NodeJs

Install Node.js

If you’ve never worked with Node.js before, kick off with installing the npm manager: nodejs.org/en/download/package-manager

Install NPM and Express Framework

In addition to npm, our application will use the Express Framework, one of the most popular Node.js frameworks. Create a new directory and initialize npm:

$ mkdir helloworld 
$ cd helloworld
$ npm init

When asked for the details of the application (name, version, etc.), just confirm the default values with enter.

Npm will create a package.json that will hold the dependencies of the app. Let’s add the Express Framework as the first dependency:

$ npm install express --save

The file should look like this now:

{
  "name": "helloworld",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "",
  "license": "ISC",
  "dependencies": {
    "express": "^4.15.2"
  }
}

Details of Hello World

With everything installed, we can create an index.js file with a simple HTTP server that will serve our Hello World website:

//Load express module with `require` directive
var express = require('express')
var app = express()

//Define request response in root URL (/)
app.get('/', function (req, res) {
  res.send('Hello World!')
})

//Launch listening server on port 8081
app.listen(8081, function () {
  console.log('app listening on port 8081!')
})

Run the app

The application is ready to launch:

$ node index.js

Go to http://localhost:8081/ in your browser to view it.

Express Microservice Starter

https://www.npmjs.com/package/express-microservice-starter

An express-based bootstrapping module for building microservices with Node.js. The starter utilises sub-app mounting to provide any implementing express application with a variety of functionality.

Key Features

The starter provides the following features out of the box;

• CORS support
• Cache-Control header support
• Body-parsing support
• Configurable controller/route auto-scanning
• Configurable health monitors
• Configurable per-application logging
• Automatic service registration with ZooKeeper
• Actuator info and health endpoints (/info and /health)
• Partial Response Powered by express-partial-response
• Request correlation id support (res.locals.correlationId and req.log Bunyan child logging also provided)

Basic Usage

The following is the most basic usage of the starter, for a more detailed example please refer to the example directory;

'use strict';
 
var express = require('express');
var micro   = require('express-microservice-starter');
 
var app = express();
 
app.use(micro({ discoverable: false, debug: true }));
 
app.listen(8000, function onListen() {
  log.info('Microservice initialised and accepting requests at the following root: http://localhost:8000/starter/v1');
});
 
app.on('service:registered', function(data) {
  log.info('service registered with zookeeper', data);
  log.info('microservice registration data is also available as an app.locals property', app.locals.microservice);
});

Configuration

By placing an app.yml config file in the /config directory of an implementing app it is possible to override default options.

default:
 
  #
  # Basic
  #
  server:
    port: 8000
 
  #
  # Log
  #
  log:
    path: my-log-file.log
 
  #
  # Microservice
  #
  microservice:
    basePath: services
    server:
      name: starter/v1
      dependencies: my/other/service/to/monitor/v1
      registrationNetworkInterfacePriority: 
        - en0
        - lo0
 
  #
  # Zookeeper
  #
  zookeeper:
    connectionString: localhost:2181
    retry:
      wait: 1000
      count: 5

In the above example the application would be accessible at the following address: http://0.0.0.0:8000/starter/v1, with the /actuator/info and /actuator/health diagnostic endpoints activated.

Note: the registrationNetworkInterfacePriority property allows the selection of the network interface when dynamically registering a service with ZooKeeper.

Note: if registrationNetworkInterfacePriority doesn't work for you, you can set ADVERTISED_HOST and ADVERTISED_PORT environment variable.

If you would like to override the version which is exposed in the /info endpoint, just set the VERSION node env variable.

VERSION=1.0.1 node index.js

API

app.use(micro([options]));

options is an optional argument which can overwrite the defaults. It can take the following properties;

• debug: boolean Activate finer grained logging.
• discoverable: boolean Register the service with Zookeeper to allow for discovery by other services connecting to the same instance of Zookeeper.
• controllersPath: String Path to load controllers. Defaults to controllers.
• monitorsPath: String Path to load monitors. Defaults to monitors.
• partialResponseQuery: String The query parameter to use for partial reponse. Defaults to fields.
• correlationHeaderName: String The name of your correlation header. Defaults to X-CorrelationID.
• validatorOptions: object Enable express-validator with these options. Defaults to null.
• enableBodyParsing: boolean Enable or disable body parsing, useful to disable when dealing with content other than JSON. Enables express-validator. Defaults to true.
• enableEtag: boolean Activate etag. Defaults to false.
• enableRequestTracing: boolean Enabled request log trace. Defaults to false.

SWAGGER Integration

Supports binding of route handlers using a swagger specification document via the options.swaggerConfig object.

app.js

'use strict';
 
var express = require('express');
var micro   = require('express-microservice-starter');
 
var app = express();
 
var options = {
  swaggerConfig: {
    filePath: `/swagger.yml`, // path to swagger specification file
    controllers: `lib/controllers` // path to controllers directory
  }
};
 
app.use(micro(options));
 
//  to register application specific exception handlers wait until the
//  'swagger:routes:registered' event is emitted.
app.once('swagger:routes:registered', () => {
 
  app.use(function (err, req, res, next) {
  
    if (err) {
      res.status(418).json({
        name: 'Teapot',
        message: 'Always wanted to use this...'
      });
    }
  });
});
 
app.listen(8000, function onListen() {
  log.info('Microservice initialised and accepting requests at the following root: http://localhost:8000/starter/v1');
});

swagger.yml

swagger: "2.0"
info:
  version: 1.0.0
  title: "API specification"
  description: API specification
basePath: /v1
schemes:
  - http
consumes:
  - application/json
produces:
  - application/json
paths:
  /users:
    x-swagger-router-controller: users # lib/controllers/users 
    get:
      description: Return a list of users
      operationId: find
      responses:
        200:
          description: User Response
          schema:
            type: array
            items:
              $ref: '#/definitions/User'
        default:
          description: Standard Error Response
          schema:
            $ref: '#/definitions/Error'
 
  /users/{uuid}:
    x-swagger-router-controller: users # lib/controllers/users 
    get:
      description: Return a user based on the provided uuid
      operationId: get
      parameters:
        - name: uuid
          in: path
          description: UUID of the user to return
          required: true
          type: integer
          format: int64
      responses:
        200:
          description: Item Response
          schema:
            $ref: '#/definitions/User'
        default:
          description: Standard Error Response
          schema:
            $ref: '#/definitions/Error'
 
 
definitions:
  User:
    required:
      - uuid
      - name
      - status
      - created
    properties:
      uuid:
        type: string
      name:
        type: string
      status:
        type: string
        enum:
          - active
          - inactive
      created:
          type: string
          format: date-time

lib/controllers/users.js

'use strict';
 
const user = {
  uuid: '1234567890',
  name: 'User One',
  status: 'active',
  created: new Date('2000-01-01')
};
 
exports.find = function find (req, res, next) {
 
  try {
    res.json([user]);
  }
  catch (e) {
    next(e);
  }
}
 
exports.get = function get (req, res, next) {
 
  try {
    res.json(user);
  }
  catch (e) {
    next(e);
  }
}

Keywords

express, zookeeper, microservicestarter, zoologist