[#217] policer: Handler redundant local copy of the object

Detect redundant local copy of the object in Object Policer. Add redundant
copy callback (`WithRedundantCopyCallback` option). Pass address of the
redundant copy to callback.

Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>

pkg/services/policer/check.go

@@ -48,8 +48,9 @@ func (p *Policer) processObject(ctx context.Context, addr *object.Address) {
 
 func (p *Policer) processNodes(ctx context.Context, addr *object.Address, nodes netmap.Nodes, shortage uint32) {
 	prm := new(headsvc.RemoteHeadPrm).WithObjectAddress(addr)
+	redundantLocalCopy := false
 
-	for i := 0; shortage > 0 && i < len(nodes); i++ {
+	for i := 0; i < len(nodes); i++ {
 		select {
 		case <-ctx.Done():
 			return
@@ -68,8 +69,13 @@ func (p *Policer) processNodes(ctx context.Context, addr *object.Address, nodes
 		}
 
 		if network.IsLocalAddress(p.localAddrSrc, node) {
-			shortage--
+			if shortage == 0 {
+				redundantLocalCopy = true
+				break
 			} else {
+				shortage--
+			}
+		} else if shortage > 0 {
 			callCtx, cancel := context.WithTimeout(ctx, p.headTimeout)
 
 			_, err = p.remoteHeader.Head(callCtx, prm.WithNodeAddress(node))
@@ -107,5 +113,7 @@ func (p *Policer) processNodes(ctx context.Context, addr *object.Address, nodes
 			WithNodes(nodes).
 			WithCopiesNumber(shortage),
 		)
+	} else if redundantLocalCopy {
+		p.cbRedundantCopy(addr)
 	}
 }

pkg/services/policer/policer.go

@@ -4,6 +4,7 @@ import (
 	"sync"
 	"time"
 
+	"github.com/nspcc-dev/neofs-api-go/pkg/object"
 	"github.com/nspcc-dev/neofs-node/pkg/core/container"
 	"github.com/nspcc-dev/neofs-node/pkg/local_object_storage/engine"
 	"github.com/nspcc-dev/neofs-node/pkg/network"
@@ -25,6 +26,10 @@ type Policer struct {
 // Option is an option for Policer constructor.
 type Option func(*cfg)
 
+// RedundantCopyCallback is a callback to pass
+// the redundant local copy of the object.
+type RedundantCopyCallback func(*object.Address)
+
 type cfg struct {
 	headTimeout time.Duration
 
@@ -45,6 +50,8 @@ type cfg struct {
 	localAddrSrc network.LocalAddressSource
 
 	replicator *replicator.Replicator
+
+	cbRedundantCopy RedundantCopyCallback
 }
 
 func defaultCfg() *cfg {
@@ -148,3 +155,12 @@ func WithReplicator(v *replicator.Replicator) Option {
 		c.replicator = v
 	}
 }
+
+// WithRedundantCopyCallback returns option to set
+// callback to pass redundant local object copies
+// detected by Policer.
+func WithRedundantCopyCallback(cb RedundantCopyCallback) Option {
+	return func(c *cfg) {
+		c.cbRedundantCopy = cb
+	}
+}