@Override
    public void processMessage(Message<ID> msg) throws MemberShunnedException {
      // UDP messages received from surprise members will have partial IDs.
      // Attempt to replace these with full IDs from the Membership's view.
      if (msg.getSender().isPartial()) {
        replacePartialIdentifierInMessage(msg);
      }

      handleOrDeferMessage(msg);
    }
this is invoked by JoinLeave when there is a loss of quorum in the membership system
geode-membership/src/main/java/org/apache/geode/distributed/internal/membership/gms/GMSMembership.java