Add number in queue status to monitor page (#18712)

Add number in queue status to the monitor page so that administrators can
assess how much work is left to be done in the queues.

Signed-off-by: Andrew Thornton <art27@cantab.net>

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

modules/queue/manager.go

@@ -84,6 +84,8 @@ type ManagedPool interface {
 	BoostWorkers() int
 	// SetPoolSettings sets the user updatable settings for the pool
 	SetPoolSettings(maxNumberOfWorkers, boostWorkers int, timeout time.Duration)
+	// NumberInQueue returns the total number of items in the pool
+	NumberInQueue() int64
 	// Done returns a channel that will be closed when the Pool's baseCtx is closed
 	Done() <-chan struct{}
 }
@@ -427,6 +429,14 @@ func (q *ManagedQueue) SetPoolSettings(maxNumberOfWorkers, boostWorkers int, tim
 	}
 }
 
+// NumberInQueue returns the number of items in the queue
+func (q *ManagedQueue) NumberInQueue() int64 {
+	if pool, ok := q.Managed.(ManagedPool); ok {
+		return pool.NumberInQueue()
+	}
+	return -1
+}
+
 func (l ManagedQueueList) Len() int {
 	return len(l)
 }

modules/queue/queue_bytefifo.go

@@ -135,6 +135,13 @@ func (q *ByteFIFOQueue) IsEmpty() bool {
 	return q.byteFIFO.Len(q.terminateCtx) == 0
 }
 
+// NumberInQueue returns the number in the queue
+func (q *ByteFIFOQueue) NumberInQueue() int64 {
+	q.lock.Lock()
+	defer q.lock.Unlock()
+	return q.byteFIFO.Len(q.terminateCtx) + q.WorkerPool.NumberInQueue()
+}
+
 // Flush flushes the ByteFIFOQueue
 func (q *ByteFIFOQueue) Flush(timeout time.Duration) error {
 	select {

modules/queue/workerpool.go

@@ -204,6 +204,11 @@ func (p *WorkerPool) NumberOfWorkers() int {
 	return p.numberOfWorkers
 }
 
+// NumberInQueue returns the number of items in the queue
+func (p *WorkerPool) NumberInQueue() int64 {
+	return atomic.LoadInt64(&p.numInQueue)
+}
+
 // MaxNumberOfWorkers returns the maximum number of workers automatically added to the pool
 func (p *WorkerPool) MaxNumberOfWorkers() int {
 	p.lock.Lock()