Tomcat优化，配置优化
1.内存优化
JAVA_OPTS="-server -Xms2048M -Xmx2048M -XX:+HeapDumpOnOutOfMemoryError -XX:HeapDumpPath=$CATALINA_HOME/logs/heap.dump"
2.并发优化
${tomcat}/webapps/docs/config/http.html
maxConnections：最大并发连接数，NIO和NIO2默认10000，APR/native模式是8192，The maximum number of connections that the server will accept and process at any given time
acceptCount: 队列最大排队数，默认值是100，The maximum queue length for incoming connection requests when all possible request processing threads are in use.
maxThreads：最大工作线程数，The maximum number of request processing threads to be created by this Connector
minSpareThreads：最小空闲的工作线程。The minimum number of threads always kept running
3.其他优化，
${tomcat}/webapps/docs/config/host.html
autoDeploy：This flag value indicates if Tomcat should check periodically for new or updated web applications while Tomcat is running
${tomcat}/webapps/docs/config/http.html
enableLookups：false
${tomcat}/webapps/docs/config/context.html:
reloadable：默认false，开发阶段可以设置true，负载很重
4. connector：apr
http://apr.apache.org/
依赖：
APR 1.2+ development headers (libapr1-dev package)
OpenSSL 1.0.2+ development headers (libssl-dev package)
JNI headers from Java compatible JDK 1.4+
GNU development environment (gcc, make)
yum install apr* openssl-devel gcc make
tar zxvf apr-1.4.5.tar
cd apr-1.4.5
./configure --prefix=/usr/local/apr
make
make install
tar -zxvf apr-iconv-1.2.1.tar.gz
cd apr-iconv-1.2.1
./configure --prefix=/usr/local/apr-iconv --with-apr=/usr/local/apr
make
make install
yum install expat-devel
tar zxvf apr-util-1.3.12.tar.gz
cd apr-util-1.3.12
./configure --prefix=/usr/local/apr-util --with-apr=/usr/local/apr
make
make install
安装openssl 1.0.2
./config --prefix=/usr/local/openssl
修改Makefile：
vi Makefile
将原来的：CFLAG= -DOPENSSL_THREADS
修改为： CFLAG= -fPIC -DOPENSSL_THREADS
也就是添加-fPIC
执行执行：
make && make install
cd bin
tar -zxvf tomcat-native.tar.gz
cd tomcat-native-1.2.12-src
cd native
./configure --with-apr=/usr/local/apr --with-ssl=/usr/local/openssl
make
make install
catalina.sh：
JAVA_OPTS="$JAVA_OPTS -Djava.library.path=/usr/local/apr/lib
注意：开启了apr之后，jvm用到的native内存会增大，因此要适当调大Metaspace空间,添加JVM选项：-XX:MetaspaceSize=128m
JAVA_OPTS="-server -Xms2048M -Xmx2048M -XX:MetaspaceSize=128M -XX:+HeapDumpOnOutOfMemoryError -XX:HeapDumpPath=$CATALINA_HOME/logs/heap.dump"
server.xml：
<Connector port="8080" protocol="org.apache.coyote.http11.Http11AprProtocol"
connectionTimeout="20000"
redirectPort="8443" />
<Listener className="org.apache.catalina.core.AprLifecycleListener" SSLEngine="off" />
LVS四层负载均衡
LVS + Keepalived高可用
