fix: shrink MySQL connection pool (50->8) so a multi-op event doesn't exhaust the shared server's max_connections (Error 1040: Too many connections), which was silently failing the on-air widget/award_refs/grid reads and making the UI look frozen

internal/db/mysql.go

@@ -129,6 +129,22 @@ func translateTextColumns(s string) string {
 // OpenMySQL opens the shared MySQL logbook, creating the database if needed,
 // then applies the (translated) embedded migrations. multiStatements is enabled
 // so multi-statement migration files run in a single Exec.
+// tuneMySQLPool sizes the connection pool for a SHARED server. A multi-operator
+// special event runs many OpsLog instances against ONE MySQL, whose max_connections
+// is a hard global limit (often 100–151). A big per-instance pool (we used 50) let
+// a handful of ops exhaust the server — "Error 1040: Too many connections" — after
+// which queries (the on-air widget, award_refs, the grid) fail silently and the UI
+// looks frozen. A modest cap with brisk idle reaping keeps each instance's server
+// footprint small so ~10+ ops fit, while still absorbing the UI's concurrent
+// logbook queries. No max lifetime: a slow first migration can run for minutes on a
+// single connection and reaping it mid-migration drops the selected database.
+func tuneMySQLPool(conn *sql.DB) {
+	conn.SetMaxOpenConns(8)
+	conn.SetMaxIdleConns(3)
+	conn.SetConnMaxIdleTime(30 * time.Second) // return idle connections to the server promptly
+	conn.SetConnMaxLifetime(0)
+}
+
 func OpenMySQL(c MySQLConfig) (*sql.DB, error) {
 	if strings.TrimSpace(c.Host) == "" {
 		return nil, fmt.Errorf("host is required")
@@ -141,18 +157,7 @@ func OpenMySQL(c MySQLConfig) (*sql.DB, error) {
 	if err != nil {
 		return nil, fmt.Errorf("open mysql: %w", err)
 	}
-	// The UI fires bursts of concurrent queries (the Preferences dialog alone
-	// loads ~8 settings in parallel, plus the grid and live cluster status). A
-	// low cap turns such a burst into a deadlock-like stall against a remote
-	// server, so keep a generous pool with idle reaping. SQLite ran uncapped.
-	conn.SetMaxOpenConns(50)
-	conn.SetMaxIdleConns(10)
-	conn.SetConnMaxIdleTime(90 * time.Second)
-	// No max lifetime: a slow server's first migration can run for minutes on a
-	// single connection, and reaping it mid-migration drops the selected database
-	// (surfacing as "Unknown database"). Idle connections are still recycled
-	// after 90s, and the driver retries stale pooled connections.
-	conn.SetConnMaxLifetime(0)
+	tuneMySQLPool(conn)
 	// Connect DIRECTLY to the database first. Only if that fails — the DB doesn't
 	// exist yet (first-time setup) or the server is unreachable — do we pay for the
 	// server-level connect + CREATE DATABASE (two more handshakes). On a normal
@@ -167,10 +172,7 @@ func OpenMySQL(c MySQLConfig) (*sql.DB, error) {
 		if err != nil {
 			return nil, fmt.Errorf("open mysql: %w", err)
 		}
-		conn.SetMaxOpenConns(50)
-		conn.SetMaxIdleConns(10)
-		conn.SetConnMaxIdleTime(90 * time.Second)
-		conn.SetConnMaxLifetime(0)
+		tuneMySQLPool(conn)
 		if err := conn.Ping(); err != nil {
 			_ = conn.Close()
 			return nil, fmt.Errorf("connect to %s: %w", name, err)