脚本宝典收集整理的这篇文章主要介绍了一则spring容器启动死锁问题(DefaultListableBeanFactory),脚本宝典觉得挺不错的,现在分享给大家,也给大家做个参考。
线上发现一个问题,应用在启动时会卡死,LOG上并没有什么异常输出,初判应该是死锁问题.
抓现场的thread dump文件, 确实是有两个线程有deadlock问题.
线程一
"HSFBizProcessor-8-thread-13" daemon prio=@H_406_18@10 tid=0x00007fc686a83000 nid=0x37128 waiting for monitor entry [0x000000004b7f3000] java.lang.Thread.state: BLOCKED (on object monitor) at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBeanDefinitionNames(DefaultListableBeanFactory.java:192) - waiting to lock <0x00000007707d84c8> (a java.util.concurrent.ConcurrentHashMap) at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBeanNamesForType(DefaultListableBeanFactory.java:209) at org.springframework.beans.factory.BeanFactoryUtils.beanNamesForTypeIncludingAncestors(BeanFactoryUtils.java:187) at org.springframework.beans.factory.support.DefaultListableBeanFactory.findAutowireCandidates(DefaultListableBeanFactory.java:652) at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:610) at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:412) at org.springframework.beans.factory.annotation.InjectionMetadata.injectFields(InjectionMetadata.java:105) at
线程二
"main": at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:180) - waiting to lock <0x00000007707ae6c0> (a java.util.concurrent.ConcurrentHashMap) at org.springframework.beans.factory.support.AbstractBeanFactory.isFactoryBean(AbstractBeanFactory.java:747) at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:422) - locked <0x00000007707d84c8> (a java.util.concurrent.ConcurrentHashMap) at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:728) at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:380) - locked <0x00000007707d7fc8> (a java.lang.Object) at org.springframework.web.context.ContextLoader.createWebApplicationContext(ContextLoader.java:255) at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:199)
栈文件的结尾已经指出了两个线程在竞争什么锁,
which is held by "main" "main": waiting to lock monitor 0x00007fc681220a08 (object 0x00000007707ae6c0, a java.util.concurrent.ConcurrentHashMap), which is held by "HSFBizProcessor-8-thread-13" "HSFBizProcessor-8-thread-13": waiting to lock monitor 0x00007fc686692438 (object 0x00000007707d84c8, a java.util.concurrent.ConcurrentHashMap), which is held by "main"
主要是线程HSFBizProcessor的DefaultListableBeanFactory.getBeanDefinitionNames(DefaultListableBeanFactory.java:192)
需要锁对象0x00000007707d84c8, 而这个对象已经被main的DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:422)
锁住了.
spring的版本是2.5.
这个问题的原因是spring在初始化singleton bean的时候,需要锁两个地方,第一个是
DefaultSingletonBeanRegistry中的singletonObjects:
/** Cache of singleton objects: bean name --> bean instance */ private final Map singletonObjects = CollectionFactory.createConcurrentMapIfPossible(16); ... synchronized (this.singletonObjects) { Object singletonObject = this.singletonObjects.get(beanName); if (singletonObject == null) { ... try { singletonObject = singletonFactory.getObject(); }
singletonObjects是DefaultSingletonBeanRegistry中的并发Map.
第二步需要锁DefaultListableBeanFactory中的beanDefinitionMap:
/** Map of bean definition objects, keyed by bean name */ private final Map beanDefinitionMap = CollectionFactory.createConcurrentMapIfPossible(16); ... public String[] getBeanDefinitionNames() { synchronized (this.beanDefinitionMap) { if (this.frozenBeanDefinitionNames != null) { return this.frozenBeanDefinitionNames; } ... } }
如果在应用启动时只有一个线程进入spring初始化bean时是没问题的, 但这里应用代码在spring的容器启动的同时,有另外一个main方法同时开始运行调用spring的DefaultListableBeanFactory.preInstantiateSingletons方法,两个线程两把锁,是有可能造成饥饿竞争的.
在spring容器外自行调用spring的创建bean方法要注意线程问题.
引申阅读:
Spring Bean Creation is Not Thread Safe
A Java Thread deadlock has occured
Performance bottleneck and potential thread deadlock in DefaultSingletonBeanRegistry
Spring deadlocks between DefaultListableBeanFactory and DefaultSingletonBeanRegistry
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