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.
Microservices With Ocelot API Gateway In ASP.NET Core

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 With Ocelot API Gateway In ASP.NET Core

Microservices Creation

Create a Blank Solution
Microservices With Ocelot API Gateway In ASP.NET Core
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
Microservices With Ocelot API Gateway In ASP.NET Core
-> 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
Microservices With Ocelot API Gateway In ASP.NET Core
Configuring the Ocelot API Gateway
This is how the Ocelot API Gateway Works in our project.
Microservices With Ocelot API Gateway In ASP.NET Core
To know about the Ocelot and its features go through this link Ocelot API Gateway
Install the package under the Gateway.WebAPI
  1. Install-Package Ocelot
Add Configuration settings in Startup.cs
Startup.cs
  1. using System;
  2. using System.Collections.Generic;
  3. using System.Linq;
  4. using System.Threading.Tasks;
  5. using Microsoft.AspNetCore.Builder;
  6. using Microsoft.AspNetCore.Hosting;
  7. using Microsoft.AspNetCore.Http;
  8. using Microsoft.Extensions.DependencyInjection;
  9. using Microsoft.Extensions.Hosting;
  10. using Ocelot.DependencyInjection;
  11. using Ocelot.Middleware;
  13. namespace Gateway.WebApi
  14. {
  15. public class Startup
  16. {
  17. // This method gets called by the runtime. Use this method to add services to the container.
  18. // For more information on how to configure your application, visit https://go.microsoft.com/fwlink/?LinkID=398940
  19. public void ConfigureServices(IServiceCollection services)
  20. {
  21. services.AddOcelot();
  22. }
  24. // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
  25. public async void Configure(IApplicationBuilder app, IWebHostEnvironment env)
  26. {
  27. if (env.IsDevelopment())
  28. {
  29. app.UseDeveloperExceptionPage();
  30. }
  31. app.UseRouting();
  32. app.UseEndpoints(endpoints =>
  33. {
  34. endpoints.MapControllers();
  35. });
  36. await app.UseOcelot();
  37. }
  38. }
  39. }
Create configuration.Json File under the Gateway.WebAPI to define the Routes which are necessary for Microservices.
configuration.Json
  1. {
  2. "Routes": [
  3. {
  4. "DownstreamPathTemplate": "/api/product",
  5. "DownstreamScheme": "https",
  6. "DownstreamHostAndPorts": [
  7. {
  8. "Host": "localhost",
  9. "Port": 44337
  10. }
  11. ],
  12. "UpstreamPathTemplate": "/gateway/product",
  13. "UpstreamHttpMethod": [ "POST", "PUT", "GET" ]
  14. },
  15. {
  16. "DownstreamPathTemplate": "/api/product/{id}",
  17. "DownstreamScheme": "https",
  18. "DownstreamHostAndPorts": [
  19. {
  20. "Host": "localhost",
  21. "Port": 44337
  22. }
  23. ],
  24. "UpstreamPathTemplate": "/gateway/product/{id}",
  25. "UpstreamHttpMethod": [ "GET", "DELETE" ]
  26. },
  27. {
  28. "DownstreamPathTemplate": "/api/customer",
  29. "DownstreamScheme": "https",
  30. "DownstreamHostAndPorts": [
  31. {
  32. "Host": "localhost",
  33. "Port": 44373
  34. }
  35. ],
  36. "UpstreamPathTemplate": "/gateway/customer",
  37. "UpstreamHttpMethod": [ "POST", "PUT", "GET" ]
  38. },
  39. {
  40. "DownstreamPathTemplate": "/api/customer/{id}",
  41. "DownstreamScheme": "https",
  42. "DownstreamHostAndPorts": [
  43. {
  44. "Host": "localhost",
  45. "Port": 44373
  46. }
  47. ],
  48. "UpstreamPathTemplate": "/gateway/customer/{id}",
  49. "UpstreamHttpMethod": [ "GET", "DELETE" ]
  50. }
  51. ],
  52. "GlobalConfiguration": {
  53. "BaseUrl": "http://localhost:44382"
  54. }
  56. }
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)
  1. {
  2. "iisSettings": {
  3. "windowsAuthentication": false,
  4. "anonymousAuthentication": true,
  5. "iisExpress": {
  6. "applicationUrl": "http://localhost:51733",
  7. "sslPort": 44382
  8. }
  9. },
  10. "profiles": {
  11. "IIS Express": {
  12. "commandName": "IISExpress",
  13. "launchBrowser": true,
  14. "environmentVariables": {
  15. "ASPNETCORE_ENVIRONMENT": "Development"
  16. }
  17. },
  18. "Gateway.WebApi": {
  19. "commandName": "Project",
  20. "launchBrowser": true,
  21. "applicationUrl": "https://localhost:5001;http://localhost:5000",
  22. "environmentVariables": {
  23. "ASPNETCORE_ENVIRONMENT": "Development"
  24. }
  25. }
  26. }
  27. }
Before testing the application make sure to run mutiple projects in a single go.
-> Right Click on solution
-> Click on properties
Microservices With Ocelot API Gateway In ASP.NET Core
Run the Project to check the results.
Output
Product Microservice - end point
Microservices With Ocelot API Gateway In ASP.NET Core
Customer Microservice - end point
Microservices With Ocelot API Gateway In ASP.NET Core
Note
I also implemented Swagger in this to check the result of individual Microservices.
I hope this article helps you!
Keep Learning!!!