[#661] blobovniczatree: Make Rebuild concurrent

Different DBs can be rebuild concurrently.

Signed-off-by: Dmitrii Stepanov <d.stepanov@yadro.com>

pkg/local_object_storage/engine/engine.go

@@ -38,6 +38,7 @@ type StorageEngine struct {
 		err error
 	}
 	evacuateLimiter *evacuationLimiter
+	rebuildLimiter  *rebuildLimiter
 }
 
 type shardWrapper struct {
@@ -215,13 +216,15 @@ type cfg struct {
 	shardPoolSize uint32
 
 	lowMem bool
+
+	rebuildWorkersCount uint32
 }
 
 func defaultCfg() *cfg {
 	return &cfg{
-		log: &logger.Logger{Logger: zap.L()},
-
-		shardPoolSize: 20,
+		log:                 &logger.Logger{Logger: zap.L()},
+		shardPoolSize:       20,
+		rebuildWorkersCount: 100,
 	}
 }
 
@@ -240,6 +243,7 @@ func New(opts ...Option) *StorageEngine {
 		closeCh:         make(chan struct{}),
 		setModeCh:       make(chan setModeRequest),
 		evacuateLimiter: &evacuationLimiter{},
+		rebuildLimiter:  newRebuildLimiter(c.rebuildWorkersCount),
 	}
 }
 
@@ -277,3 +281,10 @@ func WithLowMemoryConsumption(lowMemCons bool) Option {
 		c.lowMem = lowMemCons
 	}
 }
+
+// WithRebuildWorkersCount returns an option to set the count of concurrent rebuild workers.
+func WithRebuildWorkersCount(count uint32) Option {
+	return func(c *cfg) {
+		c.rebuildWorkersCount = count
+	}
+}