Ok I have found where is the problem. Actually it's not a bug in Swoole or my application. It's a notice log that can get disabled with log_level property of Swoole server configuration.
This happens when a Client closes swoole tab or browser (Closes client connection), so it gets disconnected so Swoole cannot retrieve users session and logs this notice.
Also if you are using bench marking tools like Apache ab or WRK, If a problem occurs, These testers will terminate all other requests and stop whole testing. So sessions get closed and logs written again.
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…