paratask-promises
v4.0.1
Published
Paratask is a tool that will execute your Back-end JavaScript code in parallel using the full potential of multi-process programming. In contrast to asynchronous task management, Paratask will create a child Node/io.js process.
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Paratask - Node Parallel Process Manager
Paratask is a tool that will execute your code in parallel using the full potential of multi-process programming. In contrast to asynchronous task management, Paratask will create a child Node/io.js process in which your task function will 'live'.
Note: Scope dependency injection is at your service. More into in the examples below.
Note: This modules embraces the Promises/A+ standard. If you're more into ES5 "callback" style you can use paratask
Install
You can install Paratask Promises/A+ with the Node Package Manager:
npm install paratask-promises
or by getting it from this repo.
Dependencies
Paratask uses only native Node/io.js modules that do not need additional installation: fs
and child_process
.
Custom Promise lib
You like to use your own Promise constructor or 3rd party alternative? No problem, just type:
var paratask = require('paratask-promises');
paratask.usePromise( require('bluebird').Promise );
// or
paratask.usePromise( require('q').Promise );
// or
paratask.usePromise( require('when').Promise );
// or
paratask.usePromise( require('rsvp').Promise );
Thanks to machinewu for the great suggestion.
Example: Parallel calculation
Both task_1
and task_2
will fork a new Node/io.js process and will run concurrently.
When both call resolve()
, the final results will be printed in the console.
Note: scope
property is your dependency injector. Can only be a valid JSON.parse()
value (i.e. no functions allowed).
var paratask = require('paratask-promises');
var task_1 = {
fork: function (resolve) {
// Some calculation using the 'count' scope var
var result = count * 10;
resolve(result);
},
scope: {
count: 10
}
};
var task_2 = {
fork: function (resolve) {
// Some calculation using the 'count' scope var
var result = count * 10;
resolve(result);
},
scope: {
count: 20
}
};
paratask([ task_1, task_2 ])
.then(function (results) {
console.log( results ); // [100, 200], 1st task result will be always the 1st in the results array even if completed last
});
Example: Error handling
Both task_1
and task_2
will fork a new process but
when task_2
call reject('Error message')
both processes will be killed and the final .then()
will be executed.
Note: scope
property is optional.
var paratask = require('paratask-promises');
var task_1 = {
fork: function (resolve) {
var count = 100000;
var factorial = 1;
while (--count) factorial *= count;
resolve(factorial);
}
};
var task_2 = {
fork: function (resolve, reject) {
reject('Error message');
}
};
paratask([ task_1, task_2 ])
.catch(function (error) {
console.log( error ); // 'Error message'
});
Comparison tests
A palette of comparison tests between paratask()
, async.parallel()
, and process.nextTick()
are available in ./tests
folder.
Heavy calculation test:
node tests/async_heavy_test.js
node tests/process_nextTick_heavy_test.js
node tests/paratask_heavy_test.js
Conclusion
Paratask is great when you have several time consuming task functions with few external dependencies. In such cases, multi-processing is the best approach. When you want to manage several relevantly quick functions with asynchronous logic, async will handle it with beauty.