30.设备间通信 - 33.OTA升级——设备端实现 - 《从0开始搭建IoT平台》

上报升级进度
响应OTA指令
代码联调

在这一节我们开始来实现 OTA 升级的设备端功能。

上报升级进度

首先我们使用一个类来封装上报升级进度的操作：

//IotHub_Device/sdk/ota_progress.js
const ObjectId = require('bson').ObjectID;
class OTAProgress {
    constructor({productName, deviceName, mqttClient, version, type}) {
        this.productName = productName
        this.deviceName = deviceName
        this.mqttClient = mqttClient
        this.version = version
        this.type = type
    }
    sendProgress(progress) {
        var meta = {
            version: this.version,
            type: this.type
        }
        var topic = `update_ota_status/${this.productName}/${this.deviceName}/${new ObjectId().toHexString()}`
        this.mqttClient.publish(topic, JSON.stringify({...meta, ...progress}), {qos: 1})
    }
    download(percent, desc = "download") {
        this.sendProgress({progress: percent, desc: desc})
    }
    downloadError(desc = "download error"){
        this.download(-1, desc)
    }
    checkMD5Error(desc = "check md5 error"){
        this.sendProgress({progress: -2, desc: desc})
    }
    installError(desc = "install error"){
        this.sendProgress({progress: -3, desc: desc})
    }
    error(desc = "error"){
        this.sendProgress({progress: -4, desc: desc})
    }
}

这个类封装了上报升级进度的各个节点的操作，设备应用代码只需要在相应的节点调用对应的方法就是了。比如下载升级包时调用 progress.download(17)，安装失败时调用 progress.installError()

响应OTA指令

在收到$ota_upgrade指令以后，DeviceSDK 代码需要把指令数据传递给设备应用代码：

//IotHub_Device/sdk/iot_device.js
handleCommand({commandName, requestID, encoding, payload, expiresAt, commandType = "cmd"}) {
             ...
            if (commandName.startsWith("$")) {
                payload = JSON.parse(data.toString())
                if (commandName == "$set_ntp") {
                    this.handleNTP(payload)
                } else if (commandName == "$set_tags") {
                    this.setTags(payload)
                }else if(commandName == "$ota_upgrade"){
                    var progress = new OTAProgress({
                        productName: this.productName,
                        deviceName: this.deviceName,
                        mqttClient: this.client,
                        version: payload.version,
                        type: payload.type
                    })
                    this.emit("ota_upgrade", payload, progress)
                }
            }
            ...
        }
    }

DeviceSDK 除了把 OTA 升级相关的数据通过”ota_upgrade”事件传递给设备应用代码，还传递了一个 OTAProgress 对象，设备应用代码可以调用这个对象方法正确上报升级进度。

代码联调

设备端的功能就全部实现了，接下来我们写一端代码来测试 OTA 升级功能。
首先实现一个设备端来模拟 OTA 升级，它收到 OTA 升级指令以后，会每隔 2 秒更新一次下载进度，当下载进度达到 100% 时，会再等待 3 秒之后上报更新后的软件版本，我们用这样的方式来模拟一次成功的 OTA 升级流程：

//IotHub_Device/samples/ota_upgrade.js
...
const currentVersion = "1.0"
device.on("online", function () {
    console.log("device is online")
})
device.on("ota_upgrade", function (ota, progress) {
    console.log(going to upgrade ${ota.type}: ${ota.url}, version=${ota.version})
    var percent = 0
    var performUpgrade = function () {
        console.log(`download:${percent}`)
        progress.download(percent)
        if(percent < 100){
            percent += 20
            setTimeout(performUpgrade, 2000)
        }else{
            setTimeout(function () {
                device.updateStatus({firmware_ver: ota.version})
            }, 3000)
        }
    }
    performUpgrade()
})
device.connect()
device.updateStatus({firmware_ver: currentVersion})

然后模拟业务系统，向设备发送 OTA 指令以后，每隔 1 秒钟查询一次设备的升级进度，进度达到 100 以后就检查设备的软件版本，如果设备的软件版本和预期一致，就说明设备已经升级成功了：

//IotHub_Server/samples/perform_ota.js
...
var otaData = {
    type: "firmware",
    url: "http://test.com/firmware/1.1.pkg",
    version: "1.1",
    size: 1000,
    md5: "abcd"
}
var progress = 0
var checkUpgradeProgress = function () {
    if (progress < 100) {
        request.get(`http://127.0.0.1:3000/ota/${process.env.TARGET_PRODUCT_NAME}/${process.env.TARGET_DEVICE_NAME}`, function (err, res, body) {
            if (!err && res.statusCode == 200) {
                var info = JSON.parse(body);
                if(info.version == otaData.version) {
                    progress = info.progress
                    console.log(`current progress:${progress}%`);
                }
                setTimeout(checkUpgradeProgress, 1000)
            }
        })
    } else {
        request.get(`http://127.0.0.1:3000/devices/${process.env.TARGET_PRODUCT_NAME}/${process.env.TARGET_DEVICE_NAME}`, function (err, res, body) {
            if (!err && res.statusCode == 200) {
                var info = JSON.parse(body);
                console.log(`current version:${info.device_status.firmware_ver}`);
                if (info.device_status.firmware_ver == otaData.version) {
                    console.log(`upgrade completed`);
                } else {
                    setTimeout(checkUpgradeProgress, 1000)
                }
            }
        })
    }
}
console.log("perform upgrade")
request.post(`http://127.0.0.1:3000/ota/${process.env.TARGET_PRODUCT_NAME}/${process.env.TARGET_DEVICE_NAME}`, {
    form: otaData
}, function (error, response) {
    if (error) {
        console.log(error)
    } else {
        console.log('statusCode:', response && response.statusCode);
        checkUpgradeProgress()
    }
})

先运行 IotHub\_Device/samples/ota\_upgrade.js，然后运行 IotHub\_Server/samples/perform_ota.js，观察下输出：

## IotHub_Device/samples/ota_upgrade.js
device is online
going to upgrade firmware: http://test.com/firmware/1.1.pkg, version=1.1
download:0
download:20
download:40
download:60
download:80
download:100
upgrade completed

## IotHub_Server/samples/perform_ota.js
perform upgrade
statusCode: 200
current progress:0%
current progress:0%
current progress:20%
current progress:20%
current progress:40%
current progress:60%
current progress:60%
current progress:80%
current progress:80%
current progress:100%
current version:1.0
current version:1.0
current version:1.1
upgrade completed

这说明 OTA 升级功能在正确工作了。

这一节，我们完成了 IotHub 设备的 OTA 升级功能，在接下来的几节课中，我们会讨论如何设计和实现一个新的功能：设备影子。