redisson连接池配置_redis连接池原理

文章目录

• Pre
• Code
• 初始化
• 槽计算
• 无需手工调用close方法

Pre

Redis进阶-Redis集群原理剖析及gossip协议初探 集群原理部分 简单的提了下Jest是如何实现Redis Cluster 的 ，这里我们再来梳理一下

Code

import redis.clients.jedis.HostAndPort;
import redis.clients.jedis.JedisCluster;
import redis.clients.jedis.JedisPoolConfig;
import java.io.IOException;
import java.util.HashSet;
import java.util.Set;
public class JedisClusterDemo { 

public static void main(String[] args) throws IOException { 

JedisPoolConfig config = new JedisPoolConfig();
config.setMaxTotal(20);
config.setMaxIdle(10);
config.setMinIdle(5);
Set<HostAndPort> jedisClusterNode = new HashSet<HostAndPort>();
jedisClusterNode.add(new HostAndPort("192.168.18.131", 8001));
jedisClusterNode.add(new HostAndPort("192.168.18.131", 8004));
jedisClusterNode.add(new HostAndPort("192.168.18.132", 8002));
jedisClusterNode.add(new HostAndPort("192.168.18.132", 8005));
jedisClusterNode.add(new HostAndPort("192.168.18.133", 8003));
jedisClusterNode.add(new HostAndPort("192.168.18.133", 8006));
JedisCluster jedisCluster = null;
try { 

//connectionTimeout：指的是连接一个url的连接等待时间
//soTimeout：指的是连接上一个url，获取response的返回等待时间
jedisCluster = new JedisCluster(jedisClusterNode, 6000, 5000, 10, "artisan", config);
System.out.println(jedisCluster.set("clusterArtisan", "artisanValue"));
System.out.println(jedisCluster.get("clusterArtisan"));
} catch (Exception e) { 

e.printStackTrace();
} finally { 

if (jedisCluster != null)
jedisCluster.close();
}
}
}

这里是个简单的demo， 生产中用的话，需要确保jedisCluster是单例的，并且无需手工调用close，不然的话 这个连接池就关闭了，你就无法获取到连接了。

初始化

当 Redis Cluster 的客户端来连接集群时，它也会得到一份集群的槽位配置信息并将其缓存在客户端本地。这样当客户端要查找某个 key 时，可以直接定位到目标节点。

我们来看下jedis的实现

 jedisCluster = new JedisCluster(jedisClusterNode, 6000, 5000, 10, "artisan", config);

跟下源码

public JedisClusterConnectionHandler(Set<HostAndPort> nodes,
final GenericObjectPoolConfig poolConfig, int connectionTimeout, int soTimeout, String password) { 

this.cache = new JedisClusterInfoCache(poolConfig, connectionTimeout, soTimeout, password);
initializeSlotsCache(nodes, poolConfig, password);
}

重点看下 initializeSlotsCache

  private void initializeSlotsCache(Set<HostAndPort> startNodes, GenericObjectPoolConfig poolConfig, String password) { 

for (HostAndPort hostAndPort : startNodes) { 

Jedis jedis = new Jedis(hostAndPort.getHost(), hostAndPort.getPort());
if (password != null) { 

jedis.auth(password);
}
try { 

cache.discoverClusterNodesAndSlots(jedis);
break;
} catch (JedisConnectionException e) { 

// try next nodes
} finally { 

if (jedis != null) { 

jedis.close();
}
}
}
}

继续 cache.discoverClusterNodesAndSlots(jedis); cache为 JedisClusterInfoCache 对象。

  public void discoverClusterNodesAndSlots(Jedis jedis) { 

w.lock();
try { 

reset();
List<Object> slots = jedis.clusterSlots();
for (Object slotInfoObj : slots) { 

List<Object> slotInfo = (List<Object>) slotInfoObj;
if (slotInfo.size() <= MASTER_NODE_INDEX) { 

continue;
}
List<Integer> slotNums = getAssignedSlotArray(slotInfo);
// hostInfos
int size = slotInfo.size();
for (int i = MASTER_NODE_INDEX; i < size; i++) { 

List<Object> hostInfos = (List<Object>) slotInfo.get(i);
if (hostInfos.size() <= 0) { 

continue;
}
HostAndPort targetNode = generateHostAndPort(hostInfos);
setupNodeIfNotExist(targetNode);
if (i == MASTER_NODE_INDEX) { 

assignSlotsToNode(slotNums, targetNode);
}
}
}
} finally { 

w.unlock();
}
}

槽计算

set --------> run  ----> runWithRetries ----> connectionHandler.getConnectionFromSlot(JedisClusterCRC16.getSlot(key))

CRC16算法，计算key对应的slot connectionHandler.getConnectionFromSlot(JedisClusterCRC16.getSlot(key))

  public static int getSlot(byte[] key) { 

int s = -1;
int e = -1;
boolean sFound = false;
for (int i = 0; i < key.length; i++) { 

if (key[i] == '{' && !sFound) { 

s = i;
sFound = true;
}
if (key[i] == '}' && sFound) { 

e = i;
break;
}
}
if (s > -1 && e > -1 && e != s + 1) { 

return getCRC16(key, s + 1, e) & (16384 - 1);
}
return getCRC16(key) & (16384 - 1);
}

无需手工调用close方法

进入到set方法中看下源码

jedisCluster.set("clusterArtisan", "artisanValue")

如下：

  @Override
public String set(final String key, final String value) { 

return new JedisClusterCommand<String>(connectionHandler, maxAttempts) { 

@Override
public String execute(Jedis connection) { 

return connection.set(key, value);
}
}.run(key);
}

命令模式， 关注 run方法

  public T run(String key) { 

if (key == null) { 

throw new JedisClusterException("No way to dispatch this command to Redis Cluster.");
}
return runWithRetries(SafeEncoder.encode(key), this.maxAttempts, false, false);
}

继续 runWithRetries ， 截取核心逻辑

private T runWithRetries(byte[] key, int attempts, boolean tryRandomNode, boolean asking) { 

Jedis connection = null;
try { 

if (asking) { 

......
} else { 

if (tryRandomNode) { 

connection = connectionHandler.getConnection();
} else { 

connection = connectionHandler.getConnectionFromSlot(JedisClusterCRC16.getSlot(key));
}
}
return execute(connection);
} finally { 

releaseConnection(connection);
}
}

关注点

• CRC16算法，计算key对应的slot connectionHandler.getConnectionFromSlot(JedisClusterCRC16.getSlot(key))

  public static int getSlot(byte[] key) { 

int s = -1;
int e = -1;
boolean sFound = false;
for (int i = 0; i < key.length; i++) { 

if (key[i] == '{' && !sFound) { 

s = i;
sFound = true;
}
if (key[i] == '}' && sFound) { 

e = i;
break;
}
}
if (s > -1 && e > -1 && e != s + 1) { 

return getCRC16(key, s + 1, e) & (16384 - 1);
}
return getCRC16(key) & (16384 - 1);
}

• getConnectionFromSlot 通过 JedisPool 获取连接

关注下 JedisCluster是如何获取连接的 getConnectionFromSlot 方法

  @Override
public Jedis getConnectionFromSlot(int slot) { 

JedisPool connectionPool = cache.getSlotPool(slot);
if (connectionPool != null) { 

// It can't guaranteed to get valid connection because of node
// assignment
return connectionPool.getResource();
} else { 

renewSlotCache(); //It's abnormal situation for cluster mode, that we have just nothing for slot, try to rediscover state
connectionPool = cache.getSlotPool(slot);
if (connectionPool != null) { 

return connectionPool.getResource();
} else { 

//no choice, fallback to new connection to random node
return getConnection();
}
}
}

本质上还是通过 JedisPool 来获取一个getResource ，跟我们使用Sentinel 啊 单节点获取方法是一样的

• finally 语句中的 releaseConnection(connection); ,自动释放连接

看下该方法

  private void releaseConnection(Jedis connection) { 

if (connection != null) { 

connection.close();
}
}

说白了，JedisCluster set后会自动释放连接，调用的是jedis 的close方法，所以我们无需手工关闭，否则你这个jedis的连接池就挂逼了…

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