Druid源码之removeAbandanded

1.官方解释

当程序存在缺陷时，申请的连接忘记关闭，这时候，就存在连接泄漏了。Druid提供了RemoveAbandanded相关配置，用来关闭长时间不使用的连接。RemoveAbandanded功能不建议在生产环境中使用，仅用于连接泄露检测诊断

参数	说明
removeAbandoned	如果连接泄露，是否需要回收泄露的连接，默认false；
logAbandoned	如果回收了泄露的连接，是否要打印一条log，默认false；
removeAbandonedTimeoutMillis	连接回收的超时时间，默认5分钟；

https://github.com/alibaba/druid/wiki/%E8%BF%9E%E6%8E%A5%E6%B3%84%E6%BC%8F%E7%9B%91%E6%B5%8B

2.Druid的1.2.9_preview_01源码，你如果没有配置destroyScheduler，除非你手动调用removeAbandoned()，不然加了配置也没用，调用这个方法，是连接创建到现在的时间如果大于

removeAbandonedTimeoutMillis，就会把活跃连接直接关闭了；不过要注意只有的连接的disable为false才会把会把活跃连接直接关闭掉，不然跳过

    protected void createAndStartDestroyThread() {
        destroyTask = new DestroyTask();

        if (destroyScheduler != null) {
            long period = timeBetweenEvictionRunsMillis;
            if (period <= 0) {
                period = 1000;
            }
            destroySchedulerFuture = destroyScheduler.scheduleAtFixedRate(destroyTask, period, period,
                                                                          TimeUnit.MILLISECONDS);
            initedLatch.countDown();
            return;
        }

        String threadName = "Druid-ConnectionPool-Destroy-" + System.identityHashCode(this);
        destroyConnectionThread = new DestroyConnectionThread(threadName);
        destroyConnectionThread.start();
    }    
public class DestroyTask implements Runnable {
        public DestroyTask() {

        }

        @Override
        public void run() {
            shrink(true, keepAlive);

            if (isRemoveAbandoned()) {
                removeAbandoned();
            }
        }

    }

public int removeAbandoned() {
        int removeCount = 0;

        long currrentNanos = System.nanoTime();

        List<DruidPooledConnection> abandonedList = new ArrayList<DruidPooledConnection>();

        activeConnectionLock.lock();
        try {
            Iterator<DruidPooledConnection> iter = activeConnections.keySet().iterator();

            for (; iter.hasNext();) {
                DruidPooledConnection pooledConnection = iter.next();

                if (pooledConnection.isRunning()) {
                    continue;
                }

                long timeMillis = (currrentNanos - pooledConnection.getConnectedTimeNano()) / (1000 * 1000);

                if (timeMillis >= removeAbandonedTimeoutMillis) {
                    iter.remove();
                    pooledConnection.setTraceEnable(false);
                    abandonedList.add(pooledConnection);
                }
            }
        } finally {
            activeConnectionLock.unlock();
        }

        if (abandonedList.size() > 0) {
            for (DruidPooledConnection pooledConnection : abandonedList) {
                final ReentrantLock lock = pooledConnection.lock;
                lock.lock();
                try {
                    if (pooledConnection.isDisable()) {
                        continue;
                    }
                } finally {
                    lock.unlock();
                }

                JdbcUtils.close(pooledConnection);
                pooledConnection.abandond();
                removeAbandonedCount++;
                removeCount++;

                if (isLogAbandoned()) {
                    StringBuilder buf = new StringBuilder();
                    buf.append("abandon connection, owner thread: ");
                    buf.append(pooledConnection.getOwnerThread().getName());
                    buf.append(", connected at : ");
                    buf.append(pooledConnection.getConnectedTimeMillis());
                    buf.append(", open stackTrace\n");

                    StackTraceElement[] trace = pooledConnection.getConnectStackTrace();
                    for (int i = 0; i < trace.length; i++) {
                        buf.append("\tat ");
                        buf.append(trace[i].toString());
                        buf.append("\n");
                    }

                    buf.append("ownerThread current state is " + pooledConnection.getOwnerThread().getState()
                               + ", current stackTrace\n");
                    trace = pooledConnection.getOwnerThread().getStackTrace();
                    for (int i = 0; i < trace.length; i++) {
                        buf.append("\tat ");
                        buf.append(trace[i].toString());
                        buf.append("\n");
                    }

                    LOG.error(buf.toString());
                }
            }
        }

        return removeCount;
    }

3.disable属性表示连接是不是被禁用,DruidDataSource.handleFatalError（）和DruidPooledConnection.close()方法会把这个属性置为true,而且DruidPooledXAConnection.close()调用了DruidPooledConnection.close()方法；

DruidPooledConnection.close()和DruidDataSource.removeAbandoned()会根据这个属性去判断要不要关闭连接，其他地方都没用到这个属性，当下还不知道这个的作用在哪里

DruidPooledConnection.close方法

public void close() throws SQLException {
        if (this.disable) {
            return;
        }

        DruidConnectionHolder holder = this.holder;
        if (holder == null) {
            if (dupCloseLogEnable) {
                LOG.error("dup close");
            }
            return;
        }

        DruidAbstractDataSource dataSource = holder.getDataSource();
        boolean isSameThread = this.getOwnerThread() == Thread.currentThread();

        if (!isSameThread) {
            dataSource.setAsyncCloseConnectionEnable(true);
        }

        if (dataSource.isAsyncCloseConnectionEnable()) {
            syncClose();
            return;
        }

        if (!CLOSING_UPDATER.compareAndSet(this, 0, 1)) {
            return;
        }

        try {
            for (ConnectionEventListener listener : holder.getConnectionEventListeners()) {
                listener.connectionClosed(new ConnectionEvent(this));
            }

            List<Filter> filters = dataSource.getProxyFilters();
            if (filters.size() > 0) {
                FilterChainImpl filterChain = new FilterChainImpl(dataSource);
                filterChain.dataSource_recycle(this);
            } else {
                recycle();
            }
        } finally {
            CLOSING_UPDATER.set(this, 0);
        }

        this.disable = true;
    }