Scheduling jobs

Sometimes you may want to postpone a method invocation; for example, to send an email to newly registered users a day after their registration. To do this, just call the BackgroundJob.schedule method and pass the desired delay:

BackgroundJob.schedule<EmailService>(Instant.now().plus(24, ChronoUnit.HOURS), 
  x -> x.sendNewlyRegisteredEmail());

You can also use the JobBuilder to achieve the same result:

BackgroundJob.create(aJob()
    .withName("Send welcome email to newly registered users")
    .scheduleIn(Duration.ofDays(1))
    .<EmailService>withDetails(x -> x.sendNewlyRegisteredEmail()));

JobRunr’s BackgroundJobServer periodically checks all scheduled jobs and enqueues them when it is time to run them, allowing workers to execute them. By default, the poll interval is equal to 15 seconds, but you can change it by passing the relevant argument to the BackgroundJobServer constructor or by changing the properties for your preferred framework.

The BackgroundJob.schedule methods has overloads and accepts:

• a ZonedDateTime
• an OffsetDateTime
• a LocalDateTime
• and an Instant

All DateTime objects are converted to an Instant - in case of the LocalDateTime, the systemDefault zoneId is used to convert it.

All of the above methods are of course also available on the JobScheduler bean and the JobRequestScheduler.

@Inject
private JobScheduler jobScheduler;

jobScheduler.schedule<EmailService>(Instant.now().plus(24, ChronoUnit.HOURS), 
  x -> x.sendNewlyRegisteredEmail());

@Inject
private JobRequestScheduler jobRequestScheduler;

jobRequestScheduler.schedule(Instant.now().plus(24, ChronoUnit.HOURS), 
  new SendNewlyRegisteredEmailJobRequest());

@Inject
private JobRequestScheduler jobRequestScheduler;

jobRequestScheduler.create(aJob()
  .scheduleIn(Duration.ofDays(1))
  .withJobRequest(new SendNewlyRegisteredEmailJobRequest()));

If you make use of the Carbon Aware API, you can add margins to the schedule: see the carbon aware jobs docs.

Note that scheduled jobs may not be executed on the exact moment you specified: whenever JobRunr fetches all the jobs that are scheduled and need to be executed, it fetches all jobs that need to happen in the next poll interval and enqueues them immediately. This may result in a difference of a couple of seconds. If you need real-time scheduling, then have a look at JobRunr Pro.