Repeated JGroups Flow Control (FC) Warning Messages and threads waiting in FC

Issue

• Warning messages like these appear in log/server.log or the console:

  WARN [org.jgroups.protocols.FC] Received two credit requests from 127.0.0.2:64842 without any intervening messages; sending 1999689
  credits
  WARN [org.jgroups.protocols.FC] Received two credit requests from 127.0.0.2:64842 without any intervening messages;
  sending 1999093 credits
  WARN [org.jgroups.protocols.FC] Received two credit requests from 127.0.0.2:64842 without any intervening messages; sending 2000000
  credits
  

• The following WARN messages are appearing non-stop in the log file over a long period

  WARN [org.jgroups.protocols.FC] Received two credit requests from 192.168.10.11:55200 without any intervening messages; sending 1986459 credits
  

• JBoss is slow and we see request threads stalling in replication activity and JGroups FlowControl:

"ajp-/127.0.0.1:8009-1" daemon prio=10 tid=0x00007f82f40bf800 nid=0x7a2a in Object.wait() [0x00007f82cddd9000]
   java.lang.Thread.State: TIMED_WAITING (on object monitor)
    at java.lang.Object.wait(Native Method)
    - waiting on <0x00000000b6794e60> (a org.jgroups.protocols.FlowControl$Credit)
    at org.jgroups.protocols.FlowControl$Credit.decrementIfEnoughCredits(FlowControl.java:553)
    - locked <0x00000000b6794e60> (a org.jgroups.protocols.FlowControl$Credit)
    at org.jgroups.protocols.UFC.handleDownMessage(UFC.java:114)