Add setting `SQLITE_JOURNAL_MODE` to enable WAL (#20535)

Co-authored-by: Andrew Thornton <art27@cantab.net>

custom/conf/app.example.ini

@@ -313,6 +313,7 @@ USER = root
 ;DB_TYPE = sqlite3
 ;PATH= ; defaults to data/gitea.db
 ;SQLITE_TIMEOUT = ; Query timeout defaults to: 500
+;SQLITE_JOURNAL_MODE = ; defaults to sqlite database default (often DELETE), can be used to enable WAL mode. https://www.sqlite.org/pragma.html#pragma_journal_mode
 ;;
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;;

docs/content/doc/advanced/config-cheat-sheet.en-us.md

@@ -382,6 +382,7 @@ The following configuration set `Content-Type: application/vnd.android.package-a
     - `verify-ca`: Enable TLS with verification of the database server certificate against its root certificate.
     - `verify-full`: Enable TLS and verify the database server name matches the given certificate in either the `Common Name` or `Subject Alternative Name` fields.
 - `SQLITE_TIMEOUT`: **500**: Query timeout for SQLite3 only.
+- `SQLITE_JOURNAL_MODE`: **""**: Change journal mode for SQlite3. Can be used to enable [WAL mode](https://www.sqlite.org/wal.html) when high load causes write congestion. See [SQlite3 docs](https://www.sqlite.org/pragma.html#pragma_journal_mode) for possible values. Defaults to the default for the database file, often DELETE.
 - `ITERATE_BUFFER_SIZE`: **50**: Internal buffer size for iterating.
 - `CHARSET`: **utf8mb4**: For MySQL only, either "utf8" or "utf8mb4". NOTICE: for "utf8mb4" you must use MySQL InnoDB > 5.6. Gitea is unable to check this.
 - `PATH`: **data/gitea.db**: For SQLite3 only, the database file path.

modules/setting/database.go

@@ -39,6 +39,7 @@ var (
 		LogSQL            bool
 		Charset           string
 		Timeout           int // seconds
+		SQLiteJournalMode string
 		UseSQLite3        bool
 		UseMySQL          bool
 		UseMSSQL          bool
@@ -91,6 +92,8 @@ func InitDBConfig() {
 
 	Database.Path = sec.Key("PATH").MustString(filepath.Join(AppDataPath, "gitea.db"))
 	Database.Timeout = sec.Key("SQLITE_TIMEOUT").MustInt(500)
+	Database.SQLiteJournalMode = sec.Key("SQLITE_JOURNAL_MODE").MustString("")
+
 	Database.MaxIdleConns = sec.Key("MAX_IDLE_CONNS").MustInt(2)
 	if Database.UseMySQL {
 		Database.ConnMaxLifetime = sec.Key("CONN_MAX_LIFETIME").MustDuration(3 * time.Second)
@@ -136,7 +139,12 @@ func DBConnStr() (string, error) {
 		if err := os.MkdirAll(path.Dir(Database.Path), os.ModePerm); err != nil {
 			return "", fmt.Errorf("Failed to create directories: %v", err)
 		}
-		connStr = fmt.Sprintf("file:%s?cache=shared&mode=rwc&_busy_timeout=%d&_txlock=immediate", Database.Path, Database.Timeout)
+		journalMode := ""
+		if Database.SQLiteJournalMode != "" {
+			journalMode = "&_journal_mode=" + Database.SQLiteJournalMode
+		}
+		connStr = fmt.Sprintf("file:%s?cache=shared&mode=rwc&_busy_timeout=%d&_txlock=immediate%s",
+			Database.Path, Database.Timeout, journalMode)
 	default:
 		return "", fmt.Errorf("Unknown database type: %s", Database.Type)
 	}