/bree

:traffic_light: Bree is the best job scheduler for Node.js with support for cron, dates, ms, later, and human-friendly strings. Uses workers and spawns sandboxed processes. Supports async/await, retries, throttling, concurrency, and cancelable jobs (graceful shutdown). Simple, fast, and the most lightweight tool for the job. Made for Forward Email and Lad.

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bree

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Bree is the best job scheduler for Node.js with support for cron, dates, ms, later, and human-friendly strings.
Uses workers to spawn sandboxed processes, and supports async/await, retries, throttling, concurrency, and cancelable jobs with graceful shutdown. Simple, fast, and the most lightweight tool for the job. Made for Forward Email and Lad.
❤️ Love this project? Support @niftylettuce's FOSS on Patreon or PayPal 🦄

Table of Contents

Foreword

Before creating Bree, I was a core maintainer (and financially invested in development) of Agenda. I have been with the Node.js community for a very, very long time, and have tried literally every solution out there (see Alternatives that are not production-ready). I have found that all existing solutions are subpar, as I have filed countless issues; discovered memory leaks, found functionality not working as described, unresolved core bugs have persisted over time, etc.

Previous to creating this, I was relying heavily on bull; having created @ladjs/bull – but due to core issues (and being Redis-backed) it was not the best tool for the job. Bull might have been okay if the core issues were fixed, however since it uses Redis it should not be used for a job queue. From my experience, Redis should only be used for caching and session storage purposes (e.g. CDN or managing user log in state in your application). As of the time of this writing, it has been months and the core bugs with Bull are still unresolved; as more people are continuing to reproduce and comment on the known issues.

Since workers are now readily available in LTS versions of Node, I thought it would be a great time to implement them in a job scheduler environment. Additionally, my research and development of a better anti-spam and anti-phishing classifier with Spam Scanner gave me some necessary insight to using workers.

Bree was created to give you fine-grained control with simplicity, and has built-in support for workers, sandboxed processes, graceful reloading, cron jobs, dates, human-friendly time representations, and much more. We recommend you to query a persistent database in your jobs, to prevent specific operations from running more than once. Bree does not force you to use an additional database layer of Redis or MongoDB to manage job state. In doing so, you should manage boolean job states yourself using queries. For instance, if you have to send a welcome email to users, only send a welcome email to users that do not have a Date value set yet for welcome_email_sent_at.

Install

npm:

npm install bree

yarn:

yarn add bree

Usage and Examples

The example below assumes that you have a directory jobs in the root of the directory from which you run this example. For example, if the example below is at /path/to/script.js, then /path/to/jobs/ must also exist as a directory. If you wish to disable this feature, then pass root: false as an option.

Inside this jobs directory are individual scripts which are run using Workers per optional timeouts, and additionally, an optional interval or cron expression. The example below contains comments, which help to clarify how this works.

The option jobs passed to a new instance of Bree (as shown below) is an Array. It contains values which can either be a String (name of a job in the jobs directory, which is run on boot) OR it can be an Object with name, path, timeout, and interval properties. If you do not supply a path, then the path is created using the root directory (defaults to jobs) in combination with the name. If you do not supply values for timeout and/nor interval, then these values are defaulted to 0 (which is the default for both, see index.js for more insight into configurable default options).

We have also documented all Instance Options and Job Options in this README below. Be sure to read those sections so you have a complete understanding of how Bree works.

const path = require('path');

// optional
const ms = require('ms');
const dayjs = require('dayjs');
const Graceful = require('@ladjs/graceful');
const Cabin = require('cabin');

// required
const Bree = require('bree');

//
// NOTE: see the "Instance Options" section below in this README
// for the complete list of options and their defaults
//
const bree = new Bree({
  //
  // NOTE: by default the `logger` is set to `console`
  // however we recommend you to use CabinJS as it
  // will automatically add application and worker metadata
  // to your log output, and also masks sensitive data for you
  // <https://cabinjs.com>
  //
  logger: new Cabin(),

  //
  // NOTE: instead of passing this Array as an option
  // you can create a `./jobs/index.js` file, exporting
  // this exact same array as `module.exports = [ ... ]`
  // doing so will allow you to keep your job configuration and the jobs
  // themselves all in the same folder and very organized
  //
  // See the "Job Options" section below in this README
  // for the complete list of job options and configurations
  //
  jobs: [
    // runs `./jobs/foo.js` on start
    'foo',

    // runs `./jobs/foo-bar.js` on start
    {
      name: 'foo-bar'
    },

    // runs `./jobs/some-other-path.js` on start
    {
      name: 'beep',
      path: path.join(__dirname, 'jobs', 'some-other-path')
    },

    // runs `./jobs/worker-1.js` on the last day of the month
    {
      name: 'worker-1',
      interval: 'on the last day of the month'
    },

    // runs `./jobs/worker-2.js` every other day
    {
      name: 'worker-2',
      interval: 'every 2 days'
    },

    // runs `./jobs/worker-3.js` at 10:15am and 5:15pm every day except on Tuesday
    {
      name: 'worker-3',
      interval: 'at 10:15 am also at 5:15pm except on Tuesday'
    },

    // runs `./jobs/worker-4.js` at 10:15am every weekday
    {
      name: 'worker-4',
      cron: '15 10 ? * *'
    },

    // runs `./jobs/worker-5.js` on after 10 minutes have elapsed
    {
      name: 'worker-5',
      timeout: '10m'
    },

    // runs `./jobs/worker-6.js` after 1 minute and every 5 minutes thereafter
    {
      name: 'worker-6',
      timeout: '1m',
      interval: '5m'
      // this is unnecessary but shows you can pass a Number (ms)
      // interval: ms('5m')
    },

    // runs `./jobs/worker-7.js` after 3 days and 4 hours
    {
      name: 'worker-7',
      // this example uses `human-interval` parsing
      timeout: '3 days and 4 hours'
    },

    // runs `./jobs/worker-8.js` at midnight (once)
    {
      name: 'worker-8',
      timeout: 'at 12:00 am'
    },

    // runs `./jobs/worker-9.js` every day at midnight
    {
      name: 'worker-9',
      interval: 'at 12:00 am'
    },

    // runs `./jobs/worker-10.js` at midnight on the 1st of every month
    {
      name: 'worker-10',
      cron: '0 0 1 * *'
    },

    // runs `./jobs/worker-11.js` at midnight on the last day of month
    {
      name: 'worker-11',
      cron: '0 0 L * *'
    },

    // runs `./jobs/worker-12.js` at a specific Date (e.g. in 3 days)
    {
      name: 'worker-12',
      // <https://github.com/iamkun/dayjs>
      date: dayjs().add(3, 'days').toDate()
      // you can also use momentjs
      // <https://momentjs.com/>
      // date: moment('1/1/20', 'M/D/YY').toDate()
      // you can pass Date instances (if it's in the past it will not get run)
      // date: new Date()
    },

    // runs `./jobs/worker-13.js` on start and every 2 minutes
    {
      name: 'worker-13',
      interval: '2m'
    },

    // runs `./jobs/worker-14.js` on start with custom `new Worker` options (see below)
    {
      name: 'worker-14',
      // <https://nodejs.org/api/worker_threads.html#worker_threads_new_worker_filename_options>
      worker: {
        workerData: {
          foo: 'bar',
          beep: 'boop'
        }
      }
    },

    // runs `./jobs/worker-15.js` **NOT** on start, but every 2 minutes
    {
      name: 'worker-15',
      timeout: false, // <-- specify `false` here to prevent default timeout (e.g. on start)
      interval: '2m'
    },

    // runs `./jobs/worker-16.js` on January 1st, 2022
    // and at midnight on the 1st of every month thereafter
    {
      name: 'worker-16',
      date: dayjs('1-1-2022', 'M-D-YYYY').toDate(),
      cron: '0 0 1 * *'
    }
  ]
});

// handle graceful reloads, pm2 support, and events like SIGHUP, SIGINT, etc.
const graceful = new Graceful({ brees: [bree] });
graceful.listen();

// start all jobs (this is the equivalent of reloading a crontab):
bree.start();

/*
// start only a specific job:
bree.start('foo');

// stop all jobs
bree.stop();

// stop only a specific job:
bree.stop('beep');

// run all jobs (this does not abide by timeout/interval/cron and spawns workers immediately)
bree.run();

// run a specific job (...)
bree.run('beep');
*/

Node.js Email Queue Job Scheduling Example

A very common use case for a Node.js job scheduler is the sending of emails.

We highly recommend you to use Bree in combination with the email-templates package (made by the same author). Not only does it let you easily manage email templates, but it also automatically opens email previews in your browser for you during local development (using preview-email).

You will then create in your application a MongoDB "email" collection (or SQL table) with the following properties (or SQL columns):

  • template (String) - the name of the email template
  • message (Object) - a Nodemailer message object
  • locals (Object) - an Object of locals that are passed to the template for rendering

Here are optional properties/columns that you may want to also add (you'll need to implement the logic yourself as the example provided below does not include it):

  • send_at (Date) - the Date you want to send an email (should default to current Date.now() when record is created, and can be overridden on a per job basis)
  • sent_at (Date) - the Date that the email actually got sent (set by your job in Bree - you would use this when querying for emails to send, and specifically exclude any emails that have a sent_at value sent in your query)
  • response (Object) - the mixed Object that is returned from Nodemailer sending the message (you should store this for historical data and so you can detect bounces)

In your application, you will then need to save a new record into the collection or table (where you want to trigger an email to be queued) with values for these properties.

Lastly, you will need to set up Bree to fetch from the email collection every minute (you can configure how frequent you wish, however you may want to implement locking, by setting a is_locked Boolean property, and subsequently unlocking any jobs locked more than X minutes ago – but typically this is not needed unless you are sending thousands of emails and have a slow SMTP transport).

const Bree = require('bree');
const Graceful = require('@ladjs/graceful');
const Cabin = require('cabin');

//
// we recommend using Cabin as it is security-focused
// and you can easily hook in Slack webhooks and more
// <https://cabinjs.com>
//
const logger = new Cabin();

const bree = new Bree({
  logger,
  jobs: [
    {
      // runs `./jobs/email.js` on start and every minute
      name: 'email',
      interval: '1m'
    }
  ]
});

Example contents of a file named ./jobs/email.js:

const os = require('os');
const { parentPort } = require('worker_threads');

const Cabin = require('cabin');
const Email = require('email-templates');
const pMap = require('p-map');

//
// we recommend using Cabin as it is security-focused
// and you can easily hook in Slack webhooks and more
// <https://cabinjs.com>
//
const logger = new Cabin();

//
// we recommend using email-templates to
// create, send, and manage your emails
// <https://email-templates.js.org>
//
const email = new Email({
  message: {
    // set a default from that will be set on all messages
    // (unless you specifically override it on an individual basis)
    from: 'elon@tesla.com'
  }
});

// store boolean if the job is cancelled
let isCancelled = false;

// how many emails to send at once
const concurrency = os.cpus().length;

// example database results
const results = [
  {
    template: 'welcome',
    message: {
      to: 'elon@spacex.com'
    },
    locals: {
      foo: 'bar',
      beep: 'boop'
    }
  }
  // ...
];

async function mapper(result) {
  // return early if the job was already cancelled
  if (isCancelled) return;
  try {
    const response = await email.send(result);
    logger.info('sent email', { response });
    // here is where you would write to the database that it was sent
    return response;
  } catch (err) {
    // catch the error so if one email fails they all don't fail
    logger.error(err);
  }
}

// handle cancellation (this is a very simple example)
if (parentPort)
  parentPort.once('message', message => {
    //
    // TODO: once we can manipulate concurrency option to p-map
    // we could make it `Number.MAX_VALUE` here to speed cancellation up
    // <https://github.com/sindresorhus/p-map/issues/28>
    //
    if (message === 'cancel') isCancelled = true;
  });

(async () => {
  // query database results for emails not sent
  // and iterate over them with concurrency
  await pMap(results, mapper, { concurrency });

  // signal to parent that the job is done
  if (parentPort) parentPort.postMessage('done');
  else process.exit(0);
})();

Example contents of a file named ./emails/welcome/html.pug:

p Welcome to Tesla
ul
  li
    strong Foo value:
    = ' '
    = foo
  li
    strong Beep value:
    = ' '
    = beep

Example contents of a file named ./emails/welcome/subject.pug:

= 'Welcome to Tesla'

NOTE: We have provided a complete demo example using Express at https://github.com/breejs/express-example.

Instance Options

Here is the full list of options and their defaults. See index.js for more insight if necessary.

Property Type Default Value Description
logger Object console This is the default logger. We recommend using Cabin instead of using console as your default logger.
root String path.resolve('jobs') Set this value to false to prevent requiring a root directory of jobs (e.g. if your jobs are not all in one directory).
timeout Number 0 Default timeout for jobs (e.g. a value of 0 means that jobs will start on boot by default unless a job has a property of timeout defined. Set this to false if you do not wish for a default value to be set for jobs. This value does not apply to jobs with a property of date.
interval Number 0 Default interval for jobs (e.g. a value of 0 means that there is no interval, and a value greater than zero indicates a default interval will be set with this value). This value does not apply to jobs with a property of cron.
jobs Array [] Defaults to an empty Array, but if the root directory has a index.js file, then it will be used. This allows you to keep your jobs and job definition index in the same place. See Job Options below, and Usage and Examples above for more insight.
hasSeconds Boolean false This value is passed to later for parsing jobs, and can be overridden on a per job basis. See later cron parsing documentation for more insight. Note that setting this to true will automatically set cronValidate defaults to have { preset: 'default', override: { useSeconds: true } }
cronValidate Object {} This value is passed to cron-validate for validation of cron expressions. See the cron-validate documentation for more insight.
closeWorkerAfterMs Number 0 If you set a value greater than 0 here, then it will terminate workers after this specified time (in milliseconds). By default there is no termination done, and jobs can run for infinite periods of time.
defaultExtension String js This value can either be js or mjs. The default is js, and is the default extension added to jobs that are simply defined with a name and without a path. For example, if you define a job test, then it will look for /path/to/root/test.js as the file used for workers.
worker Object {} These are default options to pass when creating a new Worker instance. See the Worker class documentation for more insight.
outputWorkerMetadata Boolean false By default worker metadata is not passed to the second Object argument of logger. However if you set this to true, then logger will be invoked internally with two arguments (e.g. logger.info('...', { worker: ... })). This worker property contains isMainThread (Boolean), resourceLimits (Object), and threadId (String) properties; all of which correspond to Workers metadata. This can be overridden on a per job basis.

Job Options

See Interval, Timeout, Date, and Cron Validate below for more insight besides this table:

Property Type Description
name String The name of the job. This should match the base file path (e.g. foo if foo.js is located at /path/to/jobs/foo.js) unless path option is specified. A value of index, index.js, and index.mjs are reserved values and cannot be used here.
path String The path of the job used for spawning a new Worker with. If not specified, then it defaults to the value for name plus the default file extension specified under Instance Options.
timeout Number, Object, String, or Boolean Sets the duration in milliseconds before the job starts (it overrides the default inherited timeout as set in Instance Options. A value of 0 indicates it will start immediately. This value can be a Number, String, or a Boolean of false (which indicates it will NOT inherit the default timeout from Instance Options). See Job Interval and Timeout Values below for more insight into how this value is parsed.
interval Number, Object, or String Sets the duration in milliseconds for the job to repeat itself, otherwise known as its interval (it overrides the default inherited interval as set in Instance Options). A value of 0 indicates it will not repeat and there will be no interval. If the value is greater than 0 then this value will be used as the interval. See Job Interval and Timeout Values below for more insight into how this value is parsed.
date Date This must be a valid JavaScript Date (we use instance of Date for comparison). If this value is in the past, then it is not run when jobs are started (or run manually). We recommend using dayjs for creating this date, and then formatting it using the toDate() method (e.g. dayjs().add('3, 'days').toDate()). You could also use moment or any other JavaScript date library, as long as you convert the value to a Date instance here.
cron String A cron expression to use as the job's interval, which is validated against cron-validate and parsed by later.
hasSeconds Boolean Overrides the Instance Options hasSeconds property if set. Note that setting this to true will automatically set cronValidate defaults to have { preset: 'default', override: { useSeconds: true } }
cronValidate Object Overrides the Instance Options cronValidate property if set.
closeWorkerAfterMs Number Overrides the Instance Options closeWorkerAfterMs property if set.
worker Object Overrides the Instance Options worker property if set.
outputWorkerMetadata Boolean Overrides the Instance Options outputWorkerMetadata property if set.

Job Interval and Timeout Values

These values can include Number, Object, and String variable types:

  • Number values indicates the number of milliseconds for the timeout or interval
  • Object values must be a later schedule object value (e.g. later.schedule(later.parse.cron('15 10 * * ? *'))))
  • String values can be either a later, human-interval, or ms String values (e.g. later supports Strings such as every 5 mins, human-interval supports Strings such as 3 days and 4 hours, and ms supports Strings such as 4h for four hours)

Listening for events

Bree extends from EventEmitter and emits two events:

  • worker created with an argument of name
  • worker deleted with an argument of name

If you'd like to know when your workers are created (or deleted), you can do so through this example:

bree.on('worker created', (name) => {
  console.log('worker created', name);
  console.log(bree.workers[name]);
});

bree.on('worker deleted', (name) => {
  console.log('worker deleted', name);
  console.log(typeof bree.workers[name] === 'undefined');
});

Cancellation, Retries, Stalled Jobs, and Graceful Reloading

We recommend that you listen for "cancel" event in your worker paths. Doing so will allow you to handle graceful cancellation of jobs. For example, you could use p-cancelable

Here's a quick example of how to do that (e.g. ./jobs/some-worker.js):

// <https://nodejs.org/api/worker_threads.html>
const { parentPort } = require('worker_threads');

// ...

function cancel() {
  // do cleanup here
  // (if you're using @ladjs/graceful, the max time this can run by default is 5s)

  // send a message to the parent that we're ready to terminate
  // (you could do `process.exit(0)` or `process.exit(1)` instead if desired
  // but this is a bit of a cleaner approach for worker termination
  if (parentPort) parentPort.postMessage('cancelled');
  else process.exit(0);
}

if (parentPort)
  parentPort.once('message', message => {
    if (message === 'cancel') return cancel();
  });

If you'd like jobs to retry, simply wrap your usage of promises with p-retry.

We leave it up to you to have as much fine-grained control as you wish.

See @ladjs/graceful for more insight into how this package works.

Interval, Timeout, Date, and Cron Validation

If you need help writing cron expressions, you can reference crontab.guru.

We support later, human-interval, or ms String values for both timeout and interval.

If you pass a cron property, then it is validated against cron-validate.

You can pass a Date as the date property, but you cannot combine both date and timeout.

If you do pass a Date, then it is only run if it is in the future.

See Job Interval and Timeout Values above for more insight.

Writing jobs with Promises and async-await

Until Node LTS has a stable release with top-level async-await support, here is the working alternative:

const { parentPort } = require('worker_threads');

const delay = require('delay');
const ms = require('ms');

(async () => {
  // wait for a promise to finish
  await delay(ms('10s'));

  // signal to parent that the job is done
  if (parentPort) parentPort.postMessage('done');
  else process.exit(0);
})();

Callbacks, Done, and Completion States

To close out the worker and signal that it is done, you can simply parentPort.postMessage('done'); and/or process.exit(0).

While writing your jobs (which will run in worker threads), you should do one of the following:

  • Signal to the main thread that the process has completed by sending a "done" message (per the example above in Writing jobs with Promises and async-await)
  • Exit the process if there is NOT an error with code 0 (e.g. process.exit(0);)
  • Throw an error if an error occurs (this will bubble up to the worker event error listener and terminate it)
  • Exit the process if there IS an error with code 1 (e.g. process.exit(1))

Long-running jobs

If a job is already running, a new worker thread will not be spawned, instead logger.error will be invoked with an error message (no error will be thrown, don't worry). This is to prevent bad practices from being used. If you need something to be run more than one time, then make the job itself run the task multiple times. This approach gives you more fine-grained control.

By default, workers run indefinitely and are not closed until they exit (e.g. via process.exit(0) or process.exit(1), OR send to the parent port a "close" message, which will subsequently call worker.close() to close the worker thread.

If you wish to specify a maximum time (in milliseconds) that a worker can run, then pass closeWorkerAfterMs (Number) either as a default option when creating a new Bree() instance (e.g. new Bree({ closeWorkerAfterMs: ms('10s') })) or on a per-job configuration, e.g. { name: 'beep', closeWorkerAfterMs: ms('5m') }.

Complex timeouts and intervals

Since we use later, you can pass an instance of later.schedule as the timeout or interval property values (e.g. if you need to construct something manually).

You can also use dayjs to construct dates (e.g. from now or a certain date) to millisecond differences using dayjs().diff(new Date(), 'milliseconds'). You would then pass that returned Number value as timeout or interval as needed.

Custom Worker Options

You can pass a default worker configuration object as new Bree({ worker: { ... } });.

These options are passed to the options argument when we internally invoke new Worker(path, options).

Additionally, you can pass custom worker options on a per-job basis through a worker property Object on the job definition.

See complete documentation here for options https://nodejs.org/api/worker_threads.html#worker_thre (but you usually don't have to modify these).

Concurrency

We recommend using the following packages in your workers for handling concurrency:

Real-world usage

More detailed examples can be found in Forward Email and Lad.

Alternatives that are not production-ready

Kudos to the authors of all these packages, however they did not work well enough for myself in real-world production environments.

Contributors

Name Website
Nick Baugh http://niftylettuce.com/
shadowgate15 https://github.com/shadowgate15

License

MIT © Nick Baugh

#