kue-chain

kue-chain

Using Kue I discovered that most of the new jobs in my system are created on reaction to some other jobs finish. After implementing a little helper function it got a little better, but it still left a lot of repetetive parts in the code which managed the sequencing of jobs. So I went a little further to make what's happening on what more clear. This is what came out.

Installation

npm install kue-chain

Usage

First define your job types which inherit from Kue.Job:

var Job = require('kue').Job;
var util = require('util');

function TakeApart(thing) {
    Job.call(this, 'takeapart', {
        thing: thing
    });
}
util.inherits(TakeApart, Job);

function Repair(pieces, takeApartJobData) {
    Job.call(this, 'repair', {
        thing: takeApartJobData.thing,
        parts: pieces
    });
}
util.inherits(Repair, Job);

[...]

Start combining:

var kue = require('kue');
var jobs = kue.createQueue();
var when = require('kue-chain')(jobs, kue.Job);

when(TakeApart).then(Repair);
when(Repair).then(PutBackTogether);

Sometimes a little more control is needed:

/*
    ensure GoToStore and Buy are Kue Jobs...
 */
when(GoToStore).then(function (result, job.data, job, then) {
    checkTheShoppinglist(function (list) {
        // Buy each of the list items
        list.forEach(function (item) {
            then(new Buy(item));
        });
        // Always buy beer
        then(new Buy('beer'));
    });
});

And at other times you just need a shortcut to creat them:

var takeApartJob = new TakeApart('scooter');
takeApartJob.save();

Api

Module exports a function. The chainer:

chainer(Kue.Queue queue, Kue.Job KueJob) -> Function when(string|Function ParentJob)

This is needed for setup and setting up the job complete listener.

when(string|Function ParentJob) -> Object thenable

Function takes a parent job as well a string for the job type and returns a object with one property: then.

Object thenable.then(Job|Function job) -> void

Function takes a child Job, which, as well as ParentJob, has to inherit from the Kues Job prototype, or a function job(result, Object completedJobData, Job completedJob, Function then). then function here takes instance of a job and saves it.