Azure Functions新增Event Hub输出绑定后应用关闭无法写入数据

问题场景 #

开发Azure应用函数实现从源Event Hub读取数据，处理后写入目标Event Hub。初始仅实现读取+日志打印逻辑时函数可正常运行，新增Event Hub输出绑定后发布到云端，出现应用启动后自动关闭、无法写入数据的问题。

初始可正常运行的代码 #

[FunctionName("EHFunction")]
public static async Task Run(
    [EventHubTrigger("ehquery", Connection = "EventHubConnectionString")] EventData[] events,
    ILogger log)
{
    var exceptions = new List<Exception>();

    foreach (EventData eventData in events)
    {
        try
        {
            // Read event hub event which contains link to a blob with messages. Read messages from the blob storage endpoint.

            foreach (var blobEntry in blobData)
            {
                foreach (var record in blobEntry.Records)
                {
                    var recordStr = record.ToString();
                    log.LogInformation($"Record: {recordStr}");
                }
            }
        }
        catch (Exception e)
        {
            // We need to keep processing the rest of the batch - capture this exception and continue.
            // Also, consider capturing details of the message that failed processing so it can be processed again later.
            log.LogCritical(e.Message);
            exceptions.Add(e);
        }
    }
}

新增输出绑定后的问题代码 #

[FunctionName("EHFunction")]
public static async Task Run(
    [EventHubTrigger("ehquery", Connection = "EventHubConnectionString")] EventData[] events,
    [EventHub("ehquery-output", Connection = "EventHubOutputConnectionAppSetting")] IAsyncCollector<string> outputEvents,
    ILogger log)
{
    var exceptions = new List<Exception>();

    foreach (EventData eventData in events)
    {
        try
        {
            // Read event hub event which contains link to a blob with messages. Read messages from the blob storage endpoint.

            foreach (var blobEntry in blobData)
            {
                foreach (var record in blobEntry.Records)
                {
                    var recordStr = record.ToString();
                    await outputEvents.AddAsync(recordStr);
                }
            }
        }
        catch (Exception e)
        {
            // We need to keep processing the rest of the batch - capture this exception and continue.
            // Also, consider capturing details of the message that failed processing so it can be processed again later.
            log.LogCritical(e.Message);
            exceptions.Add(e);
        }
    }
}

云端异常日志 #

<EventData>
<Data>Application 'C:\Program Files (x86)\SiteExtensions\Functions\3.7.1\64bit\' started successfully.</Data>
<Data>Process Id: 3776.</Data>
<Data>File Version: 13.1.22054.23. Description: IIS ASP.NET Core Module V2 Request Handler. Commit: 509f6badec2f3162f0e50330cd9107e5624b379b</Data>
</EventData>
</Event>
<EventData>
<Data>Application 'MACHINE/WEBROOT/APPHOST/EHFunction' has shutdown.</Data>
<Data>Process Id: 4624.</Data>
<Data>File Version: 13.1.22054.23. Description: IIS ASP.NET Core Module V2 Request Handler. Commit: 509f6badec2f3162f0e50330cd9107e5624b379b</Data>
</EventData>
</Event>

本地配置参考 #

{
    "IsEncrypted": false,
  "Values": {
    "AzureWebJobsStorage": "UseDevelopmentStorage=true",
    "EventHubConnectionString": "Endpoint=sb://{inputeventhubconnectionstring}",
    "EventHubOutputConnectionAppSetting": "Endpoint=sb://{outputeventhubconnectionstring}",
    "FUNCTIONS_WORKER_RUNTIME": "dotnet"
  }
}

问题根因 #

一共4个核心错误，直接导致函数启动失败、无法写入：

• 配置未同步到云端环境：local.settings.json 仅用于本地开发调试，发布函数时不会自动把该文件内的配置同步到Azure云端的函数应用配置中。云端运行时找不到对应的连接字符串配置，会直接触发启动失败、进程退出。
• 存储配置不适配云端环境：本地配置中AzureWebJobsStorage的值为UseDevelopmentStorage=true，这是本地Azure存储模拟器的专用配置，云端环境无法访问本地模拟器，函数运行时缺少必须的存储依赖会直接关闭。
• 连接字符串权限/配置不匹配：输出Event Hub的连接字符串需要具备发送权限，如果连接字符串未携带EntityPath参数，需要确保[EventHub]绑定特性中配置的Hub名称（ehquery-output）和实际目标Event Hub名称完全一致，否则会出现鉴权失败、写入报错。
• 代码逻辑缺失：所有事件处理完成后没有判断收集到的异常列表，也没有触发输出收集器的最终刷新，即使写入过程出现错误也不会触发重试，容易出现消息丢失。

修复方案 #

1. 登录Azure门户，进入目标函数应用的「配置」-「应用程序设置」页面，新增/更新以下配置项：
   • AzureWebJobsStorage：替换为Azure标准存储账号的连接字符串，不能保留本地开发存储的配置值
   • EventHubConnectionString：填入源Event Hub的连接字符串，确保具备监听权限，建议拼接EntityPath=ehquery参数
   • EventHubOutputConnectionAppSetting：填入目标Event Hub的连接字符串，确保具备发送权限，如果连接字符串未携带EntityPath，确认目标Hub名称和绑定中配置的ehquery-output完全一致
2. 补全代码逻辑：在所有事件循环处理完成后，增加异常判断和输出刷新逻辑，参考如下：

   // 所有事件循环结束后新增
   await outputEvents.FlushAsync();
   if (exceptions.Any())
   {
       throw new AggregateException(exceptions);
   }
   

3. 保存配置后重启函数应用，通过实时日志流观察运行状态，确认是否存在剩余的鉴权、网络访问类错误。

内容的提问来源于stack exchange，提问作者Gengis Khan