Hemera-controlplane package

This is a plugin to scale your workers remotly with Hemera. This package allows you to react dynamically to load requirements. Each worker has its own memory, with their own V8 instance. If you scale a worker inside a docker container ensure that you docker host has enough memory. The maximal number of workers is restricted to the processor count of the host machine.

Status: Experimental

• Create easy multiple workers of your hemera service
• When parent worker exit all child workers will exit
• online and exit status are guaranteed via IPC
• Receive further events e.g when a worker exists fast after it was successfully created

Run tests

$ node ./test/worker
$ npm run test

Start your worker

'use strict'

const Hemera = require('nats-hemera')
const nats = require('nats').connect()
const HemeraControlPlane = require('hemera-controlplane')
const HemeraJoi = require('hemera-joi')

const hemera = new Hemera(nats, {
  logLevel: 'debug'
})

hemera.use(HemeraJoi)
hemera.use(HemeraControlPlane, {
  service: 'math'
})

hemera.ready(() => {
  hemera.add({
    topic: 'math',
    cmd: 'add'
  }, (req, cb) => {
    cb(null, req.a + req.b)
  })
})

Scale your worker

'use strict'

const Hemera = require('nats-hemera')
const nats = require('nats').connect()

const hemera = new Hemera(nats, {
  logLevel: 'debug'
})

hemera.ready(() => {
  hemera.act({
    topic: 'controlplane',
    cmd: 'scaleUp',
    service: 'math',
    maxMessages$: 2 // receive further error events when the creation of the worker fails
  }, (err, req) => {
    hemera.log.info(req, 'Result') // {"success":true,"pid":5500}
  })
})

Scale your worker down

'use strict'

const Hemera = require('nats-hemera')
const nats = require('nats').connect()

const hemera = new Hemera(nats, {
  logLevel: 'debug'
})

hemera.ready(() => {
  hemera.act({
    topic: 'controlplane',
    cmd: 'scaleDown',
    service: 'math',
    maxMessages$: 2 // receive further error events when the killing of the worker fails
  }, (err, req) => {
    hemera.log.info(req, 'Result') // {"success":true,"pid":5500}
  })
})

Kill all workers but keep the parent process

'use strict'

const Hemera = require('nats-hemera')
const nats = require('nats').connect()

const hemera = new Hemera(nats, {
  logLevel: 'debug'
})

hemera.ready(() => {
  hemera.act({
    topic: 'controlplane',
    cmd: 'down',
    service: 'math'
  }, (err, req) => {
    hemera.log.info(req, 'Result') // {"success":true}
  })
})

Exit a worker by PID

'use strict'

const Hemera = require('nats-hemera')
const nats = require('nats').connect()

const hemera = new Hemera(nats, {
  logLevel: 'debug'
})

hemera.ready(() => {
  hemera.act({
    topic: 'controlplane',
    cmd: 'killByPid',
    service: 'math',
    pid: 1,
    maxMessages$: 2 // receive further error events when killing of the worker fails
  }, (err, req) => {
    hemera.log.info(req, 'Result') // {"success":true}
  })
})

Get list of all running workers

'use strict'

const Hemera = require('nats-hemera')
const nats = require('nats').connect()

const hemera = new Hemera(nats, {
  logLevel: 'debug'
})

hemera.ready(() => {
  hemera.act({
    topic: 'controlplane',
    cmd: 'list',
    service: 'math'
  }, (err, req) => {
    hemera.log.info(req, 'Result') // {"success":true, list: [5500]}
  })
})

TODO

• [X] Use IPC to guarantee that process was started or exited.
• [ ] Add more tests