Job Classes

For most Ruby applications the preferred way to write jobs in Zizq will by including the Zizq::Job module in your Ruby classes. This module adds instance and class methods to the class, which enable dispatching work to instances if that class.

Zizq::Job

In Zizq, jobs have a number of required attributes, such as a named queue, a job type and a payload. A number of optional attributes also exist. Zizq::Job provides convenience methods to derive and set these attributes, allowing you to think only in terms of these simple job classes when writing code for your application.

Defining a Job Class

Any named class can include Zizq::Job. This can be a top-level class, or a class namespaced within a module hierarchy. Classes including Zizq::Job must implement a #perform method; the arguments to which are arbitrary.

Caution

You cannot make an anonymous class a Zizq::Job. The worker would have no way of finding it and instantiating it.

class MyApp::MyJob
  include Zizq::Job

  def perform(arg1, arg2)
    puts "Hello, #{arg1} and #{arg2}"
  end
end

We would enqueue an instance of this job by calling Zizq.enqueue with the class and the job arguments.

Zizq.enqueue(MyApp::MyJob, "Bill", "Ben")
# #<Zizq::Resources::Job @data={"id"=>"03ftfjjuhc59aliu4wadzi06j", ... }>

This job isn’t very interesting but it is a valid Zizq::Job implementation and allows us to highlight some concepts.

Tip

The examples in this documentation use positional arguments in the #perform method. This is perfectly valid but experience shows such methods are more difficult to evolve over time than those that use keyword arguments with optional defaults.

Job Attributes

Zizq will derive the job type from the class name "MyApp::MyJob".

Because the job class does not specify a queue explicitly, jobs of this type will be placed onto the default queue.

MyApp::MyJob.zizq_queue
# "default"

There are a number of class methods added to the job class—all prefixed with zizq_—which allow getting or setting the various attributes. These can all be overridden at enqueue-time too.

Specifying the Queue

Use zizq_queue to set or get the queue. Queue names must be valid UTF-8 and cannot contain any of the following reserved characters: ,, *, ?, [, ], {, }, \

The default queue is "default".

class MyApp::MyJob
  include Zizq::Job
  zizq_queue 'example'
end

MyApp::MyJob.zizq_queue
# "example"

Setting the Priority

Use zizq_priority to set or get the priority of the job. Valid values range between 0 and 65536. The default priority is not specified by the client, but by the Zizq server (generally 32768).

class MyApp::MyJob
  include Zizq::Job
  zizq_priority 500
end

MyApp::MyJob.zizq_priority
# 500

Setting the Backoff Policy

Use zizq_retry_limit to set the maximum number of retries before a job is marked "dead", and zizq_backoff to set the backoff formula parameters. The defaults are managed by the server (generally the default retry_limit is 25 and the backoff parameters are base: 10, exponent: 4, jitter: 30).

Backoff parameters are in seconds. Floating point values are acceptable. All three backoff arguments must be provided together.

The values are used in the following formula:

delay = base + (attempts ** exponent) + (rand(0.0..jitter) * attempts)

The randomness in the jitter component is designed to avoid situations where a cascade of failures all retry at the same time. They naturally spread out.

class MyApp::MyJob
  include Zizq::Job
  zizq_retry_limit 50
  zizq_backoff base: 5, exponent: 2, jitter: 10
end

MyApp::MyJob.zizq_retry_limit
# 50

MyApp::MyJob.zizq_backoff
# {:exponent=>2.0, :base=>5.0, :jitter=>10.0}

Setting the Retention Policy

Use zizq_retention to set or get the number of seconds for which dead and completed jobs are retained by the server before being reaped (hard deleted). Values are in seconds and floating points are acceptable. Thd defaults are managed by the server but are generally set at 7 days for dead jobs, and zero for completed jobs, meaning only dead jobs are kept.

Both arguments are optional.

class MyApp::MyJob
  include Zizq::Job
  zizq_retention dead: 86_400 * 30, completed: 86_400 * 2
end

MyApp::MyJob.zizq_retention
# {:completed=>172800.0, :dead=>2592000.0}

Specifying Job Uniqueness

Tip

This section of the documentation deals mostly with how to define unique jobs. See Unique Jobs for more detailed documentation on using this feature.

This requires a pro license on the server. Zizq is able to prevent duplicate enqueues of the same job within a specified job lifecycle scope. Use zizq_unique enable or disable uniqueness for a job.

The scope: argument specifies for which part of the job’s lifecycle it is considered unique. Options are:

The default scope is :queued. Zizq does not force you to select an arbitrary expiry deadline for unique jobs. The implementation is purely lifecycle based.

class MyApp::MyJob
  include Zizq::Job
  zizq_unique true, scope: :active
end

MyApp::MyJob.zizq_unique
# true

MyApp::MyJob.zizq_unique_scope
# :active

Unique Keys

Identity is based on the generation of a unique_key for a job, which is handled through the zizq_unique_key class method. This method takes the same arguments as the #perform method and returns a string for the unique key.

The default implementation is a function of the job type and its arguments.

MyApp::MyJob.zizq_unique_key("Bill", "Ben", example: 42)
# "MyApp::MyJob:0b9ca7f07581994caa848878576fed30e09e7177611c01aeafe7113921090c29"

MyApp::MyJob.zizq_unique_key("Bill", "Ben", example: 42)
# "MyApp::MyJob:0b9ca7f07581994caa848878576fed30e09e7177611c01aeafe7113921090c29"

MyApp::MyJob.zizq_unique_key("Bill", "Ben", example: 99)
# "MyApp::MyJob:3be19cc482f366dcd538c22b8536d7947672071b8c8fb3a2486ebfd04b2216b6"

If, for example, you need uniqueness only on a subset of the arguments you may override this method in your class:

class MyApp::MyJob
  include Zizq::Job
  zizq_unique true, scope: :active

  def self.zizq_unique_key(arg1, arg2, example:)
    super(arg1, arg2)
  end
end

MyApp::MyJob.zizq_unique_key("Bill", "Ben", example: 42)
# "MyApp::MyJob:bcd08012e829243d82e953a8140ffb58aeeb839e545ee1547a894bb2c9ba1b8f"
MyApp::MyJob.zizq_unique_key("Bill", "Ben", example: 99)
# "MyApp::MyJob:bcd08012e829243d82e953a8140ffb58aeeb839e545ee1547a894bb2c9ba1b8f"

Dynamic Job Configuration

When the client generates parameters to send to the Zizq server, it does this by calling zizq_enqueue_request(*args, **kwargs) on your job class, passing the job arguments. The return value is a Zizq::EnqueueRequest instance, exactly the same as the one yielded to the caller in Zizq.enqueue.

If you need to do any kind of dynamic configuration in your job classes, such as assigning a different priority based on time of day, or based on some of the arguments, you can override this method.

class MyApp::MyJob
  include Zizq::Job

  zizq_priority 500

  def self.zizq_enqueue_request(arg1, arg2, example:)
    req = super
    req.priority -= 50 if arg1 == "Bill"
    req
  end
end

Payload Serialization & Deserialization

When jobs are enqueued, Zizq produces the payload from the JSON serialized representation of the job arguments. This means by default all jobs arguments must be JSON serializable, though it is possible to write your own argument serialization and deserialization implementation.

The default serialization implementation is done through the zizq_serialize class method, which takes the same input arguments as the #perform method and returns a JSON-serializable value encoding those arguments (i.e. a Hash).

MyApp::MyJob.zizq_serialize("Bill", "Ben", example: 42)
# {"args"=>["Bill", "Ben"], "kwargs"=>{"example"=>42}}

A corresponding zizq_deserialize exists. This method returns two values: an args array for the positional arguments and a kwargs hash for any keyword arguments.

args, kwargs = MyApp::MyJob.zizq_deserialize({"args"=>["Bill", "Ben"], "kwargs"=>{"example"=>42}})

args
# ["Bill", "Ben"]
kwargs
# {:example=>42}

Your classes may override these methods if you need custom serialization logic.

Performing & Error Handling

The Zizq worker will instantiate your job class and call its #perform method with the same arguments that were used to enqueue the job. There is no maximum runtime imposed on jobs. They can run for as long as necessary. Provided the #perform method returns successfully and no errors are raised, Zizq will acknowledge (mark completed) this job. If any errors are raised from the #perform method, Zizq will report that error to the Zizq server and either backoff and retry, or kill the job, depending on the retry limit and the backoff policy.

If you do not want errors to trigger retries, you have two options:

1. Allow the error and configure zizq_retry_limit to 0.
2. Rescue the error inside the #perform method so the Zizq worker does not see it as a failure.

ActiveJob

If your application is a Rails app, you can also use Active Job to manage your jobs with the :zizq queue adapter. See Using Active Job for full documentation on this feature.