[#109] services: Implement Replicator service

Implement Replicator service that performs background work to replicate
local object to remote nodes in the container. Replicator is going to be
used by Policer.

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

pkg/services/replicator/replicator.go

@@ -0,0 +1,80 @@
+package replicator
+
+import (
+	"time"
+
+	"github.com/nspcc-dev/neofs-node/pkg/local_object_storage/localstore"
+	putsvc "github.com/nspcc-dev/neofs-node/pkg/services/object/put"
+	"github.com/nspcc-dev/neofs-node/pkg/util/logger"
+	"go.uber.org/zap"
+)
+
+// Replicator represents the utility that replicates
+// local objects to remote nodes.
+type Replicator struct {
+	*cfg
+
+	ch chan *Task
+}
+
+// Option is an option for Policer constructor.
+type Option func(*cfg)
+
+type cfg struct {
+	taskCap uint32
+
+	putTimeout time.Duration
+
+	log *logger.Logger
+
+	remoteSender *putsvc.RemoteSender
+
+	localStorage *localstore.Storage
+}
+
+func defaultCfg() *cfg {
+	return &cfg{}
+}
+
+// New creates, initializes and returns Replicator instance.
+func New(opts ...Option) *Replicator {
+	c := defaultCfg()
+
+	for i := range opts {
+		opts[i](c)
+	}
+
+	c.log = c.log.With(zap.String("component", "Object Replicator"))
+
+	return &Replicator{
+		cfg: c,
+	}
+}
+
+// WithPutTimeout returns option to set Put timeout of Replicator.
+func WithPutTimeout(v time.Duration) Option {
+	return func(c *cfg) {
+		c.putTimeout = v
+	}
+}
+
+// WithLogger returns option to set Logger of Replicator.
+func WithLogger(v *logger.Logger) Option {
+	return func(c *cfg) {
+		c.log = v
+	}
+}
+
+// WithRemoteSender returns option to set remote object sender of Replicator.
+func WithRemoteSender(v *putsvc.RemoteSender) Option {
+	return func(c *cfg) {
+		c.remoteSender = v
+	}
+}
+
+// WithLocalStorage returns option to set local object storage of Replicator.
+func WithLocalStorage(v *localstore.Storage) Option {
+	return func(c *cfg) {
+		c.localStorage = v
+	}
+}