rpc: add StartWhenSynchronized option, fix #2433

cli/server/server.go

@@ -506,9 +506,12 @@ func startServer(ctx *cli.Context) error {
 	}
 	errChan := make(chan error)
 	rpcServer := server.New(chain, cfg.ApplicationConfiguration.RPC, serv, oracleSrv, log, errChan)
+	serv.AddService(&rpcServer)
 
 	go serv.Start(errChan)
-	rpcServer.Start()
+	if !cfg.ApplicationConfiguration.RPC.StartWhenSynchronized {
+		rpcServer.Start()
+	}
 
 	sighupCh := make(chan os.Signal, 1)
 	signal.Notify(sighupCh, syscall.SIGHUP)
@@ -530,12 +533,14 @@ Main:
 				log.Info("SIGHUP received, restarting rpc-server")
 				rpcServer.Shutdown()
 				rpcServer = server.New(chain, cfg.ApplicationConfiguration.RPC, serv, oracleSrv, log, errChan)
-				rpcServer.Start()
+				serv.AddService(&rpcServer) // Replaces old one by service name.
+				if !cfg.ApplicationConfiguration.RPC.StartWhenSynchronized || serv.IsInSync() {
+					rpcServer.Start()
+				}
 			}
 		case <-grace.Done():
 			signal.Stop(sighupCh)
 			serv.Shutdown()
-			rpcServer.Shutdown()
 			break Main
 		}
 	}

docs/cli.md

@@ -55,6 +55,17 @@ Or specify a different network with appropriate flag like this:
 By default, the node will run in foreground using current standard output for
 logging.
 
+
+### Node synchronization
+
+Most of the services (state validation, oracle, consensus and RPC if
+configured with `StartWhenSynchronized` option) are only started after the
+node is completely synchronizaed because running them before that is either
+pointless or even dangerous. The node considers itself to be fully
+synchronized with the network if it has more than `MinPeers` neighbours and if
+at least 2/3 of them are known to have a height less than or equal to the
+current height of the node.
+
 ### Restarting node services
 
 To restart some node services without full node restart, send the SIGHUP 

docs/node-configuration.md

@@ -136,6 +136,7 @@ RPC:
   MaxFindResultItems: 100
   MaxNEP11Tokens: 100
   Port: 10332
+  StartWhenSynchronized: false
   TLSConfig:
     Address: ""
     CertFile: serv.crt
@@ -158,6 +159,10 @@ where:
 - `MaxNEP11Tokens` - limit for the number of tokens returned from
   `getnep11balances` call.
 - `Port` is an RPC server port it should be bound to.
+- `StartWhenSynchronized` controls when RPC server will be started, by default
+  (`false` setting) it's started immediately and RPC is availabe during node
+  synchronization. Setting it to `true` will make the node start RPC service only
+  after full synchronization.
 - `TLS` section configures TLS protocol.
 
 ### State Root Configuration

pkg/rpc/rpc_config.go

@@ -17,6 +17,7 @@ type (
 		MaxFindResultItems     int           `yaml:"MaxFindResultItems"`
 		MaxNEP11Tokens         int           `yaml:"MaxNEP11Tokens"`
 		Port                   uint16        `yaml:"Port"`
+		StartWhenSynchronized  bool          `yaml:"StartWhenSynchronized"`
 		TLSConfig              TLSConfig     `yaml:"TLSConfig"`
 	}
 

pkg/rpc/server/server.go

@@ -260,6 +260,9 @@ func (s *Server) Start() {
 func (s *Server) Shutdown() {
 	var httpsErr error
 
+	if !s.started.Load() {
+		return
+	}
 	// Signal to websocket writer routines and handleSubEvents.
 	close(s.shutdown)