buf.append("\"os\":{");
        final OsProbe osProbe = OsProbe.getInstance();
        buf.append("\"memory\":{");
        buf.append("\"physical\":{");
        append(buf, "free", () -> osProbe.getFreePhysicalMemorySize()).append(',');
        append(buf, "total", () -> osProbe.getTotalPhysicalMemorySize());
        buf.append("},");
        buf.append("\"swap_space\":{");