Use schedulers

 

Overview

Schedulers enable J2EE application tasks to run at a requested time. We can schedule the following types of tasks:

  • Invoke a session bean method

  • Send a Java Message Service (JMS) message to a queue or topic

Schedulers also enable application developers to create their own stateless session EJB components to receive event notifications during a task life cycle, allowing the plugging-in of custom logging utilities or workflow applications. Stateless session EJB components are also used to provide generic calendaring. Developers can either use the supplied calendar bean or create their own for their existing business calendars. For example, one of your business processes might involve invoicing for services. With the scheduler's use of stateless EJB components, one can schedule when periodic email distributions are to be sent to your customers who have received invoices. The scheduler service performs these tasks, repeating as necessary, according to the metadata for that task.

A scheduler is the mechanism by which the timer service for Enterprise Java Beans 2.1 runs. One can configure the EJB timer service to use many of the features that schedulers provide. See the timer service for Enterprise Java Beans 2.1 documentation for more details.

Use the following table to determine which persistent timer service is best for you:

Schedulers EJB timers
Run stateless session EJB components and sends JMS messages Run all EJB types except for stateful session beans
Persistent, transactional and highly available. Persistent, transactional and highly available.
Tasks guaranteed to run only once Timers guaranteed to run only once, if the timer EJB uses a container-managed global transaction
Run repeating tasks using any calculation rules Run repeating tasks using a repeating interval defined in milliseconds
Uses a modified fixed-delay time calculation to determine repeating intervals (next run time based on the start-time of the previous task) Uses a fixed-rate time calculation to determine repeating intervals (time of the next task is based on the original scheduled time).
Programmatic task monitoring capability with the use of the NotificationSink stateless session EJB No programmatic timer monitoring
Abort late or time-sensitive tasks from running Abort late or time-sensitive tasks from running (achieved through manual detection within the javax.ejb.TimedObject implementation).
Manage any task lifecycle (find, suspend, resume, cancel and purge tasks programmatically and through Java Management Extensions (JMX)). Find and cancel its timers programmatically. Administrators find and cancel timers using a command-line utility.
Store a limited amount of text with the data, like a Name (arbitrary data stored externally.) Store arbitrary data with a timer

This task demonstrates how to manage, develop and interoperate with schedulers and subsequent tasks.

 

Procedure

  1. Manage the scheduler service. This article includes instructions for creating and configuring schedulers, creating and configuring a database for schedulers and administering schedulers.

  2. Develop and schedule tasks. This article includes instructions for developing various types of tasks, receiving notifications from a task, submitting tasks to a scheduler, and managing tasks.

    Note: Creating and manipulating scheduled tasks through the Scheduler API interface is only supported from within the Enterprise Java Beans (EJB) container or Web container (JavaServer Pages or servlets). Looking up and using a configured scheduler from a Java 2 Platform Enterprise Edition (J2EE) application client container is not supported.

  3. Interoperate with schedulers. This article explains how to manage scheduler in a clustered environment with mixed WAS product versions and mixed platforms.

 

See also


Manage schedulers
Developing and scheduling tasks
Scheduler daemon
Interoperating with schedulers