vCenter plugin not loading after fresh install of vCSA 6.5 U1e

[craigc123]

We deployed a fresh VCSA (6.5 U1e) and registered our Flex plugin. It was not accessible from vSphere Web Client until we restarted the vsphere-client service. Rebooting the VCSA will also cause the plugin to load. We don't experience this problem on earlier VCSA versions. Has anyone else ran in to this kind of issue before? Is the correct procedure to reboot vCenter (or restart some services) after deploying a 3rd party plugin?

Here is the NoClassDefFoundError that seems to be preventing our plugin from loading:

[2018-03-01T21:37:55.365Z] [INFO ] start-signalling-3 o.a.c.c.C.[.[localhost].[/vsphere-client/vstacplugin-ui] No Spring WebApplicationInitializer types detected on classpath
[2018-03-01T21:37:55.368Z] [ERROR] start-signalling-3 o.a.c.c.C.[.[localhost].[/vsphere-client/vstacplugin-ui] Error configuring application listener of class flex.messaging.HttpFlexSession java.lang.NoClassDefFoundError: flex/messaging/FlexSessionAttributeListener
at java.lang.Class.getDeclaredMethods0(Native Method)
at java.lang.Class.privateGetDeclaredMethods(Class.java:2701)
at java.lang.Class.getDeclaredMethods(Class.java:1975)
at org.apache.catalina.util.Introspection.getDeclaredMethods(Introspection.java:127)
at org.apache.catalina.core.DefaultInstanceManager.populateAnnotationsCache(DefaultInstanceManager.java:309)
at org.apache.catalina.core.DefaultInstanceManager.newInstance(DefaultInstanceManager.java:132)
at org.apache.catalina.core.DefaultInstanceManager.newInstance(DefaultInstanceManager.java:114)
at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:5026)
at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5633)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:145)
at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:1015)
at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:991)
at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:652)
at org.eclipse.gemini.web.tomcat.internal.TomcatServletContainer.startWebApplication(TomcatServletContainer.java:125)
at org.eclipse.gemini.web.internal.StandardWebApplication.start(StandardWebApplication.java:109)
at org.eclipse.virgo.web.core.internal.WebBundleLifecycleListener.onStarted(WebBundleLifecycleListener.java:122)
at org.eclipse.virgo.kernel.install.artifact.internal.StandardArtifactStateMonitor.onStarted(StandardArtifactStateMonitor.java:271)
at org.eclipse.virgo.kernel.install.artifact.internal.AbstractInstallArtifact.asyncStartSucceeded(AbstractInstallArtifact.java:319)
at org.eclipse.virgo.kernel.install.artifact.internal.AbstractInstallArtifact.access$0(AbstractInstallArtifact.java:316)
at org.eclipse.virgo.kernel.install.artifact.internal.AbstractInstallArtifact$StateMonitorSignal.signalSuccessfulCompletion(AbstractInstallArtifact.java:252)
at org.eclipse.virgo.nano.core.internal.BundleStartTracker$1.run(BundleStartTracker.java:140)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)
Caused by: org.eclipse.virgo.kernel.osgi.framework.ExtendedClassNotFoundException: flex.messaging.FlexSessionAttributeListener in KernelBundleClassLoader: [bundle=org.apache.flex.blazeds.core_4.7.3]
at org.eclipse.virgo.kernel.userregion.internal.equinox.KernelBundleClassLoader.loadClass(KernelBundleClassLoader.java:150)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
... 24 common frames omitted
Caused by: java.lang.ClassNotFoundException: flex.messaging.FlexSessionAttributeListener
at org.eclipse.osgi.internal.loader.BundleLoader.findClassInternal(BundleLoader.java:501)
at org.eclipse.osgi.internal.loader.BundleLoader.findClass(BundleLoader.java:421)
at org.eclipse.osgi.internal.loader.BundleLoader.findClass(BundleLoader.java:412)
at org.eclipse.osgi.internal.baseadaptor.DefaultClassLoader.loadClass(DefaultClassLoader.java:107)
at org.eclipse.virgo.kernel.userregion.internal.equinox.KernelBundleClassLoader.loadClass(KernelBundleClassLoader.java:146)
... 25 common frames omitted

After restarting the vsphere-client service we don't see any errors and the plugin loads successfully:

[2018-03-02T18:11:22.870Z] [INFO ] start-signalling-3 o.a.c.c.C.[.[localhost].[/vsphere-client/vstacplugin-ui] No Spring WebApplicationInitializer types detected on classpath
[2018-03-02T18:11:22.885Z] [INFO ] start-signalling-3 o.a.c.c.C.[.[localhost].[/vsphere-client/vstacplugin-ui] Initializing Spring FrameworkServlet 'springServlet'
[2018-03-02T18:11:22.885Z] [INFO ] start-signalling-3 org.springframework.web.servlet.DispatcherServlet FrameworkServlet 'springServlet': initialization started
[2018-03-02T18:11:22.886Z] [INFO ] start-signalling-3 o.eclipse.virgo.web.dm.ServerOsgiBundleXmlWebApplicationContext Refreshing ServerOsgiBundleXmlWebApplicationContext for namespace 'springServlet-servlet': startup date [Fri Mar 02 18:11:22 UTC 2018]; root of context hierarchy
[2018-03-02T18:11:22.886Z] [INFO ] start-signalling-3 o.eclipse.virgo.web.dm.ServerOsgiBundleXmlWebApplicationContext Application Context service already unpublished
[2018-03-02T18:11:22.886Z] [INFO ] start-signalling-3 org.springframework.beans.factory.xml.XmlBeanDefinitionReader Loading XML bean definitions from ServletContext resource [/WEB-INF/spring/bundle-context.xml]
[2018-03-02T18:11:22.898Z] [INFO ] start-signalling-3 o.e.virgo.kernel.dmfragment.internal.LoadTimeWeaverPostProcessor Load-time weaving not enabled for bundle 'com.pivot3.vstacpluginui.Vstacpluginui_1.0.0 [371]',
[2018-03-02T18:11:22.898Z] [INFO ] start-signalling-3 o.e.virgo.kernel.dmfragment.internal.MBeanExporterPostProcessor MBean exporting not enabled for bundle 'com.pivot3.vstacpluginui.Vstacpluginui_1.0.0 [371]',
[2018-03-02T18:11:22.924Z] [INFO ] start-signalling-3 o.s.beans.factory.support.DefaultListableBeanFactory Pre-instantiating singletons in org.springframework.beans.factory.support.DefaultListableBeanFactory@76a07494: defining beans _messageBrokerHandlerAdapter,vstacplugin-ui-brokerDefaultHandlerMapping,_jsonConfigMapEditorConfigur...; root of factory hierarchy
[2018-03-02T18:11:22.942Z] [INFO ] start-signalling-3 org.springframework.flex.config.FlexConfigurationManager Loading Flex services configuration from: ServletContext resource [/WEB-INF/flex/services-config.xml]
[2018-03-02T18:11:22.951Z] [INFO ] start-signalling-3 org.springframework.flex.config.FlexConfigurationManager Including Flex services configuration from: ServletContext resource [/WEB-INF/flex/messaging-config.xml]
[2018-03-02T18:11:22.955Z] [INFO ] start-signalling-3 org.springframework.flex.config.FlexConfigurationManager Including Flex services configuration from: ServletContext resource [/WEB-INF/flex/remoting-config.xml]
[2018-03-02T18:11:22.969Z] [INFO ] start-signalling-3 org.springframework.flex.core.MessageBrokerFactoryBean flex-messaging-core: 4.7.3