JDK8下，触发computeIfAbsent的BUG，会造成CPU100%

[xshiyu]

版本：spring-cloud-starter-dubbo-2.2.6.RELEASE
过程：启动的过程中，JVM会卡着不动，导致CPU 100%，无法启动

堆栈信息：
"main" #1 prio=5 os_prio=31 tid=0x00007fcb5a80b800 nid=0x2903 runnable [0x00007000006ca000]
java.lang.Thread.State: RUNNABLE
at java.util.concurrent.ConcurrentHashMap.computeIfAbsent(ConcurrentHashMap.java:1674)

• locked <0x0000000773e2def8> (a java.util.concurrent.ConcurrentHashMap$ReservationNode)
  at com.alibaba.cloud.dubbo.service.DubboMetadataServiceProxy.createProxyIfAbsent(DubboMetadataServiceProxy.java:140)
  at com.alibaba.cloud.dubbo.service.DubboMetadataServiceProxy.createProxyIfAbsent(DubboMetadataServiceProxy.java:130)
  at com.alibaba.cloud.dubbo.service.DubboMetadataServiceProxy.getProxy(DubboMetadataServiceProxy.java:99)
  at com.alibaba.cloud.dubbo.service.DubboMetadataServiceProxy.getProxy0(DubboMetadataServiceProxy.java:164)
  at com.alibaba.cloud.dubbo.service.DubboMetadataServiceProxy.getProxy(DubboMetadataServiceProxy.java:160)
  at com.alibaba.cloud.dubbo.metadata.repository.DubboServiceMetadataRepository.getProxy(DubboServiceMetadataRepository.java:266)
  at com.alibaba.cloud.dubbo.metadata.repository.DubboServiceMetadataRepository.getServiceRestMetadataSet(DubboServiceMetadataRepository.java:576)
  at com.alibaba.cloud.dubbo.metadata.repository.DubboServiceMetadataRepository.initDubboRestServiceMetadataRepository(DubboServiceMetadataRepository.java:471)
  at com.alibaba.cloud.dubbo.metadata.repository.DubboServiceMetadataRepository.initializeMetadata(DubboServiceMetadataRepository.java:262)
  at com.alibaba.cloud.dubbo.metadata.repository.DubboServiceMetadataRepository$$Lambda$1141/1205751246.accept(Unknown Source)
  at java.lang.Iterable.forEach(Iterable.java:75)
  at com.alibaba.cloud.dubbo.metadata.repository.DubboServiceMetadataRepository.initializeMetadata(DubboServiceMetadataRepository.java:251)
  at com.alibaba.cloud.dubbo.metadata.repository.DubboServiceMetadataRepository$$FastClassBySpringCGLIB$$4ef4b7bd.invoke()
  at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:218)
  at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:771)
  at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:163)
  at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.proceed(CglibAopProxy.java:749)
  at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:139)
  at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
  at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.proceed(CglibAopProxy.java:749)
  at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:691)
  at com.alibaba.cloud.dubbo.metadata.repository.DubboServiceMetadataRepository$$EnhancerBySpringCGLIB$$8f342aa4.initializeMetadata()
  at com.alibaba.cloud.dubbo.registry.DubboCloudRegistry.preInit(DubboCloudRegistry.java:150)
  at co m.alibaba.cloud.dubbo.registry.DubboCloudRegistry.doRegister(DubboCloudRegistry.java:185)
• locked <0x000000077efbe7d8> (a com.alibaba.cloud.dubbo.registry.DubboCloudRegistry)
  at org.apache.dubbo.registry.support.FailbackRegistry.register(FailbackRegistry.java:240)
  at org.apache.dubbo.registry.ListenerRegistryWrapper.register(ListenerRegistryWrapper.java:57)
  at org.apache.dubbo.registry.integration.RegistryProtocol.doRefer(RegistryProtocol.java:466)
  at org.apache.dubbo.registry.integration.RegistryProtocol.refer(RegistryProtocol.java:454)
  at org.apache.dubbo.rpc.protocol.ProtocolListenerWrapper.refer(ProtocolListenerWrapper.java:72)
  at org.apache.dubbo.rpc.protocol.ProtocolFilterWrapper.refer(ProtocolFilterWrapper.java:161)
  at org.apache.dubbo.qos.protocol.QosProtocolWrapper.refer(QosProtocolWrapper.java:73)
  at org.apache.dubbo.rpc.Protocol$Adaptive.refer(Protocol$Adaptive.java)
  at org.apache.dubbo.config.ReferenceConfig.createProxy(ReferenceConfig.java:367)
  at org.apache.dubbo.config.ReferenceConfig.init(ReferenceConfig.java:305)
• locked <0x000000077899af80> (a org.apache.dubbo.config.spring.ReferenceBean)
  at org.apache.dubbo.config.ReferenceConfig.get(ReferenceConfig.java:205)
• locked <0x000000077899af80> (a org.apache.dubbo.config.spring.ReferenceBean)
  at com.alibaba.cloud.dubbo.service.DubboGenericServiceFactory.create(DubboGenericServiceFactory.java:84)
  at com.alibaba.cloud.dubbo.service.DubboMetadataServiceInvocationHandler.(DubboMetadataServiceInvocationHandler.java:40)
  at com.alibaba.cloud.dubbo.service.DubboMetadataServiceProxy.createProxy(DubboMetadataServiceProxy.java:192)
  at com.alibaba.cloud.dubbo.service.DubboMetadataServiceProxy.lambda$createProxyIfAbsent$0(DubboMetadataServiceProxy.java:141)
  at com.alibaba.cloud.dubbo.service.DubboMetadataServiceProxy$$Lambda$1067/1533182537.apply(Unknown Source)
  at java.util.concurrent.ConcurrentHashMap.computeIfAbsent(ConcurrentHashMap.java:1660)
• locked <0x0000000773e2def8> (a java.util.concurrent.ConcurrentHashMap$ReservationNode)
  at com.alibaba.cloud.dubbo.service.DubboMetadataServiceProxy.createProxyIfAbsent(DubboMetadataServiceProxy.java:140)
  at com.alibaba.cloud.dubbo.service.DubboMetadataServiceProxy.createProxyIfAbsent(DubboMetadataServiceProxy.java:130)
  at com.alibaba.cloud.dubbo.service.DubboMetadataServiceProxy.getProxy(DubboMetadataServiceProxy.java:99)
  at com.alibaba.cloud.dubbo.service.DubboMetadataServiceProxy.getProxy0(DubboMetadataServiceProxy.java:164)
  at com.alibaba.cloud.dubbo.service.DubboMetadataServiceProxy.getProxy(DubboMetadataServiceProxy.java:160)
  at com.alibaba.cloud.dubbo.metadata.repository.DubboServiceMetadataRepository.getProxy(DubboServiceMetadataRepository.java:266)
  at com.alibaba.cloud.dubbo.metadata.repository.DubboServiceMetadataRepository.getServiceRestMetadataSet(DubboServiceMetadataRepository.java:576)
  at com.alibaba.cloud.dubbo.metadata.repository.DubboServiceMetadataRepository.initDubboRestServiceMetadataRepository(DubboServiceMetadataRepository.java:471)
  at com.alibaba.cloud.dubbo.metadata.repository.DubboServiceMetadataRepository.initializeMetadata(DubboServiceMetadataRepository.java:262)
  at com.alibaba.cloud.dubbo.metadata.repository.DubboServiceMetadataRepository$$FastClassBySpringCGLIB$$4ef4b7bd.invoke()
  at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:218)
  at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:771)
  at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:163)
  at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.proceed(CglibAopProxy.java:749)
  at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:139)
  at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
  at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.proceed(CglibAopProxy.java:749)
  at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:691)
  at com.alibaba.cloud.dubbo.metadata.repository.DubboServiceMetadataRepository$$EnhancerBySpringCGLIB$$8f342aa4.initializeMetadata()
  at com.alibaba.cloud.dubbo.openfeign.TargeterInvocationHandler.createDubboInvocationHandler(TargeterInvocationHandler.java:140)
  at com.alibaba.cloud.dubbo.openfeign.TargeterInvocationHandler.createDubboProxyIfRequired(TargeterInvocationHandler.java:103)
  at com.alibaba.cloud.dubbo.openfeign.TargeterInvocationHandler.invoke(TargeterInvocationHandler.java:97)
  at org.springframework.cloud.openfeign.$Proxy236.target(Unknown Source)
  at org.springframework.cloud.openfeign.FeignClientFactoryBean.loadBalance(FeignClientFactoryBean.java:318)
  at org.springframework.cloud.openfeign.FeignClientFactoryBean.getTarget(FeignClientFactoryBean.java:347)
  at org.springframework.cloud.openfeign.FeignClientFactoryBean.getObject(FeignClientFactoryBean.java:327)
  at org.springframework.beans.factory.support.FactoryBeanRegistrySupport.doGetObjectFromFactoryBean(FactoryBeanRegistrySupport.java:169)
  at org.springframework.beans.factory.support.FactoryBeanRegistrySupport.getObjectFromFactoryBean(FactoryBeanRegistrySupport.java:101)
• locked <0x00000006c0741aa0> (a java.util.concurrent.ConcurrentHashMap)
  at org.springframework.beans.factory.support.AbstractBeanFactory.getObjectForBeanInstance(AbstractBeanFactory.java:1828)
  at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.getObjectForBeanInstance(AbstractAutowireCapableBeanFactory.java:1265)
  at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:261)
  at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202)
  at org.springframework.beans.factory.config.DependencyDescriptor.resolveCandidate(DependencyDescriptor.java:276)
  at org.springframework.beans.factory.support.DefaultListableBeanFactory.addCandidateEntry(DefaultListableBeanFactory.java:1532)
  at org.springframework.beans.factory.support.DefaultListableBeanFactory.findAutowireCandidates(DefaultListableBeanFactory.java:1489)
  at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1270)
  at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1227)
  at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor.autowireResource(CommonAnnotationBeanPostProcessor.java:521)
  at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor.getResource(CommonAnnotationBeanPostProcessor.java:497)
  at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor$ResourceElement.getResourceToInject(CommonAnnotationBeanPostProcessor.java:650)
  at org.springframework.beans.factory.annotation.InjectionMetadata$InjectedElement.inject(InjectionMetadata.java:228)
  at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:119)
  at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor.postProcessProperties(CommonAnnotationBeanPostProcessor.java:318)
  at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1420)
  at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:593)
  at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:516)
  at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:324)
  at org.springframework.beans.factory.support.AbstractBeanFactory$$Lambda$155/1839962989.getObject(Unknown Source)
  at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:234)
• locked <0x00000006c0741aa0> (a java.util.concurrent.ConcurrentHashMap)
  at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:322)
  at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202)
  at org.springframework.beans.factory.config.DependencyDescriptor.resolveCandidate(DependencyDescriptor.java:276)
  at org.springframework.beans.factory.support.DefaultListableBeanFactory.addCandidateEntry(DefaultListableBeanFactory.java:1525)
  at org.springframework.beans.factory.support.DefaultListableBeanFactory.findAutowireCandidates(DefaultListableBeanFactory.java:1489)
  at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveMultipleBeans(DefaultListableBeanFactory.java:1408)
  at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1265)
  at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1227)
  at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor.autowireResource(CommonAnnotationBeanPostProcessor.java:521)
  at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor.getResource(CommonAnnotationBeanPostProcessor.java:497)
  at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor$ResourceElement.getResourceToInject(CommonAnnotationBeanPostProcessor.java:650)
  at org.springframework.beans.factory.annotation.InjectionMetadata$InjectedElement.inject(InjectionMetadata.java:228)
  at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:119)
  at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor.postProcessProperties(CommonAnnotationBeanPostProcessor.java:318)
  at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1420)
  at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:593)
  at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:516)
  at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:324)
  at org.springframework.beans.factory.support.AbstractBeanFactory$$Lambda$155/1839962989.getObject(Unknown Source)
  at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:234)
• locked <0x00000006c0741aa0> (a java.util.concurrent.ConcurrentHashMap)
  at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:322)
  at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:207)
  at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.resolveBeanByName(AbstractAutowireCapableBeanFactory.java:453)
  at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor.autowireResource(CommonAnnotationBeanPostProcessor.java:527)
  at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor.getResource(CommonAnnotationBeanPostProcessor.java:497)
  at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor$ResourceElement.getResourceToInject(CommonAnnotationBeanPostProcessor.java:650)
  at org.springframework.beans.factory.annotation.InjectionMetadata$InjectedElement.inject(InjectionMetadata.java:228)
  at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:119)
  at org.springframework.context.annotation.CommonAnnotationBeanPostProcessor.postProcessProperties(CommonAnnotationBeanPostProcessor.java:318)
  at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1420)
  at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:593)
  at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:516)
  at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:324)
  at org.springframework.beans.factory.support.AbstractBeanFactory$$Lambda$155/1839962989.getObject(Unknown Source)
  at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:234)
• locked <0x00000006c0741aa0> (a java.util.concurrent.ConcurrentHashMap)
  at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:322)
  at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202)
  at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:897)
  at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:879)
  at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:551)
• locked <0x00000006c07b39e0> (a java.lang.Object)
  at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:143)
  at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:758)
  at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:750)
  at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:405)
  at org.springframework.boot.SpringApplication.run(SpringApplication.java:315)
  at org.springframework.boot.SpringApplication.run(SpringApplication.java:1237)
  at org.springframework.boot.SpringApplication.run(SpringApplication.java:1226)
  at com.bc.job.JobExecutorApplication.main(JobExecutorApplication.java:17)

暂时的解决办法：
项目中覆盖DubboMetadataServiceProxy源码，修改createProxyIfAbsent方法
private DubboMetadataService createProxyIfAbsent(String serviceName, String version) {
if (dubboMetadataServiceCache.get(serviceName) == null) {
DubboMetadataService proxy = createProxy(serviceName, version);
dubboMetadataServiceCache.put(serviceName, proxy);
}
return dubboMetadataServiceCache.get(serviceName);
// return dubboMetadataServiceCache.computeIfAbsent(serviceName,
// name -> createProxy(name, version));
}

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