level-schedule

Durable job scheduler based on LevelDB

npm install level-schedule
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level-schedule

Durable job scheduler based on LevelDB. If the process is restarted it will transparently resume where it stopped.

Build Status

Usage

Print some JSON after 5s, even if the process restarts.

var levelup = require('levelup');
var Schedule = require('level-schedule');

var db = levelup('./db');

Schedule(db)
  .job('print', function (payload) {
    console.log(payload);
  })
  .run('print', { some : 'json' }, Date.now() + 5000);

// => { some : 'json' }

Periodic tasks

Run a task every 100ms. Always call this.run at the end of the task, otherwise if the process crashes while running your task it will be scheduled once too many.

Schedule(db)
  .job('periodic', function () {
    console.log('doing some stuff...');
    this.run('periodic', Date.now() + 100)
  })
  .run('periodic', Date.now() + 100);

Jobs

A job can be synchronous or asynchronous, just use the done argument when defining an asynchronous job.

Schedule(db)
  .job('sync', function (payload) {
    if (somethingBadHappend) {
      throw new Error();
    }
  })
  .job('async', function (payload, done) {
    // notice the 2nd argument
    doSomething(function (err) {
      done(err);
    });
  })
  .on('error', console.error)
  .run('sync')
  .run('async');

API

Schedule(db)

Setup level-schedule to use db.

Schedule#job(name, fn)

Register a job with name and fn.

fn is called with 2 arguments:

  • payload : The payload
  • done : If the job performs async operations, call done() when done. If an error occured you can pass that as an error argument to done.

Schedule#run(job[, payload], timestamp)

Run job with payload at timestamp.

Schedule#on('error', fn)

Call fn whenever an Error occurs. When no error listener has been registered, errors will be thrown.

Installation

With npm do

$ npm install level-schedule

License

(MIT)

Copyright (c) 2013 Julian Gruber <julian@juliangruber.com>

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

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