package writecache import ( "errors" "fmt" "time" "github.com/nspcc-dev/neofs-node/pkg/local_object_storage/shard/mode" ) // ErrReadOnly is returned when Put/Write is performed in a read-only mode. var ErrReadOnly = errors.New("write-cache is in read-only mode") // SetMode sets write-cache mode of operation. // When shard is put in read-only mode all objects in memory are flushed to disk // and all background jobs are suspended. func (c *cache) SetMode(m mode.Mode) error { c.modeMtx.Lock() defer c.modeMtx.Unlock() if m.ReadOnly() == c.readOnly() { c.mode = m return nil } if !c.readOnly() { // Because modeMtx is taken no new objects will arrive an all other modifying // operations are completed. // 1. Persist objects already in memory on disk. c.persistMemoryCache() } if c.db != nil { if err := c.db.Close(); err != nil { return fmt.Errorf("can't close write-cache database: %w", err) } c.db = nil } // 2. Suspend producers to ensure there are channel send operations in fly. // metaCh and directCh can be populated either during Put or in background memory persist thread. // Former possibility is eliminated by taking `modeMtx` mutex and // latter by explicit persist in the previous step. // flushCh is populated by `flush` with `modeMtx` is also taken. // Thus all producers are shutdown and we only need to wait until all channels are empty. for len(c.metaCh) != 0 || len(c.directCh) != 0 || len(c.flushCh) != 0 { c.log.Info("waiting for channels to flush") time.Sleep(time.Second) } if err := c.openStore(m.ReadOnly()); err != nil { return err } c.mode = m return nil } // readOnly returns true if current mode is read-only. // `c.modeMtx` must be taken. func (c *cache) readOnly() bool { return c.mode.ReadOnly() }