[#642] writecache: Remove usage of close channel in badger

Signed-off-by: Anton Nikiforov <an.nikiforov@yadro.com>

pkg/local_object_storage/writecache/writecachebadger/cachebadger.go

@@ -26,12 +26,12 @@ type cache struct {
 	// helps to avoid multiple flushing of one object
 	scheduled4Flush    map[oid.Address]struct{}
 	scheduled4FlushMtx sync.RWMutex
-	// closeCh is close channel, protected by modeMtx.
-	closeCh chan struct{}
 	// wg is a wait group for flush workers.
 	wg sync.WaitGroup
 	// store contains underlying database.
 	store
+	// cancel is cancel function, protected by modeMtx in Close.
+	cancel func()
 }
 
 // wcStorageType is used for write-cache operations logging.
@@ -89,11 +89,6 @@ func (c *cache) Open(_ context.Context, readOnly bool) error {
 	if err != nil {
 		return metaerr.Wrap(err)
 	}
-
-	// Opening after Close is done during maintenance mode,
-	// thus we need to create a channel here.
-	c.closeCh = make(chan struct{})
-
 	return metaerr.Wrap(c.initCounters())
 }
 
@@ -101,8 +96,10 @@ func (c *cache) Open(_ context.Context, readOnly bool) error {
 func (c *cache) Init() error {
 	c.log.Info(logs.WritecacheBadgerInitExperimental)
 	c.metrics.SetMode(c.mode)
-	c.runFlushLoop()
-	c.runGCLoop()
+	ctx, cancel := context.WithCancel(context.Background())
+	c.cancel = cancel
+	c.runFlushLoop(ctx)
+	c.runGCLoop(ctx)
 	return nil
 }
 
@@ -111,8 +108,9 @@ func (c *cache) Close() error {
 	// We cannot lock mutex for the whole operation duration
 	// because it is taken by some background workers, so `wg.Wait()` is done without modeMtx.
 	c.modeMtx.Lock()
-	if c.closeCh != nil {
-		close(c.closeCh)
+	if c.cancel != nil {
+		c.cancel()
+		c.cancel = nil
 	}
 	c.mode = mode.DegradedReadOnly // prevent new operations from being processed
 	c.modeMtx.Unlock()
@@ -122,7 +120,6 @@ func (c *cache) Close() error {
 	c.modeMtx.Lock()
 	defer c.modeMtx.Unlock()
 
-	c.closeCh = nil
 	var err error
 	if c.db != nil {
 		err = c.db.Close()