server/filter/PluginServiceCheckManager.java

//---PACKAGE DECLARATION---
package uk.ac.ukc.iscream.filter;

//---IMPORTS---
import java.io.*;
import java.util.*;

import uk.ac.ukc.iscream.util.*;
import uk.ac.ukc.iscream.componentmanager.*;
import uk.ac.ukc.iscream.core.*;

/**
 * This class setups up and manages Plugins for performing service
 * checks.  When asked to run some service checks it runs the checks
 * on the service check pipeline for that host.  If the pipleline does
 * not exist it creates a new one.
 *
 * This is a singleton class.
 *
 * ###
 * This does not fully manage the pipelines, it should check
 * if a host has not heartbeated for a while and thus remove 
 * the pipeline.  At the moment it does not.
 * A suggestions for doing this is to use the getCreated() 
 * method on the PluginServiceCheckPipeline.  This tells you when
 * according to the system time the pipeline was created.  You could
 * then have a thread that periodically checks to see if a host
 * has not run its pipeline in say two heartbeats, and thus
 * this indicates that it is no longer running.  The pipeline
 * could then be removed from the hashmap and thus be eligable
 * for gc.
 * ###
 *
 * @author  $Author: ajm4 $
 * @version $Id: PluginServiceCheckManager.java,v 1.3 2001/02/11 19:45:11 ajm4 Exp $
 */
class PluginServiceCheckManager {

//---FINAL ATTRIBUTES---

    /**
     * The current CVS revision of this class
     */
    public final String REVISION = "$Revision: 1.3 $";
    
    /**
     * file name suffix for plugin service check classes:
     */
    private final String _suffix = "__ServiceCheck";
    
//---STATIC METHODS---

    /**
     * Return a reference to the singleton class.
     * Construct it if it does not already exist, otherwise just return the reference.
     */
    public static PluginServiceCheckManager getInstance() {
        if (_instance == null){
            _instance = new PluginServiceCheckManager();
        }
        return _instance;
    }

//---CONSTRUCTORS---

    /**
     * Private Constructor - this part creates the filter pipeline
     * This is a singleton class, btw.
     */
    private PluginServiceCheckManager(){
        _logger.write(toString(), Logger.SYSINIT, "created");
    }

//---PUBLIC METHODS---

    /**
     * run all registered service checks on a given host,
     * returning XML data with information about the check.
     *
     * @param hostname the host to run service checks for
     * @return the xml output from the service checks
     */
    public String runServiceChecks(String hostname){
        if (!_hostPipelines.containsKey(hostname)) {
               _hostPipelines.put(hostname, new PluginServiceCheckPipeline(hostname, this));
        }
        return "<services>" + ((PluginServiceCheckPipeline) _hostPipelines.get(hostname)).runPipeline() + "</services>";
    }

    /**
     * Overrides the {@link java.lang.Object#toString() Object.toString()}
     * method to provide clean logging (every class should have this).
     *
     * This uses the uk.ac.ukc.iscream.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---

    /**
     * Returns a reference to the specified service check.
     * This method takes the name of the class that contains
     * a service check implementation.  It then checks to see
     * if it has loaded that class before.  If it has it returns
     * a reference to it, if not, it loads it for the first time,
     * remembers it, then returns that.
     *
     * @param className the PluginServiceCheck to be loaded
     * @return the requested PluginServiceCheck
     */
    public synchronized PluginServiceCheck getServiceCheck(String className) {
         _logger.write(toString(), Logger.DEBUG, "got request for service check - " + className);
        // see if we've already got the service check loaded
        if(_loadedServiceChecks.containsKey(className)) {
            _logger.write(toString(), Logger.DEBUG, className + " already loaded - returning reference to it.");
            return (PluginServiceCheck) _loadedServiceChecks.get(className);
        }
        // otherwise we need to load it and return
        _logger.write(toString(), Logger.DEBUG, "attempting to load service check - " + className);
        
        // Create an instance of the specified PluginServiceCheck
        // then added it to the list of already loaded service checks
        PluginServiceCheck serviceCheck = null;
        try {
            serviceCheck = (PluginServiceCheck)ClassLoader.getSystemClassLoader().loadClass(className).newInstance();
            _loadedServiceChecks.put(className, serviceCheck);
            _logger.write(toString(), Logger.DEBUG, "loaded service check - "+className+" ("+serviceCheck.getDescription()+")");
        }
        catch (InstantiationException e){
            _logger.write(toString(), Logger.ERROR, "failed to instantiate - "+className);
            _logger.write(toString(), Logger.ERROR, e.getMessage());
        }
        catch (Exception e){
            _logger.write(toString(), Logger.ERROR, "failed to add - "+className);
            _logger.write(toString(), Logger.ERROR, e.toString());
        }
        
        return serviceCheck;
    }

//---ACCESSOR/MUTATOR METHODS---

//---ATTRIBUTES---
 
    /**
     * A hash map containing host pipelines
     */
    private HashMap _hostPipelines = new HashMap();
 
    /**
     * A hash map containing host pipelines
     */
    private HashMap _loadedServiceChecks = new HashMap();
 
    /**
     * 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 = FilterMain.NAME;

    /**
     * This holds a reference to the
     * system logger that is being used.
     */
    private Logger _logger = ReferenceManager.getInstance().getLogger();
    
    /**
     * A reference to the reference manager in use
     */
    private ReferenceManager _refman = ReferenceManager.getInstance();

//---STATIC ATTRIBUTES---

    /**
     * A reference to the single instance of this class
     */
    private static PluginServiceCheckManager _instance;
}
Revision:	1.4
Committed:	Mon Feb 12 00:34:11 2001 UTC (23 years, 3 months ago) by tdb
Branch:	MAIN
Changes since 1.3:	+8 -10 lines
Log Message:	Comment changes really. This wasn't copy/pasted at all was it ? :-)
#	User	Rev	Content
1	ajm	1.1	//---PACKAGE DECLARATION---
2			package uk.ac.ukc.iscream.filter;
3
4			//---IMPORTS---
5			import java.io.*;
6			import java.util.*;
7
8			import uk.ac.ukc.iscream.util.*;
9			import uk.ac.ukc.iscream.componentmanager.*;
10			import uk.ac.ukc.iscream.core.*;
11
12			/**
13			* This class setups up and manages Plugins for performing service
14			* checks. When asked to run some service checks it runs the checks
15			* on the service check pipeline for that host. If the pipleline does
16			* not exist it creates a new one.
17			*
18			* This is a singleton class.
19			*
20			* ###
21			* This does not fully manage the pipelines, it should check
22			* if a host has not heartbeated for a while and thus remove
23			* the pipeline. At the moment it does not.
24			* A suggestions for doing this is to use the getCreated()
25			* method on the PluginServiceCheckPipeline. This tells you when
26			* according to the system time the pipeline was created. You could
27			* then have a thread that periodically checks to see if a host
28			* has not run its pipeline in say two heartbeats, and thus
29			* this indicates that it is no longer running. The pipeline
30			* could then be removed from the hashmap and thus be eligable
31			* for gc.
32			* ###
33			*
34	ajm	1.3	* @author $Author: ajm4 $
35	tdb	1.4	* @version $Id: PluginServiceCheckManager.java,v 1.3 2001/02/11 19:45:11 ajm4 Exp $
36	ajm	1.1	*/
37			class PluginServiceCheckManager {
38
39			//---FINAL ATTRIBUTES---
40
41			/**
42			* The current CVS revision of this class
43			*/
44	tdb	1.4	public final String REVISION = "$Revision: 1.3 $";
45	ajm	1.1
46			/**
47	tdb	1.4	* file name suffix for plugin service check classes:
48	ajm	1.1	*/
49			private final String _suffix = "__ServiceCheck";
50
51			//---STATIC METHODS---
52
53			/**
54	tdb	1.4	* Return a reference to the singleton class.
55	ajm	1.1	* Construct it if it does not already exist, otherwise just return the reference.
56			*/
57			public static PluginServiceCheckManager getInstance() {
58			if (_instance == null){
59	ajm	1.2	_instance = new PluginServiceCheckManager();
60	ajm	1.1	}
61			return _instance;
62			}
63
64			//---CONSTRUCTORS---
65
66			/**
67			* Private Constructor - this part creates the filter pipeline
68			* This is a singleton class, btw.
69			*/
70	ajm	1.2	private PluginServiceCheckManager(){
71	ajm	1.1	_logger.write(toString(), Logger.SYSINIT, "created");
72			}
73
74			//---PUBLIC METHODS---
75
76			/**
77	tdb	1.4	* run all registered service checks on a given host,
78			* returning XML data with information about the check.
79	ajm	1.1	*
80	tdb	1.4	* @param hostname the host to run service checks for
81			* @return the xml output from the service checks
82	ajm	1.1	*/
83			public String runServiceChecks(String hostname){
84			if (!_hostPipelines.containsKey(hostname)) {
85	ajm	1.2	_hostPipelines.put(hostname, new PluginServiceCheckPipeline(hostname, this));
86	ajm	1.1	}
87	ajm	1.2	return "<services>" + ((PluginServiceCheckPipeline) _hostPipelines.get(hostname)).runPipeline() + "</services>";
88	ajm	1.1	}
89
90			/**
91			* Overrides the {@link java.lang.Object#toString() Object.toString()}
92			* method to provide clean logging (every class should have this).
93			*
94			* This uses the uk.ac.ukc.iscream.util.NameFormat class
95			* to format the toString()
96			*
97			* @return the name of this class and its CVS revision
98			*/
99			public String toString() {
100			return FormatName.getName(
101			_name,
102			getClass().getName(),
103			REVISION);
104			}
105
106			//---PRIVATE METHODS---
107
108			/**
109			* Returns a reference to the specified service check.
110			* This method takes the name of the class that contains
111			* a service check implementation. It then checks to see
112			* if it has loaded that class before. If it has it returns
113			* a reference to it, if not, it loads it for the first time,
114			* remembers it, then returns that.
115			*
116			* @param className the PluginServiceCheck to be loaded
117			* @return the requested PluginServiceCheck
118			*/
119			public synchronized PluginServiceCheck getServiceCheck(String className) {
120	ajm	1.3	_logger.write(toString(), Logger.DEBUG, "got request for service check - " + className);
121	ajm	1.1	// see if we've already got the service check loaded
122			if(_loadedServiceChecks.containsKey(className)) {
123			_logger.write(toString(), Logger.DEBUG, className + " already loaded - returning reference to it.");
124			return (PluginServiceCheck) _loadedServiceChecks.get(className);
125			}
126			// otherwise we need to load it and return
127			_logger.write(toString(), Logger.DEBUG, "attempting to load service check - " + className);
128
129			// Create an instance of the specified PluginServiceCheck
130			// then added it to the list of already loaded service checks
131			PluginServiceCheck serviceCheck = null;
132			try {
133			serviceCheck = (PluginServiceCheck)ClassLoader.getSystemClassLoader().loadClass(className).newInstance();
134			_loadedServiceChecks.put(className, serviceCheck);
135			_logger.write(toString(), Logger.DEBUG, "loaded service check - "+className+" ("+serviceCheck.getDescription()+")");
136			}
137			catch (InstantiationException e){
138			_logger.write(toString(), Logger.ERROR, "failed to instantiate - "+className);
139			_logger.write(toString(), Logger.ERROR, e.getMessage());
140			}
141			catch (Exception e){
142			_logger.write(toString(), Logger.ERROR, "failed to add - "+className);
143			_logger.write(toString(), Logger.ERROR, e.toString());
144			}
145
146			return serviceCheck;
147			}
148
149			//---ACCESSOR/MUTATOR METHODS---
150
151			//---ATTRIBUTES---
152
153			/**
154			* A hash map containing host pipelines
155			*/
156			private HashMap _hostPipelines = new HashMap();
157
158			/**
159			* A hash map containing host pipelines
160			*/
161			private HashMap _loadedServiceChecks = new HashMap();
162
163			/**
164			* This is the friendly identifier of the
165			* component this class is running in.
166			* eg, a Filter may be called "filter1",
167			* If this class does not have an owning
168			* component, a name from the configuration
169			* can be placed here. This name could also
170			* be changed to null for utility classes.
171			*/
172			private String _name = FilterMain.NAME;
173
174			/**
175			* This holds a reference to the
176			* system logger that is being used.
177			*/
178			private Logger _logger = ReferenceManager.getInstance().getLogger();
179
180			/**
181			* A reference to the reference manager in use
182			*/
183			private ReferenceManager _refman = ReferenceManager.getInstance();
184
185			//---STATIC ATTRIBUTES---
186
187			/**
188			* A reference to the single instance of this class
189			*/
190			private static PluginServiceCheckManager _instance;
191			}