seneca-cqrs-example.js

seneca-cqrs-example.js

'use strict'

var seneca = require('seneca')

function eventStore () {

  // This is the acid part, if this stores correctly all events are
  // emitted, if not you die because you are in an invalid state. this
  // whole part is usually based on optimistic concurrency.
  seneca.add('role:eventStore,cmd:update', functiom (msg, done) {

    // Assuming our save went well for each event, we publish them
    // for readmodels or anyone else to listen to.
    msg.events.forEach((event) => {
      seneca.act(event, {fatal$: false})
    })
  })
}


function productHandler () {

  // In seneca these parts are your agreggates.
  senea.add('role:product,cmd:create', function (msg, done) {

    // create product would create the events needed based on
    // the message provided and may create multiple messages.
    createProduct(msg, (events) => {
      // forward all events on to the store, we don't need a response.
      this.act('role:eventStore,cmd:update', {events: events})
      done()
    })

  })
}

function productReadModel () {
  // We want all events related to product.
  seneca.add('role:product,event:*', function (msg, done) {
    // add products to some run time cache
    done()
  })

  // Give people the data we have, it will be eventually consistent.
  seneca.add('role:product,query:listAll', function (msg, done) {
    done(null, {data: {...}})
  })
}



// Send a command once per second, commands are fire and forget.
setTimeout(() => {
  seneca.act('role:product,cmd:create', {name: 'apple'})
}, 1000)


// Query a read-model, these are populated via the event stream
setTimeout(() => {
  seneca.act('role:product,query:listAll', (err, reply) => {
    console.log(err || reply.data)
  })
}, 1200)