Azure DevOps Use a Variable as a Condition between Deployment Stages - azure

Question

I currently build all our Azure Infrastructure using Terraform via Azure DevOps Pipelines. This has been working well and we have a standard pipeline which calls two templates
Plan Stage
Deployment Job
Planning Template
Runs Every Time
Apply Stage
Deployment Job
Apply Template
Runs with manual approval check
Now this works fine, but what I want to do is only have the apply step run if there are changes to make. I have found other articles on how to get a variable set in the plan stage which I can do and it works fine.
I can call this same variable in the next step
variables:
varFromPlanStage: $[stageDependencies.Plan.planning_stage.outputs['planning_stage.terraformPlanResult.terraformChanges']]
steps:
- script: echo $(varFromPlanStage)
But the problem comes in when I try and use this same variable in a condition.
I found that the way you all it is different, needing a dependency instead of stagedependancy, but no matter what I try I can't get it to work.
The pipeline looks like this.
stages:
- stage: 'Plan'
displayName: 'Planning'
jobs:
- deployment: planning_stage
displayName: 'Planning Changes'
pool:
vmImage: 'Ubuntu-20.04'
environment: 'planning'
strategy:
runOnce:
deploy:
steps:
- template: /Pipelines/10-TEST-terraform-planning-template.yml # Run the Planning Template
parameters:
terraform_version: ${{ parameters.terraform_version }}
terraform_backend_service_arm: ${{ parameters.terraform_backend_service_arm }}
terraform_backend_resource_group: ${{ parameters.terraform_backend_resource_group }}
terraform_backend_storage_account: ${{ parameters.terraform_backend_storage_account }}
terraform_backend_storage_container: ${{ parameters.terraform_backend_storage_container }}
terraform_state_key: ${{ parameters.terraform_state_key }}
git_working_directory: ${{ parameters.git_working_directory }}
# This is the Build Stage - Only do this when on the master branch (which is via a PR)
- stage: 'Apply'
condition: and(succeeded(), eq(dependencies.Plan.planning_stage.outputs['planning_stage.terraformPlanResult.terraformChanges'], 'true'))
variables:
varFromPlanStage: $[stageDependencies.Plan.planning_stage.outputs['planning_stage.terraformPlanResult.terraformChanges']]
displayName: 'Applying Changes'
jobs:
- deployment: applying_stage
displayName: 'Lets Build'
pool:
vmImage: 'Ubuntu-20.04'
environment: 'building'
strategy:
runOnce:
deploy:
steps:
- script: echo $(varFromPlanStage) # Just a test
- template: /Pipelines/20-TEST-terraform-apply-template.yml # Run the Apply Template
parameters:
terraform_version: ${{ parameters.terraform_version }}
terraform_backend_service_arm: ${{ parameters.terraform_backend_service_arm }}
terraform_backend_resource_group: ${{ parameters.terraform_backend_resource_group }}
terraform_backend_storage_account: ${{ parameters.terraform_backend_storage_account }}
terraform_backend_storage_container: ${{ parameters.terraform_backend_storage_container }}
terraform_state_key: ${{ parameters.terraform_state_key }}
git_working_directory: ${{ parameters.git_working_directory }}
And the part of the Planning Template that exports the variable is called terraformPlanResult with the var being terraformChanges
Any idea what I am doing wrong here, and why I can't call the variable as a condition but I can as part of the steps?
Thx!

Answer 1

This appears to work differently depending on whether you're setting the variable in a 'deployment' job, or a 'job' job. After some trial, error and googling I managed to get working for both. Examples below :-)
Example passing variables from a 'deployment' job.
# Example passing variables from a 'deployment' job.
stages:
# Create some variables to pass to next stage.
- stage: 'A'
jobs:
- deployment: 'A1'
pool:
vmImage: 'windows-2019'
environment: 'test'
strategy:
runOnce:
deploy:
steps:
# Create a variable.
- task: PowerShell#2
name: foo
displayName: 'Create a variable.'
inputs:
targetType: 'inline'
script: |
echo "##vso[task.setvariable variable=bar;isOutput=true]apple"
# Check variable.
- task: PowerShell#2
displayName: 'Check a variable.'
inputs:
targetType: 'inline'
script: |
Write-Host "$env:MY_MAPPED_ENV_VAR"
env:
MY_MAPPED_ENV_VAR: $(foo.bar)
# Confirm condition works & variables are available for use.
- stage: 'B'
dependsOn:
- 'A'
variables:
- name: varFromStageA
# stageDependencies.stageName.deploymentName.outputs['deploymentName.stepName.variableName']
value: $[ stageDependencies.A.A1.outputs['A1.foo.bar'] ]
# dependencies.stageName.outputs['deploymentName.deploymentName.stepName.variableName']
condition: and(succeeded(), eq(dependencies.A.outputs['A1.A1.foo.bar'], 'apple'))
jobs:
- job: 'B1'
pool:
vmImage: 'windows-2019'
steps:
# Confirm variable has been passed between stages.
- task: PowerShell#2
displayName: 'Confirm var passed between stages'
inputs:
targetType: 'inline'
script: |
Write-Host "$env:MY_MAPPED_ENV_VAR"
env:
MY_MAPPED_ENV_VAR: $(varFromStageA)
Example passing variables from a 'job' job.
# Example passing variables from a 'job' job.
stages:
# Create some variables to pass to next stage.
- stage: 'A'
jobs:
- job: 'A1'
pool:
vmImage: 'windows-2019'
steps:
# Create a variable.
- task: PowerShell#2
name: foo
displayName: 'Create a variable.'
inputs:
targetType: 'inline'
script: |
echo "##vso[task.setvariable variable=bar;isOutput=true]apple"
# Check variable.
- task: PowerShell#2
displayName: 'Check a variable.'
inputs:
targetType: 'inline'
script: |
Write-Host "$env:MY_MAPPED_ENV_VAR"
env:
MY_MAPPED_ENV_VAR: $(foo.bar)
# Confirm condition works & variables are available for use.
- stage: 'B'
dependsOn:
- 'A'
variables:
- name: varFromStageA
# stageDependencies.stageName.jobName.outputs['stepName.variableName']
value: $[ stageDependencies.A.A1.outputs['foo.bar'] ]
# dependencies.stageName.outputs['jobName.stepName.variableName']
condition: and(succeeded(), eq(dependencies.A.outputs['A1.foo.bar'], 'apple'))
jobs:
- job: 'B1'
pool:
vmImage: 'windows-2019'
steps:
# Confirm variable has been passed between stages.
- task: PowerShell#2
displayName: 'Confirm var passed between stages'
inputs:
targetType: 'inline'
script: |
Write-Host "$env:MY_MAPPED_ENV_VAR"
env:
MY_MAPPED_ENV_VAR: $(varFromStageA)

Answer 2

What's working for me (by many trials and errors) is the format:
dependencies.stage_name.outputs['job_name.step_name.variable_name']
In your case, this would be:
dependencies.Plan.outputs['planning_stage.terraformPlanResult.terraformChanges']
If that doesn't work, the only unusual thing is that your planning_stage is a deployment. You might try and change it to a regular job.
Here's a pipeline that tests various ways of referencing outputs in conditions.

Answer 3

For me it looks like an issue on Azure Devops (later O will preapre minimial working example and create a bug for this). Because the same syntax works correctly for regular jobs but not for deployment. Also you can use condition like condition: in(dependencies.A.result, 'Succeeded', 'SucceededWithIssues', 'Skipped') but not outputs. And according to this
"dependencies": {
"<STAGE_NAME>" : {
"result": "Succeeded|SucceededWithIssues|Skipped|Failed|Canceled",
"outputs": {
"jobName.stepName.variableName": "value"
}
},
"...": {
// another stage
}
}
it is correct syntax.
I also checked this but using life cycle hook instead of job name doesn't helped me.
What is trange that you can use output variables in job condition if ther are in the same stage.
Here is link to the issue.