背景
晚上发现数据库的连接有1000多个，通过 show processlist 命令经排查发现都是我部署的一个项目的两台服务器连接的
奇怪的是，我使用的Java框架是springboot，默认是用连接池的，我没有配置，默认应该最大连接应该是10个，为什么会有这么多的连接呢
排查
使用如下命令kill
select * from information_schema.processlist where user=‘follow_up’
select concat(‘KILL ‘,id,’;’) from information_schema.processlist where user=‘follow_up’
kill掉之后，发现连接还是会继续增长
我在项目中把用户名故意写错，密码也清空了，重启部署，连接还是在，还是1000多
无奈，我把tomcat中的webapp项目中的我的项目给删除了，连接还是在
无奈，删除了项目之后，重启了tomcat
第二天尝试
现在一个连接都没有，所以我重新部署一了一遍，发现有20个连接（两台服务器，每个默认最大10个连接）
再部署一遍，发现有40个连接
部署第三次，发现有60个连接
再把项目从webapp目录删除，连接还在
再部署几遍，连接数达到了80，100，最后达到了200个
请教了其他的同时，未果。
请教了大牛，未果。
最后花钱请教了一个老师，说你查看一下catalina日志。
惊喜的发现了一个单词undeploy
下面是重要的日志
grep undeploy -A4 catalina.2022-09-08.log
08-Sep-2022 09:31:16.791 INFO [Catalina-utility-2] org.apache.catalina.startup.HostConfig.undeploy Undeploying context [/followuph5]
08-Sep-2022 09:31:16.808 WARNING [Catalina-utility-2] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesJdbc The web application [followuph5] registered the JDBC driver [com.mysql.cj.jdbc.Driver] but failed to unregister it when the web application was stopped. To prevent a memory leak, the JDBC Driver has been forcibly unregistered.
08-Sep-2022 09:31:16.823 WARNING [Catalina-utility-2] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesThreads The web application [followuph5] appears to have started a thread named [mysql-cj-abandoned-connection-cleanup] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:
java.lang.Object.wait(Native Method)
java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:143)
--
08-Sep-2022 09:44:25.745 INFO [Catalina-utility-2] org.apache.catalina.startup.HostConfig.undeploy Undeploying context [/followuph5]
08-Sep-2022 09:44:25.783 WARNING [Catalina-utility-2] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesJdbc The web application [followuph5] registered the JDBC driver [com.mysql.cj.jdbc.Driver] but failed to unregister it when the web application was stopped. To prevent a memory leak, the JDBC Driver has been forcibly unregistered.
08-Sep-2022 09:44:25.798 WARNING [Catalina-utility-2] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesThreads The web application [followuph5] appears to have started a thread named [mysql-cj-abandoned-connection-cleanup] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:
java.lang.Object.wait(Native Method)
java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:143)
--
08-Sep-2022 10:46:10.577 INFO [Catalina-utility-2] org.apache.catalina.startup.HostConfig.undeploy Undeploying context [/followuph5]
08-Sep-2022 10:46:10.600 WARNING [Catalina-utility-2] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesJdbc The web application [followuph5] registered the JDBC driver [com.mysql.cj.jdbc.Driver] but failed to unregister it when the web application was stopped. To prevent a memory leak, the JDBC Driver has been forcibly unregistered.
08-Sep-2022 10:46:10.615 WARNING [Catalina-utility-2] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesThreads The web application [followuph5] appears to have started a thread named [mysql-cj-abandoned-connection-cleanup] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:
java.lang.Object.wait(Native Method)
java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:143)
--
08-Sep-2022 10:49:44.786 INFO [Catalina-utility-2] org.apache.catalina.startup.HostConfig.undeploy Undeploying context [/followuph5]
08-Sep-2022 10:49:44.816 INFO [Catalina-utility-2] org.apache.catalina.startup.HostConfig.deployWAR Deploying web application archive [/usr/local/tomcat/webapps/followuph5.war]
08-Sep-2022 10:49:51.611 INFO [Catalina-utility-2] org.apache.jasper.servlet.TldScanner.scanJars At least one JAR was scanned for TLDs yet contained no TLDs. Enable debug logging for thislogger for a complete list of JARs that were scanned but no TLDs were found in them. Skipping unneeded JARs during scanning can improve startup time and JSP compilation time.
08-Sep-2022 10:49:51.615 INFO [Catalina-utility-2] org.apache.catalina.startup.HostConfig.deployWAR Deployment of web application archive [/usr/local/tomcat/webapps/followuph5.war] has finished in [6,799] ms
08-Sep-2022 10:50:00.730 INFO [catalina-exec-41427] org.apache.coyote.http11.Http11Processor.service Error parsing HTTP request header
--
08-Sep-2022 11:15:15.026 INFO [Catalina-utility-1] org.apache.catalina.startup.HostConfig.undeploy Undeploying context [/followuph5]
08-Sep-2022 11:15:15.270 WARNING [Catalina-utility-1] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesJdbc The web application [followuph5] registered the JDBC driver [com.mysql.cj.jdbc.Driver] but failed to unregister it when the web application was stopped. To prevent a memory leak, the JDBC Driver has been forcibly unregistered.
08-Sep-2022 11:15:15.288 WARNING [Catalina-utility-1] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesThreads The web application [followuph5] appears to have started a thread named [mysql-cj-abandoned-connection-cleanup] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:
java.lang.Object.wait(Native Method)
java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:143)
--
08-Sep-2022 12:04:21.593 INFO [Catalina-utility-2] org.apache.catalina.startup.HostConfig.undeploy Undeploying context [/followuph5]
08-Sep-2022 12:04:21.787 WARNING [Catalina-utility-2] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesJdbc The web application [followuph5] registered the JDBC driver [com.mysql.cj.jdbc.Driver] but failed to unregister it when the web application was stopped. To prevent a memory leak, the JDBC Driver has been forcibly unregistered.
08-Sep-2022 12:04:21.802 WARNING [Catalina-utility-2] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesThreads The web application [followuph5] appears to have started a thread named [mysql-cj-abandoned-connection-cleanup] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:
java.lang.Object.wait(Native Method)
java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:143)
--
08-Sep-2022 13:32:22.692 INFO [Catalina-utility-2] org.apache.catalina.startup.HostConfig.undeploy Undeploying context [/followuph5]
08-Sep-2022 13:32:22.716 WARNING [Catalina-utility-2] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesJdbc The web application [followuph5] registered the JDBC driver [com.mysql.cj.jdbc.Driver] but failed to unregister it when the web application was stopped. To prevent a memory leak, the JDBC Driver has been forcibly unregistered.
08-Sep-2022 13:32:22.730 WARNING [Catalina-utility-2] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesThreads The web application [followuph5] appears to have started a thread named [mysql-cj-abandoned-connection-cleanup] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:
java.lang.Object.wait(Native Method)
java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:143)
--
08-Sep-2022 14:58:14.381 INFO [Catalina-utility-2] org.apache.catalina.startup.HostConfig.undeploy Undeploying context [/followuph5]
08-Sep-2022 14:58:14.419 WARNING [Catalina-utility-2] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesJdbc The web application [followuph5] registered the JDBC driver [com.mysql.cj.jdbc.Driver] but failed to unregister it when the web application was stopped. To prevent a memory leak, the JDBC Driver has been forcibly unregistered.
08-Sep-2022 14:58:14.435 WARNING [Catalina-utility-2] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesThreads The web application [followuph5] appears to have started a thread named [mysql-cj-abandoned-connection-cleanup] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:
java.lang.Object.wait(Native Method)
java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:143)
--
08-Sep-2022 15:08:44.587 INFO [Catalina-utility-1] org.apache.catalina.startup.HostConfig.undeploy Undeploying context [/followuph5]
08-Sep-2022 15:08:44.739 WARNING [Catalina-utility-1] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesJdbc The web application [followuph5] registered the JDBC driver [com.mysql.cj.jdbc.Driver] but failed to unregister it when the web application was stopped. To prevent a memory leak, the JDBC Driver has been forcibly unregistered.
08-Sep-2022 15:08:44.754 WARNING [Catalina-utility-1] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesThreads The web application [followuph5] appears to have started a thread named [mysql-cj-abandoned-connection-cleanup] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:
java.lang.Object.wait(Native Method)
java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:143)
--
08-Sep-2022 15:14:12.424 INFO [Catalina-utility-1] org.apache.catalina.startup.HostConfig.undeploy Undeploying context [/followuph5]
08-Sep-2022 15:14:12.427 WARNING [Catalina-utility-1] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesJdbc The web application [followuph5] registered the JDBC driver [com.mysql.cj.jdbc.Driver] but failed to unregister it when the web application was stopped. To prevent a memory leak, the JDBC Driver has been forcibly unregistered.
08-Sep-2022 15:14:12.444 WARNING [Catalina-utility-1] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesThreads The web application [followuph5] appears to have started a thread named [mysql-cj-abandoned-connection-cleanup] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:
java.lang.Object.wait(Native Method)
java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:143)
--
08-Sep-2022 15:42:15.197 INFO [Catalina-utility-1] org.apache.catalina.startup.HostConfig.undeploy Undeploying context [/followuph5]
08-Sep-2022 15:42:15.292 WARNING [Catalina-utility-1] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesJdbc The web application [followuph5] registered the JDBC driver [com.mysql.cj.jdbc.Driver] but failed to unregister it when the web application was stopped. To prevent a memory leak, the JDBC Driver has been forcibly unregistered.
08-Sep-2022 15:42:15.307 WARNING [Catalina-utility-1] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesThreads The web application [followuph5] appears to have started a thread named [mysql-cj-abandoned-connection-cleanup] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:
java.lang.Object.wait(Native Method)
java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:143)
--
08-Sep-2022 15:46:03.074 INFO [Catalina-utility-2] org.apache.catalina.startup.HostConfig.undeploy Undeploying context [/followuph5]
08-Sep-2022 15:46:03.356 WARNING [Catalina-utility-2] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesJdbc The web application [followuph5] registered the JDBC driver [com.mysql.cj.jdbc.Driver] but failed to unregister it when the web application was stopped. To prevent a memory leak, the JDBC Driver has been forcibly unregistered.
08-Sep-2022 15:46:03.371 WARNING [Catalina-utility-2] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesThreads The web application [followuph5] appears to have started a thread named [mysql-cj-abandoned-connection-cleanup] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:
java.lang.Object.wait(Native Method)
java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:143)
--
08-Sep-2022 15:47:51.011 INFO [Catalina-utility-2] org.apache.catalina.startup.HostConfig.undeploy Undeploying context [/followuph5]
08-Sep-2022 15:47:51.037 WARNING [Catalina-utility-2] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesJdbc The web application [followuph5] registered the JDBC driver [com.mysql.cj.jdbc.Driver] but failed to unregister it when the web application was stopped. To prevent a memory leak, the JDBC Driver has been forcibly unregistered.
08-Sep-2022 15:47:51.054 WARNING [Catalina-utility-2] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesThreads The web application [followuph5] appears to have started a thread named [mysql-cj-abandoned-connection-cleanup] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:
java.lang.Object.wait(Native Method)
java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:143)
--
08-Sep-2022 16:17:12.405 INFO [Catalina-utility-1] org.apache.catalina.startup.HostConfig.undeploy Undeploying context [/followuph5]
08-Sep-2022 16:17:12.668 WARNING [Catalina-utility-1] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesJdbc The web application [followuph5] registered the JDBC driver [com.mysql.cj.jdbc.Driver] but failed to unregister it when the web application was stopped. To prevent a memory leak, the JDBC Driver has been forcibly unregistered.
08-Sep-2022 16:17:12.681 WARNING [Catalina-utility-1] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesThreads The web application [followuph5] appears to have started a thread named [mysql-cj-abandoned-connection-cleanup] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:
java.lang.Object.wait(Native Method)
java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:143)
--
08-Sep-2022 16:24:51.011 INFO [Catalina-utility-2] org.apache.catalina.startup.HostConfig.undeploy Undeploying context [/followuph5]
08-Sep-2022 16:24:51.270 WARNING [Catalina-utility-2] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesJdbc The web application [followuph5] registered the JDBC driver [com.mysql.cj.jdbc.Driver] but failed to unregister it when the web application was stopped. To prevent a memory leak, the JDBC Driver has been forcibly unregistered.
08-Sep-2022 16:24:51.285 WARNING [Catalina-utility-2] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesThreads The web application [followuph5] appears to have started a thread named [mysql-cj-abandoned-connection-cleanup] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:
java.lang.Object.wait(Native Method)
java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:143)
--
08-Sep-2022 16:39:00.667 INFO [Catalina-utility-2] org.apache.catalina.startup.HostConfig.undeploy Undeploying context [/followuph5]
08-Sep-2022 16:39:00.691 WARNING [Catalina-utility-2] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesJdbc The web application [followuph5] registered the JDBC driver [com.mysql.cj.jdbc.Driver] but failed to unregister it when the web application was stopped. To prevent a memory leak, the JDBC Driver has been forcibly unregistered.
08-Sep-2022 16:39:00.706 WARNING [Catalina-utility-2] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesThreads The web application [followuph5] appears to have started a thread named [mysql-cj-abandoned-connection-cleanup] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:
java.lang.Object.wait(Native Method)
java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:143)
--
08-Sep-2022 17:21:08.789 INFO [Catalina-utility-1] org.apache.catalina.startup.HostConfig.undeploy Undeploying context [/followuph5]
08-Sep-2022 17:21:08.993 WARNING [Catalina-utility-1] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesJdbc The web application [followuph5] registered the JDBC driver [com.mysql.cj.jdbc.Driver] but failed to unregister it when the web application was stopped. To prevent a memory leak, the JDBC Driver has been forcibly unregistered.
08-Sep-2022 17:21:09.008 WARNING [Catalina-utility-1] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesThreads The web application [followuph5] appears to have started a thread named [mysql-cj-abandoned-connection-cleanup] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:
java.lang.Object.wait(Native Method)
java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:143)
--
08-Sep-2022 17:38:39.011 INFO [Catalina-utility-2] org.apache.catalina.startup.HostConfig.undeploy Undeploying context [/followuph5]
08-Sep-2022 17:38:39.304 WARNING [Catalina-utility-2] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesJdbc The web application [followuph5] registered the JDBC driver [com.mysql.cj.jdbc.Driver] but failed to unregister it when the web application was stopped. To prevent a memory leak, the JDBC Driver has been forcibly unregistered.
08-Sep-2022 17:38:39.318 WARNING [Catalina-utility-2] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesThreads The web application [followuph5] appears to have started a thread named [mysql-cj-abandoned-connection-cleanup] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:
java.lang.Object.wait(Native Method)
java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:143)
--
08-Sep-2022 18:04:32.209 INFO [Catalina-utility-1] org.apache.catalina.startup.HostConfig.undeploy Undeploying context [/followuph5]
08-Sep-2022 18:04:32.520 WARNING [Catalina-utility-1] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesJdbc The web application [followuph5] registered the JDBC driver [com.mysql.cj.jdbc.Driver] but failed to unregister it when the web application was stopped. To prevent a memory leak, the JDBC Driver has been forcibly unregistered.
08-Sep-2022 18:04:32.533 WARNING [Catalina-utility-1] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesThreads The web application [followuph5] appears to have started a thread named [mysql-cj-abandoned-connection-cleanup] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:
java.lang.Object.wait(Native Method)
java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:143)
--
08-Sep-2022 18:07:55.508 INFO [Catalina-utility-2] org.apache.catalina.startup.HostConfig.undeploy Undeploying context [/followuph5]
08-Sep-2022 18:07:55.846 INFO [Catalina-utility-2] org.apache.catalina.startup.HostConfig.deployWAR Deploying web application archive [/usr/local/tomcat/webapps/followuph5.war]
08-Sep-2022 18:08:02.973 INFO [Catalina-utility-2] org.apache.jasper.servlet.TldScanner.scanJars At least one JAR was scanned for TLDs yet contained no TLDs. Enable debug logging for thislogger for a complete list of JARs that were scanned but no TLDs were found in them. Skipping unneeded JARs during scanning can improve startup time and JSP compilation time.
08-Sep-2022 18:08:03.000 INFO [Catalina-utility-2] org.apache.catalina.startup.HostConfig.deployWAR Deployment of web application archive [/usr/local/tomcat/webapps/followuph5.war] has finished in [7,154] ms
08-Sep-2022 18:09:46.127 INFO [catalina-exec-50622] org.apache.coyote.http11.Http11Processor.service Error parsing HTTP request header
--
08-Sep-2022 22:37:27.864 INFO [Catalina-utility-2] org.apache.catalina.startup.HostConfig.undeploy Undeploying context [/followuph5]
08-Sep-2022 22:37:27.978 WARNING [Catalina-utility-2] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesJdbc The web application [followuph5] registered the JDBC driver [com.mysql.cj.jdbc.Driver] but failed to unregister it when the web application was stopped. To prevent a memory leak, the JDBC Driver has been forcibly unregistered.
08-Sep-2022 22:37:27.997 WARNING [Catalina-utility-2] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesThreads The web application [followuph5] appears to have started a thread named [mysql-cj-abandoned-connection-cleanup] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:
java.lang.Object.wait(Native Method)
java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:143)
--
08-Sep-2022 22:46:14.905 INFO [Catalina-utility-1] org.apache.catalina.startup.HostConfig.undeploy Undeploying context [/followuph5]
08-Sep-2022 22:46:15.237 INFO [Catalina-utility-1] org.apache.catalina.startup.HostConfig.deployWAR Deploying web application archive [/usr/local/tomcat/webapps/followuph5.war]
08-Sep-2022 22:46:22.902 INFO [Catalina-utility-1] org.apache.jasper.servlet.TldScanner.scanJars At least one JAR was scanned for TLDs yet contained no TLDs. Enable debug logging for thislogger for a complete list of JARs that were scanned but no TLDs were found in them. Skipping unneeded JARs during scanning can improve startup time and JSP compilation time.
08-Sep-2022 22:46:22.908 INFO [Catalina-utility-1] org.apache.catalina.startup.HostConfig.deployWAR Deployment of web application archive [/usr/local/tomcat/webapps/followuph5.war] has finished in [7,671] ms
08-Sep-2022 22:49:49.782 INFO [catalina-exec-52027] org.apache.coyote.http11.Http11Processor.service Error parsing HTTP request header
--
08-Sep-2022 23:02:25.278 INFO [Catalina-utility-2] org.apache.catalina.startup.HostConfig.undeploy Undeploying context [/followuph5]
08-Sep-2022 23:02:25.860 WARNING [Catalina-utility-2] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesJdbc The web application [followuph5] registered the JDBC driver [com.mysql.cj.jdbc.Driver] but failed to unregister it when the web application was stopped. To prevent a memory leak, the JDBC Driver has been forcibly unregistered.
08-Sep-2022 23:02:25.876 WARNING [Catalina-utility-2] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesThreads The web application [followuph5] appears to have started a thread named [mysql-cj-abandoned-connection-cleanup] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:
java.lang.Object.wait(Native Method)
java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:143)
--
08-Sep-2022 23:24:07.240 INFO [Catalina-utility-2] org.apache.catalina.startup.HostConfig.undeploy Undeploying context [/followuph5]
08-Sep-2022 23:24:07.269 WARNING [Catalina-utility-2] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesJdbc The web application [followuph5] registered the JDBC driver [com.mysql.cj.jdbc.Driver] but failed to unregister it when the web application was stopped. To prevent a memory leak, the JDBC Driver has been forcibly unregistered.
08-Sep-2022 23:24:07.286 WARNING [Catalina-utility-2] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesThreads The web application [followuph5] appears to have started a thread named [mysql-cj-abandoned-connection-cleanup] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:
java.lang.Object.wait(Native Method)
java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:143)
--
08-Sep-2022 23:31:49.037 INFO [Catalina-utility-2] org.apache.catalina.startup.HostConfig.undeploy Undeploying context [/followuph5]
08-Sep-2022 23:31:49.071 WARNING [Catalina-utility-2] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesJdbc The web application [followuph5] registered the JDBC driver [com.mysql.cj.jdbc.Driver] but failed to unregister it when the web application was stopped. To prevent a memory leak, the JDBC Driver has been forcibly unregistered.
08-Sep-2022 23:31:49.085 WARNING [Catalina-utility-2] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesThreads The web application [followuph5] appears to have started a thread named [mysql-cj-abandoned-connection-cleanup] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:
java.lang.Object.wait(Native Method)
java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:143)
可以看到我部署了多少遍进行测试
最重要的信息是undeploy Undeploying context [/followuph5],意思是说正在取消部署上下文followuph5
然后是Web应用程序 [followuph5] 注册了JDBC驱动程序 [com.mysql.cj.jdbc.Driver]，但在Web应用程序停止时无法注销它。 为防止内存泄漏，JDBC驱动程序已被强制取消注册。org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesThreads Web应用程序[followuph5]似乎启动了一个名为[mysql-cj-abandoned-connection-cleanup]的线程，但未能停止它。这很可能会造成内存泄漏。
原因就在于此
上网查找了解决方案
方案
添加一个监听器
package cn.juhe.listener;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import javax.servlet.annotation.WebListener;
import java.sql.Driver;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.Enumeration;
import com.mysql.jdbc.AbandonedConnectionCleanupThread;
@WebListener
public class ContextFinalizer implements ServletContextListener {
public void contextInitialized(ServletContextEvent sce) {
}
public void contextDestroyed(ServletContextEvent sce) {
Enumeration<Driver> drivers = DriverManager.getDrivers();
Driver d = null;
while (drivers.hasMoreElements()) {
try {
d = drivers.nextElement();
DriverManager.deregisterDriver(d);
} catch (SQLException ex) {
}
}
// 注意：mysql8版本的jar好像shutdown方法私有了，只能调用checkedShutdown或uncheckedShutdown
try {
AbandonedConnectionCleanupThread.checkedShutdown();
} catch (Exception e) {
e.printStackTrace();
}
}
}
注意点
- 需要注意的是，springboot <version>2.2.2.RELEASE</version>版本默认的是
mysql-connector-java 驱动是8.0.18版本的，如果添加上面的监听器，是没有AbandonedConnectionCleanupThread这个类的
解决办法是改为
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.41</version>
<scope>compile</scope>
</dependency>
- 此时还需要注意scope不能为runtime，不然，会提示找不到com.mysql.jdbc包
- application.properties配置中的spring.datasource.driver-class-name原来是可以不用填写的，现在要改为
spring.datasource.driver-class-name=com.mysql.jdbc.Driver，因为默认是com.mysql.cj.jdbc.Driver
本地测试效果
再次打包war包，从tomcat的webapp目录删除followuph5，没有关于jdbc驱动的提示了，启动也正常了
