org.jboss.ejb.client

Interface ClusterNodeSelector

public interface ClusterNodeSelector

A selector which selects and returns a node from the available nodes in a cluster. Typical usage of a ClusterNodeSelector involve load balancing of calls to various nodes in the cluster.

Author:

Jaikiran Pai

Field Summary

Fields

Modifier and Type	Field and Description
static ClusterNodeSelector	DEFAULT A simple default selector which uses simpleConnectionThresholdRandomSelector(int) with a minimum of 5 connections.
static ClusterNodeSelector	FIRST_AVAILABLE Always use the first available node, regardless of whether it is connected.
static ClusterNodeSelector	FIRST_CONNECTED Always use the first connected node, or fall back to the first available node if none are connected.
static ClusterNodeSelector	RANDOM Use a random available node, regardless of whether it is connected.
static ClusterNodeSelector	RANDOM_CONNECTED Always use a random connected node, or fall back to a random unconnected node.

Method Summary

Modifier and Type	Method and Description
static ClusterNodeSelector	firstConnected(ClusterNodeSelector fallback) Always try to use the first connected node.
static ClusterNodeSelector	minimumConnectionThreshold(int minimum, ClusterNodeSelector unmet, ClusterNodeSelector met) Determine the action to take based on a threshold of minimum connections.
String	selectNode(String clusterName, String[] connectedNodes, String[] totalAvailableNodes) Returns a node from among the totalAvailableNodes, as the target node for EJB invocations.
static ClusterNodeSelector	simpleConnectionThresholdRandomSelector(int minimum) A simple threshold-based random selector.
static ClusterNodeSelector	useRandomConnectedNode(ClusterNodeSelector fallback) Always try to use a random connected node.
static ClusterNodeSelector	useRandomUnconnectedNode(ClusterNodeSelector fallback) Always try to use an unconnected node.
static ClusterNodeSelector	useRoundRobinConnectedNode(ClusterNodeSelector fallback) Always try to round-robin among connected nodes.
static ClusterNodeSelector	useRoundRobinUnconnectedNode(ClusterNodeSelector fallback) Always try to use an unconnected node in a round-robin fashion.

Field Detail

FIRST_AVAILABLE

static final ClusterNodeSelector FIRST_AVAILABLE

Always use the first available node, regardless of whether it is connected.

FIRST_CONNECTED

static final ClusterNodeSelector FIRST_CONNECTED

Always use the first connected node, or fall back to the first available node if none are connected.

RANDOM_CONNECTED

static final ClusterNodeSelector RANDOM_CONNECTED

Always use a random connected node, or fall back to a random unconnected node.

RANDOM

static final ClusterNodeSelector RANDOM

Use a random available node, regardless of whether it is connected.

DEFAULT

static final ClusterNodeSelector DEFAULT

A simple default selector which uses simpleConnectionThresholdRandomSelector(int) with a minimum of 5 connections.

Method Detail

selectNode

String selectNode(String clusterName,
                  String[] connectedNodes,
                  String[] totalAvailableNodes)

Returns a node from among the totalAvailableNodes, as the target node for EJB invocations. The selector can decide whether to pick an already connected node (from the passed connectedNodes) or decide to select a node to which a connection hasn't yet been established. If a node to which a connection hasn't been established is selected then the cluster context will create a connection to it.

Parameters:

clusterName - the name of the cluster to which the nodes belong (will not be null)

connectedNodes - the node names to which a connection has been established (may be empty but will not be null)

totalAvailableNodes - all available nodes in the cluster, including connected nodes (will not be empty or null)

Returns:

the selected node name (must not be null)

simpleConnectionThresholdRandomSelector

static ClusterNodeSelector simpleConnectionThresholdRandomSelector(int minimum)

A simple threshold-based random selector. If the minimum is met, then a random connected node is used, otherwise a random available node is used, increasing the total number of connections for future invocations.

Parameters:

minimum - the minimum number of connected nodes to attempt to acquire

Returns:

the node selector (not null)

firstConnected

static ClusterNodeSelector firstConnected(ClusterNodeSelector fallback)

Always try to use the first connected node. If no nodes are connected, the fallback is used.

Parameters:

fallback - the fallback selector (must not be null)

Returns:

the node selector (not null)

useRandomConnectedNode

static ClusterNodeSelector useRandomConnectedNode(ClusterNodeSelector fallback)

Always try to use a random connected node. If no nodes are connected, the fallback is used.

Parameters:

fallback - the fallback selector (must not be null)

Returns:

the node selector (not null)

useRoundRobinConnectedNode

static ClusterNodeSelector useRoundRobinConnectedNode(ClusterNodeSelector fallback)

Always try to round-robin among connected nodes. If no nodes are connected, the fallback is used. 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.

Parameters:

fallback - the fallback selector (must not be null)

Returns:

the node selector (not null)

minimumConnectionThreshold

static ClusterNodeSelector minimumConnectionThreshold(int minimum,
                                                      ClusterNodeSelector unmet,
                                                      ClusterNodeSelector met)

Determine the action to take based on a threshold of minimum connections. If the minimum is met, or if there are no more available nodes to choose from, the met selector is used, otherwise the unmet selector is used.

Parameters:

minimum - the minimum number of connections

unmet - the selector to use when the number of connections is below the minimum and there are unconnected nodes (must not be null)

met - the selector to use when the number of connections is at or above the minimum or there are no unconnected nodes (must not be null)

Returns:

the node selector (not null)

useRandomUnconnectedNode

static ClusterNodeSelector useRandomUnconnectedNode(ClusterNodeSelector fallback)

Always try to use an unconnected node. If all nodes are connected, the fallback is used.

Parameters:

fallback - the selector to use if all available nodes are connected (must not be null)

Returns:

the node selector (not null)

useRoundRobinUnconnectedNode

static ClusterNodeSelector useRoundRobinUnconnectedNode(ClusterNodeSelector fallback)

Always try to use an unconnected node in a round-robin fashion. If all nodes are connected, the fallback is used.

Parameters:

fallback - the selector to use if all available nodes are connected (must not be null)

Returns:

the node selector (not null)