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Service Orchestrator - Low Level Design
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‎service-orchestrator/pom.xml

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<?xml version="1.0" encoding="UTF-8"?>
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<project xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
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xmlns="http://maven.apache.org/POM/4.0.0"
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xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
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<modelVersion>4.0.0</modelVersion>
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<groupId>org.example</groupId>
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<artifactId>service-orchestrator</artifactId>
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<version>1.0</version>
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<build>
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<plugins>
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<plugin>
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<groupId>org.apache.maven.plugins</groupId>
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<artifactId>maven-compiler-plugin</artifactId>
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<configuration>
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<source>11</source>
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<target>11</target>
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</configuration>
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</plugin>
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</plugins>
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</build>
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<dependencies>
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<dependency>
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<groupId>junit</groupId>
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<artifactId>junit</artifactId>
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<version>4.13.1</version>
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<scope>test</scope>
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</dependency>
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</dependencies>
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</project>

‎service-orchestrator/service-orchestrator.iml

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<?xml version="1.0" encoding="UTF-8"?>
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<module org.jetbrains.idea.maven.project.MavenProjectsManager.isMavenModule="true" type="JAVA_MODULE" version="4">
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<component name="NewModuleRootManager" LANGUAGE_LEVEL="JDK_11">
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<output url="file://$MODULE_DIR$/target/classes" />
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<output-test url="file://$MODULE_DIR$/target/test-classes" />
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<content url="file://$MODULE_DIR$">
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<sourceFolder url="file://$MODULE_DIR$/src/main/java" isTestSource="false" />
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<sourceFolder url="file://$MODULE_DIR$/src/test/java" isTestSource="true" />
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<excludeFolder url="file://$MODULE_DIR$/${project.build.directory}/classes" />
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<excludeFolder url="file://$MODULE_DIR$/${project.build.directory}/test-classes" />
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<excludeFolder url="file://$MODULE_DIR$/target" />
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</content>
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<orderEntry type="inheritedJdk" />
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<orderEntry type="sourceFolder" forTests="false" />
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<orderEntry type="library" scope="TEST" name="Maven: junit:junit:4.13.1" level="project" />
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<orderEntry type="library" scope="TEST" name="Maven: org.hamcrest:hamcrest-core:1.3" level="project" />
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</component>
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</module>

‎service-orchestrator/src/main/java/LoadBalancer.java

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import models.Node;
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import models.Request;
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import models.Service;
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import java.util.Map;
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import java.util.concurrent.ConcurrentHashMap;
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public class LoadBalancer {
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private final Map<String, Service> services;
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private final Map<String, Node> nodes;
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public LoadBalancer() {
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this.services = new ConcurrentHashMap<>();
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this.nodes = new ConcurrentHashMap<>();
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}
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public void register(Service service) {
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services.put(service.getId(), service);
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}
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public void addNode(String serviceId, Node node) {
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nodes.put(node.getId(), node);
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services.get(serviceId).getRouter().addNode(node);
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}
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public void removeNode(String serviceId, String nodeId) {
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services.get(serviceId).getRouter().removeNode(nodes.remove(nodeId));
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}
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public Node getHandler(Request request) {
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return services.get(request.getServiceId()).getRouter().getAssignedNode(request);
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}
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}

‎service-orchestrator/src/main/java/algorithms/ConsistentHashing.java

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package algorithms;
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import models.Node;
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import models.Request;
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import java.util.List;
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import java.util.Map;
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import java.util.concurrent.ConcurrentHashMap;
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import java.util.concurrent.ConcurrentSkipListMap;
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import java.util.concurrent.CopyOnWriteArrayList;
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import java.util.function.Function;
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public class ConsistentHashing implements Router {
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private final Map<Node, List<Long>> nodePositions;
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private final ConcurrentSkipListMap<Long, Node> nodeMappings;
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private final Function<String, Long> hashFunction;
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private final int pointMultiplier;
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public ConsistentHashing(final Function<String, Long> hashFunction,
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final int pointMultiplier) {
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if (pointMultiplier == 0) {
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throw new IllegalArgumentException();
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}
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this.pointMultiplier = pointMultiplier;
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this.hashFunction = hashFunction;
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this.nodePositions = new ConcurrentHashMap<>();
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this.nodeMappings = new ConcurrentSkipListMap<>();
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}
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public void addNode(Node node) {
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nodePositions.put(node, new CopyOnWriteArrayList<>());
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for (int i = 0; i < pointMultiplier; i++) {
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for (int j = 0; j < node.getWeight(); j++) {
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final var point = hashFunction.apply((i * pointMultiplier + j) + node.getId());
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nodePositions.get(node).add(point);
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nodeMappings.put(point, node);
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}
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}
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}
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public void removeNode(Node node) {
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for (final Long point : nodePositions.remove(node)) {
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nodeMappings.remove(point);
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}
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}
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public Node getAssignedNode(Request request) {
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final var key = hashFunction.apply(request.getId());
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final var entry = nodeMappings.higherEntry(key);
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if (entry == null) {
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return nodeMappings.firstEntry().getValue();
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} else {
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return entry.getValue();
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}
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}
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}

‎service-orchestrator/src/main/java/algorithms/Router.java

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package algorithms;
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import models.Node;
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import models.Request;
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public interface Router {
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void addNode(Node node);
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void removeNode(Node node);
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Node getAssignedNode(Request request);
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}

‎service-orchestrator/src/main/java/algorithms/WeightedRoundRobin.java

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package algorithms;
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import models.Node;
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import models.Request;
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import java.util.ArrayList;
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import java.util.List;
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public class WeightedRoundRobin implements Router {
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private final List<Node> nodes;
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private final Object lock;
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private int assignTo;
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private int currentNodeAssignments;
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public WeightedRoundRobin() {
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this.nodes = new ArrayList<>();
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this.assignTo = 0;
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this.lock = new Object();
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}
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public void addNode(Node node) {
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synchronized (this.lock) {
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nodes.add(node);
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}
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}
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public void removeNode(Node node) {
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synchronized (this.lock) {
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nodes.remove(node);
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assignTo--;
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currentNodeAssignments = 0;
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}
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}
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public Node getAssignedNode(Request request) {
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synchronized (this.lock) {
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assignTo = (assignTo + nodes.size()) % nodes.size();
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final var currentNode = nodes.get(assignTo);
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currentNodeAssignments++;
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if (currentNodeAssignments == currentNode.getWeight()) {
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assignTo++;
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currentNodeAssignments = 0;
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}
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return currentNode;
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}
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}
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}

‎service-orchestrator/src/main/java/models/Node.java

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package models;
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import java.util.Objects;
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public class Node {
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private final String id;
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private final int weight;
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private final String ipAddress;
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public Node(String id, String ipAddress) {
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this(id, ipAddress, 1);
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}
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public Node(String id, String ipAddress, int weight) {
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this.id = id;
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this.weight = weight;
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this.ipAddress = ipAddress;
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}
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public String getId() {
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return id;
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}
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public int getWeight() {
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return weight;
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}
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public String getIpAddress() {
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return ipAddress;
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}
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@Override
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public boolean equals(Object o) {
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if (this == o) return true;
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if (o == null || getClass() != o.getClass()) return false;
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Node node = (Node) o;
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return id.equals(node.id);
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}
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@Override
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public int hashCode() {
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return Objects.hash(id);
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}
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}

‎service-orchestrator/src/main/java/models/Request.java

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package models;
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public class Request {
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private final String id;
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private final String serviceId;
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private final String method;
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public Request(String id, String serviceId, String method) {
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this.id = id;
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this.serviceId = serviceId;
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this.method = method;
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}
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public String getId() {
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return id;
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}
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public String getServiceId() {
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return serviceId;
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}
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public String getMethod() {
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return method;
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}
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}

‎service-orchestrator/src/main/java/models/Service.java

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package models;
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import algorithms.Router;
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public class Service {
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private final Router router;
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private final String id;
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private final String[] methods;
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public Service(String id, Router router, String[] methods) {
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this.router = router;
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this.id = id;
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this.methods = methods;
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}
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public Router getRouter() {
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return router;
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}
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public String getId() {
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return id;
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}
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public String[] getMethods() {
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return methods;
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}
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}

‎service-orchestrator/src/test/java/LBTester.java

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import algorithms.ConsistentHashing;
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import algorithms.WeightedRoundRobin;
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import models.Node;
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import models.Request;
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import models.Service;
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import org.junit.Assert;
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import org.junit.Test;
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public class LBTester {
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@Test
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public void LBDefaultBehaviour() {
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LoadBalancer loadBalancer = new LoadBalancer();
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final var consistentHashing = new ConsistentHashing(point -> (long) Math.abs(point.hashCode()) % 100, 1);
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final String profileServiceId = "profile", smsServiceId = "sms", emailServiceId = "email";
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loadBalancer.register(new Service(profileServiceId, consistentHashing, new String[]{"addProfile", "deleteProfile", "updateProfile"}));
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loadBalancer.register(new Service(smsServiceId, new WeightedRoundRobin(), new String[]{"sendSms", "addTemplate", "getSMSForUser"}));
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loadBalancer.register(new Service(emailServiceId, new WeightedRoundRobin(), new String[]{"sendEmail", "addTemplate", "getSMSForUser"}));
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final Node pNode1 = new Node("51", "35.45.55.65", 2), pNode2 = new Node("22", "35.45.55.66", 3);
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loadBalancer.addNode(profileServiceId, pNode1);
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loadBalancer.addNode(profileServiceId, pNode2);
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final Node sNode1 = new Node("13", "35.45.55.67"), sNode2 = new Node("64", "35.45.55.68");
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loadBalancer.addNode(smsServiceId, sNode1);
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loadBalancer.addNode(smsServiceId, sNode2);
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final Node eNode1 = new Node("node-35", "35.45.55.69", 2), eNode2 = new Node("node-76", "35.45.55.70");
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loadBalancer.addNode(emailServiceId, eNode1);
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loadBalancer.addNode(emailServiceId, eNode2);
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var profileNode1 = loadBalancer.getHandler(new Request("r-123", profileServiceId, "addProfile"));
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var profileNode2 = loadBalancer.getHandler(new Request("r-244", profileServiceId, "addProfile"));
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var profileNode3 = loadBalancer.getHandler(new Request("r-659", profileServiceId, "addProfile"));
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var profileNode4 = loadBalancer.getHandler(new Request("r-73", profileServiceId, "addProfile"));
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Assert.assertEquals(pNode1, profileNode1);
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Assert.assertEquals(pNode1, profileNode2);
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Assert.assertEquals(pNode2, profileNode3);
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Assert.assertEquals(pNode1, profileNode4);
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loadBalancer.removeNode(profileServiceId, pNode1.getId());
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profileNode1 = loadBalancer.getHandler(new Request("r-123", profileServiceId, "addProfile"));
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profileNode2 = loadBalancer.getHandler(new Request("r-244", profileServiceId, "addProfile"));
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profileNode3 = loadBalancer.getHandler(new Request("r-659", profileServiceId, "addProfile"));
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profileNode4 = loadBalancer.getHandler(new Request("r-73", profileServiceId, "addProfile"));
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Assert.assertEquals(pNode2, profileNode1);
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Assert.assertEquals(pNode2, profileNode2);
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Assert.assertEquals(pNode2, profileNode3);
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Assert.assertEquals(pNode2, profileNode4);
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final var smsNode1 = loadBalancer.getHandler(new Request("r-124", smsServiceId, "addTemplate"));
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final var smsNode2 = loadBalancer.getHandler(new Request("r-1214", smsServiceId, "addTemplate"));
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final var smsNode3 = loadBalancer.getHandler(new Request("r-4", smsServiceId, "addTemplate"));
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Assert.assertEquals(sNode1, smsNode1);
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Assert.assertEquals(sNode2, smsNode2);
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Assert.assertEquals(sNode1, smsNode3);
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final var emailNode1 = loadBalancer.getHandler(new Request("r-1232", emailServiceId, "addTemplate"));
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final var emailNode2 = loadBalancer.getHandler(new Request("r-4134", emailServiceId, "addTemplate"));
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final var emailNode3 = loadBalancer.getHandler(new Request("r-23432", emailServiceId, "addTemplate"));
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final var emailNode4 = loadBalancer.getHandler(new Request("r-5345", emailServiceId, "addTemplate"));
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Assert.assertEquals(eNode1, emailNode1);
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Assert.assertEquals(eNode1, emailNode2);
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Assert.assertEquals(eNode2, emailNode3);
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Assert.assertEquals(eNode1, emailNode4);
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}
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}

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