Story #38 - CPU Usage graph

5 files changed, 315 insertions, 53 deletions

diff --git a/src/com.gluster.storage.management.server/WebContent/WEB-INF/web.xml b/src/com.gluster.storage.management.server/WebContent/WEB-INF/web.xml
index 7c20d6c7..405c4e40 100644
--- a/src/com.gluster.storage.management.server/WebContent/WEB-INF/web.xml
+++ b/src/com.gluster.storage.management.server/WebContent/WEB-INF/web.xml
@@ -81,14 +81,14 @@
 		<filter-name>springSecurityFilterChain</filter-name>
 		<url-pattern>/*</url-pattern>
 	</filter-mapping>
-	
+
 	<security-constraint>
-	<web-resource-collection>
-		<web-resource-name>Gluster Management Gateway</web-resource-name>
-		<url-pattern>/*</url-pattern>
-	</web-resource-collection>
-	<user-data-constraint>
-		<transport-guarantee>CONFIDENTIAL</transport-guarantee>
-	</user-data-constraint>
-</security-constraint>
+		<web-resource-collection>
+			<web-resource-name>Gluster Management Gateway</web-resource-name>
+			<url-pattern>/*</url-pattern>
+		</web-resource-collection>
+		<user-data-constraint>
+			<transport-guarantee>CONFIDENTIAL</transport-guarantee>
+		</user-data-constraint>
+	</security-constraint>
 </web-app>
diff --git a/src/com.gluster.storage.management.server/src/com/gluster/storage/management/server/resources/v1_0/GenericExceptionMapper.java b/src/com.gluster.storage.management.server/src/com/gluster/storage/management/server/resources/v1_0/GenericExceptionMapper.java
new file mode 100644
index 00000000..4cd7f4f9
--- /dev/null
+++ b/src/com.gluster.storage.management.server/src/com/gluster/storage/management/server/resources/v1_0/GenericExceptionMapper.java
@@ -0,0 +1,45 @@
+/*******************************************************************************
+ * Copyright (c) 2011 Gluster, Inc. <http://www.gluster.com>
+ * This file is part of Gluster Management Console.
+ *
+ * Gluster Management Console is free software; you can redistribute it and/or 
+ * modify it under the terms of the GNU Affero General Public License as published
+ * by the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *  
+ * Gluster Management Console is distributed in the hope that it will be useful, 
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Affero General Public License
+ * for more details.
+ *  
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see
+ * <http://www.gnu.org/licenses/>.
+ *******************************************************************************/
+package com.gluster.storage.management.server.resources.v1_0;
+
+import javax.ws.rs.core.MediaType;
+import javax.ws.rs.core.Response;
+import javax.ws.rs.core.Response.ResponseBuilder;
+import javax.ws.rs.ext.ExceptionMapper;
+import javax.ws.rs.ext.Provider;
+
+import com.gluster.storage.management.core.exceptions.GlusterValidationException;
+
+@Provider
+public class GenericExceptionMapper implements ExceptionMapper<Exception> {
+
+	/* (non-Javadoc)
+	 * @see javax.ws.rs.ext.ExceptionMapper#toResponse(java.lang.Throwable)
+	 */
+	@Override
+	public Response toResponse(Exception exception) {
+		ResponseBuilder builder;
+		if (exception instanceof GlusterValidationException) {
+			builder = Response.status(Response.Status.BAD_REQUEST);
+		} else {
+			builder = Response.status(Response.Status.INTERNAL_SERVER_ERROR);
+		}
+		return builder.entity(exception.getMessage()).type(MediaType.TEXT_PLAIN).build();
+	}
+}
diff --git a/src/com.gluster.storage.management.server/src/com/gluster/storage/management/server/resources/v1_0/GlusterServersResource.java b/src/com.gluster.storage.management.server/src/com/gluster/storage/management/server/resources/v1_0/GlusterServersResource.java
index a5f366a2..09391841 100644
--- a/src/com.gluster.storage.management.server/src/com/gluster/storage/management/server/resources/v1_0/GlusterServersResource.java
+++ b/src/com.gluster.storage.management.server/src/com/gluster/storage/management/server/resources/v1_0/GlusterServersResource.java
@@ -18,15 +18,21 @@
  *******************************************************************************/
 package com.gluster.storage.management.server.resources.v1_0;
 
-import static com.gluster.storage.management.core.constants.RESTConstants.FORM_PARAM_SERVER_NAME;
 import static com.gluster.storage.management.core.constants.RESTConstants.FORM_PARAM_FSTYPE;
+import static com.gluster.storage.management.core.constants.RESTConstants.FORM_PARAM_SERVER_NAME;
 import static com.gluster.storage.management.core.constants.RESTConstants.PATH_PARAM_CLUSTER_NAME;
 import static com.gluster.storage.management.core.constants.RESTConstants.PATH_PARAM_DISK_NAME;
 import static com.gluster.storage.management.core.constants.RESTConstants.PATH_PARAM_SERVER_NAME;
+import static com.gluster.storage.management.core.constants.RESTConstants.QUERY_PARAM_DETAILS;
+import static com.gluster.storage.management.core.constants.RESTConstants.QUERY_PARAM_TYPE;
 import static com.gluster.storage.management.core.constants.RESTConstants.RESOURCE_DISKS;
 import static com.gluster.storage.management.core.constants.RESTConstants.RESOURCE_PATH_CLUSTERS;
 import static com.gluster.storage.management.core.constants.RESTConstants.RESOURCE_SERVERS;
+import static com.gluster.storage.management.core.constants.RESTConstants.RESOURCE_STATISTICS;
 import static com.gluster.storage.management.core.constants.RESTConstants.RESOURCE_TASKS;
+import static com.gluster.storage.management.core.constants.RESTConstants.STATISTICS_TYPE_CPU;
+import static com.gluster.storage.management.core.constants.RESTConstants.STATISTICS_TYPE_NETWORK;
+import static com.gluster.storage.management.core.constants.RESTConstants.STATISTICS_TYPE_MEMORY;
 
 import java.util.ArrayList;
 import java.util.List;
@@ -39,6 +45,7 @@ import javax.ws.rs.PUT;
 import javax.ws.rs.Path;
 import javax.ws.rs.PathParam;
 import javax.ws.rs.Produces;
+import javax.ws.rs.QueryParam;
 import javax.ws.rs.core.MediaType;
 import javax.ws.rs.core.Response;
 
@@ -49,14 +56,15 @@ import com.gluster.storage.management.core.constants.CoreConstants;
 import com.gluster.storage.management.core.constants.RESTConstants;
 import com.gluster.storage.management.core.exceptions.ConnectionException;
 import com.gluster.storage.management.core.exceptions.GlusterRuntimeException;
+import com.gluster.storage.management.core.model.ServerStats;
 import com.gluster.storage.management.core.model.GlusterServer;
 import com.gluster.storage.management.core.model.GlusterServer.SERVER_STATUS;
 import com.gluster.storage.management.core.response.GlusterServerListResponse;
+import com.gluster.storage.management.core.response.ServerNameListResponse;
 import com.gluster.storage.management.server.data.ClusterInfo;
 import com.gluster.storage.management.server.data.ServerInfo;
 import com.gluster.storage.management.server.services.ClusterService;
 import com.gluster.storage.management.server.tasks.InitializeDiskTask;
-import com.gluster.storage.management.server.utils.GlusterUtil;
 import com.gluster.storage.management.server.utils.SshUtil;
 import com.sun.jersey.api.core.InjectParam;
 import com.sun.jersey.spi.resource.Singleton;
@@ -92,17 +100,44 @@ public class GlusterServersResource extends AbstractServersResource {
 
 	@GET
 	@Produces(MediaType.APPLICATION_JSON)
-	public Response getGlusterServersJSON(@PathParam(PATH_PARAM_CLUSTER_NAME) String clusterName) {
-		return getGlusterServers(clusterName, MediaType.APPLICATION_JSON);
+	public Response getGlusterServersJSON(@PathParam(PATH_PARAM_CLUSTER_NAME) String clusterName,
+			@QueryParam(QUERY_PARAM_DETAILS) Boolean details) {
+		return getGlusterServers(clusterName, MediaType.APPLICATION_JSON, details);
 	}
 
 	@GET
 	@Produces(MediaType.APPLICATION_XML)
-	public Response getGlusterServersXML(@PathParam(PATH_PARAM_CLUSTER_NAME) String clusterName) {
-		return getGlusterServers(clusterName, MediaType.APPLICATION_XML);
+	public Response getGlusterServersXML(@PathParam(PATH_PARAM_CLUSTER_NAME) String clusterName,
+			@QueryParam(QUERY_PARAM_DETAILS) Boolean details) {
+		return getGlusterServers(clusterName, MediaType.APPLICATION_XML, details);
 	}
+	
+	private List<GlusterServer> getGlusterServers(String clusterName, boolean fetchDetails) {
+		List<GlusterServer> glusterServers;
+		GlusterServer onlineServer = clusterService.getOnlineServer(clusterName);
+		if (onlineServer == null) {
+			throw new GlusterRuntimeException("No online servers found in cluster [" + clusterName + "]");
+		}
 
-	public Response getGlusterServers(String clusterName, String mediaType) {
+		try {
+			glusterServers = getGlusterServers(clusterName, onlineServer, fetchDetails);
+		} catch (ConnectionException e) {
+			// online server has gone offline! try with a different one.
+			onlineServer = clusterService.getNewOnlineServer(clusterName);
+			if (onlineServer == null) {
+				throw new GlusterRuntimeException("No online servers found in cluster [" + clusterName + "]");
+			}
+			glusterServers = getGlusterServers(clusterName, onlineServer, fetchDetails);
+		}
+		return glusterServers;
+	}
+
+	private Response getGlusterServers(String clusterName, String mediaType, Boolean fetchDetails) {
+		if(fetchDetails == null) {
+			// by default, fetch the server details
+			fetchDetails = true;
+		}
+		
 		List<GlusterServer> glusterServers = new ArrayList<GlusterServer>();
 
 		if (clusterName == null || clusterName.isEmpty()) {
@@ -118,37 +153,30 @@ public class GlusterServersResource extends AbstractServersResource {
 			return okResponse(new GlusterServerListResponse(glusterServers), mediaType);
 		}
 
-		GlusterServer onlineServer = clusterService.getOnlineServer(clusterName);
-		if (onlineServer == null) {
-			return errorResponse("No online servers found in cluster [" + clusterName + "]");
-		}
-
 		try {
-			glusterServers = getGlusterServers(clusterName, onlineServer);
-		} catch (ConnectionException e) {
-			// online server has gone offline! try with a different one.
-			onlineServer = clusterService.getNewOnlineServer(clusterName);
-			if (onlineServer == null) {
-				return errorResponse("No online servers found in cluster [" + clusterName + "]");
-			}
-			try {
-				glusterServers = getGlusterServers(clusterName, onlineServer);
-			} catch (Exception e1) {
-				return errorResponse(e1.getMessage());
-			}
+			glusterServers = getGlusterServers(clusterName, fetchDetails);
 		} catch (Exception e) {
 			return errorResponse(e.getMessage());
 		}
-
-		String errMsg = fetchDetailsOfServers(glusterServers, onlineServer);
-		if (!errMsg.isEmpty()) {
-			return errorResponse("Couldn't fetch details for server(s): " + errMsg);
+		
+		if(fetchDetails) {
+			return okResponse(new GlusterServerListResponse(glusterServers), mediaType);
+		} else {
+			// no details to be fetched. Return list of server names.
+			return okResponse(new ServerNameListResponse(getServerNames(glusterServers)), mediaType);
 		}
+	}
+
 
-		return okResponse(new GlusterServerListResponse(glusterServers), mediaType);
+	private List<String> getServerNames(List<GlusterServer> glusterServers) {
+		List<String> serverNames = new ArrayList<String>();
+		for(GlusterServer server : glusterServers) {
+			serverNames.add(server.getName());
+		}
+		return serverNames;
 	}
 
-	public String fetchDetailsOfServers(List<GlusterServer> glusterServers, GlusterServer onlineServer) {
+	private String fetchDetailsOfServers(List<GlusterServer> glusterServers, GlusterServer onlineServer) {
 		String errMsg = "";
 
 		for (GlusterServer server : glusterServers) {
@@ -161,7 +189,7 @@ public class GlusterServersResource extends AbstractServersResource {
 		return errMsg;
 	}
 
-	public List<GlusterServer> getGlusterServers(String clusterName, GlusterServer onlineServer) {
+	private List<GlusterServer> getGlusterServers(String clusterName, GlusterServer onlineServer, boolean fetchDetails) {
 		List<GlusterServer> glusterServers;
 		try {
 			glusterServers = glusterUtil.getGlusterServers(onlineServer);
@@ -174,11 +202,18 @@ public class GlusterServersResource extends AbstractServersResource {
 
 			glusterServers = glusterUtil.getGlusterServers(onlineServer);
 		}
+		
+		if (fetchDetails) {
+			String errMsg = fetchDetailsOfServers(glusterServers, onlineServer);
+			if (!errMsg.isEmpty()) {
+				throw new GlusterRuntimeException("Couldn't fetch details for server(s): " + errMsg);
+			}
+		}
 		return glusterServers;
 	}
 
 	@GET
-	@Path("{serverName}")
+	@Path("{" + PATH_PARAM_SERVER_NAME + "}")
 	@Produces(MediaType.APPLICATION_XML)
 	public Response getGlusterServerXML(@PathParam(PATH_PARAM_CLUSTER_NAME) String clusterName,
 			@PathParam(PATH_PARAM_SERVER_NAME) String serverName) {
@@ -186,7 +221,7 @@ public class GlusterServersResource extends AbstractServersResource {
 	}
 
 	@GET
-	@Path("{serverName}")
+	@Path("{" + PATH_PARAM_SERVER_NAME + "}")
 	@Produces(MediaType.APPLICATION_JSON)
 	public Response getGlusterServerJSON(@PathParam(PATH_PARAM_CLUSTER_NAME) String clusterName,
 			@PathParam(PATH_PARAM_SERVER_NAME) String serverName) {
@@ -428,20 +463,57 @@ public class GlusterServersResource extends AbstractServersResource {
 			return errorResponse(e.getMessage());
 		}
 	}
+	
+	@GET
+	@Produces(MediaType.APPLICATION_XML)
+	@Path(RESOURCE_STATISTICS)
+	public Response getAggregatedPerformanceDataXML(@PathParam(PATH_PARAM_CLUSTER_NAME) String clusterName,
+			@QueryParam(QUERY_PARAM_TYPE) String type) {
+		return getAggregaredPerformanceData(clusterName, type, MediaType.APPLICATION_XML);
+	}
 
-	private void setGlusterUtil(GlusterUtil glusterUtil) {
-		this.glusterUtil = glusterUtil;
+	@GET
+	@Produces(MediaType.APPLICATION_JSON)
+	@Path(RESOURCE_STATISTICS)
+	public Response getAggregaredPerformanceDataJSON(@PathParam(PATH_PARAM_CLUSTER_NAME) String clusterName,
+			@QueryParam(QUERY_PARAM_TYPE) String type) {
+		return getAggregaredPerformanceData(clusterName, type, MediaType.APPLICATION_JSON);
 	}
 
-	public static void main(String[] args) {
-		GlusterServersResource glusterServersResource = new GlusterServersResource();
-		GlusterUtil glusterUtil = new GlusterUtil();
-		glusterUtil.setSshUtil(new SshUtil());
-		glusterServersResource.setGlusterUtil(glusterUtil);
-		// System.out.println(glusterServersResource.getServerDetails("127.0.0.1").size());
+	@GET
+	@Produces(MediaType.APPLICATION_XML)
+	@Path("{" + PATH_PARAM_SERVER_NAME + "}/" + RESOURCE_STATISTICS)
+	public Response getPerformanceDataXML(@PathParam(PATH_PARAM_SERVER_NAME) String serverName, @QueryParam(QUERY_PARAM_TYPE) String type) {
+		return getPerformanceData(serverName, type, MediaType.APPLICATION_XML);
+	}
 
-		// To add a server
-		// GlusterServerResponse response = glusterServersResource.addServer("my-server");
-		// System.out.println(response.getData().getName());
+	@GET
+	@Produces(MediaType.APPLICATION_JSON)
+	@Path("{" + PATH_PARAM_SERVER_NAME + "}/" + RESOURCE_STATISTICS)
+	public Response getPerformanceDataJSON(@PathParam(PATH_PARAM_SERVER_NAME) String serverName, @QueryParam(QUERY_PARAM_TYPE) String type) {
+		return getPerformanceData(serverName, type, MediaType.APPLICATION_JSON);
+	}
+
+	private Response getAggregaredPerformanceData(String clusterName, String type, String mediaType) {
+		List<String> serverNames = getServerNames(getGlusterServers(clusterName, false));
+		if(type.equals(STATISTICS_TYPE_CPU)) {
+			return okResponse(serverUtil.fetchAggregatedCPUStats(serverNames), mediaType);
+		} else {
+			return badRequestResponse("Server Statistics for [" + type + "] not supported! Valid values are ["
+					+ STATISTICS_TYPE_CPU + ", " + STATISTICS_TYPE_NETWORK + ", " + STATISTICS_TYPE_MEMORY + "]");
+		}
+	}
+
+	private Response getPerformanceData(String serverName, String type, String mediaType) {
+		if(type.equals(STATISTICS_TYPE_CPU)) {
+			return okResponse(serverUtil.fetchCPUUsageData(serverName), mediaType);
+		} else if(type.equals(STATISTICS_TYPE_NETWORK)) {
+			return okResponse(serverUtil.fetchCPUUsageData(serverName), mediaType);
+		} else if(type.equals(STATISTICS_TYPE_MEMORY)) {
+			return okResponse(serverUtil.fetchCPUUsageData(serverName), mediaType);
+		} else {
+			return badRequestResponse("Server Statistics for [" + type + "] not supported! Valid values are ["
+					+ STATISTICS_TYPE_CPU + ", " + STATISTICS_TYPE_NETWORK + ", " + STATISTICS_TYPE_MEMORY + "]");
+		}
 	}
 }
diff --git a/src/com.gluster.storage.management.server/src/com/gluster/storage/management/server/resources/v1_0/ValidationExceptionMapper.java b/src/com.gluster.storage.management.server/src/com/gluster/storage/management/server/resources/v1_0/ValidationExceptionMapper.java
new file mode 100644
index 00000000..cab6cc62
--- /dev/null
+++ b/src/com.gluster.storage.management.server/src/com/gluster/storage/management/server/resources/v1_0/ValidationExceptionMapper.java
@@ -0,0 +1,39 @@
+/*******************************************************************************
+ * Copyright (c) 2011 Gluster, Inc. <http://www.gluster.com>
+ * This file is part of Gluster Management Console.
+ *
+ * Gluster Management Console is free software; you can redistribute it and/or 
+ * modify it under the terms of the GNU Affero General Public License as published
+ * by the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *  
+ * Gluster Management Console is distributed in the hope that it will be useful, 
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Affero General Public License
+ * for more details.
+ *  
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see
+ * <http://www.gnu.org/licenses/>.
+ *******************************************************************************/
+package com.gluster.storage.management.server.resources.v1_0;
+
+import javax.ws.rs.core.MediaType;
+import javax.ws.rs.core.Response;
+import javax.ws.rs.ext.ExceptionMapper;
+import javax.ws.rs.ext.Provider;
+
+import com.gluster.storage.management.core.exceptions.GlusterValidationException;
+
+@Provider
+public class ValidationExceptionMapper implements ExceptionMapper<GlusterValidationException> {
+
+	/* (non-Javadoc)
+	 * @see javax.ws.rs.ext.ExceptionMapper#toResponse(java.lang.Throwable)
+	 */
+	@Override
+	public Response toResponse(GlusterValidationException exception) {
+		return Response.status(Response.Status.BAD_REQUEST).entity(exception.getMessage())
+				.type(MediaType.TEXT_PLAIN).build();
+	}
+}
diff --git a/src/com.gluster.storage.management.server/src/com/gluster/storage/management/server/utils/ServerUtil.java b/src/com.gluster.storage.management.server/src/com/gluster/storage/management/server/utils/ServerUtil.java
index ae4bc919..55be59b4 100644
--- a/src/com.gluster.storage.management.server/src/com/gluster/storage/management/server/utils/ServerUtil.java
+++ b/src/com.gluster.storage.management.server/src/com/gluster/storage/management/server/utils/ServerUtil.java
@@ -22,6 +22,8 @@ package com.gluster.storage.management.server.utils;
 
 import java.io.ByteArrayInputStream;
 import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Date;
 import java.util.List;
 
 import javax.servlet.ServletContext;
@@ -29,12 +31,15 @@ import javax.xml.bind.JAXBContext;
 import javax.xml.bind.JAXBException;
 import javax.xml.bind.Unmarshaller;
 
+import org.apache.log4j.Logger;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.stereotype.Component;
 
 import com.gluster.storage.management.core.constants.CoreConstants;
 import com.gluster.storage.management.core.exceptions.ConnectionException;
 import com.gluster.storage.management.core.exceptions.GlusterRuntimeException;
+import com.gluster.storage.management.core.model.ServerStatsRow;
+import com.gluster.storage.management.core.model.ServerStats;
 import com.gluster.storage.management.core.model.Server;
 import com.gluster.storage.management.core.model.Status;
 import com.gluster.storage.management.core.response.GenericResponse;
@@ -48,6 +53,8 @@ public class ServerUtil {
 
 	@Autowired
 	private SshUtil sshUtil;
+	
+	private static final Logger logger = Logger.getLogger(ServerUtil.class);
 
 	private static final String SCRIPT_DIR = "scripts";
 	private static final String SCRIPT_COMMAND = "python";
@@ -216,4 +223,103 @@ public class ServerUtil {
 	public Status getDiskForDir(String serverName, String brickDir) {
 		return (Status) executeOnServer(true, serverName, REMOTE_SCRIPT_GET_DISK_FOR_DIR + " " + brickDir, Status.class);
 	}
+
+	public ServerStats fetchCPUUsageData(String serverName) {
+		String cpuUsageData = "<?xml version=\"1.0\" encoding=\"ISO-8859-1\"?> <xport> <meta> <start>1310468100</start> <step>300</step> <end>1310471700</end> <rows>13</rows> <columns>3</columns> <legend> <entry>user</entry> <entry>system</entry> <entry>total</entry> </legend> </meta> <data> <row><t>1310468100</t><v>NaN</v><v>4.3747778209e-01</v><v>6.6128073384e-01</v></row> <row><t>1310468400</t><v>2.3387347338e-01</v><v>4.4642717442e-01</v><v>6.8030064780e-01</v></row> <row><t>1310468700</t><v>5.5043873220e+00</v><v>6.2462376636e+00</v><v>1.1750624986e+01</v></row> <row><t>1310469000</t><v>2.4350593653e+01</v><v>2.6214585217e+01</v><v>5.0565178869e+01</v></row> <row><t>1310469300</t><v>4.0786489953e+01</v><v>4.6784713828e+01</v><v>8.7571203781e+01</v></row> <row><t>1310469600</t><v>4.1459955508e+01</v><v>5.2546309044e+01</v><v>9.4006264551e+01</v></row> <row><t>1310469900</t><v>4.2312286165e+01</v><v>5.2390588332e+01</v><v>9.4702874497e+01</v></row> <row><t>1310470200</t><v>4.2603794982e+01</v><v>5.1598861493e+01</v><v>9.4202656475e+01</v></row> <row><t>1310470500</t><v>3.8238751290e+01</v><v>4.5312089966e+01</v><v>8.3550841256e+01</v></row> <row><t>1310470800</t><v>1.7949961224e+01</v><v>2.1282058418e+01</v><v>3.9232019642e+01</v></row> <row><t>1310471100</t><v>1.2330371421e-01</v><v>4.6347832868e-01</v><v>5.8678204289e-01</v></row> <row><t>1310471400</t><v>1.6313260492e-01</v><v>5.4088119561e-01</v><v>7.0401380052e-01</v></row> <row><t>1310471700</t><v>NaN</v><v>NaN</v><v>NaN</v></row> </data> </xport>";
+		Object output = unmarshal(ServerStats.class, cpuUsageData, false);
+		if(output instanceof Status) {
+			throw new GlusterRuntimeException(((Status)output).toString());
+		}
+		return (ServerStats) output;
+	}
+	
+	private ServerStats getFirstOnlineServerCPUStats(List<String> serverNames, boolean removeServerOnError, boolean removeOnlineServer) {
+		for(String serverName : serverNames) {
+			try {
+				ServerStats stats = fetchCPUUsageData(serverName);
+				if(removeOnlineServer) {
+					serverNames.remove(serverName);
+				}
+			} catch(Exception e) {
+				// server might be offline - continue with next one
+				logger.warn("Couldn't fetch CPU stats from server [" + serverName + "]!", e);
+				if(removeServerOnError) {
+					serverNames.remove(serverName);
+				}
+				continue;
+			}
+		}
+		throw new GlusterRuntimeException("All servers offline!");
+	}
+
+	public Object fetchAggregatedCPUStats(List<String> serverNames) {
+		if(serverNames == null || serverNames.size() == 0) {
+			throw new GlusterRuntimeException("No server names passed to fetchAggregaredCPUUsageData!");
+		}
+		
+		ServerStats firstServerStats = getFirstOnlineServerCPUStats(serverNames, true, true);
+
+		ServerStats aggregatedStats = new ServerStats(firstServerStats);
+		aggregateCPUStats(serverNames, aggregatedStats);
+		return aggregatedStats;
+	}
+
+	private void aggregateCPUStats(List<String> serverNames, ServerStats aggregatedStats) {
+		int[][] dataCount = new int[aggregatedStats.getMetadata().getRowCount()][aggregatedStats.getMetadata()
+				.getLegend().size()];
+		
+		for (String serverName : serverNames) {
+			ServerStats serverStats;
+			try {
+				serverStats = fetchCPUUsageData(serverName);
+			} catch(Exception e) {
+				// server might be offline - continue with next one
+				logger.warn("Couldn't fetch CPU stats from server [" + serverName + "]!", e);
+				continue;
+			}
+			List<ServerStatsRow> serverStatsRows = addServerStats(serverStats, aggregatedStats, dataCount);
+		}
+		
+		List<ServerStatsRow> rows = aggregatedStats.getRows();
+		for(int rowNum = 0; rowNum < rows.size(); rowNum++) {
+			List<Double> data = rows.get(rowNum).getUsageData();
+			for(int columnNum = 0; columnNum < data.size(); columnNum++) {
+				data.set(columnNum, data.get(columnNum) / dataCount[rowNum][columnNum]);
+			}
+		}
+	}
+
+	/**
+	 * 
+	 * @param statsToBeAdded
+	 * @param targetStats
+	 * @param dataCount Each element of this matrix will be incremented for every valid element added
+	 * @return
+	 */
+	private List<ServerStatsRow> addServerStats(ServerStats statsToBeAdded, ServerStats targetStats, int[][] dataCount) {
+		List<ServerStatsRow> serverStatsRows = statsToBeAdded.getRows();
+		for (int rowNum = 0; rowNum < serverStatsRows.size()
+				&& rowNum < targetStats.getMetadata().getRowCount(); rowNum++) {
+			ServerStatsRow row = serverStatsRows.get(rowNum);
+			List<Double> rowData = row.getUsageData();
+			
+			List<Double> aggregatedStatsRowData = targetStats.getRows().get(rowNum).getUsageData();
+			for(int i = 1; i < targetStats.getMetadata().getLegend().size(); i++) {
+				// Add the data
+				Double data = rowData.get(i);
+				if(!data.isNaN()) {
+					// data is available. add it.
+					aggregatedStatsRowData.set(i, aggregatedStatsRowData.get(i) + data);
+					// increment record count. this will be used for calculating average of aggregated data.
+					dataCount[rowNum][i]++;
+				}
+			}
+		}
+		return serverStatsRows;
+	}
+	
+	public static void main(String[] args) {
+		ServerStats stats = new ServerUtil().fetchCPUUsageData("s1");
+		System.out.println(stats.getMetadata().getLegend());
+	}
 }