[#188] engine: Refactor get range from engine

Resolve funlen linter for StorageEngine.getRange method

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

pkg/local_object_storage/engine/range.go

@@ -65,122 +65,51 @@ func (e *StorageEngine) GetRange(prm RngPrm) (res RngRes, err error) {
 	return
 }
 
-// nolint: funlen
 func (e *StorageEngine) getRange(prm RngPrm) (RngRes, error) {
 	if e.metrics != nil {
 		defer elapsed(e.metrics.AddRangeDuration)()
 	}
 
-	var (
+	var errNotFound apistatus.ObjectNotFound
-		obj   *objectSDK.Object
-		siErr *objectSDK.SplitInfoError
-
-		errNotFound apistatus.ObjectNotFound
-
-		outSI    *objectSDK.SplitInfo
-		outError error = errNotFound
-
-		shardWithMeta hashedShard
-		metaError     error
-	)
-
-	var hasDegraded bool
 
 	var shPrm shard.RngPrm
 	shPrm.SetAddress(prm.addr)
 	shPrm.SetRange(prm.off, prm.ln)
 
-	e.iterateOverSortedShards(prm.addr, func(_ int, sh hashedShard) (stop bool) {
+	it := &getRangeShardIterator{
-		noMeta := sh.GetMode().NoMetabase()
+		OutError: errNotFound,
-		hasDegraded = hasDegraded || noMeta
+		ShardPrm: shPrm,
-		shPrm.SetIgnoreMeta(noMeta)
+		Address:  prm.addr,
-
+		Engine:   e,
-		res, err := sh.GetRange(shPrm)
-		if err != nil {
-			if res.HasMeta() {
-				shardWithMeta = sh
-				metaError = err
-			}
-			switch {
-			case shard.IsErrNotFound(err):
-				return false // ignore, go to next shard
-			case errors.As(err, &siErr):
-				if outSI == nil {
-					outSI = objectSDK.NewSplitInfo()
-				}
-
-				util.MergeSplitInfo(siErr.SplitInfo(), outSI)
-
-				_, withLink := outSI.Link()
-				_, withLast := outSI.LastPart()
-
-				// stop iterating over shards if SplitInfo structure is complete
-				if withLink && withLast {
-					return true
-				}
-
-				return false
-			case
-				shard.IsErrRemoved(err),
-				shard.IsErrOutOfRange(err):
-				outError = err
-
-				return true // stop, return it back
-			default:
-				e.reportShardError(sh, "could not get object from shard", err)
-				return false
-			}
-		}
-
-		obj = res.Object()
-
-		return true
-	})
-
-	if outSI != nil {
-		return RngRes{}, logicerr.Wrap(objectSDK.NewSplitInfoError(outSI))
 	}
 
-	if obj == nil {
+	it.tryGetWithMeta()
+
+	if it.SplitInfo != nil {
+		return RngRes{}, logicerr.Wrap(objectSDK.NewSplitInfoError(it.SplitInfo))
+	}
+
+	if it.Object == nil {
 		// If any shard is in a degraded mode, we should assume that metabase could store
 		// info about some object.
-		if shardWithMeta.Shard == nil && !hasDegraded || !shard.IsErrNotFound(outError) {
+		if it.ShardWithMeta.Shard == nil && !it.HasDegraded || !shard.IsErrNotFound(it.OutError) {
-			return RngRes{}, outError
+			return RngRes{}, it.OutError
 		}
 
-		// If the object is not found but is present in metabase,
+		it.tryGetFromBlobstor()
-		// try to fetch it from blobstor directly. If it is found in any
-		// blobstor, increase the error counter for the shard which contains the meta.
-		shPrm.SetIgnoreMeta(true)
 
-		e.iterateOverSortedShards(prm.addr, func(_ int, sh hashedShard) (stop bool) {
+		if it.Object == nil {
-			if sh.GetMode().NoMetabase() {
+			return RngRes{}, it.OutError
-				// Already processed it without a metabase.
-				return false
-			}
-
-			res, err := sh.GetRange(shPrm)
-			if shard.IsErrOutOfRange(err) {
-				var errOutOfRange apistatus.ObjectOutOfRange
-
-				outError = errOutOfRange
-				return true
-			}
-			obj = res.Object()
-			return err == nil
-		})
-		if obj == nil {
-			return RngRes{}, outError
 		}
-		if shardWithMeta.Shard != nil {
+		if it.ShardWithMeta.Shard != nil {
-			e.reportShardError(shardWithMeta, "meta info was present, but object is missing",
+			e.reportShardError(it.ShardWithMeta, "meta info was present, but object is missing",
-				metaError,
+				it.MetaError,
 				zap.Stringer("address", prm.addr))
 		}
 	}
 
 	return RngRes{
-		obj: obj,
+		obj: it.Object,
 	}, nil
 }
 
@@ -197,3 +126,85 @@ func GetRange(storage *StorageEngine, addr oid.Address, rng *objectSDK.Range) ([
 
 	return res.Object().Payload(), nil
 }
+
+type getRangeShardIterator struct {
+	Object         *objectSDK.Object
+	SplitInfoError *objectSDK.SplitInfoError
+	SplitInfo      *objectSDK.SplitInfo
+	OutError       error
+	ShardWithMeta  hashedShard
+	MetaError      error
+	HasDegraded    bool
+
+	ShardPrm shard.RngPrm
+	Address  oid.Address
+	Engine   *StorageEngine
+}
+
+func (i *getRangeShardIterator) tryGetWithMeta() {
+	i.Engine.iterateOverSortedShards(i.Address, func(_ int, sh hashedShard) (stop bool) {
+		noMeta := sh.GetMode().NoMetabase()
+		i.HasDegraded = i.HasDegraded || noMeta
+		i.ShardPrm.SetIgnoreMeta(noMeta)
+
+		res, err := sh.GetRange(i.ShardPrm)
+		if err == nil {
+			i.Object = res.Object()
+			return true
+		}
+
+		if res.HasMeta() {
+			i.ShardWithMeta = sh
+			i.MetaError = err
+		}
+		switch {
+		case shard.IsErrNotFound(err):
+			return false // ignore, go to next shard
+		case errors.As(err, &i.SplitInfoError):
+			if i.SplitInfo == nil {
+				i.SplitInfo = objectSDK.NewSplitInfo()
+			}
+
+			util.MergeSplitInfo(i.SplitInfoError.SplitInfo(), i.SplitInfo)
+
+			_, withLink := i.SplitInfo.Link()
+			_, withLast := i.SplitInfo.LastPart()
+
+			// stop iterating over shards if SplitInfo structure is complete
+			return withLink && withLast
+		case
+			shard.IsErrRemoved(err),
+			shard.IsErrOutOfRange(err):
+			i.OutError = err
+
+			return true // stop, return it back
+		default:
+			i.Engine.reportShardError(sh, "could not get object from shard", err)
+			return false
+		}
+	})
+}
+
+func (i *getRangeShardIterator) tryGetFromBlobstor() {
+	// If the object is not found but is present in metabase,
+	// try to fetch it from blobstor directly. If it is found in any
+	// blobstor, increase the error counter for the shard which contains the meta.
+	i.ShardPrm.SetIgnoreMeta(true)
+
+	i.Engine.iterateOverSortedShards(i.Address, func(_ int, sh hashedShard) (stop bool) {
+		if sh.GetMode().NoMetabase() {
+			// Already processed it without a metabase.
+			return false
+		}
+
+		res, err := sh.GetRange(i.ShardPrm)
+		if shard.IsErrOutOfRange(err) {
+			var errOutOfRange apistatus.ObjectOutOfRange
+
+			i.OutError = errOutOfRange
+			return true
+		}
+		i.Object = res.Object()
+		return err == nil
+	})
+}