react-native-persistent-job

• Run parametized asynchronous functions (called jobs) that will re-run in cases of failure, connection loss, application crash or user forced shutdowns.
• Runs on both android and iOS.

Why?

When you develop an application you usually focus on the 'happy flow', where everything runs smoothly, the user has perfect connection, he only leaves the app through the exit button, the app never crashes and your backend or any of the services you use never fail.
Well... it is not usually like that.
Things will fail and might leave your application in an unstable state.
This repository aims to help deal with that.

Installation

Install package from npm

npm install --save react-native-persistent-job

Usage

There are 2 main apis. One for initialization, registering job types and applying modifiers (initializeStore) and one for running jobs (createJob).

initializeStore

initializeStore is used to set up options & run stored jobs. As soon as initializeStore is called the stored jobs that did not finish execution run.
To run any kind of persistent job you must call initializeStore first.

Arguments:

• storeName?: string - optional store name that identifies your instance when you call createJob
• jobHandlers: Array<{jobType: string, handleFunction: (...args: any) => Promise<void>}> - an array of job type (the key that identifies the job) and an handle function to run when the job type is called
• modifyJobStream?: Rx.Observable<JobNumbered> => RxObservable<JobNumbered> - Modifies the stream that runs the jobs (more on that later in the readme)
• modifyRetryStream?: Rx.Observable<JobNumbered> => RxObservable<JobNumbered> - Modifies the stream that retries the jobs (more on that later in the readme)
• concurrencyLimit?: number - Limit the number of jobs that can run concurrently, other jobs will have to wait until the running jobs finish before they can run.

createJob

createJob is used to run the jobs, it accepts the job type as an argument and returns the function of that job type wrapped with persistent-job functionality. For example if I want to run a function (a, b, c) => console.log(a, b, c) that has a jobType console I will run it like this: persistentJob.store().createJob('console')('valueForA', 'valueForB', 'valueForC')

Arguments:

• jobType: string - the job type for the job you want to run that you registered beforehand in initializeStore with the jobHandlers param
• ...args: any[] - the args that the function accepts

example for initializeStore and createJob

import persistentJob from 'react-native-persistent-job'

const logIt = (a, b, c) => console.log(a, b, c)

await persistentJob.initializeStore({
	jobHandlers: [{jobType: 'logIt', handleFunction: logIt}]
})

const persistentLogIt = persistentJob.store().createJob('logIt')
persistentLogIt('valueForA', 'valueForB', 'valueForC')
persistentLogIt('AnotherValueForA', 'AnotherValueForB', 'AnotherValueForC')

Job & Retry streams

The jobs run on a stream that can be modified using rx. There are some built-in modifiers which can be used to modify the stream.

runWhenOnline

Will only run the jobs once the device is connected to the internet.

• example

import persistentJob, {streamModifiers} from 'react-native-persistent-job'

const logIt = (a, b, c) => console.log(a, b, c)

await persistentJob.initializeStore({
	storeName: 'online-jobs',
	jobHandlers: [{jobType: 'logIt', handleFunction: logIt}]
	modifyJobStream: streamModifiers.runWhenOnline
})

const persistentLogIt = persistentJob.store('online-jobs').createJob('logIt')
persistentLogIt('valueForA', 'valueForB', 'valueForC')

withBackoff

Will run failed jobs with delay based on a backoff method (right now either exponential or fibonacci)

• Api:

streamModifiers.retryStream.withBackoff.{exponential / fibonacci}(initialWaitTime: number, maxWaitTime?: number)

• Example:

import persistentJob, {streamModifiers} from 'react-native-persistent-job' 

const failureOfAJob = (msg) => {
	console.log(msg)
	throw 'I failed'
}

const failingJobsStore = await persistentJob.initializeStore({
	storeName: 'failing-jobs',
	jobHandlers: [{jobType: 'failureOfAJob', handleFunction: failureOfAJob}]
	modifyRetryStream: streamModifiers.retryStream.withBackoff.exponential(10, 50)
})

const persistentFailureOfAJob = failingJobsStore.createJob('failureOfAJob') 
persistentFailureOfAJob('I will fail while running')

Stateful & stateless jobs

Usually you will want to use stateless jobs.
Sometimes however, it is more convenient for a job to have a state, then whenever it runs after a failure it will remember the last state it was at.
To do that your function will have to have a prefix with 2 arguments currentState and updateState.
Here is an example with both a stateless and a stateful job:

const statelessJob = async (name) => {
	for (let i = 0; i < 10; i++) {
		console.log('Hello name', i)
	}
}

const statefulJob = (currentState, updateState) => async (name) => {
	const start = currentState || 0
	for (let i = start; i < 10; i++) {
		console.log('Hello name', i)
		await updateState(i)
	}
}

await persistentJob.initializeStore({
	storeName: 'stateless-stateful',
	jobHandlers: [
		{jobType: 'stateless', handleFunction: statelessJob},
		{jobType: 'stateful', handleFunction: statefulJob, isStateful: true}
	]
})

const persistentStatelessJob = persistentJob.store('stateless-stateful').createJob('stateless')
const persistentStatefulJob = persistentJob.store('stateless-stateful').createJob('stateful')
persistentStatelessJob('john')
persistentStatefulJob('mary')