限速設計及實現(xiàn)(微服務架構(gòu))

[圖片上傳失敗...(image-c9b470-1662870789547)]

開過車或者坐過車的都對限速是深惡痛絕吧，不過為了大家安全，忍一忍吧。系統(tǒng)究竟是如何判斷車主是否超速那，本文主要介紹這個系統(tǒng)到底是如何設計的。本文基于微服務進行設計。

關(guān)于微服務，在微服務初探（0）和微服務-node.js中對微服務有簡單的介紹。通過這篇文章，可以進一步了解微服務。

注：本文內(nèi)容參考《Dapr For .NET developer》，專有名詞保留英文原文，不做翻譯。

Dapr

The Distributed Application Runtime (Dapr) provides APIs that simplify microservice connectivity. Whether your communication pattern is service to service invocation or pub/sub messaging, Dapr helps you write resilient and secured microservices.

Building blocks抽象了分布式應用能力的實現(xiàn)，service只需要和Building blocks進行交互即可。
[圖片上傳失敗...(image-5830d9-1662870789547)]

Dapr的現(xiàn)在和安裝可參考Install the Dapr CLI。

限速設計

[圖片上傳失敗...(image-149a63-1662870789547)]
這里面fine是罰單，罰款的意思。

VehicleState包括了車牌號，進入限速區(qū)域(Cameral)時間，退出限速區(qū)域(Cameral)時間。

public record struct VehicleState
{
    public string LicenseNumber { get; init; }
    public DateTime EntryTimestamp { get; init; }
    public DateTime? ExitTimestamp { get; init; }

    public VehicleState(string licenseNumber, DateTime entryTimestamp, DateTime? exitTimestamp = null)
    {
        this.LicenseNumber = licenseNumber;
        this.EntryTimestamp = entryTimestamp;
        this.ExitTimestamp = exitTimestamp;
    }
}

據(jù)此就可以計算出平均時速，然后再與規(guī)定的時速進行比較，如果超過了，不好意思，您將收到一封郵件，也可以用短信等方式發(fā)送給車主。而車主的郵件信息通過VehicleRegistrationService來獲取。

車輛信息的結(jié)構(gòu)體定義如下：

public record struct VehicleInfo(string VehicleId, string Brand, string Model, string OwnerName, string OwnerEmail);

代碼實現(xiàn)

windows平臺下需要將start-maildev.ps1修改為，修改參考maildev/maildev。

docker run -d -p 4000:1080 -p 4025:1025 --name dtc-maildev maildev/maildev

-d: 后臺運行容器，并返回容器ID；

(1) CameralSimulation.cs

模擬進入和退出代碼：

// simulate entry
DateTime entryTimestamp = DateTime.Now;
var vehicleRegistered = new VehicleRegistered
{
    Lane = _camNumber,
    LicenseNumber = GenerateRandomLicenseNumber(),
    Timestamp = entryTimestamp
};
await _trafficControlService.SendVehicleEntryAsync(vehicleRegistered);
Console.WriteLine($"Simulated ENTRY of vehicle with license-number {vehicleRegistered.LicenseNumber} in lane {vehicleRegistered.Lane}");

// simulate exit
TimeSpan exitDelay = TimeSpan.FromSeconds(_rnd.Next(_minExitDelayInS, _maxExitDelayInS) + _rnd.NextDouble());
Task.Delay(exitDelay).Wait();
vehicleRegistered.Timestamp = DateTime.Now;
vehicleRegistered.Lane = _rnd.Next(1, 4);
await _trafficControlService.SendVehicleExitAsync(vehicleRegistered);
Console.WriteLine($"Simulated EXIT of vehicle with license-number {vehicleRegistered.LicenseNumber} in lane {vehicleRegistered.Lane}");

跟蹤 _trafficControlService.SendVehicleEntryAsync

 public async Task SendVehicleEntryAsync(VehicleRegistered vehicleRegistered)
 {
     var eventJson = JsonSerializer.Serialize(vehicleRegistered);
     var message = new MqttApplicationMessageBuilder()
         .WithTopic("trafficcontrol/entrycam")
         .WithPayload(Encoding.UTF8.GetBytes(eventJson))
         .WithAtMostOnceQoS()
         .Build();
     await _client.PublishAsync(message, CancellationToken.None);
 }

使用Input Binding來發(fā)布消息?？勺粉櫟较⒌挠嗛喺呤莟rafficcontrolservice。
（2）TrafficController.cs

[HttpPost("entrycam")]
 public async Task<ActionResult> VehicleEntryAsync(VehicleRegistered msg)
 {
     try
     {
         // log entry
         _logger.LogInformation($"ENTRY detected in lane {msg.Lane} at {msg.Timestamp.ToString("hh:mm:ss")} " +
             $"of vehicle with license-number {msg.LicenseNumber}.");

         // store vehicle state
         var vehicleState = new VehicleState(msg.LicenseNumber, msg.Timestamp, null);
         await _vehicleStateRepository.SaveVehicleStateAsync(vehicleState);

         return Ok();
     }
     catch (Exception ex)
     {
         _logger.LogError(ex, "Error occurred while processing ENTRY");
         return StatusCode(500);
     }
 }

跟蹤_vehicleStateRepository.SaveVehicleStateAsync(vehicleState)

public async Task SaveVehicleStateAsync(VehicleState vehicleState)
{
    await _daprClient.SaveStateAsync<VehicleState>(
        DAPR_STORE_NAME, vehicleState.LicenseNumber, vehicleState);
}

使用state management building block來保存VehicleState。

同理可知退出時會調(diào)用trafficcontrolservice的VehicleExitAsync：

 [HttpPost("exitcam")]
    public async Task<ActionResult> VehicleExitAsync(VehicleRegistered msg, [FromServices] DaprClient daprClient)
    {
        try
        {
            // get vehicle state
            var state = await _vehicleStateRepository.GetVehicleStateAsync(msg.LicenseNumber);
            if (state == default(VehicleState))
            {
                return NotFound();
            }

            // log exit
            _logger.LogInformation($"EXIT detected in lane {msg.Lane} at {msg.Timestamp.ToString("hh:mm:ss")} " +
                $"of vehicle with license-number {msg.LicenseNumber}.");

            // update state
            var exitState = state.Value with { ExitTimestamp = msg.Timestamp };
            await _vehicleStateRepository.SaveVehicleStateAsync(exitState);

            // handle possible speeding violation
            int violation = _speedingViolationCalculator.DetermineSpeedingViolationInKmh(exitState.EntryTimestamp, exitState.ExitTimestamp.Value);
            if (violation > 0)
            {
                _logger.LogInformation($"Speeding violation detected ({violation} KMh) of vehicle" +
                    $"with license-number {state.Value.LicenseNumber}.");

                var speedingViolation = new SpeedingViolation
                {
                    VehicleId = msg.LicenseNumber,
                    RoadId = _roadId,
                    ViolationInKmh = violation,
                    Timestamp = msg.Timestamp
                };

                // publish speedingviolation (Dapr publish / subscribe)
                await daprClient.PublishEventAsync("pubsub", "speedingviolations", speedingViolation);
            }

            return Ok();
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Error occurred while processing EXIT");
            return StatusCode(500);
        }
    }

如果存在超速的話會調(diào)用：

await daprClient.PublishEventAsync("pubsub", "speedingviolations", speedingViolation)

根據(jù)配置文件

apiVersion: dapr.io/v1alpha1
kind: Component
metadata:
  name: pubsub
  namespace: dapr-trafficcontrol
spec:
  type: pubsub.rabbitmq
  version: v1
  metadata:
  - name: host
    value: "amqp://localhost:5672"
  - name: durable
    value: "false"
  - name: deletedWhenUnused
    value: "false"
  - name: autoAck
    value: "false"
  - name: reconnectWait
    value: "0"
  - name: concurrency
    value: parallel
scopes:
  - trafficcontrolservice
  - finecollectionservice

可追蹤到消息的訂閱者是finecollectionservice。
（3）FineCollectionService

    [Topic("pubsub", "speedingviolations")]
    [Route("collectfine")]
    [HttpPost()]
    public async Task<ActionResult> CollectFine(SpeedingViolation speedingViolation, [FromServices] DaprClient daprClient)
    {
        decimal fine = _fineCalculator.CalculateFine(_fineCalculatorLicenseKey!, speedingViolation.ViolationInKmh);

        // get owner info (Dapr service invocation)
        var vehicleInfo = _vehicleRegistrationService.GetVehicleInfo(speedingViolation.VehicleId).Result;

        // log fine
        string fineString = fine == 0 ? "tbd by the prosecutor" : $"{fine} Euro";
        _logger.LogInformation($"Sent speeding ticket to {vehicleInfo.OwnerName}. " +
            $"Road: {speedingViolation.RoadId}, Licensenumber: {speedingViolation.VehicleId}, " +
            $"Vehicle: {vehicleInfo.Brand} {vehicleInfo.Model}, " +
            $"Violation: {speedingViolation.ViolationInKmh} Km/h, Fine: {fineString}, " +
            $"On: {speedingViolation.Timestamp.ToString("dd-MM-yyyy")} " +
            $"at {speedingViolation.Timestamp.ToString("hh:mm:ss")}.");

        // send fine by email (Dapr output binding)
        var body = EmailUtils.CreateEmailBody(speedingViolation, vehicleInfo, fineString);
        var metadata = new Dictionary<string, string>
        {
            ["emailFrom"] = "noreply@cfca.gov",
            ["emailTo"] = vehicleInfo.OwnerEmail,
            ["subject"] = $"Speeding violation on the {speedingViolation.RoadId}"
        };
        await daprClient.InvokeBindingAsync("sendmail", "create", body, metadata);

        return Ok();
    }

其中vehicleInfo 的值是通過service invocation調(diào)用VehicleRegistrationService獲取的。

最后通過Output Binding來發(fā)送郵件:

await daprClient.InvokeBindingAsync("sendmail", "create", body, metadata);

運行

  1. start-all.ps1
  2. dapr run --app-id vehicleregistrationservice --app-port 6002 --dapr-http-port 3602 --dapr-grpc-port 60002 --config ../dapr/config/config.yaml --components-path ../dapr/components dotnet run
  3. dapr run --app-id finecollectionservice --app-port 6001 --dapr-http-port 3601 --dapr-grpc-port 60001 --config ../dapr/config/config.yaml --components-path ../dapr/components dotnet run
  4. dapr run --app-id trafficcontrolservice --app-port 6000 --dapr-http-port 3600 --dapr-grpc-port 60000 --config ../dapr/config/config.yaml --components-path ../dapr/components dotnet run
  5. cd Simulation && dotnet run

最終結(jié)果：
[圖片上傳失敗...(image-c915c-1662870789547)]

車輛的進入退出信息都會實時捕獲到，如果有超速信息，會通過郵件發(fā)送。
[圖片上傳失敗...(image-878039-1662870789547)]

寫在最后

可視化版本

cd .\VisualSimulation\ && dotnet run

[圖片上傳失敗...(image-cee7e8-1662870789547)]

視頻可參見： https://live.csdn.net/v/238245

rabbitmq管理界面

默認賬號密碼都是guest。
[圖片上傳失敗...(image-db9747-1662870789547)]

公眾號

更多內(nèi)容，歡迎關(guān)注我的微信公眾號: 半夏之夜的無情劍客。
[圖片上傳失敗...(image-a6573f-1662870789547)]

?著作權(quán)歸作者所有,轉(zhuǎn)載或內(nèi)容合作請聯(lián)系作者
【社區(qū)內(nèi)容提示】社區(qū)部分內(nèi)容疑似由AI輔助生成，瀏覽時請結(jié)合常識與多方信息審慎甄別。
平臺聲明：文章內(nèi)容（如有圖片或視頻亦包括在內(nèi)）由作者上傳并發(fā)布，文章內(nèi)容僅代表作者本人觀點，簡書系信息發(fā)布平臺，僅提供信息存儲服務。

相關(guān)閱讀更多精彩內(nèi)容

友情鏈接更多精彩內(nèi)容