org.jboss.cache.loader
Class SharedStoreCacheLoader

java.lang.Object
  |
  +--org.jboss.cache.AbstractTreeCacheListener
        |
        +--org.jboss.cache.loader.SharedStoreCacheLoader

All Implemented Interfaces:

CacheLoader, ExtendedTreeCacheListener, org.jboss.system.Service, TreeCacheListener

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 1.4 2005/08/25 19:54:58 hmesha 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) Commit the transaction.
void	create()
void	destroy()
boolean	exists(Fqn name) Checks whether the CacheLoader has a node with Fqn
java.util.Map	get(Fqn name) Returns all keys and values from the persistent store, given a fully qualified name
java.lang.Object	get(Fqn name, java.lang.Object key) Returns the value for a given key.
java.util.Set	getChildrenNames(Fqn fqn) Returns a list of children names, all names are relative.
byte[]	loadEntireState() Fetch the entire state for this cache from secondary storage (disk, DB) and return 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) Prepare the modifications.
void	put(Fqn name, java.util.Map attributes) Inserts all elements of attributes into the attributes hashmap of the given node, overwriting existing attributes, but not clearing the existing hashmap before insertion (making it a union of existing and new attributes) If the node does not exist, all parent nodes from the root down are created automatically
java.lang.Object	put(Fqn name, java.lang.Object key, java.lang.Object value) Inserts key and value into the attributes hashmap of the given node.
void	put(java.util.List modifications) Inserts all modifications to the backend store.
void	remove(Fqn name) Removes the given node.
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
void	rollback(java.lang.Object tx) Roll the transaction back.
void	setCache(TreeCache c) This method allows the CacheLoader to set the TreeCache, therefore allowing the CacheLoader to invoke methods of the TreeCache.
void	setConfig(java.util.Properties props) Sets the configuration.
void	start()
void	stop()
void	storeEntireState(byte[] state) Store 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

Parameters:

fqn -

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

Parameters:

fqn -

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

Parameters:

fqn -

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

Parameters:

fqn -

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

Parameters:

fqn -

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

Parameters:

cache -

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

Parameters:

cache -

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. Will be called before Service.create() and Service.start()

Specified by:

setConfig in interface CacheLoader

Parameters:

props - A list of properties, defined in the XML file

setCache

public void setCache(TreeCache c)

Description copied from interface: CacheLoader

This method allows the CacheLoader to set the TreeCache, therefore allowing the CacheLoader to invoke methods of the TreeCache. It can also use the TreeCache to fetch configuration information. Alternatively, the CacheLoader could maintain its own configuration
This method will be called directly after the CacheLoader instance has been created

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 list of children names, all names are relative. Returns null if the parent node is not found. The returned set must not be modified, e.g. use Collections.unmodifiableSet(s) to return the result

Specified by:

getChildrenNames in interface CacheLoader

Parameters:

fqn - The FQN of the parent

Returns:

Set. A list of children. Returns null if no children nodes are present, or the parent is not present

java.lang.Exception

get

public java.lang.Object get(Fqn name,
                            java.lang.Object key)
                     throws java.lang.Exception

Description copied from interface: CacheLoader

Returns the value for a given key. Returns null if the node doesn't exist, or the value is not bound

Specified by:

get in interface CacheLoader

Parameters:

name -

Returns:

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

Specified by:

get in interface CacheLoader

Parameters:

name -

Returns:

Map of keys and values for the given node. Returns null if the node was not found, or if the node has no attributes

Throws:

java.lang.Exception

exists

public boolean exists(Fqn name)
               throws java.lang.Exception

Description copied from interface: CacheLoader

Checks whether the CacheLoader has a node with Fqn

Specified by:

exists in interface CacheLoader

Parameters:

name -

Returns:

True if node exists, false otherwise

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

Inserts key and value into the attributes hashmap of the 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

java.lang.Exception

put

public void put(Fqn name,
                java.util.Map attributes)
         throws java.lang.Exception

Description copied from interface: CacheLoader

Inserts all elements of attributes into the attributes hashmap of the given node, overwriting existing attributes, but not clearing the existing hashmap before insertion (making it a union of existing and new attributes) 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

java.lang.Exception

put

public void put(java.util.List modifications)
         throws java.lang.Exception

Description copied from interface: CacheLoader

Inserts all modifications to the backend store. Overwrite whatever is already in the datastore.

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. No-op if node doesn't exist

Specified by:

remove in interface CacheLoader

java.lang.Exception

remove

public void remove(Fqn name)
            throws java.lang.Exception

Description copied from interface: CacheLoader

Removes the given node. If the node is the root of a subtree, this will recursively remove all subnodes, depth-first

Specified by:

remove in interface CacheLoader

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

Specified by:

removeData in interface CacheLoader

Parameters:

name -

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

Prepare the 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

Commit 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 -

java.lang.Exception

rollback

public void rollback(java.lang.Object tx)

Description copied from interface: CacheLoader

Roll 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 -

loadEntireState

public byte[] loadEntireState()
                       throws java.lang.Exception

Description copied from interface: CacheLoader

Fetch the entire state for this cache from secondary storage (disk, DB) and return it as a byte buffer. This is for initialization of a new cache from a remote cache. The new cache would then call storeEntireState().
todo: define binary format for exchanging state

Specified by:

loadEntireState in interface CacheLoader

java.lang.Exception

storeEntireState

public void storeEntireState(byte[] state)
                      throws java.lang.Exception

Description copied from interface: CacheLoader

Store the given state in secondary storage. Overwrite whatever is currently in seconday storage.

Specified by:

storeEntireState in interface CacheLoader

java.lang.Exception

create

public void create()
            throws java.lang.Exception

Specified by:

create in interface org.jboss.system.Service

java.lang.Exception

start

public void start()
           throws java.lang.Exception

Specified by:

start in interface org.jboss.system.Service

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