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 a EJB 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 EJB. If discovery yields a URI or cluster, this mechanism is not used.

Author:

Jaikiran Pai

Field Summary

Fields

Modifier and Type	Field and 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	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 and 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.

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)