JBoss EAP 6 or 7 starts slowly when one of the mod_cluster proxies is down

Issue

• In EAP 6/7 when using more than one Apache in proxy-list, JBoss starts slowly if at least one Apache is down. From thread dumps, we see start up operations frequently persisting in calls like below:

"ServerService Thread Pool -- 72" #134 prio=5 os_prio=0 tid=0x00007f84581fa9f0 nid=0x6718 runnable [0x00007f83c1561000]
   java.lang.Thread.State: RUNNABLE
        at java.net.SocketInputStream.socketRead0(Native Method)
        at java.net.SocketInputStream.socketRead(SocketInputStream.java:116)
        at java.net.SocketInputStream.read(SocketInputStream.java:171)
        at java.net.SocketInputStream.read(SocketInputStream.java:141)
        at sun.nio.cs.StreamDecoder.readBytes(StreamDecoder.java:284)
        at sun.nio.cs.StreamDecoder.implRead(StreamDecoder.java:326)
        at sun.nio.cs.StreamDecoder.read(StreamDecoder.java:178)
        - locked <0x00000000eb0a4700> (a java.io.InputStreamReader)
        at java.io.InputStreamReader.read(InputStreamReader.java:184)
        at java.io.BufferedReader.fill(BufferedReader.java:161)
        at java.io.BufferedReader.readLine(BufferedReader.java:324)
        - locked <0x00000000eb0a4700> (a java.io.InputStreamReader)
        at java.io.BufferedReader.readLine(BufferedReader.java:389)
        at org.jboss.modcluster.mcmp.impl.DefaultMCMPHandler.sendRequest(DefaultMCMPHandler.java:529)
        at org.jboss.modcluster.mcmp.impl.DefaultMCMPHandler.sendRequest(DefaultMCMPHandler.java:605)
        - locked <0x00000000fcaac598> (a org.jboss.modcluster.mcmp.impl.DefaultMCMPHandler$Proxy)
        at org.jboss.modcluster.mcmp.impl.DefaultMCMPHandler.sendRequest(DefaultMCMPHandler.java:429)
        at org.jboss.modcluster.ModClusterService.enable(ModClusterService.java:375)
        at org.jboss.modcluster.ModClusterService.start(ModClusterService.java:361)
        at org.wildfly.mod_cluster.undertow.UndertowEventHandlerAdapter.onDeploymentStart(UndertowEventHandlerAdapter.java:136)
        - locked <0x00000000fcaac7a8> (a org.wildfly.mod_cluster.undertow.UndertowEventHandlerAdapter)
        at org.wildfly.extension.undertow.Host$1.invoke(Host.java:192)
        at org.wildfly.extension.undertow.UndertowService.fireEvent(UndertowService.java:249)
        - locked <0x00000000fcaa4598> (a java.util.Collections$SynchronizedList)
        at org.wildfly.extension.undertow.Host.registerDeployment(Host.java:189)
        at org.wildfly.extension.undertow.deployment.UndertowDeploymentService.startContext(UndertowDeploymentService.java:103)
        at org.wildfly.extension.undertow.deployment.UndertowDeploymentService$1.run(UndertowDeploymentService.java:82)

• JBoss EAP starts slowly when one Apache is down