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在Quartz.Net中使用Scoped Service

news 来源：原创 2024/9/19 9:03:41

refs:

Creating a Quartz.NET hosted service with ASP.NET Core

Using scoped services inside a Quartz.NET hosted service with ASP.NET Core

本文基于上面2个链接的文章翻译攥写。

在Quartz.Net中无法使用scoped service比如DbContext，一般IJob只能是单例模式或Transient模式；

1）为了使用scoped servcie 一般是注入IServiceProvice，然后创建scope环境获取实例。

比如:

public class EmailReminderJob : IJob
{private readonly IServiceProvider _provider;public EmailReminderJob( IServiceProvider provider){_provider = provider;}public Task Execute(IJobExecutionContext context){using(var scope = _provider.CreateScope()){var dbContext = scope.ServiceProvider.GetService<AppDbContext>();var emailSender = scope.ServiceProvider.GetService<IEmailSender>();// fetch customers, send email, update DB}return Task.CompletedTask;}
}

在很多场景下这个是可行的，此时IJob依然在DI中是单例模式。

2）创建一个辅助任务

不直接在IJob中实现，而是通过一个QuartzJobRunner的任务间接实现，在次任务中创建新的任务来实现；

QuartzJobRunner.依然是单例模式,这样就不用担心会被 disposed掉.

services.AddSingleton<QuartzJobRunner>();

在QuartzJobRunner中创建一个实例化的新IJob并执行:

using Microsoft.Extensions.DependencyInjection;
using Quartz;
using System;
using System.Threading.Tasks;public class QuartzJobRunner : IJob
{private readonly IServiceProvider _serviceProvider;public QuartzJobRunner(IServiceProvider serviceProvider){_serviceProvider = serviceProvider;}public async Task Execute(IJobExecutionContext context){using (var scope = _serviceProvider.CreateScope()){var jobType = context.JobDetail.JobType;var job = scope.ServiceProvider.GetRequiredService(jobType) as IJob;await job.Execute(context);}}
}

这么做有2个优点:

我们注册EmailReminderJob 为scoped service,并直接注入依赖到其构造方法中；
我们可以将其他跨领域问题转移到QuartzJobRunner类中.

由于job的实例源自 scoped IServiceProvder,所以可以在构造方法中使用 scoped services。

如果你不熟悉DI范围问题，那么理解这些问题可能会很棘手。

[DisallowConcurrentExecution]
public class EmailReminderJob : IJob
{private readonly AppDbContext _dbContext;private readonly IEmailSender _emailSender;public EmailReminderJob(AppDbContext dbContext, IEmailSender emailSender){_dbContext = dbContext;_emailSender = emailSender;}public Task Execute(IJobExecutionContext context){// fetch customers, send email, update DBreturn Task.CompletedTask;}
}

这些 IJob 实现可以注册为任何生命周期(scoped or transient)，当然 JobSchedule 依然是单例:

services.AddScoped<EmailReminderJob>();
services.AddSingleton(new JobSchedule(jobType: typeof(EmailReminderJob),cronExpression: "0 0 12 * * ?")); // every day at noon

QuartzJobRunner 处理跨界问题。

This example is obviously very basic. If the code here looks ok to you, I suggest watching Jimmy Bogard's "Six Little Lines of Fail" talk, which describes some of the issues!

public class QuartzJobRunner : IJob
{private readonly IServiceProvider _serviceProvider;public QuartzJobRunner(IServiceProvider serviceProvider){_serviceProvider = serviceProvider;}public async Task Execute(IJobExecutionContext context){using (var scope = _serviceProvider.CreateScope()){var jobType = context.JobDetail.JobType;var job = scope.ServiceProvider.GetRequiredService(jobType) as IJob;var dbContext = scope.ServiceProvider.GetRequiredService<AppDbContext>();var messageBus = scope.ServiceProvider.GetRequiredService<IBus>();await job.Execute(context);// job completed, save dbContext changesawait dbContext.SaveChangesAsync();// db transaction succeeded, send messagesawait messageBus.DispatchAsync();}}
}

QuartzJobRunner 以上实现类似前面的，但是我们创建job后，从DI容器中获取了 DbContext和messageBus，等执行完job后再保存到db并且发送消息到事件总线。 .

把这些方法放在 QuartzJobRunner 中可以减少在具体 IJob中的实现，并且更容易实现其他模式。

这里展示的方法（使用中间的QuartzJobRunner类），主要有两个原因：