ThreadWeaver 5.109.0
Classes | Public Member Functions | Static Public Member Functions | List of all members
ThreadWeaver::Queue

Queue implements a ThreadWeaver job queue. More...

#include <queue.h>

Classes

struct  GlobalQueueFactory
 Interface for the global queue factory. More...
 

Public Member Functions

 Queue (QObject *parent=nullptr)
 
 Queue (QueueSignals *implementation, QObject *parent=nullptr)
 Construct a queue with a customized implementation The queue takes ownership and will delete the implementation upon destruction.
 
int currentNumberOfThreads () const override
 Returns the current number of threads in the inventory.
 
void dequeue () override
 Remove all queued jobs.
 
bool dequeue (const JobPointer &) override
 Remove a job from the queue.
 
void enqueue (const JobPointer &job)
 
void enqueue (const QVector< JobPointer > &jobs) override
 Queue a vector of jobs.
 
void finish () override
 Finish all queued operations, then return.
 
bool isEmpty () const override
 Is the queue empty? The queue is empty if no more jobs are queued.
 
bool isIdle () const override
 Is the weaver idle? The weaver is idle if no jobs are queued and no jobs are processed by the threads.
 
int maximumNumberOfThreads () const override
 Get the maximum number of threads this Weaver may start.
 
int queueLength () const override
 Returns the number of pending jobs.
 
void requestAbort () override
 Request aborts of the currently executed jobs.
 
void reschedule () override
 Reschedule the jobs in the queue.
 
void resume () override
 Resume job queueing.
 
void setMaximumNumberOfThreads (int cap) override
 Set the maximum number of threads this Weaver object may start.
 
void shutDown () override
 Shut down the queue.
 
const Statestate () const override
 Return the state of the weaver object.
 
QueueStream stream ()
 
void suspend () override
 Suspend job execution.
 
- Public Member Functions inherited from ThreadWeaver::QueueSignals
 QueueSignals (QObject *parent=nullptr)
 
 QueueSignals (ThreadWeaver::Private::QueueSignals_Private *d, QObject *parent=nullptr)
 
virtual int currentNumberOfThreads () const =0
 Returns the current number of threads in the inventory.
 
virtual void dequeue ()=0
 Remove all queued jobs.
 
virtual bool dequeue (const JobPointer &job)=0
 Remove a job from the queue.
 
virtual void enqueue (const QVector< JobPointer > &jobs)=0
 Queue a vector of jobs.
 
virtual void finish ()=0
 Finish all queued operations, then return.
 
virtual bool isEmpty () const =0
 Is the queue empty? The queue is empty if no more jobs are queued.
 
virtual bool isIdle () const =0
 Is the weaver idle? The weaver is idle if no jobs are queued and no jobs are processed by the threads.
 
virtual int maximumNumberOfThreads () const =0
 Get the maximum number of threads this Weaver may start.
 
virtual int queueLength () const =0
 Returns the number of pending jobs.
 
virtual void requestAbort ()=0
 Request aborts of the currently executed jobs.
 
virtual void reschedule ()=0
 Reschedule the jobs in the queue.
 
virtual void resume ()=0
 Resume job queueing.
 
virtual void setMaximumNumberOfThreads (int cap)=0
 Set the maximum number of threads this Weaver object may start.
 
virtual void shutDown ()=0
 Shut down the queue.
 
virtual const Statestate () const =0
 Return the state of the weaver object.
 
virtual void suspend ()=0
 Suspend job execution.
 

Static Public Member Functions

static ThreadWeaver::Queueinstance ()
 
static void setGlobalQueueFactory (GlobalQueueFactory *factory)
 

Additional Inherited Members

- Signals inherited from ThreadWeaver::QueueSignals
void finished ()
 Emitted when the Queue has completed all jobs currently queued.
 
void stateChanged (ThreadWeaver::State *)
 Emitted when the processing state of the Queue has changed.
 
void suspended ()
 The Queue has been suspended.
 
- Protected Member Functions inherited from ThreadWeaver::QueueSignals
ThreadWeaver::Private::QueueSignals_Private * d ()
 
const ThreadWeaver::Private::QueueSignals_Private * d () const
 

Detailed Description

Queue implements a ThreadWeaver job queue.

Queues process jobs enqueued in them by automatically assigning them to worker threads they manage. Applications using ThreadWeaver can make use of a global Queue which is instantiated on demand, or create multiple queues as needed. A job assigned to a queue will be processed by that specific queue.

Worker threads are created by the queues as needed. To create a customized global queue, see GlobalQueueFactory.

See also
GlobalQueueFactory
Queue::enqueue()
Queue::instance()

Constructor & Destructor Documentation

◆ Queue()

ThreadWeaver::Queue::Queue ( QueueSignals implementation,
QObject *  parent = nullptr 
)
explicit

Construct a queue with a customized implementation The queue takes ownership and will delete the implementation upon destruction.

Member Function Documentation

◆ currentNumberOfThreads()

int ThreadWeaver::Queue::currentNumberOfThreads ( ) const
overridevirtual

Returns the current number of threads in the inventory.

Implements ThreadWeaver::QueueInterface.

◆ dequeue() [1/2]

void ThreadWeaver::Queue::dequeue ( )
overridevirtual

Remove all queued jobs.

All waiting jobs will be dequeued. The semantics are the same as for dequeue(JobInterface).

See also
dequeue(JobInterface)

Implements ThreadWeaver::QueueInterface.

◆ dequeue() [2/2]

bool ThreadWeaver::Queue::dequeue ( const JobPointer &  job)
overridevirtual

Remove a job from the queue.

If the job was queued but not started so far, it is removed from the queue.

You can always call dequeue, it will return true if the job was dequeued. However if the job is not in the queue anymore, it is already being executed, it is too late to dequeue, and dequeue will return false. The return value is thread-safe - if true is returned, the job was still waiting, and has been dequeued. If not, the job was not waiting in the queue.

Modifying queued jobs is best done on a suspended queue. Often, for example at the end of an application, it is sufficient to dequeue all jobs (which leaves only the ones mid-air in threads), call finish (that will wait for all the mid air jobs to complete), and then exit. Without dequeue(), all jobs in the queue would be executed during finish().

See also
requestAbort for aborting jobs during execution
Returns
true if the job was waiting and has been dequeued
false if the job was not found waiting in the queue

Implements ThreadWeaver::QueueInterface.

◆ enqueue()

void ThreadWeaver::Queue::enqueue ( const QVector< JobPointer > &  jobs)
overridevirtual

Queue a vector of jobs.

It depends on the state if execution of the job will be attempted immediately. In suspended state, jobs can be added to the queue, but the threads remain suspended. In WorkongHard state, an idle thread may immediately execute the job, or it might be queued if all threads are busy.

JobPointer is a shared pointer. This means the object pointed to will be deleted if this object is the last remaining reference to it. Keep a JobPointer to the job to avoid automatic deletion.

Implements ThreadWeaver::QueueInterface.

◆ finish()

void ThreadWeaver::Queue::finish ( )
overridevirtual

Finish all queued operations, then return.

This method is used in imperative (not event driven) programs that cannot react on events to have the controlling (main) thread wait wait for the jobs to finish. The call will block the calling thread and return when all queued jobs have been processed.

Warning: This will suspend your thread! Warning: If one of your jobs enters an infinite loop, this will never return!

Implements ThreadWeaver::QueueInterface.

◆ isEmpty()

bool ThreadWeaver::Queue::isEmpty ( ) const
overridevirtual

Is the queue empty? The queue is empty if no more jobs are queued.

Implements ThreadWeaver::QueueInterface.

◆ isIdle()

bool ThreadWeaver::Queue::isIdle ( ) const
overridevirtual

Is the weaver idle? The weaver is idle if no jobs are queued and no jobs are processed by the threads.

Implements ThreadWeaver::QueueInterface.

◆ maximumNumberOfThreads()

int ThreadWeaver::Queue::maximumNumberOfThreads ( ) const
overridevirtual

Get the maximum number of threads this Weaver may start.

Implements ThreadWeaver::QueueInterface.

◆ queueLength()

int ThreadWeaver::Queue::queueLength ( ) const
overridevirtual

Returns the number of pending jobs.

This will return the number of queued jobs. Jobs that are currently being executed are not part of the queue. All jobs in the queue are waiting to be executed.

Implements ThreadWeaver::QueueInterface.

◆ requestAbort()

void ThreadWeaver::Queue::requestAbort ( )
overridevirtual

Request aborts of the currently executed jobs.

It is important to understand that aborts are requested, but cannot be guaranteed, as not all Job classes support it. It is up to the application to decide if and how job aborts are necessary.

Implements ThreadWeaver::QueueInterface.

◆ reschedule()

void ThreadWeaver::Queue::reschedule ( )
overridevirtual

Reschedule the jobs in the queue.

This method triggers a scheduling attempt to perform jobs. It will schedule enqueued jobs to be executed by idle threads. It should only be necessary to call it if the canRun() status of a job changed spontaneously due to external reasons.

Implements ThreadWeaver::QueueInterface.

◆ resume()

void ThreadWeaver::Queue::resume ( )
overridevirtual

Resume job queueing.

See also
suspend

Implements ThreadWeaver::QueueInterface.

◆ setMaximumNumberOfThreads()

void ThreadWeaver::Queue::setMaximumNumberOfThreads ( int  cap)
overridevirtual

Set the maximum number of threads this Weaver object may start.

Implements ThreadWeaver::QueueInterface.

◆ shutDown()

void ThreadWeaver::Queue::shutDown ( )
overridevirtual

Shut down the queue.

Tells all threads to exit, and changes to Destructed state. It is safe to destroy the queue once this method returns.

Implements ThreadWeaver::QueueInterface.

◆ state()

const State * ThreadWeaver::Queue::state ( ) const
overridevirtual

Return the state of the weaver object.

Implements ThreadWeaver::QueueInterface.

◆ suspend()

void ThreadWeaver::Queue::suspend ( )
overridevirtual

Suspend job execution.

When suspending, all threads are allowed to finish the currently assigned job but will not receive a new assignment. When all threads are done processing the assigned job, the signal suspended will() be emitted. If you call suspend() and there are no jobs left to be done, you will immediately receive the suspended() signal.

Implements ThreadWeaver::QueueInterface.