Basic Usage

Using task queue service

Setup

Include the spikeify-taskqueue.jar lib in your project or add a maven dependency:

<dependency>
    <groupId>com.spikeify</groupId>
    <artifactId>taskqueue</artifactId>
    <version>0.1.9</version>
</dependency>

Basic services

TaskQueueService

The DefaultTaskQueueService takes care of:

• adding new jobs to the queue
• getting the next job to be executed
• removing jobs from queue
• changing job state in its lifecycle

For most cases only the add(Job job, String queueName) method will be needed.

TaskQueueService - creating a job

Creating a new job is easy. Just inherit from the Job interface and implement TaskResult execute(TaskContext context) method.

public class SimpleJob implements Job {

	private int property;

	protected SimpleJob() {
		// for Jackson
	}

	public SimpleJob(int value) {
		setProperty(value);
	}

	public int getProperty() {
		return property;
	}

	public void setProperty(int value) {
		property = value;
	}

	@Override
	public TaskResult execute(TaskContext context) {

		// nothing to do right now ...
		if (context != null && context.interrupted()) {
			return TaskResult.interrupted();
		}

		return TaskResult.ok();
	}
}

Following must be considered:

• jobs should be small atomic tasks, not running more than a few minutes (currently 10 minutes by default)
• job execution order is not guaranteed so one job should not rely on some other job started in short sequence
• jobs get serialized and deserialized from to JSON string, only properties that are serialized can be used by the job in the execute method
• jobs must have a default (empty) constructor
• jobs must return a success or failed state (this is used by the queue service to re-run failed jobs)
• long running jobs should regularly check TaskContext if the interrupted() method returns true. If so the job has some time (10 seconds at the most) to end gracefully. Otherwise the job thread will be interrupted.

TaskQueueManager

Once a job has been added to the queue, the queue manager takes over:

• runs a scheduled check every 10 seconds checking is a new task is present in the queue
• once a task has been found, the task is executed
• if more tasks are found the execution continues
• successful or failed tasks are regularly purged from the queue (failed tasks stay longer in the queue to be inspected)
• queue manager also builds up running statistic for all completed or failed tasks

TaskQueueManager - job execution

In order to start queue following must be done:

• Register queue

TaskQueueService queues = new DefaultTaskQueueService(spikeify);
TaskQueueManager manager = new DefaultTaskQueueManager(spikeify, queues);
manager.register("myQueue", true);

• Start queue / check

manager.check("myQueue");

The check call should be triggered regularly via cron job on each instance where the queue service is running. It takes care of stopping/starting the queue service in case the service has been stopped or started on some other instance.

If you are running the queue service on only one instance then the check is not needed. Just start up the queue manually:

manager.start("myQueue");