How to setup devops for build-once, but for multiple environments

Question

I am trying to improve our build/release process as work, but I have hit a snag, and I am not sure if it's because of trying to do the impossible, or just me not grasping some concepts.

As source we have a C# asp.net application with four appsettings-files for different environments. The appsettings are the default appsettings.json, appsettings.development.json, appsettings.test.json, and appsettings.release.json

Our environments are 'dev' which is a local developers PC, 'test' which is a test-server located onprem, and 'release' is also onprem but on a public-facing server. Later on the release-server will be in azure as a webapp. So it's nice to do this in a way that is compatible with Azure.

Ideally I want to have a build-once system where I build the code and generate artifacts, and just promote the artifacts from dev to test and finally release.

Is this a decent way to to this; I remove all appsettings files except appsettings.json, and add one build-pipeline to build it, and then make multiple release-pipelines, one pipeline per environment, each with a plethora of variables to configure the appsettings.json file to match the environment it will be deployed to?

Ideally I would like to keep the different appsettings files so all changes to the environments are configured there, but I realize that the way the appsettings files are manipulated on build means that won't work.

Hoping for some input so I can start setup this up. And thanks in advance.

Answer 1

Based on your requirement, you need to keep one appsettings.json file in the project and use multiple pipeline variables to configure the appsettings.json file based on the environment.

This is a common situation in CI/CD deployments.

To meet your requirement, I suggest that you can use the built-in task: File Transform task in each pipelines to replace the value in the Appsettings.json file.

Here is an example:

Appsettings.json

{
  "Data": {
    "DefaultConnection": {
      "ConnectionString": "Data Source=(LocalDb)\\MSDB;AttachDbFilename=aspcore-local.mdf;"
    },
    "DebugMode": "enabled",
    "DBAccess": {
      "Administrators": ["Admin-1", "Admin-2"],
      "Users": ["Vendor-1", "vendor-3"]
    },
    "FeatureFlags": {
      "Preview": [
        {
          "newUI": "AllAccounts"
        },
        {
          "NewWelcomeMessage": "Newusers"
        }
      ]
    }
  }
}

Set the Pipeline variables and use File Transform task:

variables:
  Data.DebugMode: disabled
  Data.DefaultConnection.ConnectionString: 'Data Source=(prodDB)\MSDB;AttachDbFilename=prod.mdf;'
  Data.DBAccess.Users.0: Admin-3
  Data.FeatureFlags.Preview.1.NewWelcomeMessage: AllAccounts

# Update appsettings.json via FileTransform task.
- task: FileTransform@2
  displayName: 'File transformation: appsettings.json'
  inputs:
    folderPath: '$(Build.ArtifactStagingDirectory)/$(Build.BuildId).zip'
    targetFiles: '**/appsettings.json'
    fileType: json

For more detailed info, you can refer to this doc: JSON variable substitution