writecache: Check whether we are in a degraded mode

Signed-off-by: Evgenii Stratonikov <e.stratonikov@yadro.com>

pkg/local_object_storage/writecache/delete.go

@@ -37,6 +37,9 @@ func (c *cache) Delete(ctx context.Context, addr oid.Address) error {
 		return ErrNotInitialized
 	}
 	defer c.modeMtx.RUnlock()
+	if c.mode.NoMetabase() {
+		return ErrDegraded
+	}
 	if c.readOnly() {
 		return ErrReadOnly
 	}

pkg/local_object_storage/writecache/get.go

@@ -41,6 +41,14 @@ func (c *cache) getInternal(ctx context.Context, saddr string, addr oid.Address)
 		c.metrics.Get(time.Since(startedAt), found, storageType)
 	}()
 
+	if !c.modeMtx.TryRLock() {
+		return nil, ErrNotInitialized
+	}
+	defer c.modeMtx.RUnlock()
+	if c.mode.NoMetabase() {
+		return nil, ErrDegraded
+	}
+
 	value, err := Get(c.db, []byte(saddr))
 	if err == nil {
 		obj := objectSDK.New()

pkg/local_object_storage/writecache/put.go

@@ -38,6 +38,9 @@ func (c *cache) Put(ctx context.Context, prm common.PutPrm) (common.PutRes, erro
 		return common.PutRes{}, ErrNotInitialized
 	}
 	defer c.modeMtx.RUnlock()
+	if c.mode.NoMetabase() {
+		return common.PutRes{}, ErrDegraded
+	}
 	if c.readOnly() {
 		return common.PutRes{}, ErrReadOnly
 	}

pkg/local_object_storage/writecache/seal.go

@@ -18,6 +18,9 @@ func (c *cache) Seal(ctx context.Context, ignoreErrors bool) error {
 
 	c.modeMtx.Lock()
 	defer c.modeMtx.Unlock()
+	if c.mode.NoMetabase() {
+		return ErrDegraded
+	}
 
 	// flush will be done by setMode
 	err := c.setMode(ctx, mode.DegradedReadOnly, ignoreErrors)

pkg/local_object_storage/writecache/writecache.go

@@ -65,4 +65,6 @@ var (
 	ErrBigObject = errors.New("too big object")
 	// ErrOutOfSpace is returned when there is no space left to put a new object.
 	ErrOutOfSpace = errors.New("no space left in the write cache")
+	// ErrDegraded is returned when writecache is in degraded mode.
+	ErrDegraded = logicerr.New("write-cache is in degraded mode")
 )