關於spring-data-redis使用中資源耗盡的問題（Could not get a resource from the pool）

前段時間公司的項目運行一段時間后出現宕機狀態，靜態頁面雖能打開，但是請求都無法成功。

 

查看日志，發現請求卡在Opening RedisConnection就不往下走了

看代碼，攔截器中有做redis操作，而不知為何redis操作不往下走了

 

查看源碼，jedis沒有配置最大等待時間，而默認配置  blockWhenExhausted=true ，獲取不到資源會一直阻塞等待

        PooledObject<T> p = null;

        // Get local copy of current config so it is consistent for entire
        // method execution
        //默認配置為true，資源耗盡阻塞
        final boolean blockWhenExhausted = getBlockWhenExhausted();

        boolean create;
        final long waitTime = System.currentTimeMillis();

        while (p == null) {
            create = false;
            p = idleObjects.pollFirst();//從空閑隊列彈出PooledObject
            if (p == null) {
                //如果為空，則創建，如果超過最大數，則返回空
                p = create();
                if (p != null) {
                    create = true;
                }
            }
            if (blockWhenExhausted) {
                if (p == null) {
                    if (borrowMaxWaitMillis < 0) {
                        //如果沒有配置maxWaitMillis,則去idleObjects等待資源，如果沒有空閑資源就阻塞一直等待
                        p = idleObjects.takeFirst();
                    } else {
                        //如果配置了maxWaitMillis，則超時返回
                        p = idleObjects.pollFirst(borrowMaxWaitMillis,
                                TimeUnit.MILLISECONDS);
                    }
                }
                if (p == null) {
                    throw new NoSuchElementException(
                            "Timeout waiting for idle object");
                }
            } else {
                if (p == null) {
                    throw new NoSuchElementException("Pool exhausted");
                }
            }
 
        }                                                             

 

於是增加配置

<property name="maxWaitMillis" value="3000"/>

改了后，這回項目不會阻塞了，但是運行一段時間后，會頻繁的報錯，Could not get a resource from the pool

去網上找了一大圈都不靠譜，還是得自己調試找原因

想想項目中使用redis的情況，感覺一切都很正常，唯一有點值得注意的是

<property name="enableTransactionSupport" value="true" />

 

打斷點進源碼里面，發現 releaseConnection 方法中，連接沒有進行釋放

public static void releaseConnection(RedisConnection conn, RedisConnectionFactory factory) {

        if (conn == null) {
            return;
        }

        RedisConnectionHolder connHolder = (RedisConnectionHolder) TransactionSynchronizationManager.getResource(factory);

        if (connHolder != null && connHolder.isTransactionSyncronisationActive()) {
            if (log.isDebugEnabled()) {
                log.debug("Redis Connection will be closed when transaction finished.");
            }
            return;
        }

        // release transactional/read-only and non-transactional/non-bound connections.
        // transactional connections for read-only transactions get no synchronizer registered
        //如果配置了enableTransactionSupport=true，以下條件都不滿足，連接沒有釋放
        if (isConnectionTransactional(conn, factory)
                && TransactionSynchronizationManager.isCurrentTransactionReadOnly()) {
            unbindConnection(factory);
        } else if (!isConnectionTransactional(conn, factory)) {
            if (log.isDebugEnabled()) {
                log.debug("Closing Redis Connection");
            }
            conn.close();
        }
    }    

 

於是idleobjects的size一直為0，pool會新建PooledObject，等到一段時間后，達到最大資源數，便無法從pool中獲取到資源

 

嘗試手動釋放資源，果然就可以了

public boolean hasKey(final String key) {
        try {
            return redisTemplate.hasKey(key);
        } finally {
　　　　　　  //釋放連接
            RedisConnectionUtils.unbindConnection(redisTemplate.getConnectionFactory());
        }
    }

 

參考

(中文)  http://www.cnblogs.com/qijiang/p/5626461.html 

(原文)  https://www.javaworld.com/article/3062899/big-data/lightning-fast-nosql-with-spring-data-redis.html?page=2