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:
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.
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:Reposdapr-sampleschapter01.
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.
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:
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:
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.
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:
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.
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:
Dapr provides several building blocks that microservice application developers can adopt selectively, based on their needs. These are outlined here:
This building block is presented in more detail in Chapter 3, Service-to-Service Invocation.
You can learn about this building block in Chapter 4, Introducing State Management.
A discussion of this building block is presented in Chapter 5, Publish and Subscribe.
This building block is presented in more detail in Chapter 6, Resource Bindings.
You can learn about this building block in Chapter 7, Using Actors.
This building block is presented in more detail in Chapter 9, Tracing Dapr Applications.
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.
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.
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/.
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.
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:Reposdapr-sampleschapter01> 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 Filesdotnetsdk5.0.202
Host (useful for support):
Version: 5.0.5
Commit: 2f740adc14
…
This proves .NET has been recognized and the framework is working fine.
VS Code 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.
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/.
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.
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:Reposdapr-sampleschapter01> 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:Usersdabedin.daprin.
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:Reposdapr-sampleschapter01> 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.
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.
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:Reposdapr-sampleschapter01> powershell -Command "iwr -useb https://raw.githubusercontent.com/dapr/cli/master/install/install.ps1 | iex"
WARNING: Dapr is detected - c:daprdapr.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:daprdapr_windows_amd64.zip...
CLI version: 1.1.0
Runtime version: 1.0.0
Clean up c:daprdapr_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:Reposdapr-sampleschapter01> 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:Reposdapr-sampleschapter01> 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.
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:Reposdapr-samples folder, and I created a C:Reposdapr-sampleschapter01 folder for this first sample. We'll take the following steps:
PS C:Reposdapr-sampleschapter01> dotnet new webapi -o dapr.microservice.webapi
PS C:Reposdapr-sampleschapter01> dotnet add package Dapr.AspNetCore --version 1.1.0
In Configure, I also added endpoints.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.cs class:
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(...) and MapPost(...). You can see an example at https://github.com/dapr/dotnet-sdk/tree/master/examples/AspNetCore/RoutingSample.
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.
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 5000 but I changed the Dapr HTTP port to 5010. The following command line launches the Dapr application:
PS C:Reposdapr-sampleschapter01dapr.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 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 5000 and Dapr is responding on port 5010. In order to test Dapr, let's invoke a curl command, as follows. Using the browser is equally fine:
PS C:Reposdapr-sampleschapter01> 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.WriteLine sends its output to the Dapr window, as follows:
== APP == Hello, World.
PS C:WindowsSystem32> 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:
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:
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.
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.
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