multi: separate account RPC server init & start

In the upcoming actions migration, we need fetch LNDs macaroons prior to
initializing the stores, as the macaroons will be required during the
migration.

This requires that we setup the connection to LND before we initialize
the stores, as we can only fetch the macaroons after the LND connection
is established.

In preparation of doing so, we cannot reference the stores when
initializing/creating the accounts RPC server object, as we do so prior
to setting up the LND connection.

This commit therefore refactors the accounts RPC server so that we
separate the initializing from the starting of the RPC server, and only
require the store reference during the actual startup of the RPC server.

Note that while this commit adds an `active atomic int32` to the RPC
server which must be set toggled before the server will process
requests, the RPC proxy and status manager will ensure that no requests
get sent to the RPC prior to LiT's subserver being set to running. This
is added to ensure that we dont introduce any nil pointer panics in
future updates though, as the RPC server would panic in requests were
actually processed prior to it having the dependencies injected during
the `Start` function.

Also note that we still keep the init of the accounts RPC server
reference prior to setting up the LND connection, as not doing so would
require that we'd refactor the registering of `GrpcSubserver`s in a more
complex and in a less elegant way.

Author: ViktorTigerstrom

accounts/rpcserver.go

@@ -3,7 +3,9 @@ package accounts
 import (
 	"context"
 	"encoding/hex"
+	"errors"
 	"fmt"
+	"sync/atomic"
 	"time"
 
 	"github.com/btcsuite/btcd/btcutil"
@@ -16,8 +18,17 @@ import (
 	"gopkg.in/macaroon.v2"
 )
 
+var (
+	// ErrServerNotActive indicates that the server has started but hasn't
+	// fully finished the startup process.
+	ErrServerNotActive = errors.New("accounts server is still in the " +
+		"process of starting")
+)
+
 // RPCServer is the main server that implements the Accounts gRPC service.
 type RPCServer struct {
+	active int32 // atomic
+
 	litrpc.UnimplementedAccountsServer
 
 	service *InterceptorService
@@ -26,13 +37,31 @@ type RPCServer struct {
 }
 
 // NewRPCServer returns a new RPC server for the given service.
-func NewRPCServer(service *InterceptorService,
-	superMacBaker litmac.Baker) *RPCServer {
+func NewRPCServer() *RPCServer {
+	return &RPCServer{}
+}
+
+// started returns true if the server has been started, and false otherwise.
+// NOTE: This function is safe for concurrent access.
+func (s *RPCServer) started() bool {
+	return atomic.LoadInt32(&s.active) != 0
+}
 
-	return &RPCServer{
-		service:       service,
-		superMacBaker: superMacBaker,
+// Start adds the necessary dependencies for the RPCServer to be able to process
+// requests, and starts the RPCServer.
+func (s *RPCServer) Start(service *InterceptorService,
+	superMacBaker litmac.Baker) error {
+
+	if s.started() {
+		return errors.New("accounts rpc server is already started")
 	}
+
+	s.service = service
+	s.superMacBaker = superMacBaker
+
+	atomic.StoreInt32(&s.active, 1)
+
+	return nil
 }
 
 // CreateAccount adds an entry to the account database. This entry represents
@@ -50,6 +79,10 @@ func (s *RPCServer) CreateAccount(ctx context.Context,
 	req *litrpc.CreateAccountRequest) (*litrpc.CreateAccountResponse,
 	error) {
 
+	if !s.started() {
+		return nil, ErrServerNotActive
+	}
+
 	log.Infof("[createaccount] label=%v, balance=%d, expiration=%d",
 		req.Label, req.AccountBalance, req.ExpirationDate)
 
@@ -110,6 +143,10 @@ func (s *RPCServer) CreateAccount(ctx context.Context,
 func (s *RPCServer) UpdateAccount(ctx context.Context,
 	req *litrpc.UpdateAccountRequest) (*litrpc.Account, error) {
 
+	if !s.started() {
+		return nil, ErrServerNotActive
+	}
+
 	log.Infof("[updateaccount] id=%s, label=%v, balance=%d, expiration=%d",
 		req.Id, req.Label, req.AccountBalance, req.ExpirationDate)
 
@@ -136,6 +173,10 @@ func (s *RPCServer) CreditAccount(ctx context.Context,
 	req *litrpc.CreditAccountRequest) (*litrpc.CreditAccountResponse,
 	error) {
 
+	if !s.started() {
+		return nil, ErrServerNotActive
+	}
+
 	if req.GetAccount() == nil {
 		return nil, fmt.Errorf("account param must be specified")
 	}
@@ -174,6 +215,10 @@ func (s *RPCServer) CreditAccount(ctx context.Context,
 func (s *RPCServer) DebitAccount(ctx context.Context,
 	req *litrpc.DebitAccountRequest) (*litrpc.DebitAccountResponse, error) {
 
+	if !s.started() {
+		return nil, ErrServerNotActive
+	}
+
 	if req.GetAccount() == nil {
 		return nil, fmt.Errorf("account param must be specified")
 	}
@@ -212,6 +257,10 @@ func (s *RPCServer) DebitAccount(ctx context.Context,
 func (s *RPCServer) ListAccounts(ctx context.Context,
 	_ *litrpc.ListAccountsRequest) (*litrpc.ListAccountsResponse, error) {
 
+	if !s.started() {
+		return nil, ErrServerNotActive
+	}
+
 	log.Info("[listaccounts]")
 
 	// Retrieve all accounts from the macaroon account store.
@@ -237,6 +286,10 @@ func (s *RPCServer) ListAccounts(ctx context.Context,
 func (s *RPCServer) AccountInfo(ctx context.Context,
 	req *litrpc.AccountInfoRequest) (*litrpc.Account, error) {
 
+	if !s.started() {
+		return nil, ErrServerNotActive
+	}
+
 	log.Infof("[accountinfo] id=%v, label=%v", req.Id, req.Label)
 
 	accountID, err := s.findAccount(ctx, req.Id, req.Label)
@@ -257,6 +310,10 @@ func (s *RPCServer) RemoveAccount(ctx context.Context,
 	req *litrpc.RemoveAccountRequest) (*litrpc.RemoveAccountResponse,
 	error) {
 
+	if !s.started() {
+		return nil, ErrServerNotActive
+	}
+
 	log.Infof("[removeaccount] id=%v, label=%v", req.Id, req.Label)
 
 	accountID, err := s.findAccount(ctx, req.Id, req.Label)

terminal.go

@@ -471,9 +471,7 @@ func (g *LightningTerminal) start(ctx context.Context) error {
 		)
 	}
 
-	g.accountRpcServer = accounts.NewRPCServer(
-		g.accountService, superMacBaker,
-	)
+	g.accountRpcServer = accounts.NewRPCServer()
 
 	g.ruleMgrs = rules.NewRuleManagerSet()
 
@@ -1025,6 +1023,21 @@ func (g *LightningTerminal) startInternalSubServers(ctx context.Context,
 	}
 	g.macaroonServiceStarted = true
 
+	superMacBaker := func(ctx context.Context, rootKeyID uint64,
+		perms []bakery.Op, caveats []macaroon.Caveat) (string, error) {
+
+		return litmac.BakeSuperMacaroon(
+			ctx, g.basicClient, rootKeyID, perms, caveats,
+		)
+	}
+
+	log.Infof("Starting LiT accounts server")
+
+	err = g.accountRpcServer.Start(g.accountService, superMacBaker)
+	if err != nil {
+		return err
+	}
+
 	if !g.cfg.Autopilot.Disable {
 		withLndVersion := func(cfg *autopilotserver.Config) {
 			cfg.LndVersion = autopilotserver.Version{