Practical Microservices with Dapr and .NET

Introducing Dapr

Welcome to this second edition of Practical Microservices with Dapr and .NET! Distributed Application Runtime (Dapr) evolved greatly after the version one release and the innovations in .NET 6 prompted a refreshed and enriched edition of the book.

This chapter will introduce you to the Dapr project to teach you the core concepts of its architecture and prepare you to develop with Dapr.

Dapr accelerates the development of new cloud-native applications and simplifies the adoption of a microservice architecture.

In this chapter, we are going to cover the following main topics:

Understanding Dapr
Exploring Dapr
Setting up Dapr
Building our first Dapr sample

Learning about these topics is important to establish a solid foundation for our future endeavors with Dapr and microservice architectures. These basic concepts will guide our learning throughout the rest of this book.

Our first steps into the project will start with exploring Dapr and understanding how it works.

Understanding Dapr

Dapr is an event-driven, portable runtime created by Microsoft with an open source approach and it is a Cloud Native Computing Foundation (CNCF) incubated project.

Being event-driven (which is emphasized in the definition of Dapr) plays an important role in microservices; this is because an application can be designed to efficiently react to events from external systems or other parts of the solution and to produce events as well in order to inform other services of new facts or to continue processing elsewhere, or at a later stage.

Dapr is portable as it can run locally on your development machine in self-hosted mode; it can also be deployed to the edge, or it can run on Kubernetes.

The following diagram shows the many building blocks provided by Dapr:

Figure 1.1 – Dapr architecture

Portability does also extend beyond the hosting environment—while Dapr is an initiative that was started by Microsoft, it can also run on Kubernetes on-premises or in the cloud with Microsoft Azure, Amazon Web Services (AWS), Google Cloud Platform (GCP), or any other cloud vendor.

Dapr has been built on the experience gained by Microsoft in developing hyperscale cloud-native applications. It has been inspired by the design of Orleans and Service Fabric, which in turn enables many Microsoft Azure cloud services to operate resiliently and at a large scale.

A brief history of Dapr

Dapr was first released in October 2019, and you can find more information at https://cloudblogs.microsoft.com/opensource/2019/10/16/announcing-dapr-open-source-project-build-microservice-applications/.

Dapr adopted an open governance model early on in the initial development phase in September 2020; see the description at https://blog.dapr.io/posts/2020/09/30/transitioning-the-dapr-project-to-open-governance/.

Dapr reached the production-ready v1.0 release in February 2021; see https://blog.dapr.io/posts/2021/02/17/announcing-dapr-v1.0/ for more details. In November 2021, Dapr joined CNCF as an incubated project; see the announcement at https://blog.dapr.io/posts/2021/11/03/dapr-joins-cncf-as-an-incubating-project/.

Dapr offers developers an approach to design the tools to build and the runtime to operate applications, based on a microservice architecture style.

Microservices offer a vast array of benefits balanced by increased complexities in team and product management, usually with a significant burden on the developer and the team in order to get started.

What if you could leverage a runtime such as Dapr to help you get through the common patterns you will likely need to adopt, and thus ease your operations?

The following figure shows the two Dapr hosting modes:

Figure 1.2 – Dapr sidecar

As depicted in Figure 1.2, the Dapr runtime operates in sidecar processes, lifting most of the complexity from the application to a separate environment, greatly simplifying development and operations as well. These sidecar processes are run locally in your development environment or as containers in a Pod on Kubernetes.

From an application perspective, Dapr is an Application Programming Interface (API) that can be directly reached via HyperText Transfer Protocol (HTTP), Remote Procedure Call (gRPC) calls, or, even more simply, via any of the Software Development Kits (SDKs) available for .NET, Java, Go, Python, PHP, JavaScript, C++, and Rust languages.

As we will experience later, it is not necessary to adopt the Dapr SDK in your application; a request to a Dapr service can be as simple as an HTTP call to an endpoint, such as http://localhost:3500/v1.0/invoke/<app-id>/method/<methodname>. Nevertheless, using the SDK does provide many benefits if you are writing a Dapr service adopting the server extensions, interacting with Dapr via the client SDK, or leveraging the Dapr actor model with the Actor SDK.

You can learn more about SDKs and the supported languages in the Dapr docs at https://docs.dapr.io/developing-applications/sdks/.

Now that we have learned about the high-level architecture of Dapr, it is time to also clarify what D apr is not.

What Dapr is not

While we hope the overview of Dapr has informed and intrigued you enough to spend time on this book, when we have the chance to talk about Dapr, we often find ourselves in need of clarifying what Dapr is not. This makes it easier to eliminate any misconceptions we may have about what Dapr does, as follows:

Dapr does not force the developer to embrace a programming model with strict rules and constraints. On the contrary, while the application developer is freed, by Dapr, of the many complexities of a microservice architecture, the developer is not mandated on how to write the application. As an example, the management of the connection to the database where the state is stored is a responsibility of Dapr and, as we will see in the following chapters, it is transparent to the microservice application code.
Dapr is not a service mesh. While many similarities can be found in the general objectives of Dapr and service meshes, Dapr does provide these benefits at the application level, while a service mesh operates on the infrastructure. For instance, it is the developer’s responsibility to decide how to handle errors Dapr might return if there is a conflict or an intermittent issue; whether it is adopting a retry policy as provided by the Dapr resiliency configurations, raising an error back to the client, or compensating the operation, these are explicit choices only the developer can make.

Dapr is designed to be integrated with service meshes such as Istio, which is out of the scope of this book.

Dapr is not a Microsoft cloud service. It does help the developer build microservice applications in the cloud, and it surely provides many integrations with Azure cloud services, but it also has as many components for AWS, GCP, and other services. At the same time, Azure does offer rich support to Dapr in Azure Kubernetes Service (AKS) with the native extension, in Azure API Management with Dapr policies, and in Azure Container Apps with Dapr native integration.
Dapr is not a .NET only technology. Dapr itself has been written in the Go language and any language can leverage it. SDKs for many languages are available but you can also choose to interact directly with the Dapr API without any additional library.

Important note

While this book is heavily skewed toward .NET, Dapr does provide the same benefits to Python developers (just as an example) as it provides SDKs for Dapr and Dapr Actor, with Kubernetes as the deployment target—Dapr welcomes all developers in a vendor-neutral and open approach.

We hope this perspective on the Dapr objectives and role will help you in properly adopting this technology. The next section will be dedicated to understanding the archi tecture of Dapr.

Exploring Dapr

Dapr has been designed from the ground up as a set of pluggable building blocks—developers can create an application counting on the support of many facilities, while operators can adapt applications to the hosting environment by simply intervening in the configuration.

The following is a complete list of the tools and components of Dapr:

The Dapr command-line interface (CLI): A cross-platform command-line tool to configure, manage, and monitor the Dapr environment. It is also the tool used to locally debug Dapr applications.
Dapr Helm charts: It is worth mentioning that Helm charts are provided for a richer experience in installing and updating Dapr in a Kubernetes environment.
The Dapr API: The API that defines how an application can interact with the Dapr runtime in order to leverage its building blocks.
The Dapr runtime: This is the core of Dapr that implements the API. If you are curious, you can take a look at how it is developed in Go at Dapr’s repository at https://github.com/dapr/dapr.
The Dapr host: On your development machine, the host runs as a standalone process; in Kubernetes, it is a sidecar container in your application’s pod.
The Dapr operator: Specific to Kubernetes mode, the operator manages bindings and configurations.
The Dapr sidecar injector: Once instructed via configuration in Kubernetes mode, this takes care of injecting the Dapr sidecar into your application pod.
The Dapr placement service: This service has the objective of distributing (or placing) Actor instances across the Dapr pods.
Dapr Sentry: A built-in Certificate Authority (CA) to issue and manage certificates used by Dapr to provide transparent mutual Transport Layer Security (mTLS).

Dapr provides several building blocks that microservice application developers can adopt selectively, based on their needs, and they are as follows:

Service invocation: Service-to-service invocation enables your code to call other services located in the same hosting environment while taking care of the retry policy.

This building block is presented in more detail in Chapter 4, Service-to-Service Invocation.

State management: This is to efficiently manage the application state as a simple Key-Value Pair (KVP), relieving your stateful or stateless services of the need to support different backends. Dapr provides many state stores, which include Redis, Azure Cosmos DB, Azure SQL Server, and PostgreSQL, which can be plugged in via configuration.

You can learn about this building block in Chapter 5, Introducing State Management.

Publish and subscribe (pub/sub) messaging: The pub/sub pattern enables decoupled communication between microservices by exchanging messages, counting on the presence of a service bus, which can route messages between producers and consumers.

A discussion of this building block is presented in Chapter 6, Publish and Subscribe.

Resource bindings: This is where the event-driven nature of Dapr shines. With bindings, your application can be triggered by a Short Message Service (SMS) message sent via Twilio (just one of the popular services in the area of communication API).

This building block is presented in more detail in Chapter 7, Resource Bindings.

Actors: The actor pattern aims to simplify highly concurrent scenarios by splitting the overall request load between a large number of computation units (the actors), which take care of the job in their smaller, but independent, scope by processing requests to a single actor one at a time. Dapr provides great benefits in this space.

You can learn about this building block in Chapter 8, Using Actors.

Observability: Dapr enables the developer and operator to observe the behavior of the system services and applications without having to instrument them.

This building block is presented in more detail in Chapter 11, Tracing Dapr Applications.

Secrets: It is a healthy practice to keep secrets segregated from the code. Dapr enables you to store secrets and to reference these from other components, in Kubernetes or Azure Key Vault, among many options.
Configuration: Introduced in Dapr version 1.8 in Alpha state, this building block addresses the common need to retrieve the configuration data needed by an application.
Distributed lock: Introduced with Dapr version 1.8 in Alpha state, it provides a powerful lease-based mechanism to manage mutually exclusive access to a named lock. The lock can be used by the application to assure exclusive access to a resource by many concurrent instances.

After learning about Dapr architecture and components, and before we can start using them, we need to set up Dapr in our development environment, which wil l be the topic of the next section.

Building our first Dapr sample

It is time to see Dapr in action. We are going to build a web API that returns a hello world message. We chose to base all our samples in the C:\Repos\practical-dapr\ folder, and we created a C:\Repos\practical-dapr\chapter01 folder for this first sample. We’ll take the following steps:

Let’s start by creating a Web API ASP.NET project as follows:

PS C:\Repos\practical-dapr\chapter01> dotnet new webapi

-o dapr.microservice.webapi

Then, we add the reference to the Dapr SDK for ASP.NET. The current version is 1.5.0. You can look for the package versions on NuGet at https://www.nuget.org/packages/Dapr.Actors.AspNetCore with the dotnet add package command, as illustrated in the following code snippet:
```
PS C:\Repos\practical-dapr\chapter01> dotnet add package
```
```
Dapr.AspNetCore --version 1.8.0
```
We need to apply some changes to the template we used to create the project. These are going to be much easier to do via VS Code—with the <directory>\code . command, we open it in the scope of the project folder.
To support Dapr in ASP.NET 6 and leverage minimal hosting and global usings, we made a few changes to the code in Program.cs. We changed the builder.Services.AddControllers() method to builder.Services.AddControllers().AddDapr().

We also added app.MapSubscribeHandler(). While this is not necessary for our sample, as we will not use the pub/sub features of Dapr, it is better to have it in mind as the base set of changes you need to apply to a default ASP.NET project.

Finally, in order to simplify the code, we commented app.UseHttpsRedirection().

The following is the modified code of the Program.cs class:

var builder = WebApplication.CreateBuilder(args);
// Add services to the container.
builder.Services.AddControllers().AddDapr();
// Learn more about configuring Swagger/OpenAPI at https://aka.ms/aspnetcore/swashbuckle
builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen();
var app = builder.Build();
// Configure the HTTP request pipeline.
if (app.Environment.IsDevelopment())
{
    app.UseSwagger();
    app.UseSwaggerUI();
}
//app.UseHttpsRedirection();
app.UseAuthorization();
app.MapControllers();
app.MapSubscribeHandler();
app.Run();

In the preceding code block, we instructed Dapr to leverage the Model-View-Controller (MVC) pattern in ASP.NET 6.

Finally, we added a controller named HelloWorldController as illustrated in the following code snippet:

using Microsoft.AspNetCore.Mvc;

namespace dapr.microservice.webapi.Controllers;

[ApiController]

[Route("[controller]")]

public class HelloController : ControllerBase

    private readonly ILogger<HelloController> _logger;

    public HelloController(ILogger<HelloController>

      logger)

        _logger = logger;

    [HttpGet()]

    public ActionResult<string> Get()

        Console.WriteLine("Hello, World.");

        return "Hello, World";

In the preceding code snippet, you can see [Route] and [HttpGet]. These ASP.NET attributes are evaluated by the routing to identify the method name.

In order to run a Dapr application, you use the following command structure:

dapr run --app-id <your app id> --app-port <port of the

application> --dapr-http-port <port in Dapr> dotnet run

We left the ASP.NET default port as 5000 but we changed the Dapr HTTP port to 5010. The following command line launches the Dapr application:

PS C:\Repos\practical-dapr\chapter01\dapr.microservice.
webapi> dapr run --app-id hello-world --app-port 5000
--dapr-http-port 5010 dotnet run
Starting Dapr with id hello-world. HTTP Port: 5010. gRPC
Port: 52443

The initial message informs you that Dapr is going to use port 5010 for HTTP as specified, while for gRPC, it is going to auto-select an available port.

The log from Dapr is full of information. To confirm your application is running correctly in the context of the Dapr runtime, you can look for the following code:

Updating metadata for app command: dotnet run
You're up and running! Both Dapr and your app logs will
appear here.

At this stage, ASP.NET is responding locally on port 5000 and Dapr is responding on port 5010. In order to test Dapr, let’s invoke a curl command as follows, and using the browser is equally fine:

PS C:\Repos\practical-dapr\chapter01> curl http://
localhost:5010/v1.0/invoke/hello-world/method/hello
Hello, World

This exciting response has been returned by Dapr, which passed our (the client’s) initial request to the ASP.NET Web API framework. You should also see that the same result logged as Console.WriteLine sends its output to the Dapr window as follows:

== APP == Hello, World.

From another window, let’s verify our Dapr service details. Instead of using the dapr list command, let’s open the Dapr dashboard as follows:
```
PS C:\Windows\System32> dapr dashboard
```
```
Dapr Dashboard running on http://localhost:8080
```

We can open the dashboard by navigating to http://localhost:8080 to reveal the following screen:

Figure 1.3 – Dapr dashboard application

The Dapr dashboard shown in Figure 1.3 illustrates the details of our hello-world application.

In this case, the Dapr dashboard shows only this sample application we are running on the development machine. In a Kubernetes environment, it would show all the microservices running, along with the other components.

The Dapr dashboard also displays the configured components in the hosting environment, as we can see in the following screenshot:

Figure 1.4 – Dapr dashboard components

In Figure 1.4, the Dapr dashboard shows us that the local installation of Redis is configured as state store and pub/sub components, in addition to the deployment of Zipkin.

This ends our introductory section, where we were able to build our first Dapr sample.

Practical Microservices with Dapr and .NET: A developer's guide to building cloud-native applications using the event-driven runtime , Second Edition

What do you get with Print?

Practical Microservices with Dapr and .NET

Introducing Dapr

Technical requirements

Understanding Dapr

What Dapr is not

Exploring Dapr

Setting up Dapr

Docker

Intalling the Dapr CLI

Installing .NET

Installing VS Code

The Dapr extension

Installing Windows Terminal

Installing Dapr in self-hosted mode

Installing Dapr on Kubernetes

Updating Dapr version

Building our first Dapr sample

Summary

Questions

Further reading

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