azure - 订阅 Azure IoT 中心设备事件

Question

我想从 Azure IoT 中心阅读“Microsoft.Devices.DeviceConnected”事件（ https://docs.microsoft.com/en-us/azure/iot-hub/iot-hub-event-grid#event-types ） . 我发现的唯一示例涉及 Azure 事件网格，但我更愿意使用 IoT 中心的内部端点（事件中心）。这甚至可能吗？当我使用EventProcessorHost接口订阅内部事件中心时，我得到的只是 D2C 用户遥测消息。

标签： azureazure-iot-hubazure-eventhub

Answer 1

就像@PeterBons 所说，Azure IoT Hub 不支持此功能，但是可以使用 Azure Function 在 Azure IoT Hub 之外完成。以下屏幕片段显示了此集成，其中 EventGrid 事件被推送到 IoT 中心流：

如您所见，上面的EventGridTrigger函数是Azure Event Grid 和 Azure IoT Hub 之间的集成器。此集成器负责使用事件网格事件，映射到 D2C 消息并将其作为具有 Https 协议的虚拟 IoT 设备（后端设备）发送到 Azure IoT 中心。

更新：

以下代码片段是 Azure 函数 - 集成到 Azure IoT 中心的示例：

#r "Microsoft.Azure.EventGrid"
#r "Newtonsoft.Json"

using System.Configuration;
using System.Threading.Tasks;
using System.Security.Cryptography;
using System.Web;
using System.Net.Http;
using System.Text;
using System.Globalization;
using Newtonsoft.Json;
using Microsoft.Azure.EventGrid.Models;


// reusable client proxy
static HttpClientHelper iothub = new HttpClientHelper(Environment.GetEnvironmentVariable("AzureIoTHubShariedAccessPolicy"));

public static async Task Run(EventGridEvent eventGridEvent, ILogger log)
{
    log.LogInformation(eventGridEvent.Data.ToString());

    // my virtual backend iot device
    string deviceId = "Device13";
    var content = new StringContent(JsonConvert.SerializeObject(eventGridEvent), Encoding.UTF8, "application/json");

    await iothub.Client.PostAsync($"/devices/{deviceId}/messages/events?api-version=2018-06-30", content);
}




// helpers
class HttpClientHelper
{
    HttpClient client;
    DateTime expiringSaS;
    (string hostname, string keyname, string key) config;

    public HttpClientHelper(string connectionString)
    {
        config = GetPartsFromConnectionString(connectionString);
        client = new HttpClient() { BaseAddress = new Uri($"https://{config.hostname}")};
        SetAuthorizationHeader();         
    }

    public HttpClient Client
    {
        get
        {          
            if (expiringSaS < DateTime.UtcNow.AddMinutes(-1))
            {
               SetAuthorizationHeader();  
            }         
            return client;
        }
    }

    internal void SetAuthorizationHeader()
    {
        lock (client)
        {
            if (expiringSaS < DateTime.UtcNow.AddMinutes(-1)) 
            {
                string sasToken = GetSASToken(config.hostname, config.key, config.keyname, 1);
                if (client.DefaultRequestHeaders.Contains("Authorization"))
                    client.DefaultRequestHeaders.Remove("Authorization");
                client.DefaultRequestHeaders.Add("Authorization", sasToken);
                expiringSaS = DateTime.UtcNow.AddHours(1);
            }
        }
    }

    internal (string hostname, string keyname, string key) GetPartsFromConnectionString(string connectionString)
    {
        var parts = connectionString.Split(new[] { ';' }, StringSplitOptions.RemoveEmptyEntries).Select(s => s.Split(new[] { '=' }, 2)).ToDictionary(x => x[0].Trim(), x => x[1].Trim());
        return (parts["HostName"] ?? "", parts["SharedAccessKeyName"] ?? "", parts["SharedAccessKey"] ?? "");
    }

    internal string GetSASToken(string resourceUri, string key, string keyName = null, uint hours = 24)
    {
        var expiry = GetExpiry(hours);
        string stringToSign = HttpUtility.UrlEncode(resourceUri) + "\n" + expiry;
        HMACSHA256 hmac = new HMACSHA256(Convert.FromBase64String(key));

        var signature = Convert.ToBase64String(hmac.ComputeHash(Encoding.UTF8.GetBytes(stringToSign)));
        var sasToken = String.Format(CultureInfo.InvariantCulture, $"SharedAccessSignature sr={HttpUtility.UrlEncode(resourceUri)}&sig={HttpUtility.UrlEncode(signature)}&se={expiry}");
        if (!string.IsNullOrEmpty(keyName))
            sasToken += $"&skn={keyName}";
        return sasToken;
    }

    internal string GetExpiry(uint hours = 24)
    {
        TimeSpan sinceEpoch = DateTime.UtcNow - new DateTime(1970, 1, 1);
        return Convert.ToString((int)sinceEpoch.TotalSeconds + 3600 * hours);
    }
}

和function.json：

{
  "bindings": [
    {
      "type": "eventGridTrigger",
      "name": "eventGridEvent",
      "direction": "in"
    }
  ],
  "disabled": false
}