序

本文主要研究在中途数据库挂的情况下，hikari与tomcat jdbc pool的fail fast情况。

实验代码

  @Testpublic void testDatabaseDownAndUp() throws SQLException, InterruptedException {LOGGER.info("begin to wait for database down and up");for(int c=0;c<10;c++){LOGGER.info("execute:"+(c+1));Connection conn = null;String sql = "select 1";PreparedStatement pstmt = null;try {long start = System.currentTimeMillis();conn = dataSource.getConnection();LOGGER.info("{} got connection,cost:{}",(c+1),System.currentTimeMillis() - start);pstmt = (PreparedStatement)conn.prepareStatement(sql);ResultSet rs = pstmt.executeQuery();int col = rs.getMetaData().getColumnCount();while (rs.next()) {for (int i = 1; i <= col; i++) {System.out.print(rs.getObject(i));}System.out.println("");}LOGGER.info("============================");} catch (Exception e) {e.printStackTrace();} finally {//close resourcesDbUtils.closeQuietly(pstmt);DbUtils.closeQuietly(conn);}TimeUnit.SECONDS.sleep(10);}}
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在第一次循环输出之后断开数据库连接，等个二三十秒再恢复。

hikari

2018-01-30 15:35:16.668  INFO 5852 --- [           main] c.e.demo.HikariDemoApplicationTests      : execute:1
2018-01-30 15:35:26.854  INFO 5852 --- [           main] c.e.demo.HikariDemoApplicationTests      : execute:2
2018-01-30 15:36:06.867  INFO 5852 --- [           main] c.e.demo.HikariDemoApplicationTests      : execute:3
2018-01-30 15:36:46.878  INFO 5852 --- [           main] c.e.demo.HikariDemoApplicationTests      : execute:4
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从这点来看，中途数据库断开的话，hikari会不断获取数据库链接

假设数据库一直没恢复，那么所以请求数据库操作的业务线程将都阻塞connectionTimeout的时间，这个会占用工作线程

hikari只有testOnBorrow功能，是直接一个while循环，在timeout时间内不断borrow连接，validate连接，validate成功才返回或者超时抛出SQLTransientConnectionException异常。borrow的超时时间为connectionTimeout，默认30秒。

validate不成功日志记录的异常

2018-01-31 16:45:00.653  WARN 6501 --- [           main] org.postgresql.jdbc.PgConnection         : Validating connection.org.postgresql.util.PSQLException: FATAL: terminating connection due to administrator commandat org.postgresql.core.v3.QueryExecutorImpl.receiveErrorResponse(QueryExecutorImpl.java:2422) ~[postgresql-42.2.1.jar:42.2.1]at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:2167) ~[postgresql-42.2.1.jar:42.2.1]at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:306) ~[postgresql-42.2.1.jar:42.2.1]at org.postgresql.jdbc.PgStatement.executeInternal(PgStatement.java:441) ~[postgresql-42.2.1.jar:42.2.1]at org.postgresql.jdbc.PgStatement.execute(PgStatement.java:365) ~[postgresql-42.2.1.jar:42.2.1]at org.postgresql.jdbc.PgPreparedStatement.executeWithFlags(PgPreparedStatement.java:155) ~[postgresql-42.2.1.jar:42.2.1]at org.postgresql.jdbc.PgPreparedStatement.executeUpdate(PgPreparedStatement.java:132) ~[postgresql-42.2.1.jar:42.2.1]at org.postgresql.jdbc.PgConnection.isValid(PgConnection.java:1364) ~[postgresql-42.2.1.jar:42.2.1]at com.zaxxer.hikari.pool.PoolBase.isConnectionAlive(PoolBase.java:160) [HikariCP-2.7.6.jar:na]at com.zaxxer.hikari.pool.HikariPool.getConnection(HikariPool.java:171) [HikariCP-2.7.6.jar:na]at com.zaxxer.hikari.pool.HikariPool.getConnection(HikariPool.java:147) [HikariCP-2.7.6.jar:na]at com.zaxxer.hikari.HikariDataSource.getConnection(HikariDataSource.java:123) [HikariCP-2.7.6.jar:na]at com.example.demo.HikariDemoApplicationTests.testDatabaseDownAndUp(HikariDemoApplicationTests.java:109) [test-classes/:na]at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_71]at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_71]at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_71]at java.lang.reflect.Method.invoke(Method.java:497) ~[na:1.8.0_71]at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50) [junit-4.12.jar:4.12]at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12) [junit-4.12.jar:4.12]at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47) [junit-4.12.jar:4.12]at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17) [junit-4.12.jar:4.12]at org.springframework.test.context.junit4.statements.RunBeforeTestExecutionCallbacks.evaluate(RunBeforeTestExecutionCallbacks.java:73) [spring-test-5.0.3.RELEASE.jar:5.0.3.RELEASE]at org.springframework.test.context.junit4.statements.RunAfterTestExecutionCallbacks.evaluate(RunAfterTestExecutionCallbacks.java:83) [spring-test-5.0.3.RELEASE.jar:5.0.3.RELEASE]at org.springframework.test.context.junit4.statements.RunBeforeTestMethodCallbacks.evaluate(RunBeforeTestMethodCallbacks.java:75) [spring-test-5.0.3.RELEASE.jar:5.0.3.RELEASE]at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate(RunAfterTestMethodCallbacks.java:86) [spring-test-5.0.3.RELEASE.jar:5.0.3.RELEASE]at org.springframework.test.context.junit4.statements.SpringRepeat.evaluate(SpringRepeat.java:84) [spring-test-5.0.3.RELEASE.jar:5.0.3.RELEASE]at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325) [junit-4.12.jar:4.12]at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:251) [spring-test-5.0.3.RELEASE.jar:5.0.3.RELEASE]at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:97) [spring-test-5.0.3.RELEASE.jar:5.0.3.RELEASE]at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290) [junit-4.12.jar:4.12]at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71) [junit-4.12.jar:4.12]at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288) [junit-4.12.jar:4.12]at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58) [junit-4.12.jar:4.12]at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268) [junit-4.12.jar:4.12]at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61) [spring-test-5.0.3.RELEASE.jar:5.0.3.RELEASE]at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:70) [spring-test-5.0.3.RELEASE.jar:5.0.3.RELEASE]at org.junit.runners.ParentRunner.run(ParentRunner.java:363) [junit-4.12.jar:4.12]at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:190) [spring-test-5.0.3.RELEASE.jar:5.0.3.RELEASE]at org.junit.runner.JUnitCore.run(JUnitCore.java:137) [junit-4.12.jar:4.12]at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:69) [junit-rt.jar:na]at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:234) [junit-rt.jar:na]at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:74) [junit-rt.jar:na]at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_71]at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_71]at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_71]at java.lang.reflect.Method.invoke(Method.java:497) ~[na:1.8.0_71]at com.intellij.rt.execution.application.AppMain.main(AppMain.java:144) [idea_rt.jar:na]
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假设在测试之前新建立好maxPoolSize的连接，那么执行之后中断数据库，则下一次的getConnection会挨个取出这些空闲连接，validate，validate失败会在log里头记录异常，同时getConnection继续循环获取连接

getConnection timeout抛出的异常

java.sql.SQLTransientConnectionException: demo1 - Connection is not available, request timed out after 60007ms.at com.zaxxer.hikari.pool.HikariPool.createTimeoutException(HikariPool.java:666)at com.zaxxer.hikari.pool.HikariPool.getConnection(HikariPool.java:182)at com.zaxxer.hikari.pool.HikariPool.getConnection(HikariPool.java:147)at com.zaxxer.hikari.HikariDataSource.getConnection(HikariDataSource.java:123)at com.example.demo.HikariDemoApplicationTests.testDatabaseDownAndUp(HikariDemoApplicationTests.java:98)at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)at java.lang.reflect.Method.invoke(Method.java:497)at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)at org.springframework.test.context.junit4.statements.RunBeforeTestExecutionCallbacks.evaluate(RunBeforeTestExecutionCallbacks.java:73)at org.springframework.test.context.junit4.statements.RunAfterTestExecutionCallbacks.evaluate(RunAfterTestExecutionCallbacks.java:83)at org.springframework.test.context.junit4.statements.RunBeforeTestMethodCallbacks.evaluate(RunBeforeTestMethodCallbacks.java:75)at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate(RunAfterTestMethodCallbacks.java:86)at org.springframework.test.context.junit4.statements.SpringRepeat.evaluate(SpringRepeat.java:84)at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:251)at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:97)at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:70)at org.junit.runners.ParentRunner.run(ParentRunner.java:363)at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:190)at org.junit.runner.JUnitCore.run(JUnitCore.java:137)at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:69)at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:234)at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:74)at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)at java.lang.reflect.Method.invoke(Method.java:497)at com.intellij.rt.execution.application.AppMain.main(AppMain.java:144)
Caused by: org.postgresql.util.PSQLException: Connection to 192.168.99.100:5432 refused. Check that the hostname and port are correct and that the postmaster is accepting TCP/IP connections.at org.postgresql.core.v3.ConnectionFactoryImpl.openConnectionImpl(ConnectionFactoryImpl.java:247)at org.postgresql.core.ConnectionFactory.openConnection(ConnectionFactory.java:49)at org.postgresql.jdbc.PgConnection.<init>(PgConnection.java:195)at org.postgresql.Driver.makeConnection(Driver.java:452)at org.postgresql.Driver.connect(Driver.java:254)at com.zaxxer.hikari.util.DriverDataSource.getConnection(DriverDataSource.java:117)at com.zaxxer.hikari.util.DriverDataSource.getConnection(DriverDataSource.java:123)at com.zaxxer.hikari.pool.PoolBase.newConnection(PoolBase.java:375)at com.zaxxer.hikari.pool.PoolBase.newPoolEntry(PoolBase.java:204)at com.zaxxer.hikari.pool.HikariPool.createPoolEntry(HikariPool.java:459)at com.zaxxer.hikari.pool.HikariPool.access$200(HikariPool.java:70)at com.zaxxer.hikari.pool.HikariPool$PoolEntryCreator.call(HikariPool.java:696)at com.zaxxer.hikari.pool.HikariPool$PoolEntryCreator.call(HikariPool.java:682)at java.util.concurrent.FutureTask.run(FutureTask.java:266)at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)at java.lang.Thread.run(Thread.java:745)
Caused by: java.net.ConnectException: Connection refusedat java.net.PlainSocketImpl.socketConnect(Native Method)at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350)at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206)at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188)at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)at java.net.Socket.connect(Socket.java:589)at org.postgresql.core.PGStream.<init>(PGStream.java:69)at org.postgresql.core.v3.ConnectionFactoryImpl.openConnectionImpl(ConnectionFactoryImpl.java:158)... 16 more
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循环获取连接超时，则抛出SQLTransientConnectionException

异步线程PoolEntryCreator补充新连接在日志记录的异常

2018-01-31 16:45:00.915  WARN 6501 --- [onnection adder] unknown.jul.logger                       : ConnectException occurred while connecting to 192.168.99.100:5432java.net.ConnectException: Connection refusedat java.net.PlainSocketImpl.socketConnect(Native Method) ~[na:1.8.0_71]at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350) ~[na:1.8.0_71]at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206) ~[na:1.8.0_71]at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188) ~[na:1.8.0_71]at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392) ~[na:1.8.0_71]at java.net.Socket.connect(Socket.java:589) ~[na:1.8.0_71]at org.postgresql.core.PGStream.<init>(PGStream.java:69) ~[postgresql-42.2.1.jar:42.2.1]at org.postgresql.core.v3.ConnectionFactoryImpl.openConnectionImpl(ConnectionFactoryImpl.java:158) ~[postgresql-42.2.1.jar:42.2.1]at org.postgresql.core.ConnectionFactory.openConnection(ConnectionFactory.java:49) [postgresql-42.2.1.jar:42.2.1]at org.postgresql.jdbc.PgConnection.<init>(PgConnection.java:195) [postgresql-42.2.1.jar:42.2.1]at org.postgresql.Driver.makeConnection(Driver.java:452) [postgresql-42.2.1.jar:42.2.1]at org.postgresql.Driver.connect(Driver.java:254) [postgresql-42.2.1.jar:42.2.1]at com.zaxxer.hikari.util.DriverDataSource.getConnection(DriverDataSource.java:117) [HikariCP-2.7.6.jar:na]at com.zaxxer.hikari.util.DriverDataSource.getConnection(DriverDataSource.java:123) [HikariCP-2.7.6.jar:na]at com.zaxxer.hikari.pool.PoolBase.newConnection(PoolBase.java:375) [HikariCP-2.7.6.jar:na]at com.zaxxer.hikari.pool.PoolBase.newPoolEntry(PoolBase.java:204) [HikariCP-2.7.6.jar:na]at com.zaxxer.hikari.pool.HikariPool.createPoolEntry(HikariPool.java:459) [HikariCP-2.7.6.jar:na]at com.zaxxer.hikari.pool.HikariPool.access$200(HikariPool.java:70) [HikariCP-2.7.6.jar:na]at com.zaxxer.hikari.pool.HikariPool$PoolEntryCreator.call(HikariPool.java:696) [HikariCP-2.7.6.jar:na]at com.zaxxer.hikari.pool.HikariPool$PoolEntryCreator.call(HikariPool.java:682) [HikariCP-2.7.6.jar:na]at java.util.concurrent.FutureTask.run(FutureTask.java:266) [na:1.8.0_71]at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) [na:1.8.0_71]at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) [na:1.8.0_71]at java.lang.Thread.run(Thread.java:745) [na:1.8.0_71]
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获取连接的源码

HikariCP-2.7.6-sources.jar!/com/zaxxer/hikari/pool/HikariPool.java

   /*** Get a connection from the pool, or timeout after the specified number of milliseconds.** @param hardTimeout the maximum time to wait for a connection from the pool* @return a java.sql.Connection instance* @throws SQLException thrown if a timeout occurs trying to obtain a connection*/public Connection getConnection(final long hardTimeout) throws SQLException{suspendResumeLock.acquire();final long startTime = currentTime();try {long timeout = hardTimeout;do {PoolEntry poolEntry = connectionBag.borrow(timeout, MILLISECONDS);if (poolEntry == null) {break; // We timed out... break and throw exception}final long now = currentTime();if (poolEntry.isMarkedEvicted() || (elapsedMillis(poolEntry.lastAccessed, now) > ALIVE_BYPASS_WINDOW_MS && !isConnectionAlive(poolEntry.connection))) {closeConnection(poolEntry, poolEntry.isMarkedEvicted() ? EVICTED_CONNECTION_MESSAGE : DEAD_CONNECTION_MESSAGE);timeout = hardTimeout - elapsedMillis(startTime);}else {metricsTracker.recordBorrowStats(poolEntry, startTime);return poolEntry.createProxyConnection(leakTaskFactory.schedule(poolEntry), now);}} while (timeout > 0L);metricsTracker.recordBorrowTimeoutStats(startTime);throw createTimeoutException(startTime);}catch (InterruptedException e) {Thread.currentThread().interrupt();throw new SQLException(poolName + " - Interrupted during connection acquisition", e);}finally {suspendResumeLock.release();}}
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tomcat

2018-01-30 15:39:23.913  INFO 5894 --- [           main] com.example.JpaDemoApplicationTests      : execute:1
2018-01-30 15:39:33.939  INFO 5894 --- [           main] com.example.JpaDemoApplicationTests      : execute:2
2018-01-30 15:39:43.949  INFO 5894 --- [           main] com.example.JpaDemoApplicationTests      : execute:3
2018-01-30 15:39:53.955  INFO 5894 --- [           main] com.example.JpaDemoApplicationTests      : execute:4
2018-01-30 15:40:03.962  INFO 5894 --- [           main] com.example.JpaDemoApplicationTests      : execute:5
2018-01-30 15:40:13.968  INFO 5894 --- [           main] com.example.JpaDemoApplicationTests      : execute:6
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tomcat jdbc pool有testOnBorrow,testOnReturn,testOnConnect,testWhileIdle属性来配置什么时候检测连接，如果是testOnBorrow的话，有空闲连接则进行borrow同时进行validate，如果上一次validate的时间在validation interval内，则默认validate成功，否则进行validate，validate失败会进行reconnect，再validate，如果再失败则抛出new SQLException("Failed to validate a newly established connection.")。如果没有空闲连接，且连接池没满就创建一个新的；如果没有空闲连接且连接池满了，则while轮询空闲队列，如果没取到连接，若没超过maxWait则继续，超过则抛出PoolExhaustedException。如果没有空闲连接，且连接池满了，则borrow超时时间为maxWait默认30秒。

这个示例程序，每次循环都会先归还连接再sleep，因此连接池始终有空闲连接，只是testOnBorrow校验不成功，进行了reconnect，在reconnect抛出了异常

reconnect抛出的异常

org.postgresql.util.PSQLException: Connection to 192.168.99.100:5432 refused. Check that the hostname and port are correct and that the postmaster is accepting TCP/IP connections.at org.postgresql.core.v3.ConnectionFactoryImpl.openConnectionImpl(ConnectionFactoryImpl.java:262)at org.postgresql.core.ConnectionFactory.openConnection(ConnectionFactory.java:51)at org.postgresql.jdbc.PgConnection.<init>(PgConnection.java:215)at org.postgresql.Driver.makeConnection(Driver.java:404)at org.postgresql.Driver.connect(Driver.java:272)at org.apache.tomcat.jdbc.pool.PooledConnection.connectUsingDriver(PooledConnection.java:310)at org.apache.tomcat.jdbc.pool.PooledConnection.connect(PooledConnection.java:203)at org.apache.tomcat.jdbc.pool.PooledConnection.reconnect(PooledConnection.java:361)at org.apache.tomcat.jdbc.pool.ConnectionPool.borrowConnection(ConnectionPool.java:821)at org.apache.tomcat.jdbc.pool.ConnectionPool.borrowConnection(ConnectionPool.java:651)at org.apache.tomcat.jdbc.pool.ConnectionPool.getConnection(ConnectionPool.java:198)at org.apache.tomcat.jdbc.pool.DataSourceProxy.getConnection(DataSourceProxy.java:132)at com.example.JpaDemoApplicationTests.testDatabaseDownAndUp(JpaDemoApplicationTests.java:296)at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)at java.lang.reflect.Method.invoke(Method.java:497)at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)at org.springframework.test.context.junit4.statements.RunBeforeTestMethodCallbacks.evaluate(RunBeforeTestMethodCallbacks.java:75)at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate(RunAfterTestMethodCallbacks.java:86)at org.springframework.test.context.junit4.statements.SpringRepeat.evaluate(SpringRepeat.java:84)at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:252)at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:94)at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:70)at org.junit.runners.ParentRunner.run(ParentRunner.java:363)at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:191)at org.junit.runner.JUnitCore.run(JUnitCore.java:137)at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:69)at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:234)at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:74)at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)at java.lang.reflect.Method.invoke(Method.java:497)at com.intellij.rt.execution.application.AppMain.main(AppMain.java:144)
Caused by: java.net.ConnectException: Connection refusedat java.net.PlainSocketImpl.socketConnect(Native Method)at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350)at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206)at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188)at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)at java.net.Socket.connect(Socket.java:589)at org.postgresql.core.PGStream.<init>(PGStream.java:61)at org.postgresql.core.v3.ConnectionFactoryImpl.openConnectionImpl(ConnectionFactoryImpl.java:144)... 44 more
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获取连接的源码

tomcat-jdbc-8.5.23-sources.jar!/org/apache/tomcat/jdbc/pool/ConnectionPool.java

    /*** Thread safe way to retrieve a connection from the pool* @param wait - time to wait, overrides the maxWait from the properties,* set to -1 if you wish to use maxWait, 0 if you wish no wait time.* @param username The user name to use for the connection* @param password The password for the connection* @return a connection* @throws SQLException Failed to get a connection*/private PooledConnection borrowConnection(int wait, String username, String password) throws SQLException {if (isClosed()) {throw new SQLException("Connection pool closed.");} //end if//get the current time stamplong now = System.currentTimeMillis();//see if there is one available immediatelyPooledConnection con = idle.poll();while (true) {if (con!=null) {//configure the connection and return itPooledConnection result = borrowConnection(now, con, username, password);borrowedCount.incrementAndGet();if (result!=null) return result;}//if we get here, see if we need to create one//this is not 100% accurate since it doesn't use a shared//atomic variable - a connection can become idle while we are creating//a new connectionif (size.get() < getPoolProperties().getMaxActive()) {//atomic duplicate checkif (size.addAndGet(1) > getPoolProperties().getMaxActive()) {//if we got here, two threads passed through the first ifsize.decrementAndGet();} else {//create a connection, we're below the limitreturn createConnection(now, con, username, password);}} //end if//calculate wait time for this iterationlong maxWait = wait;//if the passed in wait time is -1, means we should use the pool property valueif (wait==-1) {maxWait = (getPoolProperties().getMaxWait()<=0)?Long.MAX_VALUE:getPoolProperties().getMaxWait();}long timetowait = Math.max(0, maxWait - (System.currentTimeMillis() - now));waitcount.incrementAndGet();try {//retrieve an existing connectioncon = idle.poll(timetowait, TimeUnit.MILLISECONDS);} catch (InterruptedException ex) {if (getPoolProperties().getPropagateInterruptState()) {Thread.currentThread().interrupt();}SQLException sx = new SQLException("Pool wait interrupted.");sx.initCause(ex);throw sx;} finally {waitcount.decrementAndGet();}if (maxWait==0 && con == null) { //no wait, return one if we have oneif (jmxPool!=null) {jmxPool.notify(org.apache.tomcat.jdbc.pool.jmx.ConnectionPool.POOL_EMPTY, "Pool empty - no wait.");}throw new PoolExhaustedException("[" + Thread.currentThread().getName()+"] " +"NoWait: Pool empty. Unable to fetch a connection, none available["+busy.size()+" in use].");}//we didn't get a connection, lets see if we timed outif (con == null) {if ((System.currentTimeMillis() - now) >= maxWait) {if (jmxPool!=null) {jmxPool.notify(org.apache.tomcat.jdbc.pool.jmx.ConnectionPool.POOL_EMPTY, "Pool empty - timeout.");}throw new PoolExhaustedException("[" + Thread.currentThread().getName()+"] " +"Timeout: Pool empty. Unable to fetch a connection in " + (maxWait / 1000) +" seconds, none available[size:"+size.get() +"; busy:"+busy.size()+"; idle:"+idle.size()+"; lastwait:"+timetowait+"].");} else {//no timeout, lets try againcontinue;}}} //while}
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小结

如果是没有空闲连接且连接池满不能新建连接的情况下

• hikari则是阻塞connectionTimeout的时间，没有得到连接抛出SQLTransientConnectionException
• tomcat jdbc pool会阻塞max-wait时间，若没有得到连接则抛出PoolExhaustedException

如果是有空闲连接的情况

• hikari是在connectionTimeout时间内不断循环获取下一个空闲连接进行校验，校验失败继续获取下一个空闲连接，直到超时抛出SQLTransientConnectionException
• tomcat jdbc pool会borrow连接然后validate连接，正常validate失败会reconnect，再validate，若此时reconnect不成功则抛出ConnectException: Connection refused，如果reconnect成功但是validate失败，则抛出SQLException("Failed to validate a newly established connection.")

假设数据库是挂的，但还有空闲连接，tomcat的testOnBorrow=true。对比可以发现

hikari在获取一个连接的时候，会在connectionTimeout时间内循环把空闲连接挨个validate一次，最后timeout抛出异常；之后的获取连接操作，则一直阻塞connectionTimeout时间再抛出异常

tomcat jdbc pool则是在获取一个连接的时候，先borrow出来连接，正常validate失败会reconnect，再validate，通常reconnect的时候抛出了ConnectException: Connection refused，然后业务程序会fail fast，之后的获取连接也都是fail fast的

由此可见，hikari如果connectionTimeout如果设置太大的话，在数据库挂的时候，很容易阻塞业务线程，而tomcat jdbc pool则会fail fast。

另外hikari是异步去建立minIdle大小的连接，而tomcat是同步的建立initial-size的连接。