Jobs.md

Jobs

A job is basically a task that you either don't want to execute in the current context, on the current server or execute at a later time. EventFlow provides basic functionality for jobs.

There are areas where you might find jobs very useful, here are some examples

• Publish a command at a specific time in the future
• Transient error handling

var jobScheduler = resolver.Resolve<IJobScheduler>();
var job = PublishCommandJob.Create(new SendEmailCommand(id), resolver);
await jobScheduler.ScheduleAsync(
  job,
  TimeSpan.FromDays(7),
  CancellationToken.None)
  .ConfigureAwait(false);

In the above example the SendEmailCommand command will be published in seven days.

Be careful when using jobs

When working with jobs, you should be aware of the following

• The default implementation does executes the job now, i.e., in the current context. To get another behavior, install e.g. EventFlow.Hangfire to get support for scheduled jobs. Read below for details on how to configure Hangfire
• Your jobs should serialize to JSON properly, see the section on value objects for more information
• If you use the provided PublishCommandJob, make sure that your commands serialize properly as well

Create your own jobs

To create your own jobs, your job merely needs to implement the IJob interface and be registered in EventFlow.

Here's an example of a job implementing IJob

[JobVersion("LogMessage", 1)]
public class LogMessageJob : IJob
{
  public LogMessageJob(string message)
  {
    Message = message;
  }

  public string Message { get; }

  public Task ExecuteAsync(
    IResolver resolver,
    CancellationToken cancellationToken)
  {
    var log = resolver.Resolve<ILog>();
    log.Debug(Message);
  }
}

Note that the JobVersion attribute specifies the job name and version to EventFlow and this is how EventFlow distinguishes between the different job types. This makes it possible for you to reorder your code, even rename the job type, as long as you keep the same attribute values its considered the same job in EventFlow. If the attribute is omitted, the name will be the type name and version will be 1.

Here's how the job is registered in EventFlow.

var resolver = EventFlowOptions.new
  .AddJobs(typeof(LogMessageJob))
  ...
  .CreateResolver();

Then to schedule the job

var jobScheduler = resolver.Resolve<IJobScheduler>();
var job = new LogMessageJob("Great log message");
await jobScheduler.ScheduleAsync(
  job,
  TimeSpan.FromDays(7),
  CancellationToken.None)
  .ConfigureAwait(false);

Hangfire

To use Hangfire as the job scheduler, install the NuGet package EventFlow.Hangfire and configure EventFlow to use the scheduler like this.

var resolver = EventFlowOptions.new
  .UseHangfireJobScheduler() // This line
  ...
  .CreateResolver();

Note that the UseHangfireJobScheduler() doesn't do any Hangfire configuration, but merely registers the proper scheduler in EventFlow.