Operation ("read-attribute") failed

[draven1]

Server hung and in server.log just wrote this:

How understand why it hung? How to fix without reboot server?

ERROR [org.jboss.as.controller.management-operation] (External Management Request Threads -- 5) WFLYCTL0013: Operation ("read-attribute") failed - address: ([

    ("deployment" => "deploy"),

    ("subsystem" => "undertow")

]): java.lang.NullPointerException

        at org.wildfly.extension.undertow.DeploymentDefinition$SessionManagerStatsHandler.executeRuntimeStep(DeploymentDefinition.java:101)

        at org.jboss.as.controller.AbstractRuntimeOnlyHandler$1.execute(AbstractRuntimeOnlyHandler.java:53)

        at org.jboss.as.controller.AbstractOperationContext.executeStep(AbstractOperationContext.java:890)

        at org.jboss.as.controller.AbstractOperationContext.processStages(AbstractOperationContext.java:659)

        at org.jboss.as.controller.AbstractOperationContext.executeOperation(AbstractOperationContext.java:370)

        at org.jboss.as.controller.OperationContextImpl.executeOperation(OperationContextImpl.java:1329)

        at org.jboss.as.controller.ModelControllerImpl.internalExecute(ModelControllerImpl.java:400)

        at org.jboss.as.controller.ModelControllerImpl.execute(ModelControllerImpl.java:222)

        at org.jboss.as.domain.http.server.DomainApiHandler.handleRequest(DomainApiHandler.java:219)

        at io.undertow.server.handlers.encoding.EncodingHandler.handleRequest(EncodingHandler.java:72)

        at org.jboss.as.domain.http.server.security.SubjectDoAsHandler$1.run(SubjectDoAsHandler.java:72)

        at org.jboss.as.domain.http.server.security.SubjectDoAsHandler$1.run(SubjectDoAsHandler.java:68)

        at java.security.AccessController.doPrivileged(Native Method)

        at javax.security.auth.Subject.doAs(Subject.java:422)

        at org.jboss.as.controller.AccessAuditContext.doAs(AccessAuditContext.java:149)

        at org.jboss.as.domain.http.server.security.SubjectDoAsHandler.handleRequest(SubjectDoAsHandler.java:68)

        at org.jboss.as.domain.http.server.security.SubjectDoAsHandler.handleRequest(SubjectDoAsHandler.java:63)

        at io.undertow.server.handlers.BlockingHandler.handleRequest(BlockingHandler.java:56)

        at org.jboss.as.domain.http.server.DomainApiCheckHandler.handleRequest(DomainApiCheckHandler.java:95)

        at io.undertow.server.Connectors.executeRootHandler(Connectors.java:202)

        at io.undertow.server.HttpServerExchange$1.run(HttpServerExchange.java:805)

        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)

        at org.jboss.threads.JBossThread.run(JBossThread.java:320)

[rhusar]

This is not indicative of a server hang.

It looks like server was queried for statistics but the services were not yet up or were already down. Which version of WF is this?

[rhusar]

The NPE has been fixed long time ago: [WFLY-7120] NPE in SessionManagerStatsHandler - JBoss Issue Tracker

[draven1]

We use 10.1.0 Final

I wrote server hung because it's not worked correct, deployment tab not display any application.