node-endeavour

Endeavour

Flexible, fault-tolerant operations for Typescript.

Requirements

• Node >=4.6.0
• Typescript >=2.0
• Experimental decorators
• ES6 target (for async/await support)

Installation

npm install node-endeavour --save

Example Usage

import endeavour from 'node-endeavour'

function unreliable () {
  if (Math.random <= 0.25) return Promise.resolve()
  return Promise.reject()
}

// create a fault tolerant operation. This will be retried
// 10 times, backing off exponentially with no maximum delay.
const faultTolerant = endeavour(unreliable)

async function main () {
  let result

  try {
    result = await faultTolerant()
  } catch (error) {
    console.log(error)
  }
}

main()

API

endeavour(thenableFunction, [options], [ctx])

Creates a new EndeavourRunnable; a wrapped version of your function that will retry indefinitely, or up until some specified limit. The default options are as follows:

• retries The maximum amount of times to retry the operation. Defaults to 10.
• constant The base in exponential backoff, or the slope in linear backoff. Defaults to 2.
• minTimeout The number of milliseconds before starting the first retry. Default is 1000.
• maxTimeout The maximum number of milliseconds between two retries. Default is Infinity.

You may also specify this (useful for wrapping instance methods).

class Thing {
  doSomethingUnreliable () {}
}

const instance = new Thing()

const faultTolerant = endeavour(instance.doSomethingUnreliable, instance)

faultTolerant()
  .then(res => { console.log('yay!') })
  .catch(e => { console.log(':(')) })

See the decorators section for a more terse way of handling these cases.

EndeavourRunnable([arguments], [intercept])

Using your wrapped function from endeavour(...) works much in the same way as before. Arguments are be passed like this:

myFaultTolerantOperation(['some', 'arguments'])

The wrapped operation also accepts and optional function to allow for greater control over how retries should proceed.

faultTolerantOperation((result, next) => {
  if (result.error instanceof MyCustomError) {
    return next(new Error('something went horribly wrong :('))
  }
})

Calling next() with an error will stop your operation. You can also pass in an new array of arguments for subsequent retries.

faultTolerantOperation((result, next) => {
  if (result.error instanceof MyCustomError) {
    return next(['new', 'args'])
  }
})

You could also just inspect the result of the last attempt.

faultTolerantOperation(result => {
  console.log(result.error)
})

Decorators

@endeavourable(EndeavourOpts)

A decorator for providing metadata about how retriable methods in a class should operate. Takes the options defined here.

@endeavourify([EndeavourOpts])

Provides the same functionality as endeavour, but for class methods.

@endeavourable({ retries: 15 })
class {
  // retried 15 times
  @endeavourify()
  unreliableMethod () {
    if (Math.random <= 0.25) return Promise.resolve()
    return Promise.reject()
  }

  // retried 5 times
  @endeavourify({ retries: 5 })
  doSomething () { }

  // retried 10 times
  @endeavourify()
  otherThing() { }
}

When no arguments are given to @endeavourable or @endeavourify, the defaults provided here will be used.

Want something for plain old JS? Check out node-retry.