关于spring-data-redis使用中资源耗尽的问题（Could not get a resource from the pool）

前段时间公司的项目运行一段时间后出现宕机状态，静态页面虽能打开，但是请求都无法成功。

 

查看日志，发现请求卡在Opening RedisConnection就不往下走了

看代码，拦截器中有做redis操作，而不知为何redis操作不往下走了

 

查看源码，jedis没有配置最大等待时间，而默认配置  blockWhenExhausted=true ，获取不到资源会一直阻塞等待

        PooledObject<T> p = null;

        // Get local copy of current config so it is consistent for entire
        // method execution
        //默认配置为true，资源耗尽阻塞
        final boolean blockWhenExhausted = getBlockWhenExhausted();

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

        while (p == null) {
            create = false;
            p = idleObjects.pollFirst();//从空闲队列弹出PooledObject
            if (p == null) {
                //如果为空，则创建，如果超过最大数，则返回空
                p = create();
                if (p != null) {
                    create = true;
                }
            }
            if (blockWhenExhausted) {
                if (p == null) {
                    if (borrowMaxWaitMillis < 0) {
                        //如果没有配置maxWaitMillis,则去idleObjects等待资源，如果没有空闲资源就阻塞一直等待
                        p = idleObjects.takeFirst();
                    } else {
                        //如果配置了maxWaitMillis，则超时返回
                        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");
                }
            }
 
        }                                                             

 

于是增加配置

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

改了后，这回项目不会阻塞了，但是运行一段时间后，会频繁的报错，Could not get a resource from the pool

去网上找了一大圈都不靠谱，还是得自己调试找原因

想想项目中使用redis的情况，感觉一切都很正常，唯一有点值得注意的是

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

 

打断点进源码里面，发现 releaseConnection 方法中，连接没有进行释放

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，以下条件都不满足，连接没有释放
        if (isConnectionTransactional(conn, factory)
                && TransactionSynchronizationManager.isCurrentTransactionReadOnly()) {
            unbindConnection(factory);
        } else if (!isConnectionTransactional(conn, factory)) {
            if (log.isDebugEnabled()) {
                log.debug("Closing Redis Connection");
            }
            conn.close();
        }
    }    

 

于是idleobjects的size一直为0，pool会新建PooledObject，等到一段时间后，达到最大资源数，便无法从pool中获取到资源

 

尝试手动释放资源，果然就可以了

public boolean hasKey(final String key) {
        try {
            return redisTemplate.hasKey(key);
        } finally {
　　　　　　  //释放连接
            RedisConnectionUtils.unbindConnection(redisTemplate.getConnectionFactory());
        }
    }

 

参考

(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