压力测试场景，前端nginx反向代理到4个tomcat实例，在其中的一个实例上产生了大量的countDownConnection Incorrect connection count警告
WARNING [http-nio-8080-exec-48] org.apache.tomcat.util.net.AbstractEndpoint.countDownConnection Incorrect connection count, multiple socket.close called on the same socket.另外一个异常是4个tomcat实例上都看到的NPE异常：
Exception in thread "http-nio-8080-AsyncTimeout" java.lang.NullPointerException
at org.apache.coyote.AbstractProcessor.doTimeoutAsync(AbstractProcessor.java:528)
at org.apache.coyote.AbstractProcessor.timeoutAsync(AbstractProcessor.java:518)
at org.apache.coyote.AbstractProtocol$AsyncTimeout.run(AbstractProtocol.java:1130)
at java.lang.Thread.run(Thread.java:745)使用了servlet3.0，connector配置如下：
<Connector port="8080" protocol="org.apache.coyote.http11.Http11NioProtocol"
connectionTimeout="20000" redirectPort="8443" maxParameterCount="2000" maxKeepAliveRequests="-1"
maxThreads="200" maxPostSize="20971520" acceptCount="1024" useBodyEncodingForURI="true"
URIEncoding="UTF-8"/>已将bug提交到了bugzilla，在这里记录一下，后续跟踪。