[#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/process.go

@@ -0,0 +1,95 @@
+package replicator
+
+import (
+	"context"
+
+	"github.com/nspcc-dev/neofs-node/pkg/network"
+	putsvc "github.com/nspcc-dev/neofs-node/pkg/services/object/put"
+	"go.uber.org/zap"
+)
+
+func (p *Replicator) Run(ctx context.Context) {
+	defer func() {
+		close(p.ch)
+		p.log.Info("routine stopped")
+	}()
+
+	p.ch = make(chan *Task, p.taskCap)
+
+	p.log.Info("process routine",
+		zap.Uint32("task queue capacity", p.taskCap),
+		zap.Duration("put timeout", p.putTimeout),
+	)
+
+	for {
+		select {
+		case <-ctx.Done():
+			p.log.Warn("context is done",
+				zap.String("error", ctx.Err().Error()),
+			)
+
+			return
+		case task, ok := <-p.ch:
+			if !ok {
+				p.log.Warn("trigger channel is closed")
+
+				return
+			}
+
+			p.handleTask(ctx, task)
+		}
+	}
+}
+
+func (p *Replicator) handleTask(ctx context.Context, task *Task) {
+	defer func() {
+		p.log.Info("finish work",
+			zap.Uint32("amount of unfinished replicas", task.quantity),
+		)
+	}()
+
+	obj, err := p.localStorage.Get(task.addr)
+	if err != nil {
+		p.log.Error("could not get object from local storage")
+
+		return
+	}
+
+	prm := new(putsvc.RemotePutPrm).
+		WithObject(obj)
+
+	for i := 0; task.quantity > 0 && i < len(task.nodes); i++ {
+		select {
+		case <-ctx.Done():
+			return
+		default:
+		}
+
+		netAddr := task.nodes[i].NetworkAddress()
+
+		log := p.log.With(zap.String("node", netAddr))
+
+		node, err := network.AddressFromString(netAddr)
+		if err != nil {
+			log.Error("could not parse network address")
+
+			continue
+		}
+
+		callCtx, cancel := context.WithTimeout(ctx, p.putTimeout)
+
+		err = p.remoteSender.PutObject(callCtx, prm.WithNodeAddress(node))
+
+		cancel()
+
+		if err != nil {
+			log.Error("could not replicate object",
+				zap.String("error", err.Error()),
+			)
+		} else {
+			log.Info("object successfully replicated")
+
+			task.quantity--
+		}
+	}
+}