Apparent connection leak detected

异常信息:

java.lang.Exception: Apparent connection leak detected
at com.sq.driver.datasource.HikariDatasourceWrap.initDatasource(HikariDatasourceWrap.java:73)
at com.sq.config.cache.BaseNodeResource$Builder.lambda$withFactory$2(BaseNodeResource.java:280)
at com.sq.config.cache.BaseNodeResource.get(BaseNodeResource.java:129)
at com.sq.driver.datasource.HikariDatasourceWrap.warmup(HikariDatasourceWrap.java:171)
at com.sq.pool.core.spring.WarmupProcess.onApplicationEvent(WarmupProcess.java:34)
at com.sq.pool.core.spring.WarmupProcess.onApplicationEvent(WarmupProcess.java:20)
at org.springframework.context.event.SimpleApplicationEventMulticaster.invokeListener(SimpleApplicationEventMulticaster.java:163)
at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:136)
at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:381)
at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:335)
at org.springframework.context.support.AbstractApplicationContext.finishRefresh(AbstractApplicationContext.java:855)
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:541)
at org.springframework.web.context.ContextLoader.configureAndRefreshWebApplicationContext(ContextLoader.java:446)
at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:328)
at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:107)
at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4853)
at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5314)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:145)

数据源配置:

<?xml version="1.0" encoding="utf-8"?>

<config>
<value>{"name":"pool","driverClassName":"com.mysql.jdbc.Driver", "jdbcUrl":"jdbc:mysql://************************************:8888/dispatcher?zeroDateTimeBehavior=convertToNull&useUnicode=true&characterEncoding=UTF-8&connectTimeout=1000&socketTimeout=15000", "username":"*******", "password": "*************", "maximumPoolSize":20, "minimumIdle":20, "connectionTimeout":3000, "leakDetectionThreshold":10000}</value>
</config>

原理介绍:

leakDetectionThreshold 设定了连接泄露阀值10s，即当从连接池里取出连接超过10s不归还时，会warn Apparent connection leak detected

HikariPool#getConnection

ProxyLeakTask#ProxyLeakTask

在连接归还或被踢除时，会清除此调度任务，详见ProxyConnection。即在10s内归还连接，会清除调度任务。超过10s调度任务执行。

清除调度任务时，如果已经超过调度时间，会LOGGER.info("Previously reported leaked connection {} was returned to the pool (unleaked)", connectionName);。详见ProxyLeakTask#cancel。

解决方案:

只借不还，浪费资源。有借须有还，将connection归还。

HikariDatasourceWrap#initDatasource

总结：

这个case中最大的亮点是。Hikari warn日志中详细的打印出，存在连接泄露的代码行数，异常信息非常直白易懂。实现逻辑详见 ProxyLeakTask#ProxyLeakTask ProxyLeakTask#run。优秀的代码设计+不错的性能，也难怪SpringBoot2.0起默认数据库连接池从TomcatPool换到了「HikariCP」。