Kamyab7 / NCronJob

A Job Scheduler sitting on top of IHostedService in dotnet.

NCronJob

Scheduling made easy

NCronJob

A Job Scheduler sitting on top of IHostedService in dotnet.

Often times one finds themself between the simplicity of the BackgroundService/IHostedService and the complexity of a full blown Hangfire or Quartz scheduler. This library aims to fill that gap by providing a simple and easy to use job scheduler that can be used in any dotnet application and feels "native".

So no need for setting up a database, just schedule your stuff right away! The library gives you two ways of scheduling jobs:

1. Instant jobs - just run a job right away
2. Cron jobs - schedule a job using a cron expression

Features

• The ability to schedule jobs using a cron expression
• The ability to instantly run a job
• Parameterized jobs - instant as well as cron jobs!
• Integrated in ASP.NET - Access your DI container like you would in any other service
• Get notified when a job is done (either successfully or with an error).

Not features

As this is a simple scheduler, some features are not included by design. If you need these features, you might want to look into a more advanced scheduler like Hangfire or Quartz.

• Job persistence - Jobs are not persisted between restarts of the application.
• Job history - There is no history of jobs that have been run.
• Retries - If a job fails, it is not retried.
• Progress state - There is no way to track the progress of a job. The library will support notifying when a job is done, but not the progress of the job itself.
• The job scheduler always uses UTC time. We might change that in the future.

Short example

1. Import the namespace (or let your IDE do the dirty work)

using LinkDotNet.NCronJob;

2. Create a job

public class PrintHelloWorld : IJob
{
    private readonly ILogger<PrintHelloWorld> logger;

    public PrintHelloWorld(ILogger<PrintHelloWorld> logger)
    {
        this.logger = logger;
    }

    public Task RunAsync(JobExecutionContext context, CancellationToken token)
    {
        logger.LogInformation("Hello World");
        logger.LogInformation("Parameter: {Parameter}", context.Parameter);

        return Task.CompletedTask;
    }
}

3. Register the NCronJob and the job in your Program.cs

builder.Services.AddNCronJob();
builder.Services.AddCronJob<PrintHelloWorld>(options => 
{
    // Every minute
    options.CronExpression = "* * * * *";
    // Optional parameter
    options.Parameter = "Hello World";
});

4. Run your application and see the magic happen

Triggering an instant job

If the need arises and you want to trigger a job instantly, you can do so:

public class MyService
{
  private readonly IInstantJobRegistry jobRegistry;
  
  public MyService(IInstantJobRegistry jobRegistry) => this.jobRegistry = jobRegistry;

  public void MyMethod() => jobRegistry.AddInstantJob<MyJob>("I am an optional parameter");
}

Getting notified when a job is done

NCronJob provides a way to get notified when a job is done. For this, implement a IJobNotificationHandler<TJob> and register it in your DI container.

Services.AddNotificationHandler<MyJobNotificationHandler, MyJob>();

This allows to run logic after a job is done. The JobExecutionContext and the Exception (if there was one) are passed to the Handle method.

public class MyJobNotificationHandler : IJobNotificationHandler<MyJob>
{
    private readonly ILogger<MyJobNotificationHandler> logger;

    public MyJobNotificationHandler(ILogger<MyJobNotificationHandler> logger)
    {
        this.logger = logger;
    }

    public Task HandleAsync(JobExecutionContext context, Exception? exception, CancellationToken token)
    {
        if (exception is not null)
        {
            logger.LogError(exception, "Job failed");
        }
        else
        {
            logger.LogInformation("Job was successful");
            logger.LogInformation("Output: {Output}", context.Output);
        }

        return Task.CompletedTask;
    }
}

Advanced Cases

Isolation Level

By default, the jobs are run in the same scope as the scheduler. If there are long-running jobs that are synchronous, this might block the scheduler from running other jobs. To avoid this, you can set the IsolationLevel.

Services.AddCronJob<LongRunningJob>(options => 
{
    options.CronExpression = "* * * * *";
    options.IsolationLevel = IsolationLevel.Task;
});

You can achieve the same by using await Task.Yield() at the beginning your job, but this is a more explicit way of doing it.

Log Level

The NCronJob scheduler can be configured to log at a specific log level.

{
  "Logging": {
    "LogLevel": {
      "Default": "Information",
      "Microsoft.AspNetCore": "Warning",
      "LinkDotNet.NCronJob": "Debug"

Support & Contributing

Thanks to all contributors and people that are creating bug-reports and valuable input: