db_sqlite: drop mutex

See [1] for details.

[1]: https://github.com/mattn/go-sqlite3/issues/209

db_sqlite.go

@@ -6,7 +6,6 @@ import (
 	"fmt"
 	"math"
 	"strings"
-	"sync"
 	"time"
 
 	_ "github.com/mattn/go-sqlite3"
@@ -192,15 +191,17 @@ var sqliteMigrations = []string{
 }
 
 type SqliteDB struct {
-	lock sync.RWMutex
 	db *sql.DB
 }
 
 func OpenSqliteDB(source string) (Database, error) {
-	sqlSqliteDB, err := sql.Open("sqlite3", source)
+	// Open the DB with cache=shared and SetMaxOpenConns(1) to allow usage from
+	// multiple goroutines
+	sqlSqliteDB, err := sql.Open("sqlite3", source+"?cache=shared")
 	if err != nil {
 		return nil, err
 	}
+	sqlSqliteDB.SetMaxOpenConns(1)
 
 	db := &SqliteDB{db: sqlSqliteDB}
 	if err := db.upgrade(); err != nil {
@@ -212,15 +213,10 @@ func OpenSqliteDB(source string) (Database, error) {
 }
 
 func (db *SqliteDB) Close() error {
-	db.lock.Lock()
-	defer db.lock.Unlock()
 	return db.db.Close()
 }
 
 func (db *SqliteDB) upgrade() error {
-	db.lock.Lock()
-	defer db.lock.Unlock()
-
 	var version int
 	if err := db.db.QueryRow("PRAGMA user_version").Scan(&version); err != nil {
 		return fmt.Errorf("failed to query schema version: %v", err)
@@ -264,9 +260,6 @@ func (db *SqliteDB) RegisterMetrics(r prometheus.Registerer) error {
 }
 
 func (db *SqliteDB) Stats(ctx context.Context) (*DatabaseStats, error) {
-	db.lock.RLock()
-	defer db.lock.RUnlock()
-
 	ctx, cancel := context.WithTimeout(ctx, sqliteQueryTimeout)
 	defer cancel()
 
@@ -290,9 +283,6 @@ func toNullString(s string) sql.NullString {
 }
 
 func (db *SqliteDB) ListUsers(ctx context.Context) ([]User, error) {
-	db.lock.RLock()
-	defer db.lock.RUnlock()
-
 	ctx, cancel := context.WithTimeout(ctx, sqliteQueryTimeout)
 	defer cancel()
 
@@ -322,9 +312,6 @@ func (db *SqliteDB) ListUsers(ctx context.Context) ([]User, error) {
 }
 
 func (db *SqliteDB) GetUser(ctx context.Context, username string) (*User, error) {
-	db.lock.RLock()
-	defer db.lock.RUnlock()
-
 	ctx, cancel := context.WithTimeout(ctx, sqliteQueryTimeout)
 	defer cancel()
 
@@ -343,9 +330,6 @@ func (db *SqliteDB) GetUser(ctx context.Context, username string) (*User, error)
 }
 
 func (db *SqliteDB) StoreUser(ctx context.Context, user *User) error {
-	db.lock.Lock()
-	defer db.lock.Unlock()
-
 	ctx, cancel := context.WithTimeout(ctx, sqliteQueryTimeout)
 	defer cancel()
 
@@ -379,9 +363,6 @@ func (db *SqliteDB) StoreUser(ctx context.Context, user *User) error {
 }
 
 func (db *SqliteDB) DeleteUser(ctx context.Context, id int64) error {
-	db.lock.Lock()
-	defer db.lock.Unlock()
-
 	ctx, cancel := context.WithTimeout(ctx, sqliteQueryTimeout)
 	defer cancel()
 
@@ -438,9 +419,6 @@ func (db *SqliteDB) DeleteUser(ctx context.Context, id int64) error {
 }
 
 func (db *SqliteDB) ListNetworks(ctx context.Context, userID int64) ([]Network, error) {
-	db.lock.RLock()
-	defer db.lock.RUnlock()
-
 	ctx, cancel := context.WithTimeout(ctx, sqliteQueryTimeout)
 	defer cancel()
 
@@ -488,9 +466,6 @@ func (db *SqliteDB) ListNetworks(ctx context.Context, userID int64) ([]Network,
 }
 
 func (db *SqliteDB) StoreNetwork(ctx context.Context, userID int64, network *Network) error {
-	db.lock.Lock()
-	defer db.lock.Unlock()
-
 	ctx, cancel := context.WithTimeout(ctx, sqliteQueryTimeout)
 	defer cancel()
 
@@ -558,9 +533,6 @@ func (db *SqliteDB) StoreNetwork(ctx context.Context, userID int64, network *Net
 }
 
 func (db *SqliteDB) DeleteNetwork(ctx context.Context, id int64) error {
-	db.lock.Lock()
-	defer db.lock.Unlock()
-
 	ctx, cancel := context.WithTimeout(ctx, sqliteQueryTimeout)
 	defer cancel()
 
@@ -594,9 +566,6 @@ func (db *SqliteDB) DeleteNetwork(ctx context.Context, id int64) error {
 }
 
 func (db *SqliteDB) ListChannels(ctx context.Context, networkID int64) ([]Channel, error) {
-	db.lock.RLock()
-	defer db.lock.RUnlock()
-
 	ctx, cancel := context.WithTimeout(ctx, sqliteQueryTimeout)
 	defer cancel()
 
@@ -631,9 +600,6 @@ func (db *SqliteDB) ListChannels(ctx context.Context, networkID int64) ([]Channe
 }
 
 func (db *SqliteDB) StoreChannel(ctx context.Context, networkID int64, ch *Channel) error {
-	db.lock.Lock()
-	defer db.lock.Unlock()
-
 	ctx, cancel := context.WithTimeout(ctx, sqliteQueryTimeout)
 	defer cancel()
 
@@ -671,9 +637,6 @@ func (db *SqliteDB) StoreChannel(ctx context.Context, networkID int64, ch *Chann
 }
 
 func (db *SqliteDB) DeleteChannel(ctx context.Context, id int64) error {
-	db.lock.Lock()
-	defer db.lock.Unlock()
-
 	ctx, cancel := context.WithTimeout(ctx, sqliteQueryTimeout)
 	defer cancel()
 
@@ -682,9 +645,6 @@ func (db *SqliteDB) DeleteChannel(ctx context.Context, id int64) error {
 }
 
 func (db *SqliteDB) ListDeliveryReceipts(ctx context.Context, networkID int64) ([]DeliveryReceipt, error) {
-	db.lock.RLock()
-	defer db.lock.RUnlock()
-
 	ctx, cancel := context.WithTimeout(ctx, sqliteQueryTimeout)
 	defer cancel()
 
@@ -715,9 +675,6 @@ func (db *SqliteDB) ListDeliveryReceipts(ctx context.Context, networkID int64) (
 }
 
 func (db *SqliteDB) StoreClientDeliveryReceipts(ctx context.Context, networkID int64, client string, receipts []DeliveryReceipt) error {
-	db.lock.Lock()
-	defer db.lock.Unlock()
-
 	ctx, cancel := context.WithTimeout(ctx, sqliteQueryTimeout)
 	defer cancel()
 
@@ -756,9 +713,6 @@ func (db *SqliteDB) StoreClientDeliveryReceipts(ctx context.Context, networkID i
 }
 
 func (db *SqliteDB) GetReadReceipt(ctx context.Context, networkID int64, name string) (*ReadReceipt, error) {
-	db.lock.RLock()
-	defer db.lock.RUnlock()
-
 	ctx, cancel := context.WithTimeout(ctx, sqliteQueryTimeout)
 	defer cancel()
 
@@ -787,9 +741,6 @@ func (db *SqliteDB) GetReadReceipt(ctx context.Context, networkID int64, name st
 }
 
 func (db *SqliteDB) StoreReadReceipt(ctx context.Context, networkID int64, receipt *ReadReceipt) error {
-	db.lock.Lock()
-	defer db.lock.Unlock()
-
 	ctx, cancel := context.WithTimeout(ctx, sqliteQueryTimeout)
 	defer cancel()