本文是本系列的最后一篇。 看一下第1 部分和第2部分 。

在本系列的最后一篇文章中，我將展示如何在JDK中使用本機JMX支持來實現一種通知機制，該機制可以在HEAP內存超過特定閾值時向偵聽器發出警報。

正如我在上一篇文章中討論的那樣，這種方法是理想的，因為它是推式而不是拉式，不是侵入式的，并且對應用程序的計算需求最小。

這些是本文說明的解決方案的關鍵組件：

• MemoryWarningService：此組件充當偵聽器，并向Memory MBean注冊其自身以接收通知。 可以使用介于0到1之間的百分比形式的閾值（其中1為100％）進行配置
• MemoryThreadDumper：當通知MemoryWarningService HEAP使用量超過閾值并且其職責是將線程轉儲寫入文件時，將調用此組件。
• MemoryWarningServiceConfigurator：此組件是MBean，它公開一種用于更改MemoryWarningService閾值的方法。

該解決方案還提供用于在測試應用程序時填充HEAP的MemoryHeapFiller類和用于引導Spring環境的MemTest類。

當應用程序運行時（使用MemoryHeapFiller設置），您可以在URL上觸發JConsole：service：jmx：rmi：// localhost / jndi / rmi：// localhost：8888 / jemosJmxConnector以jemosAdmin / secure連接并更改閾值各種價值。

該代碼不是用于生產的：它不健壯，缺少許多注釋，并且寫入線程轉儲的文件名是硬編碼的。 但是，它代表了一個很好的起點。

該代碼附在下面。 您將需要Maven來構建它。

下載Jemos-jmx-experiments-0.0.1-SNAPSHOT-project

我嘗試了一個初始閾值為0.5的場景，將其更改為0.3，然后更改為0.8。 結果如下所示：

2011-08-15 21:53:21 ClassPathXmlApplicationContext [INFO] Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@a4a63d8: startup date [Mon Aug 15 21:53:21 BST 2011]; root of context hierarchy 2011-08-15 21:53:21 XmlBeanDefinitionReader [INFO] Loading XML bean definitions from class path resource [jemos-jmx-appCtx.xml] 2011-08-15 21:53:21 PropertyPlaceholderConfigurer [INFO] Loading properties file from class path resource [jemos-jmx.properties] 2011-08-15 21:53:21 PropertyPlaceholderConfigurer [INFO] Loading properties file from URL [file:/C:/Users/mtedone/.secure/jmxconnector-credentials.properties] 2011-08-15 21:53:21 ThreadPoolTaskScheduler [INFO] Initializing ExecutorService 'myScheduler' 2011-08-15 21:53:21 ClassPathXmlApplicationContext [INFO] Bean 'myScheduler' of type [class org.springframework.scheduling.concurrent.ThreadPoolTaskScheduler] is not eligible for getting processed by all BeanPostProcessors (for example: not eligible for auto-proxying) 2011-08-15 21:53:21 DefaultListableBeanFactory [INFO] Pre-instantiating singletons in org.springframework.beans.factory.support.DefaultListableBeanFactory@30296f76: defining beans [propertyConfigurer,loggerConfigurator,memoryWarningServiceConfigurator,memoryHeapFiller,memoryThreadDumper,org.springframework.context.annotation.internalConfigurationAnnotationProcessor,org.springframework.context.annotation.internalAutowiredAnnotationProcessor,org.springframework.context.annotation.internalRequiredAnnotationProcessor,org.springframework.context.annotation.internalCommonAnnotationProcessor,mbeanExporter,jemosJmxServer,rmiRegistry,clientConnector,memoryMxBean,memoryWarningService,org.springframework.scheduling.annotation.internalAsyncAnnotationProcessor,org.springframework.scheduling.annotation.internalScheduledAnnotationProcessor,myScheduler]; root of factory hierarchy 2011-08-15 21:53:21 AnnotationMBeanExporter [INFO] Registering beans for JMX exposure on startup 2011-08-15 21:53:21 RmiRegistryFactoryBean [INFO] Looking for RMI registry at port '8888' 2011-08-15 21:53:23 RmiRegistryFactoryBean [INFO] Could not detect RMI registry - creating new one 2011-08-15 21:53:23 ConnectorServerFactoryBean [INFO] JMX connector server started: javax.management.remote.rmi.RMIConnectorServer@4355d3a3 2011-08-15 21:53:23 AnnotationMBeanExporter [INFO] Bean with name 'jemosJmxServer' has been autodetected for JMX exposure 2011-08-15 21:53:23 AnnotationMBeanExporter [INFO] Bean with name 'loggerConfigurator' has been autodetected for JMX exposure 2011-08-15 21:53:23 AnnotationMBeanExporter [INFO] Bean with name 'memoryWarningServiceConfigurator' has been autodetected for JMX exposure 2011-08-15 21:53:23 AnnotationMBeanExporter [INFO] Located managed bean 'loggerConfigurator': registering with JMX server as MBean [jemos.mbeans:type=config,name=LoggingConfiguration] 2011-08-15 21:53:23 AnnotationMBeanExporter [INFO] Located MBean 'jemosJmxServer': registering with JMX server as MBean [jemos.mbeans:name=jemosJmxServer,type=RMIConnectorServer] 2011-08-15 21:53:23 AnnotationMBeanExporter [INFO] Located managed bean 'memoryWarningServiceConfigurator': registering with JMX server as MBean [jemos.mbeans:type=config,name=MemoryWarningServiceConfiguration] 2011-08-15 21:53:23 MemoryWarningService [INFO] Percentage is: 0.5 2011-08-15 21:53:23 MemoryWarningService [INFO] Listener added to JMX bean Adding data... Adding data... Adding data... Adding data... Adding data... Adding data... Adding data... 2011-08-15 21:53:37 MemoryWarningService [INFO] Percentage is: 0.3 2011-08-15 21:53:37 MemoryWarningServiceConfigurator [INFO] Memory threshold set to 0.3 Adding data... 2011-08-15 21:53:38 MemoryWarningService [WARN] Memory usage low!!! 2011-08-15 21:53:38 MemoryWarningService [WARN] percentageUsed = 0.3815679398794023 2011-08-15 21:53:38 MemoryThreadDumper [WARN] Stacks dumped to: C:/tmp/stacks.dump Adding data... Adding data... Adding data... 2011-08-15 21:53:45 MemoryWarningService [INFO] Percentage is: 0.8 2011-08-15 21:53:45 MemoryWarningServiceConfigurator [INFO] Memory threshold set to 0.8 Adding data... Adding data... Adding data... Adding data... Adding data... Adding data... Adding data... 2011-08-15 21:54:01 MemoryWarningService [WARN] Memory usage low!!! 2011-08-15 21:54:01 MemoryWarningService [WARN] percentageUsed = 0.8383333266727508 2011-08-15 21:54:02 MemoryThreadDumper [WARN] Stacks dumped to: C:/tmp/stacks.dump Adding data... Adding data... Adding data... Exception in thread "JMX server connection timeout 24" java.lang.OutOfMemoryError: Java heap space

內存警告服務

package uk.co.jemos.experiments.jmx;import java.lang.management.ManagementFactory; import java.lang.management.MemoryNotificationInfo; import java.lang.management.MemoryPoolMXBean; import java.lang.management.MemoryType;import javax.annotation.PostConstruct; import javax.management.Notification; import javax.management.NotificationEmitter; import javax.management.NotificationListener;import org.springframework.beans.factory.annotation.Autowired;/*** A component which sends notifications when the HEAP memory is above a certain* threshold.* * @author mtedone* */ public class MemoryWarningService implements NotificationListener {/** This bean's name */public static final String MBEAN_NAME = "jemos.mbeans:type=monitoring,name=MemoryWarningService";/** The application logger */private static final org.apache.log4j.Logger LOG = org.apache.log4j.Logger.getLogger(MemoryWarningService.class);@Autowiredprivate NotificationEmitter memoryMxBean;@Autowiredprivate MemoryThreadDumper threadDumper;/** A pool of Memory MX Beans specialised in HEAP management */private static final MemoryPoolMXBean tenuredGenPool = findTenuredGenPool();/*** {@inheritDoc}*/@Overridepublic void handleNotification(Notification notification, Object handback) {if (notification.getType().equals(MemoryNotificationInfo.MEMORY_THRESHOLD_EXCEEDED)) {long maxMemory = tenuredGenPool.getUsage().getMax();long usedMemory = tenuredGenPool.getUsage().getUsed();LOG.warn("Memory usage low!!!");double percentageUsed = (double) usedMemory / maxMemory;LOG.warn("percentageUsed = " + percentageUsed);threadDumper.dumpStacks();} else {LOG.info("Other notification received..."+ notification.getMessage());}}/*** It sets the threshold percentage.* * @param percentage*/public void setPercentageUsageThreshold(double percentage) {if (percentage <= 0.0 || percentage > 1.0) {throw new IllegalArgumentException("Percentage not in range");} else {LOG.info("Percentage is: " + percentage);}long maxMemory = tenuredGenPool.getUsage().getMax();long warningThreshold = (long) (maxMemory * percentage);tenuredGenPool.setUsageThreshold(warningThreshold);}@PostConstructpublic void completeSetup() {memoryMxBean.addNotificationListener(this, null, null);LOG.info("Listener added to JMX bean");}/*** Tenured Space Pool can be determined by it being of type HEAP and by it* being possible to set the usage threshold.*/private static MemoryPoolMXBean findTenuredGenPool() {for (MemoryPoolMXBean pool : ManagementFactory.getMemoryPoolMXBeans()) {// I don't know whether this approach is better, or whether// we should rather check for the pool name "Tenured Gen"?if (pool.getType() == MemoryType.HEAP&& pool.isUsageThresholdSupported()) {return pool;}}throw new AssertionError("Could not find tenured space");}}

內存線程轉儲器

package uk.co.jemos.experiments.jmx;import java.io.BufferedWriter; import java.io.File; import java.io.FileWriter; import java.io.IOException; import java.io.Writer; import java.lang.management.ManagementFactory; import java.lang.management.ThreadInfo; import java.lang.management.ThreadMXBean; import java.text.SimpleDateFormat; import java.util.Date; import java.util.HashMap; import java.util.Map;import org.apache.commons.io.IOUtils; import org.springframework.stereotype.Component;/*** This component dumps the thread stack to the file system.* * @author mtedone* */ @Component public class MemoryThreadDumper {/** The application logger */private static final org.apache.log4j.Logger LOG = org.apache.log4j.Logger.getLogger(MemoryThreadDumper.class);/*** It dumps the Thread stacks* * @throws IOException*/public void dumpStacks() {// hard-coded: This needs to be changed to a property or somethingString stackFileName = "C:/tmp/stacks.dump";ThreadMXBean mxBean = ManagementFactory.getThreadMXBean();ThreadInfo[] threadInfos = mxBean.getThreadInfo(mxBean.getAllThreadIds(), 0);Map<Long, ThreadInfo> threadInfoMap = new HashMap<Long, ThreadInfo>();for (ThreadInfo threadInfo : threadInfos) {threadInfoMap.put(threadInfo.getThreadId(), threadInfo);}File dumpFile = new File(stackFileName);BufferedWriter writer = null;try {writer = new BufferedWriter(new FileWriter(dumpFile));this.dumpTraces(mxBean, threadInfoMap, writer);LOG.warn("Stacks dumped to: " + stackFileName);} catch (IOException e) {throw new IllegalStateException("An exception occurred while writing the thread dump");} finally {IOUtils.closeQuietly(writer);}}private void dumpTraces(ThreadMXBean mxBean,Map<Long, ThreadInfo> threadInfoMap, Writer writer)throws IOException {Map<Thread, StackTraceElement[]> stacks = Thread.getAllStackTraces();writer.write("Dump of "+ stacks.size()+ " thread at "+ new SimpleDateFormat("yyyy/MM/dd HH:mm:ss z").format(new Date(System.currentTimeMillis())) + "\n\n");for (Map.Entry<Thread, StackTraceElement[]> entry : stacks.entrySet()) {Thread thread = entry.getKey();writer.write("\"" + thread.getName() + "\" prio="+ thread.getPriority() + " tid=" + thread.getId() + " "+ thread.getState() + " "+ (thread.isDaemon() ? "deamon" : "worker") + "\n");ThreadInfo threadInfo = threadInfoMap.get(thread.getId());if (threadInfo != null) {writer.write(" native=" + threadInfo.isInNative()+ ", suspended=" + threadInfo.isSuspended()+ ", block=" + threadInfo.getBlockedCount() + ", wait="+ threadInfo.getWaitedCount() + "\n");writer.write(" lock=" + threadInfo.getLockName()+ " owned by " + threadInfo.getLockOwnerName() + " ("+ threadInfo.getLockOwnerId() + "), cpu="+ mxBean.getThreadCpuTime(threadInfo.getThreadId())/ 1000000L + ", user="+ mxBean.getThreadUserTime(threadInfo.getThreadId())/ 1000000L + "\n");}for (StackTraceElement element : entry.getValue()) {writer.write(" ");writer.write(element.toString());writer.write("\n");}writer.write("\n");}}}

內存服務配置MBean

package uk.co.jemos.experiments.jmx.mbeans;import org.springframework.beans.BeansException; import org.springframework.context.ApplicationContext; import org.springframework.context.ApplicationContextAware; import org.springframework.jmx.export.annotation.ManagedOperation; import org.springframework.jmx.export.annotation.ManagedOperationParameter; import org.springframework.jmx.export.annotation.ManagedOperationParameters; import org.springframework.jmx.export.annotation.ManagedResource; import org.springframework.stereotype.Component;import uk.co.jemos.experiments.jmx.MemoryWarningService;@Component @ManagedResource(objectName = MemoryWarningServiceConfigurator.MBEAN_NAME, // description = "Allows clients to set the memory threshold") public class MemoryWarningServiceConfigurator implementsApplicationContextAware {/** The application logger */private static final org.apache.log4j.Logger LOG = org.apache.log4j.Logger.getLogger(MemoryWarningServiceConfigurator.class);public static final String MBEAN_NAME = "jemos.mbeans:type=config,name=MemoryWarningServiceConfiguration";private ApplicationContext ctx;@ManagedOperation(description = "Sets the memory threshold for the memory warning system")@ManagedOperationParameters({ @ManagedOperationParameter(description = "The memory threshold", name = "memoryThreshold"), })public void setMemoryThreshold(double memoryThreshold) {MemoryWarningService memoryWarningService = (MemoryWarningService) ctx.getBean("memoryWarningService");memoryWarningService.setPercentageUsageThreshold(memoryThreshold);LOG.info("Memory threshold set to " + memoryThreshold);}@Overridepublic void setApplicationContext(ApplicationContext applicationContext)throws BeansException {ctx = applicationContext;}}

Spring配置

<?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://www.springframework.org/schema/context"xmlns:util="http://www.springframework.org/schema/util"xmlns:task="http://www.springframework.org/schema/task"xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsdhttp://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.0.xsdhttp://www.springframework.org/schema/task http://www.springframework.org/schema/task/spring-task-3.0.xsdhttp://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-3.0.xsd"><bean id="propertyConfigurer" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer" ><property name="locations"><list><value>classpath:jemos-jmx.properties</value><value>file:///${user.home}/.secure/jmxconnector-credentials.properties</value></list></property></bean><context:component-scan base-package="uk.co.jemos.experiments.jmx" /><context:mbean-export default-domain="jemos.mbeans" /><bean id="jemosJmxServer" class="org.springframework.jmx.support.ConnectorServerFactoryBean" depends-on="rmiRegistry"><property name="objectName" value="connector:name=rmi" /><property name="serviceUrl"value="service:jmx:rmi://localhost/jndi/rmi://localhost:${jemos.jmx.rmi.port}/jemosJmxConnector" /><property name="environment"><!-- the following is only valid when the sun jmx implementation is used --><map><entry key="jmx.remote.x.password.file" value="${user.home}/.secure/jmxremote.password" /><entry key="jmx.remote.x.access.file" value="${user.home}/.secure/jmxremote.access" /></map></property></bean><bean id="rmiRegistry" class="org.springframework.remoting.rmi.RmiRegistryFactoryBean"><property name="port" value="${jemos.jmx.rmi.port}" /></bean><bean id="clientConnector" class="org.springframework.jmx.support.MBeanServerConnectionFactoryBean" depends-on="jemosJmxServer"><property name="serviceUrl"value="service:jmx:rmi://localhost/jndi/rmi://localhost:${jemos.jmx.rmi.port}/jemosJmxConnector" /><property name="environment"><map><entry key="jmx.remote.credentials"><beanfactory-method="commaDelimitedListToStringArray"><constructor-arg value="${jmx.username},${jmx.password}" /></bean></entry></map></property></bean><bean id="memoryMxBean" class="java.lang.management.ManagementFactory"factory-method="getMemoryMXBean" /><bean id="memoryWarningService" class="uk.co.jemos.experiments.jmx.MemoryWarningService"><property name="percentageUsageThreshold" value="0.5" /></bean><task:annotation-driven scheduler="myScheduler" /> <task:scheduler id="myScheduler" pool-size="10" /> </beans>

參考： JMX和Spring –我們的JCG合作伙伴 Marco Tedone的第3部分 ，位于Marco Tedone的博客博客中。

翻譯自: https://www.javacodegeeks.com/2012/07/jmx-and-spring-part-3.html

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