redux-background

About

redux-background allows you to create background tasks on redux. This package is very similar to redux-thunk or redux-promise but adds several features, like statistics, progress and rescheduling.

Installation

npm install redux-background --save

or if you use yarn

yarn add redux-background

Example

There is an example in this repo under the examples directory. To run in clone the repo. Go to the examples directory and run npm install; npm start

Setup

When creating the store, you need to add both the reducer, and a middleware provided by the package.

import { createStore, combineReducers, applyMiddleware } from 'redux';
import background from 'redux-background';
	
// Your app reducer
function appReducer(state = {}, action) {
  return state;
}
	
// Add the background reducer
const reducer = combineReducers({
  app: appReducer,
  background: background.reducer,
});
	
// Add the background middleware
// you can add any other middleware you want
const middleware = [
	background.middleware,		
];
	
export default createStore(reducer,applyMiddleware(...middleware)));

Basic Usage

Once everything is set up. You can execute a job by dispatching an addJob action creator.

import { startJob } from 'redux-background/actions'; 

...

function generateRandomNumber(job, dispatch, getState) {
	return 4; // Chosen by fair die roll
}

const options = {};
const action = startJob('randomNumber', generateRandomNumber, options);
dispatch(action)

...

Once its finished, assuming you mounted your reducer on background your state tree should look something like this

{
	background: {
		randomNumber: {
		    "times": 1, // The number of times this job has run
		    "active": true, // If the job is active
		    "running": false, // If the job is currently running
		    "startedOn": 1488855527616, // When it started
		    "finishedOn": 1488855526614, // When it finished
		    "lastRanOn": 1488855525107, // The last time it ran
		    "lastDuration": 1507, // How long did it take to run
		    "stoppedOn": 1488855529121, // When was it stopped
		    "value": 10, // The value of the latest run
		    "error": null, // An error if it existed
		    "progress": 100, // The progress of the job
		    "interval":null,
		    "maxTimes": null
		}
	}
}

Repeating Jobs

If you want to make the job automatically repeat after is done you can use the addJob action creator, and pass in some extra options

Option	Description	Default Value
interval	The frequency to call this job in ms. After it finishes it will wait interval ms before starting up again.	1000
maxTimes	How many times will this job be run before it automatically stops	1

So for a job that starts again 1s after if finishes you can use this action.

import { addJob } from 'redux-background/actions';

const action = addJob(name, fn, { interval: 1000, maxTimes: Infinity });

there is shorthand for this called addDaemon

import { addDaemon } from 'redux-background/actions';
const action = addDaemon(name, fn);

Passing Data to The Job

If you pass a data key to the job options, it will be available inside the first parameter for your job function

import { addJob } from 'redux-background/actions';

function createRandomNumber(job, dispatch, getState) {
  const { max, min } = job.data;
  return Math.round((Math.random() * (max - min)) + min);
}

const action = addJob(name, fn, { 
	interval: 1000, 
	maxTimes: Infinity,
	data: {
		min: 1,
		max: 6,
	}
});

Async Jobs

If your job is async, you have several options to choose from

1. Use promises if your job function returns a promise. The value of the job run will the promise value. Following our previous example

   function generateRandomNumber(job, dispatch, getState) {
   	return Promise.resolve(4); // Chosen by fair async die roll
   }

2. Use callbacks if your job recieves a fourth argument, it will be a callback you can use to report its error or value.

   function generateRandomNumber(job, dispatch, getState, cb) {
   	setTimeout(() => cb(null, 4), 0);
   }

3. Use async functions you can also use async functions

   async function generateRandomNumber(job, dispatch, getState, cb) {
   	const number = await Promise.resolve(4);
   	return number;
   }

   all jobs will wait until finished to be called again.

Error Handling

An error will be reported and added to the state if

1. Your job throws an error
2. It returns a rejected promise
3. You call the callback with a non null value as its first argument.

The latest error will be available in the state under the error property.

Reporting Progress

You can report on the progress of a job, by calling progress function inside the job parameter.

import Promise from 'bluebird';

async function createRandomNumber(job, dispatch, getState) {
  const { progress } = job;

  await Promise.delay(500);
  progress(25);

  await Promise.delay(500);
  progress(75);

  await Promise.delay(500);
  return 4;
}

The current progress will be available in the state under the progress property.

API

startJob

Registers a new job and automatically starts it, you can specify optional OPTIONS object with the following options

Option	Description	Default Value
interval	The frequency to call this job in ms. After it finishes it will wait interval ms before starting up again.	1000
maxTimes	How many times will this job be run before it automatically stops	1
data	An object to be passed to the job	{}

If the job previously existed it will replace it with this new function.

import { startJob } from 'redux-background/actions';
const OPTIONS = {
	interval: null,
	maxTimes: 1,
	data: {},
}
startJob(JOBNAME, JOBFN, OPTIONS);

startDaemon

shorthand for startJob with the options interval 1000 and maxTimes Infinity

stopJob

Stops a currently running job

import { stopJob } from 'redux-background/actions';
const action = stopJob(JOBNAME);

removeJob

Deregisters a job, and clears all its data from the state

import { removeJob } from 'redux-background/actions';
const action = removeJob(JOBNAME);