org.jboss.cache.loader
Class SingletonStoreCacheLoader

java.lang.Object
  org.jboss.cache.loader.AbstractCacheLoader
      org.jboss.cache.loader.AbstractDelegatingCacheLoader
          org.jboss.cache.loader.SingletonStoreCacheLoader

All Implemented Interfaces:

CacheLoader

public class SingletonStoreCacheLoader
extends AbstractDelegatingCacheLoader

SingletonStoreCacheLoader is a delegating cache loader used for situations when only one node should interact with the underlying store. The coordinator of the cluster will be responsible for the underlying CacheLoader. SingletonStoreCacheLoader is a simply facade to a real CacheLoader implementation. It always delegates reads to the real CacheLoader.

Writes are forwarded only if this SingletonStoreCacheLoader 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 SingletonStoreCacheLoader will then pass writes through to its underlying CacheLoader. Optionally, when a new coordinator takes over the Singleton, it can push the in-memory state to the cache cacheLoader.

Author:

Bela Ban, Galder Zamarreno

Nested Class Summary

class

SingletonStoreCacheLoader.SingletonStoreListener Cache listener that reacts to cluster topology changes to find out whether a new coordinator is elected.

Field Summary

Fields inherited from class org.jboss.cache.loader.AbstractCacheLoader

cache, regionManager

Constructor Summary

SingletonStoreCacheLoader(CacheLoader cacheLoader, boolean pushConfiguration)

Method Summary

protected void	activeStatusChanged(boolean newActiveState)
void	commit(java.lang.Object tx) Commits the transaction.
protected java.lang.Thread	createPushStateThread()
java.lang.Object	getCacheListener()
java.lang.Thread	getPushStateThread()
void	prepare(java.lang.Object tx, java.util.List<Modification> 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<Modification> modifications) Applies all modifications to the backend store.
void	remove(Fqn fqn) Removes the given node and all its subnodes, does nothing if the node does not exist.
java.lang.Object	remove(Fqn fqn, java.lang.Object key) Removes the given key and value from the attributes of the given node.
void	removeData(Fqn fqn) 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	storeEntireState(java.io.ObjectInputStream is) Stores the entire state for this cache by reading it from a provided ObjectInputStream.
void	storeState(Fqn subtree, java.io.ObjectInputStream is) Stores the given portion of the cache tree's state in secondary storage.
java.lang.String	toString()

Methods inherited from class org.jboss.cache.loader.AbstractDelegatingCacheLoader

create, destroy, exists, get, getCacheLoader, getChildrenNames, getConfig, loadEntireState, loadState, setCache, setCacheLoader, setConfig, setRegionManager, start, stop

Methods inherited from class org.jboss.cache.loader.AbstractCacheLoader

getMarshaller, getNodeDataList, loadStateHelper, put

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

SingletonStoreCacheLoader

public SingletonStoreCacheLoader(CacheLoader cacheLoader,
                                 boolean pushConfiguration)

Method Detail

getCacheListener

public java.lang.Object getCacheListener()

activeStatusChanged

protected void activeStatusChanged(boolean newActiveState)

createPushStateThread

protected java.lang.Thread createPushStateThread()

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

Overrides:

put in class AbstractDelegatingCacheLoader

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

Overrides:

put in class AbstractDelegatingCacheLoader

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<Modification> 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

Overrides:

put in class AbstractDelegatingCacheLoader

Parameters:

modifications - A List of modifications

Throws:

java.lang.Exception

remove

public java.lang.Object remove(Fqn fqn,
                               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

Overrides:

remove in class AbstractDelegatingCacheLoader

Throws:

java.lang.Exception

remove

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

Description copied from interface: CacheLoader

Removes the given node and all its subnodes, does nothing if the node does not exist.

Specified by:

remove in interface CacheLoader

Overrides:

remove in class AbstractDelegatingCacheLoader

Parameters:

fqn - the Fqn of the node

Throws:

java.lang.Exception

removeData

public void removeData(Fqn fqn)
                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

Overrides:

removeData in class AbstractDelegatingCacheLoader

Parameters:

fqn - the Fqn of the node

Throws:

java.lang.Exception

prepare

public void prepare(java.lang.Object tx,
                    java.util.List<Modification> 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 corresponding SQL statements against the DB (statements derived from modifications)

For non-transactional CacheLoader (e.g. file-based), the implementation could attempt to implement it's own transactional logic, attempting to write data to a temp location (or memory) and writing it to the proper location upon commit.

Specified by:

prepare in interface CacheLoader

Overrides:

prepare in class AbstractDelegatingCacheLoader

Parameters:

tx - The transaction, indended to be used by implementations as an identifier of the transaction (and not necessarily a JTA Transaction object)

modifications - A List containing Modifications, for 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

Overrides:

commit in class AbstractDelegatingCacheLoader

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

Overrides:

rollback in class AbstractDelegatingCacheLoader

Parameters:

tx - transaction to roll back

storeEntireState

public void storeEntireState(java.io.ObjectInputStream is)
                      throws java.lang.Exception

Description copied from interface: CacheLoader

Stores the entire state for this cache by reading it from a provided ObjectInputStream. The state was provided to this cache by calling CacheLoader.loadEntireState(ObjectOutputStream)} on some other cache instance. State currently in storage gets overwritten.

Implementations of this method should not catch any exception or close the given ObjectInputStream parameter. In order to ensure cacheloader interoperability contents of the cache are read from the ObjectInputStream as a sequence of NodeData objects.

Default implementation is provided by AbstractCacheLoader and ensures cacheloader interoperability. Implementors are encouraged to consider extending AbstractCacheLoader prior to implementing completely custom cacheloader.

Specified by:

storeEntireState in interface CacheLoader

Overrides:

storeEntireState in class AbstractDelegatingCacheLoader

Parameters:

is - ObjectInputStream to read state

Throws:

java.lang.Exception

See Also:

AbstractCacheLoader.storeEntireState(ObjectInputStream), NodeData

storeState

public void storeState(Fqn subtree,
                       java.io.ObjectInputStream is)
                throws java.lang.Exception

Description copied from interface: CacheLoader

Stores the given portion of the cache tree's state in secondary storage. Overwrite whatever is currently in secondary storage. If the transferred state has Fqns equal to or children of parameter subtree, then no special behavior is required. Otherwise, ensure that the state is integrated under the given subtree. Typically in the latter case subtree would be the Fqn of the buddy backup region for a buddy group; e.g.

If the the transferred state had Fqns starting with "/a" and subtree was "/_BUDDY_BACKUP_/192.168.1.2:5555" then the state should be stored in the local persistent store under "/_BUDDY_BACKUP_/192.168.1.2:5555/a"

Implementations of this method should not catch any exception or close the given ObjectInputStream parameter. In order to ensure cacheloader interoperability contents of the cache are read from the ObjectInputStream as a sequence of NodeData objects.

Default implementation is provided by AbstractCacheLoader and ensures cacheloader interoperability. Implementors are encouraged to consider extending AbstractCacheLoader prior to implementing completely custom cacheloader.

Specified by:

storeState in interface CacheLoader

Overrides:

storeState in class AbstractDelegatingCacheLoader

Parameters:

subtree - Fqn naming the root (i.e. highest level parent) node of the subtree included in state. If the Fqns of the data included in state are not already children of subtree, then their Fqns should be altered to make them children of subtree before they are persisted.

is - ObjectInputStream to read state

Throws:

java.lang.Exception

See Also:

AbstractCacheLoader.storeState(Fqn,ObjectInputStream), NodeData

getPushStateThread

public java.lang.Thread getPushStateThread()

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object