We experienced this problem on the IgniteRealtime.org domain, a couple of hours after we upgraded Openfire there from 3.10.3 to 4.0.0 alpha, after the 'connenctionmanager-refactoring' branch was merged.
I'm not sure if this is related:
I was investigating a connectivity issue with jabber.org. In the admin console, I observed that there was an outbound s2s connection, but not an inbound connection. I tried creating one by using my jabber.org account in Pidgin to join the open_chat muc. This attempt caused this line to be displayed in the logs:
org.jivesoftware.openfire.server.ServerDialback - TLS required for db:verify but cannot yet do this.
Also, I was no longer able to send/receive data in the MUC (using my igniterealtime account that was already joined. After a while, Pidgin warned me that I had become disconnected. I am unable to reconnect.
Performing a thread dump gave me this deadlock:
Believed fixed by reverting code.