Real-Time Exchange Information With Microservices and NodeJs

Bora Kaşmer
May 17, 2020 · 12 min read

Today we will talk about real-time information used in all areas of social life. Speed ​​is the most important thing in the new technology century. In this article, we will try to informed customers who buy the stock papers when the price changed. It should be as fast and accurate as possible.

You can listen to the radio to get information about the exchange news once in a day like above the yellow taxi radio. But if you want to learn something in a real-time, you have to do more then this. You have to use technology. We will use “Socket.IO in this example.

“There is more to life than simply increasing its speed.”
― Mahatma Gandhi

But speed is not enough. Performance should also be. What is the performance of programming? Completing the job within a required time period. The user experiences are no interrupted or slowdown. How is this accomplished?

What Rome did is to divide a great system into several microsystems, thus diluting the entropy that can affect the great system by reducing it.
Divide and conquer…

This is a bronze statue of the first Roman emperor Caesar Augustus

How could we improve performance? If we separate some long processes, we keep customers waiting less while working. We will use Microservices for performance. Informing customers about the exchange of stock data is a very intense process. We will add to a Queue all inserted and updated stock data. We will use “RabbitMQ” for this application. We will write consumer microservice and get data from the queue and finally notify all customers with Socket.IO.

We will use NodeJs for the Backend.
Let’s create the first step of this new project:

Setup Before Starting Backend Application For Macbook :

  1. Firstly install NodeJs. We will use Socket.IO for real-time information service.
  2. Install Visual Studio Code: We will use VSCode for IDE. I love it. It is fast and straightforward.
  3. Install HomeBrew for installing RabbitMQ.
  4. brew install rabbitmq”: Install Rabbitmq. I will use RabbitMQ to queue the relevant data.
  5. “rabbitmq-server”: Run RabbitMQ.

If everything is ok, when you type “http://localhost:15672 from the browser and enter Username:” guest,” Password:” guest,” you have to see a screen like below the picture.

This is enough for the First Step :) Microservice Architecture is built on the simple working principle. But in fact, it is a combination of lots of complex pieces.

“Simplicity is the ultimate sophistication.”
-Leonardo Da Vinci

Now let’s create the first NodeJs Backend Service:

Lorem Ipsum Stock Data-DB

stockData.js: For not to distribute our focus, I will not get data from any database, like MsSql, Oracle, or MongoDB. So let’s create our static Lorem Ipsum Stock Data list.

RabbitMQ

npm install amqplib — save” : We have to install amqplib library for using RabbitMQ on NodeJs.

rabbitMQ.js: This is the queue in which the changed data will push to the clients.

1-) This function gets the channel name and updated stock data as a parameter..

rabbitMQ.js(1)

2-)This is the local path of RabbitMQ.

rabbitMQ.js(2)

3-)We are creating a channel on connected RabbitMQ.

rabbitMQ.js(3)

4-)Checks for “queueName (updateStock)” queue. If it doesn’t exist, then it creates one.

rabbitMQ.js(4)

5-)Put the stock data onto the “queueName (updateStock)” queue.

rabbitMQ.js(5)

NodeJS Service

service.js : This is our backend service. We send and update all stock data here. And we put modified stock data in a “updateStock” channel on RabbitMQ.

npm install express — save” : We will use the Express library on NodeJs for all HTTP requests.
npm install body-parser” : Parse incoming request bodies in a middleware before your handlers, available under the req.body property.
npm install — save cors” :It is used for allowing Cross-Origin. A client can get or post request from a browser to NodeJs service.

1-) This is the bodyParser library. It is available to get the updated stockData by req.body

service.js(1)

2-) This function is used for getting static Stock Data from the client. And all the data are sorted by the name.”localeCompare” is a javascript function. It is used for comparing two strings and returns a number indicating whether the string comes before, after, or is equal as the compare string in sort order.

service.js(2)

3-) When the administrator updates the properties of a stock, updated stock data from the client is posted to this “updatestockData” service as a parameter. “req.body,” is used for getting this parameter from the request. And finally, current stock data is updated with “findAndUpdateStock()” function. We will talk about it in the next item.

service.js(3)

4-) This function is used for finding and removing old data by the name from the static data list. Finally, updated data is added to the same list.

service.js(4)

5-) To informing the customers, updated data is put on the “updateStock” channel in RabbitMQ. Don’t forget to convert data to string with the “JSON.stringify()” function before putting it on the channel.

service.js(5)

6-) This NodeJs web service is published from 9480 port.

service.js(6)

“Microservices are a kind of asynchronous mechanism.
Nobody waits for the process to the end, and they always work at the behand of the scene.”
— Bora Kaşmer

Consumer

consumer.js: I compare the Consumer to a worker who works forever :) Consumer is an application or an instance that consumes messages. The same application can also publish messages and thus be a publisher at the same time. In this application, we will consume stock data from the “updateStock” channel, and at first, we will just press the stock’s name and value on to the screen. Later, we will notify this updated data to all clients.

1-)The ”io” is our custom Socket module. It is used for notifying the customers. “ampq” is a RabbitMQ library. It is used for pulling the updated data from the queue.

consumer.js(1)

2-) This function “amqp.connect()” is used for connect to local RabbitMQ serve.

consumer.js(2)

3-) This function is used for creating the “updateStock” channel, which we will take from stock data.

consumer.js(3)

4-) We declare a queue for consuming the data. “durable” means RabbitMQ saves the data on the memory as a default. But if we set “durable: true,” queues are persisted to disk. So If the server is taken down and then brought back up, the durable queue will be re-declared during server startup, however, only persistent messages will be recovered. Other On memory(durable: false) Queues will be lost.

consumer.js(4)

5-) This “channel.consume ()” function is to listen to the “updateStock” channel, get the updated stock data from the queue and send it to all customers in real-time using the Socket.IO service that we have not written yet.

noAck: true means, when the data is consumed, it will remove from the queue.
consumer.js(5)

io.socket.emit(“updatedStock”, stock) :

6-) This upper function is used for triggering the “updateStock” client-side function of all connected clients. And it sends them the updated stock data on Real-Time.

Socket.IO

socket.js: This module export a Socket Server. We will use it on Consumer. When the data is pulled from the queue, we will push it to all clients by using this Socket Server.

"npm install express socket.io --save": We need the Socket.IO library to inform the updated socket data to all clients.

1-) Io Socket Server needs a server, and the server needs an express library, so we declare all of them like seen belove the picture.

socket.js(1)

2-) When all the clients connect to Socket-IO, this “io-on(‘connecton’)” function will be triggered.

socket.js(2)

3-)When one of the clients is logout, this “socket, on (“disconnect”)” function will be triggered.

socket.js(3)

4-) Socket-IO and Consumer are published from 1923 port.

socket.js(4)
Image Source

Front-end Angular

Backend is finished. Let’s create the Front-End application. We will use Angular 9 for this application.

"npm i ngx-socket-io" : We need the ngx-socket-io library to get updated stock data and give real-time information to all clients.
"npm install bootstrap --save" : I use bootstrap for the css library.
Note: Add "style.css": @import "~bootstrap/dist/css/bootstrap.css";
Create Angular StockUI application with this command!

Model

stock.ts: Create stock model, which is monitoring by the clients.

export class Stock {
name: string;
value: number;
change: number;
percentage: number;
image:string;
}

Service

stockService.ts: It is used for getting and updating stock data from NodeJs. And It listens to the “updateStock” event to notify the client with real-time stock data.

1-) HttpClient and Socket libraries are injected into the “stockService” on the Constructor. It listens for the “updatestock” event and assigns the updated stock data to the “updateStock” variable when it comes from Socket.IO. When consumers received the updated stock data from the rabbitMQ, it will emit this to the client-side “updateStock” event.

stockService.ts(1)

2-)getStocks() function is used for getting all stock data from the NodeJs service. Return type Observer List of Stock. And if an error occurs, It tries to get the data one more time. More then 2 errors it calls “errorHandel()” function.

stockService.ts(2)

3-) It is used for error handling. You can send mail to the system desk or add as a document into an index of elastic-search.

stockService.ts(3)

AppComponent

app.component.ts:

1-)AppComponent is inherited from “AfterViewInit” because after the page is loaded, I want to get all stock data. The “ngAfterViewInit()” method provides this to me. It is like “Windows Form.OnLoad” method. And it comes from the AfterViewInit interface.

app.component.ts(1):

2-)This method is used for getting all stock data from the NodeJs service. It is an observer async method. After we got all data, we assigned all of them to the “stockList” Stock[] array.

The “image” column is only our view-model property. It is used for showing a green or red arrow icon on the page, which depends on the stock change value. There is no similar property in NodeJs service for this column.

app.component.ts(2):

3-)After the page is loaded, all stock data takes from the NodeJs service.

We declared the “updateStock” service, which is listening to the “updateStock” event. When update data come from the NodeJs service, we set the image property to depend on the change value of this stock data. And after all, we will remove the old one from our stockList and add an updated newest one to the same list.

app.component.ts(3):

Finally, I didn’t write any Admin page or UpdateService on Angular for updating stock data. Instead of this, I used “Postman.” I post stock data as above picture to “updateStockData()” NodeJs service.

Postman
Stock Monitoring Screen

app.component.html: I will iterate over the stocklist and render Html table row for every stock item on the screen.

<tbody>
<tr *ngFor="let stock of stockList">
<td>{{stock.name}}</td>
<td>{{stock.value}}</td>
<td>{{stock.change}}</td>
<td>{{stock.percentage}}</td>
<td><img src="../assets/images/{{stock.image}}.png" width="50px"></td>
</tr>
</tbody>

AppModule

app.modules.ts: All angular service, component, socket and module definitions are in this module.

1-) For using SocketIo on Angular, we need the “ngx-socket-io” library. And we have to define the Backend SocketIO HTTP server address as a config. In the end, we will use this config as a forRoot’s parameter during import this SocketIoModule.

app.modules(1)

2-)Forms module is used for model and form element-binding. HttpClient module is used for http.post and http.get request. SocketIoModule is used for Real-Time Communication between SocketIO and Angular.

app.modules(2)

The best couples share the load, divide the grief, and add to the peace, thereby multiplying joy.

— Matshona Dhliwayo

Music (Out At Sea)

Microservices are a way of breaking large software projects into loosely coupled modules that communicate with each other through simple Application Programming Interfaces. They are used to distribute the incoming load.

If you don’t have to wait for a process finished, you can imagine sperate it from the main process into the small application. What is the benefit of this? Of course, performance, less using resources, and working asynchronously. For example, in this application, Admin, who updated the stock data, doesn’t have to wait for all the client’s notification. He is only concerned with updating the database. So there is no reason to notify all clients at the main process. So we separated the Socket operation into the tiny Consumer application with RabbitMQ. We call it Microservice.

Image Source

Microservice is language Independent. If your team is a .Net Team, and this new guy is a python guy who came to your crew yesterday. Is this a problem for your business? If you are working with Microservices, it is not a problem. The new image processing module could be written using Python. And this new module will be developed independently, so compiling time will be reduced. He doesn’t have to compile other projects for running this image processing application.

Short Compile Time and Language Independent are some of the benefits of Microservices!

Microservice is not a silver bullet. Communication between services is not as simple as you think. You need many services to distribute the load. More services are equal to more resources. Handling the process gets harder with every new service.

Global testing could be soo hard when using microservices. Finding a problem could be like looking for a needle in a haystack. And the most important one is the deployment. If you have one hundred console applications, manually managing all of them is impossible. You have to Automated your deployments, tests, and scalability. But nowadays you are soo lucky there are a lot of toys for automating that. We call them cloud technology :)

Conclusion:

With this article, we learned how to handle loads by dividing them into small pieces. We call them Microservices and they work asynchronously. But Microservices is not a silver bullet. There a lot of disadvantages besides the advantages of Microservices. We saw the combined use of RabbitMQ, SocketIO, NodeJs, Consumer, and Angular technologies. You have to automate your test, deployment, management, replica, and more. So if you want to use Microservices, think twice and do once.

THE END & GOOD BYE

“If you have read so far, first of all, thank you for your patience and support. I welcome all of you to my blog for more!”

Source Code: Github
Source
: RabbitMQ, NodeJs, Socket.IO

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