Relieve

The goal of this library is to ease the implementation of multi processing accross your existing microservices. Relieve aims to give a reusable design pattern using process forks. It also eases communication with child processes with an high-level abstraction.

For example, with a CallableTask:

//task.js
//just export a module in the child process
module.exports = {
  print: (str) => {
    console.log(str)
  },
  data: () => {
    //return some async data
    return Promise.resolve({foo: 'bar'})
  }
}

Then from your master, just call the task:

//worker.js
var CallableTask = require('relieve/tasks/CallableTask')
var task = new CallableTask('task.js')

task.start()
.then(() => {
  task.call('print', 'hello world')
  return task.get('data')
})
.then(d => {
  //d is {foo: 'bar'}
})

The design pattern

Relieve is based on a design pattern containing:

• A Worker
• One or more tasks

The task can be used without a Worker, but the Worker helps managing workflows.

Task

The task will implement a child process using fork. It'll make sure that there is an ipc channel open so that Workers and Tasks can communicate. There are different tasks implementations:

• Fork Task - simply transforms a ChildProcess.fork in a Task
• Script Task - wraps a script path in a container that is managed through ChildProcess.fork. It gives the ability to start, restart or kill a Task
• Callable Task - this is a Script Task with convenience methods to call or get script methods remotely

Tutorials:

• Fork Task
• Script Task
• Callable Task

Worker

Different kind of Workers for different use cases. Every Worker takes one or more tasks and handles them.

• Worker - it's a basic worker. Helps sending a message to every task.
• QueueWorker - process tasks one after the other, or in concurrency. Waits for a Task to exit before it consider's it as done.
• CloudWorker - does not wait for tasks to exit and process them through a Strategy (ie: RoundRobin)

Tutorials:

• Worker
• QueueWorker
• CloudWorker

Tools

• Containers - easy way to add ipc methods for your tasks
• Interfaces - extends how the tasks are managed (FailSafe, Logger)

Links

• Documentation
• Coverage
• Blog post