Terracotta Discussion Forums

Code:

 
 Hi,
 
 i am trying to simulate central caching system using terracotta
 
 but facing few problems please help  me out..
 
 when i try to add refrence of ArrayList or Map in DSO object 
 and then try to update throws exception.
 
 Platform Detail:
 
 >TerraCotta 2.6.2
 >JDK 1.5_012
 >dso-boot-hotspot_win32_150_12.jar
 >Winxp
 
 
 Codes :
 
 >TerraCottaCache.java 
   have DSO object "internalCache" 
   internalCache is a hashmap for central cache
 
 
 >SingleCacheTest.java
   commandline based cache control
   which allows adding map,list...
 
 
 
 
 //---------------------- TerraCottaCache.java ----------------------//
 
 /**
  * 
  */
 package com.zycus.utils.tc.cache;
 
 import java.util.HashMap;
 import java.util.Map;
 
 /**
  * @author dhruv.patel
  *
  */
 public class TerraCottaCache
 {
 	private HashMap	internalCache;
 
 	/**
 	 * 
 	 */
 	public TerraCottaCache()
 	{
 		internalCache = new HashMap();
 	}
 
 	/**
 	 * 
 	 * <pre>
 	 * </pre>
 	 * @param key
 	 * @param value
 	 */
 	public void put(Object key, Object value)
 	{
 		internalCache.put(key, value);
 	}
 
 	/**
 	 * 
 	 * <pre>
 	 * </pre>
 	 * @param key
 	 * @return Object
 	 */
 	public Object get(Object key)
 	{
 		return internalCache.get(key);
 	}
 
 	/**
 	 * 
 	 * <pre>
 	 * </pre>
 	 * @param key
 	 * @return object
 	 */
 	public Object remove(Object key)
 	{
 		return internalCache.remove(key);
 	}
 
 	/**
 	 * 
 	 * <pre>
 	 * </pre>
 	 */
 	public void clear()
 	{
 		internalCache.clear();
 	}
 
 	/**
 	 * 
 	 * <pre>
 	 * </pre>
 	 * @return grt map
 	 */
 	public Map getMap()
 	{
 		return internalCache;
 	}
 }
 
 
 //---------------------- SingleCacheTest.java ----------------------//
 
 /**
  * 
  */
 package com.zycus.utils.tc.cache.test;
 
 import java.io.BufferedReader;
 import java.io.IOException;
 import java.io.InputStreamReader;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.Iterator;
 import java.util.Map;
 import java.util.Random;
 import java.util.Vector;
 import java.util.Map.Entry;
 
 import com.zycus.utils.tc.cache.TerraCottaCache;
 
 /**
  * @author dhruv.patel
  *
  */
 public class SingleCacheTest
 {
 	private TerraCottaCache	cache;
 
 	/**
 	 * 
 	 */
 	public SingleCacheTest()
 	{
 		cache = new TerraCottaCache();
 	}
 
 	/**
 	 * <pre>
 	 * </pre>
 	 */
 	public void addData()
 	{
 		Random random = new Random();
 		for (int index = 0; index < 10; index++)
 		{
 			int randomNo = random.nextInt(1000);
 			cache.put(randomNo + "", randomNo + "");
 		}
 		System.out.println("added");
 	}
 
 	/**
 	 * <pre>
 	 * </pre>
 	 */
 	public void addList()
 	{
 		Vector list = (Vector) cache.get("list");
 
 		if (list == null)
 		{
 			list = new Vector();
 			cache.put("list", list);
 		}
 		Random random = new Random();
 		for (int index = 0; index < 10; index++)
 		{
 			int randomNo = random.nextInt(1000);
 			list.add(randomNo + "");
 		}
 		System.out.println("list added");
 	}
 
 	/**
 	 * <pre>
 	 * </pre>
 	 */
 	public void addMap()
 	{
 		Map map = (Map) cache.get("map");
 		if (map == null)
 		{
 			map = Collections.synchronizedMap(new HashMap());
 			cache.put("map", map);
 		}
 		Random random = new Random();
 		for (int index = 0; index < 10; index++)
 		{
 			int randomNo = random.nextInt(1000);
 			map.put(randomNo + "", randomNo + "");
 		}
 		System.out.println("map added");
 	}
 
 	/**
 	 * <pre>
 	 * </pre>
 	 */
 	public void clearData()
 	{
 		cache.clear();
 		System.out.println("cleared");
 	}
 
 	/**
 	 * <pre>
 	 * </pre>
 	 */
 	public void showData()
 	{
 		Map cacheMap = cache.getMap();
 		Iterator cacheIterator = cacheMap.entrySet().iterator();
 		Entry entry = null;
 		System.out.println("-----------------------------");
 		while (cacheIterator.hasNext())
 		{
 			entry = (Entry) cacheIterator.next();
 			System.out.println(entry.getKey() + ":" + entry.getValue());
 		}
 		System.out.println("-----------------------------");
 	}
 
 	/**
 	 * <pre>
 	 * </pre>
 	 * @param args
 	 * @throws IOException
 	 */
 	public static void main(String[] args) throws IOException
 	{
 		SingleCacheTest cacheTest = new SingleCacheTest();
 		BufferedReader inputReader = new BufferedReader(new InputStreamReader(System.in));
 		String line = "";
 		String[] command = null;
 		while ((line = inputReader.readLine()) != null)
 		{
 			command = line.split(" ");
 			if (command[0].equalsIgnoreCase("insert"))
 			{
 				cacheTest.addData();
 			}
 			else if (command[0].equalsIgnoreCase("addmap"))
 			{
 				cacheTest.addMap();
 			}
 			else if (command[0].equalsIgnoreCase("addlist"))
 			{
 				cacheTest.addList();
 			}
 			else if (command[0].equalsIgnoreCase("clear"))
 			{
 				cacheTest.clearData();
 			}
 			else if (command[0].equalsIgnoreCase("show"))
 			{
 				cacheTest.showData();
 			}
 			else if (command[0].equalsIgnoreCase("exit"))
 			{
 				break;
 			}
 		}
 	}
 }
 ///------------------------------tc-config.xml------------------------------//
 
 <?xml version="1.0" encoding="UTF-8"?>
 <con:tc-config xmlns:con="http://www.terracotta.org/config">
   <servers>
     <server host="%i" name="localhost">
       <dso-port>9510</dso-port>
       <jmx-port>9520</jmx-port>
       <data>terracotta/server-data</data>
       <logs>terracotta/server-logs</logs>
       <statistics>terracotta/cluster-statistics</statistics>
     </server>
     <update-check>
       <enabled>true</enabled>
     </update-check>
   </servers>
   <clients>
     <logs>terracotta/client-logs</logs>
     <statistics>terracotta/client-statistics/%D</statistics>
   </clients>
   <application>
     <dso>
       <instrumented-classes>
         <include>
           <class-expression>*..*</class-expression>
         </include>
       </instrumented-classes>
       <roots>
         <root>
           <field-name>com.zycus.utils.tc.cache.TerraCottaCache.internalCache</field-name>
         </root>
       </roots>
       <locks>
         <named-lock>
           <method-expression>void com.zycus.utils.tc.cache.TerraCottaCache.clear()</method-expression>
           <lock-level>write</lock-level>
           <lock-name>clear</lock-name>
         </named-lock>
         <named-lock>
           <method-expression>java.util.Map com.zycus.utils.tc.cache.TerraCottaCache.getMap()</method-expression>
           <lock-level>write</lock-level>
           <lock-name>getMap</lock-name>
         </named-lock>
         <named-lock>
           <method-expression>void com.zycus.utils.tc.cache.TerraCottaCache.put(java.lang.Object, java.lang.Object)</method-expression>
           <lock-level>write</lock-level>
           <lock-name>put</lock-name>
         </named-lock>
         <named-lock>
           <method-expression>java.lang.Object com.zycus.utils.tc.cache.TerraCottaCache.get(java.lang.Object)</method-expression>
           <lock-level>write</lock-level>
           <lock-name>get</lock-name>
         </named-lock>
         <named-lock>
           <method-expression>java.lang.Object com.zycus.utils.tc.cache.TerraCottaCache.remove(java.lang.Object)</method-expression>
           <lock-level>write</lock-level>
           <lock-name>remove</lock-name>
         </named-lock>
       </locks>
     </dso>
   </application>
 </con:tc-config>
 
 ///------------------------------STACK TRACE------------------------------//
 
 
 com.tc.object.tx.UnlockedSharedObjectException: 
 *******************************************************************************
 Attempt to access a shared object outside the scope of a shared lock.  
 All access to shared objects must be within the scope of one or more shared locks defined in your Terracotta configuration.  
 Please alter the locks section of your Terracotta configuration so that this access is auto-locked or protected by a named lock.
 
 For more information on this issue, please visit our Troubleshooting Guide at:
  http://terracotta.org/kit/troubleshooting
 
 
     Caused by Thread: main  in  VM(16)
     Shared Object Type: java.util.Vector
 *******************************************************************************
 
 	at com.tc.object.tx.ClientTransactionManagerImpl.getTransaction(ClientTransactionManagerImpl.java:300)
 	at com.tc.object.tx.ClientTransactionManagerImpl.checkWriteAccess(ClientTransactionManagerImpl.java:313)
 	at com.tc.object.bytecode.ManagerImpl.checkWriteAccess(ManagerImpl.java:697)
 	at com.tc.object.bytecode.ManagerUtil.checkWriteAccess(ManagerUtil.java:378)
 	at java.util.Vector.add(Vector.java)
 	at com.zycus.utils.tc.cache.test.SingleCacheTest.addList(SingleCacheTest.java:67)
 	at com.zycus.utils.tc.cache.test.SingleCacheTest.main(SingleCacheTest.java:146)
 Exception in thread "main" com.tc.object.tx.UnlockedSharedObjectException: 
 *******************************************************************************
 Attempt to access a shared object outside the scope of a shared lock.  
 All access to shared objects must be within the scope of one or more shared locks defined in your Terracotta configuration.  
 Please alter the locks section of your Terracotta configuration so that this access is auto-locked or protected by a named lock.
 
 For more information on this issue, please visit our Troubleshooting Guide at:
  http://terracotta.org/kit/troubleshooting
 
 
     Caused by Thread: main  in  VM(16)
     Shared Object Type: java.util.Vector
 *******************************************************************************
 
 	at com.tc.object.tx.ClientTransactionManagerImpl.getTransaction(ClientTransactionManagerImpl.java:300)
 	at com.tc.object.tx.ClientTransactionManagerImpl.checkWriteAccess(ClientTransactionManagerImpl.java:313)
 	at com.tc.object.bytecode.ManagerImpl.checkWriteAccess(ManagerImpl.java:697)
 	at com.tc.object.bytecode.ManagerUtil.checkWriteAccess(ManagerUtil.java:378)
 	at java.util.Vector.add(Vector.java)
 	at com.zycus.utils.tc.cache.test.SingleCacheTest.addList(SingleCacheTest.java:67)
 	at com.zycus.utils.tc.cache.test.SingleCacheTest.main(SingleCacheTest.java:146)

Hi Dhruv

The exception you are getting is because you are trying to modify an object that comes in your root's (com.zycus.utils.tc.cache.TerraCottaCache.internalCache) object graph without acquiring any locks.
You are trying to add a list/map as a value to the root map without acquiring locks in SingleCacheTest.addList and SingleCacheTest.addMap.
Any modifications in any shared object (a shared object is one which comes under the object graph of any root in Terracotta) needs to be done under the scope of a shared lock.

You missed out the following config in your tc-config:
Code:

         <named-lock>
           <method-expression>void com.zycus.utils.tc.cache.test.SingleCacheTest.addList()</method-expression>
           <lock-level>write</lock-level>
           <lock-name>addList</lock-name>
         </named-lock>
         <named-lock>
           <method-expression>void com.zycus.utils.tc.cache.test.SingleCacheTest.addMap()</method-expression>
           <lock-level>write</lock-level>
           <lock-name>addMap</lock-name>
         </named-lock>

Adding the above snippet in your tc-config should make it work.
You can find more information here
Hope you are finding Terracotta as exciting as we do.

Cheers

Thank You Abhishek,

i was looking for terracotta because of transparency in configuration.

but as you mention my all classes which uses package need to be configured in TC xml.

is there any alternative to achieve configuration transparency for clients.

You can use Annotations:

http://www.terracotta.org/web/display/docs/Annotations

or TIMs. "Transparency for clients" is kind of unclear. But Annotations will give you easier / clearer config that the developers can see and know is therefore going to invoke Terracotta behavior. TIMs allow libraries (jars, or what have you) to completely hide all the Terracotta-ness from the end user developer. Your library configuration need not reside inside the regular tc-config.xml that developers have access to and rely on.

--Ari

Thanks Taylor Gautier & ari ,

but its really surprising to me tht

TerraCotta is able to check that

DSO is being used by some method which is not present in my config file.

but why it cant lock by itself ???

is there any way to automatically lock DSO without changing code.

my basic requirement for using DSO is for holding big object (application specific)

and there are many codes and many methods updating object.

i cant define those all in "xml" and even cant set "Annotations" for same.

please suggest any solution for real transparency to client.

i hope there must be some solution to it.

and one more thing i didnt find any "tim-get.bat"

using terracotta 2.6.2

well,

when you say, "lock by itself" do you mean figure out where to place synchronized{} in your code? Or is your code pretty well synchronized and you want us to lock it all w/o any native Java locking going on in your code?

The first is easy...lock using a package expression and the autolock feature:
http://www.terracotta.org/web/display/docs/Concept+and+Architecture+Guide#ConceptandArchitectureGuide-locks

WARNING: it may not perform well since you will be doing lots of locking thru Terracotta that you might not need and you will have no choice but to make all locks write locks unless your development team uses some sort of naming convention for methods that get and objects that set values in shared objects (eg: getName() or setName()).

If you want the latter, I hate to say this but it doesn't exist. There is no product that infers concurrency model from the class files on disk and inserts the proper synchronization logic that I know of. But, yes, that would be an AWESOME feature.

--Ari

--Ari

My Root is HashMap(DSO)

i am removing object from HashMap

and when i try to update it ,

its throwing error

once the object is removed from ROOT

any updation to object in any method should not throw exception !!

but it is throing exception..

ahh I see. this point is discussed in detail in the concept and architecture guide on locks. please read the whole section:

http://www.terracotta.org/web/display/docs/Concept+and+Architecture+Guide#ConceptandArchitectureGuide-Locks

hi,

any change in tc-config.xml require to recreate

boot.jar

or once boot.jar is created for specific JVM works fine with config file ??

Most changes do not require a change in the boot-jar. Only things that affect the boot jar - e.g. core java classes.

For example:

1) updating the additional-boot-jar-classes entry
2) updating locking for java classes

where i can find what changes makes creating new boot.jar

what if i add many funcions entry for locking ??

There's no doc that I am aware of that lists the changes explicitly. We will fix that.

I am updating my previous message to be more clear:

Most changes do not require a change in the boot-jar. Only things that affect the boot jar - e.g. locks that affect core java language classes (e.g. java.util.Hashtable).

For example:

1) updating the additional-boot-jar-classes entry
2) updating locking for java lang classes - e.g. java.util.Hashtable (not application classes)

so you mean to say that
if i configure tc-config.xml for my core caching API

and create boot.jar using eclipse tool for specific JVM

now when client code use this boot.jar
and add new methods entry in tc-config.xml

do i need to create boot.jar again in this case

my all new methods are application or client code specific.

No, the boot jar is for core Java classes, not your application classes.