loopd+loopdb: add timeout to DB open

loopd/daemon.go

@@ -11,6 +11,7 @@ import (
 	"sync"
 	"sync/atomic"
 
+	"github.com/coreos/bbolt"
 	proxy "github.com/grpc-ecosystem/grpc-gateway/runtime"
 	"github.com/lightninglabs/lndclient"
 	"github.com/lightninglabs/loop"
@@ -128,6 +129,13 @@ func (d *Daemon) Start() error {
 	// and error handlers. If this fails, then nothing has been started yet
 	// and we can just return the error.
 	err = d.initialize()
+	if errors.Is(err, bbolt.ErrTimeout) {
+		// We're trying to be started as a standalone Loop daemon, most
+		// likely LiT is already running and blocking the DB
+		return fmt.Errorf("%v: make sure no other loop daemon "+
+			"process (standalone or embedded in "+
+			"lightning-terminal) is running", err)
+	}
 	if err != nil {
 		return err
 	}
@@ -168,7 +176,14 @@ func (d *Daemon) StartAsSubserver(lndGrpc *lndclient.GrpcLndServices) error {
 	// the swap server client, the RPC server instance and our main swap
 	// handlers. If this fails, then nothing has been started yet and we can
 	// just return the error.
-	return d.initialize()
+	err := d.initialize()
+	if errors.Is(err, bbolt.ErrTimeout) {
+		// We're trying to be started inside LiT so there most likely is
+		// another standalone Loop process blocking the DB.
+		return fmt.Errorf("%v: make sure no other loop daemon "+
+			"process is running", err)
+	}
+	return err
 }
 
 // ValidateMacaroon extracts the macaroon from the context's gRPC metadata,

loopd/macaroons.go

@@ -5,8 +5,9 @@ import (
 	"fmt"
 	"io/ioutil"
 	"os"
-	"time"
 
+	"github.com/coreos/bbolt"
+	"github.com/lightninglabs/loop/loopdb"
 	"github.com/lightningnetwork/lnd/lnrpc"
 	"github.com/lightningnetwork/lnd/macaroons"
 	"google.golang.org/grpc"
@@ -17,10 +18,6 @@ const (
 	// loopMacaroonLocation is the value we use for the loopd macaroons'
 	// "Location" field when baking them.
 	loopMacaroonLocation = "loop"
-
-	// macDatabaseOpenTimeout is how long we wait for acquiring the lock on
-	// the macaroon database before we give up with an error.
-	macDatabaseOpenTimeout = time.Second * 5
 )
 
 var (
@@ -150,8 +147,14 @@ func (d *Daemon) startMacaroonService() error {
 	var err error
 	d.macaroonService, err = macaroons.NewService(
 		d.cfg.DataDir, loopMacaroonLocation, false,
-		macDatabaseOpenTimeout, macaroons.IPLockChecker,
+		loopdb.DefaultLoopDBTimeout, macaroons.IPLockChecker,
 	)
+	if err == bbolt.ErrTimeout {
+		return fmt.Errorf("%w: couldn't obtain exclusive lock on "+
+			"%s/%s, timed out after %v", bbolt.ErrTimeout,
+			d.cfg.DataDir, "macaroons.db",
+			loopdb.DefaultLoopDBTimeout)
+	}
 	if err != nil {
 		return fmt.Errorf("unable to set up macaroon authentication: "+
 			"%v", err)

loopdb/store.go

@@ -99,9 +99,18 @@ var (
 	keyLength = 33
 )
 
-// DefaultLoopOutHtlcConfirmations is the default number of confirmations we
-// set for a loop out htlc.
-const DefaultLoopOutHtlcConfirmations uint32 = 1
+const (
+	// DefaultLoopOutHtlcConfirmations is the default number of
+	// confirmations we set for a loop out htlc.
+	DefaultLoopOutHtlcConfirmations uint32 = 1
+
+	// DefaultLoopDBTimeout is the default maximum time we wait for the
+	// Loop bbolt database to be opened. If the database is already opened
+	// by another process, the unique lock cannot be obtained. With the
+	// timeout we error out after the given time instead of just blocking
+	// for forever.
+	DefaultLoopDBTimeout = 5 * time.Second
+)
 
 // fileExists returns true if the file exists, and false otherwise.
 func fileExists(path string) bool {
@@ -139,7 +148,14 @@ func NewBoltSwapStore(dbPath string, chainParams *chaincfg.Params) (
 	// Now that we know that path exists, we'll open up bolt, which
 	// implements our default swap store.
 	path := filepath.Join(dbPath, dbFileName)
-	bdb, err := bbolt.Open(path, 0600, nil)
+	bdb, err := bbolt.Open(path, 0600, &bbolt.Options{
+		Timeout: DefaultLoopDBTimeout,
+	})
+	if err == bbolt.ErrTimeout {
+		return nil, fmt.Errorf("%w: couldn't obtain exclusive lock on "+
+			"%s, timed out after %v", bbolt.ErrTimeout, path,
+			DefaultLoopDBTimeout)
+	}
 	if err != nil {
 		return nil, err
 	}

release_notes.md

@@ -19,3 +19,6 @@ This file tracks release notes for the loop client.
 #### Breaking Changes
 
 #### Bug Fixes
+ - Instead of just blocking for forever without any apparent reason if another
+   Loop daemon process is already running, we now exit with an error after 5
+   seconds if acquiring the unique lock on the Loop `bbolt` DB fails.