如何在EventGrid触发的Azure Function事件中获取User ID

我有一个基于.NET7独立工作进程的EventGrid触发Azure Function，每当客户端连接SignalR hub时会被调用，代码如下：

[Function("v1-on-connectivity-events-changed")]
public async Task OnConnectivityEventsChangedAsync
(
    [EventGridTrigger]
    EventGridConnectivityEvent eventGridConnectivityEvent,
    FunctionContext functionContext
)
{
  _logger.LogWarning("Event grid trigger received. Data='{ConnectionInfo}'", JsonSerializer.Serialize(eventGridConnectivityEvent));
  ...
}

客户端通过Negotiate API连接SignalR的代码如下：

_hubConnection = new HubConnectionBuilder()
                .WithUrl(hubEndpoint.AbsoluteUri, options =>
                {
                    //  Adds the application token to the options' header.
                    options.AccessTokenProvider = () => Task.FromResult(user.IdentityToken.AccessToken)!;
                    options.Headers.Add("userSid", user.IdentityToken.UserSid);   
                })
                .Build();

...

await _hubConnection.StartAsync();

Negotiate函数返回包含额外参数的URL，代码如下：

[Function("negotiate")]
public Task<SignalRConnectionInfo> OnNegotiateAsync
(
    [HttpTrigger(AuthorizationLevel.Anonymous, "POST")]
    HttpRequestData httpRequestData,
    [SignalRConnectionInfoInput
    (
       HubName = Constants.HubName,
       ConnectionStringSetting = "AzureSignalRConnectionString"
    )]
    SignalRConnectionInfo signalRConnectionInfo
)
{
        return ExecuteAsync(httpRequestData, async claimsPrincipal =>
        {
            IUserPrincipal userPrincipal = await RetrieveClaimsAsync(httpRequestData, claimsPrincipal);

            signalRConnectionInfo.Url += $"&userSid={userPrincipal.UserSid}";
            
            return signalRConnectionInfo;
        });
    }

客户端连接时，OnConnectivityEventsChangedAsync函数可正常触发，但事件中缺少所需的User ID。根据SignalR文档，连接事件应同时提供User ID和Connection ID，而当前收到的事件数据如下：

{
    "Id":"56f3ab25-11d7-41d6-acbb-8429a741d746",
"Topic":"/subscriptions/<subscription_id>/resourceGroups/<resource_group>/providers/Microsoft.SignalRService/SignalR/<signalr_instance>",
    "Subject":"hub/updates",
    "EventType":"Microsoft.SignalRService.ClientConnectionConnected",
    "EventTime":"2022-11-27T19:22:19.2349923Z",
    "Data": { 
         "timestamp":"2022-11-27T19:22:19.2349923Z",
         "hubName":"updates",
         "connectionId":"gmJM_GHVkXsQuS5C1LhdXXXXX"
    }
}

请问如何在事件中同时获取User ID和Connection ID？

要让Azure SignalR的Event Grid事件包含User ID，需确保协商阶段正确关联用户标识，而非仅手动拼接URL参数，具体操作如下：

• 通过SignalRConnectionInfoInput绑定设置用户标识
  修改Negotiate函数的SignalRConnectionInfoInput属性，添加UserId绑定表达式，直接从请求头或令牌声明中获取用户ID。示例中从请求头的userSid字段获取：

  [SignalRConnectionInfoInput
  (
     HubName = Constants.HubName,
     ConnectionStringSetting = "AzureSignalRConnectionString",
     UserId = "{headers.userSid}"
  )]
  SignalRConnectionInfo signalRConnectionInfo
  

  此操作会让Azure SignalR服务自动将用户ID与连接关联，后续连接事件将携带该字段。

• 移除手动拼接URL的代码
  无需再手动给signalRConnectionInfo.Url追加userSid参数，因为UserId绑定已完成用户标识关联。修改后的Negotiate核心代码如下：

  [Function("negotiate")]
  public Task<SignalRConnectionInfo> OnNegotiateAsync
  (
      [HttpTrigger(AuthorizationLevel.Anonymous, "POST")]
      HttpRequestData httpRequestData,
      [SignalRConnectionInfoInput
      (
         HubName = Constants.HubName,
         ConnectionStringSetting = "AzureSignalRConnectionString",
         UserId = "{headers.userSid}"
      )]
      SignalRConnectionInfo signalRConnectionInfo
  )
  {
          return ExecuteAsync(httpRequestData, async claimsPrincipal =>
          {
              IUserPrincipal userPrincipal = await RetrieveClaimsAsync(httpRequestData, claimsPrincipal);
              return signalRConnectionInfo;
          });
      }
  

• 验证事件数据
  完成修改后，客户端重新连接，Event Grid触发的事件数据将新增userId字段，示例如下：

  {
      "Id":"56f3ab25-11d7-41d6-acbb-8429a741d746",
  "Topic":"/subscriptions/<subscription_id>/resourceGroups/<resource_group>/providers/Microsoft.SignalRService/SignalR/<signalr_instance>",
      "Subject":"hub/updates",
      "EventType":"Microsoft.SignalRService.ClientConnectionConnected",
      "EventTime":"2022-11-27T19:22:19.2349923Z",
      "Data": { 
           "timestamp":"2022-11-27T19:22:19.2349923Z",
           "hubName":"updates",
           "connectionId":"gmJM_GHVkXsQuS5C1LhdXXXXX",
           "userId":"your-user-sid-value"
      }
  }
  

• 扩展说明
  如果用户标识来自JWT令牌的声明，可调整UserId的绑定表达式，例如从令牌的特定声明字段获取，确保Azure SignalR服务能正确关联用户ID与连接。

内容的提问来源于stack exchange，提问作者Kzryzstof