修复A Native Collection has not been disposed, resulting in a memory leak.

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No information on error with full stack traces enabled

Hello, I have an error of "A Native Collection has not been disposed, resulting in a memory leak. Enable Full StackTraces to get more details. (Filename: Line: 0)" I have enabled full stack traces on everything in the project settings and in the stack trace logging menu. However it still does not show anymore details. I have tried restarting the editor but it did not help. Any help would be great. Thanks for your time!

Edit: This has been fixed for me by going to Menu: Jobs -> Leak Detection -> Full Stack Traces (Expensive). SecondCobra has a picture if you need help. You may need to update jobs to see it, not sure if it was included in an update or always there.

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3个解答，截止LateNighterDK · 2021年04月04日 20:39

And to obtain the Jobs menu you need to install the experimental Entities package. Since its experimental it's not enough to enable preview packages in the Package manager. You have to install it via the "Add package by name" in the Package manager and know that its called "com.unity.entities".

Took my some hours to piece the scattered clues to this together from various forums and Unitys vague descriptions on DOTS/ECS.

Hope it helps someone out there.

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1个解答，截止lPVDl · 2021年09月08日 08:40

This can be done by changing property NativeLeakDetection.Mode. For example, via menu item MyProject > Jobs > Leak Detection With Stack Trace:

 See more at Unity API NativeLeakDetectionMode:

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0个解答，截止SecondCobra · 2020年10月10日 06:23

In case anyone else finds this question, it is turned on using the Menu: Jobs -> Leak Detection -> Full Stack Traces (Expensive).

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0个解答，截止the_rings_of_saturn · 05月26日 01:11

Still in Unity 2021.3.3f1 LTS! After installing "entities", I didn't see the option "Leak detection", so I restarted Unity. After restarting, I don't see either "Jobs" menu now. And I got this new error: Library\\PackageCache\\com.unity.entities@0.50.1-preview.2\\Unity.Entities\\RetainBlobAssetSystem.cs(6,5): error SGICE002: Seeing this error indicates a bug in the dots compiler. We'd appreciate a bug report (About->Report a Bug...). Thnx! <3 System.IO.IOException: Cannot create 'C:\\Users\\emili\\My project\\Library\\Bee\\artifacts\\1900b0aE.dag\\Unity.Entities.AdditionalFile.txt' because a file or directory with the same name already exists.

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转载网页：No information on error with full stack traces enabled - Unity Answers

tomcat启动过程报the JDBC Driver has been forcibly unregistered问题的修复过程

  最近两天在整理关于flume的总结文档，没有启动过tomcat。昨天晚上部署启动，发现报了如题的错误，全文如下：

严重: The web application [/oa-deploy] registered the JBDC driver [com.microsoft.sqlserver.jdbc.SQLServerDriver] but failed to unregister it when the web application was stopped. To prevent a memory leak, the JDBC Driver has been forcibly unregistered.
2016-3-10 9:49:08 org.apache.catalina.loader.WebappClassLoader clearReferencesJdbc
严重: The web application [/oa-deploy] registered the JBDC driver [com.mysql.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.
2016-3-10 9:49:08 org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
严重: The web application [/oa-deploy] appears to have started a thread named [Timer-1] but has failed to stop it. This is very likely to create a memory leak.
2016-3-10 9:49:08 org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
严重: The web application [/oa-deploy] appears to have started a thread named [Resource Destroyer in BasicResourcePool.close()] but has failed to stop it. This is very likely to create a memory leak.

   首先我怀疑可能与启动过程中的其他报错有关，在启动过程中频繁地报出了这样的错误：

2016-03-10 11:21:01,117 [main] DEBUG [com.opensymphony.xwork2.util.logging.commons.CommonsLogger.debug] The result type [com.fx.platform.web.struts.result.JsonResult] doesn‘t have a default param [DEFAULT_PARAM] defined!

java.lang.NoSuchFieldException: DEFAULT_PARAM

at java.lang.Class.getField(Class.java:1520)

at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.addResultTypes(XmlConfigurationProvider.java:578)

at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.addPackage(XmlConfigurationProvider.java:530)

at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.loadPackages(XmlConfigurationProvider.java:292)

at org.apache.struts2.config.StrutsXmlConfigurationProvider.loadPackages(StrutsXmlConfigurationProvider.java:112)

at com.opensymphony.xwork2.config.impl.DefaultConfiguration.reloadContainer(DefaultConfiguration.java:250)

at com.opensymphony.xwork2.config.ConfigurationManager.getConfiguration(ConfigurationManager.java:67)

at org.apache.struts2.dispatcher.Dispatcher.init_PreloadConfiguration(Dispatcher.java:446)

at org.apache.struts2.dispatcher.Dispatcher.init(Dispatcher.java:490)

at org.apache.struts2.dispatcher.ng.InitOperations.initDispatcher(InitOperations.java:74)

at org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.init(StrutsPrepareAndExecuteFilter.java:57)

at org.apache.catalina.core.ApplicationFilterConfig.getFilter(ApplicationFilterConfig.java:295)

at org.apache.catalina.core.ApplicationFilterConfig.setFilterDef(ApplicationFilterConfig.java:422)

at org.apache.catalina.core.ApplicationFilterConfig.<init>(ApplicationFilterConfig.java:115)

at org.apache.catalina.core.StandardContext.filterStart(StandardContext.java:4001)

at org.apache.catalina.core.StandardContext.start(StandardContext.java:4651)

at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1045)

at org.apache.catalina.core.StandardHost.start(StandardHost.java:785)

at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1045)

at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:445)

at org.apache.catalina.startup.Embedded.start(Embedded.java:825)

at org.codehaus.mojo.tomcat.AbstractRunMojo.startContainer(AbstractRunMojo.java:558)

at org.codehaus.mojo.tomcat.AbstractRunMojo.execute(AbstractRunMojo.java:255)

at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:101)

at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:209)

at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:153)

at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:145)

at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:84)

at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:59)

at org.apache.maven.lifecycle.internal.LifecycleStarter.singleThreadedBuild(LifecycleStarter.java:183)

at org.apache.maven.lifecycle.internal.LifecycleStarter.execute(LifecycleStarter.java:161)

at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:320)

at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:156)

at org.apache.maven.cli.MavenCli.execute(MavenCli.java:537)

at org.apache.maven.cli.MavenCli.doMain(MavenCli.java:196)

at org.apache.maven.cli.MavenCli.main(MavenCli.java:141)

at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)

at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)

at java.lang.reflect.Method.invoke(Method.java:597)

at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced(Launcher.java:290)

at org.codehaus.plexus.classworlds.launcher.Launcher.launch(Launcher.java:230)

at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode(Launcher.java:409)

at org.codehaus.plexus.classworlds.launcher.Launcher.main(Launcher.java:352)

   目测这段错误信息，包含了tomcat，也包括了我们自有的代码信息，这让我以为tomcat无法启动可能与该错误有关。我通读了代码，并将该代码与服务器和其他同事的代码对比，发现一致，理论上不是这里的问题。

   开始百度，以下是百度到的错误解决方案：

  1. registered the JDBC driver [com.mysql.jdbc.Driver] but failed to unregister it when the web applica问; 

  2. Closing BasicDataSource doesn‘t deregister JDBC driver, causing memory leak; 

  3. The web application [] registered the JDBC driver [com.mysql.jdbc.Driver] but failed to unregister i

  4. 异常 A web application registered the JBDC driver; 

  5. he web application [] registered the JDBC driver [com.mysql.jdbc.Driver] but;  


  6. tomcat关闭应用时的清理工作(1): JDBC Driver的检测和反注册

特别是5、6两篇文章思考的比较深入，介绍的也比较详细，给出了自己的解决方案，2则是apache官方的关于该问题的讨论方案，部分工程师认为这是tomcat的一个bug。

   我并不认为是bug，我认为是代码导致的问题，我向所有工程师发出求助邮件，其中一位高级工程师回复“检查C6 数据源是否畅通”，C6数据源是jdbc.properties里配置的三个数据源之一。昨天我确实因为使用无线网导致C6连接不上反映过该问题。我修改了C6数据源配置并且切换到有线内网，错误仍然存在。

   第六篇文章给了我较多启发，作者hongjiang应该是tomcat的一位资深研究人员，发表了多篇关于tomcat的研究文章，其对该错误的分析摘要如下：

        tomcat在关闭应用时，对资源做了一些清理，避免了泄露，这个工作主要是WebappClassLoader里做的，WebappClassLoader也实现自Lifecycle接口，在应用关闭时，会触发其stop方法，其中对JDBC Driver的清理，是clearReferencesJdbc方法，它检查当前WebappClassLoader加载过的，在关闭时未注销掉的JDBC Driver，给出警告信息，并强行将这些Driver反注册掉。如果servlet在初始化时注册了一个Driver，但销毁时未将这个Driver给反注册掉；这时不管是显式的通过命令来stop tomcat，还是因为设置了自动reload，而且恰好检查到应用有变，执行了reload的时候(reload也是对app context进行stop，然后再重新start)，就会被tomcat判断为泄露，给出警告并强制反注册Driver。

    要避免这个信息，应用或框架应该自己来保证在销毁时将JDBC Driver反注册掉。例如在destroy方法里：

@Override
	public void destroy() {
	    super.destroy();
	    try{
	        DriverManager.deregisterDriver(DriverManager.getDrivers().nextElement());
	    }catch(Exception e){
	        e.printStackTrace();
	    }
	}

   因为tomcat自带了DBCP数据库连接池，很多用户在使用DBCP时遇到了这个问题，并建议在 DBCP 的 BasicDataSource的close方法里执行反注册驱动的行为来解决这个警告。但DBCP的开发者认为这个应该是使用者的责任，不愿意接受这种建议。

         关闭reloadable重启该问题未再重现。

本文出自 “江南矿工技术空间” 博客，请务必保留此出处http://jncumter.blog.51cto.com/812546/1749568

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