1.keepAlive官方解读
| keepAlive | false （1.0.28） |
连接池中的minIdle数量以内的连接，空闲时间超过minEvictableIdleTimeMillis，则会执行keepAlive操作。 |
2.这个参数是严格保证连接池里的连接都是存活的，但其实不止官方解读那一个地方
DruidDataSource.init方法，keepAlive前面,如果没有设置异步，设置了初始化参数，就会初始化连接，而且接着启动创建连接线程,连接池的连接数量未达到配置的最小连接数，会继续创建的，后面又去做keepAlive判断，
我觉得加个这个判断是再次检查之前创建的连接是存活的，
if (createScheduler != null && asyncInit) { for (int i = 0; i < initialSize; ++i) { submitCreateTask(true); } } else if (!asyncInit) { // init connections while (poolingCount < initialSize) { try { PhysicalConnectionInfo pyConnectInfo = createPhysicalConnection(); DruidConnectionHolder holder = new DruidConnectionHolder(this, pyConnectInfo); connections[poolingCount++] = holder; } catch (SQLException ex) { LOG.error("init datasource error, url: " + this.getUrl(), ex); if (initExceptionThrow) { connectError = ex; break; } else { Thread.sleep(3000); } } } if (poolingCount > 0) { poolingPeak = poolingCount; poolingPeakTime = System.currentTimeMillis(); } } createAndLogThread(); createAndStartCreatorThread(); createAndStartDestroyThread(); initedLatch.await(); init = true; initedTime = new Date(); registerMbean(); if (connectError != null && poolingCount == 0) { throw connectError; } if (keepAlive) { // async fill to minIdle if (createScheduler != null) { for (int i = 0; i < minIdle; ++i) { submitCreateTask(true); } } else { this.emptySignal(); } }
额外提两点
1.连接池为什么要有initialSize参数，去初始化连接，后面又去启动创建连接的线程，假设连接initialSize为0，这个线程就会去创建连接达到最小连接数；我做了下实验，初步得出个结论，因为创建连接的线程，去创建连接达到最小连接数，是没有办法保证时间的，假设当下连接池达到最小连接数，连接又被拿完，剩下的线程是不是只有等待了，initialSize这个值也是根据使用方的流量设置的，也就是大部分时候initialSize的数量连接是够用的，那么也就是说只有第一次初始化的时候比较慢，之后获取连接都比较快，不会有波动
不设置initialSize，KeepAliveTest运行结果,可以看出创建连接的线程，去创建连接达到最小连接数，是没有办法保证时间的
dataSource.setPoolPreparedStatements(true); dataSource.setMinIdle(10); dataSource.setMaxActive(20); // dataSource.setMinEvictableIdleTimeMillis(30000); // dataSource.setMaxEvictableIdleTimeMillis(30000); dataSource.setTimeBetweenEvictionRunsMillis(10); dataSource.setFilters("log4j"); dataSource.setValidationQuery("select 1"); Properties properties = new Properties(); properties.put("druid.keepAlive", "true"); dataSource.configFromPropety(properties);
2022-05-19 00:20:33,198 [INFO ] ClickHouseDriver:42 - Driver registered 2022-05-19 00:20:33,704 [INFO ] DruidDataSource:995 - {dataSource-1} inited poolingCount : 0 poolingCount : 0 poolingCount : 0 poolingCount : 0 poolingCount : 0 poolingCount : 0 poolingCount : 0 poolingCount : 0 poolingCount : 0 poolingCount : 0 poolingCount : 0 poolingCount : 0 poolingCount : 0 poolingCount : 0 poolingCount : 0 poolingCount : 0 poolingCount : 0 poolingCount : 0 poolingCount : 0 poolingCount : 0 poolingCount : 0 poolingCount : 0 poolingCount : 0 poolingCount : 0 poolingCount : 0 poolingCount : 0 poolingCount : 0 poolingCount : 0 poolingCount : 0 poolingCount : 0 poolingCount : 0 poolingCount : 0 poolingCount : 0 poolingCount : 0 poolingCount : 0 poolingCount : 0 2022-05-19 00:20:34,254 [DEBUG] Connection:132 - {conn-10001,procId-128} connected poolingCount : 0 2022-05-19 00:20:34,274 [DEBUG] Statement:137 - {conn-10001, stmt-20000} created poolingCount : 0 poolingCount : 0 poolingCount : 0 2022-05-19 00:20:34,321 [DEBUG] Statement:137 - {conn-10001, stmt-20000, rs-50000} query executed. 26.8684 millis. select 1 2022-05-19 00:20:34,321 [DEBUG] ResultSet:142 - {conn-10001, stmt-20000, rs-50000} open poolingCount : 0 poolingCount : 0 poolingCount : 0 2022-05-19 00:20:34,392 [DEBUG] ResultSet:142 - {conn-10001, stmt-20000, rs-50000} Header: [1] 2022-05-19 00:20:34,393 [DEBUG] ResultSet:142 - {conn-10001, stmt-20000, rs-50000} closed 2022-05-19 00:20:34,393 [DEBUG] Statement:137 - {conn-10001, stmt-20000} closed poolingCount : 0 poolingCount : 1 2022-05-19 00:20:34,423 [DEBUG] Connection:132 - {conn-10002,procId-129} connected 2022-05-19 00:20:34,424 [DEBUG] Statement:137 - {conn-10002, stmt-20001} created 2022-05-19 00:20:34,424 [DEBUG] Statement:137 - {conn-10002, stmt-20001, rs-50001} query executed. 0.5225 millis. select 1 2022-05-19 00:20:34,424 [DEBUG] ResultSet:142 - {conn-10002, stmt-20001, rs-50001} open 2022-05-19 00:20:34,424 [DEBUG] ResultSet:142 - {conn-10002, stmt-20001, rs-50001} Header: [1] 2022-05-19 00:20:34,425 [DEBUG] ResultSet:142 - {conn-10002, stmt-20001, rs-50001} closed 2022-05-19 00:20:34,425 [DEBUG] Statement:137 - {conn-10002, stmt-20001} closed 2022-05-19 00:20:34,430 [DEBUG] Connection:132 - {conn-10003,procId-130} connected 2022-05-19 00:20:34,431 [DEBUG] Statement:137 - {conn-10003, stmt-20002} created 2022-05-19 00:20:34,431 [DEBUG] Statement:137 - {conn-10003, stmt-20002, rs-50002} query executed. 0.4103 millis. select 1 2022-05-19 00:20:34,431 [DEBUG] ResultSet:142 - {conn-10003, stmt-20002, rs-50002} open 2022-05-19 00:20:34,431 [DEBUG] ResultSet:142 - {conn-10003, stmt-20002, rs-50002} Header: [1] 2022-05-19 00:20:34,431 [DEBUG] ResultSet:142 - {conn-10003, stmt-20002, rs-50002} closed 2022-05-19 00:20:34,431 [DEBUG] Statement:137 - {conn-10003, stmt-20002} closed 2022-05-19 00:20:34,437 [DEBUG] Connection:132 - {conn-10004,procId-131} connected 2022-05-19 00:20:34,438 [DEBUG] Statement:137 - {conn-10004, stmt-20003} created 2022-05-19 00:20:34,438 [DEBUG] Statement:137 - {conn-10004, stmt-20003, rs-50003} query executed. 0.3958 millis. select 1 2022-05-19 00:20:34,438 [DEBUG] ResultSet:142 - {conn-10004, stmt-20003, rs-50003} open 2022-05-19 00:20:34,438 [DEBUG] ResultSet:142 - {conn-10004, stmt-20003, rs-50003} Header: [1] 2022-05-19 00:20:34,438 [DEBUG] ResultSet:142 - {conn-10004, stmt-20003, rs-50003} closed poolingCount : 3 2022-05-19 00:20:34,439 [DEBUG] Statement:137 - {conn-10004, stmt-20003} closed 2022-05-19 00:20:34,444 [DEBUG] Connection:132 - {conn-10005,procId-132} connected 2022-05-19 00:20:34,444 [DEBUG] Statement:137 - {conn-10005, stmt-20004} created 2022-05-19 00:20:34,445 [DEBUG] Statement:137 - {conn-10005, stmt-20004, rs-50004} query executed. 0.5292 millis. select 1 2022-05-19 00:20:34,445 [DEBUG] ResultSet:142 - {conn-10005, stmt-20004, rs-50004} open 2022-05-19 00:20:34,445 [DEBUG] ResultSet:142 - {conn-10005, stmt-20004, rs-50004} Header: [1] 2022-05-19 00:20:34,446 [DEBUG] ResultSet:142 - {conn-10005, stmt-20004, rs-50004} closed 2022-05-19 00:20:34,446 [DEBUG] Statement:137 - {conn-10005, stmt-20004} closed 2022-05-19 00:20:34,451 [DEBUG] Connection:132 - {conn-10006,procId-133} connected 2022-05-19 00:20:34,451 [DEBUG] Statement:137 - {conn-10006, stmt-20005} created 2022-05-19 00:20:34,452 [DEBUG] Statement:137 - {conn-10006, stmt-20005, rs-50005} query executed. 0.4187 millis. select 1 2022-05-19 00:20:34,452 [DEBUG] ResultSet:142 - {conn-10006, stmt-20005, rs-50005} open 2022-05-19 00:20:34,452 [DEBUG] ResultSet:142 - {conn-10006, stmt-20005, rs-50005} Header: [1] 2022-05-19 00:20:34,452 [DEBUG] ResultSet:142 - {conn-10006, stmt-20005, rs-50005} closed 2022-05-19 00:20:34,452 [DEBUG] Statement:137 - {conn-10006, stmt-20005} closed poolingCount : 6 2022-05-19 00:20:34,456 [DEBUG] Connection:132 - {conn-10007,procId-134} connected 2022-05-19 00:20:34,456 [DEBUG] Statement:137 - {conn-10007, stmt-20006} created 2022-05-19 00:20:34,457 [DEBUG] Statement:137 - {conn-10007, stmt-20006, rs-50006} query executed. 0.7669 millis. select 1 2022-05-19 00:20:34,457 [DEBUG] ResultSet:142 - {conn-10007, stmt-20006, rs-50006} open 2022-05-19 00:20:34,457 [DEBUG] ResultSet:142 - {conn-10007, stmt-20006, rs-50006} Header: [1] 2022-05-19 00:20:34,457 [DEBUG] ResultSet:142 - {conn-10007, stmt-20006, rs-50006} closed 2022-05-19 00:20:34,457 [DEBUG] Statement:137 - {conn-10007, stmt-20006} closed 2022-05-19 00:20:34,462 [DEBUG] Connection:132 - {conn-10008,procId-135} connected 2022-05-19 00:20:34,463 [DEBUG] Statement:137 - {conn-10008, stmt-20007} created 2022-05-19 00:20:34,463 [DEBUG] Statement:137 - {conn-10008, stmt-20007, rs-50007} query executed. 0.4346 millis. select 1 2022-05-19 00:20:34,463 [DEBUG] ResultSet:142 - {conn-10008, stmt-20007, rs-50007} open 2022-05-19 00:20:34,464 [DEBUG] ResultSet:142 - {conn-10008, stmt-20007, rs-50007} Header: [1] 2022-05-19 00:20:34,464 [DEBUG] ResultSet:142 - {conn-10008, stmt-20007, rs-50007} closed 2022-05-19 00:20:34,464 [DEBUG] Statement:137 - {conn-10008, stmt-20007} closed 2022-05-19 00:20:34,468 [DEBUG] Connection:132 - {conn-10009,procId-136} connected 2022-05-19 00:20:34,469 [DEBUG] Statement:137 - {conn-10009, stmt-20008} created 2022-05-19 00:20:34,469 [DEBUG] Statement:137 - {conn-10009, stmt-20008, rs-50008} query executed. 0.503 millis. select 1 2022-05-19 00:20:34,469 [DEBUG] ResultSet:142 - {conn-10009, stmt-20008, rs-50008} open poolingCount : 8
2.连接池一开始初始化大小就为最大连接数的大小，后面如果创建连接就不需要扩容，这可能是Druid性能高的一个原因，相比遍历连接池，去做操作，消耗的时间，在当下这个cpu性能，根本不算什么;而扩容消耗的内存以及后续可能引发的gc代价就比较大了
connections = new DruidConnectionHolder[maxActive]; evictConnections = new DruidConnectionHolder[maxActive]; keepAliveConnections = new DruidConnectionHolder[maxActive];
3.keepAlive还是比较严格,shrink也有判断，假设连接池存活数量小于最小连接数，就要通知创建连接线程去创建连接
public void shrink(boolean checkTime, boolean keepAlive) { try { lock.lockInterruptibly(); } catch (InterruptedException e) { return; } boolean needFill = false; int evictCount = 0; int keepAliveCount = 0; int fatalErrorIncrement = fatalErrorCount - fatalErrorCountLastShrink; fatalErrorCountLastShrink = fatalErrorCount; try { if (!inited) { return; } final int checkCount = poolingCount - minIdle; final long currentTimeMillis = System.currentTimeMillis(); for (int i = 0; i < poolingCount; ++i) { DruidConnectionHolder connection = connections[i]; if ((onFatalError || fatalErrorIncrement > 0) && (lastFatalErrorTimeMillis > connection.connectTimeMillis)) { keepAliveConnections[keepAliveCount++] = connection; continue; } if (checkTime) { if (phyTimeoutMillis > 0) { long phyConnectTimeMillis = currentTimeMillis - connection.connectTimeMillis; if (phyConnectTimeMillis > phyTimeoutMillis) { evictConnections[evictCount++] = connection; continue; } } long idleMillis = currentTimeMillis - connection.lastActiveTimeMillis; if (idleMillis < minEvictableIdleTimeMillis && idleMillis < keepAliveBetweenTimeMillis ) { break; } if (idleMillis >= minEvictableIdleTimeMillis) { if (checkTime && i < checkCount) { evictConnections[evictCount++] = connection; continue; } else if (idleMillis > maxEvictableIdleTimeMillis) { evictConnections[evictCount++] = connection; continue; } } if (keepAlive && idleMillis >= keepAliveBetweenTimeMillis) { keepAliveConnections[keepAliveCount++] = connection; } } else { if (i < checkCount) { evictConnections[evictCount++] = connection; } else { break; } } } int removeCount = evictCount + keepAliveCount; if (removeCount > 0) { System.arraycopy(connections, removeCount, connections, 0, poolingCount - removeCount); Arrays.fill(connections, poolingCount - removeCount, poolingCount, null); poolingCount -= removeCount; } keepAliveCheckCount += keepAliveCount; if (keepAlive && poolingCount + activeCount < minIdle) { needFill = true; } } finally { lock.unlock(); } if (evictCount > 0) { for (int i = 0; i < evictCount; ++i) { DruidConnectionHolder item = evictConnections[i]; Connection connection = item.getConnection(); JdbcUtils.close(connection); destroyCountUpdater.incrementAndGet(this); } Arrays.fill(evictConnections, null); } if (keepAliveCount > 0) { // keep order for (int i = keepAliveCount - 1; i >= 0; --i) { DruidConnectionHolder holer = keepAliveConnections[i]; Connection connection = holer.getConnection(); holer.incrementKeepAliveCheckCount(); boolean validate = false; try { this.validateConnection(connection); validate = true; } catch (Throwable error) { if (LOG.isDebugEnabled()) { LOG.debug("keepAliveErr", error); } // skip } boolean discard = !validate; if (validate) { holer.lastKeepTimeMillis = System.currentTimeMillis(); boolean putOk = put(holer, 0L, true); if (!putOk) { discard = true; } } if (discard) { try { connection.close(); } catch (Exception e) { // skip } lock.lock(); try { discardCount++; if (activeCount + poolingCount <= minIdle) { emptySignal(); } } finally { lock.unlock(); } } } this.getDataSourceStat().addKeepAliveCheckCount(keepAliveCount); Arrays.fill(keepAliveConnections, null); } if (needFill) { lock.lock(); try { int fillCount = minIdle - (activeCount + poolingCount + createTaskCount); for (int i = 0; i < fillCount; ++i) { emptySignal(); } } finally { lock.unlock(); } } else if (onFatalError || fatalErrorIncrement > 0) { lock.lock(); try { emptySignal(); } finally { lock.unlock(); } } }
CreateConnectionThread.run也会检查活跃
if (emptyWait) {
// 必须存在线程等待，才创建连接
if (poolingCount >= notEmptyWaitThreadCount //
&& (!(keepAlive && activeCount + poolingCount < minIdle))
&& !isFailContinuous()
) {
empty.await();
}
// 防止创建超过maxActive数量的连接
if (activeCount + poolingCount >= maxActive) {
empty.await();
continue;
}
}
