224 lines
7.2 KiB
Markdown
224 lines
7.2 KiB
Markdown
# 软件开发文档 - 04. 数据处理链设计
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本文档专门阐述当系统从S7 PLC等设备读取到变量值后，如何通过一个可扩展的、链式的处理流程，对数据进行加工、存储和转发。
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## 1. 设计目标
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* **解耦**：每个处理步骤应是独立的、可复用的。
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* **可扩展**：可以轻松地添加新的处理环节（例如：数据校验、报警判断、线性转换等）。
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* **高性能**：处理流程应高效，避免阻塞数据采集线程。
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* **可配置**：能够根据不同变量的需求，动态构建处理链。
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## 2. 核心概念：`VariableContext`
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为了在处理链中传递数据，我们定义一个上下文对象 `VariableContext`。它将携带变量的原始值、当前值以及其他相关信息，在整个处理链中流动。
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```csharp
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// 文件: DMS.Core/Models/VariableContext.cs
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namespace DMS.Core.Models;
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public class VariableContext
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{
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public Variable Variable { get; init; }
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public object RawValue { get; init; } // 从设备读取的原始值
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public object CurrentValue { get; set; } // 当前处理后的值
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public DateTime Timestamp { get; init; }
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public bool IsValueChanged { get; set; } // 标记值是否发生变化
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public bool IsProcessingTerminated { get; set; } // 是否终止后续处理
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public VariableContext(Variable variable, object rawValue)
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{
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Variable = variable;
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RawValue = rawValue;
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CurrentValue = rawValue;
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Timestamp = DateTime.UtcNow;
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}
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}
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```
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## 3. 处理器接口与抽象基类
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我们定义一个统一的处理器接口 `IVariableProcessor` 和一个实现了链式调用的抽象基类 `VariableProcessorBase`。
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### 3.1. `IVariableProcessor` 接口
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```csharp
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// 文件: DMS.Application/Interfaces/IVariableProcessor.cs
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namespace DMS.Application.Interfaces;
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public interface IVariableProcessor
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{
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IVariableProcessor SetNext(IVariableProcessor next);
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Task ProcessAsync(VariableContext context);
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}
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```
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### 3.2. `VariableProcessorBase` 抽象基类
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```csharp
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// 文件: DMS.Application/Services/Processors/VariableProcessorBase.cs
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namespace DMS.Application.Services.Processors;
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public abstract class VariableProcessorBase : IVariableProcessor
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{
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private IVariableProcessor _next;
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public IVariableProcessor SetNext(IVariableProcessor next)
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{
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_next = next;
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return next;
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}
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public virtual async Task ProcessAsync(VariableContext context)
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{
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if (context.IsProcessingTerminated) return;
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await HandleAsync(context);
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if (_next != null && !context.IsProcessingTerminated)
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{
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await _next.ProcessAsync(context);
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}
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}
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// 模板方法，由子类实现具体的处理逻辑
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protected abstract Task HandleAsync(VariableContext context);
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}
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```
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## 4. 具体处理器实现
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以下是处理链中几个核心处理器的设计。
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### 4.1. `ChangeDetectionProcessor` - 变化检测处理器
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**职责**：检测本次读取的值与上一次的值是否相同。如果相同，则终止后续处理，以节省资源。
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```csharp
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// 文件: DMS.Infrastructure/Services/Processors/ChangeDetectionProcessor.cs
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public class ChangeDetectionProcessor : VariableProcessorBase
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{
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private readonly IMemoryCache _cache; // 使用内存缓存来存储上一次的值
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public ChangeDetectionProcessor(IMemoryCache cache)
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{
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_cache = cache;
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}
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protected override Task HandleAsync(VariableContext context)
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{
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var lastValue = _cache.Get(context.Variable.Id);
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if (lastValue != null && lastValue.Equals(context.RawValue))
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{
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context.IsProcessingTerminated = true; // 值未变化，终止处理
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}
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else
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{
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context.IsValueChanged = true;
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_cache.Set(context.Variable.Id, context.RawValue, TimeSpan.FromDays(1));
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}
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return Task.CompletedTask;
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}
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}
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```
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### 4.2. `HistoryStorageProcessor` - 历史存储处理器
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**职责**：将变化后的值存入数据库历史记录表。
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```csharp
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// 文件: DMS.Infrastructure/Services/Processors/HistoryStorageProcessor.cs
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public class HistoryStorageProcessor : VariableProcessorBase
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{
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private readonly IVariableHistoryRepository _historyRepository;
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public HistoryStorageProcessor(IVariableHistoryRepository historyRepository)
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{
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_historyRepository = historyRepository;
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}
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protected override async Task HandleAsync(VariableContext context)
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{
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if (!context.IsValueChanged) return;
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var history = new VariableHistory
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{
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VariableId = context.Variable.Id,
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Value = context.CurrentValue.ToString(),
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Timestamp = context.Timestamp
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};
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await _historyRepository.AddAsync(history);
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}
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}
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```
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### 4.3. `MqttPublishProcessor` - MQTT发布处理器
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**职责**：如果变量关联了MQTT服务器，则将值发布出去。
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```csharp
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// 文件: DMS.Infrastructure/Services/Processors/MqttPublishProcessor.cs
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public class MqttPublishProcessor : VariableProcessorBase
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{
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private readonly IMqttPublishService _mqttService;
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private readonly IVariableRepository _variableRepository; // 用于获取关联的MQTT服务器
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public MqttPublishProcessor(IMqttPublishService mqttService, IVariableRepository variableRepository)
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{
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_mqttService = mqttService;
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_variableRepository = variableRepository;
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}
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protected override async Task HandleAsync(VariableContext context)
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{
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if (!context.IsValueChanged) return;
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var variableWithMqtt = await _variableRepository.GetVariableWithMqttServersAsync(context.Variable.Id);
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if (variableWithMqtt?.MqttServers == null) return;
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foreach (var server in variableWithMqtt.MqttServers)
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{
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if (server.IsActive)
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{
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var topic = $"DMS/{context.Variable.VariableTable.Device.Name}/{context.Variable.VariableTable.Name}/{context.Variable.Name}";
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var payload = System.Text.Json.JsonSerializer.Serialize(new { value = context.CurrentValue, timestamp = context.Timestamp });
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await _mqttService.PublishAsync(server, topic, payload);
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}
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}
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}
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}
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```
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## 5. 构建和执行处理链
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在数据采集的后台服务中，我们将动态构建并执行这个处理链。
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```csharp
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// 在 S7BackgroundService.cs 或类似服务中
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public class DataAcquisitionService
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{
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private readonly IServiceProvider _serviceProvider;
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public DataAcquisitionService(IServiceProvider serviceProvider)
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{
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_serviceProvider = serviceProvider;
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}
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public async Task OnDataReceived(Variable variable, object rawValue)
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{
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var context = new VariableContext(variable, rawValue);
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// 1. 从DI容器中获取处理器实例
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var changeDetector = _serviceProvider.GetRequiredService<ChangeDetectionProcessor>();
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var historian = _serviceProvider.GetRequiredService<HistoryStorageProcessor>();
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var publisher = _serviceProvider.GetRequiredService<MqttPublishProcessor>();
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// 2. 构建处理链
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changeDetector.SetNext(historian).SetNext(publisher);
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// 3. 启动处理
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await changeDetector.ProcessAsync(context);
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}
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}
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```
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