NIO EventPoller thread dies from uncaught NPE, leading to unresponsiveness

Issue

• We use an NIO connector and it became unresponsive. The acceptor thread was refusing connections with errors like the following:

INFO [org.apache.tomcat.util] (http-/0:0:0:0:0:0:0:0:38092-Acceptor) JBWEB003022: Channel processing failed

• There were limited sockets established, but still in a heap dump, it looks like the NioEndpoint has exhausted connections:

    NioEndpoint.maxConnection = 32768
    NioEndpoint.counter = 32768
    NioEndpoint.connections hold 32768 instances of NioChannel

• A thread dump also shows the EventPoller thread for this connector is missing