add a way to avoid blocking queueHealTask() depending on caller (#16433)

cmd/admin-heal-ops.go

@@ -397,6 +397,7 @@ type healSource struct {
 	bucket    string
 	object    string
 	versionID string
+	noWait    bool             // a non blocking call, if task queue is full return right away.
 	opts      *madmin.HealOpts // optional heal option overrides default setting
 }
 
@@ -700,7 +701,6 @@ func (h *healSequence) queueHealTask(source healSource, healType madmin.HealItem
 		object:    source.object,
 		versionID: source.versionID,
 		opts:      h.settings,
-		respCh:    h.respCh,
 	}
 	if source.opts != nil {
 		task.opts = *source.opts
@@ -713,15 +713,32 @@ func (h *healSequence) queueHealTask(source healSource, healType madmin.HealItem
 	h.lastHealActivity = UTCNow()
 	h.mutex.Unlock()
 
-	select {
-	case globalBackgroundHealRoutine.tasks <- task:
-		if serverDebugLog {
-			logger.Info("Task in the queue: %#v", task)
+	if source.noWait {
+		select {
+		case globalBackgroundHealRoutine.tasks <- task:
+			if serverDebugLog {
+				logger.Info("Task in the queue: %#v", task)
+			}
+		case <-h.ctx.Done():
+			return nil
+		default:
+			// task queue is full, no more workers, we shall move on and heal later.
+			return nil
+		}
+	} else {
+		// respCh must be set for guaranteed result
+		task.respCh = h.respCh
+		select {
+		case globalBackgroundHealRoutine.tasks <- task:
+			if serverDebugLog {
+				logger.Info("Task in the queue: %#v", task)
+			}
+		case <-h.ctx.Done():
+			return nil
 		}
-	case <-h.ctx.Done():
-		return nil
 	}
 
+	// task queued, now wait for the response.
 	select {
 	case res := <-h.respCh:
 		if !h.reportProgress {

cmd/background-heal-ops.go

@@ -88,8 +88,7 @@ func (h *healRoutine) AddWorker(ctx context.Context, objAPI ObjectLayer) {
 			var err error
 			switch task.bucket {
 			case nopHeal:
-				task.respCh <- healResult{err: errSkipFile}
-				continue
+				err = errSkipFile
 			case SlashSeparator:
 				res, err = healDiskFormat(ctx, objAPI, task.opts)
 			default:
@@ -100,7 +99,10 @@ func (h *healRoutine) AddWorker(ctx context.Context, objAPI ObjectLayer) {
 				}
 			}
 
-			task.respCh <- healResult{result: res, err: err}
+			if task.respCh != nil {
+				task.respCh <- healResult{result: res, err: err}
+			}
+
 		case <-ctx.Done():
 			return
 		}

cmd/global-heal.go

@@ -449,6 +449,7 @@ func healObject(bucket, object, versionID string, scan madmin.HealScanMode) {
 			bucket:    bucket,
 			object:    object,
 			versionID: versionID,
+			noWait:    true, // do not block callers.
 			opts: &madmin.HealOpts{
 				Remove:   healDeleteDangling, // if found dangling purge it.
 				ScanMode: scan,