说明： 双主机用memcached做的Session，第一台不报错，第二台有时小量报错有时一报一大批，服务访问显示"服务异常"； 网上找了很多方法(改字符编码，调整tomcat头部大小限制)都不起作用，重启后当时没问题，大概几个小时后又会报同样的错误。
Tomcat环境：
Server version: Apache Tomcat/8.0.32 Server built: Feb 2 2016 19:34:53 UTC Server number: 8.0.32.0 OS Name: Linux OS Version: 3.10.0-514.26.2.el7.x86_64 Architecture: amd64 JVM Version: 1.8.0_74-b02 JVM Vendor: Oracle Corporation配置文件：
<Connector port="8083" protocol="HTTP/1.1" connectionTimeout="20000" maxHttpHeaderSize="14194304" maxPostSize="4194304" redirectPort="8443" URIEncoding='UTF-8' />报错内容：
29-Oct-2018 11:15:02.777 SEVERE [bxgdisthread-getAfficheList-8eb5aaa0f1a0417da9d4ad6e836eeb68] org.apache.coyote.http11.AbstractHttp11Processor.process Error processing request java.lang.NullPointerException at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:571) at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1095) at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:672) at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1500) at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1456) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) at java.lang.Thread.run(Thread.java:745) 29-Oct-2018 11:15:02.777 SEVERE [bxgdisthread-getAfficheList-8eb5aaa0f1a0417da9d4ad6e836eeb68] org.apache.coyote.http11.AbstractHttp11Processor.endRequest Error finishing response java.lang.NullPointerException 29-Oct-2018 11:15:14.741 SEVERE [bxgdisthread-findNotArchiveSquadsWithStuCnt-a682fbc87ef348b494dc7a3319366fd0] org.apache.coyote.http11.AbstractHttp11Processor.endRequest Error finishing response java.lang.NullPointerException 29-Oct-2018 11:15:14.792 SEVERE [bxgdisthread-findExamsByCreatePerson-abc002f7505f44bf94984ef258349440] org.apache.coyote.http11.AbstractHttp11Processor.endRequest Error finishing response java.lang.NullPointerException 29-Oct-2018 11:15:30.678 SEVERE [bxgdisthread-findByUserId-4187f396dc274c449a793935c02f921b] org.apache.coyote.http11.AbstractHttp11Processor.process Error processing request java.lang.NullPointerException at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:571) at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1095) at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:672) at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1500) at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1456) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) at java.lang.Thread.run(Thread.java:745) 29-Oct-2018 11:15:30.678 SEVERE [bxgdisthread-findByUserId-4187f396dc274c449a793935c02f921b] org.apache.coyote.http11.AbstractHttp11Processor.endRequest Error finishing response java.lang.NullPointerException 29-Oct-2018 11:15:34.982 SEVERE [bxgdisthread-menuRedPoint-7d3d616f3546443390a91ec2cdff0c9e] org.apache.coyote.http11.AbstractHttp11Processor.process Error processing request java.lang.NullPointerException 29-Oct-2018 11:15:34.982 SEVERE [bxgdisthread-menuRedPoint-7d3d616f3546443390a91ec2cdff0c9e] org.apache.coyote.http11.AbstractHttp11Processor.endRequest Error finishing response java.lang.NullPointerException 29-Oct-2018 11:15:51.891 SEVERE [bxgdisthread-menuRedPoint-99da36b292a54380a40409c3b8a181c3] org.apache.coyote.http11.AbstractHttp11Processor.process Error processing request