fix(sqlite): enable WAL + working busy timeout + _txlock=immediate to stop concurrent write lockouts (#7030)

* fix(sqlite): enable WAL + working busy timeout + _txlock=immediate to stop concurrent write lockouts

common/database.go

@@ -41,4 +41,24 @@ func UsingLogDatabase(databaseType DatabaseType) bool {
 	return logDatabaseType == databaseType
 }
 
-var SQLitePath = "one-api.db?_busy_timeout=30000"
+// SQLitePath is the DSN for the default SQLite database. It uses WAL journal
+// mode so readers are never blocked by the single writer, plus a 30s busy
+// timeout for writers to queue.
+//
+// Two details are non-obvious and both are required for concurrent correctness:
+//
+//  1. The busy timeout must be passed as a `_pragma=busy_timeout(30000)` DSN
+//     parameter. The pure-Go driver (modernc.org/sqlite, used through
+//     github.com/glebarez/sqlite) silently ignores the plain `_busy_timeout=`
+//     form, so without this the effective timeout stays at SQLite's 5s default
+//     and concurrent writes surface as "database is locked" (see #6805).
+//
+//  2. `_txlock=immediate` (BEGIN IMMEDIATE) must be enabled. Without it, a
+//     transaction that first SELECTs (establishing a read snapshot) and then
+//     writes can hit SQLITE_BUSY_SNAPSHOT when another connection commits in
+//     between; the busy handler does not cover that case, so the write fails
+//     instantly no matter the timeout. BEGIN IMMEDIATE takes the write lock up
+//     front, so writers serialize through the busy timeout instead of dying on
+//     a stale snapshot. Autocommit SELECTs stay concurrent because WAL keeps
+//     readers unlocked.
+var SQLitePath = "one-api.db?_pragma=busy_timeout(30000)&_pragma=journal_mode(WAL)&_txlock=immediate"