Orchestrator

A module for sequencing and executing tasks and dependencies in maximum concurrency

Usage

1. Get a reference:

var Orchestrator = require('orchestrator');
var orchestrator = new Orchestrator();

2. Load it up with stuff to do:

orchestrator.add('thing1', function(){
  // do stuff
});
orchestrator.add('thing2', function(){
  // do stuff
});

3. Run the tasks:

orchestrator.start('thing1', 'thing2', function (err) {
  // all done
});

API

orchestrator.add(name[, deps][, function]);

Define a task

orchestrator.add('thing1', function(){
  // do stuff
});

name

Type: String

The name of the task.

deps

Type: Array

An array of task names to be executed and completed before your task will run.

orchestrator.add('mytask', ['array', 'of', 'task', 'names'], function() {
  // Do stuff
});

Note: Are your tasks running before the dependencies are complete? Make sure your dependency tasks are correctly using the async run hints: take in a callback or return a promise or event stream.

fn

Type: function

The function that performs the task's operations. For asynchronous tasks, you need to provide a hint when the task is complete:

• Take in a callback
• Return a stream or a promise

examples:

Accept a callback:

orchestrator.add('thing2', function(callback){
  // do stuff
  callback(err);
});

Return a promise:

var Q = require('q');

orchestrator.add('thing3', function(){
  var deferred = Q.defer();

  // do async stuff
  setTimeout(function () {
    deferred.resolve();
  }, 1);

  return deferred.promise;
});

Return a stream: (task is marked complete when stream ends)

var map = require('map-stream');

orchestrator.add('thing4', function(){
  var stream = map(function (args, cb) {
    cb(null, args);
  });
  // do stream stuff
  return stream;
});

Note: By default, tasks run with maximum concurrency -- e.g. it launches all the tasks at once and waits for nothing. If you want to create a series where tasks run in a particular order, you need to do two things:

• give it a hint to tell it when the task is done,
• and give it a hint that a task depends on completion of another.

For these examples, let's presume you have two tasks, "one" and "two" that you specifically want to run in this order:

1. In task "one" you add a hint to tell it when the task is done. Either take in a callback and call it when you're done or return a promise or stream that the engine should wait to resolve or end respectively.

2. In task "two" you add a hint telling the engine that it depends on completion of the first task.

So this example would look like this:

var Orchestrator = require('orchestrator');
var orchestrator = new Orchestrator();

// takes in a callback so the engine knows when it'll be done
orchestrator.add('one', function (cb) {
    // do stuff -- async or otherwise
    cb(err); // if err is not null or undefined, the orchestration will stop, and note that it failed
});

// identifies a dependent task must be complete before this one begins
orchestrator.add('two', ['one'], function () {
    // task 'one' is done now
});

orchestrator.start('one', 'two');

orchestrator.hasTask(name);

Have you defined a task with this name?

name

Type: String

The task name to query

orchestrator.start(tasks...[, cb]);

Start running the tasks

tasks

Type: String or Array of Strings

Tasks to be executed. You may pass any number of tasks as individual arguments.

cb

Type: function: function (err) {

Callback to call after run completed.

Passes single argument: err: did the orchestration succeed?

Note: Tasks run concurrently and therefore may not complete in order. Note: Orchestrator uses sequencify to resolve dependencies before running, and therefore may not start in order. Listen to orchestration events to watch task running.

orchestrator.start('thing1', 'thing2', 'thing3', 'thing4', function (err) {
  // all done
});

orchestrator.start(['thing1','thing2'], ['thing3','thing4']);

FRAGILE: Orchestrator catches exceptions on sync runs to pass to your callback but doesn't hook to process.uncaughtException so it can't pass those exceptions to your callback

FRAGILE: Orchestrator will ensure each task and each dependency is run once during an orchestration run even if you specify it to run more than once. (e.g. orchestrator.start('thing1', 'thing1') will only run 'thing1' once.) If you need it to run a task multiple times, wait for the orchestration to end (start's callback) then call start again. (e.g. orchestrator.start('thing1', function () {orchestrator.start('thing1');}).) Alternatively create a second orchestrator instance.

orchestrator.stop()

Stop an orchestration run currently in process

Note: It will call the start() callback with an err noting the orchestration was aborted

orchestrator.on(event, cb);

Listen to orchestrator internals

event

Type: String

Event name to listen to:

• start: from start() method, shows you the task sequence
• stop: from stop() method, the queue finished successfully
• err: from stop() method, the queue was aborted due to a task error
• task_start: from _runTask() method, task was started
• task_stop: from _runTask() method, task completed successfully
• task_err: from _runTask() method, task errored
• task_not_found: from start() method, you're trying to start a task that doesn't exist
• task_recursion: from start() method, there are recursive dependencies in your task list

cb

Type: function: function (e) {

Passes single argument: e: event details

orchestrator.on('task_start', function (e) {
  // e.message is the log message
  // e.task is the task name if the message applies to a task else `undefined`
  // e.err is the error if event is 'err' else `undefined`
});
// for task_end and task_err:
orchestrator.on('task_stop', function (e) {
  // e is the same object from task_start
  // e.message is updated to show how the task ended
  // e.duration is the task run duration (in seconds)
});

Note: fires either *stop or *err but not both.

orchestrator.onAll(cb);

Listen to all orchestrator events from one callback

cb

Type: function: function (e) {

Passes single argument: e: event details

orchestrator.onAll(function (e) {
  // e is the original event args
  // e.src is event name
});

LICENSE

(MIT License)

Copyright (c) 2013 Richardson & Sons, LLC

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.