meta: fix container creation deadlock

It is prohibited to make RPC calls if you are not reading notification channel.
If last container removal and new container creation are events from a single
block, 7ec47bd deadlocks in its
(re)subscription subroutines. The logic will be improved in the future when
every notification is handled in a strict order: #3259.

Signed-off-by: Pavel Karpy <[email protected]>

Author: carpawell

pkg/services/meta/meta.go

@@ -26,6 +26,11 @@ const (
 	// rootKey is the key for the last known state root in KV data base
 	// associated with MPT.
 	rootKey = 0x00
+
+	// notificationBuffSize is a nesessary buffer for neo-go's client proper
+	// notification work; it is required to always read notifications without
+	// any blocking or making additional RPC
+	notificationBuffSize = 100
 )
 
 // NeoFSNetwork describes current NeoFS storage network state.
@@ -200,10 +205,10 @@ func New(p Parameters) (*Meta, error) {
 		net:       p.Network,
 		endpoints: p.NeoEnpoints,
 		timeout:   p.Timeout,
-		bCh:       make(chan *block.Header),
-		cnrDelEv:  make(chan *state.ContainedNotificationEvent),
-		cnrPutEv:  make(chan *state.ContainedNotificationEvent),
-		epochEv:   make(chan *state.ContainedNotificationEvent),
+		bCh:       make(chan *block.Header, notificationBuffSize),
+		cnrDelEv:  make(chan *state.ContainedNotificationEvent, notificationBuffSize),
+		cnrPutEv:  make(chan *state.ContainedNotificationEvent, notificationBuffSize),
+		epochEv:   make(chan *state.ContainedNotificationEvent, notificationBuffSize),
 		blockBuff: make(chan *block.Header, blockBuffSize),
 		storages:  storages}, nil
 }

pkg/services/meta/notifications.go

@@ -197,7 +197,7 @@ func (m *Meta) reconnect(ctx context.Context) error {
 
 	m.stM.RLock()
 	if len(m.storages) > 0 {
-		m.bCh = make(chan *block.Header)
+		m.bCh = make(chan *block.Header, notificationBuffSize)
 		m.blockSubID, err = m.subscribeForBlocks(m.bCh)
 		if err != nil {
 			m.stM.RUnlock()
@@ -206,9 +206,9 @@ func (m *Meta) reconnect(ctx context.Context) error {
 	}
 	m.stM.RUnlock()
 
-	m.cnrDelEv = make(chan *state.ContainedNotificationEvent)
-	m.cnrPutEv = make(chan *state.ContainedNotificationEvent)
-	m.epochEv = make(chan *state.ContainedNotificationEvent)
+	m.cnrDelEv = make(chan *state.ContainedNotificationEvent, notificationBuffSize)
+	m.cnrPutEv = make(chan *state.ContainedNotificationEvent, notificationBuffSize)
+	m.epochEv = make(chan *state.ContainedNotificationEvent, notificationBuffSize)
 
 	err = m.subscribeForMeta()
 	if err != nil {