Foxx Job Queues

If you have never built a Foxx App, then you can make your own first Foxx App using our cookbook.

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.

--server.foxx-queues flag
If true, the Foxx queues will be available and jobs in the queues will be executed asynchronously.
The default is true. When set to false the queue manager will be disabled and any jobs are prevented from being processed, which may reduce CPU load a great deal.

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

--server.foxx-queues-poll-interval value
The poll interval for the Foxx queues manager. The value is specified in seconds. Lower values will mean more immediate and more frequent Foxx queue job execution, but will make the queue thread wake up and query the queues more often. When set to a low value, the queue thread might cause CPU load.
The default is 1 second. If Foxx queues are not used much, then this value may be increased to make the queues thread wake up less.

For the low-level functionality see the chapter on the Task Management module.

As of ArangoDB 2.6, Foxx queue job types are defined as regular Foxx scripts. To learn more about Foxx scripts, see the chapter on Foxx scripts. Function-based job types are still supported in 2.6 but have been removed in 2.7.

For an example of re-usable job types see the various mailer apps available in the Foxx app store.

Creating or updating a queue

Creates a queue with the given name and maximum number of workers.

Foxx.queues.create(name, [maxWorkers])

Returns the Queue instance 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 context of the current database.

Parameters

• name: the name of the queue to create
• maxWorkers (optional): the maximum number of workers. Default: 1

Examples

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

Fetching an existing queue

Fetches a queue with the given name.

Foxx.queues.get(name)

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

The queue will be looked for in the context of the current database.

Parameters

• name: the name of the queue to fetch

Examples

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

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

Otherwise the Queue instance will be returned:

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

Deleting a queue

Deletes the queue with the given name from the database.

Foxx.queues.delete(name)

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

Parameters

• name: the name of the queue to delete

Examples

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

Adding a job to a queue

Adds a job to the given queue.

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

Queue::push(script, data, [opts])

Returns the job id.

Parameters

• script: a job type definition, consisting of an object with the following properties:
  • name: the name of the script that will be invoked.
  • mount: the mount path of the app that defines the script.
  • backOff (optional): 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. Default: 1000.
  • maxFailures (optional): the 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. Default: 0.
  • schema (optional): a Joi schema to validate a job’s data against before enqueuing the job.
  • preprocess (optional): a function to pre-process a job’s (validated) data before serializing it in the queue.
  • repeatTimes (optional): 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. Default: 0 (no repeat).
  • repeatUntil (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 (optional): 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. Default: 0.
• data: the job data of the job; must be serializable to JSON.
• opts (optional): an object with any of the following properties:
• success (optional): a function to be called after the job has been completed successfully.
• failure (optional): a function to be called after the job has failed too many times.
• delayUntil (optional): a timestamp in milliseconds (or Date instance) until which the execution of the job should be delayed. Default: Date.now().
• backOff (optional): see script.backOff.
• maxFailures (optional): see script.maxFailures.
• repeatTimes (optional): see script.repeatTimes.
• repeatUntil (optional): see script.repeatUntil.
• repeatDelay (optional): see script.repeatDelay.

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: the return value of the script for the current run of the job.
• jobData: the data passed to this method.
• job: the ArangoDB document representing the job’s current state.

Examples

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

var Foxx = require("org/arangodb/foxx");
var queue = Foxx.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):

var Foxx = require("org/arangodb/foxx");
var queue = Foxx.queues.create("my-queue");
var 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 "console is not defined"
  }}
);

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

var Foxx = require("org/arangodb/foxx");
var queue = Foxx.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
  }
);

Fetching a job from the queue

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

The job will be looked for in the specified queue in the context of the current database.

Queue::get(jobId)

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

Parameters

• jobId: the id of the job to create a proxy object for.

Examples

var jobId = queue.push("log", "Hello World!");
var job = queue.get(jobId);
assertEqual(job.id, jobId);

Deleting a job from the queue

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

Queue::delete(jobId)

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

Fetching an array of jobs in a queue

Examples

queue.push("log", "Hello World!", {delayUntil: Date.now() + 50});
assertEqual(queue.pending("log").length, 1);
// 50 ms later...
assertEqual(queue.pending("log").length, 0);
assertEqual(queue.progress("log").length, 1);
// even later...
assertEqual(queue.progress("log").length, 0);
assertEqual(queue.complete("log").length, 1);

Fetching an array of pending jobs in a queue

Queue::pending([script])

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 for in the specified queue in the context of the current database.

Parameters

• script (optional): an object with the following properties:
• name: name of the script.
• mount: mount path of the app defining the script.

Fetching an array of jobs that are currently in 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 for in the specified queue in the context of the current database.

Parameters

• script (optional): an object with the following properties:
• name: name of the script.
• mount: mount path of the app defining the script.

Fetching an array of completed jobs in a queue

Queue::complete([script])

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 for in the specified queue in the context of the current database.

Parameters

• script (optional): an object with the following properties:
• name: name of the script.
• mount: mount path of the app defining the script.

Fetching an array of failed jobs in a queue

Queue::failed([script])

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 for in the specified queue in the context of the current database.

Parameters

• script (optional): an object with the following properties:
• name: name of the script.
• mount: mount path of the app defining the script.

Fetching an array of all jobs in a queue

Queue::all([script])

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 for in the specified queue in the context of the current database.

Parameters

• script (optional): an object with the following properties:
• name: name of the script.
• mount: mount path of the app defining the script.

Aborting a job

Aborts a non-completed job.

Job::abort()

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