rpc: Fix block connected handler.

Fix a bug where it appeared as though a notification handler was being
attached to the dcrd RPC client, but actually no notifications were
received until the client was disconnected a new one was created.

Now, rather than delaying attaching the notification handler, it is
attached immediately upon client creation and vspd does not start
handling the received notifications until it is ready.

cmd/vspd/vspd.go

@@ -42,6 +42,8 @@ type vspd struct {
 	db      *database.VspDatabase
 	dcrd    rpc.DcrdConnect
 	wallets rpc.WalletConnect
+
+	blockNotifChan chan *wire.BlockHeader
 }
 
 // newVspd creates the essential resources required by vspd - a database, logger
@@ -56,9 +58,12 @@ func newVspd(cfg *config) (*vspd, error) {
 	log := cfg.logger("VSP")
 	rpcLog := cfg.logger("RPC")
 
+	// Create a channel to receive blockConnected notifications from dcrd.
+	blockNotifChan := make(chan *wire.BlockHeader)
+
 	// Create RPC client for local dcrd instance (used for broadcasting and
 	// checking the status of fee transactions).
-	dcrd := rpc.SetupDcrd(cfg.DcrdUser, cfg.DcrdPass, cfg.DcrdHost, cfg.dcrdCert, cfg.netParams.Params, rpcLog)
+	dcrd := rpc.SetupDcrd(cfg.DcrdUser, cfg.DcrdPass, cfg.DcrdHost, cfg.dcrdCert, cfg.netParams.Params, rpcLog, blockNotifChan)
 
 	// Create RPC client for remote dcrwallet instances (used for voting).
 	wallets := rpc.SetupWallet(cfg.walletUsers, cfg.walletPasswords, cfg.walletHosts, cfg.walletCerts, cfg.netParams.Params, rpcLog)
@@ -69,6 +74,8 @@ func newVspd(cfg *config) (*vspd, error) {
 		db:      db,
 		dcrd:    dcrd,
 		wallets: wallets,
+
+		blockNotifChan: blockNotifChan,
 	}
 
 	return v, nil
@@ -162,8 +169,7 @@ func (v *vspd) run() int {
 		return 1
 	}
 
-	// Create a channel to receive blockConnected notifications from dcrd.
+	// Start handling blockConnected notifications from dcrd.
-	notifChan := make(chan *wire.BlockHeader)
 	shutdownWg.Add(1)
 	go func() {
 		for {
@@ -171,16 +177,13 @@ func (v *vspd) run() int {
 			case <-shutdownCtx.Done():
 				shutdownWg.Done()
 				return
-			case header := <-notifChan:
+			case header := <-v.blockNotifChan:
 				v.log.Debugf("Block notification %d (%s)", header.Height, header.BlockHash().String())
 				v.blockConnected()
 			}
 		}
 	}()
 
-	// Attach notification listener to dcrd client.
-	v.dcrd.BlockConnectedHandler(notifChan)
-
 	// Loop forever attempting ensuring a dcrd connection is available, so
 	// notifications are received.
 	shutdownWg.Add(1)

rpc/dcrd.go

@@ -46,24 +46,22 @@ type DcrdConnect struct {
 	log    slog.Logger
 }
 
-func SetupDcrd(user, pass, addr string, cert []byte, params *chaincfg.Params, log slog.Logger) DcrdConnect {
+func SetupDcrd(user, pass, addr string, cert []byte, params *chaincfg.Params, log slog.Logger,
+	blockConnectedChan chan *wire.BlockHeader) DcrdConnect {
+	client := setup(user, pass, addr, cert, log)
+
+	client.notifier = &blockConnectedHandler{
+		blockConnected: blockConnectedChan,
+		log:            log,
+	}
+
 	return DcrdConnect{
-		client: setup(user, pass, addr, cert, log),
+		client: client,
 		params: params,
 		log:    log,
 	}
 }
 
-// BlockConnectedHandler attaches a blockconnected notification handler to the
-// dcrd client. Every time a notification is received, the header of the
-// connected block is sent to the provided channel.
-func (d *DcrdConnect) BlockConnectedHandler(blockConnected chan *wire.BlockHeader) {
-	d.client.notifier = &blockConnectedHandler{
-		blockConnected: blockConnected,
-		log:            d.log,
-	}
-}
-
 func (d *DcrdConnect) Close() {
 	d.client.Close()
 	d.log.Debug("dcrd client closed")