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/*
* JBoss, Home of Professional Open Source.
* Copyright 2017 Red Hat, Inc., and individual contributors
* as indicated by the @author tags.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.jboss.ejb.client;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.HashSet;
import java.util.concurrent.ThreadLocalRandom;
import java.util.concurrent.atomic.AtomicInteger;
import org.jboss.ejb._private.Logs;
import org.wildfly.common.Assert;
/**
* 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 {@link 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
* @author Wolf Dieter Fink
*/
public interface DeploymentNodeSelector {
/**
* 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
*
* @param eligibleNodes the eligible nodes which can handle the deployment; not {@code null}, will not be empty
* @param appName the app name of the deployment
* @param moduleName the module name of the deployment
* @param distinctName the distinct name of the deployment
* @return the node selection (must not be {@code null})
*/
String selectNode(final String[] eligibleNodes, final String appName, final String moduleName, final String distinctName);
/**
* Create a deployment node selector that prefers one or more favorite nodes, falling back to another selector if
* none of the favorites are found.
*
* @param favorites the favorite nodes, in decreasing order of preference (must not be {@code null})
* @param fallback the fallback selector (must not be {@code null})
* @return the selector (not {@code null})
*/
static DeploymentNodeSelector favorite(Collection favorites, DeploymentNodeSelector fallback) {
Assert.checkNotNullParam("favorites", favorites);
Assert.checkNotNullParam("fallback", fallback);
return (eligibleNodes, appName, moduleName, distinctName) -> {
final HashSet set = new HashSet(eligibleNodes.length);
Collections.addAll(set, eligibleNodes);
for (String favorite : favorites) {
if (set.contains(favorite)) {
if (Logs.MAIN.isDebugEnabled()) {
Logs.MAIN.debugf("FAVORITE node %s for [app: %s, module: %s, distinctname: %s]", favorite, appName, moduleName, distinctName);
}
return favorite;
}
}
if(Logs.MAIN.isDebugEnabled()) {
Logs.MAIN.debugf("FAVORITE no favorite found use fallback for [eligibleNodes %s, app: %s, module: %s, distinctname: %s]", Arrays.deepToString(eligibleNodes), appName, moduleName, distinctName);
}
return fallback.selectNode(eligibleNodes, appName, moduleName, distinctName);
};
}
/**
* A deployment node selector which prefers the first node always. This will generally avoid load balancing in most
* cases.
*/
DeploymentNodeSelector FIRST = (eligibleNodes, appName, moduleName, distinctName) -> eligibleNodes[0];
/**
* 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.
*/
DeploymentNodeSelector RANDOM = (eligibleNodes, appName, moduleName, distinctName) -> eligibleNodes[ThreadLocalRandom.current().nextInt(eligibleNodes.length)];
/**
* 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.
*/
DeploymentNodeSelector ROUND_ROBIN = new DeploymentNodeSelector() {
private final AtomicInteger counter = new AtomicInteger();
public String selectNode(final String[] eligibleNodes, final String appName, final String moduleName, final String distinctName) {
final int length = eligibleNodes.length;
assert length > 0;
if(Logs.MAIN.isTraceEnabled()) {
Logs.MAIN.tracef("ROUND_ROBIN [nodes=%s appName=%s moduleName=%s, distinctName=%s]", Arrays.deepToString(eligibleNodes), appName, moduleName, distinctName);
}
String node = eligibleNodes[Math.floorMod(counter.getAndIncrement(), length)];
if(Logs.MAIN.isDebugEnabled()) {
Logs.MAIN.debugf("ROUND_ROBIN select node %s for [app: %s, module: %s, distinctname: %s]", node, appName, moduleName, distinctName);
}
return node;
}
};
/**
* A deployment node selector which check the server name if inside and prefer it if available for selection.
*/
DeploymentNodeSelector RANDOM_PREFER_LOCAL = new DeploymentNodeSelector() {
private final String localNodeName = SecurityUtils.getString(SystemProperties.JBOSS_NODE_NAME);
public String selectNode(final String[] eligibleNodes, final String appName, final String moduleName, final String distinctName) {
if(Logs.MAIN.isTraceEnabled()) {
Logs.MAIN.tracef("RANDOM_PREFER_LOCAL (%s) [nodes=%s appName=%s moduleName=%s, distinctName=%s]", localNodeName, Arrays.deepToString(eligibleNodes), appName, moduleName, distinctName);
}
// Just a single node available, so just return it
if (eligibleNodes.length == 1) {
return eligibleNodes[0];
}
// prefer local node if available
if(localNodeName != null) {
for (final String eligibleNode : eligibleNodes) {
if (localNodeName.equals(eligibleNode)) {
if (Logs.MAIN.isDebugEnabled()) {
Logs.MAIN.debugf("RANDOM_PREFER_LOCAL select local node %s for [app: %s, module: %s, distinctname: %s]", eligibleNode, appName, moduleName, distinctName);
}
return eligibleNode;
}
}
}
// select one randomly
if (Logs.MAIN.isDebugEnabled()) {
Logs.MAIN.debug("RANDOM_PREFER_LOCAL local node not avaialble, fallback to RANDOM selection");
}
return RANDOM.selectNode(eligibleNodes, appName, moduleName, distinctName);
}
};
}