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Chapter 1: Introducing Dapr
This chapter will introduce you to the Distributed Application Runtime (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:
- An overview of Dapr
- The architecture of Dapr
- Setting up Dapr
- Building our first Dapr sample
At this stage, learning these topics is important with regard to obtaining a solid foundation on Dapr internals and understanding its approach to 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.
Technical requirements
The code for this sample can be found in GitHub at https://github.com/PacktPublishing/Practical-Microservices-with-Dapr-and-.NET/tree/main/chapter01.
In this chapter, the working area for scripts and code is expected to be <repository path>\chapter01\. In my local environment, it is C:\Repos\dapr-samples\chapter01.
Please refer to the Setting up Dapr section for a complete guide to the tools needed to develop with Dapr and work with the samples.
An overview of Dapr
Dapr is an event-driven, portable runtime created by Microsoft with an open source approach and, at the time of writing this book, is still in active development.
Being event-driven, which is emphasized in the definition of Dapr, plays an important role in microservices as 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 of a Dapr architecture:
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.
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?
This diagram 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) or gRPC Remote Procedure Call (gRPC) calls or, even more simply, via any of the software development kits (SDKs) available. At the time of writing this book, these SDKs are .NET, Java, Go, Python, C++, JavaScript, and Rust.
As we will experience later, it is not necessary to adopt the Dapr SDK in your application: a call 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/<method name>. Nevertheless, using the SDK does provide many benefits if you are writing a Dapr service or leveraging the Dapr actor model.
What Dapr is not
While I hope the overview of Dapr has informed and intrigued you enough to spend time on this book, when I have the chance to talk about Dapr, I often find myself 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's goal is not to 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 pooling 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, Dapr applies retry logic in its interaction with state stores and services, but 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 raising an error back to the client, compensating an operation, or adopting a retry policy (maybe leveraging Polly in .NET), these are explicit choices only the developer can make.
- Dapr is meant 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.
It is also true that Dapr does not run better on Azure than on any other Kubernetes environment in the cloud. I would hope to convince you that Azure Kubernetes Service (AKS) is the best-managed Kubernetes offering in the cloud space, but this is a different conversation for another time.
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, working on macOS, and with Kubernetes as the deployment target—Dapr welcomes all developers in a vendor-neutral and open approach.
The next section will be dedicated to understanding the architectures that Dapr can enable.
The architecture of 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.
Here 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.
- 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: 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. These are outlined here:
- 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 3, 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 4, 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 5, 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 this area).
This building block is presented in more detail in Chapter 6, 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 7, 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 9, Tracing Dapr Applications.
- Secrets: It is a common requirement and a healthy practice to keep secrets at a safe distance from the code, even if only to prevent unintended access in a development environment to the connection string intended for the production environment. Dapr enables you to store secrets and to reference these from other Dapr components, in Kubernetes or Azure Key Vault, among many options.
After learning about Dapr architecture and components, 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.
Setting up Dapr
Dapr is a runtime for every platform and every language. The focus of this book is on C# in .NET, used with Visual Studio Code (VS Code). The code snippets in the book can be appreciated by developers from any background, but nevertheless, you will get the most out of it from a .NET perspective.
The development environment I use is Windows 10, 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 particular action on Linux or a macOS development machine, I encourage you to check the Dapr documentation at https://docs.dapr.io/.
Important note: Updated to production-ready version
The Dapr runtime reached the v1.0 production-ready version in February 2021, as announced in the Dapr blog: https://blog.dapr.io/posts/2021/02/17/announcing-dapr-v1.0/.
The samples and scripts in this book have been updated and tested with v1.1 of Dapr.
Docker
Dapr requires Docker locally on 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 can find detailed instructions for running Docker at https://docs.docker.com/install/.
The Dapr CLI
We will immediately start working with Dapr; therefore, you need to install all the necessary tools. The Dapr runtime and its tools can be found at https://github.com/dapr/cli.
On Windows, it is suggested to use the following command to install the CLI in the %USERPROFILE%\.dapr\ folder and add it to the user PATH environment variable so that the tools can be found from the command line:
powershell -Command "iwr -useb https://raw.githubusercontent.com/dapr/cli/master/install/install.ps1 | iex"
The previous command installs a release candidate (RC) version of the Dapr CLI. Please refer to https://docs.dapr.io/getting-started/install-dapr-cli/ for more details.
We still need to initialize Dapr on the development machine, which we will do later in this chapter.
.NET
To install .NET 5, please refer to https://dotnet.microsoft.com/download for the link to the latest binaries.
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 the dotnet --info command. You should see the following output:
PS C:\Repos\dapr-samples\chapter01> dotnet --info .NET SDK (reflecting any global.json): Version: 5.0.202 Commit: db7cc87d51 Runtime Environment: OS Name: Windows OS Version: 10.0.19042 OS Platform: Windows RID: win10-x64 Base Path: C:\Program Files\dotnet\sdk\5.0.202\ Host (useful for support): Version: 5.0.5 Commit: 2f740adc14 …
This proves .NET has been recognized and the framework is working fine.
VS Code
VS Code is a great multiplatform source code editor by Microsoft. You can install 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 environment and eases the debugging configuration—I highly recommend it. Please follow the instructions at https://docs.dapr.io/developing-applications/ides/vscode/.
Windows Terminal
I really love the new Windows Terminal (https://aka.ms/terminal) for its ease of use and configurability. In the following chapters, we will often have to run multiple commands and tools in parallel. Therefore, the tabs feature of Windows Terminal is just one of the reasons why I suggest you adopt it too.
Installing self-hosted Dapr
Dapr can be initialized in two modes: self-hosted (or standalone) and Kubernetes.
As it is intended to be used only for a development environment, the self-hosted mode locally installs Redis, the Dapr placement services, and Zipkin. The following command initializes Dapr on your local environment:
dapr init
In a local development environment, it might happen that the ports Dapr intends 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 the init command, this is the output you should expect:
PS C:\Repos\dapr-samples\chapter01> dapr init Making the jump to hyperspace... Downloading 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 use docker ps, as follows:
PS C:\Repos\dapr-samples\chapter01> docker ps --format "{{.ID}}: {{.Image}} - {{.Ports}} - {{.Names}}"
2082b7f0eda4: daprio/dapr - 0.0.0.0:6050->50005/tcp - dapr_placement
6c68d869cea7: redis - 0.0.0.0:6379->6379/tcp - dapr_redis
e4c8eae6992d: openzipkin/zipkin - 9410/tcp, 0.0.0.0:9411->9411/tcp - dapr_zipkin
The output shows the Docker container running on my machine.
Installing Dapr on Kubernetes
Dapr is specifically intended to be executed on Kubernetes. From your development machine on which you have 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 a continuous integration/continuous deployment (CI/CD) pipeline that takes care of the Dapr installation on the Kubernetes cluster too, this can also work, although it is out of scope for the present setup.
To verify the installation completed successfully, execute this command:
kubectl get pods --namespace dapr-system
The command should display the pods in the dapr-system namespace.
Updating the Dapr version
On a development Windows machine on which a previous version of Dapr was already present, this is the output of an update of the CLI:
PS C:\Repos\dapr-samples\chapter01> powershell -Command "iwr -useb https://raw.githubusercontent.com/dapr/cli/master/install/install.ps1 | iex" WARNING: Dapr is detected - c:\dapr\dapr.exe CLI version: 1.0.1 Runtime version: 1.0.0 Reinstalling Dapr... Creating c:\dapr directory Downloading https://api.github.com/repos/dapr/cli/releases/assets/34341976 ... Extracting c:\dapr\dapr_windows_amd64.zip... CLI version: 1.1.0 Runtime version: 1.0.0 Clean up c:\dapr\dapr_windows_amd64.zip... Try to add c:\dapr to User Path Environment variable... Skipping to add c:\dapr to User Path - … omitted … Dapr CLI is installed successfully. To get started with Dapr, please visit https://docs.dapr.io/getting-started/ . Ensure that Docker Desktop is set to Linux containers mode when you run Dapr in self hosted mode.
The process to update the Dapr runtime is similar to the initialization, but first, we will need to uninstall Dapr from your machine, as follows:
PS C:\Repos\dapr-samples\chapter01> dapr uninstall Removing Dapr from your machine... Removing directory: C… Removing container: dapr_placement Dapr has been removed successfully
After we execute dapr 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\dapr-samples\chapter01> dapr --version CLI version: 1.1.0 Runtime version: 1.1.1
Our Dapr test environment is up and running: we are now ready to try it with our first sample.
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. I chose to base all my samples in the C:\Repos\dapr-samples\ folder, and I created a C:\Repos\dapr-samples\chapter01 folder for this first sample. We'll take the following steps:
- Let's start by creating a Web API .NET project, as follows:
PS C:\Repos\dapr-samples\chapter01> dotnet new webapi -o dapr.microservice.webapi
- Then, we add the reference to the Dapr SDK for ASP.NET. The current version is
1.1.0. You can look for the package versions on NuGet at https://www.nuget.org/packages/Dapr.Actors.AspNetCore with thedotnet add packagecommand, as illustrated in the following code snippet:PS C:\Repos\dapr-samples\chapter01> dotnet add package Dapr.AspNetCore --version 1.1.0
- 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, I made a few changes to the code. In
Startup.cs, I changed theConfigureServicesmethod toservices.AddControllers().AddDapr();.In
Configure, I also addedendpoints.MapSubscribeHandler();. This is not necessary for our sample, as we will not use the pub/sub features of Dapr. Nevertheless, 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, I removed
app.UseHttpsRedirection();.Here is the modified code of the
Startup.csclass:using Microsoft.AspNetCore.Builder; using Microsoft.AspNetCore.Hosting; using Microsoft.Extensions.Configuration; using Microsoft.Extensions.DependencyInjection; using Microsoft.Extensions.Hosting; namespace dapr.microservice.webapi { public class Startup { public Startup(IConfiguration configuration) { Configuration = configuration; } public IConfiguration Configuration { get; } // This method gets called by the runtime. Use //this method to add services to the container. public void ConfigureServices (IServiceCollection services) { services.AddControllers().AddDapr(); } // This method gets called by the runtime. Use //this method to configure the HTTP request pipeline. public void Configure(IApplicationBuilder app, IWebHostEnvironment env) { if (env.IsDevelopment()) { app.UseDeveloperExceptionPage(); } app.UseRouting(); app.UseAuthorization(); app.UseEndpoints(endpoints => { endpoints.MapSubscribeHandler(); endpoints.MapControllers(); }); } } }In the preceding code block, I instructed Dapr to leverage the model-view-controller (MVC) pattern in ASP.NET. Keep in mind there is an alternate approach for Dapr in ASP.NET, which does rely on routing with
MapGet(...)andMapPost(...). You can see an example at https://github.com/dapr/dotnet-sdk/tree/master/examples/AspNetCore/RoutingSample. - Finally, I added a controller named
HelloWorldController, as illustrated in the following code snippet:using Dapr; using Microsoft.AspNetCore.Mvc; using System; namespace dapr.microservice.webapi.Controllers { [ApiController] public class HelloWorldController : ControllerBase { [HttpGet("hello")] public ActionResult<string> Get() { Console.WriteLine("Hello, World."); return "Hello, World"; } } }In the preceding code snippet, you can see
[HttpGet("hello")]: this ASP.NET attribute is evaluated by Dapr to identify the method name. - In order to run a Dapr application, you use the following format:
dapr run --app-id <your app id> --app-port <port of the application> --dapr-http-port <port in Dapr> dotnet run
I left the ASP.NET default port as
5000but I changed the Dapr HTTP port to5010. The following command line launches the Dapr application:PS C:\Repos\dapr-samples\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
5010for 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 this part:
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
5000and Dapr is responding on port5010. In order to test Dapr, let's invoke acurlcommand, as follows. Using the browser is equally fine:PS C:\Repos\dapr-samples\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 it logged as
Console.WriteLinesends 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 listcommand, let's open the Dapr dashboard, like this: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 here:
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.
Summary
In this chapter, you have learned about the Dapr project, with 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.
