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简介
上文中分析了数据库连接池的初始化部分，接下来我们来看看获取连接部分的代码
数据库连接池中连接获取
下面的相关的代码，在代码中加了自己的相关注释：
public DruidPooledConnection getConnection(long maxWaitMillis) throws SQLException {
// 上文分析过的初始化
init();
// 由于没有配置 filter，直接走：getConnectionDirect
if (filters.size() > 0) {
FilterChainImpl filterChain = new FilterChainImpl(this);
return filterChain.dataSource_connect(this, maxWaitMillis);
} else {
return getConnectionDirect(maxWaitMillis);
}
}
public DruidPooledConnection getConnectionDirect(long maxWaitMillis) throws SQLException {
int notFullTimeoutRetryCnt = 0;
for (;;) {
// handle notFullTimeoutRetry
DruidPooledConnection poolableConnection;
try {
// 获取连接，具体后面再看
poolableConnection = getConnectionInternal(maxWaitMillis);
} catch (GetConnectionTimeoutException ex) {
if (notFullTimeoutRetryCnt <= this.notFullTimeoutRetryCount && !isFull()) {
notFullTimeoutRetryCnt++;
if (LOG.isWarnEnabled()) {
LOG.warn("get connection timeout retry : " + notFullTimeoutRetryCnt);
}
continue;
}
throw ex;
}
// 下面看意思是做了一些连接有效性的检查
// 无效的就跳过这次，重新去获取一次
if (testOnBorrow) {
boolean validate = testConnectionInternal(poolableConnection.holder, poolableConnection.conn);
if (!validate) {
if (LOG.isDebugEnabled()) {
LOG.debug("skip not validate connection.");
}
discardConnection(poolableConnection.holder);
continue;
}
} else {
if (poolableConnection.conn.isClosed()) {
discardConnection(poolableConnection.holder); // 传入null，避免重复关闭
continue;
}
// 这段感觉有段阻塞超时等待的感觉，留待确认
if (testWhileIdle) {
final DruidConnectionHolder holder = poolableConnection.holder;
long currentTimeMillis = System.currentTimeMillis();
long lastActiveTimeMillis = holder.lastActiveTimeMillis;
long lastExecTimeMillis = holder.lastExecTimeMillis;
long lastKeepTimeMillis = holder.lastKeepTimeMillis;
if (checkExecuteTime
&& lastExecTimeMillis != lastActiveTimeMillis) {
lastActiveTimeMillis = lastExecTimeMillis;
}
if (lastKeepTimeMillis > lastActiveTimeMillis) {
lastActiveTimeMillis = lastKeepTimeMillis;
}
long idleMillis = currentTimeMillis - lastActiveTimeMillis;
long timeBetweenEvictionRunsMillis = this.timeBetweenEvictionRunsMillis;
if (timeBetweenEvictionRunsMillis <= 0) {
timeBetweenEvictionRunsMillis = DEFAULT_TIME_BETWEEN_EVICTION_RUNS_MILLIS;
}
if (idleMillis >= timeBetweenEvictionRunsMillis
|| idleMillis < 0 // unexcepted branch
) {
boolean validate = testConnectionInternal(poolableConnection.holder, poolableConnection.conn);
if (!validate) {
if (LOG.isDebugEnabled()) {
LOG.debug("skip not validate connection.");
}
discardConnection(poolableConnection.holder);
continue;
}
}
}
}
// 最后的收尾，标识位设置之类的
if (removeAbandoned) {
StackTraceElement[] stackTrace = Thread.currentThread().getStackTrace();
poolableConnection.connectStackTrace = stackTrace;
poolableConnection.setConnectedTimeNano();
poolableConnection.traceEnable = true;
activeConnectionLock.lock();
try {
activeConnections.put(poolableConnection, PRESENT);
} finally {
activeConnectionLock.unlock();
}
}
if (!this.defaultAutoCommit) {
poolableConnection.setAutoCommit(false);
}
return poolableConnection;
}
}
private DruidPooledConnection getConnectionInternal(long maxWait) throws SQLException {
// 下面这两段看着是数据库关闭或者不可用触发
// 如果数据库恢复重启，是那段代码去重置这些标识位的，后面去看下
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;
for (boolean createDirect = false;;) {
// 直接生成新的数据库连接
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 ");
}
// 下面检测了现有活跃的连接数与配置的最大获取数
// 如果小于则统计增加
// 其他则，有close操作，感觉不应该是关闭当前连接，可能是其他一些可关闭的连接，具体的后面再看看
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);
}
try {
// 一些最大等待线程限制？
// 下面这两段if没太能理解其含义......
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++;
// 这一点检测后就跳到了直接生成新的物理连接
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;
}
}
// 下面的都是从connections里面去去连接
// 但让人疑惑的是在createDirect和其相关的代码中，没有看到放入connection的相关操作
// 后面再确认下这块的获取逻辑
if (maxWait > 0) {
holder = pollLast(nanos);
} else {
holder = takeLast();
}
// 一些统计设置
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;
}
// 有点像阻塞等待打印一些信息
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;
}
复制代码总结
结合以前的阅读，我们得到：
- 1.初始化的时候，设置了配置的初始化数量的连接
- 2.获取时从一个数据库连接池中获取
- 3.没有空闲的连接时，会再次生产新的数据库物理连接
但我们目前没有明确找到生产新的物理数据库连接放入数据的操作，还有如果当前连接数大于配置的最大连接数时具体处理
后面还需要进行探索
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