Microservices With Ocelot API Gateway In ASP.NET Core

Introduction

 

Today we are going to learn about Microservice architecture and its implementation using Ocelot API Gateway in ASp.Net Core - 3.1. We all know the benifits of using Microservices for large scale applications. 

 

Microservice Architecture - Overview

 

There are two possible ways to build and structure the applications:

1. Monolith Architecture
2. Microservices Architecture 

Monolith Architecture

 

Monolith is like a big container, wherein all the software components of an app are assembled and tightly coupled; i.e each component fully depends on each other. There are advantages and disadvantages in Monolith. Compared to Microservices the advantages are less in Monolith Architecture.

 

 

Disadvantage

 

Slow Development

 

If we modify any module or any component we need to redeploy the whole application instead of updating  part of it. It consumes more time in slow development.

 

Unreliable

 

If one service goes down then the entire application stops working because all the services of the application are connected to each other.

 

Large and Complex Applications

 

For large scale applications it is difficult for maintenance because they are dependent on each other.

 

It consumes more memory where each component will access the whole data and it makes more memory consumption and also  rebuilds the application. In addition to that we need to change the whole application and  it makes the process a bit diffcult.

 

Microservices Architecture

 

Microservices Architecture refers to a technique that gives modern developers a way to design highly scalable, flexible applications by decomposing the application into discrete services that implement specific business functions. These services, often referred to as "Loosely Coupled," can be built, deployed and scaled independently.

 

The following picture is from Microsoft Docs which shows the microservices architecture style. 

 

 

Microservices Creation

 

Create a Blank Solution

 

 

Create a New Solution Folder with the name as Microservices

 

     ->  Right Click on Microservices Folder

     ->  Click on Add

     ->  Click on New Project

 

Create a Customer Microservice

 

     

-> Enter the project name 

-> Choose API as template and we are going with .Net Core 3.1 Version.

-> Click on Create

 

Create the Product Microservice

 

  - > Follow the same process as we did for Customer Microservice.

 

Create the API Gateway 

 

-> Choose Empty as template with the same .Net Core 3.1 Version.

 

Folder Structure

 

 

Configuring the Ocelot API Gateway

 

This is how the Ocelot API Gateway Works in our project.

 

 

To know about the Ocelot and its features go through this link Ocelot API Gateway

 

Install the package under the Gateway.WebAPI

Install-Package Ocelot

Add Configuration settings in Startup.cs

 

Startup.cs 

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Ocelot.DependencyInjection;
using Ocelot.Middleware;

namespace Gateway.WebApi
{
    public class Startup
    {
        // This method gets called by the runtime. Use this method to add services to the container.
        // For more information on how to configure your application, visit https://go.microsoft.com/fwlink/?LinkID=398940
public void ConfigureServices(IServiceCollection services)
{
    services.AddOcelot();
}

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
public async void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
    if (env.IsDevelopment())
    {
        app.UseDeveloperExceptionPage();
    }
    app.UseRouting();
    app.UseEndpoints(endpoints =>
    {
        endpoints.MapControllers();
    });
    await app.UseOcelot();
}
    }
}

Create configuration.Json File under the Gateway.WebAPI to define the Routes which are necessary for Microservices.

 

configuration.Json

{
  "Routes": [
    {
      "DownstreamPathTemplate": "/api/product",
      "DownstreamScheme": "https",
      "DownstreamHostAndPorts": [
        {
          "Host": "localhost",
          "Port": 44337
        }
      ],
      "UpstreamPathTemplate": "/gateway/product",
      "UpstreamHttpMethod": [ "POST", "PUT", "GET" ]
    },
    {
      "DownstreamPathTemplate": "/api/product/{id}",
      "DownstreamScheme": "https",
      "DownstreamHostAndPorts": [
        {
          "Host": "localhost",
          "Port": 44337
        }
      ],
      "UpstreamPathTemplate": "/gateway/product/{id}",
      "UpstreamHttpMethod": [ "GET", "DELETE" ]
    },
    {
      "DownstreamPathTemplate": "/api/customer",
      "DownstreamScheme": "https",
      "DownstreamHostAndPorts": [
        {
          "Host": "localhost",
          "Port": 44373
        }
      ],
      "UpstreamPathTemplate": "/gateway/customer",
      "UpstreamHttpMethod": [ "POST", "PUT", "GET" ]
    },
    {
      "DownstreamPathTemplate": "/api/customer/{id}",
      "DownstreamScheme": "https",
      "DownstreamHostAndPorts": [
        {
          "Host": "localhost",
          "Port": 44373
        }
      ],
      "UpstreamPathTemplate": "/gateway/customer/{id}",
      "UpstreamHttpMethod": [ "GET", "DELETE" ]
    }
  ],
  "GlobalConfiguration": {
    "BaseUrl": "http://localhost:44382"
  }

}

DownstreampathTemplate -  Defines the route of actual endpoint of Microservice

 

DownstreamScheme - scheme of Microservice, HTTPS 

 

DownstreamHostsandPorts - Host and Port of Microservice will define here.

 

UpstreampathTemplate - The path at which the client will request the Ocelot API Gateway

 

UpstreamHttpmethod - The Supported HTTP Methods to the API Gateway. Based on the incoming method,Ocelot sends a  similar HTTP method request to microservices as well.

 

Let's test the application and this will run under the Gateway.WebAPI Port number which we already defined in the configuration.json file

 

launchsettings.json (Gateway API)

{
  "iisSettings": {
    "windowsAuthentication": false,
    "anonymousAuthentication": true,
    "iisExpress": {
      "applicationUrl": "http://localhost:51733",
      "sslPort": 44382
    }
  },
  "profiles": {
    "IIS Express": {
      "commandName": "IISExpress",
      "launchBrowser": true,
      "environmentVariables": {
        "ASPNETCORE_ENVIRONMENT": "Development"
      }
    },
    "Gateway.WebApi": {
      "commandName": "Project",
      "launchBrowser": true,
      "applicationUrl": "https://localhost:5001;http://localhost:5000",
      "environmentVariables": {
        "ASPNETCORE_ENVIRONMENT": "Development"
      }
    }
  }
}

Before testing the application make sure to run mutiple projects in a single go.

 

 -> Right Click on solution

-> Click on properties

 

 

Run the Project to check the results.

 

Output

 

Product Microservice - end point 

 

Customer Microservice - end point  

 

Note 

I also implemented Swagger in this to check the result of individual Microservices.

• GitHub Source

I hope this article helps you!

 

Keep Learning!!!