Package org.jboss.ejb.client

Interface DeploymentNodeSelector

public interface DeploymentNodeSelector

A selector which selects and returns a node, from among the passed eligible nodes, that can handle a specific deployment within an Enterprise Bean client context. Typical usage of DeploymentNodeSelector involves load balancing calls to multiple nodes which can all handle the same deployment. This allows the application to have a deterministic node selection policy while dealing with multiple nodes with same deployment.

Node selection is only used when discovery yields nodes as a result of its query to locate an Enterprise Bean. If discovery yields a URI or cluster, this mechanism is not used.

Author:

Jaikiran Pai, Wolf Dieter Fink

Field Summary

Fields

Modifier and Type	Field	Description
static DeploymentNodeSelector	FIRST	A deployment node selector which prefers the first node always.
static DeploymentNodeSelector	RANDOM	A deployment node selector which randomly chooses the next node.
static DeploymentNodeSelector	RANDOM_PREFER_LOCAL	A deployment node selector which check the server name if inside and prefer it if available for selection.
static DeploymentNodeSelector	ROUND_ROBIN	A deployment node selector which uses an approximate round-robin policy among all of the eligible nodes.

Method Summary

Modifier and Type	Method	Description
static DeploymentNodeSelector	favorite(Collection<String> favorites, DeploymentNodeSelector fallback)	Create a deployment node selector that prefers one or more favorite nodes, falling back to another selector if none of the favorites are found.
String	selectNode(String[] eligibleNodes, String appName, String moduleName, String distinctName)	Selects and returns a node from among the eligibleNodes to handle the invocation on a deployment represented by the passed appName, moduleName and distinctName combination.

Field Detail

FIRST

static final DeploymentNodeSelector FIRST

A deployment node selector which prefers the first node always. This will generally avoid load balancing in most cases.

RANDOM

static final DeploymentNodeSelector RANDOM

A deployment node selector which randomly chooses the next node. This will generally provide the best possible load balancing over a large number of requests.

ROUND_ROBIN

static final DeploymentNodeSelector ROUND_ROBIN

A deployment node selector which uses an approximate round-robin policy among all of the eligible nodes. Note that the round-robin node count may be shared among multiple node sets, thus certain specific usage patterns may defeat the round-robin behavior.

RANDOM_PREFER_LOCAL

static final DeploymentNodeSelector RANDOM_PREFER_LOCAL

A deployment node selector which check the server name if inside and prefer it if available for selection.

Method Detail

selectNode

String selectNode(String[] eligibleNodes,
                  String appName,
                  String moduleName,
                  String distinctName)

Selects and returns a node from among the eligibleNodes to handle the invocation on a deployment represented by the passed appName, moduleName and distinctName combination. Implementations of this method must not return null or any other node name which isn't in the eligibleNodes

Parameters:

eligibleNodes - the eligible nodes which can handle the deployment; not null, will not be empty

appName - the app name of the deployment

moduleName - the module name of the deployment

distinctName - the distinct name of the deployment

Returns:

the node selection (must not be null)

favorite

static DeploymentNodeSelector favorite(Collection<String> favorites,
                                       DeploymentNodeSelector fallback)

Create a deployment node selector that prefers one or more favorite nodes, falling back to another selector if none of the favorites are found.

Parameters:

favorites - the favorite nodes, in decreasing order of preference (must not be null)

fallback - the fallback selector (must not be null)

Returns:

the selector (not null)