Work managers

A work manager is a thread pool created for J2EE applications that use asynchronous beans.

Using the administrative console, an administrator can configure any number of work managers. The administrator specifies the properties of the work manager, including the J2EE context inheritance policy for any asynchronous beans that use the work manager. The administrator binds each work manager to a unique place in Java Naming and Directory Interface (JNDI). Use work manager objects in any one of the following interfaces:

  • Asynchronous beans

  • CommonJ work manager (For details, see the CommonJ work manager section in this article.)

The selected type of interface is resolved during the JNDI lookup time. The interface type is the value that you specify in the ResourceRef, rather than the interface type specified in the configuration object. For example, one can have one ResourceRef for each interface per configuration object, and each ResourceRef lookup returns that appropriate type of instance.

The work managers provide a programming model for the J2EE 1.4 applications. For more information, see the Programming model section in this topic.

When writing a Web or EJB component that uses asynchronous beans, the developer should include a resource reference in each component that needs access to a work manager. For more information on resource references, see the topic References. The component looks up a work manager using a logical name in the component, java:comp namespace, just as it looks up a data source, enterprise bean, or connection factory.

The deployer binds physical work managers to logical work managers when the application is deployed.

For example, if a developer needs three thread pools to partition work between bronze, silver, and gold levels, the developer writes the component to pick a logical pool based on an attribute in the client application profile. The deployer has the flexibility to decide how to map this request for three thread pools. The deployer might decide to use a single thread pool on a small machine. In this case, the deployer binds all three resource references to the same work manager instance (that is, the same JNDI name). A larger machine might support three thread pools, so the deployer binds each resource reference to a different work manager. Work managers can be shared between multiple J2EE applications installed on the same server.

An application developer can use as many logical work managers as necessary. The deployer chooses whether to map one physical work manager or several to the logical work manager defined in the application.

All J2EE components that need to share asynchronous scope objects must use the same work manager. These scope objects have an affinity with a single work manager. An application that uses asynchronous scopes should verify that all of the components using scope objects use the same work manager.

When multiple work managers are defined, the underlying thread pools are created in a JVM only if an application within that Java virtual machine (JVM) looks up the work manager. For example, there might be ten thread pools (work managers) defined, but none are actually created until an application looks these pools up.

 

CommonJ Work Manager

The CommonJ work manager is similar to the work manager. The difference between the two is that the CommonJ work manager contains a subset of the asynchronous beans work manager methods. Although CommonJ work manager functions in a J2EE 1.4 environment, the interface does not return a new instance for each JNDI naming lookup, since this specification is not included in the J2EE specification.

Remote start of work. The CommonJ Work specification optional feature for work running remotely is not supported. Even if a unit of work implements the java.io.Serializable interface, the unit of work does not run remotely.

 

How to look up a work manager

An application can

look up a work manager as follows. Here, the component contains a resource reference named wm/myWorkManager, which was bound to a physical work manager when the component was deployed 

InitialContext ic = new InitialContext();
WorkManager wm = (WorkManager)ic.lookup("java:comp/env/wm/myWorkManager");

 

Inheritance J2EE contexts

Asynchronous beans can

inherit the following J2EE contexts.

Internationalization context

When this option is selected and the internationalization service is enabled, and the internationalization context that exists on the scheduling thread is available on the target thread.

Work area

When this option is selected, the work area context for every work area partition that exists on the scheduling thread is available on the target thread.

Application profile (deprecated)

When this option is selected, the application profile service is enabled, and the application profile service property, 5.x compatibility mode, is selected. The application profile task that is associated with the scheduling thread is available on the target thread for J2EE 1.3 applications. For J2EE 1.4 applications, the application profile task is a property of its associated unit of work, rather than a thread. This option has no effect on the behavior of the task in J2EE 1.4 applications. The scheduled work that runs in a J2EE 1.4 application does not receive the application profiling task of the scheduling thread.

Security

The asynchronous bean can be run as anonymous or as the client authenticated on the thread that created it. This behavior is useful because the asynchronous bean can do only what the caller can do. This action is more useful than a RUN_AS mechanism, for example, which prevents this kind of behavior. When you select the Security option, the JAAS subject that exists on the scheduling thread is available on the target thread. If not selected, the thread runs anonymously.

Component metadata

Component metadata is relevant only when the asynchronous bean is a simple Java object. If the bean is a J2EE component, such as an enterprise bean, the component metadata is active.

The contexts that can be inherited depend on the work manager used by the application that creates the asynchronous bean. Using the administrative console, the administrator defines the sticky context policy of a work manager by selecting the services on which the work manager is to be made available.

 

Programming model

Work managers support

the following programming models.

  • CommonJ Specification. The Application Server v6 CommonJ programming model uses the WorkManager and TimerManager to manage threads and timers asynchronously in the J2EE 1.4 environment.

  • Asynchronous beans and CommonJ specification extensions. The current asynchronous beans Event Source, asynchronous scopes, subsystem monitors and J2EEContext interfaces are a part of the CommonJ extension.

The following table describes the method mapping between the CommonJ and Asynchronous beans APIs. We can change the current asynchronous beans interfaces to use the CommonJ interface, while maintaining the same functions.

CommonJ package API Asynchronous beans package API
Work manager   Work manager  
Asynchronous beans Field - IMMEDIATE (long)   Field - IMMEDIATE (int)
  Field - INDEFINITE   Field - INDEFINITE
  schedule(Work) throws WorkException, IllegalArgumentException   startWork(Work) throws WorkException, IllegalArgumentException
  schedule(Work, WorkListener) throws WorkException, IllegalArgumentException

Note: Configure the work manager work timeout property to the value you previously specified as timeout_ms on startWork. The default timeout value is INDEFINITE.

  startWork(Work, timeout_ms, WorkListener) throws WorkException, IllegalArgumentException
  waitForAll(workItems, timeout_ms)   join(workItems, JOIN_AND, timeout_ms)
  waitForAny(workItems, timeout_ms)   join(workItems, JOIN_OR, timeout_ms)
WorkItem   WorkItem  
  getResult   getResult
  getStatus   getStatus
WorkListener   WorkListener  
  workAccepted(WorkEvent)   workAccepted(WorkEvent)
  workCompleted(WorkEvent)   workCompleted(WorkEvent)
  workRejected(WorkEvent)   workRejected(WorkEvent)
  workStarted(WorkEvent)   workStarted(WorkEvent)
WorkEvent   WorkEvent  
  Field - WORK_ACCEPTED   Field - WORK_ACCEPTED
  Field - WORK_COMPLETED   Field - WORK_COMPLETED
  Field - WORK_REJECTED   Field - WORK_REJECTED
  Field - WORK_STARTED   Field - WORK_STARTED
  getException   getException
  getType   getType
  getWorkItem().getResult()

Note: This API is valid only after the work is complete.

  getWork
Work (extends Runnable) Work (Extends Runnable)
  isDaemon   *
  release   release
RemoteWorkItem Not in this release. Use Distributed WorkManager in XD or future release NA  
TimerManager   AlarmManager  
  resume   *
  schedule(Listener, Date)   create(Listener, context, time) ** need to convert the parameters
  schedule(Listener, Date, period)    
  schedule(Listener, delay, period)    
  scheduleAtFixedRate(Listener, Date, period)    
  scheduleAtFixedRate(Listener, delay, period)    
  stop    
  suspend    
Timer   Alarm  
  cancel   cancel
  getPeriod    
  getTimerListener   getAlarmListener
  scheduledExecutionTime    
TimerListener   AlarmListener  
  timerExpired(timer)   fired(alarm)
StopTimerListener   Not applicable  
  timerStop(timer)    
CancelTimerListener   Not applicable  
  timerCancel(timer)    
WorkException (Extends Exception) WorkException (Extends WsException)
WorkCompletedException (Extends WorkException) WorkCompletedException (Extends WorkException)
WorkRejectedException (Extends WorkException) WorkRejectedException (Extends WorkException)
For more information on work manager APIs, refer to the Javadoc.

 

Work manager examples

Table 1. Look up work manager
Asynchronous beans CommonJ 
InitialContext ctx  = new InitialContext();
com.ibm.websphere.asynchbeans.WorkManager wm  =
(com.ibm.websphere.asynchbeans.WorkManager)
         ctx.lookup(“java:comp/env/wm/MyWorkMgr”);

InitialContext ctx  = new InitialContext();
commonj.work.WorkManager wm = (commonj.work.WorkManager)
       ctx.lookup(“java:comp/env/wm/MyWorkMgr”);

Table 2. Create your work using MyWork
Asynchronous beans CommonJ 
public class MyWork implements   
com.ibm.websphere.asynchbeans.Work {
public void release() {
              ......
       }
     public void run() {
        System.out.println(“Running.....”);
    }


public class MyWork implements 
commonj.work.Work{
     public boolean isDaemon() {
         return false;
     }
     public void release () {
          .....
      }
    public void run () {
       System.out.println(“Running.....”);
    }

Table 3. Submit the work
Asynchronous beans CommonJ 
  MyWork work1 = new MyWork(new URI =
“http://www.example./com/1”);
  MyWork work2 = new MyWork(new URI =
“http://www.example./com/2”);
  
  WorkItem item1;
  WorkItem item2;
  Item1=wm.startWork(work1);
  Item2=wm.startWork(work2);
  
  // case 1: block until all items are done
  ArrayList col1 = new ArrayList();
  Col1.add(item1);
  Col1.add(item2);
  wm.join(col1, WorkManager.JOIN_AND, (long)WorkManager.IMMEDIATE);
  // when the works are done
  System.out.println(“work1 data=”+work1.getData());
  System.out.println(“work2 data=”+work2.getData());
  
  // case 2: wait for any of the items to complete.
  Boolean ret = wm.join(col1,                           WorkManager.JOIN_OR, 1000);


  MyWork work1 = new MyWork(new URI = 
“http://www.example./com/1”);
  MyWork work2 = new MyWork(new URI =
“http://www.example./com/2”);
  
  WorkItem item1;
  WorkItem item2;
  Item1=wm.schedule(work1 );
  Item2=wm.schedule(work2);
  
  // case 1: block until all items are done
  Collection col1 = new ArrayList();
  col1.add(item1);
  col1.add(item2);
  wm.waitForAll(col1, WorkManager.IMMEDIATE);
  // when the works are done
  System.out.println(“work1 data=”+work1.getData());
  System.out.println(“work2 data=”+work2.getData());
  
  
  // case 2: wait for any of the items to complete.
  Collection finished = wm.waitForAny(col1,                           1000);
  // check the workItems status
  if (finished != null) {
    Iterator I = finished.iterator();
    if (i.hasNext()) {
       WorkItem wi = (WorkItem) i.next();
        if (wi.equals(item1)) {
          System.out.println(“work1 = “+ work1.getData());
        } else if (wi.equals(item2)) {
          System.out.println(“work1 = “+ work1.getData());
        }
    }
  }

Table 4. Create a timer manager
Asynchronous beans CommonJ 
  InitialContext ctx  = new InitialContext();
  com.ibm.websphere.asynchbeans.WorkManager wm  =
      (com.ibm.websphere.asynchbeans.WorkManager)
        ctx.lookup(“java:comp/env/wm/MyWorkMgr”);
  
  AsynchScope ascope;
  Try {
    Ascope = wm.createAsynchScope(“ABScope”);
  } Catch (DuplicateKeyException ex)
  {
     Ascope = wm.findAsynchScope(“ABScope”);
     ex.printStackTrace();
  }
  
  // get an AlarmManager 
  AlarmManager  aMgr= ascope.getAlarmManager();

  InitialContext ctx  = new InitialContext();
  Commonj.timers.TimerManager tm = (commonj.timers.TimerManager) ctx.lookup(“java:comp/env/tm/MyTimerManager”);

Table 5. Fire the timer
Asynchronous beans CommonJ 
  // create alarm
  ABAlarmListener listener = new ABAlarmListener();
  Alarm am = aMgr.create(listener, “SomeContext”, 1000*60);


  // create Timer
  TimerListener listener = new StockQuoteTimerListener(“qqq”, “johndoe@example.com”);
  Timer timer = tm.schedule(listener, 1000*60);
  
  // Fixed-delay: schedule timer to expire in 60 seconds 
  // from now and repeat every hour thereafter.  
  Timer timer = tm.schedule(listener, 1000*60, 1000*30);
  
  // Fixed-rate: schedule timer to expire in 60 seconds
  // from now and repeat every hour thereafter
  Timer timer = tm.scheduleAtFixedRate(listener, 1000*60, 1000*30);

 

Related Tasks


Configuring work managers