一、简介
APR(Apache portable Run-time libraries)模式：简单理解，就是从操作系统级别解决异步IO问题，大幅度的提高服务器的处理和响应性能， 也是Tomcat运行高并发应用的首选模式。
二、启用apr模式步聚
1、安装系统必要库和工具
yum install apr-devel
yum install openssl-devel
yum install gcc
yum install make
openssl库要求在0.9.7以上版本，APR要求在1.2以上版本
2、安装apr动态库
进入tomcat的bin目录，解压tomcat-native.tar.gz文件，并进入tomcat-native-1.2.7-src/native目录，执行./configure && make && make install 命令，动态库默认安装在/usr/local/apr/lib目录下
3、配置APR本地库到系统共享库搜索路径中
编辑$TOMCAT_HOME/bin/catalina.sh文件，在虚拟机启动参数JAVA_OPTS中添加java.library.path参数，指定apr库的路径
JAVA_OPTS="$JAVA_OPTS -Djava.library.path=/usr/local/apr/lib"
修改 server.xml 中的协议为 APR Protocol
<Connector port="8080" protocol="org.apache.coyote.http11.Http11AprProtocol"
connectionTimeout="20000"
redirectPort="8443" />
如果不想启用SSL，将server.xml中apr模式下ssl关闭即可:
<Listener className="org.apache.catalina.core.AprLifecycleListener" SSLEngine="off" />
重启Tomcat, 日志显示
Aug 29, 2010 3:47:32 PM org.apache.catalina.core.AprLifecycleListener init
INFO: Loaded APR based Apache Tomcat Native library 1.1.20.
在最后的端口信息方面也可以看到http-apr-8080
⚠注意
Tomcat 7.x版本从7.0.30开始就支持APR, 之后版本的都可以使用APR模式
三、Linux Optimization
由于我们采用了linux服务器，所以优化内核参数也是一个非常重要的工作。以下为优化参考:
修改/etc/sysctl.cnf文件，在最后追加如下内容：
net.core.netdev_max_backlog = 32768
net.core.somaxconn = 32768
net.core.wmem_default = 8388608
net.core.rmem_default = 8388608
net.core.rmem_max = 16777216
net.core.wmem_max = 16777216
net.ipv4.ip_local_port_range = 1024 65000
net.ipv4.route.gc_timeout = 100
net.ipv4.tcp_fin_timeout = 30
net.ipv4.tcp_keepalive_time = 1200
net.ipv4.tcp_timestamps = 0
net.ipv4.tcp_synack_retries = 2
net.ipv4.tcp_syn_retries = 2
net.ipv4.tcp_tw_recycle = 1
net.ipv4.tcp_tw_reuse = 1
net.ipv4.tcp_mem = 94500000 915000000 927000000
net.ipv4.tcp_max_orphans = 3276800
net.ipv4.tcp_max_syn_backlog = 65536
保存退出，执行sysctl -p生效
四、配置模式
APR
<Connector executor="tomcatThreadPool" port="8080" protocol="org.apache.coyote.http11.Http11AprProtocol"
connectionTimeout="20000"
redirectPort="8443"
enableLookups="false"
maxPostSize="10485760"
URIEncoding="UTF-8"
acceptCount="600"
acceptorThreadCount="48"
disableUploadTimeout="true"
maxConnections="800"
SSLEnabled="false"/>
<Executor name="tomcatThreadPool" namePrefix="catalina-exec-"
maxThreads="600" maxIdleTime="20000" minSpareThreads="400" prestartminSpareThreads="true" />
AJP
<Connector port="8009" protocol="AJP/1.3" maxThreads="1000" minSpareThreads="100" maxSpareThreads="500"
acceptCount="700" connectionTimeout="20000" redirectPort="8443" />
2017-01-06 对原先基线和配置修改
机器配置为
CPU: Intel(R) Xeon(R) CPU E5-2630 v2 @ 2.6GHz 24core
内存: 128G
JDK Ver: 1.7.0_80
Tomcat Ver: 8.5.6
⚠注意 使用Tomcat8时会出现如下Warning
警告 [localhost-startStop-1] org.apache.catalina.webresources.Cache.getResource Unable to add the resource at [/WEB-INF/classes/] to the cache because there was insufficient free space available after evicting expired cache entries - consider increasing the maximum size of the cache
解决办法在conf/conext.xml中加入如下配置
<Context>
<WatchedResource>WEB-INF/web.xml</WatchedResource>
<WatchedResource>${catalina.base}/conf/web.xml</WatchedResource>
<Resources cachingAllowed="true" cacheMaxSize="100000" />
</Context>
在更换Tomcat之后首次调整ThreadPool采用NIO Pattern
<Connector executor="tomcatThreadPool" port="8080" protocol="org.apache.coyote.http11.Http11NioProtocol"
connectionTimeout="20000"
redirectPort="8443"
enableLookups="false"
maxPostSize="10485760"
URIEncoding="UTF-8"
acceptCount="600"
acceptorThreadCount="48"
disableUploadTimeout="true"
maxConnections="800"
SSLEnabled="false"/>
<Executor name="tomcatThreadPool" namePrefix="catalina-exec-"
maxThreads="600" maxIdleTime="20000" minSpareThreads="400" prestartminSpareThreads="true" />
acceptorThreadCount 数量为CPU Core的2倍
OSP Client Interface Conf Param: CentOS5.8、Timeout 20ms
验测线程50并发
验测线程200并发
Redis Response Interface Conf Param: CentOS5.8、Connection Redis
验测线程50并发
验测线程200并发
2017-01-10 切换服务器版本为CentOS6.6、Tomcat版本和ThreadPool配置参数不变，重新压测数据如下
OSP Client Interface Conf Param: CentOS6.6、Timeout 20ms
验测线程50并发
验测线程200并发
Redis Response Interface Conf Param: CentOS6.6、Connection Redis
验测线程50并发
验测线程200并发
此次调整操作系统版本6.6之后同比之前5.8版本中的压测结果均有30%左右的提升，但调用USP的OSP接口环比原生链接Redis的接口的QPS相差还在45%以上，前者低于后者。
2017-01-12
%TOMCAT_HOME%/bin/catalina.sh添加JVM参数
JAVA_OPTS="-server
-Xms4096m
-Xmx4096m
-Xmn2048m
-XX:MaxDirectMemorySize=4096m
-XX:PermSize=256m
-XX:MaxPermSize=512m
-XX:ReservedCodeCacheSize=240M
-XX:+UseCodeCacheFlushing"
OSP Client Interface
验测线程200并发
Redis Response Interface
验测线程200并发
两个接口QPS均有10%的提升，但环比差距仍为50%，原生访问Redis的接口好于访问OSP的接口