Foxx queues

const queues = require('@arangodb/foxx/queues')

Foxx allows defining job queues that let you perform slow or expensive actions asynchronously. These queues can be used to send e-mails, call external APIs or perform other actions that you do not want to perform directly or want to retry on failure.

Foxx queue jobs can be any script named in the manifest of a service in the same database.

Please note that Foxx queues are database-specific. Queues and jobs are always relative to the database in which they are created or accessed.

For disabling the Foxx queues feature or adjusting the polling interval see the foxx.queues and foxx.queues-poll-interval options.

For the low-level functionality see the chapter on the task management module.

Managing queues

queues.create

queues.create(name, [maxWorkers]): Queue

Returns the queue for the given name. If the queue does not exist, a new queue with the given name will be created. If a queue with the given name already exists and maxWorkers is set, the queue’s maximum number of workers will be updated. The queue will be created in the current database.

Arguments

• name: string

  Name of the queue to create.

• maxWorkers: number (Default: 1)

  The maximum number of workers.

Examples

// Create a queue with the default number of workers (i.e. one)
const queue1 = queues.create("my-queue");
// Create a queue with a given number of workers
const queue2 = queues.create("another-queue", 2);
// Update the number of workers of an existing queue
const queue3 = queues.create("my-queue", 10);
// queue1 and queue3 refer to the same queue
assertEqual(queue1, queue3);

queues.get

queues.get(name): Queue

Returns the queue for the given name. If the queue does not exist an exception is thrown instead.

The queue will be looked up in the current database.

Arguments

• name: string

  Name of the queue to fetch.

Examples

If the queue does not yet exist an exception is thrown:

queues.get("some-queue");
// Error: Queue does not exist: some-queue
//     at ...

Otherwise the queue will be returned:

const queue1 = queues.create("some-queue");
const queue2 = queues.get("some-queue");
assertEqual(queue1, queue2);

queues.delete

queues.delete(name): boolean

Returns true if the queue was deleted successfully. If the queue did not exist, it returns false instead. The queue will be looked up and deleted in the current database.

When a queue is deleted, jobs on that queue will no longer be executed.

Deleting a queue will not delete any jobs on that queue.

Arguments

• name: string

  Name of the queue to delete.

Examples

const queue = queues.create("my-queue");
queues.delete("my-queue"); // true
queues.delete("my-queue"); // false

Queue API

queue.push

queue.push(script, data, [opts]): string

The job will be added to the specified queue in the current database.

Returns the job id.

Arguments

• script: object

  A job type definition, consisting of an object with the following properties:

  • name: string

    Name of the script that will be invoked.

  • mount: string

    Mount path of the service that defines the script.

  • backOff: Function | number (Default: 1000)

    Either a function that takes the number of times the job has failed before as input and returns the number of milliseconds to wait before trying the job again, or the delay to be used to calculate an exponential back-off, or 0 for no delay.

  • maxFailures: number | Infinity (Default: 0):

    Number of times a single run of a job will be re-tried before it is marked as "failed". A negative value or Infinity means that the job will be re-tried on failure indefinitely.

  • schema: Schema (optional)

    Schema to validate a job’s data against before enqueuing the job.

  • preprocess: Function (optional)

    Function to pre-process a job’s (validated) data before serializing it in the queue.

• data: any

  Job data of the job; must be serializable to JSON.

• opts: object (optional)

  Object with any of the following properties:

  • success: Function (optional)

    Function to be called after the job has been completed successfully.

  • failure: Function (optional)

    Function to be called after the job has failed too many times.

  • delayUntil: number | Date (Default: Date.now())

    Timestamp in milliseconds (or Date instance) until which the execution of the job should be delayed.

  • backOff: Function | number (Default: 1000)

    See script.backOff.

  • maxFailures: number | Infinity (Default: 0):

    See script.maxFailures.

  • repeatTimes: number (Default: 0)

    If set to a positive number, the job will be repeated this many times (not counting recovery when using maxFailures). If set to a negative number or Infinity, the job will be repeated indefinitely. If set to 0 the job will not be repeated.

  • repeatUntil: number | Date (optional)

    If the job is set to automatically repeat, this can be set to a timestamp in milliseconds (or Date instance) after which the job will no longer repeat. Setting this value to zero, a negative value or Infinity has no effect.

  • repeatDelay: number (Default: 0)

    If the job is set to automatically repeat, this can be set to a non-negative value to set the number of milliseconds for which the job will be delayed before it is started again.

Note that if you pass a function for the backOff calculation, success callback or failure callback options the function will be serialized to the database as a string and therefore must not rely on any external scope or external variables.

When the job is set to automatically repeat, the failure callback will only be executed when a run of the job has failed more than maxFailures times. Note that if the job fails and maxFailures is set, it will be rescheduled according to the backOff until it has either failed too many times or completed successfully before being scheduled according to the repeatDelay again. Recovery attempts by maxFailures do not count towards repeatTimes.

The success and failure callbacks receive the following arguments:

• result: any

  The return value of the script for the current run of the job.

• jobData: any

  The data passed to this method.

• job: object

  ArangoDB document representing the job’s current state.

Examples

Let’s say we have an service mounted at /mailer that provides a script called send-mail:

'use strict';
const queues = require('@arangodb/foxx/queues');
const queue = queues.create('my-queue');
queue.push(
  {mount: '/mailer', name: 'send-mail'},
  {to: 'hello@example.com', body: 'Hello world'}
);

This will not work, because log was defined outside the callback function (the callback must be serializable to a string):

// WARNING: THIS DOES NOT WORK!
'use strict';
const queues = require('@arangodb/foxx/queues');
const queue = queues.create('my-queue');
const log = require('console').log; // outside the callback's function scope
queue.push(
  {mount: '/mailer', name: 'send-mail'},
  {to: 'hello@example.com', body: 'Hello world'},
  {success: function () {
    log('Yay!'); // throws 'log is not defined'
  }}
);

Here’s an example of a job that will be executed every 5 seconds until tomorrow:

'use strict';
const queues = require('@arangodb/foxx').queues;
const queue = queues.create('my-queue');
queue.push(
  {mount: '/mailer', name: 'send-mail'},
  {to: 'hello@example.com', body: 'Hello world'},
  {
    repeatTimes: Infinity,
    repeatUntil: Date.now() + (24 * 60 * 60 * 1000),
    repeatDelay: 5 * 1000
  }
);

queue.get

queue.get(jobId): Job

Creates a proxy object representing a job with the given job id.

The job will be looked up in the specified queue in the current database.

Returns the job for the given jobId. Properties of the job object will be fetched whenever they are referenced and can not be modified.

Arguments

• jobId: string

  The id of the job to create a proxy object for.

Examples

const jobId = queue.push({mount: '/logger', name: 'log'}, 'Hello World!');
const job = queue.get(jobId);
assertEqual(job.id, jobId);

queue.delete

queue.delete(jobId): boolean

Deletes a job with the given job id. The job will be looked up and deleted in the specified queue in the current database.

Arguments

• jobId: string

  The id of the job to delete.

Returns true if the job was deleted successfully. If the job did not exist it returns false instead.

queue.pending

queue.pending([script]): Array<string>

Returns an array of job ids of jobs in the given queue with the status "pending", optionally filtered by the given job type. The jobs will be looked up in the specified queue in the current database.

Arguments

• script: object (optional)

  An object with the following properties:

• name: string

Name of the script.

• mount: string

Mount path of the service defining the script.

Examples

const logScript = {mount: '/logger', name: 'log'};
queue.push(logScript, 'Hello World!', {delayUntil: Date.now() + 50});
assertEqual(queue.pending(logScript).length, 1);
// 50 ms later...
assertEqual(queue.pending(logScript).length, 0);
assertEqual(queue.progress(logScript).length, 1);
// even later...
assertEqual(queue.progress(logScript).length, 0);
assertEqual(queue.complete(logScript).length, 1);

queue.progress

queue.progress([script])

Returns an array of job ids of jobs in the given queue with the status "progress", optionally filtered by the given job type. The jobs will be looked up in the specified queue in the current database.

Arguments

• script: object (optional)

  An object with the following properties:

• name: string

Name of the script.

• mount: string

Mount path of the service defining the script.

queue.complete

queue.complete([script]): Array<string>

Returns an array of job ids of jobs in the given queue with the status "complete", optionally filtered by the given job type. The jobs will be looked up in the specified queue in the current database.

Arguments

• script: object (optional)

  An object with the following properties:

• name: string

Name of the script.

• mount: string

Mount path of the service defining the script.

queue.failed

queue.failed([script]): Array<string>

Returns an array of job ids of jobs in the given queue with the status "failed", optionally filtered by the given job type. The jobs will be looked up in the specified queue in the current database.

Arguments

• script: object (optional)

  An object with the following properties:

• name: string

Name of the script.

• mount: string

Mount path of the service defining the script.

queue.all

queue.all([script]): Array<string>

Returns an array of job ids of all jobs in the given queue, optionally filtered by the given job type. The jobs will be looked up in the specified queue in the current database.

Arguments

• script: object (optional)

  An object with the following properties:

• name: string

Name of the script.

• mount: string

Mount path of the service defining the script.

Job API

job.abort

job.abort(): void

Aborts a non-completed job.

Sets a job’s status to "failed" if it is not already "complete", without calling the job’s onFailure callback.