Continuum startup hangs if enabled build agent is not available

This is particularly a problem when using the same container for both continuum and a build agent.

Here's a thread dump of the hang:

"main" prio=10 tid=0x09593800 nid=0x47c6 runnable [0x73693000]
java.lang.Thread.State: RUNNABLE
at java.net.SocketInputStream.socketRead0(Native Method)
at java.net.SocketInputStream.read(SocketInputStream.java:129)
at java.io.BufferedInputStream.fill(BufferedInputStream.java:218)
at java.io.BufferedInputStream.read1(BufferedInputStream.java:258)
at java.io.BufferedInputStream.read(BufferedInputStream.java:317)

• locked <0x7504da58> (a java.io.BufferedInputStream)
  at sun.net.www.http.HttpClient.parseHTTPHeader(HttpClient.java:687)
  at sun.net.www.http.HttpClient.parseHTTP(HttpClient.java:632)
  at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1072)
• locked <0x74ffab50> (a sun.net.www.protocol.http.HttpURLConnection)
  at org.apache.xmlrpc.client.XmlRpcSunHttpTransport.getInputStream(XmlRpcSunHttpTransport.java:63)
  at org.apache.xmlrpc.client.XmlRpcStreamTransport.sendRequest(XmlRpcStreamTransport.java:141)
  at org.apache.xmlrpc.client.XmlRpcHttpTransport.sendRequest(XmlRpcHttpTransport.java:94)
  at org.apache.xmlrpc.client.XmlRpcSunHttpTransport.sendRequest(XmlRpcSunHttpTransport.java:44)
  at org.apache.xmlrpc.client.XmlRpcClientWorker.execute(XmlRpcClientWorker.java:53)
  at org.apache.xmlrpc.client.XmlRpcClient.execute(XmlRpcClient.java:166)
  at org.apache.xmlrpc.client.XmlRpcClient.execute(XmlRpcClient.java:157)
  at org.apache.xmlrpc.client.XmlRpcClient.execute(XmlRpcClient.java:146)
  at com.atlassian.xmlrpc.RPCCallMethodInterceptor.invoke(RPCCallMethodInterceptor.java:62)
  at $Proxy284.ping(Unknown Source)
  at org.apache.continuum.distributed.transport.slave.SlaveBuildAgentTransportClient.ping(SlaveBuildAgentTransportClient.java:154)
  at org.apache.continuum.builder.distributed.manager.DefaultDistributedBuildManager.initialize(DefaultDistributedBuildManager.java:134)
• locked <0x74988788> (a java.util.Collections$SynchronizedMap)
  at org.codehaus.plexus.spring.PlexusLifecycleBeanPostProcessor.postProcessAfterInitialization(PlexusLifecycleBeanPostProcessor.java:217)
  at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyBeanPostProcessorsAfterInitialization(AbstractAutowireCapableBeanFactory.java:404)
  at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.postProcessObjectFromFactoryBean(AbstractAutowireCapableBeanFactory.java:1544)
  at org.springframework.beans.factory.support.FactoryBeanRegistrySupport.doGetObjectFromFactoryBean(FactoryBeanRegistrySupport.java:163)
  at org.springframework.beans.factory.support.FactoryBeanRegistrySupport.getObjectFromFactoryBean(FactoryBeanRegistrySupport.java:102)
• locked <0x846e11d0> (a java.util.concurrent.ConcurrentHashMap)
  at org.springframework.beans.factory.support.AbstractBeanFactory.getObjectForBeanInstance(AbstractBeanFactory.java:1387)
  at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:244)
  at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:189)
  at org.codehaus.plexus.spring.PlexusComponentFactoryBean.resolveRequirement(PlexusComponentFactoryBean.java:246)
  at org.codehaus.plexus.spring.PlexusComponentFactoryBean.createInstance(PlexusComponentFactoryBean.java:163)
  at org.codehaus.plexus.spring.PlexusComponentFactoryBean.getObject(PlexusComponentFactoryBean.java:108)
• locked <0x8550aac8> (a org.codehaus.plexus.spring.PlexusComponentFactoryBean)
  at org.springframework.beans.factory.support.FactoryBeanRegistrySupport.doGetObjectFromFactoryBean(FactoryBeanRegistrySupport.java:143)
  at org.springframework.beans.factory.support.FactoryBeanRegistrySupport.getObjectFromFactoryBean(FactoryBeanRegistrySupport.java:102)
• locked <0x846e11d0> (a java.util.concurrent.ConcurrentHashMap)
  at org.springframework.beans.factory.support.AbstractBeanFactory.getObjectForBeanInstance(AbstractBeanFactory.java:1387)
  at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:244)
  at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:189)
  at org.codehaus.plexus.spring.PlexusComponentFactoryBean.createInstance(PlexusComponentFactoryBean.java:141)
  at org.codehaus.plexus.spring.PlexusComponentFactoryBean.getObject(PlexusComponentFactoryBean.java:108)
• locked <0x85404db0> (a org.codehaus.plexus.spring.PlexusComponentFactoryBean)
  at org.springframework.beans.factory.support.FactoryBeanRegistrySupport.doGetObjectFromFactoryBean(FactoryBeanRegistrySupport.java:143)
  at org.springframework.beans.factory.support.FactoryBeanRegistrySupport.getObjectFromFactoryBean(FactoryBeanRegistrySupport.java:102)
• locked <0x846e11d0> (a java.util.concurrent.ConcurrentHashMap)
  at org.springframework.beans.factory.support.AbstractBeanFactory.getObjectForBeanInstance(AbstractBeanFactory.java:1387)
  at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:244)
  at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:193)
  at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBeansOfType(DefaultListableBeanFactory.java:386)
  at org.springframework.beans.factory.support.DefaultListableBeanFactory.getBeansOfType(DefaultListableBeanFactory.java:376)
  at org.springframework.context.support.AbstractApplicationContext.getBeansOfType(AbstractApplicationContext.java:1109)
  at org.springframework.beans.factory.BeanFactoryUtils.beansOfTypeIncludingAncestors(BeanFactoryUtils.java:221)
  at org.apache.maven.continuum.notification.manager.spring.NotifierFactoryBean.getObject(NotifierFactoryBean.java:51)
  at org.springframework.beans.factory.support.FactoryBeanRegistrySupport.doGetObjectFromFactoryBean(FactoryBeanRegistrySupport.java:143)
  at org.springframework.beans.factory.support.FactoryBeanRegistrySupport.getObjectFromFactoryBean(FactoryBeanRegistrySupport.java:109)
  at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveInnerBean(BeanDefinitionValueResolver.java:274)
  at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveValueIfNecessary(BeanDefinitionValueResolver.java:120)
  at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyPropertyValues(AbstractAutowireCapableBeanFactory.java:1308)
  at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1067)
  at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:511)
  at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:450)
  at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:290)
  at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222)
• locked <0x846e11d0> (a java.util.concurrent.ConcurrentHashMap)
  at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:287)
  at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:189)
  at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:562)
• locked <0x846e14d8> (a java.util.concurrent.ConcurrentHashMap)
  at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:871)
  at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:423)
• locked <0x846882e8> (a java.lang.Object)
  at org.springframework.web.context.ContextLoader.createWebApplicationContext(ContextLoader.java:272)
  at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:196)
  at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:47)
  at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:3910)
  at org.apache.catalina.core.StandardContext.start(StandardContext.java:4393)
• locked <0x84688340> (a org.apache.catalina.core.StandardContext)
  at org.jboss.web.tomcat.service.deployers.TomcatDeployment.performDeployInternal(TomcatDeployment.java:310)
  at org.jboss.web.tomcat.service.deployers.TomcatDeployment.performDeploy(TomcatDeployment.java:142)
  at org.jboss.web.deployers.AbstractWarDeployment.start(AbstractWarDeployment.java:461)
• locked <0x84688570> (a org.jboss.web.tomcat.service.deployers.TomcatDeployment)
  at org.jboss.web.deployers.WebModule.startModule(WebModule.java:118)
• locked <0x84688088> (a org.jboss.web.deployers.WebModule)
  at org.jboss.web.deployers.WebModule.start(WebModule.java:97)
  at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
  at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
  at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
  at java.lang.reflect.Method.invoke(Method.java:597)
  at org.jboss.mx.interceptor.ReflectedDispatcher.invoke(ReflectedDispatcher.java:157)
  at org.jboss.mx.server.Invocation.dispatch(Invocation.java:96)
  at org.jboss.mx.server.Invocation.invoke(Invocation.java:88)
  at org.jboss.mx.server.AbstractMBeanInvoker.invoke(AbstractMBeanInvoker.java:264)
  at org.jboss.mx.server.MBeanServerImpl.invoke(MBeanServerImpl.java:668)
  at org.jboss.system.microcontainer.ServiceProxy.invoke(ServiceProxy.java:206)
  at $Proxy38.start(Unknown Source)
  at org.jboss.system.microcontainer.StartStopLifecycleAction.installAction(StartStopLifecycleAction.java:42)
  at org.jboss.system.microcontainer.StartStopLifecycleAction.installAction(StartStopLifecycleAction.java:37)
  at org.jboss.dependency.plugins.action.SimpleControllerContextAction.simpleInstallAction(SimpleControllerContextAction.java:62)
  at org.jboss.dependency.plugins.action.AccessControllerContextAction.install(AccessControllerContextAction.java:71)
  at org.jboss.dependency.plugins.AbstractControllerContextActions.install(AbstractControllerContextActions.java:51)
  at org.jboss.dependency.plugins.AbstractControllerContext.install(AbstractControllerContext.java:348)
  at org.jboss.system.microcontainer.ServiceControllerContext.install(ServiceControllerContext.java:286)
  at org.jboss.dependency.plugins.AbstractController.install(AbstractController.java:1631)
  at org.jboss.dependency.plugins.AbstractController.incrementState(AbstractController.java:934)
  at org.jboss.dependency.plugins.AbstractController.resolveContexts(AbstractController.java:1082)
  at org.jboss.dependency.plugins.AbstractController.resolveContexts(AbstractController.java:984)
  at org.jboss.dependency.plugins.AbstractController.change(AbstractController.java:822)
  at org.jboss.dependency.plugins.AbstractController.change(AbstractController.java:553)
  at org.jboss.system.ServiceController.doChange(ServiceController.java:688)
  at org.jboss.system.ServiceController.start(ServiceController.java:460)
  at org.jboss.system.deployers.ServiceDeployer.start(ServiceDeployer.java:163)
  at org.jboss.system.deployers.ServiceDeployer.deploy(ServiceDeployer.java:99)
  at org.jboss.system.deployers.ServiceDeployer.deploy(ServiceDeployer.java:46)
  at org.jboss.deployers.spi.deployer.helpers.AbstractSimpleRealDeployer.internalDeploy(AbstractSimpleRealDeployer.java:62)
  at org.jboss.deployers.spi.deployer.helpers.AbstractRealDeployer.deploy(AbstractRealDeployer.java:50)
  at org.jboss.deployers.plugins.deployers.DeployerWrapper.deploy(DeployerWrapper.java:171)
  at org.jboss.deployers.plugins.deployers.DeployersImpl.doDeploy(DeployersImpl.java:1439)
  at org.jboss.deployers.plugins.deployers.DeployersImpl.doInstallParentFirst(DeployersImpl.java:1157)
  at org.jboss.deployers.plugins.deployers.DeployersImpl.doInstallParentFirst(DeployersImpl.java:1178)
  at org.jboss.deployers.plugins.deployers.DeployersImpl.install(DeployersImpl.java:1098)
  at org.jboss.dependency.plugins.AbstractControllerContext.install(AbstractControllerContext.java:348)
  at org.jboss.dependency.plugins.AbstractController.install(AbstractController.java:1631)
  at org.jboss.dependency.plugins.AbstractController.incrementState(AbstractController.java:934)
  at org.jboss.dependency.plugins.AbstractController.resolveContexts(AbstractController.java:1082)
  at org.jboss.dependency.plugins.AbstractController.resolveContexts(AbstractController.java:984)
  at org.jboss.dependency.plugins.AbstractController.change(AbstractController.java:822)
  at org.jboss.dependency.plugins.AbstractController.change(AbstractController.java:553)
  at org.jboss.deployers.plugins.deployers.DeployersImpl.process(DeployersImpl.java:781)
  at org.jboss.deployers.plugins.main.MainDeployerImpl.process(MainDeployerImpl.java:702)
  at org.jboss.system.server.profileservice.repository.MainDeployerAdapter.process(MainDeployerAdapter.java:117)
  at org.jboss.system.server.profileservice.repository.ProfileDeployAction.install(ProfileDeployAction.java:70)
  at org.jboss.system.server.profileservice.repository.AbstractProfileAction.install(AbstractProfileAction.java:53)
  at org.jboss.system.server.profileservice.repository.AbstractProfileService.install(AbstractProfileService.java:361)
  at org.jboss.dependency.plugins.AbstractControllerContext.install(AbstractControllerContext.java:348)
  at org.jboss.dependency.plugins.AbstractController.install(AbstractController.java:1631)
  at org.jboss.dependency.plugins.AbstractController.incrementState(AbstractController.java:934)
  at org.jboss.dependency.plugins.AbstractController.resolveContexts(AbstractController.java:1082)
  at org.jboss.dependency.plugins.AbstractController.resolveContexts(AbstractController.java:984)
  at org.jboss.dependency.plugins.AbstractController.change(AbstractController.java:822)
  at org.jboss.dependency.plugins.AbstractController.change(AbstractController.java:553)
  at org.jboss.system.server.profileservice.repository.AbstractProfileService.activateProfile(AbstractProfileService.java:306)
  at org.jboss.system.server.profileservice.ProfileServiceBootstrap.start(ProfileServiceBootstrap.java:271)
  at org.jboss.bootstrap.AbstractServerImpl.start(AbstractServerImpl.java:461)
  at org.jboss.Main.boot(Main.java:221)
  at org.jboss.Main$1.run(Main.java:556)
  at java.lang.Thread.run(Thread.java:619)