java - 无法在 Tomcat webapp 中关闭 Neo4j Jetty 服务器

Question

目前我正在开发一个使用 Neo4j 的网络应用程序。我们的应用程序需要部署在 Tomcat 环境中(客户要求)。我们决定嵌入 Neo4j，因为这样我们就可以使用 Neo4j 提供的 Java API，它更容易部署并且我们获得改进的性能。但是，我们还需要访问 REST API，因为我们有一个用 Angular 编写的单页 ​​Web 应用程序，目前正在使用这个接口(interface)。然而，嵌入式 Neo4j 数据库不公开 REST api。 Neo4j-server 工件包含可以使用嵌入式图形数据库引导 jetty 服务器的代码。所以我们的 Tomcat webapp 正在启动一个 Jetty 服务器。我们可以通过一个端口(8080)上部署在 Tomcat 中的 webapp 和另一个端口(7474)上的 Neo4j REST 接口(interface)和 Neo4j 浏览器来访问 graphDb。虽然这有点奇怪但它工作正常，除了当我们试图停止我们的 webapp 时(例如重新部署)。当关闭我们的 webapp 时，我们从 tomcat 收到这些错误:

SEVERE: The web application [/chainmonitor] appears to have started a thread named [GC-Monitor] but has failed to stop it. This is very likely to create a memory leak.
jun 10, 2014 6:43:17 PM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
SEVERE: The web application [/chainmonitor] appears to have started a thread named [RRD4J Sync Pool [Thread-1]] but has failed to stop it. This is very likely to create a memory leak.
jun 10, 2014 6:43:17 PM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
SEVERE: The web application [/chainmonitor] appears to have started a thread named [Statistics Gatherer[primitives]] but has failed to stop it. This is very likely to create a memory leak.
jun 10, 2014 6:43:17 PM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
SEVERE: The web application [/chainmonitor] appears to have started a thread named [pool-1-thread-1] but has failed to stop it. This is very likely to create a memory leak.
jun 10, 2014 6:43:17 PM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
SEVERE: The web application [/chainmonitor] appears to have started a thread named [pool-1-thread-2] but has failed to stop it. This is very likely to create a memory leak.
jun 10, 2014 6:43:17 PM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
SEVERE: The web application [/chainmonitor] appears to have started a thread named [DateCache] but has failed to stop it. This is very likely to create a memory leak.
jun 10, 2014 6:43:17 PM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
SEVERE: The web application [/chainmonitor] appears to have started a thread named [qtp835579386-31-selector-3] but has failed to stop it. This is very likely to create a memory leak.
jun 10, 2014 6:43:17 PM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
SEVERE: The web application [/chainmonitor] appears to have started a thread named [qtp835579386-32-selector-0] but has failed to stop it. This is very likely to create a memory leak.
jun 10, 2014 6:43:17 PM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
SEVERE: The web application [/chainmonitor] appears to have started a thread named [qtp835579386-33-selector-1] but has failed to stop it. This is very likely to create a memory leak.
jun 10, 2014 6:43:17 PM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
SEVERE: The web application [/chainmonitor] appears to have started a thread named [qtp835579386-34-selector-2] but has failed to stop it. This is very likely to create a memory leak.
jun 10, 2014 6:43:17 PM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
SEVERE: The web application [/chainmonitor] appears to have started a thread named [qtp835579386-35-selector-4] but has failed to stop it. This is very likely to create a memory leak.
jun 10, 2014 6:43:17 PM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
SEVERE: The web application [/chainmonitor] appears to have started a thread named [qtp835579386-36-selector-5] but has failed to stop it. This is very likely to create a memory leak.
jun 10, 2014 6:43:17 PM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
SEVERE: The web application [/chainmonitor] appears to have started a thread named [qtp835579386-37-acceptor-0-ServerConnector@1425c689{HTTP/1.1}{localhost:7474}] but has failed to stop it. This is very likely to create a memory leak.
jun 10, 2014 6:43:17 PM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
SEVERE: The web application [/chainmonitor] appears to have started a thread named [qtp835579386-38-acceptor-1-ServerConnector@1425c689{HTTP/1.1}{localhost:7474}] but has failed to stop it. This is very likely to create a memory leak.
jun 10, 2014 6:43:17 PM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
SEVERE: The web application [/chainmonitor] appears to have started a thread named [HashSessionScavenger-0] but has failed to stop it. This is very likely to create a memory leak.
jun 10, 2014 6:43:17 PM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
SEVERE: The web application [/chainmonitor] appears to have started a thread named [qtp835579386-54] but has failed to stop it. This is very likely to create a memory leak.
jun 10, 2014 6:43:17 PM org.apache.catalina.loader.WebappClassLoader checkThreadLocalMapForLeaks
SEVERE: The web application [/chainmonitor] created a ThreadLocal with key of type [org.eclipse.jetty.http.HttpFields$1] (value [org.eclipse.jetty.http.HttpFields$1@4a3d3a5e]) and a value of type [org.eclipse.jetty.http.HttpFields.DateGenerator] (value [org.eclipse.jetty.http.HttpFields$DateGenerator@24f0137b]) but failed to remove it when the web application was stopped. Threads are going to be renewed over time to try and avoid a probable memory leak.
jun 10, 2014 6:43:17 PM org.apache.catalina.loader.WebappClassLoader checkThreadLocalMapForLeaks
SEVERE: The web application [/chainmonitor] created a ThreadLocal with key of type [scala.util.DynamicVariable$$anon$1] (value [scala.util.DynamicVariable$$anon$1@281a099d]) and a value of type [java.lang.Integer] (value [0]) but failed to remove it when the web application was stopped. Threads are going to be renewed over time to try and avoid a probable memory leak.
jun 10, 2014 6:43:17 PM org.apache.catalina.loader.WebappClassLoader checkThreadLocalMapForLeaks
SEVERE: The web application [/chainmonitor] created a ThreadLocal with key of type [scala.util.DynamicVariable$$anon$1] (value [scala.util.DynamicVariable$$anon$1@281a099d]) and a value of type [java.lang.Integer] (value [0]) but failed to remove it when the web application was stopped. Threads are going to be renewed over time to try and avoid a probable memory leak.
jun 10, 2014 6:43:17 PM org.apache.catalina.loader.WebappClassLoader checkThreadLocalMapForLeaks
SEVERE: The web application [/chainmonitor] created a ThreadLocal with key of type [scala.util.DynamicVariable$$anon$1] (value [scala.util.DynamicVariable$$anon$1@281a099d]) and a value of type [java.lang.Integer] (value [0]) but failed to remove it when the web application was stopped. Threads are going to be renewed over time to try and avoid a probable memory leak.
jun 10, 2014 6:43:17 PM org.apache.catalina.loader.WebappClassLoader checkThreadLocalMapForLeaks
SEVERE: The web application [/chainmonitor] created a ThreadLocal with key of type [scala.util.DynamicVariable$$anon$1] (value [scala.util.DynamicVariable$$anon$1@281a099d]) and a value of type [java.lang.Integer] (value [0]) but failed to remove it when the web application was stopped. Threads are going to be renewed over time to try and avoid a probable memory leak.
jun 10, 2014 6:43:17 PM org.apache.catalina.loader.WebappClassLoader checkThreadLocalMapForLeaks
SEVERE: The web application [/chainmonitor] created a ThreadLocal with key of type [scala.util.DynamicVariable$$anon$1] (value [scala.util.DynamicVariable$$anon$1@281a099d]) and a value of type [java.lang.Integer] (value [0]) but failed to remove it when the web application was stopped. Threads are going to be renewed over time to try and avoid a probable memory leak.
jun 10, 2014 6:43:17 PM org.apache.catalina.loader.WebappClassLoader checkThreadLocalMapForLeaks
SEVERE: The web application [/chainmonitor] created a ThreadLocal with key of type [scala.util.DynamicVariable$$anon$1] (value [scala.util.DynamicVariable$$anon$1@281a099d]) and a value of type [java.lang.Integer] (value [0]) but failed to remove it when the web application was stopped. Threads are going to be renewed over time to try and avoid a probable memory leak.
jun 10, 2014 6:43:17 PM org.apache.catalina.loader.WebappClassLoader checkThreadLocalMapForLeaks
SEVERE: The web application [/chainmonitor] created a ThreadLocal with key of type [scala.util.DynamicVariable$$anon$1] (value [scala.util.DynamicVariable$$anon$1@281a099d]) and a value of type [java.lang.Integer] (value [0]) but failed to remove it when the web application was stopped. Threads are going to be renewed over time to try and avoid a probable memory leak.
jun 10, 2014 6:43:17 PM org.apache.catalina.loader.WebappClassLoader checkThreadLocalMapForLeaks
SEVERE: The web application [/chainmonitor] created a ThreadLocal with key of type [scala.util.DynamicVariable$$anon$1] (value [scala.util.DynamicVariable$$anon$1@281a099d]) and a value of type [java.lang.Integer] (value [0]) but failed to remove it when the web application was stopped. Threads are going to be renewed over time to try and avoid a probable memory leak.
jun 10, 2014 6:43:17 PM org.apache.catalina.loader.WebappClassLoader checkThreadLocalMapForLeaks
SEVERE: The web application [/chainmonitor] created a ThreadLocal with key of type [scala.util.DynamicVariable$$anon$1] (value [scala.util.DynamicVariable$$anon$1@281a099d]) and a value of type [java.lang.Integer] (value [0]) but failed to remove it when the web application was stopped. Threads are going to be renewed over time to try and avoid a probable memory leak.
jun 10, 2014 6:43:17 PM org.apache.catalina.loader.WebappClassLoader checkThreadLocalMapForLeaks
SEVERE: The web application [/chainmonitor] created a ThreadLocal with key of type [scala.util.DynamicVariable$$anon$1] (value [scala.util.DynamicVariable$$anon$1@281a099d]) and a value of type [java.lang.Integer] (value [0]) but failed to remove it when the web application was stopped. Threads are going to be renewed over time to try and avoid a probable memory leak.
jun 10, 2014 6:43:17 PM org.apache.catalina.loader.WebappClassLoader checkThreadLocalMapForLeaks
SEVERE: The web application [/chainmonitor] created a ThreadLocal with key of type [scala.util.DynamicVariable$$anon$1] (value [scala.util.DynamicVariable$$anon$1@281a099d]) and a value of type [java.lang.Integer] (value [0]) but failed to remove it when the web application was stopped. Threads are going to be renewed over time to try and avoid a probable memory leak.
jun 10, 2014 6:43:17 PM org.apache.catalina.loader.WebappClassLoader checkThreadLocalMapForLeaks
SEVERE: The web application [/chainmonitor] created a ThreadLocal with key of type [scala.util.DynamicVariable$$anon$1] (value [scala.util.DynamicVariable$$anon$1@281a099d]) and a value of type [java.lang.Integer] (value [0]) but failed to remove it when the web application was stopped. Threads are going to be renewed over time to try and avoid a probable memory leak.
jun 10, 2014 6:43:17 PM org.apache.catalina.loader.WebappClassLoader checkThreadLocalMapForLeaks
SEVERE: The web application [/chainmonitor] created a ThreadLocal with key of type [scala.util.DynamicVariable$$anon$1] (value [scala.util.DynamicVariable$$anon$1@281a099d]) and a value of type [java.lang.Integer] (value [0]) but failed to remove it when the web application was stopped. Threads are going to be renewed over time to try and avoid a probable memory leak.
jun 10, 2014 6:43:17 PM org.apache.catalina.loader.WebappClassLoader checkThreadLocalMapForLeaks
SEVERE: The web application [/chainmonitor] created a ThreadLocal with key of type [scala.util.DynamicVariable$$anon$1] (value [scala.util.DynamicVariable$$anon$1@281a099d]) and a value of type [java.lang.Integer] (value [0]) but failed to remove it when the web application was stopped. Threads are going to be renewed over time to try and avoid a probable memory leak.
jun 10, 2014 6:43:17 PM org.apache.catalina.loader.WebappClassLoader checkThreadLocalMapForLeaks
SEVERE: The web application [/chainmonitor] created a ThreadLocal with key of type [scala.util.DynamicVariable$$anon$1] (value [scala.util.DynamicVariable$$anon$1@281a099d]) and a value of type [java.lang.Integer] (value [0]) but failed to remove it when the web application was stopped. Threads are going to be renewed over time to try and avoid a probable memory leak.
jun 10, 2014 6:43:17 PM org.apache.catalina.loader.WebappClassLoader checkThreadLocalMapForLeaks
SEVERE: The web application [/chainmonitor] created a ThreadLocal with key of type [scala.util.DynamicVariable$$anon$1] (value [scala.util.DynamicVariable$$anon$1@281a099d]) and a value of type [java.lang.Integer] (value [0]) but failed to remove it when the web application was stopped. Threads are going to be renewed over time to try and avoid a probable memory leak.
jun 10, 2014 6:43:17 PM org.apache.catalina.loader.WebappClassLoader checkThreadLocalMapForLeaks
SEVERE: The web application [/chainmonitor] created a ThreadLocal with key of type [scala.util.DynamicVariable$$anon$1] (value [scala.util.DynamicVariable$$anon$1@281a099d]) and a value of type [java.lang.Integer] (value [0]) but failed to remove it when the web application was stopped. Threads are going to be renewed over time to try and avoid a probable memory leak.
jun 10, 2014 6:43:27 PM org.apache.catalina.startup.HostConfig undeploy
INFO: Undeploying context [/chainmonitor]
jun 10, 2014 6:43:27 PM org.apache.catalina.startup.ExpandWar deleteDir
SEVERE: [C:\dev\apache-tomcat-7.0.54\webapps\chainmonitor\WEB-INF\lib] could not be completely deleted. The presence of the remaining files may cause problems
jun 10, 2014 6:43:27 PM org.apache.catalina.startup.ExpandWar deleteDir
SEVERE: [C:\dev\apache-tomcat-7.0.54\webapps\chainmonitor\WEB-INF] could not be completely deleted. The presence of the remaining files may cause problems
jun 10, 2014 6:43:27 PM org.apache.catalina.startup.ExpandWar deleteDir
SEVERE: [C:\dev\apache-tomcat-7.0.54\webapps\chainmonitor] could not be completely deleted. The presence of the remaining files may cause problems
jun 10, 2014 6:43:27 PM org.apache.catalina.startup.ExpandWar delete
SEVERE: [C:\dev\apache-tomcat-7.0.54\webapps\chainmonitor] could not be completely deleted. The presence of the remaining files may cause problems

我们的 pom.xml 看起来像这样:

    <dependency>
        <groupId>org.neo4j</groupId>
        <artifactId>neo4j</artifactId>
        <version>2.0.3</version>
    </dependency>
    <dependency>
        <groupId>org.neo4j.app</groupId>
        <artifactId>neo4j-server</artifactId>
        <version>2.0.3</version>
    </dependency>

这就是我们启动嵌入式数据库和启动 jetty 服务器的方式:

graphDb = (EmbeddedGraphDatabase) new GraphDatabaseFactory().
      newEmbeddedDatabaseBuilder(dataDir).loadPropertiesFromURL(Neo4jPropertiesUrl).newGraphDatabase();
bootstrapper = new WrappingNeoServerBootstrapper(graphDb);

目前 neo4j-server.properties 是空的。我没有尝试过许多不同的配置，但这样做似乎不是问题。

这就是我们停止嵌入式数据库和 jetty 服务器的方式:

    @Override
    public void contextDestroyed(ServletContextEvent event) {
​            graphDb.shutdown();
            bootstrapper.stop();
    }

这显然是由 Tomcat 的内存泄漏保护 ( http://wiki.apache.org/tomcat/MemoryLeakProtection ) 引起的。

结果是我们的webapp只能通过完全杀掉Tomcat进程(kill -9)才能重新部署，这是非常不可取的。

我们已经尝试了很多东西:

• 没有关闭嵌入式 grapbDb。没有效果。
• 没有明确关闭 Bootstrap 。没有效果。 ( Bootstrap 有自己的关闭钩子(Hook))
• 首先关闭 Bootstrap ，然后关闭嵌入式数据库。
• 自焚者:https://github.com/Neo4j/Neo4j/issues/1070 .该代码运行并破坏了 59 个线程本地值，但没有明显效果。有趣的是，当我在关机期间循环运行它一分钟时，它一直说它牺牲了 6 个值。对我来说，这表明此过程根本不起作用，因为 Neo4j 在关闭时需要一些时间。
• 在关闭后进行延迟。我们尝试这样做的原因是因为在 tomcat 收到关闭信号后，我们需要等待几秒钟才能真正终止进程，否则我们在下一次启动时会收到错误消息，提示我们的图形数据已损坏(消息未损坏)已正确关闭)。延迟 5 秒以上似乎也有影响，因为之后我们只得到 6 个严重错误，而不是 16 个。这也是我认为自焚过程根本不起作用的原因。
• 作为替代方案，我们尝试将嵌入式 Neo4j 添加到集群中，从而能够同时使用 REST api 和嵌入式 Neo4j。然而，在尝试让它工作大约四个小时后，我们放弃了。在嵌入式 Neo4j 数据库启动期间，我们的 Web 应用程序刚刚卡住。经过一些调试后，它看起来很像是 Neo4j 代码中的一个死锁。我们尝试将所有 HA 超时配置设置为一些较小的值，但没有效果。

问题是由 Neo4j jetty 服务器引起的。没有它就不会出现这个问题。不过我们需要 REST API。你知道我们如何解决这个问题吗？或者您是否有其他方法在 Tomcat 环境中使用嵌入式数据库和 REST API？

我们正在使用:

• Java:1.7.0_60
• Tomcat 7.0.54
• Neo4j:2.0.3(我们试过 2.1.1 但得到的结果完全一样)
• 在 Windows 7 和 Linux Redhat 上观察到相同的行为

Answer 1

您可能有尚未关闭的泄漏事务，然后 Neo4j 在关闭时最多等待 20 秒以关闭这些事务。

如果您等待 5 秒以上，哪些报告的问题仍然存在？