Seneca microservice boilerplate

Boilerplate for developing microservice based architecture using Seneca.js.

Microservice design using Api Gateway

Requirements

node -v 10+

Why Seneca.js?

• Avoiding service coupling

If service A knows that it needs to send a message to service B, those services are coupled.

You want the flow to look like this:

Microservice A sends a message and does not know who gets it. B receives it but doesn't know who sent it. Now microservices are fully decoupled and you can deploy different versions of A and different versions of B.

Now we have another problem, Microservice A still needs to somehow find Microservice B.

We solve that by using seneca-mesh. Mesh uses swim algorithm for automatic service discovery.

• Pattern matching

This makes seenca super easy to use. You emit an event with a certain pattern and service that matches that pattern will pick it up.

• Composability of microservices

You can easily use 2 or more services together, to extend each other, to process data.

Api structure

Api gateway

• Api gateway using seneca and express. Maps rest api routes to seneca actions.
• You can use chairo and hapi.js for building api gateway. Chairo is a simple seneca plugin for hapi that maps api routes to seneca actions
• Api gateway holds authentication logic(to be added)

Routes.js folder contains routes separated into files(you can separate it according to your business logic, permissions etc.. depends on your needs) There you map each api rest route to seneca action.

Here you can see that we map /test route to seneca.add method that reacts to 'role:admin,cmd:test' pattern

'use strict'
const AdminRoutes =
    {
        pin: 'role:admin,cmd:*',
        map: {
          test: {
            GET: true,
            alias: '/test'
          }
    }

const AdminPlugin = function plugin (options) {
  const seneca = this;

  seneca.add('role:admin,cmd:test', (msg, done) => {
    this.act({role:'microservice',cmd:'promise'}, (err, msg) => {
      done(null, msg)
    })
  })
}

module.exports = {
    AdminRoutes,
    AdminPlugin
}

Microservice(using callbacks)

• Microservice is using seneca to recieve and emit events and react on api gateway sent events.

Note: Microservice is not obligated to communicate to Api gateway, services can also just communicate between each other.

How to use promises?

We can promisify seneca act method using promise library Bluebird.

const Promise = require('bluebird');
const act = Promise.promisify(seneca.act, {context: seneca});

act({role:'microservice',cmd:'test'})
  .then((msg) => {
    done(null, msg)
  })
  .catch((err) => {
    done(new Error('I have been rejected!'))
  })

You can refer to routes-with-promises.js to see promises in action.

Microservice(using MongoDB) - to be added

Microservices(using PostgreSQL) - to be added

Base

Base service contains base node. For a microservice to join a network, you do need to know where the base nodes are. Once you've joined, you don't even need the bases anymore, as the network keeps you informed of new services.

Local Development

We are using fuge. It provides an execution environment for developing microservice systems, eliminating shell hell and significantly reducing developer friction.

After you install fuge go into each directory and install dependencies

cd api-gateway
npm install

cd ../base
npm install

cd ../microservice
npm install

cd ../fuge
fuge shell

after fuge starts run

start all

and you can view all running services using fuge ps command