waiter: adopt headers subscription for WS-based tx awaiting

Try to subscribe for headers firstly, and then if RPC server doesn't
have this ability, fallback to block subscriptions to manage transaction
awaiting.

Close #3260.

Signed-off-by: Anna Shaleva <shaleva.ann@nspcc.ru>

ROADMAP.md

@@ -58,3 +58,14 @@ NeoGo retains certain deprecated error codes: `neorpc.ErrCompatGeneric`,
 neo-project/proposals#156 (NeoGo pre-0.102.0 and all known C# versions).
 
 Removal of the deprecated RPC error codes is planned once all nodes adopt the new error standard.
+
+## Block based web-socket waiter transaction awaiting
+
+Web-socket RPC based `waiter.EventWaiter` uses `header_of_added_block` notifications
+subscription to manage transaction awaiting. To support old NeoGo RPC servers
+(older than 0.105.0) that do not have block headers subscription ability,
+event-based waiter fallbacks to the old way of block monitoring with
+`block_added` notifications subscription.
+
+Removal of stale RPC server compatibility code from `waiter.EventWaiter` is
+scheduled for May-June 2024 (~0.107.0 release).

pkg/rpcclient/waiter/waiter.go

@@ -73,6 +73,7 @@ type (
 	RPCEventBased interface {
 		RPCPollingBased
 
+		ReceiveHeadersOfAddedBlocks(flt *neorpc.BlockFilter, rcvr chan<- *block.Header) (string, error)
 		ReceiveBlocks(flt *neorpc.BlockFilter, rcvr chan<- *block.Block) (string, error)
 		ReceiveExecutions(flt *neorpc.ExecutionFilter, rcvr chan<- *state.AppExecResult) (string, error)
 		Unsubscribe(id string) error
@@ -234,6 +235,7 @@ func (w *EventBased) WaitAny(ctx context.Context, vub uint32, hashes ...util.Uin
 	var (
 		wsWaitErr     error
 		waitersActive int
+		hRcvr         = make(chan *block.Header, 2)
 		bRcvr         = make(chan *block.Block, 2)
 		aerRcvr       = make(chan *state.AppExecResult, len(hashes))
 		unsubErrs     = make(chan error)
@@ -242,16 +244,22 @@ func (w *EventBased) WaitAny(ctx context.Context, vub uint32, hashes ...util.Uin
 
 	// Execution event preceded the block event, thus wait until the VUB-th block to be sure.
 	since := vub
-	blocksID, err := w.ws.ReceiveBlocks(&neorpc.BlockFilter{Since: &since}, bRcvr)
+	blocksID, err := w.ws.ReceiveHeadersOfAddedBlocks(&neorpc.BlockFilter{Since: &since}, hRcvr)
 	if err != nil {
-		wsWaitErr = fmt.Errorf("failed to subscribe for new blocks: %w", err)
+		// Falling back to block-based subscription.
+		if errors.Is(err, neorpc.ErrInvalidParams) {
+			blocksID, err = w.ws.ReceiveBlocks(&neorpc.BlockFilter{Since: &since}, bRcvr)
+		}
+	}
+	if err != nil {
+		wsWaitErr = fmt.Errorf("failed to subscribe for new blocks/headers: %w", err)
 	} else {
 		waitersActive++
 		go func() {
 			<-exit
 			err = w.ws.Unsubscribe(blocksID)
 			if err != nil {
-				unsubErrs <- fmt.Errorf("failed to unsubscribe from blocks (id: %s): %w", blocksID, err)
+				unsubErrs <- fmt.Errorf("failed to unsubscribe from blocks/headers (id: %s): %w", blocksID, err)
 				return
 			}
 			unsubErrs <- nil
@@ -290,9 +298,20 @@ func (w *EventBased) WaitAny(ctx context.Context, vub uint32, hashes ...util.Uin
 
 	if wsWaitErr == nil && res == nil {
 		select {
+		case _, ok := <-hRcvr:
+			if !ok {
+				// We're toast, retry with non-ws client.
+				hRcvr = nil
+				bRcvr = nil
+				aerRcvr = nil
+				wsWaitErr = ErrMissedEvent
+				break
+			}
+			waitErr = ErrTxNotAccepted
 		case _, ok := <-bRcvr:
 			if !ok {
 				// We're toast, retry with non-ws client.
+				hRcvr = nil
 				bRcvr = nil
 				aerRcvr = nil
 				wsWaitErr = ErrMissedEvent
@@ -302,6 +321,7 @@ func (w *EventBased) WaitAny(ctx context.Context, vub uint32, hashes ...util.Uin
 		case aer, ok := <-aerRcvr:
 			if !ok {
 				// We're toast, retry with non-ws client.
+				hRcvr = nil
 				bRcvr = nil
 				aerRcvr = nil
 				wsWaitErr = ErrMissedEvent
@@ -321,13 +341,21 @@ func (w *EventBased) WaitAny(ctx context.Context, vub uint32, hashes ...util.Uin
 	drainLoop:
 		for {
 			select {
+			case _, ok := <-hRcvr:
+				if !ok { // Missed event means both channels are closed.
+					hRcvr = nil
+					bRcvr = nil
+					aerRcvr = nil
+				}
 			case _, ok := <-bRcvr:
 				if !ok { // Missed event means both channels are closed.
+					hRcvr = nil
 					bRcvr = nil
 					aerRcvr = nil
 				}
 			case _, ok := <-aerRcvr:
 				if !ok { // Missed event means both channels are closed.
+					hRcvr = nil
 					bRcvr = nil
 					aerRcvr = nil
 				}
@@ -349,6 +377,9 @@ func (w *EventBased) WaitAny(ctx context.Context, vub uint32, hashes ...util.Uin
 			}
 		}
 	}
+	if hRcvr != nil {
+		close(hRcvr)
+	}
 	if bRcvr != nil {
 		close(bRcvr)
 	}

pkg/rpcclient/waiter/waiter_test.go

@@ -35,6 +35,8 @@ type RPCClient struct {
 	context context.Context
 }
 
+var _ = waiter.RPCPollingBased(&RPCClient{})
+
 func (r *RPCClient) InvokeContractVerify(contract util.Uint160, params []smartcontract.Parameter, signers []transaction.Signer, witnesses ...transaction.Witness) (*result.Invoke, error) {
 	return r.invRes, r.err
 }
@@ -80,11 +82,14 @@ func (r *RPCClient) GetApplicationLog(hash util.Uint256, trig *trigger.Type) (*r
 type AwaitableRPCClient struct {
 	RPCClient
 
-	chLock     sync.RWMutex
+	chLock      sync.RWMutex
-	subBlockCh chan<- *block.Block
+	subHeaderCh chan<- *block.Header
-	subTxCh    chan<- *state.AppExecResult
+	subBlockCh  chan<- *block.Block
+	subTxCh     chan<- *state.AppExecResult
 }
 
+var _ = waiter.RPCEventBased(&AwaitableRPCClient{})
+
 func (c *AwaitableRPCClient) ReceiveBlocks(flt *neorpc.BlockFilter, rcvr chan<- *block.Block) (string, error) {
 	c.chLock.Lock()
 	defer c.chLock.Unlock()
@@ -97,6 +102,12 @@ func (c *AwaitableRPCClient) ReceiveExecutions(flt *neorpc.ExecutionFilter, rcvr
 	c.subTxCh = rcvr
 	return "2", nil
 }
+func (c *AwaitableRPCClient) ReceiveHeadersOfAddedBlocks(flt *neorpc.BlockFilter, rcvr chan<- *block.Header) (string, error) {
+	c.chLock.Lock()
+	defer c.chLock.Unlock()
+	c.subHeaderCh = rcvr
+	return "3", nil
+}
 func (c *AwaitableRPCClient) Unsubscribe(id string) error { return nil }
 
 func TestNewWaiter(t *testing.T) {
@@ -244,7 +255,7 @@ func TestWSWaiter_Wait(t *testing.T) {
 	check(t, func() {
 		c.chLock.RLock()
 		defer c.chLock.RUnlock()
-		c.subBlockCh <- &block.Block{}
+		c.subHeaderCh <- &block.Header{}
 	})
 }
 

pkg/services/rpcsrv/client_test.go

@@ -1789,53 +1789,84 @@ func TestClient_Wait(t *testing.T) {
 	defer chain.Close()
 	defer rpcSrv.Shutdown()
 
-	c, err := rpcclient.New(context.Background(), httpSrv.URL, rpcclient.Options{})
+	run := func(t *testing.T, ws bool) {
-	require.NoError(t, err)
+		acc, err := wallet.NewAccount()
-	acc, err := wallet.NewAccount()
+		require.NoError(t, err)
-	require.NoError(t, err)
-	act, err := actor.New(c, []actor.SignerAccount{
-		{
-			Signer: transaction.Signer{
-				Account: acc.ScriptHash(),
-			},
-			Account: acc,
-		},
-	})
-	require.NoError(t, err)
 
-	b, err := chain.GetBlock(chain.GetHeaderHash(1))
+		var act *actor.Actor
-	require.NoError(t, err)
+		if ws {
-	require.True(t, len(b.Transactions) > 0)
+			c, err := rpcclient.NewWS(context.Background(), "ws"+strings.TrimPrefix(httpSrv.URL, "http")+"/ws", rpcclient.WSOptions{})
+			require.NoError(t, err)
+			require.NoError(t, c.Init())
+			act, err = actor.New(c, []actor.SignerAccount{
+				{
+					Signer: transaction.Signer{
+						Account: acc.ScriptHash(),
+					},
+					Account: acc,
+				},
+			})
+			require.NoError(t, err)
+		} else {
+			c, err := rpcclient.New(context.Background(), httpSrv.URL, rpcclient.Options{})
+			require.NoError(t, err)
+			require.NoError(t, c.Init())
+			act, err = actor.New(c, []actor.SignerAccount{
+				{
+					Signer: transaction.Signer{
+						Account: acc.ScriptHash(),
+					},
+					Account: acc,
+				},
+			})
+			require.NoError(t, err)
+		}
 
-	check := func(t *testing.T, h util.Uint256, vub uint32, errExpected bool) {
+		b, err := chain.GetBlock(chain.GetHeaderHash(1))
-		rcvr := make(chan struct{})
+		require.NoError(t, err)
-		go func() {
+		require.True(t, len(b.Transactions) > 0)
-			aer, err := act.Wait(h, vub, nil)
+
-			if errExpected {
+		check := func(t *testing.T, h util.Uint256, vub uint32, errExpected bool) {
-				require.Error(t, err)
+			rcvr := make(chan struct{})
-			} else {
+			go func() {
-				require.NoError(t, err)
+				aer, err := act.Wait(h, vub, nil)
-				require.Equal(t, h, aer.Container)
+				if errExpected {
-			}
+					require.Error(t, err)
-			rcvr <- struct{}{}
+				} else {
-		}()
+					require.NoError(t, err)
-	waitloop:
+					require.Equal(t, h, aer.Container)
-		for {
+				}
-			select {
+				rcvr <- struct{}{}
-			case <-rcvr:
+			}()
-				break waitloop
+		waitloop:
-			case <-time.NewTimer(chain.GetConfig().TimePerBlock).C:
+			for {
-				t.Fatal("transaction failed to be awaited")
+				select {
+				case <-rcvr:
+					break waitloop
+				case <-time.NewTimer(chain.GetConfig().TimePerBlock).C:
+					t.Fatal("transaction failed to be awaited")
+				}
 			}
 		}
+
+		// Wait for transaction that has been persisted and VUB block has been persisted.
+		check(t, b.Transactions[0].Hash(), chain.BlockHeight()-1, false)
+		// Wait for transaction that has been persisted and VUB block hasn't yet been persisted.
+		check(t, b.Transactions[0].Hash(), chain.BlockHeight()+1, false)
+		if !ws {
+			// Wait for transaction that hasn't been persisted and VUB block has been persisted.
+			// WS client waits for the next block to be accepted to ensure that transaction wasn't
+			// persisted, and this test doesn't run chain, thus, don't run this test for WS client.
+			check(t, util.Uint256{1, 2, 3}, chain.BlockHeight()-1, true)
+		}
 	}
 
-	// Wait for transaction that has been persisted and VUB block has been persisted.
+	t.Run("client", func(t *testing.T) {
-	check(t, b.Transactions[0].Hash(), chain.BlockHeight()-1, false)
+		run(t, false)
-	// Wait for transaction that has been persisted and VUB block hasn't yet been persisted.
+	})
-	check(t, b.Transactions[0].Hash(), chain.BlockHeight()+1, false)
+	t.Run("ws client", func(t *testing.T) {
-	// Wait for transaction that hasn't been persisted and VUB block has been persisted.
+		run(t, true)
-	check(t, util.Uint256{1, 2, 3}, chain.BlockHeight()-1, true)
+	})
 }
 
 func mkSubsClient(t *testing.T, rpcSrv *Server, httpSrv *httptest.Server, local bool) *rpcclient.WSClient {