task-strategy

Database rollback supported task strategy.

npm install task-strategy
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task-strategy

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Database rollback supported task strategy.
A strategy is made by one or more tactics, and a tactics is made by one or more tasks.
You can write tasks without care about the others.

Install

Install with npm:

npm install task-strategy

Example code

An example for executing a strategy.

var Strategy = require('task-strategy').Strategy

// create new strategy
var strategy = new Strategy(db, tactics, configs);

// it's very simple execute
strategy.on('progress', function() {
  strategy.position() === 0
    && console.log('End of the first tactics.')
  strategy.next();
}).on('error', function(){
  // rollback acts for backup datas and remove strategy session.
  strategy.rollback().on('error', function(e){
    console.log('fatal error occurs. rollback failed.', e);
  }).on('end', function(){
    console.log('strategy: ' + strategy._id + ' is rollback ended.');
  });
}).on('end', function(){
  // commit acts for remove strategy session and backup datas
  strategy.commit().on('error', function(e) {
    console.log('fatal error occurs. commit failed.', e);
  }).on('end', function(){
    console.log('strategy: ' + strategy._id + ' completed.');
  });
});

And you can check the task condition easily

strategy.get(function(tactics){
  console.log('Now executing tactics: ' + tactics.name());
});

API - creating queues

Query

q = gruntQ([options])

Arguments

options ( Number | Array | Object ) {q:1} optional
Options for creating queues.
If a Number or an Array is given, it treats as value of q

  • q (Number|Object|Array): statuses of queue(s) creating
    4 Create four queues with from rank 0 (lowest) to rank 3 (high)
    { maxQueue: 8 } Create a queue with rank 0, max queue count 8.
    [{}, { maxQueue: 4 }] A queue with rank 0, unlimited queue count and a queue with rank 1, max queue count 4 will be created.

  • maxWorker (Number|Boolean): max worker count for execute tasks. it is limited by the number of cpus. 2 two workers will be created if the number of cpus >= 2.
    true, null or undefined require('os').cpus() workers will be created.
    false not using child_process to execute task.

Events

A grunt-q is an instance of EventEmitter.

type ready
Emits when queue(s) are ready.

  q.on('ready', function(){ ... } );

type progress
Emits when progress to next task.

  q.on('progress', function(task_id, task){ ... } );

type error
Emits when some error occurs.

  q.on('error', function(err, [task]){ ... } );

Other events are bridged from grunt-runner as type data.
type data Emits when some error occurs.

  q.on('data', function(type, args){ ... } );

See readme for more information about other events.

API - enqueue a task

Query

q.enqueue([pkg_file_path,] task_configuration [, options][, callback]);

Note that you can .enqueue() without waiting event ready.
Before ready, tasks are waiting ready automatically.

Arguments

pkg_file_path ( String ) package.json optional
Specify the task package file. It's optional because it's not required that you take a time for writing package.json.

q.enqueue('package-for-task1.json', {(some configuration)});
/* contents of package-for-task1.json:
  { "name": "task1", "taskList": ["subtask1", "subtask2"] }
*/

or, you can write this alternatively

q.enqueue({
    pkg: {name: 'task1', taskList: ['subtask1', 'subtask2']}
  , (some configuration)
});
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