task-queue

Async [Priority] Task Queue

Simple Usage

var tq = require('task-queue');

var queue = tq.Queue({capacity: 10, concurrency: 1});
// initialize a 10-slot normal queue. concurrency 1 is the default
// it tells the worker in how many tasks it can work at a time

queue.start();
// start queue - now it's waiting for the queue to be populated

queue.enqueue(some_function); // simple way to enqueue a function
queue.enqueue(some_function, {args: args_array}); // provide args to the function

// both tasks above will be executed (one at a time, since concurrency is 1)

queue.stop();
// stops the queue execution
// it wont stop the tasks the worker is currently working on

queue.finished = some_callback_function;
// you can define a finished() callback that will
// be called everytime the worker empties the queue

var priority = tq.PriorityQueue({capacity: 10});
// initialize a 10-slot priority queue

priority.start();

What is this?

task-queue is a simple node package which provides an async task queue that supports concurrency, priority and timeouts. It provides callbacks for tasks completed as well as a way to handle single shot calls (run all the tasks once).

Features

• Async
• Concurrency
• Timeouts
• Callbacks
• Single-shot calls
• Priority

Implementation-level details

The Queue is implemented over a resizable buffer so you do not need to worry about a max-space as well as massive reallocations. Just tell it the initial capacity you need and it will do the hard work for you.

The PriorityQueue is implemented over a resizable binary heap so you do not need to worry about max-space, massive reallocations as well as algorithm complexity.

API

Queue

• Queue(options) - initialize a queue with the given option
  • options:
    • capacity - Queue initial capacity. (required)
    • concurrency - how many tasks the worker will execute at a time. default 1.
    • timeout - how much time the worker will sleep after each execution cycle.
• isRunning() - returns boolean indicating if running mode is set.
• concurrency([value]) - get/set concurrency
• timeout([value]) - get/set timeout
• size() - returns how many elements are currently on the queue
• toArray() - returns an array representation of the queue.

Flow

• enqueue(fn [, task-opts]) - add task from function fn to the queue.
  • task-opts:
    • args - arguments array that will be applied to fn call.
• dequeue() - pull the first element from the queue, or null if it's empty.
• singleShot() - puts the queue in single-shot mode. all the queue elements will be executed once from now. Nothing can be enqueued while single-shot is active. When all the tasks are finished, the queue is put back in normal mode. you can stop() single-shot calls as well.
• start() - puts the queue in running mode. The worker will execute tasks whenever they are available if it's not sleeping.
• stop() - unset running mode and/or unset single-shot mode. The worker will finish all the tasks that were already dequeued and then go idle.

Callbacks

• finished() - called when all the tasks from the queue were executed (queue was emptied).
• finishedTask([task-return]) - called whenever a task is executed. task-return is the return value of the task corresponding function.

PriorityQueue extends Queue

• PriorityQueue - super constructor.

Flow

• enqueue(fn [, task-opts]) - add task from function fn to the queue.
  • task-opts:
    • args - arguments array that will be applied to fn call.
    • priority - comparable (with > or <) value that will be used to sort tasks executions by their relevance.