Building micro services through Event Driven Architecture part20 : Shared Libraries

Building micro services through Event Driven Architecture part20 : Shared Libraries

This tutorial is the 20th part of a series : Building microservices through Event Driven Architecture.

The previous step is about Building micro services through Event Driven Architecture part19 : Building and Securing Real Time Communications using SignalR and Azure Active

A microservice architecture  structures an application as a set of loosely coupled services.

An real advantage is that when there is a critical need to update a resource, only the microservice containing this resource will be updated, the other microservices  remaining compatible with the modification, unlike the entire  application in a classic architecture.

But what about shared code ?

Because I do not want to code the same functionality several times , I can follow the DRY principle ( Don’t Repeat Yourself)  :  “Every piece of knowledge must have a single, unambiguous, authoritative representation within a system”  https://en.wikipedia.org/wiki/Don%27t_repeat_yourself

But when following DDD (Domain Driven Design) , The DRY principle is about domain knowledge and code duplication may be perfectly fine. 

For those unfamiliar with DDD (Domain Driven Design), I recommend learning the basics. https://martinfowler.com/bliki/DomainDrivenDesign.html

In this tutorial, I will not discuss about the pros and cons of code sharing between micro services, but I will show to share code efficiently between microservices when needed.  I will not share business functionnalites between microservices but only technical libraries like logging/monitoring, helpers, tools, etc…

I will use the versioning package following the semver principle https://semver.org/spec/v1.0.0.html.
This way, when code common to the microservice is updated, the version must be incremented and the package published in a nuget server.
So microservices can use the new version of the package only when needed and independently.

Packaging and Versionning 

To package a Library, I have to open the project properties and check GeneratePackageOnBuild, and fill the properties accordingly as shown in the following figure :

I can also edit the LogCorner.EduSync.Speech.SharedKernel.csproj

<PropertyGroup>
    <TargetFramework>netstandard2.1</TargetFramework>
    <GeneratePackageOnBuild>true</GeneratePackageOnBuild>
    <AssemblyVersion>2.0.1</AssemblyVersion>
    <Version>2.0.1</Version>
    <PackageLicenseExpression>MIT</PackageLicenseExpression>
    <Copyright>LogCorner</Copyright>
    <PackageRequireLicenseAcceptance>True</PackageRequireLicenseAcceptance>
    <FileVersion>2.0.1</FileVersion>
    <PackageProjectUrl>https://logcorner.com/</PackageProjectUrl>
    <RepositoryUrl>https://github.com/logcorner/LogCorner.EduSync.Speech.Command/tree/master/src/LogCorner.EduSync.Speech.SharedKernel</RepositoryUrl>
    <EnforceCodeStyleInBuild>False</EnforceCodeStyleInBuild>
    <EnableNETAnalyzers>True</EnableNETAnalyzers>
    <AnalysisLevel>none</AnalysisLevel>
    <Title>The Speech Micro Service Command Shared Kernel</Title>
    <Company>Gora LEYE</Company>
    <Description>The Speech Micro Service Command Shared kernel contains a set of tools to serialize and deserialize events</Description>
    <PackageIcon>logcorner.png</PackageIcon>
    <PackageReadmeFile>README.md</PackageReadmeFile>
    <PackageTags>cqrs;event driven;serialization;</PackageTags>
    <PackageReleaseNotes>update package metadata</PackageReleaseNotes>
  </PropertyGroup>

So every time, the project is build , a package should be generated, Now I have to pubish the package in the next step

Publish Packages 

To pubish the package to github, I have to create an account https://www.nuget.org/ and create an API Key as following

Because I will publish the package during the build process, I must create a service connection in azure devops (https://dev.azure.com/ ) and fill the FeedUrl and AoiKey accordingly.

The steps to create an azure devops pipemine are discussed here https://logcorner.com/building-microservices-through-event-driven-architecture-part12-continuous-integration/

Here is the final build configuration file

resources:
  repositories:
  - repository: self
    type: git
    ref: develop
jobs:
- job: Job_1
  displayName: Agent job 1
  pool: 
    name: LOGCORNER-POOL
  steps:
  - checkout: self
  - task: DotNetCoreCLI@2
    displayName: dotnet restore
    inputs:
      command: restore
      projects: '**/*.csproj'
  - task: DotNetCoreCLI@2
    displayName: dotnet build
    inputs:
      projects: '**/*.csproj'
  - task: VSBuild@1
    displayName: database build
    inputs:
      solution: '**\*.sqlproj'
  - task: DotNetCoreCLI@2
    displayName: dotnet test
    inputs:
      command: test
      projects: '**/*Unit[Tt]ests/*.csproj'
  - task: DotNetCoreCLI@2
    displayName: dotnet pack
    inputs:
      command: 'pack'
      packagesToPack: 'src/LogCorner.EduSync.Speech.SharedKernel/LogCorner.EduSync.Speech.SharedKernel.csproj'
      packDirectory: '$(Build.ArtifactStagingDirectory)/Nugets'
      nobuild: true
      versioningScheme: 'off'
  
  - task: NuGetCommand@2
    displayName: NuGet push
    inputs:
      command: 'push'
      packagesToPush: '$(Build.ArtifactStagingDirectory)/Nugets/*.nupkg'
      nuGetFeedType: 'external'
      publishFeedCredentials: 'nuget.org'
      allowPackageConflicts: true
    continueOnError: true
...

When I update a shared library and push the code to the github repository , azure devops will trigger a build, pack and publish the package to nuget.org . As a result, a new version of the package is publicly available for demos but it should be private in a production scenario.

Code source is available here : 

• https://github.com/logcorner/LogCorner.EduSync.Speech.Command/tree/master/src/LogCorner.EduSync.Speech.SharedKernel

Thanks for reading, if you have any feedback, feel free to post it