org.jboss.cache.loader
Class SharedStoreCacheLoader

java.lang.Object
  extended by org.jboss.cache.AbstractTreeCacheListener
      extended by org.jboss.cache.loader.SharedStoreCacheLoader
All Implemented Interfaces:
ExtendedTreeCacheListener, CacheLoader, TreeCacheListener, org.jboss.system.Service

public class SharedStoreCacheLoader
extends AbstractTreeCacheListener
implements CacheLoader

CacheLoader proxy used only when multiple CacheLoaders in a cluster access the same underlying store (e.g. a shared filesystem, or DB). SharedStoreCacheLoader is a simply facade to a real CacheLoader implementation. It always delegates reads to the real CacheLoader. Writes are forwarded only if this SharedStoreCacheLoader is currently the cordinator. This avoid having all CacheLoaders in a cluster writing the same data to the same underlying store. Although not incorrect (e.g. a DB will just discard additional INSERTs for the same key, and throw an exception), this will avoid a lot of redundant work.
Whenever the current coordinator dies (or leaves), the second in line will take over. That SharedStoreCacheLoader will then pass writes through to its underlying CacheLoader.

Version:
$Id: SharedStoreCacheLoader.java,v 1.6 2006/04/08 20:30:08 genman Exp $
Author:
Bela Ban

Constructor Summary
SharedStoreCacheLoader(CacheLoader loader, org.jgroups.Address local_addr, boolean coordinator)
           
 
Method Summary
 void cacheStarted(TreeCache cache)
          Called when the cache is started.
 void cacheStopped(TreeCache cache)
          Called when the cache is stopped.
 void commit(java.lang.Object tx)
          Commits the transaction.
 void create()
           
 void destroy()
           
 boolean exists(Fqn name)
          Returns true if the CacheLoader has a node with a Fqn.
 java.util.Map get(Fqn name)
          Returns all keys and values from the persistent store, given a fully qualified name.
 java.util.Set getChildrenNames(Fqn fqn)
          Returns a set of children node names as Strings.
 byte[] loadEntireState()
          Fetches the entire state for this cache from secondary storage (disk, DB) and returns it as a byte buffer.
 void nodeCreated(Fqn fqn)
          Called when a node is created
 void nodeEvicted(Fqn fqn)
          Called when a node is evicted (not the same as remove()).
 void nodeLoaded(Fqn fqn)
          Called when a node is loaded into memory via the CacheLoader.
 void nodeModified(Fqn fqn)
          Called when a node is modified, e.g., one (key, value) pair in the internal map storage has been modified.
 void nodeRemoved(Fqn fqn)
          Called when a node is removed.
 void nodeVisited(Fqn fqn)
          Called when a node is visisted, i.e., get().
 void prepare(java.lang.Object tx, java.util.List modifications, boolean one_phase)
          Prepares a list of modifications.
 void put(Fqn name, java.util.Map attributes)
          Puts all entries of the map into the existing map of the given node, overwriting existing keys, but not clearing the existing map before insertion.
 java.lang.Object put(Fqn name, java.lang.Object key, java.lang.Object value)
          Puts a key and value into the attribute map of a given node.
 void put(java.util.List modifications)
          Applies all modifications to the backend store.
 void remove(Fqn name)
          Removes the given node and all its subnodes.
 java.lang.Object remove(Fqn name, java.lang.Object key)
          Removes the given key and value from the attributes of the given node.
 void removeData(Fqn name)
          Removes all attributes from a given node, but doesn't delete the node itself or any subnodes.
 void rollback(java.lang.Object tx)
          Rolls the transaction back.
 void setCache(TreeCache c)
          Sets the TreeCache that is maintaining this CacheLoader.
 void setConfig(java.util.Properties props)
          Sets the configuration.
 void start()
           
 void stop()
           
 void storeEntireState(byte[] state)
          Stores the given state in secondary storage.
 void viewChange(org.jgroups.View new_view)
           
 
Methods inherited from class org.jboss.cache.AbstractTreeCacheListener
nodeActivate, nodeEvict, nodeModify, nodePassivate, nodeRemove
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

SharedStoreCacheLoader

public SharedStoreCacheLoader(CacheLoader loader,
                              org.jgroups.Address local_addr,
                              boolean coordinator)
Method Detail

nodeCreated

public void nodeCreated(Fqn fqn)
Description copied from interface: TreeCacheListener
Called when a node is created

Specified by:
nodeCreated in interface TreeCacheListener
Overrides:
nodeCreated in class AbstractTreeCacheListener

nodeRemoved

public void nodeRemoved(Fqn fqn)
Description copied from interface: TreeCacheListener
Called when a node is removed.

Specified by:
nodeRemoved in interface TreeCacheListener
Overrides:
nodeRemoved in class AbstractTreeCacheListener

nodeLoaded

public void nodeLoaded(Fqn fqn)
Description copied from interface: TreeCacheListener
Called when a node is loaded into memory via the CacheLoader. This is not the same as TreeCacheListener.nodeCreated(Fqn).

Specified by:
nodeLoaded in interface TreeCacheListener
Overrides:
nodeLoaded in class AbstractTreeCacheListener

nodeEvicted

public void nodeEvicted(Fqn fqn)
Description copied from interface: TreeCacheListener
Called when a node is evicted (not the same as remove()).

Specified by:
nodeEvicted in interface TreeCacheListener
Overrides:
nodeEvicted in class AbstractTreeCacheListener

nodeModified

public void nodeModified(Fqn fqn)
Description copied from interface: TreeCacheListener
Called when a node is modified, e.g., one (key, value) pair in the internal map storage has been modified.

Specified by:
nodeModified in interface TreeCacheListener
Overrides:
nodeModified in class AbstractTreeCacheListener

nodeVisited

public void nodeVisited(Fqn fqn)
Description copied from interface: TreeCacheListener
Called when a node is visisted, i.e., get().

Specified by:
nodeVisited in interface TreeCacheListener
Overrides:
nodeVisited in class AbstractTreeCacheListener

cacheStarted

public void cacheStarted(TreeCache cache)
Description copied from interface: TreeCacheListener
Called when the cache is started.

Specified by:
cacheStarted in interface TreeCacheListener
Overrides:
cacheStarted in class AbstractTreeCacheListener

cacheStopped

public void cacheStopped(TreeCache cache)
Description copied from interface: TreeCacheListener
Called when the cache is stopped.

Specified by:
cacheStopped in interface TreeCacheListener
Overrides:
cacheStopped in class AbstractTreeCacheListener

viewChange

public void viewChange(org.jgroups.View new_view)
Specified by:
viewChange in interface TreeCacheListener
Overrides:
viewChange in class AbstractTreeCacheListener

setConfig

public void setConfig(java.util.Properties props)
Description copied from interface: CacheLoader
Sets the configuration. This is called before Service.create() and Service.start().

Specified by:
setConfig in interface CacheLoader
Parameters:
props - a collection of configuration properties

setCache

public void setCache(TreeCache c)
Description copied from interface: CacheLoader
Sets the TreeCache that is maintaining this CacheLoader. This method allows this CacheLoader to invoke methods on TreeCache, including fetching additional configuration information. This method is called be called after the CacheLoader instance has been constructed.

Specified by:
setCache in interface CacheLoader
Parameters:
c - The cache on which this loader works

getChildrenNames

public java.util.Set getChildrenNames(Fqn fqn)
                               throws java.lang.Exception
Description copied from interface: CacheLoader
Returns a set of children node names as Strings. All names are relative to this parent Fqn. Returns null if the named node is not found or there are no children. The returned set must not be modifiable. Implementors can use Collections.unmodifiableSet(Set) to make the set unmodifiable.

Specified by:
getChildrenNames in interface CacheLoader
Parameters:
fqn - The FQN of the parent
Returns:
Set a set of children. Returns null if no children nodes are present, or the parent is not present
Throws:
java.lang.Exception

get

public java.util.Map get(Fqn name)
                  throws java.lang.Exception
Description copied from interface: CacheLoader
Returns all keys and values from the persistent store, given a fully qualified name. NOTE that the expected return value of this method has changed from JBossCache 1.2.x and before! This will affect cache loaders written prior to JBossCache 1.3.0 and such implementations should be checked for compliance with the behaviour expected.

Specified by:
get in interface CacheLoader
Returns:
Map keys and values for the given node. Returns null if the node is not found. If the node is found but has no attributes, this method returns an empty Map.
Throws:
java.lang.Exception

exists

public boolean exists(Fqn name)
               throws java.lang.Exception
Description copied from interface: CacheLoader
Returns true if the CacheLoader has a node with a Fqn.

Specified by:
exists in interface CacheLoader
Returns:
true if node exists, false otherwise
Throws:
java.lang.Exception

put

public java.lang.Object put(Fqn name,
                            java.lang.Object key,
                            java.lang.Object value)
                     throws java.lang.Exception
Description copied from interface: CacheLoader
Puts a key and value into the attribute map of a given node. If the node does not exist, all parent nodes from the root down are created automatically. Returns the old value.

Specified by:
put in interface CacheLoader
Throws:
java.lang.Exception

put

public void put(Fqn name,
                java.util.Map attributes)
         throws java.lang.Exception
Description copied from interface: CacheLoader
Puts all entries of the map into the existing map of the given node, overwriting existing keys, but not clearing the existing map before insertion. This is the same behavior as Map.putAll(java.util.Map). If the node does not exist, all parent nodes from the root down are created automatically

Specified by:
put in interface CacheLoader
Parameters:
name - The fully qualified name of the node
attributes - A Map of attributes. Can be null
Throws:
java.lang.Exception

put

public void put(java.util.List modifications)
         throws java.lang.Exception
Description copied from interface: CacheLoader
Applies all modifications to the backend store. Changes may be applied in a single operation.

Specified by:
put in interface CacheLoader
Parameters:
modifications - A List of modifications
Throws:
java.lang.Exception

remove

public java.lang.Object remove(Fqn name,
                               java.lang.Object key)
                        throws java.lang.Exception
Description copied from interface: CacheLoader
Removes the given key and value from the attributes of the given node. Does nothing if the node doesn't exist Returns the removed value.

Specified by:
remove in interface CacheLoader
Throws:
java.lang.Exception

remove

public void remove(Fqn name)
            throws java.lang.Exception
Description copied from interface: CacheLoader
Removes the given node and all its subnodes.

Specified by:
remove in interface CacheLoader
Throws:
java.lang.Exception

removeData

public void removeData(Fqn name)
                throws java.lang.Exception
Description copied from interface: CacheLoader
Removes all attributes from a given node, but doesn't delete the node itself or any subnodes.

Specified by:
removeData in interface CacheLoader
Throws:
java.lang.Exception

prepare

public void prepare(java.lang.Object tx,
                    java.util.List modifications,
                    boolean one_phase)
             throws java.lang.Exception
Description copied from interface: CacheLoader
Prepares a list of modifications. For example, for a DB-based CacheLoader:
  1. Create a local (JDBC) transaction
  2. Associate the local transaction with tx (tx is the key)
  3. Execute the coresponding SQL statements against the DB (statements derived from modifications)
For non-transactional CacheLoader (e.g. file-based), this could be a null operation.

Specified by:
prepare in interface CacheLoader
Parameters:
tx - The transaction, just used as a hashmap key
modifications - List, a list of all modifications within the given transaction
one_phase - Persist immediately and (for example) commit the local JDBC transaction as well. When true, we won't get a CacheLoader.commit(Object) or CacheLoader.rollback(Object) method call later
Throws:
java.lang.Exception

commit

public void commit(java.lang.Object tx)
            throws java.lang.Exception
Description copied from interface: CacheLoader
Commits the transaction. A DB-based CacheLoader would look up the local JDBC transaction asociated with tx and commit that transaction. Non-transactional CacheLoaders could simply write the data that was previously saved transiently under the given tx key, to (for example) a file system (note this only holds if the previous prepare() did not define one_phase=true

Specified by:
commit in interface CacheLoader
Parameters:
tx - transaction to commit
Throws:
java.lang.Exception

rollback

public void rollback(java.lang.Object tx)
Description copied from interface: CacheLoader
Rolls the transaction back. A DB-based CacheLoader would look up the local JDBC transaction asociated with tx and roll back that transaction.

Specified by:
rollback in interface CacheLoader
Parameters:
tx - transaction to roll back

loadEntireState

public byte[] loadEntireState()
                       throws java.lang.Exception
Description copied from interface: CacheLoader
Fetches the entire state for this cache from secondary storage (disk, DB) and returns it as a byte buffer. This is for initialization of a new cache from a remote cache. The new cache would then call CacheLoader.storeEntireState(byte[]).

Specified by:
loadEntireState in interface CacheLoader
Throws:
java.lang.Exception

storeEntireState

public void storeEntireState(byte[] state)
                      throws java.lang.Exception
Description copied from interface: CacheLoader
Stores the given state in secondary storage. Overwrites whatever is currently in storage.

Specified by:
storeEntireState in interface CacheLoader
Throws:
java.lang.Exception

create

public void create()
            throws java.lang.Exception
Specified by:
create in interface org.jboss.system.Service
Throws:
java.lang.Exception

start

public void start()
           throws java.lang.Exception
Specified by:
start in interface org.jboss.system.Service
Throws:
java.lang.Exception

stop

public void stop()
Specified by:
stop in interface org.jboss.system.Service

destroy

public void destroy()
Specified by:
destroy in interface org.jboss.system.Service


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