ASP.NET Core+Quartz.Net实现web定时任务

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作为一枚后端程序狗，项目实践常遇到定时任务的工作，最容易想到的的思路就是利用Windows计划任务/wndows service程序/Crontab程序等主机方法在主机上部署定时任务程序/脚本。

但是很多时候，使用的是共享主机或者受控主机，这些主机不允许你私自安装exe程序、Windows服务程序。

web程序中做定时任务，目前有两个方向：

① ASP.NET Core自带的HostService，这是一个轻量级的后台服务，需要搭配timer完成定时任务
②老牌Quartz.Net组件，支持复杂灵活的Scheduling、支持ADO/RAM Job任务存储、支持集群、支持监听、支持插件。

此处我们的项目使用稍复杂的Quartz.net实现web定时任务。

项目背景

最近需要做一个计数程序：采用redis计数，设定每小时将当日累积数据持久化到关系型数据库sqlite。

添加Quartz.Net Nuget依赖包
<PackageReference Include="Quartz" Version="3.0.6" />

① 定义定时任务内容：Job
② 设置触发条件：Trigger
③ 将Quartz.Net集成进ASP.NET Core

头脑风暴

IScheduler类包装了上述背景需要完成的第①②点工作，
SimpleJobFactory工厂类定义了生成Job任务的过程：利用反射机制调用无参构造函数形成的Job实例

//----------------选自Quartz.Simpl.SimpleJobFactory类-------------
using System;
using Quartz.Logging;
using Quartz.Spi;
using Quartz.Util;
namespace Quartz.Simpl
{/// <summary>/// The default JobFactory used by Quartz - simply calls/// <see cref="ObjectUtils.InstantiateType{T}" /> on the job class./// </summary>public class SimpleJobFactory : IJobFactory{private static readonly ILog log = LogProvider.GetLogger(typeof (SimpleJobFactory));/// <summary>/// Called by the scheduler at the time of the trigger firing, in order to/// produce a <see cref="IJob" /> instance on which to call Execute./// </summary>public virtual IJob NewJob(TriggerFiredBundle bundle, IScheduler scheduler){IJobDetail jobDetail = bundle.JobDetail;Type jobType = jobDetail.JobType;try{if (log.IsDebugEnabled()){log.Debug($"Producing instance of Job '{jobDetail.Key}', class={jobType.FullName}");}return ObjectUtils.InstantiateType<IJob>(jobType);}catch (Exception e){SchedulerException se = new SchedulerException($"Problem instantiating class '{jobDetail.JobType.FullName}'", e);throw se;}}/// <summary>/// Allows the job factory to destroy/cleanup the job if needed./// No-op when using SimpleJobFactory./// </summary>public virtual void ReturnJob(IJob job){var disposable = job as IDisposable;disposable?.Dispose();}}
}//------------------节选自Quartz.Util.ObjectUtils类-------------------------public static T InstantiateType<T>(Type type)
{if (type == null){throw new ArgumentNullException(nameof(type), "Cannot instantiate null");}ConstructorInfo ci = type.GetConstructor(Type.EmptyTypes);if (ci == null){throw new ArgumentException("Cannot instantiate type which has no empty constructor", type.Name);}return (T) ci.Invoke(new object[0]);
}

很多时候，定义的Job任务依赖了其他服务(该Job定义有参构造函数)，此时默认的SimpleJobFactory不能满足实例化要求，考虑自定义Job工厂类。

关键思路：
① Quartz.Net提供IJobFactory接口，以便开发者定义灵活的Job工厂类

JobFactories may be of use to those wishing to have their application produce IJob instances via some special mechanism, such as to give the opportunity for dependency injection

② ASP.NET Core是以依赖注入为基础的，利用ASP.NET Core内置依赖注入容器IServiceProvider管理Job的实例化依赖

编码实践

已经定义好Job类：UsageCounterSyncJob

自定义Job工厂类:IOCJobFactory

   /// <summary>/// IOCJobFactory ：在Timer触发的时候产生对应Job实例/// </summary>public class IOCJobFactory : IJobFactory{protected readonly IServiceProvider Container;public IOCJobFactory(IServiceProvider container){Container = container;}//Called by the scheduler at the time of the trigger firing, in order to produce//     a Quartz.IJob instance on which to call Execute.public IJob NewJob(TriggerFiredBundle bundle, IScheduler scheduler){return Container.GetService(bundle.JobDetail.JobType) as IJob;}// Allows the job factory to destroy/cleanup the job if needed.public void ReturnJob(IJob job){}}

在Quartz启动过程中应用自定义Job工厂

   public class QuartzStartup{public IScheduler _scheduler { get; set; }private readonly ILogger _logger;private readonly IJobFactory iocJobfactory;public QuartzStartup(IServiceProvider IocContainer, ILoggerFactory loggerFactory){_logger = loggerFactory.CreateLogger<QuartzStartup>();iocJobfactory = new IOCJobFactory(IocContainer);var schedulerFactory = new StdSchedulerFactory();_scheduler = schedulerFactory.GetScheduler().Result;_scheduler.JobFactory = iocJobfactory;}// Quartz.Net启动后注册job和triggerpublic void Start(){_logger.LogInformation("Schedule job load as application start.");_scheduler.Start().Wait();var UsageCounterSyncJob = JobBuilder.Create<UsageCounterSyncJob>().WithIdentity("UsageCounterSyncJob").Build();var UsageCounterSyncJobTrigger = TriggerBuilder.Create().WithIdentity("UsageCounterSyncCron").StartNow().WithCronSchedule("0 0 * * * ?")      // Seconds,Minutes,Hours，Day-of-Month，Month，Day-of-Week，Year（optional field）.Build();_scheduler.ScheduleJob(UsageCounterSyncJob, UsageCounterSyncJobTrigger).Wait();_scheduler.TriggerJob(new JobKey("UsageCounterSyncJob"));}public void Stop(){if (_scheduler == null){return;}if (_scheduler.Shutdown(waitForJobsToComplete: true).Wait(30000))_scheduler = null;else{}_logger.LogCritical("Schedule job upload as application stopped");}}

结合ASP.NET Core依赖注入；web启动时绑定Quartz.Net

//-------------------------------截取自Startup文件------------------------
......
services.AddTransient<UsageCounterSyncJob>();      // 这里使用瞬时依赖注入
services.AddSingleton<QuartzStartup>();
......// 绑定Quartz.Net
public void Configure(IApplicationBuilder app, Microsoft.AspNetCore.Hosting.IApplicationLifetime lifetime, ILoggerFactory loggerFactory)
{var quartz = app.ApplicationServices.GetRequiredService<QuartzStartup>();lifetime.ApplicationStarted.Register(quartz.Start);lifetime.ApplicationStopped.Register(quartz.Stop);
}

以上：我们对接ASP.NET Core依赖注入框架实现了一个自定义的JobFactory，每次任务触发时创建瞬时Job.

Github地址：https://github.com/zaozaoniao/ASPNETCore-Quartz.NET.git

附：IIS网站低频访问导致工作进程进入闲置状态的解决办法

IIS为网站默认设定了20min闲置超时时间：20分钟内没有处理请求、也没有收到新的请求，工作进程就进入闲置状态。

IIS上低频web访问会造成工作进程关闭，此时应用程序池回收，Timer等线程资源会被销毁；
当工作进程重新运作，Timer可能会重新生成，但我们的设定的定时Job可能没有按需正确执行。

故为IIS站点实现低频web访问下的定时任务：可设置IdleTimeOut =0；将[应用程序池]->[正在回收]->不勾选[回收条件]

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