【Azure 应用服务】Azure Function集成虚拟网络，设置被同在虚拟网络中的Storage Account触发，遇见Function无法触发的问题

一切为了安全，所有的云上资源如支持内网资源访问，则都可以加入虚拟网络

问题描述

使用Azure Function处理Storage Account中Blob 新增，更新，删除等情况。Storage Account启用虚拟网络中的服务终结点(Service Endpoint)后，可以实现只能从内网访问。同时，Azure Function也支持集成内网。并且可支持在虚拟网络中被Storage Account所触发。所以根据门户中一步一步的操作，配置完Azure Function和Storage Account的Virtul Network后，发现Function无法启动。在日志中发现问题是：

2021-06-30T10:56:00.895 [Error] An unhandled exception has occurred. Host is shutting down.
Microsoft.Azure.Storage.StorageException : This request is not authorized to perform this operation.
   at async Microsoft.Azure.Storage.Core.Executor.Executor.ExecuteAsync[T](RESTCommand`1 cmd,IRetryPolicy policy,OperationContext operationContext,CancellationToken token)
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at async Microsoft.Azure.WebJobs.Extensions.Storage.TimeoutHandler.ExecuteWithTimeout[T](String operationName,String clientRequestId,IWebJobsExceptionHandler exceptionHandler,ILogger logger,CancellationToken cancellationToken,Func`1 operation) at C:\projects\azure-webjobs-sdk-rqm4t\src\Microsoft.Azure.WebJobs.Extensions.Storage\TimeoutHandler.cs : 56
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at async Microsoft.Azure.WebJobs.Host.Queues.Listeners.QueueListener.ExecuteAsync(CancellationToken cancellationToken) at C:\projects\azure-webjobs-sdk-rqm4t\src\Microsoft.Azure.WebJobs.Extensions.Storage\Queues\Listeners\QueueListener.cs : 201
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at async Microsoft.Azure.WebJobs.Host.Timers.TaskSeriesTimer.RunAsync(CancellationToken cancellationToken) at C:\projects\azure-webjobs-sdk-rqm4t\src\Microsoft.Azure.WebJobs.Host\Timers\TaskSeriesTimer.cs : 147
2021-06-30T10:56:00.921 [Information] Stopping JobHost
2021-06-30T10:56:00.921 [Information] Stopping the listener 'Microsoft.Azure.WebJobs.Host.Listeners.CompositeListener' for function 'BlobTrigger1'
2021-06-30T10:56:00.942 [Information] Stopped the listener 'Microsoft.Azure.WebJobs.Host.Listeners.CompositeListener' for function 'BlobTrigger1'
2021-06-30T10:56:00.943 [Information] Job host stopped

（日志可通过高级工具Kudu获取：Kudu地址为：https://<your function app name>.scm.chinacloudsites.cn/DebugConsole 日志路径为：D:\home\LogFiles\Application\Functions\Host\xxxxxxxx.log)

问题分析

根据日志发现了：

1） Function Host遇见了异常，导致它被关闭.

2）异常的原因是因为访问Storage没有权限 （Microsoft.Azure.Storage.StorageException : This request is not authorized to perform this operation.）

那么问题根源就出现在Azure Function访问Stroage时，走的是公网访问，而公网的访问在Storage中式拒绝的。所以要修改Funciton的配置，让其通过内网的形式访问Storage。在查看官方说明文档后，有发现两个非常重要的配置：

• WEBSITE_VNET_ROUTE_ALL：设置为1。它会将Azure Function的所有出站调用发送到 VNet。
• WEBSITE_DNS_SERVER：默认值为168.63.129.16。用与虚拟网络集成时，它将使用与虚拟网络相同的 DNS 服务器。 函数应用需要此设置才能与 Azure DNS 专用区域配合使用。 此设置和 WEBSITE_VNET_ROUTE_ALL 会将应用中的所有出站调用发送到虚拟网络。

问题解决

在Azure Funciton的设置页面，添加WEBSITE_VNET_ROUTE_ALL和WEBSITE_DNS_SERVER两个参数，配置如下：

修改完成后，再次查看Function Host的启动日志，就可见 “Loading functions metadata” 和 “1 functions loaded”等消息。这就表明，Function Host启动成功。

2021-06-30T10:57:00.006 [Information] Initializing Warmup Extension.
2021-06-30T10:57:00.069 [Information] Initializing Host. OperationId: '93cf4ed0-d598-4308-9241-dca5ba6a55ee'.
2021-06-30T10:57:00.073 [Information] Host initialization: ConsecutiveErrors=0, StartupCount=1, OperationId=93cf4ed0-d598-4308-9241-dca5ba6a55ee
2021-06-30T10:57:00.106 [Information] LoggerFilterOptions
{
  "MinLevel": "None",
  "Rules": [
    {
      "ProviderName": null,
      "CategoryName": null,
      "LogLevel": null,
      "Filter": "<AddFilter>b__0"
    },
    {
      "ProviderName": "Microsoft.Azure.WebJobs.Script.WebHost.Diagnostics.SystemLoggerProvider",
      "CategoryName": null,
      "LogLevel": "None",
      "Filter": null
    },
    {
      "ProviderName": "Microsoft.Azure.WebJobs.Script.WebHost.Diagnostics.SystemLoggerProvider",
      "CategoryName": null,
      "LogLevel": null,
      "Filter": "<AddFilter>b__0"
    }
  ]
}
2021-06-30T10:57:00.107 [Information] FunctionResultAggregatorOptions
{
  "BatchSize": 1000,
  "FlushTimeout": "00:00:30",
  "IsEnabled": true
}
2021-06-30T10:57:00.107 [Information] SingletonOptions
{
  "LockPeriod": "00:00:15",
  "ListenerLockPeriod": "00:00:15",
  "LockAcquisitionTimeout": "10675199.02:48:05.4775807",
  "LockAcquisitionPollingInterval": "00:00:05",
  "ListenerLockRecoveryPollingInterval": "00:01:00"
}
2021-06-30T10:57:00.107 [Information] QueuesOptions
{
  "BatchSize": 16,
  "NewBatchThreshold": 8,
  "MaxPollingInterval": "00:00:02",
  "MaxDequeueCount": 5,
  "VisibilityTimeout": "00:00:00"
}
2021-06-30T10:57:00.107 [Information] BlobsOptions
{
  "CentralizedPoisonQueue": false
}
2021-06-30T10:57:00.108 [Information] Starting JobHost
2021-06-30T10:57:00.110 [Information] Starting Host (HostId=lbfunctionforvnet01, InstanceId=05efd41a-013d-428c-b839-fb4b69127366, Version=3.0.15733.0, ProcessId=5480, AppDomainId=1, InDebugMode=True, InDiagnosticMode=False, FunctionsExtensionVersion=~3)
2021-06-30T10:57:00.121 [Information] Loading functions metadata
2021-06-30T10:57:00.137 [Information] 1 functions loaded
2021-06-30T10:57:01.348 [Information] Generating 1 job function(s)
2021-06-30T10:57:01.373 [Information] Found the following functions:
Host.Functions.BlobTrigger1

最后在Storage Blob中上传文件进行测试，Function能成功被触发及获取到正确的Blob信息

2021-06-30T11:02:22.273 [Information] Executing 'Functions.BlobTrigger1' (Reason='New blob detected: samples-workitems/local_error.log', Id=79bc13b9-5aed-487f-b5de-02bb4ff7b8c6)
2021-06-30T11:02:22.276 [Information] Trigger Details: MessageId: f6dd9893-f6c6-41af-a469-f6b2e21e09bc, DequeueCount: 1, InsertionTime: 2021-06-30T11:02:22.000+00:00, BlobCreated: 2021-06-30T11:02:13.000+00:00, BlobLastModified: 2021-06-30T11:02:13.000+00:00
2021-06-30T11:02:22.283 [Information] C# Blob trigger function Processed blob
 Name:local_error.log
 Size: 420588 Bytes
2021-06-30T11:02:22.291 [Information] Executed 'Functions.BlobTrigger1' (Succeeded, Id=79bc13b9-5aed-487f-b5de-02bb4ff7b8c6, Duration=37ms)

参考资料

具有虚拟网络触发器的高级计划 ：https://docs.azure.cn/zh-cn/azure-functions/functions-networking-options#premium-plan-with-virtual-network-triggers

配置函数应用设置：https://docs.azure.cn/zh-cn/azure-functions/functions-create-vnet#configure-your-function-app-settings