com.tomtom.speedtools.thread

Class WorkQueue

java.lang.Object

com.tomtom.speedtools.thread.WorkQueue

public class WorkQueue
extends Object

This class creates a pool of worker threads that will execute workload tasks. The amount of actual threads is limited, as well as the workload queue. To use this class, you should create a WorkQueue with a maximum number of work packages for the work queue. Some of the worker threads are started (and stand-by) immediately after creating the WorkQueue. After that, you can add workload (which is really an instance of a Runnable) to the work queue by using startOrWait(workLoad). This call will add the workload if the queue is not filled up yet, or wait until there is room to add the workload. You can use waitUntilFinished() to wait until the entire workload queue is processed (and all worker threads are done processing). Or you can check whether processing is done with isEmptyAndFinished(). If worker threads throw exceptions, these are caught and stored in a list which can be retrieved by getRuntimeExceptions(). The worker thread that processed workload throwing such an exception is simply returned to the thread pool ready to process the next piece of workload. To shutdown all the worker threads, use scheduleShutdown(). This will schedule a shutdown of all worker threads after they have finished processing their workload. After this call, the only valid calls left is getRuntimeExceptions(). Important: This class itself is NOT thread safe: only 1 thread should feed one particular instance of WorkQueue at a time.

Constructor Summary

Constructors

Constructor and Description
WorkQueue(int maxQueueSize) Create a work queue with a maximum number of worker threads and a maximum workload queue size.

Method Summary

Modifier and Type	Method and Description
void	addException(Exception exception) Add a specific exception to the work queue.
List<Exception>	getExceptions() Return any runtime exception that occurred in the threads.
boolean	isEmptyAndFinished() Check if there is workload available, or a thread is processing workload still.
void	scheduleShutdown() Schedule shutdown for all threads after they finished their work.
void	startOrWait(Runnable workLoad) Start workload, or wait if there is too much workload in the queue.
void	startOrWait(Runnable workLoad, long timeout) Start workload, or wait if there is too much workload in the queue.
boolean	waitUntilFinished() Wait until the work pool finished executing all work load.
boolean	waitUntilFinished(long timeout) Wait until the work pool finished executing all work load.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

WorkQueue

public WorkQueue(int maxQueueSize)

Create a work queue with a maximum number of worker threads and a maximum workload queue size. Adding workload past the workload queue size will block until the queue is small enough to add more workload. The caller should call shutdown() to shut down the threads after they have carried out their workloads.

Parameters:

maxQueueSize - Maximum work load queue size.

Method Detail

scheduleShutdown

public void scheduleShutdown()

Schedule shutdown for all threads after they finished their work. After this call, no other calls to this class should be made!

startOrWait

public void startOrWait(@Nonnull
                        Runnable workLoad,
                        long timeout)

Start workload, or wait if there is too much workload in the queue.

Parameters:

workLoad - Workload to be started.

timeout - Timeout in millis. If there is no room left in the queue before this timeout expires, the workload is discarded and not scheduled. Use 0 for wait 'forever'.

startOrWait

public void startOrWait(@Nonnull
                        Runnable workLoad)

Start workload, or wait if there is too much workload in the queue.

Parameters:

workLoad - Workload to be started.

waitUntilFinished

public boolean waitUntilFinished(long timeout)

Wait until the work pool finished executing all work load.

Parameters:

timeout - Max. wait time in msecs. Use 0 for 'forever'.

Returns:

False if exceptions were caught during executing workload packages.

waitUntilFinished

public boolean waitUntilFinished()

Wait until the work pool finished executing all work load.

Returns:

False if exceptions were caught during executing workload packages.

isEmptyAndFinished

public boolean isEmptyAndFinished()

Check if there is workload available, or a thread is processing workload still.

Returns:

Workload is available, or a thread is busy processing last workload.

addException

public void addException(@Nonnull
                         Exception exception)

Add a specific exception to the work queue. This method may come in handy in the run() method of workload, to communicate specific exceptions to the WorkQueue during execution.

Parameters:

exception - Exception to be added.

getExceptions

@Nonnull
public List<Exception> getExceptions()

Return any runtime exception that occurred in the threads. This method should only be called from the feeder thread.

Returns:

List of exceptions.