Openfire websocket memory leaked

My openfire server chat reach high CPU and RAM.

It becomes bigger time by time.

It is 41.3MB RAM at this time, but after 5 minutes, it will be 41.5MB. Bigger then bigger.

And it will reach ~100% RAM usage at the next morning.

I just used room chat feature.

Concurency ~600 at day, ~300 at night.

Connection timeout 30 min.

Openfire version: 4.2.1

What’s my problem? And how can I optimize my server?

Thanks!