最近一个项目用到Jedis客户端，需要对这个客户端进行改造。看了一下Jedis Cluster源码，做个记录
首先，说核心内容， 在Jedis源码中，关于cluster有个两个重要的map。一个是nodes，一个是slots
nodes: host:port ----> JedisPool
slots: slot ----> JedisPool
nodes存放的是key为host:port到JedisPool的映射
slots存放的 slot到JedisPool的映射
这里，JedisPool是用apache common pool存放jedis对象的pool，slot是通过Crc16算出对16384取余得到
上个Jedis Cluster的Demo吧
1 import redis.clients.jedis.HostAndPort;
2 import redis.clients.jedis.JedisCluster;
3 import java.util.HashSet;
4 import java.util.Set;
5
6 /**
7 * Created by guanxianseng on 2017/8/15.
8 *
9 * nodes: host:port -> JedisPool
10 * slots: slot -> JedisPool
11 */
12 public class TestCluster {
13 public static void main(String[] args) {
14 Set<HostAndPort> jedisClusterNodes = new HashSet<HostAndPort>();
15 jedisClusterNodes.add(new HostAndPort("192.168.211.131", 7340));
16 jedisClusterNodes.add(new HostAndPort("192.168.211.131", 7341));
17 jedisClusterNodes.add(new HostAndPort("192.168.211.131", 7342));
18 JedisCluster jc = new JedisCluster(jedisClusterNodes);
19 jc.set("name", "guanxianseng");
20 System.out.println(jc.get("name"));
21 }
22 }
输出
guanxianseng Process finished with exit code 0
这里IP是我的虚拟机的IP，开了两台虚拟机，部署的是三主三从的集群
首先，进入JedisCluster的构造函数，一路找下去，我们会看到这样的代码
1 public JedisClusterConnectionHandler(Set<HostAndPort> nodes,
2 final GenericObjectPoolConfig poolConfig, int connectionTimeout, int soTimeout, String password) {
3 this.cache = new JedisClusterInfoCache(poolConfig, connectionTimeout, soTimeout, password);
4 initializeSlotsCache(nodes, poolConfig, password);
5 }
进入initializeSlotsCache方法
1 private void initializeSlotsCache(Set<HostAndPort> startNodes, GenericObjectPoolConfig poolConfig, String password) {
2 for (HostAndPort hostAndPort : startNodes) {
3 Jedis jedis = new Jedis(hostAndPort.getHost(), hostAndPort.getPort());
4 if (password != null) {
5 jedis.auth(password);
6 }
7 try {
8 cache.discoverClusterNodesAndSlots(jedis);
9 break;
10 } catch (JedisConnectionException e) {
11 // try next nodes
12 } finally {
13 if (jedis != null) {
14 jedis.close();
15 }
16 }
17 }
18 }
这里，获取集群节点的jedis对象，进入discoverClusterNodesAndSlots(jedis)
1 public void discoverClusterNodesAndSlots(Jedis jedis) {
2 w.lock();
3
4 try {
5 reset();
6 List<Object> slots = jedis.clusterSlots();
7
8 for (Object slotInfoObj : slots) {
9 List<Object> slotInfo = (List<Object>) slotInfoObj;
10
11 if (slotInfo.size() <= MASTER_NODE_INDEX) {
12 continue;
13 }
14
15 List<Integer> slotNums = getAssignedSlotArray(slotInfo);
16
17 // hostInfos
18 int size = slotInfo.size();
19 for (int i = MASTER_NODE_INDEX; i < size; i++) {
20 List<Object> hostInfos = (List<Object>) slotInfo.get(i);
21 if (hostInfos.size() <= 0) {
22 continue;
23 }
24
25 HostAndPort targetNode = generateHostAndPort(hostInfos);
26 setupNodeIfNotExist(targetNode);
27 if (i == MASTER_NODE_INDEX) {
28 assignSlotsToNode(slotNums, targetNode);
29 }
30 }
31 }
32 } finally {
33 w.unlock();
34 }
35 }
第6行，其实就是执行slots命令。进入getAssignedSlotArray方法
private List<Integer> getAssignedSlotArray(List<Object> slotInfo) {
List<Integer> slotNums = new ArrayList<Integer>();
for (int slot = ((Long) slotInfo.get(0)).intValue(); slot <= ((Long) slotInfo.get(1))
.intValue(); slot++) {
slotNums.add(slot);
}
return slotNums;
}
这里获取了，节点分配的slots
回到上面，进入generateHostAndPort方法
private HostAndPort generateHostAndPort(List<Object> hostInfos) {
return new HostAndPort(SafeEncoder.encode((byte[]) hostInfos.get(0)),
((Long) hostInfos.get(1)).intValue());
}
这里获取到节点的host和port
回到上面，进入setupNodeIfNotExist(targetNode);
1 public JedisPool setupNodeIfNotExist(HostAndPort node) {
2 w.lock();
3 try {
4 String nodeKey = getNodeKey(node);
5 JedisPool existingPool = nodes.get(nodeKey);
6 if (existingPool != null) return existingPool;
7
8 JedisPool nodePool = new JedisPool(poolConfig, node.getHost(), node.getPort(),
9 connectionTimeout, soTimeout, password, 0, null, false, null, null, null);
10 nodes.put(nodeKey, nodePool);
11 return nodePool;
12 } finally {
13 w.unlock();
14 }
15 }
这里设置我们一开始提到的nodes， host:port -------> JedisPool映射
继续回到上面，进入assignSlotsToNode(slotNums, targetNode);
1 public void assignSlotsToNode(List<Integer> targetSlots, HostAndPort targetNode) {
2 w.lock();
3 try {
4 JedisPool targetPool = setupNodeIfNotExist(targetNode);
5 for (Integer slot : targetSlots) {
6 slots.put(slot, targetPool);
7 }
8 } finally {
9 w.unlock();
10 }
11 }
这里设置了前面说的slots， slot ------> JedisPool的映射
这里初始化完成
执行set命令
1 @Override
2 public String set(final String key, final String value) {
3 return new JedisClusterCommand<String>(connectionHandler, maxAttempts) {
4 @Override
5 public String execute(Jedis connection) {
6 return connection.set(key, value);
7 }
8 }.run(key);
9 }
进入run(key);方法
1 public T run(String key) {
2 if (key == null) {
3 throw new JedisClusterException("No way to dispatch this command to Redis Cluster.");
4 }
5
6 return runWithRetries(SafeEncoder.encode(key), this.maxAttempts, false, false);
7 }
进入runWithRetries()
1 private T runWithRetries(byte[] key, int attempts, boolean tryRandomNode, boolean asking) {
2 if (attempts <= 0) {
3 throw new JedisClusterMaxRedirectionsException("Too many Cluster redirections?");
4 }
5
6 Jedis connection = null;
7 try {
8
9 if (asking) {
10 // TODO: Pipeline asking with the original command to make it
11 // faster....
12 connection = askConnection.get();
13 connection.asking();
14
15 // if asking success, reset asking flag
16 asking = false;
17 } else {
18 if (tryRandomNode) {
19 connection = connectionHandler.getConnection();
20 } else {
21 connection = connectionHandler.getConnectionFromSlot(JedisClusterCRC16.getSlot(key));
22 }
23 }
24
25 return execute(connection);
26
27 } catch (JedisNoReachableClusterNodeException jnrcne) {
这里有点长，截取了前面一部分
1 connection = connectionHandler.getConnectionFromSlot(JedisClusterCRC16.getSlot(key));
这里，计算key的slot，从slots获取Jedis对象
到这，基本已完成
总结一下，执行slots命令，缓存host:port --> JedisPool， slot ---->JedisPool映射。执行命令，key ---> slot ----> JedisPool ------->Jedis
时间： 2024-07-30 13:48:18