Restart zero worker if there is still work to do (go-gitea#18658)

Backport go-gitea#18658

It is possible for the zero worker to timeout before all the work is finished.
This may mean that work may take a long time to complete because a worker will only
be induced on repushing.

Also ensure that requested count is reset after pulls and push mirror sync requests and add some more trace logging to the queue push.

Fix go-gitea#18607

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

Author: zeripath

modules/queue/workerpool.go

@@ -87,6 +87,20 @@ func (p *WorkerPool) Push(data Data) {
 	}
 }
 
+// HasNoWorkerScaling will return true if the queue has no workers, and has no worker boosting
+func (p *WorkerPool) HasNoWorkerScaling() bool {
+	p.lock.Lock()
+	defer p.lock.Unlock()
+	return p.hasNoWorkerScaling()
+}
+
+func (p *WorkerPool) hasNoWorkerScaling() bool {
+	return p.numberOfWorkers == 0 && (p.boostTimeout == 0 || p.boostWorkers == 0 || p.maxNumberOfWorkers == 0)
+}
+
+// zeroBoost will add a temporary boost worker for a no worker queue
+// p.lock must be locked at the start of this function BUT it will be unlocked by the end of this function
+// (This is because addWorkers has to be called whilst unlocked)
 func (p *WorkerPool) zeroBoost() {
 	ctx, cancel := context.WithTimeout(p.baseCtx, p.boostTimeout)
 	mq := GetManager().GetManagedQueue(p.qid)
@@ -277,6 +291,22 @@ func (p *WorkerPool) addWorkers(ctx context.Context, cancel context.CancelFunc,
 				p.cond.Broadcast()
 				cancel()
 			}
+
+			select {
+			case <-p.baseCtx.Done():
+				// Don't warn if the baseCtx is shutdown
+			default:
+				if p.hasNoWorkerScaling() {
+					log.Warn(
+						"Queue: %d is configured to be non-scaling and has no workers - this configuration is likely incorrect.\n"+
+							"The queue will be paused to prevent data-loss with the assumption that you will add workers and unpause as required.", p.qid)
+				} else if p.numberOfWorkers == 0 && atomic.LoadInt64(&p.numInQueue) > 0 {
+					// OK there are no workers but... there's still work to be done -> Reboost
+					p.zeroBoost()
+					// p.lock will be unlocked by zeroBoost
+					return
+				}
+			}
 			p.lock.Unlock()
 		}()
 	}

services/mirror/mirror.go

@@ -59,11 +59,13 @@ func Update(ctx context.Context, pullLimit, pushLimit int) error {
 
 	handler := func(idx int, bean interface{}, limit int) error {
 		var item SyncRequest
+		var repo *repo_model.Repository
 		if m, ok := bean.(*repo_model.Mirror); ok {
 			if m.Repo == nil {
 				log.Error("Disconnected mirror found: %d", m.ID)
 				return nil
 			}
+			repo = m.Repo
 			item = SyncRequest{
 				Type:   PullMirrorType,
 				RepoID: m.RepoID,
@@ -73,6 +75,7 @@ func Update(ctx context.Context, pullLimit, pushLimit int) error {
 				log.Error("Disconnected push-mirror found: %d", m.ID)
 				return nil
 			}
+			repo = m.Repo
 			item = SyncRequest{
 				Type:   PushMirrorType,
 				RepoID: m.RepoID,
@@ -89,17 +92,16 @@ func Update(ctx context.Context, pullLimit, pushLimit int) error {
 		default:
 		}
 
-		// Check if this request is already in the queue
-		has, err := mirrorQueue.Has(&item)
-		if err != nil {
-			return err
-		}
-		if has {
-			return nil
-		}
-
 		// Push to the Queue
 		if err := mirrorQueue.Push(&item); err != nil {
+			if err == queue.ErrAlreadyInQueue {
+				if item.Type == PushMirrorType {
+					log.Trace("PushMirrors for %-v already queued for sync", repo)
+				} else {
+					log.Trace("PullMirrors for %-v already queued for sync", repo)
+				}
+				return nil
+			}
 			return err
 		}
 
@@ -110,23 +112,29 @@ func Update(ctx context.Context, pullLimit, pushLimit int) error {
 		return nil
 	}
 
+	pullMirrorsRequested := 0
 	if pullLimit != 0 {
+		requested = 0
 		if err := repo_model.MirrorsIterate(func(idx int, bean interface{}) error {
 			return handler(idx, bean, pullLimit)
 		}); err != nil && err != errLimit {
 			log.Error("MirrorsIterate: %v", err)
 			return err
 		}
+		pullMirrorsRequested, requested = requested, 0
 	}
+	pushMirrorsRequested := 0
 	if pushLimit != 0 {
+		requested = 0
 		if err := repo_model.PushMirrorsIterate(func(idx int, bean interface{}) error {
 			return handler(idx, bean, pushLimit)
 		}); err != nil && err != errLimit {
 			log.Error("PushMirrorsIterate: %v", err)
 			return err
 		}
+		pushMirrorsRequested, requested = requested, 0
 	}
-	log.Trace("Finished: Update")
+	log.Trace("Finished: Update: %d pull mirrors and %d push mirrors queued", pullMirrorsRequested, pushMirrorsRequested)
 	return nil
 }