使用google perf工具来排查堆外内存占用

2017-12-02

现象

线上机器内存不足，经常被系统oom killer干掉。

如果tomcat运行的好好的，突然被干掉了，没有任何线索，那么就可以使用下面的命令看看是不是oom killer搞的鬼

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jinfo使用

2017-11-26

查看最终生效的flag

sudo -u tomcat jinfo pid

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Attaching to process ID 30350, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 24.45-b08
...
...
sun.cpu.endian = little
package.access = sun.,org.apache.catalina.,org.apache.coyote.,org.apache.tomcat.,org.apache.jasper.,sun.beans.
sun.cpu.isalist = 

VM Flags:

-Djava.util.logging.config.file=/tomcat/www/application/conf/logging.properties -Xms6g -Xmx6g -Xmn4g -XX:PermSize=256m -XX:MaxPermSize=256M ... -Djava.io.tmpdir=/tomcat/www/application/temp

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executor总结

2017-11-19

shutdown()和shutdownNow()

shutdown()

shutdown()会尝试中断空闲的线程，并把ThreadPool的状态置成SHUTDOWN,
这个状态下，不能通过submit()或者execute()提交任务，但是正在执行的和任务队列中的任务还可以继续执行。

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Guava中的ThreadFactoryBuilder

2017-11-18

用法

java中自定义线程池时可以传入一个ThreadFactory，用来创建线程。

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/**
    * Creates a new {@code ThreadPoolExecutor} with the given initial
    * parameters and default rejected execution handler.
    *
    * @param corePoolSize the number of threads to keep in the pool, even
    *        if they are idle, unless {@code allowCoreThreadTimeOut} is set
    * @param maximumPoolSize the maximum number of threads to allow in the
    *        pool
    * @param keepAliveTime when the number of threads is greater than
    *        the core, this is the maximum time that excess idle threads
    *        will wait for new tasks before terminating.
    * @param unit the time unit for the {@code keepAliveTime} argument
    * @param workQueue the queue to use for holding tasks before they are
    *        executed.  This queue will hold only the {@code Runnable}
    *        tasks submitted by the {@code execute} method.
    * @param threadFactory the factory to use when the executor
    *        creates a new thread
    * @throws IllegalArgumentException if one of the following holds:<br>
    *         {@code corePoolSize < 0}<br>
    *         {@code keepAliveTime < 0}<br>
    *         {@code maximumPoolSize <= 0}<br>
    *         {@code maximumPoolSize < corePoolSize}
    * @throws NullPointerException if {@code workQueue}
    *         or {@code threadFactory} is null
    */
   public ThreadPoolExecutor(int corePoolSize,
                             int maximumPoolSize,
                             long keepAliveTime,
                             TimeUnit unit,
                             BlockingQueue<Runnable> workQueue,
                             ThreadFactory threadFactory) {
       this(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue,
            threadFactory, defaultHandler);
   }

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MAT-Ubuntu无法打开Report

2017-11-12

现象

可以运行Leak Suspects，可以看到报告文件确实生成了，但是无法打开，看error log如下:

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Unhandled event loop exception

org.eclipse.swt.SWTException: Failed to execute runnable (org.eclipse.swt.SWTError: No more handles [Browser style SWT.MOZILLA and Java system property org.eclipse.swt.browser.DefaultType=mozilla are not supported with GTK 3 as XULRunner is not ported for GTK 3 yet])
	at org.eclipse.swt.SWT.error(SWT.java:4491)
	at org.eclipse.swt.SWT.error(SWT.java:4406)
	at org.eclipse.swt.widgets.Synchronizer.runAsyncMessages(Synchronizer.java:138)
	at org.eclipse.swt.widgets.Display.runAsyncMessages(Display.java:3794)
	at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3433)
	at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$4.run(PartRenderingEngine.java:1127)
	at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:337)
	at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.run(PartRenderingEngine.java:1018)
	at org.eclipse.e4.ui.internal.workbench.E4Workbench.createAndRunUI(E4Workbench.java:156)
	at org.eclipse.ui.internal.Workbench$5.run(Workbench.java:694)
	at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:337)
	at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:606)
	at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:150)
	at org.eclipse.mat.ui.rcp.Application.start(Application.java:26)
	at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:196)
	at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:134)
	at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:104)
	at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:380)
	at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:235)
	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:498)
	at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:669)
	at org.eclipse.equinox.launcher.Main.basicRun(Main.java:608)
	at org.eclipse.equinox.launcher.Main.run(Main.java:1515)
	at org.eclipse.equinox.launcher.Main.main(Main.java:1488)
Caused by: org.eclipse.swt.SWTError: No more handles [Browser style SWT.MOZILLA and Java system property org.eclipse.swt.browser.DefaultType=mozilla are not supported with GTK 3 as XULRunner is not ported for GTK 3 yet]
	at org.eclipse.swt.SWT.error(SWT.java:4517)
	at org.eclipse.swt.browser.MozillaDelegate.<init>(MozillaDelegate.java:57)
	at org.eclipse.swt.browser.Mozilla.create(Mozilla.java:663)
	at org.eclipse.swt.browser.Browser.<init>(Browser.java:99)
	at org.eclipse.mat.ui.internal.panes.QueryTextResultPane.createPartControl(QueryTextResultPane.java:72)
	at org.eclipse.mat.ui.editor.MultiPaneEditor.addPage(MultiPaneEditor.java:585)
	at org.eclipse.mat.ui.editor.MultiPaneEditor.addPage(MultiPaneEditor.java:574)
	at org.eclipse.mat.ui.editor.MultiPaneEditor.addNewPage(MultiPaneEditor.java:496)
	at org.eclipse.mat.ui.QueryExecution.doDisplayResult(QueryExecution.java:300)
	at org.eclipse.mat.ui.QueryExecution.access$0(QueryExecution.java:240)
	at org.eclipse.mat.ui.QueryExecution$1.run(QueryExecution.java:144)
	at org.eclipse.swt.widgets.RunnableLock.run(RunnableLock.java:35)
	at org.eclipse.swt.widgets.Synchronizer.runAsyncMessages(Synchronizer.java:135)
	... 24 more

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使用greys来排查线上问题

2017-11-12

greys

greys的理念是将btrace常用的功能命令化，这样可以大大的节省排查问题的时间。

greys 安装

推荐使用网络安装:

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java8 Stream使用不当，导致文件没有关闭

2017-11-04

现象

线上巡查的时候，检查了线上机器的tomcat打开的文件列表，发现了一些问题。
一般来说，tomcat打开的文件就是一些jar包，日志文件, 动态库，socket等。因此用下面的命令查看下tomcat打开的文件

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