约几十个请求过去后，出现Caused by: java.io.IOException: Connection reset by peer异常

Caused by: java.io.IOException: Connection reset by peer

        at java.base/sun.nio.ch.FileDispatcherImpl.write0(Native Method)

        at java.base/sun.nio.ch.SocketDispatcher.write(SocketDispatcher.java:62)

        at java.base/sun.nio.ch.IOUtil.writeFromNativeBuffer(IOUtil.java:132)

        at java.base/sun.nio.ch.IOUtil.write(IOUtil.java:97)

        at java.base/sun.nio.ch.IOUtil.write(IOUtil.java:53)

        at java.base/sun.nio.ch.SocketChannelImpl.write(SocketChannelImpl.java:532)

        at org.apache.tomcat.util.net.NioChannel.write(NioChannel.java:118)

        at org.apache.tomcat.util.net.NioEndpoint$NioSocketWrapper.doWrite(NioEndpoint.java:1381)

        at org.apache.tomcat.util.net.SocketWrapperBase.doWrite(SocketWrapperBase.java:764)

        at org.apache.tomcat.util.net.SocketWrapperBase.writeBlocking(SocketWrapperBase.java:589)

        at org.apache.tomcat.util.net.SocketWrapperBase.write(SocketWrapperBase.java:533)

        at org.apache.coyote.http11.Http11OutputBuffer$SocketOutputBuffer.doWrite(Http11OutputBuffer.java:540)

        at org.apache.coyote.http11.filters.IdentityOutputFilter.doWrite(IdentityOutputFilter.java:84)

        at org.apache.coyote.http11.Http11OutputBuffer.doWrite(Http11OutputBuffer.java:193)

        at org.apache.coyote.Response.doWrite(Response.java:616)

        at org.apache.catalina.connector.OutputBuffer.realWriteBytes(OutputBuffer.java:331)

        ... 87 common frames omitted

排查
根据网络上查询的结果，有以下几种常见情况

服务并发处理处理不过来，会关闭其中的一些连接
防火墙
客户端关闭了连接（未通知服务端四次挥手，例如直接关闭客户端）
经排查不属于以上情况，最后定位到open files设置的值调小了导致的

我使用的Centos7，默认打开文件数为1024个，通过ulimit -a 可以查看open files

[root@localhost docker]# ulimit -a | grep open
open files                      (-n) 1024

解决办法

1.修改ulimit

vim /etc/security/limits.conf
# 在最后追加以下内容
* soft nofile 65536
* hard nofile 65536

或者使用如下命令直接追加至 /etc/security/limits.conf 文件

echo "* soft nofile 65536
* hard nofile 65536 " >> /etc/security/limits.conf

检查是否生效

[root@localhost docker]# ulimit -a | grep open
open files                      (-n) 65536

2.重启后台服务

到此问题解决！