taskgroup

Task Group

Group together synchronous and asynchronous tasks and execute them with support for concurrency, naming, and nesting.

Install

Backend

1. Install Node.js
2. npm install --save taskgroup

Frontend

1. See Browserify

Usage

Example

// Import
var TaskGroup = require('taskgroup').TaskGroup;

// Create our new group
var group = new TaskGroup();

// Define what should happen once the group has completed
group.once('complete', function(err,results){
	// Log the error that has occured
	console.log(err);
	// => null

	// Log the results that our group received from the executing items
	console.log(JSON.stringify(results));
	/*	=>
		[
			[null, 'first', 'task'],
			[null, 'second task'],
			[null, [
				[null, 'sub second task'],
				[null, 'sub first', 'task']
			]]
		]
	*/
});

// Add an asynchronous task that gives the result to the completion callback
group.addTask(function(complete){
	setTimeout(function(){
		complete(null, 'first', 'task');
	},500);
});

// Add a synchronous task that returns the result
// Errors should be returned, though if an error is thrown we will catch it
group.addTask(function(){
	return 'second task';
});

// Add a sub-group to our exiting group
group.addGroup(function(addGroup,addTask){
	// Tell this sub-group to execute in parallel (all at once) by setting its concurrency to unlimited
	// by default the concurrency for all groups is set to 1
	// which means that they execute in serial fashion (one after the other, instead of all at once)
	this.setConfig({concurrency:0});

	// Add an asynchronous task that gives its result to the completion callback
	addTask(function(complete){
		setTimeout(function(){
			complete(null, 'sub first', 'task');
		},500);
	});

	// Add a synchronous task that returns its result
	addTask(function(){
		return 'sub second task';
	});
});

// Execute our group
group.run();

TaskGroup API

new require('taskgroup').TaskGroup()

• Available methods:
  • constructor(name?,fn?) - create our new group, the arguments name and fn are optional, refer to their entries in configuration
  • setConfig(config) - set the configuration for the group, returns chain
  • addTask(args...) - create a new task item with the arguments and adds it to the group, returns the new task item
  • addGroup(args...) - create a new group item with the arguments and adds it to the group, returns the new group item
  • clear() - remove the remaining items to be executed
  • stop() - clear and pause
  • pause() - pause the execution of the items
  • run() - start/resume executing the items, returns chain
  • All those of EventEmitter2
• Available configuration:
  • name, no default - allows us to assign a name to the group, useful for debugging
  • fn(addGroup,addTask,complete?), no default - allows us to use an inline and self-executing style for defining groups, useful for nesting
  • concurrency, defaults to 1 - how many items shall we allow to be run at the same time, set to 0 to allow unlimited
  • pauseOnError, defaults to true - if an error occurs in one of our items, should we stop executing any remaining items?
    • setting to false will continue with execution with the other items even if an item experiences an error
• Available events:
  • run() - fired just before we execute the items
  • complete(err, results) - fired when all our items have completed
  • task.run(task) - fired just before a task item executes
  • task.complete(task, err, args...) - fired when a task item has completed
  • group.run(group) - fired just before a group item executes
  • group.complete(group, err, results) - fired when a group item has completed
  • item.run(item) - fired just before an item executes (fired for both sub-tasks and sub-groups)
  • item.complete(item, err, args...) - fired when an item has completed (fired for both sub-task and sub-groups)

Task API

new require('taskgroup').Task()

• Available methods:
  • constructor(name?,fn?) - create our new task, the arguments name and fn are optional though fn must be set at some point, refer to their entries in configuration
  • setConfig(config) - set the configuration for the group, returns chain
  • run() - execute the task
• Available configuration:
  • name, no default - allows us to assign a name to the group, useful for debugging
  • fn(complete?), no default - must be set at some point, it is the function to execute for the task, if it is asynchronous it should use the completion callback provided
  • args, no default - an array of arguments that you would like to precede the completion callback when executing fn
• Available events:
  • run() - fired just before we execute the task
  • complete(err, args...) - fired when the task has completed

History

You can discover the history inside the History.md file

License

Licensed under the incredibly permissive MIT License
Copyright © 2013+ Bevry Pty Ltd
Copyright © 2011-2012 Benjamin Arthur Lupton

Changelog

v3.1.0 2013 April 5

• Tasks can now have the arguments that are sent to them customized by the args configuration option
• Group inline functions now support an optional completion callback
• Group events for items now have their first argument as the item the event was for