Welcome to this second edition ofPractical 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.

The code for this sample can be found on GitHub at https://github.com/PacktPublishing/Practical-Microservices-with-Dapr-and-.NET-Second-Edition/tree/main/chapter01.

In this chapter, the working area for scripts and code is expected to be<repository path>\chapter01\. In our local environment, it isC:\Repos\practical-dapr\chapter01.

Please refer to theSetting up Dapr section for a complete guide to the tools needed to develop with Dapr and work with the samples.

Dapr is anevent-driven, portable runtime createdby Microsoft with an open source approach and it is aCloud 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 doesalso extend beyond the hosting environment—while Dapris an initiative that was started by Microsoft, it canalso run on Kubernetes on-premises or in the cloud withMicrosoft 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, whichin turn enables many Microsoft Azure cloud services to operate resiliently and at a large scale.

A brief history of Dapr

Dapr was first released inOctober 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 inFigure 1.2, theDapr runtime operates in sidecar processes, lifting most of the complexity from the application to a separate environment, greatly simplifying developmentand operations as well. These sidecar processes are run locally in your development environment or as containers in a Pod on Kubernetes.

From anapplication perspective, Dapr is anApplication Programming Interface (API) that can be directly reached viaHyperText Transfer Protocol (HTTP),Remote Procedure Call (gRPC)calls, or, evenmore simply, via any of theSoftware Development Kits (SDKs) availablefor .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 ashttp://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 learnmore about SDKs and the supported languages in the Dapr docs athttps://docs.dapr.io/developing-applications/sdks/.

Now thatwe have learned about the high-level architecture of Dapr, it is time to also clarify what Dapr 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 needof clarifying what Dapr isnot. This makes it easier to eliminate any misconceptions we may have about what Dapr does, as follows:

• Dapr doesnot 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 isnot 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 isnot a Microsoft cloud service. It does help the developer build microservice applications in the cloud, and it surely provides many integrations with Azurecloud services, but it also has as many components forAWS, GCP, and other services. At thesame time, Azure does offer rich support to Dapr inAzure Kubernetes Service (AKS) with the native extension, inAzure API Management with Dapr policies, and inAzure Container Apps with Dapr native integration.
• Dapr isnot a .NET only technology. Dapr itself has been written in the Go language and anylanguage 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 architecture of Dapr.

Dapr has beendesigned 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 followingis a complete list of the tools and components of Dapr:

• The Dapr command-line interface (CLI): A cross-platform command-line tool toconfigure, manage, and monitor the Dapr environment. It is also the tool used to locally debug Dapr applications.
• Dapr Helm charts: It is worthmentioning that Helm charts are provided for a richer experience in installing and updating Dapr in a Kubernetes environment.
• The Dapr API: The API thatdefines how an application can interact with the Dapr runtime in order to leverage its building blocks.
• The Dapr runtime: This is thecore 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 yourdevelopment machine, the host runs as a standalone process; in Kubernetes, it is a sidecar container in your application’s pod.
• The Dapr operator: Specificto Kubernetes mode, the operator manages bindings and configurations.
• The Dapr sidecar injector: Once instructed via configuration in Kubernetes mode, thistakes care ofinjecting the Dapr sidecar into your application pod.
• The Dapr placement service: Thisservice has the objective of distributing (or placing) Actor instances across the Dapr pods.
• Dapr Sentry: Abuilt-inCertificate Authority (CA) to issueand manage certificates usedby Dapr to provide transparentmutual 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 otherservices located in the same hosting environment while taking care of the retry policy.

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

• State management: This is to efficiently manage the application state as a simpleKey-Value Pair (KVP), relieving your stateful or stateless services of the need tosupport 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 inChapter 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 betweenproducers and consumers.

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

• Resource bindings: This is where the event-driven nature of Dapr shines. With bindings, yourapplication can be triggered by aShort 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 inChapter 7,ResourceBindings.

• 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 inChapter 8,Using Actors.

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

This building block is presented in more detail inChapter 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 powerfullease-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 will be the topic of the next section.

Dapr is a runtime for every platform and every language. The focus of this book is on C# in .NET, used withVisual Studio Code (VS Code). The code snippets in the book can be appreciatedby developers from anybackground, but nevertheless, you will get the most out of it from a .NET perspective.

The development environment we use is Windows, as you will be able to tell from the screenshots we use in the book. While the CLI, configuration, and files will be the same, if you need more details on how to perform a particularaction on Linux or a macOS developmentmachine, we encourage you to check the Dapr documentation at https://docs.dapr.io/.

Dapr roadmap

The Dapr runtime reached the v1.0 production-ready release in February 2021, as announced in the Dapr blog at https://blog.dapr.io/posts/2021/02/17/announcing-dapr-v1.0/, and five new minor versions have been released during 2021. You can learnmore about the Dapr roadmap athttps://docs.dapr.io/contributing/roadmap/.

The samples and scripts in this book have been updated and tested with v1.8 of Dapr.

In this book, we will also leverage several services on the Azure cloud platform (https://azure.microsoft.com/en-us/explore/), whether as a platform to execute Dapr applications, for exchanging messages via Azure, or for storing data.

Access to an Azure subscription is required. Each chapter will give you instructions and directyou to documentation for further information.

Next, we will accomplish the following steps:

• Configuring Docker
• Installing the Dapr CLI
• Installing .NET
• Installing VS Code
• Installing Windows Terminal
• Installing Dapr in self-hosted mode
• Installing Dapr on Kubernetes

Let’s start with Docker.

Docker

Dapr requires Docker tobe present locally in your development environment; therefore, make sure you have it installed. If your development machine is Windows, Docker must be running in Linux container mode.

You canfind detailed instructions for running Docker at https://docs.docker.com/install/.

Intalling the Dapr CLI

We will immediatelystart working with Dapr; therefore, you need to installall the necessary tools. The Dapr runtime and its tools can be found athttps://github.com/dapr/cli.

On Windows, execute the following command to install the CLI in thec:/dapr directory and add it to the userPATH environment variable so that the tools can be easily found from the command line:

powershell -Command "iwr -useb https://raw.githubusercontent.com/dapr/cli/master/install/install.ps1 | iex"

For more details on the Dapr CLI, please refer to https://docs.dapr.io/getting-started/install-dapr-cli/.

We still need to initialize Dapr on the development machine, which we will do in theInstalling Dapr in self-hosted mode section of this chapter.

Installing .NET

To install .NET 6, pleaserefer to https://dotnet.microsoft.com/download forthe link to the latest binaries.

.NET 6 isaLong-Term Support (LTS) version of .NET, which getsfree support and patches for3 years. Refer to https://dotnet.microsoft.com/en-us/platform/support/policy for more details on the .NET support policy.

On a development machine, it makes sense to install the full SDK, which includes the runtime. Once the install is complete, open a new command prompt and run thedotnet --info command. You should see the following output:

PS C:\Repos\dapr-samples\chapter01> dotnet --info.NET SDK (reflecting any global.json): Version:   6.0.101 Commit:    ef49f6213aRuntime Environment: OS Name:     Windows OS Version:  10.0.22000 OS Platform: Windows RID:         win10-x64 Base Path:   C:\Program Files\dotnet\sdk\6.0.101\Host (useful for support):  Version: 6.0.1  Commit:  3a25a7f1cc …

This proves that .NET hasbeen recognized and the framework is workingfine.

Installing VS Code

VS Code is agreat multiplatformsource code editor by Microsoft. You caninstall it for free by following the instructions at https://code.visualstudio.com/docs/setup/windows.

The Dapr extension

Dapr has an extension for VS Code that helps with navigating the Dapr local environmentand eases the debuggingconfiguration—we highlyrecommend it. Please follow the instructions at https://docs.dapr.io/developing-applications/ides/vscode/.

Installing Windows Terminal

We really lovethe new Windows Terminal (https://aka.ms/terminal) for its ease of use and configurability. In thefollowing chapters, we will often have to runmultiple commands and tools in parallel. Therefore, the tabs feature of Windows Terminal is just one of the reasons why we suggest you adopt it too.

Installing Dapr in self-hosted mode

Dapr can beinitialized intwo modes:self-hosted (or standalone) andKubernetes.

As it is intended to be used for a development environment, the self-hosted mode locally installs Redis, the Dapr placement services, and Zipkin. The following command initializes Dapr in your local environment:

dapr init

The Dapr binaries and default components to leverage Redis are by default positioned in the%USERPROFILE%\.dapr\ folder.

In a local development environment, it might happen that the ports Dapr might intend to use for Redis, for example, are already in use. In this case, you should identify which processes or containers are using the ports and change them accordingly.

Once you launch theinit command, the following is the output you should expect:

PS C:\Repos\practical-dapr\chapter01> dapr initMaking the jump to hyperspace...Installing runtime version 1.8.4Downloading binaries and setting up components...Downloaded binaries and completed components set up.daprd binary has been installed to C:\Users\dabedin\.dapr\bin.dapr_placement container is running.dapr_redis container is running.dapr_zipkin container is running.Use `docker ps` to check running containers.Success! Dapr is up and running. To get started, go here: https://aka.ms/dapr-getting-started

To check your newly initialized Dapr environment, you can usedocker ps as follows:

PS C:\Repos\practical-dapr\chapter01> docker ps --format "{{.Image}} - {{.Ports}} - {{.Names}}"daprio/dapr:1.8.4 - 0.0.0.0:6050->50005/tcp, :::6050->50005/tcp- dapr_placementopenzipkin/zipkin - 9410/tcp, 0.0.0.0:9411->9411/tcp, :::9411->9411/tcp - dapr_zipkinredis - 0.0.0.0:6379->6379/tcp, :::6379->6379/tcp - dapr_redis

The outputshows the Dockercontainer for Dapr running on our machine.

Installing Dapr on Kubernetes

Dapr is specificallyintended to be executed on Kubernetes. From your development machine on which youhave the Dapr CLI installed, you can set up Dapr on the Kubernetes cluster currently configured as follows:

dapr init -k

Alternatively, you can install Dapr on Kubernetes with a Helm v3 chart. You can find more details at https://docs.dapr.io/getting-started/install-dapr-kubernetes/#install-with-helm-advanced.

Important note

If you intend to define aContinuous Integration/Continuous Deployment (CI/CD) pipeline that takes care of the Dapr installation on the Kubernetes cluster too, this canalso work, although it is out of scope for the present setup.

To verify theinstallation was successfully completed, execute thefollowing command:

kubectl get pods --namespace dapr-system

The command should display the pods in thedapr-system namespace.

Updating Dapr version

On a developmentWindows machine on which a previous version of Dapr was already present, the CLI can be updated by simply re-installing with the command we saw in a previous section.

As described in https://docs.dapr.io/operations/hosting/self-hosted/self-hosted-upgrade/, on a Windows development machine on which a previous version of Dapr was already present, you must uninstall Dapr first as follows:

PS C:\Repos\practical-dapr\chapter01> dapr uninstall --all

With the CLI updated and Dapr uninstalled, we can repeat the Dapr installation as follows:

PS C:\Repos\practical-dapr\chapter01> dapr init

After we executedapr init, checking the Dapr version, we can see it has now moved forward from 1.0 to 1.1 for both the CLI and the runtime, as illustrated in the following code snippet:

PS C:\Repos\practical-dapr\chapter01> dapr --versionCLI version:  1.8.1 Runtime version: 1.8.4

Our Dapr testenvironment is up and running. We are now ready to try itwith our first sample.

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

1. 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

2. Then, we add the reference to the Dapr SDK for ASP.NET. The current version is1.5.0. You can look for the package versions on NuGet athttps://www.nuget.org/packages/Dapr.Actors.AspNetCore with thedotnet 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

3. 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.
4. To support Dapr in ASP.NET 6 and leverage minimal hosting and global usings, we made a few changes to the code inProgram.cs. We changed thebuilder.Services.AddControllers() method tobuilder.Services.AddControllers().AddDapr().

We also addedapp.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 commentedapp.UseHttpsRedirection().

Thefollowing is the modified code of theProgram.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/swashbucklebuilder.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 thepreceding code block, we instructed Dapr to leverage theModel-View-Controller (MVC) pattern in ASP.NET 6.

5. Finally, we added a controller namedHelloWorldController as illustrated in thefollowing 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.

6. 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 as5000 but we changed the Dapr HTTP port to5010. 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 runStarting Dapr with id hello-world. HTTP Port: 5010. gRPCPort: 52443

Theinitial message informs you that Dapr is going to use port5010 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 runYou're up and running! Both Dapr and your app logs willappear here.

At this stage, ASP.NET is responding locally on port5000 and Dapr is responding on port5010. In order to test Dapr, let’s invoke acurl 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/helloHello, 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 asConsole.WriteLine sends its output to the Dapr window as follows:

== APP == Hello, World.

7. From another window, let’s verify our Dapr service details. Instead of using thedapr list command, let’s open the Dapr dashboard as follows:

   PS C:\Windows\System32> dapr dashboard

   Dapr Dashboard running on http://localhost:8080

Wecan open the dashboard by navigating tohttp://localhost:8080 to reveal the following screen:

Figure 1.3 – Dapr dashboard application

The Dapr dashboard shown inFigure 1.3 illustrates the details of ourhello-world application.

In this case, the Dapr dashboard shows only this sample application we are running onthe 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

InFigure 1.4, the Dapr dashboard shows us that the local installation of Redis is configuredas 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.

In this chapter, you have learned about the Dapr project, its components, building blocks, and the sidecar approach. All of these concepts will be explored individually in further depth in the following chapters. You are now able to set up Dapr on your local development machine and prepare all the necessary tools to make this experience easier.

You have also learned how to create a simple ASP.NET project and how to configure and check Dapr, and we have had a glimpse of the Dapr dashboard where we can gain a complete and immediate view of the Dapr environment.

In the next chapter, we will use the newly created environment to learn how to debug Dapr.

1. Which building blocks does Dapr provide?
2. What is the relationship between the Dapr CLI and Dapr runtime?
3. How can you install Dapr on your local development environment?
4. Which alternative methods can you follow to install Dapr in Kubernetes?

• Overview of Dapr: https://docs.dapr.io/concepts/overview/
• Getting Started with Dapr: https://docs.dapr.io/getting-started/
• Roadmap of Dapr: https://docs.dapr.io/contributing/roadmap/