org.adroitlogic.x.clustering.failover.strategy

Class FailoverStrategy<T extends FailoverClusterPaths>

java.lang.Object

org.adroitlogic.x.clustering.failover.strategy.FailoverStrategy<T>

Type Parameters:

T - Type of the FailoverClusterPaths instance used by the extending class

All Implemented Interfaces:

org.apache.curator.framework.state.ConnectionStateListener

Direct Known Subclasses:

GroupFailoverStrategy, NodeWiseFailoverStrategy

public abstract class FailoverStrategy<T extends FailoverClusterPaths>
extends Object
implements org.apache.curator.framework.state.ConnectionStateListener

This is the abstract class representing a failover strategy. Any class willing to implement a new strategy to provide failover should extend from this class. Each failover strategy should have an associated FailoverClusterPaths instance which is to be used as the ZNode structure for the given strategy.

This class also listens for connection state changes too. Whenever the connection gets disconnected, this class will take actions to reset the tags put into the XEnvironment by the child class.

Since:

17.01

Author:

Imesha Sudasingha

Field Summary

Fields

Modifier and Type	Field and Description
protected org.apache.curator.framework.CuratorFramework	client
protected XEnvironment	environment
protected T	failoverClusterPaths
protected Logger	logger
protected Status	status

Constructor Summary

Constructors

Constructor and Description
FailoverStrategy()

Method Summary

Modifier and Type	Method and Description
protected void	addTags(XTag... tags) Adds a set of XTags to the XEnvironment.
T	getFailoverClusterPaths()
abstract Map<String,?>	getFailoverMatrix()
void	initialize(org.apache.curator.framework.CuratorFramework client, ClusterPaths clusterPaths)
protected abstract void	initStrategy()
protected abstract T	newFailoverClusterPaths()
protected abstract void	refresh() This method is called whenever the failover strategy believes that the connection state became unstable and again re became stable.
protected void	removeTags(XTag... tags) Removes a set of tags from the XEnvironment.
protected abstract void	resetTags() Whenever the connection state changes to lost or suspended, this method will be called in order to remove the tags added by the extending concrete strategy.
void	start()
protected abstract void	startStrategy()
void	stateChanged(org.apache.curator.framework.CuratorFramework client, org.apache.curator.framework.state.ConnectionState newState)
void	stop()
protected abstract void	stopStrategy()
abstract String	toString()

Methods inherited from class java.lang.Object

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

Field Detail

logger

protected final Logger logger

environment

@Autowired
protected XEnvironment environment

status

protected Status status

failoverClusterPaths

protected T extends FailoverClusterPaths failoverClusterPaths

client

protected org.apache.curator.framework.CuratorFramework client

Constructor Detail

FailoverStrategy

public FailoverStrategy()

Method Detail

initialize

public void initialize(org.apache.curator.framework.CuratorFramework client,
                       ClusterPaths clusterPaths)

start

public void start()

stop

public void stop()

stateChanged

public void stateChanged(org.apache.curator.framework.CuratorFramework client,
                         org.apache.curator.framework.state.ConnectionState newState)

Specified by:

stateChanged in interface org.apache.curator.framework.state.ConnectionStateListener

addTags

protected void addTags(XTag... tags)

Adds a set of XTags to the XEnvironment. This method allows multiple tags to be added at a time. That is to allow failover processing based on multiple tags at a given time. Each strategy should take care of how it is going to add and remove tags from the tag container.

Parameters:

tags - tags to be added

removeTags

protected void removeTags(XTag... tags)

Removes a set of tags from the XEnvironment.

Parameters:

tags - tags to be removed

See Also:

addTags(XTag...)

getFailoverClusterPaths

public T getFailoverClusterPaths()

initStrategy

protected abstract void initStrategy()

startStrategy

protected abstract void startStrategy()

stopStrategy

protected abstract void stopStrategy()

refresh

protected abstract void refresh()

This method is called whenever the failover strategy believes that the connection state became unstable and again re became stable. In such occasions the implementation might need to recheck for interested ZNodes and identity the needs of providing failover.

resetTags

protected abstract void resetTags()

Whenever the connection state changes to lost or suspended, this method will be called in order to remove the tags added by the extending concrete strategy. Therefore, the classes implementing this method should make sure that no tags added by that class is in the environment anymore by removing them if they exist.

newFailoverClusterPaths

protected abstract T newFailoverClusterPaths()

getFailoverMatrix

public abstract Map<String,?> getFailoverMatrix()

toString

public abstract String toString()

Overrides:

toString in class Object