AWS IoT Device Shadow

シャドウドキュメントの例

{
  "state": {
    "desired": {
      "temperature": 25,
      "mode": "auto",
      "fanSpeed": 2
    },
    "reported": {
      "temperature": 22,
      "mode": "auto",
      "fanSpeed": 1,
      "connectionStatus": "online"
    },
    "delta": {
      "temperature": 25,
      "fanSpeed": 2
    }
  },
  "metadata": {
    "desired": {
      "temperature": {
        "timestamp": 1627824000
      },
      "mode": {
        "timestamp": 1627824000
      },
      "fanSpeed": {
        "timestamp": 1627824000
      }
    },
    "reported": {
      "temperature": {
        "timestamp": 1627823900
      },
      "mode": {
        "timestamp": 1627823900
      },
      "fanSpeed": {
        "timestamp": 1627823900
      },
      "connectionStatus": {
        "timestamp": 1627823900
      }
    }
  },
  "version": 10,
  "timestamp": 1627824000
}

シャドウの操作フロー図

アプリケーション                AWS IoT                  デバイス
     |                           |                         |
     |--- shadow/update -------->|                         |
     |  (desired: {temp: 25})    |                         |
     |                           |--- shadow/update/delta ->|
     |                           |  (delta: {temp: 25})     |
     |                           |                         |
     |                           |                         |--- デバイスが温度を調整 ---
     |                           |                         |
     |                           |<-- shadow/update ------|
     |                           |  (reported: {temp: 25}) |
     |                           |                         |
     |<-- shadow/update/accepted-|                         |
     |  (state: {                |                         |
     |    desired: {temp: 25},   |                         |
     |    reported: {temp: 25},  |                         |
     |    delta: {}              |                         |
     |  })                       |                         |
        

シャドウの取得

aws iot-data get-thing-shadow \
    --thing-name MyThing \
    --output text > shadow.json

シャドウの更新

aws iot-data update-thing-shadow \
    --thing-name MyThing \
    --payload '{"state":{"desired":{"temperature":25,"mode":"auto"}}}' \
    --output text > response.json

名前付きシャドウの取得

aws iot-data get-thing-shadow \
    --thing-name MyThing \
    --shadow-name MyShadow \
    --output text > named-shadow.json

シャドウの更新（デバイスから）

// トピック: $aws/things/MyThing/shadow/update
// ペイロード:
{
  "state": {
    "reported": {
      "temperature": 22,
      "humidity": 45,
      "connectionStatus": "online"
    }
  }
}

シャドウの更新（アプリケーションから）

// トピック: $aws/things/MyThing/shadow/update
// ペイロード:
{
  "state": {
    "desired": {
      "temperature": 25,
      "mode": "auto"
    }
  }
}

シャドウの取得

// トピック: $aws/things/MyThing/shadow/get
// ペイロード: (空)

AWS IoT Device SDK for JavaScript v2を使用したシャドウの操作

const awsIot = require('aws-iot-device-sdk-v2');
const iotshadow = awsIot.iotshadow;

// シャドウクライアントの作成
const shadowClient = new iotshadow.IotShadowClient(connection);

// シャドウの更新
const updateShadow = async () => {
  const request = {
    thingName: 'MyThing',
    state: {
      reported: {
        temperature: 22,
        humidity: 45,
        connectionStatus: 'online'
      }
    }
  };
  
  try {
    await shadowClient.updateShadow(request);
    console.log('Successfully updated shadow');
  } catch (error) {
    console.log('Failed to update shadow', error);
  }
};

// シャドウの取得
const getShadow = async () => {
  const request = {
    thingName: 'MyThing'
  };
  
  try {
    const response = await shadowClient.getShadow(request);
    console.log('Shadow document:', response.state);
  } catch (error) {
    console.log('Failed to get shadow', error);
  }
};

// deltaの購読
const subscribeToDelta = () => {
  const request = {
    thingName: 'MyThing'
  };
  
  shadowClient.subscribeToShadowDeltaUpdatedEvents(
    request,
    mqtt.QoS.AtLeastOnce,
    (error, response) => {
      if (error) {
        console.log('Error subscribing to delta', error);
        return;
      }
      
      console.log('Received delta:', response.state);
      // デバイスの状態を更新する処理
    }
  );
};

シャドウの更新に基づいてSNS通知を送信するルール

// AWS IoT Ruleの定義
{
  "sql": "SELECT * FROM '$aws/things/+/shadow/update/accepted' WHERE state.reported.temperature > 30",
  "actions": [
    {
      "sns": {
        "targetArn": "arn:aws:sns:us-west-2:123456789012:high-temperature-alert",
        "roleArn": "arn:aws:iam::123456789012:role/aws-iot-rules-role",
        "messageFormat": "JSON"
      }
    }
  ]
}