本文对官方示例 temperature 进行实验。
功能说明
本示例主要是演示在云端获取边缘端的设备状态。
编译
本文对官方示例进行了修改。此处给出修改描述,详情参考修改后的源码。
1、参考 led 示例,新加 Makefile,修改 Dockerfile。
2、修改源码,去掉与硬件操作相关的函数,将采集的温度值 temperature 累加以观察其变化。
3、制作镜像,提交镜像。
3、修改 crds 和 deployment.yaml 文件,指定调度节点名称。
实验
部署:
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| kubectl apply -f crds/ kubectl apply -f deployment.yaml
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查看pod:
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| # kubectl get pod NAME READY STATUS RESTARTS AGE temperature-mapper-77fb74f5-vzztl 1/1 Running 0 5m10s `
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在边缘商查看日志:
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| # docker logs ecc3ba6a29dc 2020-03-22T09:11:51.777 [ main] INFO Sensor = DHT11: Temperature = 74*C, Humidity = 85% (retried 1 times) 2020-03-22T09:11:56.778 [ main] INFO Sensor = DHT11: Temperature = 75*C, Humidity = 85% (retried 1 times) 2020-03-22T09:12:01.778 [ main] INFO Sensor = DHT11: Temperature = 76*C, Humidity = 85% (retried 1 times)
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在云端观察:
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| kubectl get device temperature1 -oyaml -w
输出示例: apiVersion: devices.kubeedge.io/v1alpha1 kind: Device metadata: annotations: kubectl.kubernetes.io/last-applied-configuration: | {"apiVersion":"devices.kubeedge.io/v1alpha1","kind":"Device","metadata":{"annotations":{},"labels":{"description":"temperature","manufacturer":"test"},"name":"temperature1","namespace":"default"},"spec":{"deviceModelRef":{"name":"temperature-model"},"nodeSelector":{"nodeSelectorTerms":[{"matchExpressions":[{"key":"","operator":"In","values":["latelee1"]}]}]}},"status":{"twins":[{"desired":{"metadata":{"type":"string"},"value":""},"propertyName":"temperature-status"}]}} creationTimestamp: "2020-03-22T09:04:18Z" generation: 77 labels: description: temperature manufacturer: test name: temperature1 namespace: default resourceVersion: "29280" selfLink: /apis/devices.kubeedge.io/v1alpha1/namespaces/default/devices/temperature1 uid: e9869339-6d9b-4bf3-bf9f-c6191efeedc7 spec: deviceModelRef: name: temperature-model nodeSelector: nodeSelectorTerms: - matchExpressions: - key: "" operator: In values: - latelee1 status: twins: - desired: metadata: type: string value: "" propertyName: temperature-status reported: metadata: timestamp: "1584868316781" type: string value: 75C // !!!! 此值会变化
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源码研究
流程:
1、连接 mqtt:connectToMqtt,故需要边缘端开启 mqtt 服务,并监听 1883 端口。
2、采集温度:ReadDHTxxWithContextAndRetry,本例注释。
3、将温度值发布到mqtt:publishToMqtt。
4、之后进入 KubeEdge 系统,在云端可查看状态。
其它说明:
发布主题指定如下
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| deviceTwinUpdate := "$hw/events/device/" + "temperature" + "/twin/update"
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temperature 为设备名称。需要与 Device 中的 metadata.name 保持一致。此名称也是 kubectl get device
查看到的名称。可修改使其不一致,观察效果。
发布消息前先创建消息体:createActualUpdateMessage,结构体为 DeviceTwinUpdate,具体如下:
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| map[string]*MsgTwin{"temperature-status": {Actual: &TwinValue{Value: &actualValue}, Metadata: &TypeMetadata{Type: "Updated"}}}
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查看device.yaml:
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| status: twins: - propertyName: temperature-status desired: metadata: type: string value: ''
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目前看,部分对应起来,深层理论待研究。