设备孪生入门 (Python)Get started with device twins (Python)

设备孪生是存储设备状态信息(包括元数据、配置和条件)的 JSON 文档。Device twins are JSON documents that store device state information, including metadata, configurations, and conditions. IoT 中心为连接到它的每台设备保留一个设备孪生。IoT Hub persists a device twin for each device that connects to it.

Note

本文中所述的功能仅可在 IoT 中心的标准层中使用。The features described in this article are only available in the standard tier of IoT hub. 有关基本和标准 IoT 中心层的详细信息,请参阅如何选择合适的 IoT 中心层For more information about the basic and standard IoT Hub tiers, see How to choose the right IoT Hub tier.

使用设备孪生可以:Use device twins to:

  • 存储来自解决方案后端的设备元数据。Store device metadata from your solution back end.

  • 通过设备应用报告当前状态信息,例如可用功能和条件(例如,使用的连接方法)。Report current state information such as available capabilities and conditions, for example, the connectivity method used, from your device app.

  • 同步设备应用和后端应用之间长时间运行的工作流的状态(例如固件和配置更新)。Synchronize the state of long-running workflows, such as firmware and configuration updates, between a device app and a back-end app.

  • 查询设备的元数据、配置或状态。Query your device metadata, configuration, or state.

设备孪生旨在执行同步以及查询设备的配置和条件。Device twins are designed for synchronization and for querying device configurations and conditions. 了解设备孪生中提供了有关何时使用设备孪生的详细信息。More information on when to use device twins can be found in Understand device twins.

设备孪生存储在 IoT 中心内,并且包含以下元素:Device twins are stored in an IoT hub and contain the following elements:

  • 标记Tags. 仅可由解决方案后端访问的设备元数据。Device metadata accessible only by the solution back end.

  • 所需的属性Desired properties. 可以由解决方案后端修改并可由设备应用观察的 JSON 对象。JSON objects modifiable by the solution back end and observable by the device app.

  • 报告的属性Reported properties. 可由设备应用修改并可由解决方案后端读取的 JSON 对象。JSON objects modifiable by the device app and readable by the solution back end.

标记和属性不能包含数组,但可以嵌套对象。Tags and properties cannot contain arrays, but objects can be nested.

下图显示了设备孪生组织:The following illustration shows device twin organization:

显示功能的设备孪生图像

此外,解决方案后端可以根据上述所有数据查询设备孪生。Additionally, the solution back end can query device twins based on all the above data. 有关设备孪生的详细信息,请参阅了解设备孪生For more information about device twins, see Understand device twins. 有关查询的详细信息,请参阅 IoT 中心查询语言For more information about querying, see IoT Hub query language.

本教程演示如何:This tutorial shows you how to:

  • 创建将标记添加到设备孪生的后端应用,以及将其连接通道作为设备孪生上的报告属性进行报告的模拟设备应用。Create a back-end app that adds tags to a device twin, and a simulated device app that reports its connectivity channel as a reported property on the device twin.

  • 使用标记上的筛选器和之前创建的属性通过后端应用查询设备。Query devices from your back-end app using filters on the tags and properties previously created.

在本教程结束时,会获得两个 Python 控制台应用:At the end of this tutorial, you will have two Python console apps:

  • AddTagsAndQuery.py,这是一个 Python 后端应用,用于添加标记并查询设备孪生。AddTagsAndQuery.py, a Python back-end app, which adds tags and queries device twins.
  • ReportConnectivity.py,这是一个 .Python 应用,用于模拟使用早先创建的设备标识连接到 IoT 中心的设备,并报告其连接状况。ReportConnectivity.py, a Python app, which simulates a device that connects to your IoT hub with the device identity created earlier, and reports its connectivity condition.

Note

IoT 中心通过 Azure IoT 设备 SDK 为许多设备平台和语言(包括 C、Java、Javascript 和 Python)提供 SDK 支持。IoT Hub has SDK support for many device platforms and languages (including C, Java, Javascript, and Python) through Azure IoT device SDKs. 有关如何使用 Python 将设备连接到本教程的代码,以及通常如何连接到 Azure IoT 中心的说明,请参阅 Azure IoT Python SDKFor instructions on how to use Python to connect your device to this tutorial's code, and generally to Azure IoT Hub, see the Azure IoT Python SDK.

先决条件Prerequisites

创建 IoT 中心Create an IoT hub

此部分介绍如何使用 Azure 门户创建 IoT 中心。This section describes how to create an IoT hub using the Azure portal.

  1. 登录到 Azure 门户Sign in to the Azure portal.

  2. 选择“创建资源”,然后在“搜索市场”字段中输入“IoT 中心”。 Choose Create a resource, and then enter IoT Hub in the Search the Marketplace field.

  3. 在搜索结果中选择“IoT 中心”,然后选择“创建” 。Select IoT Hub from the search results, and then select Create.

  4. 在“基本信息”选项卡上,按如下所示填写字段: On the Basics tab, complete the fields as follows:

    • 订阅:选择要用于中心的订阅。Subscription: Select the subscription to use for your hub.

    • 资源组:选择一个资源组或新建一个资源组。Resource Group: Select a resource group or create a new one. 若要新建资源组,请选择“新建”并填写要使用的名称。 To create a new one, select Create new and fill in the name you want to use. 若要使用现有的资源组,请选择它。To use an existing resource group, select that resource group. 有关详细信息,请参阅管理 Azure 资源管理器资源组For more information, see Manage Azure Resource Manager resource groups.

    • 区域:选择中心所在的区域。Region: Select the region in which you want your hub to be located. 选择最靠近你的位置。Select the location closest to you.

    • IoT 中心名称:输入中心的名称。IoT Hub Name: Enter a name for your hub. 此名称必须全局唯一。This name must be globally unique. 如果输入的名称可用,会显示一个绿色复选标记。If the name you enter is available, a green check mark appears.

    Important

    IoT 中心将公开为 DNS 终结点,因此,命名时请务必避免包含任何敏感信息。The IoT hub will be publicly discoverable as a DNS endpoint, so make sure to avoid any sensitive information while naming it.

    在 Azure 门户中创建中心

  5. 在完成时选择“下一步: 大小和规模”,以继续创建中心。Select Next: Size and scale to continue creating your hub.

    使用 Azure 门户为新的中心设置大小和规模

    在此屏幕中可以设置以下值:This screen allows you to set the following values:

    • 定价和缩放层:选择的层。Pricing and scale tier: Your selected tier. 可以根据你需要的功能数以及每天通过解决方案发送的消息数从多个层级中进行选择。You can choose from several tiers, depending on how many features you want and how many messages you send through your solution per day. 免费层适用于测试和评估。The free tier is intended for testing and evaluation. 允许 500 台设备连接到中心,每天最多可传输 8,000 条消息。It allows 500 devices to be connected to the hub and up to 8,000 messages per day. 每个 Azure 订阅可以在免费层中创建一个 IoT 中心。Each Azure subscription can create one IoT Hub in the free tier.

    • IoT 中心单元:每个单位每日允许的消息数取决于中心的定价层。IoT Hub units: The number of messages allowed per unit per day depends on your hub's pricing tier. 例如,如果希望中心支持 700,000 条消息引入,请选择两个 S1 层单位。For example, if you want the hub to support ingress of 700,000 messages, you choose two S1 tier units. 有关其他层选项的详细信息,请参阅选择合适的 IoT 中心层For details about the other tier options, see Choosing the right IoT Hub tier.

    • 高级设置 > 设备到云的分区:此属性将设备到云消息与这些消息的同步读取器数目相关联。Advanced Settings > Device-to-cloud partitions: This property relates the device-to-cloud messages to the number of simultaneous readers of the messages. 大多数中心只需要 4 个分区。Most hubs need only four partitions.

  6. 对于本文,请接受默认选项,然后选择“查看 + 创建”以查看所做的选择。 For this article, accept the default choices, and then select Review + create to review your choices. 会显示类似于以下的屏幕。You see something similar to this screen.

    查看用于创建新中心的信息

  7. 选择“创建”以创建新的中心 。Select Create to create your new hub. 创建中心需要几分钟时间。Creating the hub takes a few minutes.

在 IoT 中心内注册新设备Register a new device in the IoT hub

本部分在 IoT 中心的标识注册表中创建设备标识。In this section, you create a device identity in the identity registry in your IoT hub. 除非设备在标识注册表中具有条目,否则设备无法连接到中心。A device cannot connect to a hub unless it has an entry in the identity registry. 有关详细信息,请参阅 IoT 中心开发人员指南For more information, see the IoT Hub developer guide.

  1. 在 IoT 中心导航菜单中,打开“IoT 设备” ,然后选择“新建” 以在 IoT 中心中添加设备。In your IoT hub navigation menu, open IoT Devices, then select New to add a device in your IoT hub.

    在门户中创建设备标识

  2. 在“创建设备” 中,为新设备提供名称(例如 myDeviceId),然后选择“保存” 。In Create a device, provide a name for your new device, such as myDeviceId, and select Save. 此操作会为 IoT 中心创建设备标识。This action creates a device identity for your IoT hub.

    添加新设备

    Important

    收集的日志中可能会显示设备 ID 用于客户支持和故障排除,因此,在为日志命名时,请务必避免包含任何敏感信息。The device ID may be visible in the logs collected for customer support and troubleshooting, so make sure to avoid any sensitive information while naming it.

  3. 创建设备后,在“IoT 设备”窗格的列表中打开该设备 。After the device is created, open the device from the list in the IoT devices pane. 复制主连接字符串以便稍后使用。Copy the Primary Connection String to use later.

    设备连接字符串

Note

IoT 中心标识注册表仅存储用于实现 IoT 中心安全访问的设备标识。The IoT Hub identity registry only stores device identities to enable secure access to the IoT hub. 它存储设备 ID 和密钥作为安全凭据,以及启用/禁用标志让你禁用对单个设备的访问。It stores device IDs and keys to use as security credentials, and an enabled/disabled flag that you can use to disable access for an individual device. 如果应用程序需要存储其他特定于设备的元数据,则应使用特定于应用程序的存储。If your application needs to store other device-specific metadata, it should use an application-specific store. 有关详细信息,请参阅 IoT 中心开发人员指南For more information, see IoT Hub developer guide.

获取 IoT 中心连接字符串Get the IoT hub connection string

在本文中,将创建一个后端服务,该服务将所需的属性添加到设备孪生,然后查询标识注册表以查找具有已相应更新的报告属性的所有设备。In this article, you create a backend service that adds desired properties to a device twin and then queries the identity registry to find all devices with reported properties that have been updated accordingly. 你的服务需要“服务连接” 权限才能修改设备孪生的所需属性,并且需要“注册表读取” 权限才能查询标识注册表。Your service needs the service connect permission to modify desired properties of a device twin, and it needs the registry read permission to query the identity registry. 没有仅包含这两个权限的默认共享访问策略,因此需要创建一个。There is no default shared access policy that contains only these two permissions, so you need to create one.

若要创建一个共享访问策略以授予“服务连接”和“注册表读取”权限,同时获取该策略的连接字符串,请执行以下步骤: To create a shared access policy that grants service connect and registry read permissions and get a connection string for this policy, follow these steps:

  1. Azure 门户中,选择“资源组” 。In the Azure portal, select Resource groups. 选择中心所在的资源组,然后从资源列表中选择中心。Select the resource group where your hub is located, and then select your hub from the list of resources.

  2. 在中心的左侧窗格中,选择“共享访问策略” 。On the left-side pane of your hub, select Shared access policies.

  3. 从策略列表上方的顶部菜单中选择“添加” 。From the top menu above the list of policies, select Add.

  4. 在“添加共享访问策略”下,为策略输入一个说明性名称,例如 serviceAndRegistryRead 。 Under Add a shared access policy, enter a descriptive name for your policy, such as serviceAndRegistryRead. 在“权限”下选择“注册表读取”和“服务连接”,然后选择“创建” 。 Under Permissions, select Registry read and Service connect, and then select Create.

    显示如何添加新的共享访问策略

  5. 从策略列表中选择新策略。Select your new policy from the list of policies.

  6. 在“共享访问密钥” 下,选择“连接字符串 - 主密钥” 所对应的“复制”图标并保存该值。Under Shared access keys, select the copy icon for the Connection string -- primary key and save the value.

    显示如何检索连接字符串

有关 IoT 中心共享访问策略和权限的详细信息,请参阅访问控制和权限For more information about IoT Hub shared access policies and permissions, see Access control and permissions.

创建服务应用Create the service app

在本部分中,将创建一个 Python 控制台应用,该应用将位置元数据添加到与 {Device ID} 关联的设备孪生。In this section, you create a Python console app that adds location metadata to the device twin associated with your {Device ID}. 然后,该应用将选择位于 Redmond 的设备来查询存储在 IoT 中心的设备孪生,然后查询报告移动电话网络连接的设备孪生。It then queries the device twins stored in the IoT hub selecting the devices located in Redmond, and then the ones that are reporting a cellular connection.

  1. 在工作目录中,打开命令提示符并安装安装适用于 Python 的 Azure IoT 中心服务 SDK 。In your working directory, open a command prompt and install the Azure IoT Hub Service SDK for Python.

    pip install azure-iothub-service-client
    

    Note

    azure-iothub-service-client 的 pip 包目前仅适用于 Windows 操作系统。The pip package for azure-iothub-service-client is currently available only for Windows OS. 对于 Linux/Mac 操作系统,请参阅准备适用于 Python 的开发环境一文中特定于 Linux 和 Mac 操作系统的部分。For Linux/Mac OS, please refer to the Linux and Mac OS-specific sections on the Prepare your development environment for Python post.

  2. 使用文本编辑器,新建一个 AddTagsAndQuery.py 文件。Using a text editor, create a new AddTagsAndQuery.py file.

  3. 添加以下代码,从服务 SDK 导入所需模块:Add the following code to import the required modules from the service SDK:

    import sys
    import iothub_service_client
    from iothub_service_client import IoTHubRegistryManager, IoTHubRegistryManagerAuthMethod
    from iothub_service_client import IoTHubDeviceTwin, IoTHubError
    
  4. 添加以下代码。Add the following code. [IoTHub Connection String] 替换为在获取 IoT 中心连接字符串中复制的 IoT 中心连接字符串。Replace [IoTHub Connection String] with the IoT hub connection string you copied in Get the IoT hub connection string. [Device Id] 替换为在在 IoT 中心注册新设备中注册的设备 ID。Replace [Device Id] with the device ID you registered in Register a new device in the IoT hub.

    CONNECTION_STRING = "[IoTHub Connection String]"
    DEVICE_ID = "[Device Id]"
    
    UPDATE_JSON = "{\"properties\":{\"desired\":{\"location\":\"Redmond\"}}}"
    
    UPDATE_JSON_SEARCH = "\"location\":\"Redmond\""
    UPDATE_JSON_CLIENT_SEARCH = "\"connectivity\":\"cellular\""
    
  5. 将以下代码添加到 AddTagsAndQuery.py 文件:Add the following code to the AddTagsAndQuery.py file:

    def iothub_service_sample_run():
        try:
            iothub_registry_manager = IoTHubRegistryManager(CONNECTION_STRING)
    
            iothub_registry_statistics = iothub_registry_manager.get_statistics()
            print ( "Total device count                       : {0}".format(iothub_registry_statistics.totalDeviceCount) )
            print ( "Enabled device count                     : {0}".format(iothub_registry_statistics.enabledDeviceCount) )
            print ( "Disabled device count                    : {0}".format(iothub_registry_statistics.disabledDeviceCount) )
            print ( "" )
    
            number_of_devices = iothub_registry_statistics.totalDeviceCount
            dev_list = iothub_registry_manager.get_device_list(number_of_devices)
    
            iothub_twin_method = IoTHubDeviceTwin(CONNECTION_STRING)
    
            for device in range(0, number_of_devices):
                if dev_list[device].deviceId == DEVICE_ID:
                    twin_info = iothub_twin_method.update_twin(dev_list[device].deviceId, UPDATE_JSON)
    
            print ( "Devices in Redmond: " )        
            for device in range(0, number_of_devices):
                twin_info = iothub_twin_method.get_twin(dev_list[device].deviceId)
    
                if twin_info.find(UPDATE_JSON_SEARCH) > -1:
                    print ( dev_list[device].deviceId )
    
            print ( "" )
    
            print ( "Devices in Redmond using cellular network: " )
            for device in range(0, number_of_devices):
                twin_info = iothub_twin_method.get_twin(dev_list[device].deviceId)
    
                if twin_info.find(UPDATE_JSON_SEARCH) > -1:
                    if twin_info.find(UPDATE_JSON_CLIENT_SEARCH) > -1:
                        print ( dev_list[device].deviceId )
    
        except IoTHubError as iothub_error:
            print ( "Unexpected error {0}".format(iothub_error) )
            return
        except KeyboardInterrupt:
            print ( "IoTHub sample stopped" )
    

    Registry 对象公开从服务与设备孪生进行交互所需的所有方法。The Registry object exposes all the methods required to interact with device twins from the service. 此代码将首先初始化 Registry 对象,然后更新 deviceId 的设备孪生,最后运行两个查询。The code first initializes the Registry object, then updates the device twin for deviceId, and finally runs two queries. 第一个查询仅选择位于 Redmond43 工厂的设备的设备孪生,第二个查询将查询细化为仅选择还要通过移动电话网络连接的设备。The first selects only the device twins of devices located in the Redmond43 plant, and the second refines the query to select only the devices that are also connected through cellular network.

  6. AddTagsAndQuery.py 的末尾添加以下代码来实现 iothub_service_sample_run 函数:Add the following code at the end of AddTagsAndQuery.py to implement the iothub_service_sample_run function:

    if __name__ == '__main__':
        print ( "Starting the IoT Hub Device Twins Python service sample..." )
    
        iothub_service_sample_run()
    
  7. 使用以下内容运行应用程序:Run the application with:

    python AddTagsAndQuery.py
    

    在查询位于 Redmond43 的所有设备的查询结果中,应该会看到一个设备,而在将结果限制为使用蜂窝网络的设备的查询结果中没有任何设备。You should see one device in the results for the query asking for all devices located in Redmond43 and none for the query that restricts the results to devices that use a cellular network.

    第一个显示 Redmond 中所有设备的查询

在下一部分中,创建的设备应用会报告连接信息,并更改上一部分中查询的结果。In the next section, you create a device app that reports the connectivity information and changes the result of the query in the previous section.

创建设备应用Create the device app

在本部分中,将创建一个 Python 控制台应用,该应用以你的 {Device Id} 身份连接到中心,然后更新其设备孪生的报告属性,来说明它是使用手机网络进行连接的。In this section, you create a Python console app that connects to your hub as your {Device Id}, and then updates its device twin's reported properties to contain the information that it is connected using a cellular network.

  1. 在工作目录中的命令提示符下,安装适用于 Python 的 Azure IoT 中心设备 SDKFrom a command prompt in your working directory, install the Azure IoT Hub Device SDK for Python:

    pip install azure-iot-device
    
  2. 使用文本编辑器,新建一个 ReportConnectivity.py 文件。Using a text editor, create a new ReportConnectivity.py file.

  3. 添加以下代码,从设备 SDK 导入所需模块:Add the following code to import the required modules from the device SDK:

    import time
    import threading
    from azure.iot.device import IoTHubModuleClient
    
  4. 添加以下代码。Add the following code. [IoTHub Device Connection String] 占位符值替换为在在 IoT 中心注册新设备中复制的设备连接字符串。Replace the [IoTHub Device Connection String] placeholder value with the device connection string you copied in Register a new device in the IoT hub.

    CONNECTION_STRING = "[IoTHub Device Connection String]"
    
  5. 将以下代码添加到 ReportConnectivity.py 文件以实现设备孪生功能:Add the following code to the ReportConnectivity.py file to implement the device twins functionality:

    def twin_update_listener(client):
        while True:
            patch = client.receive_twin_desired_properties_patch()  # blocking call
            print("Twin patch received:")
            print(patch)
    
    def iothub_client_init():
        client = IoTHubModuleClient.create_from_connection_string(CONNECTION_STRING)
        return client
    
    def iothub_client_sample_run():
        try:
            client = iothub_client_init()
    
            twin_update_listener_thread = threading.Thread(target=twin_update_listener, args=(client,))
            twin_update_listener_thread.daemon = True
            twin_update_listener_thread.start()
    
            # Send reported 
            print ( "Sending data as reported property..." )
            reported_patch = {"connectivity": "cellular"}
            client.patch_twin_reported_properties(reported_patch)
            print ( "Reported properties updated" )
    
            while True:
                time.sleep(1000000)
        except KeyboardInterrupt:
            print ( "IoTHubClient sample stopped" )
    

    Client 对象公开从该设备与设备孪生交互所需的所有方法。The Client object exposes all the methods you require to interact with device twins from the device. 上面的代码首先初始化 Client 对象,然后检索你的设备的设备孪生,并使用连接信息更新其报告属性。The previous code, after it initializes the Client object, retrieves the device twin for your device and updates its reported property with the connectivity information.

  6. ReportConnectivity.py 的末尾添加以下代码来实现 iothub_client_sample_run 函数:Add the following code at the end of ReportConnectivity.py to implement the iothub_client_sample_run function:

    if __name__ == '__main__':
        print ( "Starting the IoT Hub Device Twins Python client sample..." )
        print ( "IoTHubModuleClient waiting for commands, press Ctrl-C to exit" )
    
        iothub_client_sample_run()
    
  7. 运行设备应用:Run the device app:

    python ReportConnectivity.py
    

    应当会看到关于设备孪生已更新的确认。You should see confirmation the device twins were updated.

    更新孪生

  8. 现在设备报告了其连接信息,应出现在两个查询中。Now that the device reported its connectivity information, it should appear in both queries. 回过头来再次运行查询:Go back and run the queries again:

    python AddTagsAndQuery.py
    

    这一次,两个查询结果中应当都会显示你的 {Device ID}This time your {Device ID} should appear in both query results.

    第二个查询

后续步骤Next steps

本教程中,在 Azure 门户中配置了新的 IoT 中心,并在 IoT 中心的标识注册表中创建了设备标识。In this tutorial, you configured a new IoT hub in the Azure portal, and then created a device identity in the IoT hub's identity registry. 已从后端应用以标记形式添加了设备元数据,并编写了模拟的设备应用,用于报告设备孪生中的设备连接信息。You added device metadata as tags from a back-end app, and wrote a simulated device app to report device connectivity information in the device twin. 你还学习了如何使用注册表查询此信息。You also learned how to query this information using the registry.

充分利用以下资源:Use the following resources to learn how to: