server/clientinterface/PacketSorter.java

/* 
 * i-scream central monitoring system
 * http://www.i-scream.org.uk
 * Copyright (C) 2000-2002 i-scream
 * 
 * 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., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 */

//---PACKAGE DECLARATION---
package uk.org.iscream.cms.server.clientinterface;

//---IMPORTS---
import uk.org.iscream.cms.util.*;
import uk.org.iscream.cms.server.componentmanager.*;
import uk.org.iscream.cms.server.core.*;
import java.util.*;

/**
 * Receives data from the incoming CORBA servant, places
 * it in a Queue, and then arranges distribution to the
 * DataHandlers.
 * Has extra functionality to send data to DataHandlers
 * on a per-host basis - ie. the Client can request which
 * hosts it would like to listen for.
 *
 * @author  $Author: tdb $
 * @version $Id: PacketSorter.java,v 1.22 2003/02/05 16:43:46 tdb Exp $
 */
class PacketSorter extends Thread {

//---FINAL ATTRIBUTES---

    /**
     * The current CVS revision of this class
     */
    public final String REVISION = "$Revision: 1.22 $";
    
//---STATIC METHODS---

//---CONSTRUCTORS---

    /**
     * Creates a new PacketSorter.
     */
    public PacketSorter() {
        // set the Thread name
        setName("clientinterface.PacketSorter");
        
        ConfigurationProxy cp = ConfigurationProxy.getInstance();
        String configName = "ClientInterface";
        
        // see if this Queue needs a size limit
        try {
            int queueSizeLimit = Integer.parseInt(cp.getProperty(configName, "Queue.SizeLimit"));
            String queueRemoveAlgorithm = cp.getProperty(configName, "Queue.RemoveAlgorithm");
            int algorithm = StringUtils.getStringPos(queueRemoveAlgorithm, Queue.algorithms);
            if(algorithm != -1) {
                _logger.write(toString(), Logger.DEBUG, "Starting Queue with size limit of "+queueSizeLimit+", using remove algorithm "+queueRemoveAlgorithm);
                // we have valid values, so lets start it.
                _queue = new Queue(queueSizeLimit, algorithm);
            }
            else {
                _logger.write(toString(), Logger.WARNING, "Bad Queue Algorithm configuration, not known: "+queueRemoveAlgorithm);
                // just don't activate a limit
                _queue = new Queue();
            }
            
        } catch (PropertyNotFoundException e) {
            _logger.write(toString(), Logger.DEBUG, "Optional config not set: "+e);
            // just don't activate a limit
            _queue = new Queue();
        } catch (NumberFormatException e) {
            _logger.write(toString(), Logger.WARNING, "Bad Queue SizeLimit configuration: "+e);
            // just don't activate a limit
            _queue = new Queue();
        }
        
        // startup a monitor on this queue
        try {
            // try to get the interval, if this fails, we won't start up the monitor
            int queueMonitorInterval = Integer.parseInt(cp.getProperty(configName, "Queue.MonitorInterval"));
            String queueName = _name + " PacketSorterQueue";
            _queue.startMonitor(queueMonitorInterval*1000, queueName);
        } catch (PropertyNotFoundException e) {
            _logger.write(toString(), Logger.WARNING, "failed to find queue monitor config, disabling. " + e);
        }
        
        _hostMap = new HashMap();
        _allHostDataList = new LinkedList();
        _allHostsList = new LinkedList();
        _logger.write(toString(), Logger.SYSINIT, "created");
    }
    
//---PUBLIC METHODS---

    /**
     * Method to start the PacketSorter running. This method will
     * loop forever processing and sending data.
     */
    public void run() {
        int qID = _queue.getQueue();
        while(true) {
            // attempt to get some data from the Queue
            String xml = "";
            try {
                xml = (String) _queue.get(qID);
            }
            catch(InvalidQueueException e) {
                _logger.write(toString(), Logger.ERROR, "Queue failure: "+e);
            }
            
            XMLPacket packet = null;
            
            try {
                packet = _xmlCache.getXMLPacket(xml);
            } catch(InvalidXMLException e) {
                _logger.write(toString(), Logger.ERROR, "Invalid XML: "+e);
                // skip the rest of this loop iteration
                continue;
            }
            
            String packetType = packet.getParam("packet.attributes.type");
            // check if we need to send it regardless
            if(packetType.equals("data")) {
                String host = packet.getParam("packet.attributes.machine_name");
                
                // look in the hostMap to see if anyone wants this data
                synchronized(this) {
                    if(_hostMap.containsKey(host)) {
                        LinkedList list = (LinkedList) _hostMap.get(host);
                        Iterator i = list.iterator();
                        // push the data to the listening Handler's queue
                        while(i.hasNext()) {
                            ((Queue) i.next()).add(xml);
                        }
                    }
                }
                
                // any handler in this list wants all packets, so send
                // it on to them regardless
                synchronized(this) {
                    Iterator i = _allHostDataList.iterator();
                    while(i.hasNext()) {
                        ((Queue) i.next()).add(xml);
                    }
                }
            }
            else {
                // always send this packet to all hosts, because it's
                // "extra" data, not host data
                synchronized(this) {
                    Iterator i = _allHostsList.iterator();
                    while(i.hasNext()) {
                        ((Queue) i.next()).add(xml);
                    }
                }
            }
        }
    }
    
    /**
     * Register a DataHandler in the system. This method
     * actually takes a reference to a Queue, which should be
     * a Queue that the DataHandler is making use of.
     * It also takes a hostList, this being a semi-colon
     * seperated list of hosts that the Client the DataHandler
     * is serving has requested. If this list is simply an empty
     * String, it is assumed the Client wants to listen to all
     * host information.
     *
     * @param dhQueue a Queue being used by the DataHandler that is registering
     * @param hostList a semi-colon seperated list of hosts
     */
    public void register(Queue dhQueue, String hostList) {
        // check to see if we want all hosts
        if(hostList.equals("")) {
            synchronized(this) {
                _allHostDataList.add(dhQueue);
            }
            _logger.write(toString(), Logger.SYSMSG, "registered DataHandler for all hosts");
        }
        else {
            // go through the list of hosts
            StringTokenizer st = new StringTokenizer(hostList, ";");
            while(st.hasMoreTokens()) {
                String host = st.nextToken();
                synchronized(this) {
                    // see if we already have a list in the map for this host
                    if(_hostMap.containsKey(host)) {
                        // we do, so add to it
                        List list = (List) _hostMap.get(host);
                        list.add(dhQueue);
                    }
                    else {
                        // we don't, so create a list and put it in the map
                        LinkedList list = new LinkedList();
                        list.add(dhQueue);
                        _hostMap.put(host, list);
                    }
                }
            }
            _logger.write(toString(), Logger.SYSMSG, "registered DataHandler for hosts: "+hostList);
        }
        // always add host to our complete host list
        synchronized(this) {
            _allHostsList.add(dhQueue);
        }
    }
    
    /**
     * Deregister a DataHandler. The DataHandler should give a reference
     * to the Queue it's using, and the *same* hostList it gave when it
     * register. It is imperative that the hostList is the same, otherwise
     * there will be all sorts of problems with lists getting out of sync.
     *
     * NB: Possible future addition would be recording of hostList's.
     *
     * @param dhQueue a Queue being used by the DataHandler that is deregistering
     * @param hostList a semi-colon seperated list of hosts
     */
    public void deregister(Queue dhQueue, String hostList) {
        // go through the list of hosts
        if(hostList.equals("")) {
            synchronized(this) {
                _allHostDataList.remove(dhQueue);
            }
            _logger.write(toString(), Logger.SYSMSG, "deregistered DataHandler for all hosts");
        }
        else {
            StringTokenizer st = new StringTokenizer(hostList, ";");
            while(st.hasMoreTokens()) {
                String host = st.nextToken();
                synchronized(this) {
                    // this should in reality always be true, but best check
                    if(_hostMap.containsKey(host)) {
                        // get the list and remove the host in question
                        LinkedList list = (LinkedList) _hostMap.get(host);
                        list.remove(dhQueue);
                        // if the list is now empty, we might as well remove it
                        if(list.size()==0) {
                            _hostMap.remove(host);
                        }
                    }
                }
            }
            _logger.write(toString(), Logger.SYSMSG, "deregistered DataHandler for hosts: "+hostList);
        }
        // always remove host from our complete host list
        synchronized(this) {
            _allHostsList.remove(dhQueue);
        }
    }
    
    /**
     * Overrides the {@link java.lang.Object#toString() Object.toString()}
     * method to provide clean logging (every class should have this).
     *
     * This uses the uk.org.iscream.cms.util.NameFormat class
     * to format the toString()
     *
     * @return the name of this class and its CVS revision
     */
    public String toString() {
        return FormatName.getName(
            _name,
            getClass().getName(),
            REVISION);
    }

//---PRIVATE METHODS---

//---ACCESSOR/MUTATOR METHODS---
    
    /**
     * Accessor to return a reference to the Queue object. This
     * is needed so the ClientInterfaceServant can get add data
     * easily.
     *
     * @return a reference to our Queue object.
     */
    public Queue getQueue() {
        return _queue;
    }

//---ATTRIBUTES---

    /**
     * This is the friendly identifier of the
     * component this class is running in.
     * eg, a Filter may be called "filter1",
     * If this class does not have an owning
     * component,  a name from the configuration
     * can be placed here.  This name could also
     * be changed to null for utility classes.
     */
    private String _name = ClientInterfaceMain.NAME;

    /**
     * This holds a reference to the
     * system logger that is being used.
     */
    private Logger _logger = ReferenceManager.getInstance().getLogger();
    
    /**
     * A reference to the Queue we're using.
     */
    private Queue _queue;
    
    /**
     * A HashMap to store lists of Queue's (in the DataHandlers)
     * in a way that can be easily accessed when data comes in.
     */
    private HashMap _hostMap;
    
    /**
     * A list specifically for a Queue's associated with DataHandlers
     * that want all host information.
     */
    private LinkedList _allHostDataList;
    
    /**
     * A list of all hosts.
     */
    private LinkedList _allHostsList;
    
    /**
     * A reference to the XMLCache in use
     */
    private XMLCache _xmlCache = XMLCache.getInstance();
    
//---STATIC ATTRIBUTES---

}
Revision:	1.23
Committed:	Mon Feb 24 20:18:48 2003 UTC (21 years, 3 months ago) by tdb
Branch:	MAIN
Changes since 1.22:	+3 -3 lines
Log Message:	Fairly major commit. This will break the current version of ihost, but this had to be done really to give Pete something to test the new ihost against. The main change here is removal of the TCP Heartbeat functionality from the filter. This meant the following features stopped working :- - Heartbeat testing - Configuration checking - Service checks The heartbeat testing, specifically the monitor, now looks at the presence of UDP packets instead. Before it just looked for the presence of a TCP heartbeat packet, so the change their is fairly negligible. Of course this means heartbeat testing now relies on the UDP working... but I don't see this as a problem. Configuration checking has been repositioned in to the filtermanager. This is a backwards compatible change - the filtermanager should still perform as it should for older hosts. But now there's an extra command to check the configuration is up-to-date, with a similar format to the old TCP protocol in the filter. (although we may optimise this soon) The service checks are broken. This isn't a major issue for us as they were pretty useless in the first place. The concept is good, but the checks are just far too primitive. I expect at some point I'll work on a seperate component that just monitors services, which will replace this function. Further changes in the server include removal of the key checking code, as this relied on a bolt on to the TCP heartbeat protocol to ship the key. This got more akward than originally planned, so I'm happy to drop the idea. In the long term we hope to replace this with a public key systems for signing and even encryption. Finally, general tidy up to remove other bits of code that check for TCP heartbeat packets when they don't need to any more.
#	User	Rev	Content
1	tdb	1.19	/*
2			* i-scream central monitoring system
3	tdb	1.20	* http://www.i-scream.org.uk
4	tdb	1.19	* Copyright (C) 2000-2002 i-scream
5			*
6			* This program is free software; you can redistribute it and/or
7			* modify it under the terms of the GNU General Public License
8			* as published by the Free Software Foundation; either version 2
9			* of the License, or (at your option) any later version.
10			*
11			* This program is distributed in the hope that it will be useful,
12			* but WITHOUT ANY WARRANTY; without even the implied warranty of
13			* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14			* GNU General Public License for more details.
15			*
16			* You should have received a copy of the GNU General Public License
17			* along with this program; if not, write to the Free Software
18			* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
19			*/
20
21	tdb	1.1	//---PACKAGE DECLARATION---
22	tdb	1.18	package uk.org.iscream.cms.server.clientinterface;
23	tdb	1.1
24			//---IMPORTS---
25	tdb	1.22	import uk.org.iscream.cms.util.*;
26	tdb	1.18	import uk.org.iscream.cms.server.componentmanager.*;
27			import uk.org.iscream.cms.server.core.*;
28	tdb	1.1	import java.util.*;
29
30			/**
31			* Receives data from the incoming CORBA servant, places
32			* it in a Queue, and then arranges distribution to the
33	tdb	1.4	* DataHandlers.
34			* Has extra functionality to send data to DataHandlers
35			* on a per-host basis - ie. the Client can request which
36			* hosts it would like to listen for.
37	tdb	1.1	*
38	tdb	1.19	* @author $Author: tdb $
39	tdb	1.23	* @version $Id: PacketSorter.java,v 1.22 2003/02/05 16:43:46 tdb Exp $
40	tdb	1.1	*/
41			class PacketSorter extends Thread {
42
43			//---FINAL ATTRIBUTES---
44
45			/**
46			* The current CVS revision of this class
47			*/
48	tdb	1.23	public final String REVISION = "$Revision: 1.22 $";
49	tdb	1.1
50			//---STATIC METHODS---
51
52			//---CONSTRUCTORS---
53
54			/**
55			* Creates a new PacketSorter.
56			*/
57	tdb	1.15	public PacketSorter() {
58	tdb	1.14	// set the Thread name
59			setName("clientinterface.PacketSorter");
60
61	tdb	1.17	ConfigurationProxy cp = ConfigurationProxy.getInstance();
62			String configName = "ClientInterface";
63
64			// see if this Queue needs a size limit
65			try {
66			int queueSizeLimit = Integer.parseInt(cp.getProperty(configName, "Queue.SizeLimit"));
67			String queueRemoveAlgorithm = cp.getProperty(configName, "Queue.RemoveAlgorithm");
68			int algorithm = StringUtils.getStringPos(queueRemoveAlgorithm, Queue.algorithms);
69			if(algorithm != -1) {
70			_logger.write(toString(), Logger.DEBUG, "Starting Queue with size limit of "+queueSizeLimit+", using remove algorithm "+queueRemoveAlgorithm);
71			// we have valid values, so lets start it.
72			_queue = new Queue(queueSizeLimit, algorithm);
73			}
74			else {
75			_logger.write(toString(), Logger.WARNING, "Bad Queue Algorithm configuration, not known: "+queueRemoveAlgorithm);
76			// just don't activate a limit
77			_queue = new Queue();
78			}
79
80			} catch (PropertyNotFoundException e) {
81			_logger.write(toString(), Logger.DEBUG, "Optional config not set: "+e);
82			// just don't activate a limit
83			_queue = new Queue();
84			} catch (NumberFormatException e) {
85			_logger.write(toString(), Logger.WARNING, "Bad Queue SizeLimit configuration: "+e);
86			// just don't activate a limit
87			_queue = new Queue();
88			}
89
90	tdb	1.15	// startup a monitor on this queue
91			try {
92			// try to get the interval, if this fails, we won't start up the monitor
93	tdb	1.17	int queueMonitorInterval = Integer.parseInt(cp.getProperty(configName, "Queue.MonitorInterval"));
94	tdb	1.15	String queueName = _name + " PacketSorterQueue";
95			_queue.startMonitor(queueMonitorInterval*1000, queueName);
96			} catch (PropertyNotFoundException e) {
97			_logger.write(toString(), Logger.WARNING, "failed to find queue monitor config, disabling. " + e);
98			}
99
100	tdb	1.11	_hostMap = new HashMap();
101			_allHostDataList = new LinkedList();
102			_allHostsList = new LinkedList();
103	tdb	1.1	_logger.write(toString(), Logger.SYSINIT, "created");
104			}
105
106			//---PUBLIC METHODS---
107
108	tdb	1.4	/**
109			* Method to start the PacketSorter running. This method will
110			* loop forever processing and sending data.
111			*/
112	tdb	1.1	public void run() {
113			int qID = _queue.getQueue();
114			while(true) {
115	tdb	1.4	// attempt to get some data from the Queue
116	tdb	1.1	String xml = "";
117			try {
118			xml = (String) _queue.get(qID);
119			}
120			catch(InvalidQueueException e) {
121			_logger.write(toString(), Logger.ERROR, "Queue failure: "+e);
122			}
123
124	tdb	1.10	XMLPacket packet = null;
125
126			try {
127	tdb	1.21	packet = _xmlCache.getXMLPacket(xml);
128	tdb	1.10	} catch(InvalidXMLException e) {
129			_logger.write(toString(), Logger.ERROR, "Invalid XML: "+e);
130			// skip the rest of this loop iteration
131			continue;
132			}
133	tdb	1.1
134	tdb	1.8	String packetType = packet.getParam("packet.attributes.type");
135			// check if we need to send it regardless
136	tdb	1.23	if(packetType.equals("data")) {
137	tdb	1.8	String host = packet.getParam("packet.attributes.machine_name");
138
139			// look in the hostMap to see if anyone wants this data
140	tdb	1.11	synchronized(this) {
141			if(_hostMap.containsKey(host)) {
142			LinkedList list = (LinkedList) _hostMap.get(host);
143			Iterator i = list.iterator();
144			// push the data to the listening Handler's queue
145			while(i.hasNext()) {
146			((Queue) i.next()).add(xml);
147			}
148	tdb	1.8	}
149			}
150
151			// any handler in this list wants all packets, so send
152			// it on to them regardless
153	tdb	1.11	synchronized(this) {
154			Iterator i = _allHostDataList.iterator();
155			while(i.hasNext()) {
156			((Queue) i.next()).add(xml);
157			}
158			}
159	tdb	1.1	}
160	tdb	1.8	else {
161	tdb	1.10	// always send this packet to all hosts, because it's
162			// "extra" data, not host data
163	tdb	1.11	synchronized(this) {
164			Iterator i = _allHostsList.iterator();
165			while(i.hasNext()) {
166			((Queue) i.next()).add(xml);
167			}
168			}
169	tdb	1.2	}
170	tdb	1.1	}
171			}
172
173	tdb	1.4	/**
174			* Register a DataHandler in the system. This method
175			* actually takes a reference to a Queue, which should be
176			* a Queue that the DataHandler is making use of.
177			* It also takes a hostList, this being a semi-colon
178			* seperated list of hosts that the Client the DataHandler
179			* is serving has requested. If this list is simply an empty
180			* String, it is assumed the Client wants to listen to all
181			* host information.
182			*
183			* @param dhQueue a Queue being used by the DataHandler that is registering
184			* @param hostList a semi-colon seperated list of hosts
185			*/
186	tdb	1.12	public void register(Queue dhQueue, String hostList) {
187	tdb	1.4	// check to see if we want all hosts
188	tdb	1.2	if(hostList.equals("")) {
189	tdb	1.12	synchronized(this) {
190			_allHostDataList.add(dhQueue);
191			}
192	tdb	1.2	_logger.write(toString(), Logger.SYSMSG, "registered DataHandler for all hosts");
193			}
194			else {
195	tdb	1.4	// go through the list of hosts
196	tdb	1.2	StringTokenizer st = new StringTokenizer(hostList, ";");
197			while(st.hasMoreTokens()) {
198			String host = st.nextToken();
199	tdb	1.12	synchronized(this) {
200			// see if we already have a list in the map for this host
201			if(_hostMap.containsKey(host)) {
202			// we do, so add to it
203			List list = (List) _hostMap.get(host);
204			list.add(dhQueue);
205			}
206			else {
207			// we don't, so create a list and put it in the map
208			LinkedList list = new LinkedList();
209			list.add(dhQueue);
210			_hostMap.put(host, list);
211			}
212	tdb	1.2	}
213	tdb	1.1	}
214	tdb	1.2	_logger.write(toString(), Logger.SYSMSG, "registered DataHandler for hosts: "+hostList);
215	tdb	1.1	}
216	tdb	1.10	// always add host to our complete host list
217	tdb	1.12	synchronized(this) {
218			_allHostsList.add(dhQueue);
219			}
220	tdb	1.1	}
221
222	tdb	1.4	/**
223			* Deregister a DataHandler. The DataHandler should give a reference
224			* to the Queue it's using, and the same hostList it gave when it
225			* register. It is imperative that the hostList is the same, otherwise
226			* there will be all sorts of problems with lists getting out of sync.
227			*
228			* NB: Possible future addition would be recording of hostList's.
229			*
230			* @param dhQueue a Queue being used by the DataHandler that is deregistering
231			* @param hostList a semi-colon seperated list of hosts
232			*/
233	tdb	1.12	public void deregister(Queue dhQueue, String hostList) {
234	tdb	1.4	// go through the list of hosts
235	tdb	1.2	if(hostList.equals("")) {
236	tdb	1.12	synchronized(this) {
237			_allHostDataList.remove(dhQueue);
238			}
239	tdb	1.2	_logger.write(toString(), Logger.SYSMSG, "deregistered DataHandler for all hosts");
240			}
241			else {
242			StringTokenizer st = new StringTokenizer(hostList, ";");
243			while(st.hasMoreTokens()) {
244			String host = st.nextToken();
245	tdb	1.12	synchronized(this) {
246			// this should in reality always be true, but best check
247			if(_hostMap.containsKey(host)) {
248			// get the list and remove the host in question
249			LinkedList list = (LinkedList) _hostMap.get(host);
250			list.remove(dhQueue);
251			// if the list is now empty, we might as well remove it
252			if(list.size()==0) {
253			_hostMap.remove(host);
254			}
255	tdb	1.2	}
256	tdb	1.1	}
257			}
258	tdb	1.2	_logger.write(toString(), Logger.SYSMSG, "deregistered DataHandler for hosts: "+hostList);
259	tdb	1.1	}
260	tdb	1.10	// always remove host from our complete host list
261	tdb	1.12	synchronized(this) {
262			_allHostsList.remove(dhQueue);
263			}
264	tdb	1.1	}
265
266			/**
267			* Overrides the {@link java.lang.Object#toString() Object.toString()}
268			* method to provide clean logging (every class should have this).
269			*
270	tdb	1.22	* This uses the uk.org.iscream.cms.util.NameFormat class
271	tdb	1.1	* to format the toString()
272			*
273			* @return the name of this class and its CVS revision
274			*/
275			public String toString() {
276			return FormatName.getName(
277			_name,
278			getClass().getName(),
279			REVISION);
280			}
281
282			//---PRIVATE METHODS---
283
284			//---ACCESSOR/MUTATOR METHODS---
285	tdb	1.4
286			/**
287			* Accessor to return a reference to the Queue object. This
288			* is needed so the ClientInterfaceServant can get add data
289			* easily.
290			*
291			* @return a reference to our Queue object.
292			*/
293	tdb	1.1	public Queue getQueue() {
294			return _queue;
295			}
296
297			//---ATTRIBUTES---
298
299			/**
300			* This is the friendly identifier of the
301			* component this class is running in.
302			* eg, a Filter may be called "filter1",
303			* If this class does not have an owning
304			* component, a name from the configuration
305			* can be placed here. This name could also
306			* be changed to null for utility classes.
307			*/
308			private String _name = ClientInterfaceMain.NAME;
309
310			/**
311			* This holds a reference to the
312			* system logger that is being used.
313			*/
314			private Logger _logger = ReferenceManager.getInstance().getLogger();
315
316	tdb	1.4	/**
317			* A reference to the Queue we're using.
318			*/
319	tdb	1.1	private Queue _queue;
320
321	tdb	1.4	/**
322			* A HashMap to store lists of Queue's (in the DataHandlers)
323			* in a way that can be easily accessed when data comes in.
324			*/
325	tdb	1.11	private HashMap _hostMap;
326	tdb	1.4
327			/**
328			* A list specifically for a Queue's associated with DataHandlers
329			* that want all host information.
330	tdb	1.10	*/
331	tdb	1.11	private LinkedList _allHostDataList;
332	tdb	1.10
333			/**
334			* A list of all hosts.
335	tdb	1.4	*/
336	tdb	1.11	private LinkedList _allHostsList;
337	tdb	1.21
338			/**
339			* A reference to the XMLCache in use
340			*/
341			private XMLCache _xmlCache = XMLCache.getInstance();
342	tdb	1.1
343			//---STATIC ATTRIBUTES---
344
345			}