#34 Use a different approach to retrieve datacenter name

 - Older version of cassandra do not expose the jmx attribute "datacenter"
   We are suppose to use the method getDatacenter which need to recieve as
   parameter the public ip of the node

src/main/java/com/criteo/nosql/cassandra/exporter/JmxScraper.java

@@ -4,7 +4,9 @@
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-import javax.management.*;
+import javax.management.MBeanAttributeInfo;
+import javax.management.MBeanServerConnection;
+import javax.management.ObjectName;
 import javax.management.openmbean.CompositeData;
 import javax.management.openmbean.CompositeType;
 import javax.management.remote.JMXConnector;
@@ -17,7 +19,6 @@
 import java.util.regex.Pattern;
 import java.util.stream.Stream;
 
-
 import static java.util.stream.Collectors.toList;
 
 
@@ -370,7 +371,11 @@ static Optional<NodeInfo> getNodeInfo(MBeanServerConnection beanConn) {
             }
 
             try {
-                datacenterName = beanConn.getAttribute(ObjectName.getInstance("org.apache.cassandra.db:type=EndpointSnitchInfo"), "Datacenter").toString();
+                String hostID = beanConn.getAttribute(ObjectName.getInstance("org.apache.cassandra.db:type=StorageService"), "LocalHostId").toString();
+                Map<String, String> hostIdToEndpoint = (Map<String, String>) beanConn.getAttribute(ObjectName.getInstance("org.apache.cassandra.db:type=StorageService"), "HostIdToEndpoint");
+                Object opParams[] = {hostIdToEndpoint.get(hostID)};
+                String opSig[] = {String.class.getName()};
+                datacenterName = beanConn.invoke(ObjectName.getInstance("org.apache.cassandra.db:type=EndpointSnitchInfo"), "getDatacenter", opParams, opSig).toString();
             } catch (Exception e) {
                 logger.error("Cannot retrieve the datacenter name information for the node", e);
                 return Optional.empty();