FD_SOCK is a failure detection protocol based on a ring of TCP sockets created between group members. Each member in a group connects to its neighbor (last member connects to first) thus forming a ring. Member B is suspected when its neighbor A detects abnormally closed TCP socket (presumably due to a node B crash). However, if a member B is about to leave gracefully, it lets its neighbor A know, so that it does not become suspected. The simplest FD_SOCK configuration does not take any attribute. You can just declare an empty FD_SOCK element in JGroups's Config element.

<FD_SOCK_down_thread="false" up_thread="false"/>

There available attributes in the FD_SOCK element are listed below.