[#112] Add cache to ListObjects and layer

Signed-off-by: Angira Kekteeva <kira@nspcc.ru>

api/layer/layer.go

@@ -24,6 +24,7 @@ type (
 	layer struct {
 		pool  pool.Pool
 		log   *zap.Logger
+		cache ObjectsListV2Cache
 	}
 
 	// Params stores basic API parameters.
@@ -130,6 +131,7 @@ func NewLayer(log *zap.Logger, conns pool.Pool) Client {
 	return &layer{
 		pool:  conns,
 		log:   log,
+		cache: newListObjectsCache(),
 	}
 }
 

api/layer/object.go

@@ -13,6 +13,7 @@ import (
 	cid "github.com/nspcc-dev/neofs-api-go/pkg/container/id"
 	"github.com/nspcc-dev/neofs-api-go/pkg/object"
 	"github.com/nspcc-dev/neofs-s3-gw/api"
+	"github.com/nspcc-dev/neofs-s3-gw/creds/accessbox"
 	"go.uber.org/zap"
 )
 
@@ -258,6 +259,8 @@ func (n *layer) ListObjectsV2(ctx context.Context, p *ListObjectsParamsV2) (*Lis
 		result     ListObjectsInfoV2
 		allObjects []*ObjectInfo
 		bkt        *BucketInfo
+		cacheKey   string
+		box        *accessbox.Box
 	)
 
 	if p.MaxKeys == 0 {
@@ -268,9 +271,18 @@ func (n *layer) ListObjectsV2(ctx context.Context, p *ListObjectsParamsV2) (*Lis
 		return nil, err
 	}
 
+	if box, err = GetBoxData(ctx); err != nil {
+		return nil, err
+	}
+
+	cacheKey = createKey(box.Gate.AccessKey, bkt.CID)
+
 	if p.ContinuationToken != "" {
-		// find cache with continuation token
-	} else {
+		allObjects = n.cache.Get(p.ContinuationToken, cacheKey)
+		allObjects = trimStartAfter(p.StartAfter, allObjects)
+	}
+
+	if allObjects == nil {
 		allObjects, err = n.listSortedAllObjects(ctx, allObjectParams{
 			Bucket:     bkt,
 			Prefix:     p.Prefix,
@@ -280,13 +292,20 @@ func (n *layer) ListObjectsV2(ctx context.Context, p *ListObjectsParamsV2) (*Lis
 		if err != nil {
 			return nil, err
 		}
+
+		if p.ContinuationToken != "" {
+			allObjects = trimAfterObjectID(p.ContinuationToken, allObjects)
+		}
 	}
 
 	if len(allObjects) > p.MaxKeys {
 		result.IsTruncated = true
 
+		restObjects := allObjects[p.MaxKeys:]
+		n.cache.Put(cacheKey, restObjects)
+		result.NextContinuationToken = restObjects[0].id.String()
+
 		allObjects = allObjects[:p.MaxKeys]
-		// add  creating of cache here
 	}
 
 	for _, ov := range allObjects {
@@ -343,3 +362,23 @@ func (n *layer) listSortedAllObjects(ctx context.Context, p allObjectParams) ([]
 
 	return objects, nil
 }
+
+func trimStartAfter(startAfter string, objects []*ObjectInfo) []*ObjectInfo {
+	if objects != nil && len(startAfter) != 0 && objects[0].Name <= startAfter {
+		for i := range objects {
+			if objects[i].Name > startAfter {
+				return objects[i:]
+			}
+		}
+	}
+	return objects
+}
+
+func trimAfterObjectID(id string, objects []*ObjectInfo) []*ObjectInfo {
+	for i, obj := range objects {
+		if obj.ID().String() == id {
+			return objects[i:]
+		}
+	}
+	return objects
+}

api/layer/object_cache.go

@@ -0,0 +1,79 @@
+package layer
+
+import (
+	"sync"
+	"time"
+
+	cid "github.com/nspcc-dev/neofs-api-go/pkg/container/id"
+)
+
+/*
+	This is an implementation of a cache for ListObjectsV2 which we return to users by ContinuationToken.
+
+	The cache is a map which has a key: (access_key from AccessBox) + container_id and a value: list of objects with
+	creation time. After putting a record we start a timer (via time.AfterFunc) that removes the record after
+	defaultCacheLifetime value.
+
+	ContinuationToken in our gateway is an objectID in NeoFS.
+
+	We don't keep ContinuationToken in this structure because we assume that users who received the token can reconnect
+	to other gateways and they should be able to get a list of objects.
+	When we receive the token from the user we just try to find the cache and then we return the list of objects which
+	starts from this token (i.e. objectID).
+*/
+
+// ObjectsListV2Cache provides interface for cache of ListObjectsV2 in a layer struct.
+type (
+	ObjectsListV2Cache interface {
+		Get(token string, key string) []*ObjectInfo
+		Put(key string, objects []*ObjectInfo)
+	}
+)
+
+var (
+	defaultCacheLifetime = time.Second * 60
+)
+
+type (
+	listObjectsCache struct {
+		caches map[string]cache
+		mtx    sync.RWMutex
+	}
+	cache struct {
+		list []*ObjectInfo
+	}
+)
+
+func newListObjectsCache() *listObjectsCache {
+	return &listObjectsCache{
+		caches: make(map[string]cache),
+	}
+}
+
+func (l *listObjectsCache) Get(token, key string) []*ObjectInfo {
+	l.mtx.RLock()
+	defer l.mtx.RUnlock()
+	if val, ok := l.caches[key]; ok {
+		return trimAfterObjectID(token, val.list)
+	}
+
+	return nil
+}
+
+func (l *listObjectsCache) Put(key string, objects []*ObjectInfo) {
+	var c cache
+
+	l.mtx.Lock()
+	defer l.mtx.Unlock()
+	c.list = objects
+	l.caches[key] = c
+	time.AfterFunc(defaultCacheLifetime, func() {
+		l.mtx.Lock()
+		delete(l.caches, key)
+		l.mtx.Unlock()
+	})
+}
+
+func createKey(accessKey string, cid *cid.ID) string {
+	return accessKey + cid.String()
+}