JVM - queue.receive()

Receive tasks from a queue.

import io.nitric.Nitric;
import io.nitric.resources.QueuePermission;

public class Application {
  public static void main(String[] args) {
    var queue = Nitric.INSTANCE.queue("batch").with(QueuePermission.Send);

    var tasks = queue.receive(10);

    tasks.forEach((task) -> {
      // Work on a task...

      // Complete the task
      task.complete();
    });

    Nitric.INSTANCE.run();
  }
}

Parameters

Notes

Completing tasks

Since the process is async, the queue doesn't know when a task has been completed. So failed function/containers don't result in lost tasks, tasks are not removed from a queue when they're received.

Instead, tasks are hidden and receivers are granted a temporary lease for each task they receive.

When complete, the receiver must tell the queue the task was completed successfully, which will remove it from the queue and stop it being reprocessed.

To notify the queue that a task was completed call the complete() method on the task reference.

Receive depth

When calling receive() a depth parameter can be provided, e.g. receive(5). This will attempt to receive up to 5 tasks from the queue.

However, if the queue is empty or less than 5 tasks are available on the queue, then the max available will be returned.

This means calls to receive will return between 0 and depth tasks.

Examples

Receive tasks from a queue

import io.nitric.Nitric;
import io.nitric.resources.QueuePermission;

public class Application {
  public static void main(String[] args) {
    var queue = Nitric.INSTANCE.queue("batch").with(QueuePermission.Receive);

    var tasks = queue.receive(10);

    tasks.forEach((task) -> {
      // Work on a task...

      // Complete the task
      task.complete();
    });

    Nitric.INSTANCE.run();
  }
}