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.net core 3.1 服务承载【BackgroundService】

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分类: .net后台框架

![.netcore](https://img.tnblog.net/arcimg/hb/c857299a86d84ee7b26d181a31e58234.jpg ".netcore")
>#.net core 3.1 服务承载【BackgroundService】
[TOC]

目录
------------

tn>https://www.tnblog.net/hb/article/details/5591

内容
------------

tn>在`.net core 2.1`后出了一个抽象类`BackgroundService`实现了`IHostedService`类的功能，并通过实现`ExecuteAsync`抽象方法实现后台长时间执行的效果。这里我们使用`PerformanceMetricsBackgroundService`的类去实现`BackgroundService`这个抽象类的`ExecuteAsync`方法，去实现与`PerformanceMetricsCollector`一样的效果。


```csharp
public class PerformanceMetricsBackgroundService : BackgroundService
{

    private readonly IProcessorMetricsCollector _processorMetricsCollector;
    private readonly INetworkMetricsCollector _networkMetricsCollector;
    private readonly IMetricsDeliverer _metricsDeliverer;
    private readonly IMemoryMetricsCollector _memoryMetricsCollector;
    private readonly IOptions<MetricsCollectionOptions> _optionsAccessor;
    private readonly ILogger<PerformanceMetricsBackgroundService> _logger;

    public PerformanceMetricsBackgroundService(
        IProcessorMetricsCollector processorMetricsCollector,
        INetworkMetricsCollector networkMetricsCollector,
        IMetricsDeliverer metricsDeliverer,
        IMemoryMetricsCollector memoryMetricsCollector,
        IOptions<MetricsCollectionOptions> optionsAccessor,
        ILogger<PerformanceMetricsBackgroundService> logger
        )
    {
        _processorMetricsCollector = processorMetricsCollector;
        _networkMetricsCollector = networkMetricsCollector;
        _metricsDeliverer = metricsDeliverer;
        _memoryMetricsCollector = memoryMetricsCollector;
        _optionsAccessor = optionsAccessor;
        _logger = logger;
    }

    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
    {
        while (!stoppingToken.IsCancellationRequested)
        {
            try
            {
                // 执行的方法
                await Callback();
            }
            catch (Exception ex)
            {
                _logger.LogError(ex,$"Job {nameof(PerformanceMetricsBackgroundService)} threw an exception!");
            }
            // 间隔的时间
            await Task.Delay(_optionsAccessor.Value.CaptureInterval);
        }
    }

    private async Task Callback()
    {
        // 通过不同指标获取实例
        var performanceMetrics = new PerformanceMetrics()
        {
            Memory = _memoryMetricsCollector.GetUsage(),
            Network = _networkMetricsCollector.GetThroughput(),
            Processor = _processorMetricsCollector.GetUsage()
        };
        await _metricsDeliverer.DeliverAsync(performanceMetrics);
    }
}
```

tn>注册服务

```csharp
.AddSingleton<IHostedService, PerformanceMetricsBackgroundService>()
```

tn>测试

![](https://img.tnblog.net/arcimg/hb/20b4ca97ade947069d2e9bfb87ef34ae.png)

tn>我们来分析一下`BackgroundService`的源代码

![](https://img.tnblog.net/arcimg/hb/139210ac9f4649579d1b31cefa1004d8.png)

BackgroundService的优点
------------

| 优点  |
| ------------ |
| 可以快速的实现后台任务  |
| 不会阻塞应用启动（除非重写`StartAsync`）  |


BackgroundService的缺点
------------

| 缺点  |
| ------------ |
| 不适合占用资源多的后台任务  |
| 不适合实现太多的后台任务（可能会影响性能）  |
| Web应用水平扩展时会遇到幂等性问题  |

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.net core 3.1 服务承载【BackgroundService】

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