private DruidPooledConnection getConnectionInternal(long maxWait) throws SQLException {        if (closed) {            connectErrorCountUpdater.incrementAndGet(this);            throw new DataSourceClosedException("dataSource already closed at " + new Date(closeTimeMillis));        }
        if (!enable) {            connectErrorCountUpdater.incrementAndGet(this);
            if (disableException != null) {                throw disableException;            }
            throw new DataSourceDisableException();        }
        final long nanos = TimeUnit.MILLISECONDS.toNanos(maxWait);        final int maxWaitThreadCount = this.maxWaitThreadCount;
        DruidConnectionHolder holder;    // createDirect只是针对createScheduler(创建连接的线程池)进行处理        for (boolean createDirect = false;;) {            if (createDirect) {                createStartNanosUpdater.set(this, System.nanoTime());                if (creatingCountUpdater.compareAndSet(this, 0, 1)) {                    PhysicalConnectionInfo pyConnInfo = DruidDataSource.this.createPhysicalConnection();                    holder = new DruidConnectionHolder(this, pyConnInfo);                    holder.lastActiveTimeMillis = System.currentTimeMillis();
                    creatingCountUpdater.decrementAndGet(this);                    directCreateCountUpdater.incrementAndGet(this);
                    if (LOG.isDebugEnabled()) {                        LOG.debug("conn-direct_create ");                    }
                    boolean discard = false;                    lock.lock();                    try {                        if (activeCount < maxActive) {                            activeCount++;                            holder.active = true;                            if (activeCount > activePeak) {                                activePeak = activeCount;                                activePeakTime = System.currentTimeMillis();                            }                            break;                        } else {                            discard = true;                        }                    } finally {                        lock.unlock();                    }
                    if (discard) {                        JdbcUtils.close(pyConnInfo.getPhysicalConnection());                    }                }            }
            try {                lock.lockInterruptibly();            } catch (InterruptedException e) {                connectErrorCountUpdater.incrementAndGet(this);                throw new SQLException("interrupt", e);            }            // 如果等待创建连接的线程数如果大于maxWaitThreadCount，抛出异常，这个notEmptyWaitThreadCount是在pollLast(nanos)和takeLast()中设置
            try {                if (maxWaitThreadCount > 0                        && notEmptyWaitThreadCount >= maxWaitThreadCount) {                    connectErrorCountUpdater.incrementAndGet(this);                    throw new SQLException("maxWaitThreadCount " + maxWaitThreadCount + ", current wait Thread count "                            + lock.getQueueLength());                }
                if (onFatalError                        && onFatalErrorMaxActive > 0                        && activeCount >= onFatalErrorMaxActive) {                    connectErrorCountUpdater.incrementAndGet(this);
                    StringBuilder errorMsg = new StringBuilder();                    errorMsg.append("onFatalError, activeCount ")                            .append(activeCount)                            .append(", onFatalErrorMaxActive ")                            .append(onFatalErrorMaxActive);
                    if (lastFatalErrorTimeMillis > 0) {                        errorMsg.append(", time '")                                .append(StringUtils.formatDateTime19(                                        lastFatalErrorTimeMillis, TimeZone.getDefault()))                                .append("'");                    }
                    if (lastFatalErrorSql != null) {                        errorMsg.append(", sql \n")                                .append(lastFatalErrorSql);                    }
                    throw new SQLException(                            errorMsg.toString(), lastFatalError);                }
                connectCount++;
                if (createScheduler != null                        && poolingCount == 0                        && activeCount < maxActive                        && creatingCountUpdater.get(this) == 0                        && createScheduler instanceof ScheduledThreadPoolExecutor) {                    ScheduledThreadPoolExecutor executor = (ScheduledThreadPoolExecutor) createScheduler;                    if (executor.getQueue().size() > 0) {                        createDirect = true;                        continue;                    }                }
                if (maxWait > 0) {                    holder = pollLast(nanos);                } else {                    holder = takeLast();                }
                if (holder != null) {                    if (holder.discard) {                        continue;                    }
                    activeCount++;                    holder.active = true;                    if (activeCount > activePeak) {                        activePeak = activeCount;                        activePeakTime = System.currentTimeMillis();                    }                }            } catch (InterruptedException e) {                connectErrorCountUpdater.incrementAndGet(this);                throw new SQLException(e.getMessage(), e);            } catch (SQLException e) {                connectErrorCountUpdater.incrementAndGet(this);                throw e;            } finally {                lock.unlock();            }
            break;        }
        if (holder == null) {            long waitNanos = waitNanosLocal.get();
            final long activeCount;            final long maxActive;            final long creatingCount;            final long createStartNanos;            final long createErrorCount;            final Throwable createError;            try {                lock.lock();                activeCount = this.activeCount;                maxActive = this.maxActive;                creatingCount = this.creatingCount;                createStartNanos = this.createStartNanos;                createErrorCount = this.createErrorCount;                createError = this.createError;            } finally {                lock.unlock();            }
            StringBuilder buf = new StringBuilder(128);            buf.append("wait millis ")//               .append(waitNanos / (1000 * 1000))//               .append(", active ").append(activeCount)//               .append(", maxActive ").append(maxActive)//               .append(", creating ").append(creatingCount)//            ;            if (creatingCount > 0 && createStartNanos > 0) {                long createElapseMillis = (System.nanoTime() - createStartNanos) / (1000 * 1000);                if (createElapseMillis > 0) {                    buf.append(", createElapseMillis ").append(createElapseMillis);                }            }
            if (createErrorCount > 0) {                buf.append(", createErrorCount ").append(createErrorCount);            }
            List<JdbcSqlStatValue> sqlList = this.getDataSourceStat().getRuningSqlList();            for (int i = 0; i < sqlList.size(); ++i) {                if (i != 0) {                    buf.append('\n');                } else {                    buf.append(", ");                }                JdbcSqlStatValue sql = sqlList.get(i);                buf.append("runningSqlCount ").append(sql.getRunningCount());                buf.append(" : ");                buf.append(sql.getSql());            }
            String errorMessage = buf.toString();
            if (createError != null) {                throw new GetConnectionTimeoutException(errorMessage, createError);            } else {                throw new GetConnectionTimeoutException(errorMessage);            }        }
        holder.incrementUseCount();
        DruidPooledConnection poolalbeConnection = new DruidPooledConnection(holder);        return poolalbeConnection;}