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cnp-azuredevops-libraries

Reusable pipeline components for CNP Azure DevOps pipelines

Terraform workflow templates

The template files below contain steps to add Terraform Init/Plan/Apply/Destroy tasks to a pipeline.

├── scripts
├── steps
│   └── terraform-precheck.yaml             # Precheck stage tasks
│   └── terraform.yaml                      # Terraform plan and apply stage tasks
├── tasks
├── vars

Reusing templates:

  1. Create the required folder structure in your repository

  2. Add the cnp-azure-devops-libraries repository resource as below

    resources:
  repositories:
  - repository: cnp-azuredevops-libraries
    type: github
    ref: refs/heads/master
    name: hmcts/cnp-azuredevops-libraries
    endpoint: 'hmcts (1)'

  3. Use the vars/input-variables.yaml template to add the common variables to your pipeline.

    Make sure you use the correct syntax when declaring a mixture of regular variables and templates, like below.

    Syntax example

    variables:
  # a regular variable
  - name: myvariable
    value: myvalue
  # a variable group
  - group: myvariablegroup
  # a reference to a variable template
  - template: myvariabletemplate.yml

    Full example

    variables:
  - name: timeoutInMinutes
    value: 60
  - name: agentPool
    value: ubuntu-latest
  - name: build
    value: $(Build.BuildNumber)
  - name: product
    value: cft-platform
  - name: terraformInitSubscription
    value: b8d29n39-8007-49m0-95b8-3c8691e90kb
  - template: vars/input-variables.yaml@cnp-azuredevops-libraries

    More information on the correct syntax when using regular variables, variables groups and templates.

  4. Add the terraform-precheck.yaml template to a Precheck stage

  5. Add the terraform.yaml template to a TerraformPlanApply stage

    see Example refactored pipeline

  6. First time pipeline run:

    • Run build with the Terraform plan option. State file will be created in new location
    • Copy state file from old location to overwrite new state file
    • Run build with Terraform plan to confirm plan reflects migrated state file

  7. Run pipeline with plan/apply option as required

State file:

  • In storage accounts in the HMCTS-CONTROL subscription
  • Storage account name derived from the resources subscription id as below:

    'c' + '1st-8th character of subscription id' + '25th-36th character of subscription id' + 'sa' e.g. 'cb72ab7b703b0f2c6a1bbsa'

  • Stored in the 'subscription-tfstate' storage container in the folder path derived as below:

    'location/product/build repo name/environment/component name/terraform.tfstate' e.g. 'UK South/cft-platform/azure-platform-terraform/sbox/shutter/terraform.tfstate'

Required terraform folder structure:

Template requires the below folder structure for the build repository.

Repo
├── components
│   └── <a> (e.g. network)                             # group of .tf files
│   │       └── .terraform-version (symlink)           # link to .terraform-version at root level (for local testing)
│   │       │                                            command: ln -s ../../.terraform-version .terraform-version
│   │       └── *.tf
│   └── <n>
├── environments                                       # Environment specific .tfvars files
│   └── <env>
│   │    └── *.tfvars
├── azure_pipeline.yaml
├── .terraform-version                                 # terraform version (read by tfenv)

Multiple regions

Some repositories have separate tfvars files based on region i.e. UK South or UK West and having all enviroment variables in a single tfvars file may not meet the requirement. If you need to use a different set of variables for your build then you can pass the multiRegion parameter and set this as true, the default is false.

Using multiple region support requires the below environments folder structure for the build repository.

Repo
├── environments                                       # Environment specific .tfvars files
│   └── <env>
│   │    └── <location>.tfvars                         # Region specific tfvars file without spaces e.g. prod-ukwest.tfvars

With this a different variable file will be used. An example can be found in the hub-panorama repo.

tfvars file location

Some repositories do not have the tfvars file in the standard location, or do not need tfvars file at all. In such cases, the tfVarsFile option can be used to specify this

a) Custom location of tfvars file

If tfvars file is in a non-standard location, the tfVarsFile option can be used to specify the full path of the tfvars file, as shown below

tfVarsFile: "$(System.DefaultWorkingDirectory)/$(buildRepoSuffix)/environments/network/${{ parameters.env }}.tfvars"

see example in aks-cft-deploy repo

b) No tfvars file

If the component does not need a tfvars file, then a special NULL string (all caps) can be specified for tfVarsFile, as shown below.

tfVarsFile: NULL

Note: This is different from the terraform reserved word null and is essentially a special string to indicate that no tfvars file is needed.

see example in aks-cft-deploy repo

Override components directory

In a monorepo, it may be needed to override the components folder if there's multiple applications that are built from the same repository. You can pass the baseDirectory option to specify the location of the components folder.

baseDirectory: "terraform/network/components"

Passing environment variables to terraform template:

You can pass environment variables directly to terraform tasks (plan, apply, destroy) Which then can be used as variable within terraform code as shown in below example:

- template: steps/terraform.yaml@cnp-azuredevops-libraries
  parameters:
    overrideAction: ${{ parameters.overrideAction }}
    environment: ${{ deployment.environment }}
    component: ${{ deployment.component }}
    serviceConnection: ${{ deployment.service_connection }}
    terraformInitSubscription: ${{ variables.terraformInitSubscription }}
    product: ${{ variables.product }}
    terraformEnvironmentVariables:
      TF_VAR_foo: $(bar)

In terraform you can then reference this variable as var.foo