Redis - Redis頻繁打開關閉連接(RedisConnectionUtils)，有性能問題？？？

    今天在測試代碼的時候無意中發現，使用springboot-redis連接的Redis，在讀寫數據的時候，日志中總是打印“Opening RedisConnection” “Closing Redis Connection”；

13:22:46.343 [LService-16] DEBUG o.s.d.r.core.RedisConnectionUtils - Opening RedisConnection
13:22:46.346 [LService-16] DEBUG o.s.d.r.core.RedisConnectionUtils - Closing Redis Connection
13:22:46.347 [LService-16] DEBUG o.s.d.r.core.RedisConnectionUtils - Opening RedisConnection
13:22:46.349 [LService-16] DEBUG o.s.d.r.core.RedisConnectionUtils - Closing Redis Connection
13:22:46.349 [LService-16] DEBUG o.s.d.r.core.RedisConnectionUtils - Opening RedisConnection
13:22:46.351 [LService-16] DEBUG o.s.d.r.core.RedisConnectionUtils - Closing Redis Connection
13:22:46.351 [LService-16] DEBUG o.s.d.r.core.RedisConnectionUtils - Opening RedisConnection
13:22:46.353 [LService-16] DEBUG o.s.d.r.core.RedisConnectionUtils - Closing Redis Connection

    是不是每一次的讀寫都在創建和銷毀連接？那豈不是很耗費資源？是不是效率很低下？？？

    其實，並不是這樣的。閱讀源代碼我們可以發現我們對redis的所有操作都是通過回調execute函數執行的，spring-boot-redis內部為我們封裝管理了連接池；性能那塊也不用擔心。

public <T> T execute(RedisCallback<T> action, boolean exposeConnection) {  
    return execute(action, exposeConnection, false);  
}  
// execute實現如下：  
// org.springframework.data.redis.core.RedisTemplate<K, V> --- 最終實現  
public <T> T execute(RedisCallback<T> action, boolean exposeConnection, boolean pipeline) {  
    Assert.isTrue(initialized, "template not initialized; call afterPropertiesSet() before using it");  
    Assert.notNull(action, "Callback object must not be null");  
    RedisConnectionFactory factory = getConnectionFactory();  
    RedisConnection conn = null;  
    try {  
        if (enableTransactionSupport) {  
            // only bind resources in case of potential transaction synchronization  
            conn = RedisConnectionUtils.bindConnection(factory, enableTransactionSupport);  
        } else {  
            conn = RedisConnectionUtils.getConnection(factory);  
        }  
        boolean existingConnection = TransactionSynchronizationManager.hasResource(factory);  
        RedisConnection connToUse = preProcessConnection(conn, existingConnection);  
        boolean pipelineStatus = connToUse.isPipelined();  
        if (pipeline && !pipelineStatus) {  
            connToUse.openPipeline();  
        }  
        RedisConnection connToExpose = (exposeConnection ? connToUse : createRedisConnectionProxy(connToUse));  
        T result = action.doInRedis(connToExpose);  
        // close pipeline  
        if (pipeline && !pipelineStatus) {  
            connToUse.closePipeline();  
        }  
        // TODO: any other connection processing?  
        return postProcessResult(result, connToUse, existingConnection);  
    } finally {  
        if (!enableTransactionSupport) {  
            RedisConnectionUtils.releaseConnection(conn, factory);  
        }  
    }  
}

    這里面每次執行action.doInRedis(connToExpose)前都要調用RedisConnectionUtils.getConnection(factory);獲得一個連接，進入RedisConnnectionUtils類中，getConnection(factory)最終調用的是doGetConnection(factory, true, false, enableTranactionSupport)這個函數。

這個函數我們可以看下api文檔，發現實際上並不是真的創建一個新的redis連接，它只是在connectFactory中獲取一個連接，也就是從連接池中取出一個連接。當然如果connectFactory沒有連接可用，此時如果allowCreate=true便會創建出一個新的連接，並且加入到connectFactory中。

    這樣就可以放心大膽的使用，而不用擔心性能問題了。。。