NET-Microservices-Architecture-for-Containerized-NET-Applications

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business microservice composed of several physical services. But ultimately, both patterns -BoundedContext and microservice- are closely related.DDD benefits from microservices by getting real boundaries in the form of distributed microservices.But ideas like not sharing the model between microservices are what you also want in a BoundedContext.Additional resources• Chris Richardson. Pattern: Database per servicehttps://microservices.io/patterns/data/database-per-service.html• Martin Fowler. BoundedContexthttps://martinfowler.com/bliki/BoundedContext.html• Martin Fowler. PolyglotPersistencehttps://martinfowler.com/bliki/PolyglotPersistence.html• Alberto Brandolini. Strategic Domain Driven Design with Context Mappinghttps://www.infoq.com/articles/ddd-contextmappingLogical architecture versus physical architectureIt’s useful at this point to stop and discuss the distinction between logical architecture and physicalarchitecture, and how this applies to the design of microservice-based applications.To begin, building microservices doesn’t require the use of any specific technology. For instance,Docker containers aren’t mandatory to create a microservice-based architecture. Those microservicescould also be run as plain processes. Microservices is a logical architecture.Moreover, even when a microservice could be physically implemented as a single service, process, orcontainer (for simplicity’s sake, that’s the approach taken in the initial version of eShopOnContainers),this parity between business microservice and physical service or container isn’t necessarily required inall cases when you build a large and complex application composed of many dozens or evenhundreds of services.This is where there’s a difference between an application’s logical architecture and physicalarchitecture. The logical architecture and logical boundaries of a system do not necessarily map oneto-oneto the physical or deployment architecture. It can happen, but it often doesn’t.Although you might have identified certain business microservices or Bounded Contexts, it doesn’tmean that the best way to implement them is always by creating a single service (such as an ASP.NETWeb API) or single Docker container for each business microservice. Having a rule saying eachbusiness microservice has to be implemented using a single service or container is too rigid.Therefore, a business microservice or Bounded Context is a logical architecture that might coincide (ornot) with physical architecture. The important point is that a business microservice or BoundedContext must be autonomous by allowing code and state to be independently versioned, deployed,and scaled.32 CHAPTER 4 | Architecting container and microservice-based applications
As Figure 4-8 shows, the catalog business microservice could be composed of several services orprocesses. These could be multiple ASP.NET Web API services or any other kind of services usingHTTP or any other protocol. More importantly, the services could share the same data, as long asthese services are cohesive with respect to the same business domain.Figure 4-8. Business microservice with several physical servicesThe services in the example share the same data model because the Web API service targets the samedata as the Search service. So, in the physical implementation of the business microservice, you’resplitting that functionality so you can scale each of those internal services up or down as needed.Maybe the Web API service usually needs more instances than the Search service, or vice versa.In short, the logical architecture of microservices doesn’t always have to coincide with the physicaldeployment architecture. In this guide, whenever we mention a microservice, we mean a business orlogical microservice that could map to one or more (physical) services. In most cases, this will be asingle service, but it might be more.Challenges and solutions for distributed datamanagementChallenge #1: How to define the boundaries of each microserviceDefining microservice boundaries is probably the first challenge anyone encounters. Each microservicehas to be a piece of your application and each microservice should be autonomous with all thebenefits and challenges that it conveys. But how do you identify those boundaries?First, you need to focus on the application’s logical domain models and related data. Try to identifydecoupled islands of data and different contexts within the same application. Each context could havea different business language (different business terms). The contexts should be defined and managedindependently. The terms and entities that are used in those different contexts might sound similar,but you might discover that in a particular context, a business concept with one is used for a different33 CHAPTER 4 | Architecting container and microservice-based applications
Page 2 and 3: EDITION v3.1.1 - Updated to ASP.NET
Page 4 and 5: ContentsIntroduction ..............
Page 6 and 7: Communication styles ..............
Page 8 and 9: Using message brokers and services
Page 10 and 11: Additional resources ..............
Page 12 and 13: Issue security tokens from an ASP.N
Page 14 and 15: coinciding in time with the .NET Co
Page 16 and 17: similar to instantiating a process
Page 18 and 19: For VMs, there are three base layer
Page 20 and 21: (heavier), an image containing only
Page 22 and 23: The registry is like a bookshelf wh
Page 24 and 25: • You need to use Windows APIs th
Page 26 and 27: Linux or Windows Nano, you can run
Page 28 and 29: ImportantYour development machines
Page 30 and 31: Imagemcr.microsoft.com/dotnet/core/
Page 32 and 33: CHAPTER 4Architecting container and
Page 34 and 35: For example, in a typical e-commerc
Page 36 and 37: Figure 4-4. Publishing a single-con
Page 38 and 39: tmpfs mounts are basically virtual
Page 40 and 41: and decentralized data management)
Page 42 and 43: transactional purchase subsystems,
Page 46 and 47: purpose in another context, and mig
Page 48 and 49: Figure 4-9. A microservice can’t
Page 50 and 51: Therefore, in order to enforce micr
Page 52 and 53: entities can be defined, depending
Page 54 and 55: The API gateway pattern versus the
Page 56 and 57: actions impact maintenance pretty b
Page 58 and 59: Figure 4-13.1. Using multiple custo
Page 60 and 61: Azure API ManagementAzure API Manag
Page 62 and 63: • If the API Gateway is developed
Page 64 and 65: A microservice-based application wi
Page 66 and 67: You might use any protocol to commu
Page 68 and 69: Figure 4-17. One-to-one real-time a
Page 70 and 71: Note that when the commands come fr
Page 72 and 73: service-bus features on top of lowe
Page 74 and 75: Microservices addressability and th
Page 76 and 77: Figure 4-21. Example of a composite
Page 78 and 79: the event order is challenging. In
Page 80 and 81: • Connect Windows computers to th
Page 82 and 83: Software platforms for container cl
Page 84 and 85: Figure 4-25. Running Kubernetes in
Page 86 and 87: This feature is based on URL prefix
Page 88 and 89: Additional resources• Visual Stud
Page 90 and 91: Step 1. Start coding and create you
Page 92 and 93: Figure 5-3. Enabling Docker Support
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FROM mcr.microsoft.com/dotnet/core/
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1 FROM mcr.microsoft.com/dotnet/cor
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For the final optimization, it just
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Step 4. Define your services in doc
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Figure 5-7. Adding Docker support i
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Using Docker CLITo run a multi-cont
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Figure 5-14. Example of testing you
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Additional resources• aspnet-dock
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to consume. It should also be able
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Figure 6-1. The eShopOnContainers r
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deployment architecture can bring d
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Figure 6-2. External versus interna
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Multi-architectural pattern and pol
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Figure 6-6. Creating an ASP.NET Cor
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any SQL Server, such as Windows on-
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.Take(pageSize).ToListAsync();items
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# docker-compose.override.yml#catal
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microservice, either data-driven mi
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The Swashbuckle generated Swagger U
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Figure 6-10. Swagger JSON metadataI
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basket-api:image: eshop/basket-apie
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Using docker-compose files to targe
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Figure 6-12. Multiple docker-compos
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#docker-compose.override.yml (Exten
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docker-compose.prod.yml with differ
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Additional resources• Building Op
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Log.Information("Starting web host
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}static IEnumerable<CatalogType> Ge
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Implementing event-based communicat
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}}OldPrice = oldPrice;The integrati
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use the API and abstractions provid
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Implementing a simple publish metho
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Subscribing to eventsThe first step
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Let’s go back to the initial issu
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The approach illustrated in Figure
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After the ProductPriceChangedIntegr
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the system handles the event. Messa
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• Chris Richardson. Event Sourcin
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Integration testing ensures that an
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Unit and integration test per micro
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Since .NET Core 2.0, the framework
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The IHostedService as defined in .N
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public class GracePeriodManagerServ
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• GenericHost Sample using ASP.NE
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Figure 6-30. Sample Web API microse
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This command only runs the catalog-
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The important point here for Ocelot
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Using a single Docker container ima
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- "5203:80"volumes:- ./src/ApiGatew
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Figure 6-38. Zoom in vision of the
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In any case, if the app is secured
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Using Kubernetes Ingress plus Ocelo
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CHAPTER 7Tackle BusinessComplexity
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DDD books• Eric Evans. Domain-Dri
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Figure 7-2. Simplified CQRS- and DD
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There is only one application archi
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Dapper is an open-source project (o
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}}}@"SELECT o.[Id] as ordernumber,o
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https://docs.microsoft.com/archive/
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The three layers in a DDD microserv
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Thus, your layers or class librarie
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has a lot of logic implemented in t
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The Aggregate patternA domain model
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Additional resources• Vaughn Vern
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Figure 7-11. The order aggregate in
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For example, following DDD patterns
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Additional resources• Vaughn Vern
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{if (!_requestedHashCode.HasValue)_
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Figure 7-13. Address value object w
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}{return false;}}return !thisValues
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Just by looking at the domain model
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• The identity (key) of an owned
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public abstract class Enumeration :
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if the validation fails. There are
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• Martin Fowler. Replacing Throwi
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What is a domain event?An event is
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It is important to understand that
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public class OrderStartedDomainEven
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Notice that the only thing that the
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current state of the aggregates. Th
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{}IIdentityService identityService)
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The Repository patternRepositories
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public interface IOrderRepository :
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• Eric Evans. Domain-Driven Desig
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Note that the OrderItems property c
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suggested by this guide have severa
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The repository instance lifetime in
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orderConfiguration.Property<int?>("
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// GENERIC SPECIFICATION IMPLEMENTA
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Use NoSQL databases as a persistenc
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When you use a C# model to implemen
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As shown in the following image, by
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Figure 7-22. MongoDB API NuGet pack
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Retrieve the dataIn C# code, like W
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Design the microservice application
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application’s Startup class. Your
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Use Autofac as an IoC containerYou
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Figure 7-24 shows that the UI app s
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}CardTypeId = cardTypeId;CardExpira
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As an example of a command handler
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Figure 7-25. Using the Mediator pat
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Additionally, async commands are on
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var createOrderCommand = new Create
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// CreateOrderCommandHandler.cspubl
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public class MediatorModule : Autof
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public class CreateOrderCommandVali
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CHAPTER 8Implement resilientapplica
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Figure 8-2. The impact of having an
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certain failure scenarios faster th
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public async Task<IActionResult> Up
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Issues with the original HttpClient
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Figure 8-4. Using IHttpClientFactor
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Implement your Typed Client classes
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Implement HTTP call retries with ex
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complete failure of a service. In t
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One option is to lower the allowed
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Additional resources• Circuit Bre
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CancellationToken cancellationToken
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tags: new string[] { "catalogstorag
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HealthChecksUI is easy to consume w
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CHAPTER 9Make secure .NETMicroservi
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public void ConfigureServices(IServ
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TipAll details are handled by the a
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}});options.Scope.Add("webshoppinga
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The parameters in this usage are:
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In this example, only users in the
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code and making sure not to store s
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ImportantWe recommend that you regi
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CLI versus IDE. With Microsoft tool
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