Module: Task::Task

Extended by:
ActiveSupport::Concern
Included in:
Task::Tasks::CompositeTask
Defined in:
lib/task/task.rb

Overview

A Task represents a task to be performed. The task can be serialized as JSON to be passed to other processes to complete, and can be stored in Cassandra as a means of ensuring “at-least-once” task completion for this task. So, an example lifecycle of a task would be:

1) A task is generated in a "master" job
2) The master job saves the task, providing a record that the task was generated.
3) The master job passes the task to another job to complete the task.
4) The worker job completes task, removing the record for that task.
5) If the worker job fails, the task is not completed and so the record for it persists.
6) A subsequent job can fetch the list of tasks, returning the tasks that failed to complete.
   This job could either serialize them to be completed by other jobs, or complete them directly.

A task has a unique id, belongs to a task list that group similar tasks together, and has data associated with it.

# In the process that generated the task serialized = my_task.as_hash

# In the process that acts on the hash my_task_copy = Task::Task.from_hash(serialized)

my_task.save

Task::DataInterface::Interface.new.find(task_list, task_id)

Task::DataInterface::Interface.new.all(task_list)

my_task.complete

Examples:

Defining a type of Task

class MyDeleteTask
  include Task::Task
  # This task has the item_id data field, representing the item to delete
  data_attr_reader :item_id
end

Creating a task

my_task = MyDeleteTask.build(:id => 'my_id', :task_list => "#{service.id}-delete", :item_id => '123')

Serializing and deserializing a task

Saving a task

Fetching a single task that has been saved

Fetching all tasks for a task list

Completing a task, so that it is not longer fetchable

Defined Under Namespace

Modules: ClassMethods

Class Method Summary collapse

Instance Method Summary collapse

Class Method Details

.all(task_list) ⇒ Enumerator::Lazy<Task::Task>

Returns all tasks for the provided task list

Parameters:

  • task_list (String)

Returns:



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# File 'lib/task/task.rb', line 125

def self.all(task_list)
  interface.all(task_list)
end

.find(task_list, id) ⇒ Task::Task|NilClass

Returns the task with the given id

Parameters:

  • task_list (String)
  • task_id (String)

Returns:



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# File 'lib/task/task.rb', line 118

def self.find(task_list, id)
  interface.find(task_list, id)
end

.from_hash(task_hash) ⇒ Task::Task

Returns The task object.

Parameters:

  • task_hash (Hash) —

    Should contain the :task_list, :id, :type, and :data fields

Returns:



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# File 'lib/task/task.rb', line 108

def self.from_hash(task_hash)
  task_hash = task_hash.dup
  type = task_hash.delete(:type)
  type.constantize.new(task_hash)
end

.interface ⇒ Task::DataInterface::Interface

The Data Interface used

Returns:



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# File 'lib/task/task.rb', line 131

def self.interface
  DataInterface::Interface.new
end

Instance Method Details

#as_hash ⇒ Hash

Serialized this Task as a hash

Returns:

  • (Hash) 


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# File 'lib/task/task.rb', line 143

def as_hash
  attributes.merge(type: self.class.to_s)
end

#complete ⇒ NilClass

Marks this task as complete, removing it from the datastore

Returns:

  • (NilClass) 


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# File 'lib/task/task.rb', line 157

def complete
  Task.interface.delete(task_list, id)
  nil
end

#execute(options = {}) ⇒ Object

Executes this task

Parameters:

  • options (Hash) (defaults to: {}) —

    Options specific to the execution of this task

Raises:

  • (NotImplementedError) 


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# File 'lib/task/task.rb', line 137

def execute(options = {})
  raise NotImplementedError.new('execute method not implemented')
end

#save ⇒ NilClass

Saves this task to the data store.

Returns:

  • (NilClass) 


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# File 'lib/task/task.rb', line 149

def save
  Task.interface.store(self)
  nil
end