cronos

A module for handling cron jobs

npm install cronos
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Cronos

A NodeJS module for handling cron jobs. It's a wrapper around node-schedule and it enhances its features by allowing to automatically keep track of the status of a job and adding a more efficient errors handling mechanic.

Status

Alpha as f*ck

Installation

Just clone this repo and launch npm install -d

Features

  • All the features of node-schedule are present
  • Easy to track the jobs that are running (see the how to)
  • In case of failure recover all the running job with the load() function
  • Error handling based on events

General Instructions

The main component of this module is the Scheduler, that allows to create and schedule job. A job is created by passing a JSON object

job = {
   name:'myJob',
   work:'fileName',
   period:'cronExpression'
}

work is a JavaScript file containing the function that will be executed by the job. It must conform the following structure:

var execute = function(){
  //body of the function
};
exports.execute = execute;

period is a cron expression defining when the job must be executed ( actually you can specify the period in all the way supported by node-schedule )

Both the Scheduler and the job objects are event emitter.

The Scheduler emits the following event:

  • scheduled: A particular job is scheduled
  • run: A particular job has been executed (triggered AFTER the execution of the function)
  • stop: A particular job has been stopped

The job emits the following event:

  • error: An error is occurred during the execution of the job function

How-to

Hello World

First require the module:

var Scheduler = require('path_to_the_module/scheduler.js'); //to be change as I publish the module on npm

Then to create a job:

var scheduler = new Scheduler('path_to_the_script_folder');
var job = {name:'myJob', work:'work', period:'* * * * *'};
scheduler.createJobAndSchedule(job,function(cronJob){
  //..do some other stuff
});

Given that work is this JavaScript file:

var execute = function(){
  console.log('Hello World!')
};
exports = exports.execute;

Scheduler

This object contains all the method for handling jobs

  • createJob(job,callback): create a job but don't schedule it
  • createJobAndSchduler(job,callback): create a job and schedule it for execution
  • reSchedule(cronJob): re-schedule a job
  • stopJob(cronJob): stop a job
  • cancelJob(cronJob): terminate a job and cancel it from the database
  • terminateJob(cronJob): terminate a job but don't remove it from the database
  • load(): load all the not terminated jobs saved in the database and schedule them.

All the jobs are contained in the jobs array of the Scheduler object

Handling errors

To handle errors simply write a handler for the error event of the job

var scheduler = new Scheduler('path_to_the_script_folder');
var job = {name:'myJob', work:'work', period:'* * * * *'};
scheduler.createJobAndSchedule(job,function(cronJob){
  cronJob.on('error',functon(err){
     //handle the error
  });
});

NOTE: if you schedule the job through the load method you have to rewrite the error handler.

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