Forkify

Forkify lets you run functions in a forked child process

Install

$ npm install forkify

Features

• Distribute executions over multiple instances
• Create new instances when existing ones are too busy
• Buffers & streams are sent over a separate socket to bypass costly JSON serialization
• Idle instances are reaped (by default after 30 seconds)
• Events can be emitted from the fork

Todo

• You should also be able to send events to the fork
• Emitted event arguments should be serialized through the same process as a function execution or callback, so buffers & streams can also be emitted

Examples

Forkify a function

var forkify = require('forkify');
 
// Forkify the function
var fibonacci = forkify(function generateFibonacci(amount, callback) {
    var fib = [],
        res,
        i;
 
    fib[0] = 0;
    fib[1] = 1;
 
    for (i = 2; i <= amount; i++) {
        res = fib[0] + fib[1];
 
        fib[0] = fib[1];
        fib[1] = res;
    }
 
    // Callback with the response
    callback(null, res);
});
 
fibonacci(10, function gotResult(err, result) {
    console.log('Fibonacci result:', err, result);
});

Work with buffers

You can pass Buffer instances back and forth, without problems. These are not serialized using JSON, as that is a costly affair. Unfortunately, they are also not using "shared memory", rather the buffer contents are sent to the child over an extra stream.

 
var workWithBuffers = forkify(function(buffer, callback) {
 
    // Outputs 6 in this case
    console.log(buffer.length);
 
    callback(null, new Buffer(40));
});
 
workWithBuffers(new Buffer(6), function(err, buffer) {
    // Outputs 40 in this case
    console.log(buffer.length);
});

Set instance pool size

By default, up to 3 instances are created. This can be modified at any time like this:

forkify.limit = 5;

Create a new forkify pool

If you want to create a separate pool, you can do so like this:

var forkify2 = forkify.constructor();

Set minimum idle time before reaping

Forks are killed after idling for at least 30 seconds. This can be changed by setting the idle property:

forkify.idle = 45000; // 45 seconds

Do note: For now, the reaping function only runs once every 10 seconds.

Caveats

forkify functions run in a new scope and can not access anything outside of it, you will have to re-require modules you wish to use inside the function.

Arguments passed to the forkified function are converted using a modified version of JSON-DRY (which supports Dates, Infinity, Errors, Buffers, ...)

Because of the addition of Buffer support forkify will keep your application running until all instances have been reaped.

License

MIT