description | | :------------------: | :----------------------------------: | | PENDING | Task not started | | RUNNING | Task is running | | SUSPENDED | Task is paused (ResumableTask only) | | CANCELLED | Task was cancelled | | FAILED | Task failed with errors | | COMPLETED | Task completed successfully | | ATTEMPT_SUSPENDING | Attempting to pause | | ATTEMPT_RESUMING | Attempting to resume | | ATTEMPT_CANCELING | Attempting to cancel | | ATTEMPT_COMPLETING | Attempting to complete |

Task Strategy

| Strategy | Description | | :-----------------: | :--------------------------------------------: | | ABORT_ON_ERROR | Stop task execution when an error occurs | | CONTINUE_ON_ERROR | Continue execution despite errors |

Reference

• homepage