/*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
/*
* RemoteEngine.java
* Copyright (C) 2000 University of Waikato, Hamilton, New Zealand
*
*/
package weka.experiment;
import weka.core.Queue;
import weka.core.RevisionHandler;
import weka.core.RevisionUtils;
import java.net.InetAddress;
import java.net.URL;
import java.net.URLClassLoader;
import java.rmi.Naming;
import java.rmi.RMISecurityManager;
import java.rmi.RemoteException;
import java.rmi.server.UnicastRemoteObject;
import java.util.Enumeration;
import java.util.Hashtable;
/**
* A general purpose server for executing Task objects sent via RMI.
*
* @author Mark Hall (mhall@cs.waikato.ac.nz)
* @version $Revision: 1.10 $
*/
public class RemoteEngine
extends UnicastRemoteObject
implements Compute, RevisionHandler {
/** for serialization */
private static final long serialVersionUID = -1021538162895448259L;
/** The name of the host that this engine is started on */
private String m_HostName = "local";
/** A queue of waiting tasks */
private Queue m_TaskQueue = new Queue();
/** A queue of corresponding ID's for tasks */
private Queue m_TaskIdQueue = new Queue();
/** A hashtable of experiment status */
private Hashtable m_TaskStatus = new Hashtable();
/** Is there a task running */
private boolean m_TaskRunning = false;
/**
* Constructor
* @param hostName name of the host
* @exception RemoteException if something goes wrong
*/
public RemoteEngine(String hostName) throws RemoteException {
super();
m_HostName = hostName;
/* launch a clean-up thread. Will purge any failed or finished
tasks still in the TaskStatus hashtable after an hour */
Thread cleanUpThread;
cleanUpThread = new Thread() {
public void run() {
while (true) {
try {
// sleep for an hour
Thread.sleep(3600000);
} catch (InterruptedException ie) {}
if (m_TaskStatus.size() > 0) {
purge();
} else {
System.err.println("RemoteEngine : purge - no tasks to check.");
}
}
}
};
cleanUpThread.setPriority(Thread.MIN_PRIORITY);
cleanUpThread.start();
}
/**
* Takes a task object and queues it for execution
* @param t the Task object to execute
* @return an identifier for the Task that can be used when querying
* Task status
*/
public synchronized Object executeTask(Task t) throws RemoteException {
String taskId = ""+System.currentTimeMillis()+":";
taskId += t.hashCode();
addTaskToQueue(t, taskId);
return taskId;
// return t.execute();
}
/**
* Returns status information on a particular task
*
* @param taskId the ID of the task to check
* @return a <code>TaskStatusInfo</code> encapsulating task status info
* @exception Exception if an error occurs
*/
public Object checkStatus(Object taskId) throws Exception {
TaskStatusInfo inf = (TaskStatusInfo)m_TaskStatus.get(taskId);
if (inf == null) {
throw new Exception("RemoteEngine ("+m_HostName+") : Task not found.");
}
TaskStatusInfo result = new TaskStatusInfo();
result.setExecutionStatus(inf.getExecutionStatus());
result.setStatusMessage(inf.getStatusMessage());
result.setTaskResult(inf.getTaskResult());
if (inf.getExecutionStatus() == TaskStatusInfo.FINISHED ||
inf.getExecutionStatus() == TaskStatusInfo.FAILED) {
System.err.println("Finished/failed Task id : "
+ taskId + " checked by client. Removing.");
inf.setTaskResult(null);
inf = null;
m_TaskStatus.remove(taskId);
}
inf = null;
return result;
}
/**
* Adds a new task to the queue.
*
* @param t a <code>Task</code> value to be added
* @param taskId the id of the task to be added
*/
private synchronized void addTaskToQueue(Task t, String taskId) {
TaskStatusInfo newTask = t.getTaskStatus();
if (newTask == null) {
newTask = new TaskStatusInfo();
}
m_TaskQueue.push(t);
m_TaskIdQueue.push(taskId);
newTask.setStatusMessage("RemoteEngine ("
+m_HostName
+") : task queued at postion: "
+m_TaskQueue.size());
// add task status to HashTable
m_TaskStatus.put(taskId, newTask);
System.err.println("Task id : " + taskId + "Queued.");
if (m_TaskRunning == false) {
startTask();
}
}
/**
* Checks to see if there are any waiting tasks, and if no task is
* currently running starts a waiting task.
*/
private void startTask() {
if (m_TaskRunning == false && m_TaskQueue.size() > 0) {
Thread activeTaskThread;
activeTaskThread = new Thread() {
public void run() {
m_TaskRunning = true;
Task currentTask = (Task)m_TaskQueue.pop();
String taskId = (String)m_TaskIdQueue.pop();
TaskStatusInfo tsi = (TaskStatusInfo)m_TaskStatus.get(taskId);
tsi.setExecutionStatus(TaskStatusInfo.PROCESSING);
tsi.setStatusMessage("RemoteEngine ("
+m_HostName
+") : task running...");
try {
System.err.println("Launching task id : "
+ taskId + "...");
currentTask.execute();
TaskStatusInfo runStatus = currentTask.getTaskStatus();
tsi.setExecutionStatus(runStatus.getExecutionStatus());
tsi.setStatusMessage("RemoteExperiment ("
+m_HostName+") "
+runStatus.getStatusMessage());
tsi.setTaskResult(runStatus.getTaskResult());
} catch (Exception ex) {
tsi.setExecutionStatus(TaskStatusInfo.FAILED);
tsi.setStatusMessage("RemoteEngine ("
+m_HostName
+") : task failed.");
System.err.println("Task id " + taskId + "Failed!");
} finally {
if (m_TaskStatus.size() == 0) {
purgeClasses();
}
m_TaskRunning = false;
// start any waiting tasks
startTask();
}
}
};
activeTaskThread.setPriority(Thread.MIN_PRIORITY);
activeTaskThread.start();
}
}
/**
* Attempts to purge class types from the virtual machine. May take some
* time as it relies on garbage collection
*/
private void purgeClasses() {
try {
// see if we can purge classes
ClassLoader prevCl =
Thread.currentThread().getContextClassLoader();
ClassLoader urlCl =
URLClassLoader.newInstance(new URL[] {new URL("file:.")}, prevCl);
Thread.currentThread().setContextClassLoader(urlCl);
} catch (Exception ex) {
ex.printStackTrace();
}
}
/**
* Checks the hash table for failed/finished tasks. Any that have been
* around for an hour or more are removed. Clients are expected to check
* on the status of their remote tasks. Checking on the status of a
* finished/failed task will remove it from the hash table, therefore
* any failed/finished tasks left lying around for more than an hour
* suggest that their client has died..
*
*/
private void purge() {
Enumeration keys = m_TaskStatus.keys();
long currentTime = System.currentTimeMillis();
System.err.println("RemoteEngine purge. Current time : " + currentTime);
while (keys.hasMoreElements()) {
String tk = (String)keys.nextElement();
System.err.print("Examining task id : " + tk + "...");
String timeString = tk.substring(0, tk.indexOf(':'));
long ts = Long.valueOf(timeString).longValue();
if (currentTime - ts > 3600000) {
TaskStatusInfo tsi = null;
tsi = (TaskStatusInfo)m_TaskStatus.get(tsi);
if ((tsi != null)
&& (tsi.getExecutionStatus() == TaskStatusInfo.FINISHED ||
tsi.getExecutionStatus() == TaskStatusInfo.FAILED)) {
System.err.println("\nTask id : "
+ tk + " has gone stale. Removing.");
m_TaskStatus.remove(tk);
tsi.setTaskResult(null);
tsi = null;
}
} else {
System.err.println("ok.");
}
}
if (m_TaskStatus.size() == 0) {
purgeClasses();
}
}
/**
* Returns the revision string.
*
* @return the revision
*/
public String getRevision() {
return RevisionUtils.extract("$Revision: 1.10 $");
}
/**
* Main method. Gets address of the local host, creates a remote engine
* object and binds it in the RMI registry. If there is no RMI registry,
* then it tries to create one with default port 1099.
*
* @param args
*/
public static void main(String[] args) {
if (System.getSecurityManager() == null) {
System.setSecurityManager(new RMISecurityManager());
}
InetAddress localhost = null;
try {
localhost = InetAddress.getLocalHost();
System.err.println("Host name : "+localhost.getHostName());
} catch (Exception ex) {
ex.printStackTrace();
}
String name;
if (localhost != null) {
name = "//"+localhost.getHostName()+"/RemoteEngine";
} else {
name = "//localhost/RemoteEngine";
}
try {
Compute engine = new RemoteEngine(name);
Naming.rebind(name, engine);
System.out.println("RemoteEngine bound in RMI registry");
} catch (Exception e) {
System.err.println("RemoteEngine exception: " +
e.getMessage());
// try to bootstrap a new registry
try {
System.err.println("Attempting to start rmi registry...");
java.rmi.registry.LocateRegistry.createRegistry(1099);
Compute engine = new RemoteEngine(name);
Naming.rebind(name, engine);
System.out.println("RemoteEngine bound in RMI registry");
} catch (Exception ex) {
ex.printStackTrace();
}
}
}
}