序

本文主要研究一下LettucePoolingConnectionProvider

LettucePoolingConnectionProvider

spring-data-redis-2.0.10.RELEASE-sources.jar!/org/springframework/data/redis/connection/lettuce/LettucePoolingConnectionProvider.java

/** * {@link LettuceConnectionProvider} with connection pooling support. This connection provider holds multiple pools (one * per connection type) for contextualized connection allocation. * 
 * Each allocated connection is tracked and to be returned into the pool which created the connection. Instances of this * class require {@link #destroy() disposal} to de-allocate lingering connections that were not returned to the pool and * to close the pools. * * @author Mark Paluch * @author Christoph Strobl * @since 2.0 * @see #getConnection(Class) */class LettucePoolingConnectionProvider implements LettuceConnectionProvider, RedisClientProvider, DisposableBean {	private final static Log log = LogFactory.getLog(LettucePoolingConnectionProvider.class);	private final LettuceConnectionProvider connectionProvider;	private final GenericObjectPoolConfig poolConfig;	private final Map
    
     , GenericObjectPool
     
      >> poolRef = new ConcurrentHashMap<>(			32);	private final Map
      
       , GenericObjectPool
       
        >> pools = new ConcurrentHashMap<>(32);	LettucePoolingConnectionProvider(LettuceConnectionProvider connectionProvider,			LettucePoolingClientConfiguration clientConfiguration) {		Assert.notNull(connectionProvider, "ConnectionProvider must not be null!");		Assert.notNull(clientConfiguration, "ClientConfiguration must not be null!");		this.connectionProvider = connectionProvider;		this.poolConfig = clientConfiguration.getPoolConfig();	}	/*	 * (non-Javadoc)	 * @see org.springframework.data.redis.connection.lettuce.LettuceConnectionProvider#getConnection(java.lang.Class)	 */	@Override	public 
        
         > T getConnection(Class
         
           connectionType) { GenericObjectPool
          
           > pool = pools.computeIfAbsent(connectionType, poolType -> { return ConnectionPoolSupport.createGenericObjectPool(() -> connectionProvider.getConnection(connectionType), poolConfig, false); }); try { StatefulConnection
            connection = pool.borrowObject(); poolRef.put(connection, pool); return connectionType.cast(connection); } catch (Exception e) { throw new PoolException("Could not get a resource from the pool", e); } } /* * (non-Javadoc) * @see org.springframework.data.redis.connection.lettuce.RedisClientProvider#getRedisClient() */ @Override public AbstractRedisClient getRedisClient() { if (connectionProvider instanceof RedisClientProvider) { return ((RedisClientProvider) connectionProvider).getRedisClient(); } throw new IllegalStateException( String.format("Underlying connection provider %s does not implement RedisClientProvider!", connectionProvider.getClass().getName())); } /* * (non-Javadoc) * @see org.springframework.data.redis.connection.lettuce.LettuceConnectionProvider#release(io.lettuce.core.api.StatefulConnection) */ @Override public void release(StatefulConnection
            connection) { GenericObjectPool
           
            > pool = poolRef.remove(connection); if (pool == null) { throw new PoolException("Returned connection " + connection + " was either previously returned or does not belong to this connection provider"); } pool.returnObject(connection); } /* * (non-Javadoc) * @see org.springframework.beans.factory.DisposableBean#destroy() */ @Override public void destroy() throws Exception { if (!poolRef.isEmpty()) { log.warn("LettucePoolingConnectionProvider contains unreleased connections"); poolRef.forEach((connection, pool) -> pool.returnObject(connection)); poolRef.clear(); } pools.forEach((type, pool) -> pool.close()); pools.clear(); }}
           
          
         
        
       
      
     
    

• 这个provider与普通的连接不同，它区分了不同类型的连接池，因而pools是map结构的，而且还多了poolRef这个map来维护每个连接所在连接池
• pools主要是用于根据连接类型获取对应连接池，用于连接的借用场景，而poolRef主要是用于连接的归还场景
• 这里采用了ConcurrentHashMap的computeIfAbsent方法，对于key不存在的则触发创建并返回，对于key存在的则直接返回

小结

• lettuce 4.0版本引入了StatefulConnection，它会维护登录、事务、所选数据库，读写等状态
• StatefulConnection有几个类型，分别是StatefulRedisConnection(StatefulRedisPubSubConnection、StatefulRedisMasterSlaveConnection)、StatefulRedisSentinelConnection、StatefulRedisClusterConnection
• LettucePoolingConnectionProvider维护了多类型的连接的连接池，因而采用map的数据结构，不然单一类型的连接直接使用GenericObjectPool即可

doc