Parallel Executor v1.2.0 Documentation

Table of contents

• Description
• Installation
• Usage example
• API
  • class ParallelExecutor

Description

This is a Node.js package for process parallelization. It is intended for taking advantage of multi-core CPU devices. For example if you want to run a routine on a collection of an array e.g.

const data = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11]
const results = []
const myRoutine = async (value: number) => {
  /* do some async job */
}

for (const dataItem of data) results.push(await myRoutine(dataItem))

This package will do this job quicker by:

• Splitting your data into balanced batches. The batch number will be determined by the number of cores the device CPU has. For example, if your CPU has 8 cores it will create 8 balanced batches and that will be:

  ;[[1, 9], [2, 10], [3, 11], [4], [5], [6], [7], [8]]

• Then it will create your device-CPU-core-number child processes, by forking your callback in a separate file and establishing an IPC communication channel with them
• Then one by one it will pass these balanced batches to each forked process and each child process will execute the same callback with its batch
• After each child process is done processing, each will return its result
• Finally, when all the results will be ready, the main process will gether all the results in chronological order

Installation

npm i parallel-executor

Usage example

import { ParallelExecutor } from 'parallel-executor'

// `myTask` will be executed in child process.
const myTask = async (data, params) => {
  const result = []
  const myRoutine = (_dataItem) => {
    return new Promise((resolve) =>
      setTimeout(() => resolve(_dataItem + 1), 1e3)
    )
  }

  for (const dataItem of data) result.push(await myRoutine(dataItem))

  return result
}
const options = {
  data: [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11],
  params: { dirname: __dirname },
  childProcess: {
    maxOldSpaceSize: 90
  }
}

;(async () => {
  const parallelExecutor = new ParallelExecutor()

  console.time('Parallel execution took')
  const result = await parallelExecutor.execute(myTask, options)
  console.timeEnd('Parallel execution took')
  // Parallel execution took: 2.043s

  console.log('result:', result)
  /**
   * result: [
   *   2, 3, 4,  5,  6,
   *   7, 8, 9, 10, 11,
   *   12
   * ]
   */
})()

// As opposed to parallel execution
;(async () => {
  console.time('Non parallel execution took')
  await myTask(options.data, { ...options.params, pid: 1 })
  console.timeEnd('Non parallel execution took')
  // Non parallel execution took: 11.015s
})()

API

class ParallelExecutor

• execute(callback: Callback, options: IOptions) (method):
  • params:
    • callback: (data: Data, params: IParams) => any | Promise;
      • Data:

        type Data = any[]

      • IParams:

        interface IParams {
          // Parameters passed within the options object.
          [key: string]: any
          // Child process id.
          pid: number
        }

    • options:

      interface IOptions {
        data: Data
        /**
         * Custom params. Consider that `pid` is preserved by the
         * package.
         */
        params: { [key: string]: any }
        childProcess?: {
          /*
           * You can configure the child process's `--max-old-space-size`
           * with this parameter.
           */
          maxOldSpaceSize?: number
        }
      }

  • The returned value is the merged results of the child processes. Type any[]