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为什么Tomcat在共享库开始时要慢得多？

java tomcat
2022-09-01 21:26:09

问题

我们有一个运行25个web应用程序，它们都共享具有相同版本的相同库（保证这永远不会改变！我认为，与其每个项目加载相同的库，不如将它们移动到这样可以减少所需的内存负载。Tomcat 7.0.35${catalina.home}/lib

然而，这是有代价的：每个Web应用程序的部署时间从5秒增加到2分钟，这是不可行的！

我做了一些阅读（例如类加载器HOW-TO），不幸的是，我无法找到一种方法来减少启动时间。有没有办法解决这个问题？

请求的分析信息

我运行了两种不同的情况，我将在这里介绍一些发现（如果您需要更多信息，请告诉我）：jstackjvisualvm

  • 特定于每个项目的库似乎加载了：
    运行该方法的线程的jstack输出：org.apache.catalina.loader.WebappClassLoader.findResourceInternal
    "localhost-startStop-1" daemon prio=10 tid=0x00007f17f8001800 nid=0x13b8 runnable [0x00007f183c800000]
   java.lang.Thread.State: RUNNABLE
        at java.text.MessageFormat.subformat(MessageFormat.java:1250)
        at java.text.MessageFormat.format(MessageFormat.java:819)
        at org.apache.naming.StringManager.getString(StringManager.java:145)
        at org.apache.naming.resources.BaseDirContext.lookup(BaseDirContext.java:500)
        at org.apache.naming.resources.ProxyDirContext.lookup(ProxyDirContext.java:310)
        at org.apache.catalina.loader.WebappClassLoader.findResourceInternal(WebappClassLoader.java:3011)
        at org.apache.catalina.loader.WebappClassLoader.findResource(WebappClassLoader.java:1262)
        at org.apache.catalina.loader.WebappClassLoader.getResourceAsStream(WebappClassLoader.java:1499)
        at org.apache.catalina.startup.ContextConfig.populateJavaClassCache(ContextConfig.java:2302)
        at org.apache.catalina.startup.ContextConfig.populateJavaClassCache(ContextConfig.java:2294)
        at org.apache.catalina.startup.ContextConfig.populateJavaClassCache(ContextConfig.java:2308)
        at org.apache.catalina.startup.ContextConfig.populateJavaClassCache(ContextConfig.java:2291)
        at org.apache.catalina.startup.ContextConfig.checkHandlesTypes(ContextConfig.java:2197)
        at org.apache.catalina.startup.ContextConfig.processAnnotationsStream(ContextConfig.java:2154)
        at org.apache.catalina.startup.ContextConfig.processAnnotationsJar(ContextConfig.java:2034)
        at org.apache.catalina.startup.ContextConfig.processAnnotationsUrl(ContextConfig.java:1990)
        at org.apache.catalina.startup.ContextConfig.processAnnotations(ContextConfig.java:1976)
        at org.apache.catalina.startup.ContextConfig.webConfig(ContextConfig.java:1326)
        at org.apache.catalina.startup.ContextConfig.configureStart(ContextConfig.java:882)
        - locked <0x00000007f52f3ec0> (a org.apache.catalina.startup.ContextConfig)
        at org.apache.catalina.startup.ContextConfig.lifecycleEvent(ContextConfig.java:379)
        at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:119)
        at org.apache.catalina.util.LifecycleBase.fireLifecycleEvent(LifecycleBase.java:90)
        at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5343)
        - locked <0x00000007f52f3bb8> (a org.apache.catalina.core.StandardContext)
        at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
        - locked <0x00000007f52f3bb8> (a org.apache.catalina.core.StandardContext)
        at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:902)
        at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:879)
        at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:636)
        at org.apache.catalina.startup.HostConfig.deployDirectory(HostConfig.java:1236)
        at org.apache.catalina.startup.HostConfig$DeployDirectory.run(HostConfig.java:1877)
        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)
        at java.util.concurrent.FutureTask.run(FutureTask.java:266)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
        at java.lang.Thread.run(Thread.java:745)

   Locked ownable synchronizers:
        - <0x00000007846dfc70> (a java.util.concurrent.ThreadPoolExecutor$Worker)

  • 在项目之间共享的库似乎被加载：
    这导致了令人难以置信的部署时间。JVisualVM 在项目部署期间为此方法显示 98%以上的“自用时间”。
    运行该方法的线程的 jstack 输出：at org.apache.catalina.loader.WebappClassLoader.getResourceAsStream
    "localhost-startStop-1" daemon prio=10 tid=0x00007f6280001000 nid=0x6ba3 runnable [0x00007f62c4950000]
   java.lang.Thread.State: RUNNABLE
        at java.lang.String.intern(Native Method)
        at java.util.jar.Attributes$Name.<init>(Attributes.java:466)
        at java.util.jar.Attributes.putValue(Attributes.java:168)
        at java.util.jar.Attributes.read(Attributes.java:421)
        at java.util.jar.Manifest.read(Manifest.java:251)
        at sun.security.util.SignatureFileVerifier.processImpl(SignatureFileVerifier.java:252)
        at sun.security.util.SignatureFileVerifier.process(SignatureFileVerifier.java:239)
        at java.util.jar.JarVerifier.processEntry(JarVerifier.java:307)
        at java.util.jar.JarVerifier.update(JarVerifier.java:218)
        at java.util.jar.JarFile.initializeVerifier(JarFile.java:345)
        at java.util.jar.JarFile.getInputStream(JarFile.java:412)
        - locked <0x00000007e8e9d890> (a sun.net.www.protocol.jar.URLJarFile)
        at sun.net.www.protocol.jar.JarURLConnection.getInputStream(JarURLConnection.java:162)
        at java.net.URLClassLoader.getResourceAsStream(URLClassLoader.java:233)
        at org.apache.catalina.loader.WebappClassLoader.getResourceAsStream(WebappClassLoader.java:1528)
        at org.apache.catalina.startup.ContextConfig.populateJavaClassCache(ContextConfig.java:2302)
        at org.apache.catalina.startup.ContextConfig.populateJavaClassCache(ContextConfig.java:2294)
        at org.apache.catalina.startup.ContextConfig.populateJavaClassCache(ContextConfig.java:2308)
        at org.apache.catalina.startup.ContextConfig.populateJavaClassCache(ContextConfig.java:2294)
        at org.apache.catalina.startup.ContextConfig.checkHandlesTypes(ContextConfig.java:2197)
        at org.apache.catalina.startup.ContextConfig.processAnnotationsStream(ContextConfig.java:2154)
        at org.apache.catalina.startup.ContextConfig.processAnnotationsJar(ContextConfig.java:2034)
        at org.apache.catalina.startup.ContextConfig.processAnnotationsUrl(ContextConfig.java:1990)
        at org.apache.catalina.startup.ContextConfig.processAnnotations(ContextConfig.java:1976)
        at org.apache.catalina.startup.ContextConfig.webConfig(ContextConfig.java:1326)
        at org.apache.catalina.startup.ContextConfig.configureStart(ContextConfig.java:882)
        - locked <0x00000007858db6e0> (a org.apache.catalina.startup.ContextConfig)
        at org.apache.catalina.startup.ContextConfig.lifecycleEvent(ContextConfig.java:379)
        at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:118)
        at org.apache.catalina.util.LifecycleBase.fireLifecycleEvent(LifecycleBase.java:91)
        at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5346)
        - locked <0x00000007858db318> (a org.apache.catalina.core.StandardContext)
        at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:153)
        - locked <0x00000007858db318> (a org.apache.catalina.core.StandardContext)
        at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:902)
        at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:879)
        at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:636)
        at org.apache.catalina.startup.HostConfig.deployDirectory(HostConfig.java:1236)
        at org.apache.catalina.startup.HostConfig$DeployDirectory.run(HostConfig.java:1877)
        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)
        at java.util.concurrent.FutureTask.run(FutureTask.java:266)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
        at java.lang.Thread.run(Thread.java:745)

   Locked ownable synchronizers:
        - <0x000000078460e618> (a java.util.concurrent.ThreadPoolExecutor$Worker)

    • 答案 1

    WebappClassLoader 首先在他自己的类路径上进行搜索。因此，对于不在本地类路径中的每个类，将查看所有 jar 文件。只有这样，它才会查看公共类装入器的委托。

    假设查看战争中的所有 jar 需要 x 个时间，对于其父类装入器的 jar，则需要 y 个时间。

    平均而言，从正确的类装入器加载类将花费一半的时间来扫描它们。

    从 WebappClassLoader 加载类需要 x/2 时间。

    从父类装入器装入类将采用 x + y/2。

    根据 x 和 y，您可以更改类装入器的使用顺序。如果 y 大于 x，则应保留默认设置，如果 x 大于，则可以尝试反转查找顺序。如果这样做，从公共类装入器装入类将花费 y/2 时间，但 WebappClassLoader 中的类将花费 y + x/2。

    WebbappClassLoader 有一个委托属性，用于将此设置设置为 true 应该可以解决问题。请参阅常见属性


    答案 2

    简而言之：为shared.loaderconf/catalina.properties

    shared.loader=shared/*.jar

    用更多的话说：

    # List of comma-separated paths defining the contents of the "shared"
# classloader. Prefixes should be used to define what is the repository type.
# Path may be relative to the CATALINA_BASE path or absolute. If left as blank,
# the "common" loader will be used as Catalina's "shared" loader.
# Examples:
#     "foo": Add this folder as a class repository
#     "foo/*.jar": Add all the JARs of the specified folder as class
#                  repositories
#     "foo/bar.jar": Add bar.jar as a class repository
# Please note that for single jars, e.g. bar.jar, you need the URL form
# starting with file:.
shared.loader=shared/*.jar

    默认情况下，Tomcat 6+ 具有层次结构 http://tomcat.apache.org/tomcat-7.0-doc/class-loader-howto.html

      Bootstrap
      |
   System
      |
   Common
   /     \
Webapp1   Webapp2 ...

    与 5.5 http://tomcat.apache.org/tomcat-5.5-doc/class-loader-howto.html 中的默认值进行比较

     Bootstrap
      |
   System
      |
   Common
  /      \
Catalina Shared
         /   \
    Webapp1  Webapp2 ...

    因此，通过启用共享位置，这将仅包含您的jars，并且与已经具有21个jar的Tomcat lib文件夹分开，您至少可以获得更清晰的jars视图。


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