ARM模板中Function App appsettings循环配置失败排查

问题场景 #

在嵌套ARM模板中尝试使用copy循环为Function App的appsettings添加自定义配置项，未使用copy时部署正常，使用copy后触发部署失败，错误信息如下：

{"code":"DeploymentFailed","message":"At least one resource deployment operation failed. Please list deployment operations for details. Please see https://aka.ms/arm-deployment-operations for usage details.","details":[{"message":"The parameter properties has an invalid value."}]}

对应的问题模板代码片段：

"resources": [
  {
    "type": "Microsoft.Web/sites/config",
    "apiVersion": "2020-06-01",
    "name": "[concat(parameters('functionAppName'),'/appsettings')]",
    "properties": {
      "FUNCTIONS_EXTENSION_VERSION": "~4",
      "WEBSITE_NODE_DEFAULT_VERSION": "6.5.0",
      "WEBSITE_RUN_FROM_PACKAGE": "1",
      "FUNCTIONS_WORKER_RUNTIME": "powershell",
      "FUNCTIONS_WORKER_RUNTIME_VERSION": "~7",
      "OperationalLogType": "OperationalRecord",
      "AuditLogType": "AuditRecord",
      "copy": [
        {
          "name": "copy1",
          "count": 3,
          "input": {
             "name": "[concat('customentry-', copyIndex('copy1'))]"
               }
        }
      ]
    },
    "dependsOn": []
  }
],

错误原因 #

1. copy循环使用方式违规：ARM模板不支持直接在properties对象内部嵌套copy数组来生成配置项，这种写法不符合ARM对对象属性动态生成的语法规范，直接破坏了properties的参数结构有效性。
2. 配置项结构不符合API要求：Function App的appsettingsproperties要求是扁平的键值对结构（"配置键": "配置值"），但你在input中定义的是包含name字段的嵌套对象，生成的结构与API预期完全不匹配，触发了参数无效的报错。

修正方案 #

要动态生成appsettings配置项，需通过ARM模板函数将原有固定配置与动态生成的键值对合并，推荐使用union结合createObject函数实现：

"resources": [
  {
    "type": "Microsoft.Web/sites/config",
    "apiVersion": "2020-06-01",
    "name": "[concat(parameters('functionAppName'),'/appsettings')]",
    "properties": "[union(
      {
        \"FUNCTIONS_EXTENSION_VERSION\": \"~4\",
        \"WEBSITE_NODE_DEFAULT_VERSION\": \"6.5.0\",
        \"WEBSITE_RUN_FROM_PACKAGE\": \"1\",
        \"FUNCTIONS_WORKER_RUNTIME\": \"powershell\",
        \"FUNCTIONS_WORKER_RUNTIME_VERSION\": \"~7\",
        \"OperationalLogType\": \"OperationalRecord\",
        \"AuditLogType\": \"AuditRecord\"
      },
      createObject(
        range(0, 3),
        concat('customentry-', copyIndex()),
        // 此处可自定义配置项的值，比如copyIndex()、固定字符串或其他变量
        "default-value"
      )
    )]",
    "dependsOn": []
  }
]

内容的提问来源于stack exchange，提问作者Korman