Dispo

Dispo is a job and cronjob scheduler for Node.

It uses Kue as its job queue and Redis to store job data. Definition of recurring jobs is done using crontab syntax, one-off jobs can be queued using ZeroMQ requests. nodemailer and nodemailer-sendmail-transport are being used to send emails.

All Jobs, regardless if running automatically or queued on demand for single runs, have to be defined in a configuration file. Jobs defined as cronjobs with a recurring interval are scheduled and run automatically.

Requirements

• Redis
• ZeroMQ

Installation

> npm install dispo

Usage

Dispo provides a binary to start from the command line.

> node_modules/.bin/dispo -h

Usage: dispo [options]

Options:

  -h, --help               output usage information
  -V, --version            output the version number
  -C, --config <config>    config file path, default: `jobs.json`
  -B, --basedir <basedir>  directory used as a base for relative config and job paths

The --config or -C option is required and points to the relative path of the configuration file. If no configuration path is given, the configuration is expected to be in jobs.json relative to the current working directory.

Job configuration

Jobs are defined in the jobs property of the configuration file. Each job, identified using a name, must point its file property to a JavaScript file exporting a function that is run when the job is executed.

The following configuration example defines a job called logRandomNumber that can be queued on-demand and a recurring job called databaseCleanup that is defined to run on 01:00 am every day using crontab syntax.

The attempts property on the database cleanup job defines that the job is only attempted to run once. When the property is not explicitely set, it defaults to 3 so a job is retried twice on failure. When a recurringly scheduled job/cronjob reaches fails on each of its attempts, it is not automatically rescheduled.

The recipients property will override the default set in mailer.js. You can also use it to disable sending an email for a job when it is enabled globally. You can set the global configuration in index.js.

{
  "jobs": {
    "logRandomNumber": {
      "file": "jobs/logRandomNumber.js"
    },
    "databaseCleanup": {
      "file": "jobs/databaseCleanup.js",
      "cron": "0 1 * * * *",
      "attempts": 1,
      "recipients": "[email protected]"
    }
  }
}

Send email on job failure

Dispo supports sending an email when a job fails after all available retries, using nodemailer to send the mails. To do so, simply enable the mailer in the configuration file and add email addresses that should be notified whenever a job fails to notifyOnError on a per job basis.

{
  "options": {
    "mailer": true
  },
  "jobs": [
    "mightFail": {
      "file": "jobs/mightFail.js",
      "cron": "*/1 * * * *",
      "attempts": 3,
      "notifyOnError": "[email protected]"
    }
  ]
}

By default, dispo will use nodemailer-sendmail-transport to send your emails, but you're free to add a different nodemailer transport such as smtp. You can also set mail options, such as from.

import nodemailer from 'nodemailer'

module.exports = {
  options: {
    mailer: {
      transport: nodemailer.createTransport('smtp://smtp.example.com')
      mail: {
        from: '[email protected]'
      }
    }
  },
  jobs: [
    mightFail: {
      file: 'jobs/mightFail.js',
      cron: '*/1 * * * *',
      attempts: 3,
      notifyOnError: '[email protected]'
    }
  ]
}

Attempts with delay and backoff for failing jobs

Jobs that sometimes fail to execute correctly (or any job in general to be precise) can be configured to restart with a delay after they fail. You can use this feature via the backoff property. Provide backoff.type = 'fixed' and the backoff.delay = <Number> in milliseconds to set a fixed delay in milliseconds that will be waited after a failed attempt to execute the job. Provide backoff.type = 'exponential' and the backoff.delay = <Number> in milliseconds to set a exponential growing delay in milliseconds that will be waited after a failed attempt to execute the job. The base of the expenential growth will be your given delay.

The following configuration example defines a job called flakyService that is defined to run every minute on every day. flakyService will be executed a second, third and fourth time when it fails (attempts: 4), but the second, third and fourth try will each wait 3 seconds before re-executing.

{
  "flakyService": {
    "file": "jobs/flakyService.js",
    "cron": "*/1 * * * *",
    "attempts": 4,
    "backoff": {
      "delay": 3000,
      "type": "fixed"
    }
  }
}

incremental

The following configuration example defines a job called flakyServiceWithLongRegenerationTime that is defined to run every minute on every day. flakyServiceWithLongRegenerationTime will be executed a second, third, fourth, fifth and sixth time when it fails (attempts: 4), but:

• the second try will wait 6 seconds,
• the third try will wait 9 seconds,
• the forth try will wait 12 seconds, before re-executing.

{
  "flakyServiceWithLongRegenerationTime": {
    "file": "jobs/flakyServiceWithLongRegenerationTime.js",
    "cron": "*/1 * * * *",
    "attempts": 4,
    "backoff": {
      "delay": 3000,
      "type": "incremental"
    }
  }
}

exponential

The following configuration example defines a job called anotherFlakyServiceWithLongRegenerationTime that is defined to run every minute on every day. anotherFlakyServiceWithLongRegenerationTime will be executed a second and third time when it fails (attempts: 4), but:

• the second try will wait 4 seconds (= 2000 * 2000 milliseconds),
• the third try will wait 16 seconds (= 4000 * 4000 milliseconds), before re-executing.

{
  "anotherFlakyServiceWithLongRegenerationTime": {
    "file": "jobs/anotherFlakyServiceWithLongRegenerationTime.js",
    "cron": "*/1 * * * *",
    "attempts": 3,
    "backoff": {
      "delay": 2000,
      "type": "exponential"
    }
  }
}