make configurable wal auto checkpoint

SQLite WAL addition disabled auto checkpoint, this
makes the WAL grow forever, not sure why I did that.

Make it configurable, set it to SQLite default.

Fixes #2204

Signed-off-by: Kristoffer Dalby <kristoffer@tailscale.com>

config-example.yaml

@@ -168,6 +168,11 @@ database:
     # https://www.sqlite.org/wal.html
     write_ahead_log: true
 
+    # Maximum number of WAL file frames before the WAL file is automatically checkpointed.
+    # https://www.sqlite.org/c3ref/wal_autocheckpoint.html
+    # Set to 0 to disable automatic checkpointing.
+    wal_autocheckpoint: 1000
+
   # # Postgres config
   # Please note that using Postgres is highly discouraged as it is only supported for legacy reasons.
   # See database.type for more information.

hscontrol/db/db.go

@@ -543,10 +543,10 @@ func openDB(cfg types.DatabaseConfig) (*gorm.DB, error) {
 		}
 
 		if cfg.Sqlite.WriteAheadLog {
-			if err := db.Exec(`
+			if err := db.Exec(fmt.Sprintf(`
 				PRAGMA journal_mode=WAL;
-				PRAGMA wal_autocheckpoint=0;
+				PRAGMA wal_autocheckpoint=%d;
-				`).Error; err != nil {
+				`, cfg.Sqlite.WALAutoCheckPoint)).Error; err != nil {
 				return nil, fmt.Errorf("setting WAL mode: %w", err)
 			}
 		}

hscontrol/types/config.go

@@ -104,6 +104,7 @@ type Nameservers struct {
 type SqliteConfig struct {
 	Path              string
 	WriteAheadLog     bool
+	WALAutoCheckPoint int
 }
 
 type PostgresConfig struct {
@@ -270,6 +271,7 @@ func LoadConfig(path string, isFile bool) error {
 	viper.SetDefault("database.postgres.conn_max_idle_time_secs", 3600)
 
 	viper.SetDefault("database.sqlite.write_ahead_log", true)
+	viper.SetDefault("database.sqlite.wal_autocheckpoint", 1000) // SQLite default
 
 	viper.SetDefault("oidc.scope", []string{oidc.ScopeOpenID, "profile", "email"})
 	viper.SetDefault("oidc.only_start_if_oidc_is_available", true)
@@ -543,6 +545,7 @@ func databaseConfig() DatabaseConfig {
 				viper.GetString("database.sqlite.path"),
 			),
 			WriteAheadLog:     viper.GetBool("database.sqlite.write_ahead_log"),
+			WALAutoCheckPoint: viper.GetInt("database.sqlite.wal_autocheckpoint"),
 		},
 		Postgres: PostgresConfig{
 			Host:               viper.GetString("database.postgres.host"),