ARM增量部署模式下Azure函数应用配置修改的部署行为问询

问题描述 #

我通过以下YAML任务创建了包含应用设置和函数的Azure Function App：

- task: AzureResourceManagerTemplateDeployment@3
  displayName: 'deploy resources'
  inputs:
    azureResourceManagerConnection: azureResourceManagerConnection
    subscriptionId: subscriptionId
    resourceGroupName: rg
    location: location
    csmFile: template.bicep
    csmParametersFile: parameters.json              
    deploymentMode: 'Incremental'

现在我修改了应用设置，若以Incremental部署模式运行上述任务，是会重建带有修改后设置的Function App（包含函数），还是仅更新应用设置，函数应用及现有函数保持不变？

我的template.bicep及相关模块内容如下：

var appSettings = [
  {
    name: 'WEBSITE_ADD_SITENAME_BINDINGS_IN_APPHOST_CONFIG'
    value: 1
  }
  {
    name: 'WEBSITE_ENABLE_SYNC_UPDATE_SITE'
    value: 1
  }
  {
    name: 'SCM_TOUCH_WEBCONFIG_AFTER_DEPLOYMENT'
    value: 0
  }
  {
    name: 'APPINSIGHTS_INSTRUMENTATIONKEY'
    value: reference(resourceId(appInsightsResourceGroup, 'microsoft.insights/components/', appInsightsName), '2015-05-01').InstrumentationKey
  }
  {
    name: 'AzureWebJobsStorage'
    value: 'DefaultEndpointsProtocol=https;AccountName=${storageAccountName};AccountKey=${listKeys(resourceId(storageAccountResourceGroup, 'Microsoft.Storage/storageAccounts', storageAccountName), providers('Microsoft.Storage', 'storageAccounts').apiVersions[0]).keys[0].value}'
  }
  {
    name: 'WEBSITE_CONTENTAZUREFILECONNECTIONSTRING'
    value: 'DefaultEndpointsProtocol=https;AccountName=${storageAccountName};AccountKey=${listKeys(resourceId(storageAccountResourceGroup, 'Microsoft.Storage/storageAccounts', storageAccountName), providers('Microsoft.Storage', 'storageAccounts').apiVersions[0]).keys[0].value}'
  }
  {
    name: 'FUNCTIONS_WORKER_RUNTIME'
    value: 'dotnet'
  }
  {
    name: 'FUNCTIONS_EXTENSION_VERSION'
    value: '~4'
  }
  {
    name: 'WEBSITE_MAX_DYNAMIC_APPLICATION_SCALE_OUT'
    value: maximumElasticWorkerCount
  }
  {
    name: 'appConfigurationEndpoint'
    value: appConfigurationEndpoint
  }
  {
    name: 'membershipStorageAccountName'
    value: '@Microsoft.KeyVault(SecretUri=${reference(membershipStorageAccountName, '2019-09-01').secretUriWithVersion})'
  }
  {
    name: 'membershipContainerName'
    value: '@Microsoft.KeyVault(SecretUri=${reference(membershipContainerName, '2019-09-01').secretUriWithVersion})'
  }
]

var stagingSettings = [
  {
    name: 'WEBSITE_CONTENTSHARE'
    value: toLower('functionApp-staging')
  }
  {
    name: 'AzureFunctionsJobHost__extensions__durableTask__hubName'
    value: '${solutionAbbreviation}compute${environmentAbbreviationStaging}'
  }
  {
    name: 'AzureWebJobs.StarterFunction.Disabled'
    value: 1
  }
]

var productionSettings = [
  {
    name: 'WEBSITE_CONTENTSHARE'
    value: toLower('functionApp')
  }
  {
    name: 'AzureFunctionsJobHost__extensions__durableTask__hubName'
    value: '${solutionAbbreviation}compute${environmentAbbreviation}'
  }
  {
    name: 'AzureWebJobs.StarterFunction.Disabled'
    value: 0
  }
]

module functionAppTemplate 'functionApp.bicep' = {
  name: 'functionAppTemplater'
  params: {
    name: '${functionAppName}'
    kind: functionAppKind
    location: location
    servicePlanName: servicePlanName
    dataKeyVaultName: dataKeyVaultName
    dataKeyVaultResourceGroup: dataKeyVaultResourceGroup
    secretSettings: union(appSettings, productionSettings)
  }
  dependsOn: [
    servicePlanTemplate
  ]
}

module functionAppSlotTemplate 'functionAppSlot.bicep' = {
  name: 'functionAppSlotTemplate'
  params: {
    name: '${functionAppName}/staging'
    kind: functionAppKind
    location: location
    servicePlanName: servicePlanName
    dataKeyVaultName: dataKeyVaultName
    dataKeyVaultResourceGroup: dataKeyVaultResourceGroup
    secretSettings: union(appSettings, stagingSettings)
  }
  dependsOn: [
    functionAppTemplate
  ]
}

functionApp.bicep：

resource functionApp 'Microsoft.Web/sites@2018-02-01' = {
  name: name
  location: location
  kind: kind
  properties: {
    serverFarmId: resourceId('Microsoft.Web/serverfarms', servicePlanName)
    clientAffinityEnabled: false
    httpsOnly: true
    siteConfig: {
      use32BitWorkerProcess : false
      appSettings: secretSettings
    }
  }
  identity: {
    type: 'SystemAssigned'
  }
}

functionAppSlot.bicep：

resource functionAppSlot 'Microsoft.Web/sites/slots@2018-11-01' = {
  name: name
  kind: kind
  location: location
  properties: {
    clientAffinityEnabled: true
    enabled: true
    httpsOnly: true
    serverFarmId: resourceId('Microsoft.Web/serverfarms', servicePlanName)
    siteConfig: {
      use32BitWorkerProcess : false
      appSettings: secretSettings
    }
  }
  identity: {
    type: 'SystemAssigned'
  }
}

回答 #

以Incremental模式运行部署任务时，只会更新应用设置，不会重建Function App，现有函数也会保持不变，原因如下：

1. 增量部署模式的核心逻辑
   Incremental模式会对比Azure中已存在的资源与模板定义的资源，仅对存在差异的属性进行更新，不会删除或重建未变更的资源。你的模板中，Function App的核心属性（名称、服务计划关联、位置、身份配置等）均未修改，仅siteConfig.appSettings有变更，因此只会更新这部分设置。

2. 函数代码的存储独立性
   你的Function App通过WEBSITE_CONTENTSHARE和WEBSITE_CONTENTAZUREFILECONNECTIONSTRING配置使用文件共享存储函数代码，本次部署仅修改应用设置，未触及代码存储相关的配置或资源，因此已部署的函数代码不会被覆盖或删除，会完整保留。

3. Bicep模板的设置更新规则
   模板中的Microsoft.Web/sites资源定义仅更新appSettings数组，Azure资源管理器会将模板中的设置与现有设置合并（注意：若模板中移除了某个设置，Incremental模式下该设置会被保留；若要删除设置，需要显式在模板中声明移除）。

内容的提问来源于stack exchange，提问作者user989988