org.apache.cxf.clustering
Class LoadDistributorTargetSelector

java.lang.Object
  org.apache.cxf.endpoint.AbstractConduitSelector
      org.apache.cxf.clustering.FailoverTargetSelector
          org.apache.cxf.clustering.LoadDistributorTargetSelector

All Implemented Interfaces:

Closeable, ConduitSelector

public class LoadDistributorTargetSelector
extends FailoverTargetSelector

Author:

jtalbut The LoadDistributorTargetSelector attempts to do the same job as the FailoverTargetSelector, but to choose an alternate target on every request rather than just when a fault occurs. The LoadDistributorTargetSelector uses the same FailoverStrategy interface as the FailoverTargetSelector, but has a few significant limitations: 1. Because the LoadDistributorTargetSelector needs to maintain a list of targets between calls it has to obtain that list without reference to a Message. Most FailoverStrategy classes can support this for addresses, but it cannot be supported for endpoints. If the list of targets cannot be obtained without reference to a Message then the list will still be obtained but it will be specific to the Message and thus discarded after this message has been processed. As a consequence, if the strategy chosen is a simple sequential one the first item in the list will be chosen every time. Conclusion: Be aware that if you are working with targets that are dependent on the Message the process will be less efficient and that the SequentialStrategy will not distribute the load at all. 2. The AbstractStaticFailoverStrategy base class excludes the 'default' endpoint from the list of alternate endpoints. If alternate endpoints (as opposed to alternate addresses) are to be used you should probably ensure that your FailoverStrategy overrides getAlternateEndpoints and calls getEndpoints with acceptCandidatesWithSameAddress = true.

Nested Class Summary

Nested classes/interfaces inherited from class org.apache.cxf.clustering.FailoverTargetSelector

FailoverTargetSelector.InvocationContext, FailoverTargetSelector.InvocationKey

Field Summary

Fields inherited from class org.apache.cxf.clustering.FailoverTargetSelector

failoverStrategy, inProgress

Fields inherited from class org.apache.cxf.endpoint.AbstractConduitSelector

endpoint, KEEP_CONDUIT_ALIVE, selectedConduit

Constructor Summary

LoadDistributorTargetSelector()
Normal constructor.

LoadDistributorTargetSelector(Conduit c)
Constructor, allowing a specific conduit to override normal selection.

Method Summary

protected Endpoint	getFailoverTarget(Exchange exchange, FailoverTargetSelector.InvocationContext invocation) Get the failover target endpoint, if a suitable one is available.
protected Logger	getLogger()
boolean	isFailover()
protected boolean	requiresFailover(Exchange exchange) Check if the exchange is suitable for a failover.
Conduit	selectConduit(Message message) Called when a Conduit is actually required.
void	setFailover(boolean failover)

Methods inherited from class org.apache.cxf.clustering.FailoverTargetSelector

complete, getDelayBetweenRetries, getStrategy, overrideAddressProperty, prepare, setStrategy

Methods inherited from class org.apache.cxf.endpoint.AbstractConduitSelector

close, getEndpoint, getSelectedConduit, replaceEndpointAddressPropertyIfNeeded, setEndpoint

Methods inherited from class java.lang.Object

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

Constructor Detail

LoadDistributorTargetSelector

public LoadDistributorTargetSelector()

Normal constructor.

LoadDistributorTargetSelector

public LoadDistributorTargetSelector(Conduit c)

Constructor, allowing a specific conduit to override normal selection.

Parameters:

c - specific conduit

Method Detail

isFailover

public boolean isFailover()

setFailover

public void setFailover(boolean failover)

getLogger

protected Logger getLogger()

Overrides:

getLogger in class FailoverTargetSelector

Returns:

the logger to use

selectConduit

public Conduit selectConduit(Message message)

Called when a Conduit is actually required.

Specified by:

selectConduit in interface ConduitSelector

Overrides:

selectConduit in class FailoverTargetSelector

Parameters:

message -

Returns:

the Conduit to use for mediation of the message

getFailoverTarget

protected Endpoint getFailoverTarget(Exchange exchange,
                                     FailoverTargetSelector.InvocationContext invocation)

Get the failover target endpoint, if a suitable one is available.

Overrides:

getFailoverTarget in class FailoverTargetSelector

Parameters:

exchange - the current Exchange

invocation - the current InvocationContext

Returns:

a failover endpoint if one is available Note: The only difference between this and the super implementation is that the current (failed) address is removed from the list set of alternates, it could be argued that that change should be in the super implementation but I'm not sure of the impact.

requiresFailover

protected boolean requiresFailover(Exchange exchange)

Description copied from class: FailoverTargetSelector

Check if the exchange is suitable for a failover.

Overrides:

requiresFailover in class FailoverTargetSelector

Parameters:

exchange - the current Exchange

Returns:

boolean true if a failover should be attempted