if(log.isInfoEnabled()) log.info("sender=" + sender + ", merge_id=" + merge_id);
if(log.isDebugEnabled()) log.debug("sender=" + sender + ", merge_id=" + merge_id);
    public void handleMergeRequest(Address sender, Object merge_id) {        Digest digest;        View view;        if(sender == null) {            if(log.isErrorEnabled()) log.error("sender == null; cannot send back a response");            return;        }        if(merging) {            if(log.isErrorEnabled()) log.error("merge already in progress");            sendMergeRejectedResponse(sender);            return;        }        merging=true;        this.merge_id=(Serializable)merge_id;            if(log.isInfoEnabled()) log.info("sender=" + sender + ", merge_id=" + merge_id);        digest=gms.getDigest();        view=new View(gms.view_id.copy(), gms.members.getMembers());        sendMergeResponse(sender, view, digest);    }