数据库连接数太多导致无法连接问题

  • 问题复现
  • 解决方法

问题复现

项目数据库使用的是 postgresql 11 ，启动时数据库连接报错，错误信息如下：

org.postgresql.util.PSQLException: 致命错误: 对不起, 已经有太多的客户 (pgjdbc: autodetected server-encoding to be GB2312, if the message is not readable, please check database logs and/or host, port, dbname, user, password, pg_hba.conf)at org.postgresql.core.v3.ConnectionFactoryImpl.doAuthentication(ConnectionFactoryImpl.java:525) ~[postgresql-42.2.14.jar:42.2.14]at org.postgresql.core.v3.ConnectionFactoryImpl.tryConnect(ConnectionFactoryImpl.java:146) ~[postgresql-42.2.14.jar:42.2.14]at org.postgresql.core.v3.ConnectionFactoryImpl.openConnectionImpl(ConnectionFactoryImpl.java:197) ~[postgresql-42.2.14.jar:42.2.14]at org.postgresql.core.ConnectionFactory.openConnection(ConnectionFactory.java:49) ~[postgresql-42.2.14.jar:42.2.14]at org.postgresql.jdbc.PgConnection.<init>(PgConnection.java:217) ~[postgresql-42.2.14.jar:42.2.14]at org.postgresql.Driver.makeConnection(Driver.java:458) ~[postgresql-42.2.14.jar:42.2.14]at org.postgresql.Driver.connect(Driver.java:260) ~[postgresql-42.2.14.jar:42.2.14]at com.alibaba.druid.filter.FilterChainImpl.connection_connect(FilterChainImpl.java:156) ~[druid-1.1.12.jar:1.1.12]at com.alibaba.druid.filter.FilterAdapter.connection_connect(FilterAdapter.java:786) ~[druid-1.1.12.jar:1.1.12]at com.alibaba.druid.filter.FilterChainImpl.connection_connect(FilterChainImpl.java:150) ~[druid-1.1.12.jar:1.1.12]at com.alibaba.druid.filter.stat.StatFilter.connection_connect(StatFilter.java:218) ~[druid-1.1.12.jar:1.1.12]at com.alibaba.druid.filter.FilterChainImpl.connection_connect(FilterChainImpl.java:150) ~[druid-1.1.12.jar:1.1.12]at com.alibaba.druid.pool.DruidAbstractDataSource.createPhysicalConnection(DruidAbstractDataSource.java:1572) ~[druid-1.1.12.jar:1.1.12]at com.alibaba.druid.pool.DruidAbstractDataSource.createPhysicalConnection(DruidAbstractDataSource.java:1636) ~[druid-1.1.12.jar:1.1.12]at com.alibaba.druid.pool.DruidDataSource.init(DruidDataSource.java:874) [druid-1.1.12.jar:1.1.12]at com.alibaba.druid.pool.DruidDataSource.getConnection(DruidDataSource.java:1246) [druid-1.1.12.jar:1.1.12]at com.alibaba.druid.pool.DruidDataSource.getConnection(DruidDataSource.java:1242) [druid-1.1.12.jar:1.1.12]at com.alibaba.druid.pool.DruidDataSource.getConnection(DruidDataSource.java:89) [druid-1.1.12.jar:1.1.12]at org.springframework.jdbc.datasource.DataSourceUtils.fetchConnection(DataSourceUtils.java:158) [spring-jdbc-5.2.7.RELEASE.jar:5.2.7.RELEASE]at org.springframework.jdbc.datasource.DataSourceUtils.doGetConnection(DataSourceUtils.java:116) [spring-jdbc-5.2.7.RELEASE.jar:5.2.7.RELEASE]at org.springframework.jdbc.datasource.DataSourceUtils.getConnection(DataSourceUtils.java:79) [spring-jdbc-5.2.7.RELEASE.jar:5.2.7.RELEASE]at org.mybatis.spring.transaction.SpringManagedTransaction.openConnection(SpringManagedTransaction.java:82) [mybatis-spring-2.0.1.jar:2.0.1]at org.mybatis.spring.transaction.SpringManagedTransaction.getConnection(SpringManagedTransaction.java:68) [mybatis-spring-2.0.1.jar:2.0.1]at org.apache.ibatis.executor.BaseExecutor.getConnection(BaseExecutor.java:336) [mybatis-3.5.1.jar:3.5.1]at org.apache.ibatis.executor.SimpleExecutor.prepareStatement(SimpleExecutor.java:85) [mybatis-3.5.1.jar:3.5.1]at org.apache.ibatis.executor.SimpleExecutor.doQuery(SimpleExecutor.java:62) [mybatis-3.5.1.jar:3.5.1]at org.apache.ibatis.executor.BaseExecutor.queryFromDatabase(BaseExecutor.java:324) [mybatis-3.5.1.jar:3.5.1]at org.apache.ibatis.executor.BaseExecutor.query(BaseExecutor.java:156) [mybatis-3.5.1.jar:3.5.1]at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:109) [mybatis-3.5.1.jar:3.5.1]at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:83) [mybatis-3.5.1.jar:3.5.1]at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:147) [mybatis-3.5.1.jar:3.5.1]at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:140) [mybatis-3.5.1.jar:3.5.1]at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_231]at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_231]at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_231]at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_231]at org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:433) [mybatis-spring-2.0.1.jar:2.0.1]at com.sun.proxy.$Proxy74.selectList(Unknown Source) [na:na]at org.mybatis.spring.SqlSessionTemplate.selectList(SqlSessionTemplate.java:230) [mybatis-spring-2.0.1.jar:2.0.1]at org.apache.ibatis.binding.MapperMethod.executeForMany(MapperMethod.java:147) [mybatis-3.5.1.jar:3.5.1]at org.apache.ibatis.binding.MapperMethod.execute(MapperMethod.java:80) [mybatis-3.5.1.jar:3.5.1]at org.apache.ibatis.binding.MapperProxy.invoke(MapperProxy.java:58) [mybatis-3.5.1.jar:3.5.1]at com.sun.proxy.$Proxy76.getAll(Unknown Source) [na:na]at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_231]at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_231]at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_231]at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_231]at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:344) [spring-aop-5.2.7.RELEASE.jar:5.2.7.RELEASE]at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:198) [spring-aop-5.2.7.RELEASE.jar:5.2.7.RELEASE]at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:163) [spring-aop-5.2.7.RELEASE.jar:5.2.7.RELEASE]at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:139) [spring-tx-5.2.7.RELEASE.jar:5.2.7.RELEASE]at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) [spring-aop-5.2.7.RELEASE.jar:5.2.7.RELEASE]at com.alibaba.druid.support.spring.stat.DruidStatInterceptor.invoke(DruidStatInterceptor.java:72) [druid-1.1.12.jar:1.1.12]at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186) [spring-aop-5.2.7.RELEASE.jar:5.2.7.RELEASE]at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:212) [spring-aop-5.2.7.RELEASE.jar:5.2.7.RELEASE]at com.sun.proxy.$Proxy77.getAll(Unknown Source) [na:na]at com.creatar.dataservice.service.impl.PmtCmdOperateRecordServiceImpl.getAll(PmtCmdOperateRecordServiceImpl.java:144) [classes/:na]at com.creatar.dataservice.common.ServerApplication.run(ServerApplication.java:119) [classes/:na]at org.springframework.boot.SpringApplication.callRunner(SpringApplication.java:786) [spring-boot-2.3.1.RELEASE.jar:2.3.1.RELEASE]at org.springframework.boot.SpringApplication.callRunners(SpringApplication.java:776) [spring-boot-2.3.1.RELEASE.jar:2.3.1.RELEASE]at org.springframework.boot.SpringApplication.run(SpringApplication.java:322) [spring-boot-2.3.1.RELEASE.jar:2.3.1.RELEASE]at org.springframework.boot.test.context.SpringBootContextLoader.loadContext(SpringBootContextLoader.java:120) [spring-boot-test-2.3.1.RELEASE.jar:2.3.1.RELEASE]at org.springframework.test.context.cache.DefaultCacheAwareContextLoaderDelegate.loadContextInternal(DefaultCacheAwareContextLoaderDelegate.java:99) [spring-test-5.2.7.RELEASE.jar:5.2.7.RELEASE]at org.springframework.test.context.cache.DefaultCacheAwareContextLoaderDelegate.loadContext(DefaultCacheAwareContextLoaderDelegate.java:124) [spring-test-5.2.7.RELEASE.jar:5.2.7.RELEASE]at org.springframework.test.context.support.DefaultTestContext.getApplicationContext(DefaultTestContext.java:123) [spring-test-5.2.7.RELEASE.jar:5.2.7.RELEASE]at org.springframework.test.context.web.ServletTestExecutionListener.setUpRequestContextIfNecessary(ServletTestExecutionListener.java:190) [spring-test-5.2.7.RELEASE.jar:5.2.7.RELEASE]at org.springframework.test.context.web.ServletTestExecutionListener.prepareTestInstance(ServletTestExecutionListener.java:132) [spring-test-5.2.7.RELEASE.jar:5.2.7.RELEASE]at org.springframework.test.context.TestContextManager.prepareTestInstance(TestContextManager.java:244) [spring-test-5.2.7.RELEASE.jar:5.2.7.RELEASE]at org.springframework.test.context.junit.jupiter.SpringExtension.postProcessTestInstance(SpringExtension.java:98) [spring-test-5.2.7.RELEASE.jar:5.2.7.RELEASE]at org.junit.jupiter.engine.descriptor.ClassBasedTestDescriptor.lambda$invokeTestInstancePostProcessors$5(ClassBasedTestDescriptor.java:341) [junit-jupiter-engine-5.6.2.jar:5.6.2]at org.junit.jupiter.engine.descriptor.ClassBasedTestDescriptor.executeAndMaskThrowable(ClassBasedTestDescriptor.java:346) [junit-jupiter-engine-5.6.2.jar:5.6.2]at org.junit.jupiter.engine.descriptor.ClassBasedTestDescriptor.lambda$invokeTestInstancePostProcessors$6(ClassBasedTestDescriptor.java:341) [junit-jupiter-engine-5.6.2.jar:5.6.2]at java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:193) ~[na:1.8.0_231]at java.util.stream.ReferencePipeline$2$1.accept(ReferencePipeline.java:175) ~[na:1.8.0_231]at java.util.ArrayList$ArrayListSpliterator.forEachRemaining(ArrayList.java:1382) ~[na:1.8.0_231]at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:482) ~[na:1.8.0_231]at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:472) ~[na:1.8.0_231]at java.util.stream.StreamSpliterators$WrappingSpliterator.forEachRemaining(StreamSpliterators.java:312) ~[na:1.8.0_231]at java.util.stream.Streams$ConcatSpliterator.forEachRemaining(Streams.java:743) ~[na:1.8.0_231]at java.util.stream.Streams$ConcatSpliterator.forEachRemaining(Streams.java:742) ~[na:1.8.0_231]at java.util.stream.ReferencePipeline$Head.forEach(ReferencePipeline.java:580) ~[na:1.8.0_231]at org.junit.jupiter.engine.descriptor.ClassBasedTestDescriptor.invokeTestInstancePostProcessors(ClassBasedTestDescriptor.java:340) [junit-jupiter-engine-5.6.2.jar:5.6.2]at org.junit.jupiter.engine.descriptor.ClassBasedTestDescriptor.instantiateAndPostProcessTestInstance(ClassBasedTestDescriptor.java:263) [junit-jupiter-engine-5.6.2.jar:5.6.2]at org.junit.jupiter.engine.descriptor.ClassBasedTestDescriptor.lambda$testInstancesProvider$2(ClassBasedTestDescriptor.java:256) [junit-jupiter-engine-5.6.2.jar:5.6.2]at java.util.Optional.orElseGet(Optional.java:267) ~[na:1.8.0_231]at org.junit.jupiter.engine.descriptor.ClassBasedTestDescriptor.lambda$testInstancesProvider$3(ClassBasedTestDescriptor.java:255) [junit-jupiter-engine-5.6.2.jar:5.6.2]at org.junit.jupiter.engine.execution.TestInstancesProvider.getTestInstances(TestInstancesProvider.java:29) ~[junit-jupiter-engine-5.6.2.jar:5.6.2]at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.lambda$prepare$0(TestMethodTestDescriptor.java:108) ~[junit-jupiter-engine-5.6.2.jar:5.6.2]at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73) ~[junit-platform-engine-1.6.2.jar:1.6.2]at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.prepare(TestMethodTestDescriptor.java:107) ~[junit-jupiter-engine-5.6.2.jar:5.6.2]at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.prepare(TestMethodTestDescriptor.java:71) ~[junit-jupiter-engine-5.6.2.jar:5.6.2]at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$prepare$1(NodeTestTask.java:107) ~[junit-platform-engine-1.6.2.jar:1.6.2]at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73) ~[junit-platform-engine-1.6.2.jar:1.6.2]at org.junit.platform.engine.support.hierarchical.NodeTestTask.prepare(NodeTestTask.java:107) ~[junit-platform-engine-1.6.2.jar:1.6.2]at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:75) ~[junit-platform-engine-1.6.2.jar:1.6.2]at java.util.ArrayList.forEach(ArrayList.java:1257) ~[na:1.8.0_231]at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:38) ~[junit-platform-engine-1.6.2.jar:1.6.2]at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:139) ~[junit-platform-engine-1.6.2.jar:1.6.2]at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73) ~[junit-platform-engine-1.6.2.jar:1.6.2]at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:125) ~[junit-platform-engine-1.6.2.jar:1.6.2]at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:135) ~[junit-platform-engine-1.6.2.jar:1.6.2]at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:123) ~[junit-platform-engine-1.6.2.jar:1.6.2]at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73) ~[junit-platform-engine-1.6.2.jar:1.6.2]at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:122) ~[junit-platform-engine-1.6.2.jar:1.6.2]at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:80) ~[junit-platform-engine-1.6.2.jar:1.6.2]at java.util.ArrayList.forEach(ArrayList.java:1257) ~[na:1.8.0_231]at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:38) ~[junit-platform-engine-1.6.2.jar:1.6.2]at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:139) ~[junit-platform-engine-1.6.2.jar:1.6.2]at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73) ~[junit-platform-engine-1.6.2.jar:1.6.2]at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:125) ~[junit-platform-engine-1.6.2.jar:1.6.2]at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:135) ~[junit-platform-engine-1.6.2.jar:1.6.2]at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:123) ~[junit-platform-engine-1.6.2.jar:1.6.2]at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73) ~[junit-platform-engine-1.6.2.jar:1.6.2]at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:122) ~[junit-platform-engine-1.6.2.jar:1.6.2]at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:80) ~[junit-platform-engine-1.6.2.jar:1.6.2]at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.submit(SameThreadHierarchicalTestExecutorService.java:32) ~[junit-platform-engine-1.6.2.jar:1.6.2]at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor.execute(HierarchicalTestExecutor.java:57) ~[junit-platform-engine-1.6.2.jar:1.6.2]at org.junit.platform.engine.support.hierarchical.HierarchicalTestEngine.execute(HierarchicalTestEngine.java:51) ~[junit-platform-engine-1.6.2.jar:1.6.2]at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:248) ~[junit-platform-launcher-1.6.2.jar:1.6.2]at org.junit.platform.launcher.core.DefaultLauncher.lambda$execute$5(DefaultLauncher.java:211) ~[junit-platform-launcher-1.6.2.jar:1.6.2]at org.junit.platform.launcher.core.DefaultLauncher.withInterceptedStreams(DefaultLauncher.java:226) ~[junit-platform-launcher-1.6.2.jar:1.6.2]at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:199) ~[junit-platform-launcher-1.6.2.jar:1.6.2]at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:132) ~[junit-platform-launcher-1.6.2.jar:1.6.2]at com.intellij.junit5.JUnit5IdeaTestRunner.startRunnerWithArgs(JUnit5IdeaTestRunner.java:69) ~[junit5-rt.jar:na]at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:33) ~[junit-rt.jar:na]at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:230) ~[junit-rt.jar:na]at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:58) ~[junit-rt.jar:na]2021-01-15 15:22:26.458 ERROR 22164 --- [           main] com.alibaba.druid.pool.DruidDataSource   : {dataSource-1} init error

解决方法

首先我们可以先通过查询查看一下当前的连接情况，查询sql如下：

select  * from pg_stat_activity;

结果集会显示出当前连接的数据库名，用户，IP地址，连接开始时间，查询的语句，状态等。
这时我们可以根据 state 列进行区分：
1、如果大部分的连接state列的值为active，则需要考虑增加数据库的最大连接数，修改方法为：
找到postgresql安装配置文件 postgresql.conf ，直接修改配置值
max_connections = 2500 # (change requires restart)
其中2500为修改的具体值，根据自己的需要指定，修改后需要重启数据库服务。
2、如果大部分的连连接state值为idle，并且我们不（懒）想（的）重启的话，可以用pg_stat_get_backend_activity(integer) 函数kill掉处于空闲状态的连接，完整sql如下：

SELECT pg_terminate_backend(pid) FROM pg_stat_activity WHERE state='idle'

OK，这下就杀掉了全部空闲的连接了，

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