@Override
    public String toString() {
        return "LinkData{" +
                "fromApplication=" + fromApplication +
                ", toApplication=" + toApplication +
                ", " + linkCallDataMap +
                '}';
    }
@param hostname
           host name or endpoint
@param slot
@param count
web/src/main/java/com/navercorp/pinpoint/web/applicationmap/rawdata/LinkData.java