Azure Pipeline中基于目录更新条件运行模板的问题排查

问题 #

我想在Azure Pipeline中根据提交记录是否更新特定目录，条件运行Terraform模板，但两种配置都失败了：

配置1：同一Job内使用${{ if }}表达式，变量始终判定为false #

- stage: Provision_Central_Techops
  dependsOn: [] 
  
  displayName: Provision Central Techops
  jobs:
  
  - job: Provision_TechOps_Central_Stack
    displayName: Provision TechOps Central Stack
    variables:
      workingDirectory: terraform/stacks/techops
     
    steps:
    - bash: |
        
              echo workingDirectory $(workingDirectory)
              
              if git diff-tree --no-commit-id --name-only -r HEAD | grep -q $(workingDirectory); then

                echo "##vso[task.setvariable variable=techopsUpdated]true"
                
              else

                echo "##vso[task.setvariable variable=techopsUpdated]false"
                
              fi
              
                
      name: Check_For_Update
    
    - ${{ if eq(variables.techopsUpdated, true) }}:
      - template: steps/terraform.yml
       
        parameters:
          environment: prod
          workingDirectory: $(workingDirectory)
          stackName: techops
          terraformVersion: $(terraformVersion)
    - ${{ else }}:
      - script: echo "techopsUpdated $(techopsUpdated)"

配置2：拆分Job后，条件判断时输出变量为null #

- stage: Provision_Central_Techops
  dependsOn: [] 
  
  displayName: Provision Central Techops
  jobs:
  
  - job: Provision_TechOps_Central_Stack1
    displayName: Provision TechOps Central Stack
    variables:
      workingDirectory: terraform/stacks/techops
    
   
    steps:
    - bash: |
        
              echo workingDirectory $(workingDirectory)
              
              if git diff-tree --no-commit-id --name-only -r HEAD | grep -q $(workingDirectory); then

                echo "##vso[task.setvariable variable=techopsUpdated; isOutput=true]true"
                
              else

                echo "##vso[task.setvariable variable=techopsUpdated; isOutput=true]false"
                
              fi
              
                
      name: Check_For_Update
  
  - job: Provision_TechOps_Central_Stack
    
    condition: eq(variables.techopsUpdated , true)
    displayName: Provision TechOps Central Stack
    variables:
      workingDirectory: terraform/stacks/techops
   
    steps:

    
    - template: steps/terraform.yml       
      parameters:
          environment: prod
          workingDirectory: $(workingDirectory)
          stackName: techops
          terraformVersion: $(terraformVersion)

原因分析与修复方案 #

针对配置1的问题 #

${{ if }}是编译时表达式，Azure Pipeline会在运行前就解析这个表达式，但你通过bash任务设置的techopsUpdated是运行时变量，编译阶段这个变量还未生成，所以表达式会默认判定为false。

修复方法：把编译时的${{ if }}替换为运行时的condition参数，给步骤添加动态条件判断：

- stage: Provision_Central_Techops
  dependsOn: [] 
  
  displayName: Provision Central Techops
  jobs:
  
  - job: Provision_TechOps_Central_Stack
    displayName: Provision TechOps Central Stack
    variables:
      workingDirectory: terraform/stacks/techops
     
    steps:
    - bash: |
        echo workingDirectory $(workingDirectory)
        if git diff-tree --no-commit-id --name-only -r HEAD | grep -q $(workingDirectory); then
          echo "##vso[task.setvariable variable=techopsUpdated]true"
        else
          echo "##vso[task.setvariable variable=techopsUpdated]false"
        fi
      name: Check_For_Update
    
    - template: steps/terraform.yml
      condition: eq(variables.techopsUpdated, 'true')
      parameters:
        environment: prod
        workingDirectory: $(workingDirectory)
        stackName: techops
        terraformVersion: $(terraformVersion)
    - script: echo "techopsUpdated $(techopsUpdated)"
      condition: ne(variables.techopsUpdated, 'true')

针对配置2的问题 #

你缺少两个关键配置：第二个Job未依赖第一个Job，且未正确引用前一个Job的输出变量。

修复后的配置：

- stage: Provision_Central_Techops
  dependsOn: [] 
  
  displayName: Provision Central Techops
  jobs:
  
  - job: Check_TechOps_Update
    displayName: Check if TechOps directory is updated
    variables:
      workingDirectory: terraform/stacks/techops
    
    steps:
    - bash: |
        echo workingDirectory $(workingDirectory)
        if git diff-tree --no-commit-id --name-only -r HEAD | grep -q $(workingDirectory); then
          echo "##vso[task.setvariable variable=techopsUpdated; isOutput=true]true"
        else
          echo "##vso[task.setvariable variable=techopsUpdated; isOutput=true]false"
        fi
      name: Check_For_Update
  
  - job: Provision_TechOps_Central_Stack
    dependsOn: Check_TechOps_Update
    condition: eq(variables.techopsUpdated, 'true')
    displayName: Provision TechOps Central Stack
    variables:
      workingDirectory: terraform/stacks/techops
      techopsUpdated: $[ dependencies.Check_TechOps_Update.outputs['Check_For_Update.techopsUpdated'] ]
   
    steps:
    - template: steps/terraform.yml       
      parameters:
        environment: prod
        workingDirectory: $(workingDirectory)
        stackName: techops
        terraformVersion: $(terraformVersion)

注意：输出变量的值为字符串类型，所以条件判断中要使用'true'而非布尔值true。

内容的提问来源于stack exchange，提问作者Nicholas Namacha