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Ocelot .NET (How It Works For Developers)

Ocelot API Gateway is a .NET library that implements the API gateway pattern commonly used in API gateways to handle requests across multiple microservices. It acts as a lightweight API gateway, routing requests from clients to downstream services. This article provides an in-depth look at how the Ocelot API gateway sits between clients and downstream services, covering its installation, configuration, key features, and practical examples to demonstrate its capabilities. We'll also explore IronPDF Overview and Ocelot API combined.

What is Ocelot .NET?

Ocelot .NET (How It Works For Developers): Figure 1 - Ocelot .NET homepage

Ocelot is an open-source API gateway solution for .NET applications, designed to facilitate the routing of requests across multiple microservices. It acts as a reverse proxy, managing HTTP requests from clients and routing them to the appropriate services in an ASP.NET Core environment. Developed on ASP.NET Core, Ocelot integrates seamlessly with the .NET ecosystem, offering a robust set of features that are crucial for modern applications.

Key Features of Ocelot

Routing

At the core of Ocelot's functionality is its routing capability. It matches incoming requests to the appropriate service routes based on the configuration specified by developers, and it can be integrated with service discovery mechanisms. This includes support for wildcard routing, which is particularly useful when dealing with varying API versions or numerous service endpoints.

Middleware / Delegating Handlers

Ocelot allows developers to inject custom middleware or handlers that can process requests and responses before they reach the client or the service. This is useful for adding headers, logging requests, or even modifying the response structure as needed.

Load Balancing

Ocelot supports a variety of load-balancing strategies out of the box, such as Round Robin, Least Connection, and a custom provider if none of the predefined strategies fit the requirement. This feature ensures that the load is distributed evenly among the available services, enhancing the overall resilience and efficiency of the application.

Authentication and Authorization

Securing API endpoints is critical, and Ocelot provides support for integrating with existing authentication providers, such as Identity Server. It supports popular authentication schemes, including JWT and OAuth2, and allows for fine-grained control over user access to services.

Rate Limiting and QoS

Rate limiting is essential to prevent abuse and ensure fair use of the services by limiting the number of requests a user can make in a given period. Quality of Service (QoS) options like setting timeouts and retries ensure that services remain available and responsive under various network conditions and loads.

Setting Up Ocelot in a .NET Project

To integrate Ocelot into your project, you need to install the Ocelot package via NuGet and configure it in the Program class:

dotnet add package Ocelot

Ocelot .NET (How It Works For Developers): Figure 2 - Install Ocelot .NET through NuGet Package Manager

Configure the services, including the request builder middleware, in your Startup.cs or Program.cs class to set up the service container:

public void ConfigureServices(IServiceCollection services)
{
    // Add Ocelot services to the service collection
    services.AddOcelot();
}

public async void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
    // Use the developer exception page when in development mode
    if (env.IsDevelopment())
    {
        app.UseDeveloperExceptionPage();
    }

    // Start Ocelot middleware
    await app.UseOcelot();
}
public void ConfigureServices(IServiceCollection services)
{
    // Add Ocelot services to the service collection
    services.AddOcelot();
}

public async void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
    // Use the developer exception page when in development mode
    if (env.IsDevelopment())
    {
        app.UseDeveloperExceptionPage();
    }

    // Start Ocelot middleware
    await app.UseOcelot();
}
Public Sub ConfigureServices(ByVal services As IServiceCollection)
	' Add Ocelot services to the service collection
	services.AddOcelot()
End Sub

Public Async Sub Configure(ByVal app As IApplicationBuilder, ByVal env As IWebHostEnvironment)
	' Use the developer exception page when in development mode
	If env.IsDevelopment() Then
		app.UseDeveloperExceptionPage()
	End If

	' Start Ocelot middleware
	Await app.UseOcelot()
End Sub
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Configuring Routes in Ocelot

Ocelot uses a configuration file, typically ocelot.json, to define the routing rules. Here is a more complex example that demonstrates multiple route configurations:

{
    "ReRoutes": [
        {
            "DownstreamPathTemplate": "/api/users/{id}",
            "DownstreamScheme": "https",
            "DownstreamHostAndPorts": [
                {
                    "Host": "userapi.com",
                    "Port": 443
                }
            ],
            "UpstreamPathTemplate": "/users/{id}",
            "UpstreamHttpMethod": ["Get"]
        },
        {
            "DownstreamPathTemplate": "/api/products/{id}",
            "DownstreamScheme": "https",
            "DownstreamHostAndPorts": [
                {
                    "Host": "productapi.com",
                    "Port": 443
                }
            ],
            "UpstreamPathTemplate": "/products/{id}",
            "UpstreamHttpMethod": ["Get"]
        }
    ],
    "GlobalConfiguration": {
        "BaseUrl": "http://yourgateway.com"
    }
}

This configuration specifies how requests to the API gateway are routed to different downstream services based on the path and HTTP method, using the JSON file for setup.

Using IronPDF with Ocelot .NET

Ocelot .NET (How It Works For Developers): Figure 3 - IronPDF homepage

Combining Ocelot with IronPDF's HTML-to-PDF Conversion in a .NET application provides a powerful solution where you can route PDF generation requests to a specific service or handle them internally. Here, I'll guide you through setting up a basic .NET Core application that uses Ocelot as an API Gateway and IronPDF to generate PDFs from HTML.

IronPDF excels in HTML to PDF conversion, ensuring precise preservation of original layouts and styles. It's perfect for creating PDFs from web-based content such as reports, invoices, and documentation. With support for HTML files, URLs, and raw HTML strings, IronPDF easily produces high-quality PDF documents.

using IronPdf;

class Program
{
    static void Main(string[] args)
    {
        var renderer = new ChromePdfRenderer();

        // Convert HTML string to PDF
        var htmlContent = "<h1>Hello, IronPDF!</h1><p>This is a PDF from an HTML string.</p>";
        var pdfFromHtmlString = renderer.RenderHtmlAsPdf(htmlContent);
        pdfFromHtmlString.SaveAs("HTMLStringToPDF.pdf");

        // Convert HTML file to PDF
        var htmlFilePath = "path_to_your_html_file.html"; // Specify the path to your HTML file
        var pdfFromHtmlFile = renderer.RenderHtmlFileAsPdf(htmlFilePath);
        pdfFromHtmlFile.SaveAs("HTMLFileToPDF.pdf");

        // Convert URL to PDF
        var url = "http://ironpdf.com"; // Specify the URL
        var pdfFromUrl = renderer.RenderUrlAsPdf(url);
        pdfFromUrl.SaveAs("URLToPDF.pdf");
    }
}
using IronPdf;

class Program
{
    static void Main(string[] args)
    {
        var renderer = new ChromePdfRenderer();

        // Convert HTML string to PDF
        var htmlContent = "<h1>Hello, IronPDF!</h1><p>This is a PDF from an HTML string.</p>";
        var pdfFromHtmlString = renderer.RenderHtmlAsPdf(htmlContent);
        pdfFromHtmlString.SaveAs("HTMLStringToPDF.pdf");

        // Convert HTML file to PDF
        var htmlFilePath = "path_to_your_html_file.html"; // Specify the path to your HTML file
        var pdfFromHtmlFile = renderer.RenderHtmlFileAsPdf(htmlFilePath);
        pdfFromHtmlFile.SaveAs("HTMLFileToPDF.pdf");

        // Convert URL to PDF
        var url = "http://ironpdf.com"; // Specify the URL
        var pdfFromUrl = renderer.RenderUrlAsPdf(url);
        pdfFromUrl.SaveAs("URLToPDF.pdf");
    }
}
Imports IronPdf

Friend Class Program
	Shared Sub Main(ByVal args() As String)
		Dim renderer = New ChromePdfRenderer()

		' Convert HTML string to PDF
		Dim htmlContent = "<h1>Hello, IronPDF!</h1><p>This is a PDF from an HTML string.</p>"
		Dim pdfFromHtmlString = renderer.RenderHtmlAsPdf(htmlContent)
		pdfFromHtmlString.SaveAs("HTMLStringToPDF.pdf")

		' Convert HTML file to PDF
		Dim htmlFilePath = "path_to_your_html_file.html" ' Specify the path to your HTML file
		Dim pdfFromHtmlFile = renderer.RenderHtmlFileAsPdf(htmlFilePath)
		pdfFromHtmlFile.SaveAs("HTMLFileToPDF.pdf")

		' Convert URL to PDF
		Dim url = "http://ironpdf.com" ' Specify the URL
		Dim pdfFromUrl = renderer.RenderUrlAsPdf(url)
		pdfFromUrl.SaveAs("URLToPDF.pdf")
	End Sub
End Class
$vbLabelText   $csharpLabel

Step 1: Set Up the .NET Core Web Application

First, create a new .NET Core Web API project. You can do this using the .NET CLI or Visual Studio.

Using the .NET CLI:

dotnet new webapi -n OcelotWithIronPDF
cd OcelotWithIronPDF
dotnet new webapi -n OcelotWithIronPDF
cd OcelotWithIronPDF
SHELL

Step 2: Add Necessary Packages

You need to install Ocelot and IronPDF. You can add these packages via NuGet.

dotnet add package Ocelot
dotnet add package IronPdf
dotnet add package Ocelot
dotnet add package IronPdf
SHELL

Step 3: Configure Ocelot

Add an ocelot.json file to the root of your project with the following content to configure Ocelot’s routing. This setup assumes you want Ocelot to route PDF generation requests to a specific path that will be handled by IronPDF within the same application.

{
    "ReRoutes": [
        {
            "DownstreamPathTemplate": "/api/pdf",
            "DownstreamScheme": "https",
            "DownstreamHostAndPorts": [
                {
                    "Host": "localhost",
                    "Port": 5001
                }
            ],
            "UpstreamPathTemplate": "/generatepdf",
            "UpstreamHttpMethod": ["Post"]
        }
    ],
    "GlobalConfiguration": {
        "BaseUrl": "http://localhost:5000"
    }
}

Step 4: Configure Startup.cs

Update Startup.cs to include Ocelot’s middleware. Ensure you also configure your application to use static files, as IronPDF may need to load assets from the local file system.

public class Startup
{
    public void ConfigureServices(IServiceCollection services)
    {
        services.AddControllers();
        services.AddOcelot();
    }

    public async void Configure(IApplicationBuilder app, IWebHostEnvironment env)
    {
        if (env.IsDevelopment())
        {
            app.UseDeveloperExceptionPage();
        }

        app.UseRouting();
        app.UseAuthorization();

        app.UseEndpoints(endpoints =>
        {
            endpoints.MapControllers();
        });

        await app.UseOcelot();
    }
}
public class Startup
{
    public void ConfigureServices(IServiceCollection services)
    {
        services.AddControllers();
        services.AddOcelot();
    }

    public async void Configure(IApplicationBuilder app, IWebHostEnvironment env)
    {
        if (env.IsDevelopment())
        {
            app.UseDeveloperExceptionPage();
        }

        app.UseRouting();
        app.UseAuthorization();

        app.UseEndpoints(endpoints =>
        {
            endpoints.MapControllers();
        });

        await app.UseOcelot();
    }
}
Public Class Startup
	Public Sub ConfigureServices(ByVal services As IServiceCollection)
		services.AddControllers()
		services.AddOcelot()
	End Sub

	Public Async Sub Configure(ByVal app As IApplicationBuilder, ByVal env As IWebHostEnvironment)
		If env.IsDevelopment() Then
			app.UseDeveloperExceptionPage()
		End If

		app.UseRouting()
		app.UseAuthorization()

		app.UseEndpoints(Sub(endpoints)
			endpoints.MapControllers()
		End Sub)

		Await app.UseOcelot()
	End Sub
End Class
$vbLabelText   $csharpLabel

Step 5: Implement PDF Generation with IronPDF

Create a new controller PdfController.cs in your Controllers folder. This controller will handle the PDF generation requests.

using Microsoft.AspNetCore.Mvc;
using IronPdf;

namespace OcelotWithIronPDF.Controllers
{
    [ApiController]
    [Route("api/[controller]")]
    public class PdfController : ControllerBase
    {
        [HttpPost]
        public IActionResult CreatePdfFromHtml([FromBody] string htmlContent)
        {
            var renderer = new ChromePdfRenderer();
            var pdf = renderer.RenderHtmlAsPdf(htmlContent);
            var output = pdf.BinaryData;

            // Return the PDF as a file result
            return File(output, "application/pdf", "generated.pdf");
        }
    }
}
using Microsoft.AspNetCore.Mvc;
using IronPdf;

namespace OcelotWithIronPDF.Controllers
{
    [ApiController]
    [Route("api/[controller]")]
    public class PdfController : ControllerBase
    {
        [HttpPost]
        public IActionResult CreatePdfFromHtml([FromBody] string htmlContent)
        {
            var renderer = new ChromePdfRenderer();
            var pdf = renderer.RenderHtmlAsPdf(htmlContent);
            var output = pdf.BinaryData;

            // Return the PDF as a file result
            return File(output, "application/pdf", "generated.pdf");
        }
    }
}
Imports Microsoft.AspNetCore.Mvc
Imports IronPdf

Namespace OcelotWithIronPDF.Controllers
	<ApiController>
	<Route("api/[controller]")>
	Public Class PdfController
		Inherits ControllerBase

		<HttpPost>
		Public Function CreatePdfFromHtml(<FromBody> ByVal htmlContent As String) As IActionResult
			Dim renderer = New ChromePdfRenderer()
			Dim pdf = renderer.RenderHtmlAsPdf(htmlContent)
			Dim output = pdf.BinaryData

			' Return the PDF as a file result
			Return File(output, "application/pdf", "generated.pdf")
		End Function
	End Class
End Namespace
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Step 6: Run the Application

Make sure your application is correctly configured to listen on the ports specified in ocelot.json. You can set this in Properties/launchSettings.json.

{
  "profiles": {
    "OcelotWithIronPDF": {
      "commandName": "Project",
      "launchBrowser": false,
      "applicationUrl": "https://localhost:5001;http://localhost:5000",
      "environmentVariables": {
        "ASPNETCORE_ENVIRONMENT": "Development"
      }
    }
  }
}

Now, run your application, and you should be able to post HTML content to http://localhost:5000/generatepdf and receive a PDF in response.

Ocelot .NET (How It Works For Developers): Figure 4

This example showcases a basic implementation of Ocelot with IronPDF within the same application. For production scenarios, consider securing your endpoints, handling error scenarios, and optimizing the PDF generation process based on your specific requirements.

Conclusion

Ocelot .NET (How It Works For Developers): Figure 5 - IronPDF licensing page

In conclusion, Ocelot is an excellent choice for managing and routing requests in a microservices architecture. Its robust features like routing, load balancing, middleware support, and authentication make it a powerful tool for any .NET developer. By following the detailed steps provided, you can effectively integrate Ocleot into your .NET projects to streamline your API Gateway needs.

Additionally, if you require PDF generation capabilities, integrating IronPDF with Ocelot is straightforward and enhances your application's functionality. IronPDF offers a free trial and licenses start from a cost-effective solution for your PDF needs.

By leveraging Ocelot and IronPDF together, you can build a comprehensive and efficient microservices infrastructure that meets both routing and document generation requirements.

Frequently Asked Questions

How can Ocelot improve microservices communication in .NET applications?

Ocelot acts as an API gateway, facilitating efficient routing and management of HTTP requests across multiple microservices in a .NET application. It provides features like routing, load balancing, and authentication to streamline communication between services.

What are the benefits of using Ocelot with IronPDF?

Integrating Ocelot with IronPDF allows developers to efficiently route PDF generation requests within a .NET application. IronPDF ensures that HTML-to-PDF conversions maintain original layouts and styles, making it ideal for generating web-based content such as reports and invoices.

How do you configure Ocelot for load balancing?

Ocelot supports various load-balancing strategies, including Round Robin and Least Connection, which can be configured via a JSON file typically named ocelot.json. This ensures even distribution of traffic across microservices.

What role does middleware play in Ocelot's architecture?

Middleware in Ocelot allows developers to insert custom handlers to process requests and responses. This is useful for tasks such as adding headers, logging, or modifying responses, enhancing the flexibility and functionality of the API gateway.

How can you set up Ocelot in a .NET project?

To set up Ocelot in a .NET project, install the Ocelot package via NuGet, then configure it by adding Ocelot services in the Program class and defining routes in a configuration file. This setup facilitates routing and management of API requests.

What strategies does Ocelot use to handle routing?

Ocelot uses configuration-driven routing, specified in a ocelot.json file, to direct requests from the API gateway to appropriate downstream services. It supports wildcard routing and service discovery mechanisms for flexible routing setups.

How does Ocelot ensure secure API access?

Ocelot integrates with authentication providers like Identity Server and supports JWT and OAuth2 schemes, allowing for secure API access by controlling user permissions and ensuring endpoint protection.

Can Ocelot be used to optimize PDF generation workflows?

Yes, Ocelot can route requests to specific services dedicated to PDF generation, such as those using IronPDF. This setup optimizes PDF workflows by efficiently handling requests and preserving document fidelity during conversion.

How does Ocelot integrate with service discovery mechanisms?

Ocelot supports integration with service discovery mechanisms like Consul and Eureka, which allows it to dynamically route requests based on the current state of services. This integration simplifies managing services in a microservices architecture.

Chipego
Software Engineer
Chipego has a natural skill for listening that helps him to comprehend customer issues, and offer intelligent solutions. He joined the Iron Software team in 2023, after studying a Bachelor of Science in Information Technology. IronPDF and IronOCR are the two products Chipego has been focusing on, but his knowledge of ...Read More