Redis Cluster 通过多种机制来实现高容错性，包括主从复制、自动故障转移和Gossip协议。这些机制确保即使在节点发生故障时，集群仍然能继续运行并提供服务。以下是详细的解释，并结合Java代码示例来说明其实现。
1. 主从复制（Master-Slave Replication）
主从复制是Redis Cluster最基础的高容错机制。每个主节点可以有一个或多个从节点，这些从节点复制主节点的数据。当主节点发生故障时，从节点可以接管其角色。
代码示例
1import java.util.ArrayList; 2import java.util.List; 3 4class ClusterNode { 5 String name; 6 String ip; 7 int port; 8 boolean isMaster; 9 ClusterNode master; 10 11 ClusterNode(String name, String ip, int port, boolean isMaster, ClusterNode master) { 12 this.name = name; 13 this.ip = ip; 14 this.port = port; 15 this.isMaster = isMaster; 16 this.master = master; 17 } 18 19 @Override 20 public String toString() { 21 return "Node " + name + ": " + ip + ":" + port + ", Role: " + (isMaster ? "Master" : "Slave"); 22 } 23} 24 25class Cluster { 26 List<ClusterNode> nodes = new ArrayList<>(); 27 28 void addNode(String name, String ip, int port, boolean isMaster, ClusterNode master) { 29 nodes.add(new ClusterNode(name, ip, port, isMaster, master)); 30 } 31 32 void printNodes() { 33 for (ClusterNode node : nodes) { 34 System.out.println(node); 35 } 36 } 37} 38 39public class RedisClusterDemo { 40 public static void main(String[] args) { 41 Cluster cluster = new Cluster(); 42 43 ClusterNode master1 = new ClusterNode("master1", "192.168.1.1", 6379, true, null); 44 cluster.addNode(master1.name, master1.ip, master1.port, master1.isMaster, master1.master); 45 cluster.addNode("slave1", "192.168.1.2", 6379, false, master1); 46 47 cluster.printNodes(); 48 } 49} 50
2. 自动故障转移（Automatic Failover）
当主节点发生故障时，从节点会被提升为主节点。这个机制需要其他节点的协作，以保证集群的一致性和数据的完整性。
代码示例
1import java.util.ArrayList; 2import java.util.List; 3import java.util.Timer; 4import java.util.TimerTask; 5 6class ClusterNode { 7 String name; 8 String ip; 9 int port; 10 boolean isMaster; 11 ClusterNode master; 12 long lastHeartbeat; 13 boolean isFailed; 14 15 ClusterNode(String name, String ip, int port, boolean isMaster, ClusterNode master) { 16 this.name = name; 17 this.ip = ip; 18 this.port = port; 19 this.isMaster = isMaster; 20 this.master = master; 21 this.lastHeartbeat = System.currentTimeMillis(); 22 this.isFailed = false; 23 } 24 25 void sendHeartbeat() { 26 System.out.println("Sending heartbeat to node " + name); 27 lastHeartbeat = System.currentTimeMillis(); 28 } 29 30 void checkHeartbeat() { 31 long now = System.currentTimeMillis(); 32 if (now - lastHeartbeat > 3000) { // 3 seconds timeout 33 System.out.println("Node " + name + " is not responding"); 34 isFailed = true; 35 } 36 } 37 38 @Override 39 public String toString() { 40 return "Node " + name + ": " + ip + ":" + port + ", Role: " + (isMaster ? "Master" : "Slave"); 41 } 42} 43 44class Cluster { 45 List<ClusterNode> nodes = new ArrayList<>(); 46 47 void addNode(String name, String ip, int port, boolean isMaster, ClusterNode master) { 48 nodes.add(new ClusterNode(name, ip, port, isMaster, master)); 49 } 50 51 void handleFailover() { 52 for (ClusterNode node : nodes) { 53 if (node.isMaster && node.isFailed) { 54 for (ClusterNode slave : nodes) { 55 if (slave.master == node) { 56 System.out.println("Failover: promoting slave node " + slave.name + " to master"); 57 slave.isMaster = true; 58 slave.master = null; 59 node.isMaster = false; 60 return; 61 } 62 } 63 } 64 } 65 } 66 67 void simulateCluster() { 68 Timer timer = new Timer(true); 69 TimerTask task = new TimerTask() { 70 @Override 71 public void run() { 72 for (ClusterNode node : nodes) { 73 if (node.isMaster && !node.isFailed) { 74 node.sendHeartbeat(); 75 } else { 76 node.checkHeartbeat(); 77 if (node.isFailed && node.isMaster) { 78 handleFailover(); 79 } 80 } 81 } 82 } 83 }; 84 timer.scheduleAtFixedRate(task, 0, 1000); 85 } 86 87 void printNodes() { 88 for (ClusterNode node : nodes) { 89 System.out.println(node); 90 } 91 } 92} 93 94public class RedisClusterDemo { 95 public static void main(String[] args) throws InterruptedException { 96 Cluster cluster = new Cluster(); 97 98 ClusterNode master1 = new ClusterNode("master1", "192.168.1.1", 6379, true, null); 99 cluster.addNode(master1.name, master1.ip, master1.port, master1.isMaster, master1.master); 100 cluster.addNode("slave1", "192.168.1.2", 6379, false, master1); 101 cluster.addNode("slave2", "192.168.1.3", 6379, false, master1); 102 103 cluster.printNodes(); 104 105 cluster.simulateCluster(); 106 107 // Simulate a failure of the master after 10 seconds 108 Thread.sleep(10000); 109 master1.isFailed = true; 110 111 // Keep the main thread alive to see the failover in action 112 Thread.sleep(20000); 113 } 114} 115
3. Gossip 协议
Gossip 协议用于节点之间交换状态信息，确保整个集群对节点状态的一致性认识。每个节点会定期向其他节点发送和接收状态信息。
代码示例
1import java.util.ArrayList; 2import java.util.List; 3import java.util.Timer; 4import java.util.TimerTask; 5 6class ClusterNode { 7 String name; 8 String ip; 9 int port; 10 boolean isMaster; 11 ClusterNode master; 12 long lastHeartbeat; 13 boolean isFailed; 14 15 ClusterNode(String name, String ip, int port, boolean isMaster, ClusterNode master) { 16 this.name = name; 17 this.ip = ip; 18 this.port = port; 19 this.isMaster = isMaster; 20 this.master = master; 21 this.lastHeartbeat = System.currentTimeMillis(); 22 this.isFailed = false; 23 } 24 25 void sendHeartbeat() { 26 System.out.println("Sending heartbeat from node " + name); 27 lastHeartbeat = System.currentTimeMillis(); 28 } 29 30 void receiveHeartbeat() { 31 System.out.println("Received heartbeat at node " + name); 32 lastHeartbeat = System.currentTimeMillis(); 33 isFailed = false; 34 } 35 36 void checkHeartbeat() { 37 long now = System.currentTimeMillis(); 38 if (now - lastHeartbeat > 3000) { // 3 seconds timeout 39 System.out.println("Node " + name + " is not responding"); 40 isFailed = true; 41 } 42 } 43 44 @Override 45 public String toString() { 46 return "Node " + name + ": " + ip + ":" + port + ", Role: " + (isMaster ? "Master" : "Slave"); 47 } 48} 49 50class Cluster { 51 List<ClusterNode> nodes = new ArrayList<>(); 52 53 void addNode(String name, String ip, int port, boolean isMaster, ClusterNode master) { 54 nodes.add(new ClusterNode(name, ip, port, isMaster, master)); 55 } 56 57 void handleFailover(ClusterNode failedNode) { 58 for (ClusterNode node : nodes) { 59 if (node.master == failedNode && !node.isFailed) { 60 System.out.println("Failover: promoting slave node " + node.name + " to master"); 61 node.isMaster = true; 62 node.master = null; 63 failedNode.isMaster = false; 64 return; 65 } 66 } 67 } 68 69 void gossip() { 70 for (ClusterNode node : nodes) { 71 if (!node.isFailed) { 72 for (ClusterNode peer : nodes) { 73 if (peer != node) { 74 peer.receiveHeartbeat(); 75 } 76 } 77 } else { 78 handleFailover(node); 79 } 80 } 81 } 82 83 void simulateCluster() { 84 Timer timer = new Timer(true); 85 TimerTask heartbeatTask = new TimerTask() { 86 @Override 87 public void run() { 88 for (ClusterNode node : nodes) { 89 if (!node.isFailed) { 90 node.sendHeartbeat(); 91 } 92 } 93 } 94 }; 95 96 TimerTask gossipTask = new TimerTask() { 97 @Override 98 public void run() { 99 gossip(); 100 } 101 }; 102 103 timer.scheduleAtFixedRate(heartbeatTask, 0, 1000); 104 timer.scheduleAtFixedRate(gossipTask, 0, 1000); 105 } 106 107 void printNodes() { 108 for (ClusterNode node : nodes) { 109 System.out.println(node); 110 } 111 } 112} 113 114
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