Your First Microservice in .NET 6

Very simple way to start writing microservices... It is just writing one service and don't cover communication of microservices  or  deployment configuration , but really very good to start with Microservices.

 More than a buzzword, microservices are here to stay and are currently gaining popularity due to their acceptance in the systems development market. In this article, we’ll explore some valuable features available on the .NET platform and create our first microservice.

Results obtained recently show that the architecture based on microservices can be a great option when implementing new features.

This is due to the versatility of microservices, which, despite being relatively new, already present excellent results and their use has been growing exponentially, especially in recent years. With the evolution of the .NET platform, which is currently in its sixth version, implementing microservices has become even simpler.

In this article, we’ll spend a little time defining “microservices” and then we will create a microservice from scratch.

What Are Microservices?

Although there is no exact definition of what microservices are, based on what Martin Fowler, one of the biggest references on the subject today, says, microservices can be used to describe a way to design software applications composed of small sets of services that work and communicate with each other independently, consenting to a single concept. As well as its functioning, the implementation of microservices also happens independently.

Why Microservices?

We can say that microservices are the opposite of monoliths, and there is a lot of discussion about which would be ideal. There are many reasons to use monoliths, Fowler himself is an advocate of monoliths, but let’s focus on the advantages of using microservices.

Microservices make it easier to develop, test and deploy isolated parts of an application. Each microservice can be independently scaled as needed. Your implantation also is simple and does not need to have a dependence on other parts.

Each microservice uses its own database, reserved for its own scope, which avoids the many problems that can arise from two or more systems using the same database.

Obviously, microservices do not solve all problems and also have disadvantages. One of them is the complexity created by dividing a module into several microservices. Despite having some disadvantages, results obtained mainly in recent years show that systems with architectures based on microservices are achieving great results.

ASP.NET Core and Microservices

Like other development platforms, Microsoft has invested heavily to meet the requirements of an architecture based on microservices. Today .NET provides many resources for this purpose.

Microsoft’s official website has a lot of content about microservices-based architecture, including ebooks, tutorials, videos and challenges to help developers work with them.

With .NET 6, developing apps in a microservices architecture became even easier due to the new minimal APIs feature that simplifies many processes that were once mandatory but are now no longer needed.

---

Low Ceremony, High Value: A Tour of Minimal APIs in .NET 6

 

Minimal APIs allow you to build APIs without the overhead of the complicated MVC solution. Read more to understand what this means for building APIs in ASP.NET Core.

---

Practical Approach

In this article, we will create a simple microservice, which performs a request in an API and return this data in the response.

Create the Project

To follow this tutorial, you need to download and install the .NET SDK (Software Development Kit), in version 6.

You can access the full source code at this link: Source Code.

The final structure of the project will be as follows:

In your command prompt, run the following command to create your minimal API project:

dotnet new web -o UserManager -f net6.0

What do these commands mean?

• The “dotnet new web” command creates a new application of type web API (that’s a REST API endpoint).
• The “-o” parameter creates a directory named UserManager where your app is stored.
• The “-f net6.0” command is to inform the .NET version that we will be using.

Now open the file “UserManager.csproj” generated at the root of the project with your favorite IDE—this tutorial uses Visual Studio 2022.

And then we have the following structure generated by the previous command. This is a standard minimal API framework in .NET 6.

Create the Microservice

The minimal API we created already contains everything we need to start implementing our microservice, which will have the following structure:

/Solution.sln
|
|---- UserManager.API.Default                       <-- Public API
|      |---- Program.cs                             <-- Dependency injection
|      |---- /Endpoints                                  
|      |     |---- UserEndpoints.cs                 <-- API Endpoints
|---- UserManager.Application                       <-- Layer for exposure of repository and services
|     |---- /Contracts                              <-- Contracts that are exposed to the customer
|     |     |---- /v1                               <-- Version
|     |     |     |---- /Users                      <-- Request and Response Classes
|     |     |     |     |---- /Response
|     |     |     |     |     |---- GetUsersResponse.cs
|     |---- /Services
|     |     |---- /v1                               <-- Version
|     |     |     |---- IUserConfigService          <-- Interface of service
|     |     |     |---- UserConfigService           <-- Service class

In Visual Studio rename the project from “UserManager” to “UserManager.API.Default”. Then, right-click on the solution name and follow the following sequence:

Add --> New Project… --> Class Library --> Next --> (Put the name: “UserManager.Application”) --> Next --> .NET 6.0 --> Create

We created the layer for exposure of repository and services. Now we will create the contracts that are exposed to the customer. In the UserManager.Application project, create a new folder and rename it with “Contracts”.

Inside it, create the following structure of folders v1–> Users --> Response, and inside “Response” create a new class called “GetUsersResponse”, and replace the code generated in it with this:

public record GetUsersResponse
{
    public List<User> Users { get; set; } = new List<User>();

    public record User
    {
        public int id { get; set; }
        public string name { get; set; }
        public string username { get; set; }
        public string email { get; set; }
        public Address address { get; set; }
        public string phone { get; set; }
        public string website { get; set; }
        public Company company { get; set; }
    }

    public record Address
    {
        public string street { get; set; }
        public string suite { get; set; }
        public string city { get; set; }
        public string zipcode { get; set; }
        public Geo geo { get; set; }
    }

    public record Geo
    {
        public string lat { get; set; }
        public string lng { get; set; }
    }

    public record Company
    {
        public string name { get; set; }
        public string catchPhrase { get; set; }
        public string bs { get; set; }
    }
}

C#

This class has a list of users, which will contain the data received in the response to the request.

Now let’s create the service class which will contain the microservice’s business rules.

Still in the UserManager.Application project, create a new folder and rename it with “Services”. Inside it, create a folder called “v1”. Inside v1, create a new interface called “IUserConfigService” and replace the code generated in it with this:

public interface IUserConfigService
{
    public Task<GetUsersResponse> GetAllUsersAsync();
    public Task<GetUsersResponse> GetUserByIdAsync(int id);
}

C#

And create a class called “UserConfigService” and replace the code generated in it with this:

using Newtonsoft.Json;
using static GetUsersResponse;

public class UserConfigService : IUserConfigService
{
    private readonly HttpClient _httpClient;

    public UserConfigService(HttpClient httpClient)
    {
        _httpClient = httpClient;
    }

    public async Task<GetUsersResponse> GetAllUsersAsync()
    {
        var userResponse = new GetUsersResponse();
        var uri = "https://jsonplaceholder.typicode.com/users";
        var responseString = await _httpClient.GetStringAsync(uri);
        var users = JsonConvert.DeserializeObject<List<User>>(responseString);

        userResponse.Users = users;
        return userResponse;
    }

    public async Task<GetUsersResponse> GetUserByIdAsync(int id)
    {
        var userResponse = new GetUsersResponse();
        var uri = $"https://jsonplaceholder.typicode.com/users?id={id}";
        var responseString = await _httpClient.GetStringAsync(uri);
        var users = JsonConvert.DeserializeObject<List<User>>(responseString);

        userResponse.Users = users;
        return userResponse;
    }
}

C#

You will need to install the “Newtonsoft.Json” library. You can do this through Visual Studio.

Explanation

First, we created an interface that will contain the main methods of the service. Next, we created the user service class, which will implement these methods.

In the method “GetAllUsersAsync” our service will fetch a list of users from the site “jsonplaceholder.typicode.com”, which provides a free fake API for testing and prototyping. It will return a list of users. This process will be done through a request with the “HttpClient” class that provides methods of communication between APIs.

And in the “GetUserByIdAsync” method it performs a parameterized search, sending the user id in the request and returning the user data correspondent.

In both cases, the return from the API is converted into a list of users compatible with the record User of the contract.

Creating the Endpoints

Now we need to create the endpoints that will use the service methods. In .NET 6 we don’t need a “controller” anymore so we’ll create a class that will implement the endpoints.

So in the project “UserManager.API.Default” create a new folder called “Endpoints”, and inside create a class called “UserEndpoints”. Then replace the code generated in it with this:

public static class UserEndpoints
{
    public static void MapUsersEndpoints(this WebApplication app)
    {
        app.MapGet("/v1/users", GetAllUsers);
        app.MapGet("/v1/users/{id}", GetUserById);
    }

    public static void AddUserServices(this IServiceCollection service)
    {
        service.AddHttpClient<IUserConfigService, UserConfigService>();
    }

    internal static IResult GetAllUsers(IUserConfigService service)
    {
        var users = service.GetAllUsersAsync().Result.Users;

        return users is not null ? Results.Ok(users) : Results.NotFound();
    }

    internal static IResult GetUserById(IUserConfigService service, int id)
    {
        var user = service.GetUserByIdAsync(id).Result.Users.SingleOrDefault();

        return user is not null ? Results.Ok(user) : Results.NotFound();
    }
}

C#

You will need to add in the project “UserManager.API.Default” the dependency of the project “UserManager.Application”. This is easy, just right-click on the file “Dependencies” of the “UserManager.API.Default” project --> “Add Project Reference…” and choose the project “UserManager.Application”

Explanation

In the class above, we are creating the endpoints in the “MapUsersEndpoints” method.

The “AddUserServices” method will inject the dependency of the Service and its interface, and the other two methods using the service return the search result—if it is null, a “NotFound” status will be displayed in the response.

Now in the Program class, we will add the service and swagger settings. So, replace the code from the Program.cs file with the code below.

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddUserServices();
builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen();

var app = builder.Build();

app.MapUsersEndpoints();

if (app.Environment.IsDevelopment())
{
    app.UseSwagger();
    app.UseSwaggerUI();
}

app.UseHttpsRedirection();

app.Run();

C#

You will need to install the “Swashbuckle.AspNetCore” library. You can do this through Visual Studio.

And in the file “launchSettings.json” under the setting "launchBrowser": true, add this:

"launchUrl": "swagger"

There are two places, inside “profiles” and “IIS Express”.

Finally, our microservice is ready to run. If you run it in Visual Studio using the “IIS Express” option, you will get the following result in your browser.

Now if you access the addresses https://localhost:<port number>/v1/users and https://localhost:<port number>/v1/users/1, you will get the following results:

Conclusion

In this article, we had an introduction to the topic “microservices” and we created a simple microservice in .NET 6 that communicates with another API and displays user data.

The possibilities when working with microservices are endless, so feel free to implement more functions in the project, such as creation and update methods, communication with a database, validations, unit tests and much more.

How Netflix Scales its API with GraphQL Federation (Part 1)

 Netflix is known for its loosely coupled and highly scalable microservice architecture. Independent services allow for evolving at different paces and scaling independently. Yet they add complexity for use cases that span multiple services. Rather than exposing 100s of microservices to UI developers, Netflix offers a unified API aggregation layer at the edge.

UI developers love the simplicity of working with one conceptual API for a large domain. Back-end developers love the decoupling and resilience offered by the API layer. But as our business has scaled, our ability to innovate rapidly has approached an invisible asymptote. As we’ve grown the number of developers and increased our domain complexity, developing the API aggregation layer has become increasingly harder.

In order to address this rising problem, we’ve developed a federated GraphQL platform to power the API layer. This solves many of the consistency and development velocity challenges with minimal tradeoffs on dimensions like scalability and operability. We’ve successfully deployed this approach for Netflix’s studio ecosystem and are exploring patterns and adaptations that could work in other domains. We’re sharing our story to inspire others and encourage conversations around applicability elsewhere.

Case Study: Studio Edge

Intro to Studio Ecosystem

Netflix is producing original content at an accelerated pace. From the time a TV show or a movie is pitched to when it’s available on Netflix, a lot happens behind the scenes. This includes but is not limited to talent scouting and casting, deal and contract negotiations, production and post-production, visual effects and animations, subtitling and dubbing, and much more. Studio Engineering is building hundreds of applications and tools that power these workflows.

Content Lifecycle

Studio API

Looking back to a few years ago, one of the pains in the studio space was the growing complexity of the data and its relationships. The workflows depicted above are inherently connected but the data and its relationships were disparate and existed in myriads of microservices. The product teams solved for this with two architectural patterns.

1) Single-use aggregation layers — Due to the loose coupling, we observed that many teams spent considerable effort building duplicative data-fetching code and aggregation layers to support their product needs. This was either done by UI teams via BFF (Backend For Frontend) or by a backend team in a mid-tier service.

2) Materialized views for data from other teams — some teams used a pattern of building a materialized view of another service’s data for their specific system needs. Materialized views had performance benefits, but data consistency lagged by varying degrees. This was not acceptable for the most important workflows in the Studio. Inconsistent data across different Studio applications was the top support issue in Studio Engineering in 2018.

Graph API: To better address the underlying needs, our team started building a curated graph API called “Studio API”. Its goal was to provide an unified abstraction on top of data and relationships. Studio API used GraphQL as its underlying API technology and created significant leverage for accessing core shared data. Consumers of Studio API were able to explore the graph and build new features more quickly. We also observed fewer instances of data inconsistency across different UI applications, as every field in GraphQL resolves to a single piece of data-fetching code.

Studio API Graph

Studio API Architecture

Bottlenecks of Studio API

The One Graph exposed by Studio API was a runaway success; product teams loved the reusability and easy, consistent data access. But new bottlenecks emerged as the number of consumers and amount of data in the graph increased.

First, the Studio API team was disconnected from the domain expertise and the product needs, which negatively impacted the schema’s health. Second, connecting new elements from a back-end into the graph API was manual and ran counter to the rapid evolution promised by a microservice architecture. Finally, it was hard for one small team to handle the increasing operational and support burden for the expanding graph.

We knew that there had to be a better way — unified but decoupled, curated but fast moving.

Returning to Core Principles

To address these bottlenecks, we leaned into our rich history of microservices and breaking monoliths apart. We still wanted to keep the unified GraphQL schema of Studio API but decentralize the implementation of the resolvers to their respective domain teams.

As we were brainstorming the new architecture back in early 2019, Apollo released the GraphQL Federation Specification. This promised the benefits of a unified schema with distributed ownership and implementation. We ran a test implementation of the spec with promising results, and reached out to collaborate with Apollo on the future of GraphQL Federation. Our next generation architecture, “Studio Edge”, emerged with federation as a critical element.

GraphQL Federation Primer

The goal of GraphQL Federation is two-fold: provide a unified API for consumers while also giving backend developers flexibility and service isolation. To achieve this, schemas need to be created and annotated to indicate how ownership is distributed. Let’s look at an example with three core entities:

1. Movie: At Netflix, we make titles (shows, films, shorts etc.). For simplicity, let’s assume each title is a Movie object.
2. Production: Each Movie is associated with a Studio Production. A Production object tracks everything needed to make a Movie including shooting location, vendors, and more.
3. Talent: the people working on a Movie are the Talent, including actors, directors, and so on.

These three domains are owned by three separate engineering teams responsible for their own data sources, business logic, and corresponding microservices. In an unfederated implementation, we would have this simple Schema and Resolvers owned and implemented by the Studio API team. The GraphQL Framework would take in queries from clients and orchestrate the calls to the resolvers in a breadth-first traversal.

Schema & Resolvers for Studio API

To transition to a federated architecture, we need to transfer ownership of these resolvers to their respective domains without sacrificing the unified schema. To achieve this, we need to extend the Movie type across GraphQL service boundaries:

Federating Movie

This ability to extend a Movie type across GraphQL service boundaries makes Movie a Federated Type. Resolving a given field requires delegation by a gateway layer down to the owning domain services.

Studio Edge Architecture

Using the ability to federate a type, we envisioned the following architecture:

Studio Edge Architecture

Key Architectural Components

Domain Graph Service (DGS) is a standalone spec-compliant GraphQL service. Developers define their own federated GraphQL schema in a DGS. A DGS is owned and operated by a domain team responsible for that subsection of the API. A DGS developer has the freedom to decide if they want to convert their existing microservice to a DGS or spin up a brand new service.

Schema Registry is a stateful component that stores all the schemas and schema changes for every DGS. It exposes CRUD APIs for schemas, which are used by developer tools and CI/CD pipelines. It is responsible for schema validation, both for the individual DGS schemas and for the combined schema. Last, the registry composes together the unified schema and provides it to the gateway.

GraphQL Gateway is primarily responsible for serving GraphQL queries to the consumers. It takes a query from a client, breaks it into smaller sub-queries (a query plan), and executes that plan by proxying calls to the appropriate downstream DGSs.

Implementation Details

There are 3 main business logic components that power GraphQL Federation.

Schema Composition

Composition is the phase that takes all of the federated DGS schemas and aggregates them into a single unified schema. This composed schema is exposed by the Gateway to the consumers of the graph.

Schema Composition Phases

Whenever a new schema is pushed by a DGS, the Schema Registry validates that:

1. New schema is a valid GraphQL schema
2. New schema composes seamlessly with the rest of the DGSs schemas to create a valid composed schema
3. New schema is backwards compatible

If all of the above conditions are met, then the schema is checked into the Schema Registry.

Query Planning and Execution

The federation config consists of all the individual DGS schemas and the composed schema. The Gateway uses the federation config and the client query to generate a query plan. The query plan breaks down the client query into smaller sub-queries that are then sent to the downstream DGSs for execution, along with an execution ordering that includes what needs to be done in sequence versus run in parallel.

Query Plan Inputs

Let’s build a simple query from the schema referenced above and see what the query plan might look like.

Simplified Query Plan

For this query, the gateway knows which fields are owned by which DGS based on the federation config. Using that information, it breaks the client query into three separate queries to three DGSs. The first query is sent to Movie DGS since the root field movies is owned by that DGS. This results in retrieving the movieId and title fields for the first 10 movies in the dataset. Then using the movieIds it got from the previous request, the gateway executes two parallel requests to Production DGS and Talent DGS to fetch the production and actors fields for those 10 movies. Upon completion, the sub-query responses are merged together and the combined data response is returned to the caller.

A note on performance: Query Planning and Execution adds a ~10ms overhead in the worst case. This includes the compute for building the query plan, as well as the deserialization of DGS responses and the serialization of merged gateway response.

Entity Resolver

Now you might be wondering, how do the parallel sub-queries to Production and Talent DGS actually work? That’s not something that the DGS supports. This is the final piece of the puzzle.

Let’s go back to our federated type Movie. In order for the gateway to join Movie seamlessly across DGSs, all the DGSs that define and extend the Movie need to agree on one or more fields that define the primary key (e.g. movieId). To make this work, Apollo introduced the @key directive in the Federation Spec. Second, DGSs have to implement a resolver for a generic Query field, _entities. The _entities query returns a union type of all the federated types in that DGS. The gateway uses the _entities query to look up Movie by movieId.

Let’s take a look at how the query plan actually looks like

Detailed Federated Query Plan

The representation object consists of the movieId and is generated from the response of the first request to Movie DGS. Since we requested for the first 10 movies, we would have 10 representation objects to send to Production and Talent DGS.

This is similar to Relay’s Object Identification with a few differences. _Entity is a union type, while Relay’s Node is an interface. Also, with @key, there is support for variable key names and types as well as composite keys while in Relay, the id is a single opaque ID field.

Combined together, these are the ingredients that power the core of a federated API architecture.

The Journey, Summarized

Our Studio Ecosystem architecture has evolved in distinct phases, all motivated by reducing the time between idea and implementation, improving the developer experience, and streamlining operations. The architectural phases look like:

Evolution of an API Architecture

Stay Tuned

Over the past year we’ve implemented the federated API architecture components in our Studio Edge. Getting here required rapid iteration, lots of cross-functional collaborations, a few pivots, and ongoing investment. We’re live with 70 DGSes and hundreds of developers contributing to and using the Studio Edge architecture. In our next Netflix Tech Blog post, we’ll share what we learned along the way, including the cross-cutting concerns necessary to build a holistic solution.

We want to thank the entire GraphQL open-source community for all the generous contributions and paving the path towards the promise of GraphQL. If you’d like to be a part of solving complex and interesting problems like this at Netflix scale, check out our jobs page or reach out to us directly.