private static String mustGetProperty(String key) {
        String value = System.getProperty(key);
        Preconditions.checkState(value != null, "please specify %s", key);
        return value;
    }
The path where realtime segments declare.
<pre>
    .../rt/table/tableA/host0/seg0_0 ... segN_0
    .../rt/table/tableA/host1/seg0_1 ... segN_1
</pre>
indexr-server/src/main/java/io/indexr/server/IndexRConfig.java