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package javax.resource.spi.work;
import java.lang.Object;
import java.lang.Runnable;
import java.lang.Exception;
import java.lang.Throwable;
/**
* This interface models a <code>WorkManager</code> which provides a facility
* to submit <code>Work</code> instances for execution. This frees the user
* from having to create Java threads directly to do work. Further, this
* allows efficient pooling of thread resources and more control over thread
* usage.
*
* The various stages in <code>Work</code> processing are:
* <ul>
* <li> work submit: A <code>Work</code> instance is being submitted for
* execution. The <code>Work</code> instance could either be accepted or
* rejected with a <code>WorkRejectedException</code> set to an appropriate
* error code. </li>
*
* <li> work accepted: The submitted <code>Work</code> instance has been
* accepted. The accepted <code>Work</code> instance could either start
* execution or could be rejected again with a
* <code>WorkRejectedException</code> set to an appropriate error code.
* There is no guarantee on when the execution would start unless a start
* timeout duration is specified. When a start timeout is specified, the
* <code>Work</code> execution must be started within the specified
* duration (not a real-time guarantee), failing which a
* <code>WorkRejectedException</code> set to an error code
* (<code>WorkRejected.TIMED_OUT</code>) is thrown. </li>
*
* <li> work rejected: The <code>Work</code> instance has been rejected.
* The <code>Work</code> instance could be rejected during <code>Work</code>
* submittal or after the <code>Work</code> instance has been accepted
* (but before Work instance starts execution). The rejection could be due
* to internal factors or start timeout expiration. A
* <code>WorkRejectedException</code> with an appropriate error code
* (indicates the reason) is thrown in both cases. </li>
*
* <li> work started: The execution of the <code>Work</code>
* instance has started. This means that a thread
* has been allocated for its execution. But this
* does not guarantee that the allocated thread has been scheduled to run
* on a CPU resource. Once execution is started, the allocated thread
* sets up an appropriate execution context (transaction , security, etc)
* and calls Work.run(). Note, any exception thrown during execution context
* setup or Work.run() leads to completion of processing. </li>
*
* <li> work completed: The execution of the <code>Work</code> has been
* completed. The execution could complete with or without an exception.
* The <code>WorkManager</code> catches any exception thrown during
* <code>Work</code> processing (which includes execution context setup),
* and wraps it with a <code>WorkCompletedException</code>. </li>
* </ul>
*
* @version 1.0
* @author Ram Jeyaraman
*/
public interface WorkManager {
/**
* A constant to indicate timeout duration. A zero timeout value indicates
* an action be performed immediately.
*/
long IMMEDIATE = 0L;
/**
* A constant to indicate timeout duration. A maximum timeout value
* indicates that an action be performed arbitrarily without any time
* constraint.
*/
long INDEFINITE = Long.MAX_VALUE;
/**
* A constant to indicate an unknown start delay duration or other unknown
* values.
*/
long UNKNOWN = -1;
/**
* Accepts a <code>Work</code> instance for processing. This call
* blocks until the <code>Work</code> instance completes execution.
* There is no guarantee on when the accepted <code>Work</code>
* instance would start execution ie., there is no time constraint
* to start execution.
*
* @param work The unit of work to be done.
* Could be long or short-lived.
*
* @throws WorkRejectedException indicates that a
* <code>Work</code> instance has been rejected from further processing.
* This can occur due to internal factors.
*
* @throws WorkCompletedException indicates that a
* <code>Work</code> instance has completed execution with an exception.
*/
void doWork(Work work) // startTimeout = INDEFINITE
throws WorkException;
/**
* Accepts a <code>Work</code> instance for processing. This call
* blocks until the <code>Work</code> instance completes execution.
*
* @param work The unit of work to be done.
* Could be long or short-lived.
*
* @param startTimeout a time duration (in milliseconds)
* within which the execution of the <code>Work</code> instance must
* start. Otherwise, the <code>Work</code> instance is rejected with a
* <code>WorkRejectedException</code> set to an appropriate error code
* (<code>WorkRejectedException.TIMED_OUT</code>). Note, this
* does not offer real-time guarantees.
*
* @param execContext an object containing the execution
* context with which the submitted <code>Work</code> instance must
* be executed.
*
* @param workListener an object which would be notified
* when the various <code>Work</code> processing events (work accepted,
* work rejected, work started, work completed) occur.
*
* @throws WorkRejectedException indicates that a
* <code>Work</code> instance has been rejected from further processing.
* This can occur due to internal factors or start timeout expiration.
*
* @throws WorkCompletedException indicates that a
* <code>Work</code> instance has completed execution with an exception.
*/
void doWork(Work work, long startTimeout,
ExecutionContext execContext, WorkListener workListener)
throws WorkException;
/**
* Accepts a <code>Work</code> instance for processing. This call
* blocks until the <code>Work</code> instance starts execution
* but not until its completion. There is no guarantee on when
* the accepted <code>Work</code> instance would start
* execution ie., there is no time constraint to start execution.
*
* @param work The unit of work to be done.
* Could be long or short-lived.
*
* @return the time elapsed (in milliseconds) from <code>Work</code>
* acceptance until start of execution. Note, this does not offer
* real-time guarantees. It is valid to return -1, if the actual start
* delay duration is unknown.
*
* @throws WorkRejectedException indicates that a
* <code>Work</code> instance has been rejected from further processing.
* This can occur due to internal factors.
*/
long startWork(Work work) // startTimeout = INDEFINITE
throws WorkException;
/**
* Accepts a <code>Work</code> instance for processing. This call
* blocks until the <code>Work</code> instance starts execution
* but not until its completion. There is no guarantee on when
* the accepted <code>Work</code> instance would start
* execution ie., there is no time constraint to start execution.
*
* @param work The unit of work to be done.
* Could be long or short-lived.
*
* @param startTimeout a time duration (in milliseconds)
* within which the execution of the <code>Work</code> instance must
* start. Otherwise, the <code>Work</code> instance is rejected with a
* <code>WorkRejectedException</code> set to an appropriate error code
* (<code>WorkRejectedException.TIMED_OUT</code>). Note, this
* does not offer real-time guarantees.
*
* @param execContext an object containing the execution
* context with which the submitted <code>Work</code> instance must
* be executed.
*
* @param workListener an object which would be notified
* when the various <code>Work</code> processing events (work accepted,
* work rejected, work started, work completed) occur.
*
* @return the time elapsed (in milliseconds) from <code>Work</code>
* acceptance until start of execution. Note, this does not offer
* real-time guarantees. It is valid to return -1, if the actual start
* delay duration is unknown.
*
* @throws WorkRejectedException indicates that a
* <code>Work</code> instance has been rejected from further processing.
* This can occur due to internal factors or start timeout expiration.
*/
long startWork(Work work, long startTimeout,
ExecutionContext execContext, WorkListener workListener)
throws WorkException;
/**
* Accepts a <code>Work</code> instance for processing. This call
* does not block and returns immediately once a <code>Work</code>
* instance has been accepted for processing. There is no guarantee
* on when the submitted <code>Work</code> instance would start
* execution ie., there is no time constraint to start execution.
*
* @param work The unit of work to be done.
* Could be long or short-lived.
*
* @throws WorkRejectedException indicates that a
* <code>Work</code> instance has been rejected from further processing.
* This can occur due to internal factors.
*/
void scheduleWork(Work work) // startTimeout = INDEFINITE
throws WorkException;
/**
* Accepts a <code>Work</code> instance for processing. This call
* does not block and returns immediately once a <code>Work</code>
* instance has been accepted for processing.
*
* @param work The unit of work to be done.
* Could be long or short-lived.
*
* @param startTimeout a time duration (in milliseconds)
* within which the execution of the <code>Work</code> instance must
* start. Otherwise, the <code>Work</code> instance is rejected with a
* <code>WorkRejectedException</code> set to an appropriate error code
* (<code>WorkRejectedException.TIMED_OUT</code>). Note, this
* does not offer real-time guarantees.
*
* @param execContext an object containing the execution
* context with which the submitted <code>Work</code> instance must
* be executed.
*
* @param workListener an object which would be notified
* when the various <code>Work</code> processing events (work accepted,
* work rejected, work started, work completed) occur.
*
* @throws WorkRejectedException indicates that a
* <code>Work</code> instance has been rejected from further processing.
* This can occur due to internal factors.
*/
void scheduleWork(Work work, long startTimeout,
ExecutionContext execContext, WorkListener workListener)
throws WorkException;
}
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