batch-retry

Helps you to retry a batch of tasks.

Feature

• Only retry failed tasks.
• Retry results can be cached and eventually all returned if you want.
• You can customize the maximum number of retries.
• You can customize whether the result should be retried.

Install

npm install --save batch-retry

yarn add batch-retry

Usage

Using BatchRetry class

It provide a class called BatchRetry which should be contructed with a executor.

The executor is a function that takes an array of size n as input, and returns another array of size n as output.

A BatchRetry instance has a run method, which will pass param to executor and manage the retry process.

When the executor itself throws, the run method will throws too, so executor must catch all tasks' error and return something for checking retry. You can simplily return the error, BatchRetry will check the result, if it is an error(by default, I will discuss this later), it would be recorded and wait for batch retry.

const {BatchRetry} = require('batch-retry')

const evenError = new Error('Even')
const simpleExecutor = numbers => Promise.all(numbers
  .map(each =>
    (each % 2 === 0)
      ? Promise.reject(evenError).catch(e => e) // have to catch by hand or it will throw
      : Promise.resolve(each)
  )
)

// Initialize a instance.
const batchRetry = new BatchRetry({
      maxRetries: 5,
      onlyFinalResult: false, // return all the result
      executor: simpleExecutor
    })
const input = [1, 2, 3]

// Run the process
batchRetry.run(input).then(console.log)
// will output all the result [[1],[evenError, evenError, evenError, evenError, evenError],[3]]
// if onlyFinalResult set to true, it will only output [1, evenError, 3]

Using buildWithBatchRetry function

It provide a helper function buildWithBatchRetry, to compose high order functions.

const {buildWithBatchRetry} = require('batch-retry')

const evenError = new Error('Even')
const simpleExecutor = numbers => Promise.all(numbers
  .map(each =>
    (each % 2 === 0)
      ? Promise.reject(evenError).catch(e => e) // have to catch by hand or it will throw
      : Promise.resolve(each)
  )
)

// case 1: use it as a wrapper function
{
  const withBatchRerty = buildWithBatchRetry({
        maxRetries: 5,
        onlyFinalResult: false // return all the result
      })
  // wrap the executor
  const simpleExecutorWithBatchRetry = withBatchRerty(simpleExecutor)
  // Run the process
  simpleExecutorWithBatchRetry([1, 2, 3]).then(console.log)
  // will output all the result [[1],[evenError, evenError, evenError, evenError, evenError],[3]]
  // if onlyFinalResult set to true, it will only output [1, evenError, 3]
}

// case 2: use it directly
{
  const simpleExecutorWithBatchRetry = buildWithBatchRetry({
        maxRetries: 5,
        onlyFinalResult: false, // return all the result
        executor: simpleExecutor
      })
  // Run the process
  simpleExecutorWithBatchRetry([1, 2, 3]).then(console.log)
}

API

BatchRetry

constructor(options) => batchRetry: BatchRetry

• options.shouldRetry: Function for checking retry. Default: Check if the value is of type error or error-like(has properties stack and message) or executed times is greater than or euqal to maxRetries.
  • Function: (task, result, executedTimes) = > Boolean
• options.maxRetries: Max retry times. Default: 3
  • Number
• options.onlyFinalResult: Representing if it should only returns the final result. If setting to false, it will returns all results instead. For example, having final result: [1, error, 3] and all results: [[1], [error, error, error, error, error], [3]], it means only the second task failed, and after five retries, it still failed. Default: true
  • Boolean
• options.executor: Executor function. It takes an array of size n as input, and returns another array of the same size as output. Required
  • Function: tasks: Array => result: Array