Package org.jppf.load.balancer.persistence

Class FileLoadBalancerPersistence

java.lang.Object

org.jppf.persistence.AbstractFilePersistence<LoadBalancerPersistenceInfo,LoadBalancerPersistenceException>

org.jppf.load.balancer.persistence.FileLoadBalancerPersistence

All Implemented Interfaces:

LoadBalancerPersistence

public class FileLoadBalancerPersistence
extends AbstractFilePersistence<LoadBalancerPersistenceInfo,LoadBalancerPersistenceException>
implements LoadBalancerPersistence

File-based persistence implementation for the state of the JPPF load-balancers. It relies on a directory structure is as follows:

 persistence_root
 |_channel_identifier1
 | |_algorithm1.data
 | |_...
 | |_algorithmP1.data
 |_...
 |_channel_identifiern
   |_algorithm1.data
   |_...
   |_algorithmPn.data

Where:

• Each channel_identifieri represents a hash of a string concatenated from various properties of the channel. A channel represents a connection between a node and a driver for server-side load-balancing, or between a driver and a client for client-side load-balancing. This id is unique for each channel and resilient over restarts of both related peers, contrary to their uuids, which are recreated each time a component starts. Using a hash also ensures that it can be used a s a valid folder name in a file system
• Each algorithmi prefix is the hash of the related load-balancing algorithm name. Again, it ensures it can be used to form a valid file name
• Each algorithmi.data file represents the serialized state of the related load-balancer

Since:

6.0

Author:

Laurent Cohen

Nested Class Summary

Nested classes/interfaces inherited from class org.jppf.persistence.AbstractFilePersistence

AbstractFilePersistence.DirectoryFilter

Field Summary

Fields

Modifier and Type	Field	Description
static final String	DEFAULT_ROOT	The default root path if none is specified.

Fields inherited from class org.jppf.persistence.AbstractFilePersistence

DEFAULT_EXTENSION, rootPath, TEMP_EXTENSION

Constructor Summary

Constructors

Constructor	Description
FileLoadBalancerPersistence()	Initialize this persistence with the root path DEFAULT_ROOT under the current user directory.
FileLoadBalancerPersistence(String... paths)	Initialize this persistence with the specified path as root directory.

Method Summary

Modifier and Type	Method	Description
protected LoadBalancerPersistenceException	convertException(Exception e)	Create the appropriate type of exception.
void	delete(LoadBalancerPersistenceInfo info)	Delete the specified load-balancer state(s) from the persistence store.
int	getUncompletedOperations()	Get the number of persistence operations, including load, store, delete and list, that have started but not yet completed.
List<String>	list(LoadBalancerPersistenceInfo info)	List all entries in the persistence store.
Object	load(LoadBalancerPersistenceInfo info)	Load the state of a load balancer from the persistence sstore.
void	store(LoadBalancerPersistenceInfo info)	Store a load balancer to the persistence sstore.

Methods inherited from class org.jppf.persistence.AbstractFilePersistence

checkDirectory, deleteIfEmpty, getSubDir, isSameFile, pathname, toString

Methods inherited from class java.lang.Object

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

Field Details

DEFAULT_ROOT

public static final String DEFAULT_ROOT

The default root path if none is specified.

See Also:

• Constant Field Values

Constructor Details

FileLoadBalancerPersistence

public FileLoadBalancerPersistence()

Initialize this persistence with the root path DEFAULT_ROOT under the current user directory.

FileLoadBalancerPersistence

public FileLoadBalancerPersistence(String... paths)

Initialize this persistence with the specified path as root directory.

Parameters:

paths - the root directory for this persistence.

Method Details

store

public void store(LoadBalancerPersistenceInfo info)
           throws LoadBalancerPersistenceException

Description copied from interface: LoadBalancerPersistence

Store a load balancer to the persistence sstore.

Specified by:

store in interface LoadBalancerPersistence

Parameters:

info - a LoadBalancerPersistenceInfo object representing the load balancer and its state.

Throws:

LoadBalancerPersistenceException - if any erorr occurs during the persistence operation.

load

public Object load(LoadBalancerPersistenceInfo info)
            throws LoadBalancerPersistenceException

Description copied from interface: LoadBalancerPersistence

Load the state of a load balancer from the persistence sstore.

Specified by:

load in interface LoadBalancerPersistence

Parameters:

info - a LoadBalancerPersistenceInfo object representing the load balancer and its state.

Returns:

an object representing the load balancer state, or null if no entry exists in the persistence store for the specified node identifier.

Throws:

LoadBalancerPersistenceException - if any erorr occurs during the persistence operation.

delete

public void delete(LoadBalancerPersistenceInfo info)
            throws LoadBalancerPersistenceException

Description copied from interface: LoadBalancerPersistence

Delete the specified load-balancer state(s) from the persistence store.

The info parameter embeds both the scope and identifiers for the artifacts to delete:

• if info is null or both info.getChannelID() and info.getAlgorithmID() are null, then all entries in the persistence store are deleted
• if only info.getAlgorithmID() is null, then the states of all algorithm for the specified channel are deleted
• if only info.getChannelID() is null, then the states of the specified algorithm are deleted for all the channels
• if neither info.getChannelID() nor info.getAlgorithmID() are null, then only the state of the specified algorithm for the specified channel is deleted

Specified by:

delete in interface LoadBalancerPersistence

Parameters:

info - encapsulates information about the artifacts to delete.

Throws:

LoadBalancerPersistenceException - if any erorr occurs during the persistence operation.

list

public List<String> list(LoadBalancerPersistenceInfo info)
                  throws LoadBalancerPersistenceException

Description copied from interface: LoadBalancerPersistence

List all entries in the persistence store.

The info parameter embeds both the scope and identifiers for the artifacts to list:

• if info is null or both info.getChannelID() and info.getAlgorithmID() are null, then all channelIDs in the persistence store are returned
• if only info.getAlgorithmID() is null, then all the algorithm IDs for the specified channel are returned
• if only info.getChannelID() is null, then the the IDs of the channels that have a persisted state for the algorithm are returned
• if neither info.getChannelID() nor info.getAlgorithmID() are null, then the specified algorithmID is returned (list with a single entry) if the specified channel has an entry for it, otherwise an empty list must be returned

Specified by:

list in interface LoadBalancerPersistence

Parameters:

info - encapsulates information about the artifacts to delete.

Returns:

a list of nodeIDs or algorithmIDs, depending on the input parameter.

Throws:

LoadBalancerPersistenceException - if any erorr occurs during the persistence operation.

convertException

protected LoadBalancerPersistenceException convertException(Exception e)

Description copied from class: AbstractFilePersistence

Create the appropriate type of exception.

Specified by:

convertException in class AbstractFilePersistence<LoadBalancerPersistenceInfo,LoadBalancerPersistenceException>

Parameters:

e - the actual exception from which to create the new one.

Returns:

an exception of type E.

getUncompletedOperations

public int getUncompletedOperations()

Description copied from interface: LoadBalancerPersistence

Get the number of persistence operations, including load, store, delete and list, that have started but not yet completed.

Specified by:

getUncompletedOperations in interface LoadBalancerPersistence

Returns:

the number of uncompleted operations.