Cron 表达式:在 ASP.Net Core 中每天运行一次任务 [英] Cron expression: run task once per-day in ASP.Net Core

问题描述

我的asp.net核心程序需要收集所有访问网站的IP.

My asp.net core program needs to collect all the IP which access the website pre-day.

一天结束后我需要将IP列表输出到txt文件中.

I need to output the IP list to a txt file when a day is over.

因此，程序应该每天运行一次保存 IP 列表的方法.

Therefore, the program should run a method to save the IP list once per-day.

我应该如何设计它?

在我看来，我会在 startup.cs 中添加一个循环任务，并将 Task.Delay 设置为 24 小时(一天).

In my opinion, I will add a looping task in the startup.cs and set the Task.Delay to 24 hours(one day).

我应该这样做吗?谢谢.

Should I do it like this? Thank you.

推荐答案

这就是我在 ASP.Net Core 中实现调度程序任务的方式.请注意，您必须知道如何使用 cron epxression.

This is how I implement scheduler task in ASP.Net Core. Please note that you have to know how to use cron epxression.

首先在你的 csproj 中添加这个包

First add this package in your csproj

<PackageReference Include="ncrontab" Version="3.3.1" />

接下来我将创建SceduledProcessor.cs

Next I will create SceduledProcessor.cs

public abstract class ScheduledProcessor : ScopedProcessor
    {
        private readonly CrontabSchedule _schedule;
        private DateTime _nextRun;

        protected ScheduledProcessor(IServiceScopeFactory serviceScopeFactory) : base(serviceScopeFactory)
        {
            _schedule = CrontabSchedule.Parse(GetCronExpression(serviceScopeFactory));
            _nextRun = _schedule.GetNextOccurrence(DateTime.Now);
        }

        protected override async Task ExecuteAsync(CancellationToken stoppingToken)
        {
            do
            {
                var now = DateTime.Now;
                _schedule.GetNextOccurrence(now);

                if (now > _nextRun)
                {
                    await ProcessBackgroundTask();
                    _nextRun = _schedule.GetNextOccurrence(DateTime.Now);
                }

                await Task.Delay(5000, stoppingToken);
            }
            while (!stoppingToken.IsCancellationRequested);
        }

        protected abstract string GetCronExpression(IServiceScopeFactory serviceScopeFactory);
    }

将为我们的场景运行 ExecuteAsync

The ExecuteAsync will be run for our scenario

请注意，我们必须实现 GetCronExpression 方法

Please note that we have to implement GetCronExpression method

接下来我将实现服务类

public class ScheduledEmailService : ScheduledProcessor
    {
        public ScheduledEmailService(
            IServiceScopeFactory serviceScopeFactory) : base(serviceScopeFactory)
        {
        }

        /// <summary>
        /// Get cron setting from db
        /// </summary>
        /// <returns></returns>
        protected override string GetCronExpression(IServiceScopeFactory serviceScopeFactory)
        {
            return ""; // return your cron expression here you can get from db or static string
        }

        public override Task ProcessInScope(IServiceProvider serviceProvider)
        {
            // do something you wish
            return Task.CompletedTask;
        }
    }

奖励在这里我有预定义的 cron 表达式值的小班，你可以使用它

Bonus here I small class with predefined value for cron expression you can use it

public static class CronExpression
    {
        public static readonly string EveryMinute = "0 * * * * *";
        public static readonly string EveryDay = "0 0 0 * * *";
        public static readonly string EveryWeek = "0 0 * * 0";
        public static readonly string EveryWeekend = "0 0 0 * * 6,0";
    }

最后将其添加到您的 Startup.cs

Finally add this to your Startup.cs

services.AddSingleton<IHostedService, ScheduledEmailService>();

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