Master Tomcat: From Installation to Multi‑Instance Deployment

Tomcat Overview

Tomcat concept

Tomcat role

Installation and deployment steps

Directory structure

Example: deploying zrlog

Multi‑instance deployment

Pre‑knowledge

Tomcat Concept

Tomcat is an open‑source, lightweight application server written in Java, part of the Apache Software Foundation. It implements Java Servlet, JSP, and EL specifications, enabling dynamic web applications on the Java platform.

Tomcat Role

Tomcat serves as a Java Servlet container, providing:

Support for Servlet and JSP, allowing developers to create dynamic web pages and handle user requests.

Web application deployment via WAR files placed in the webapps directory.

HTTP/HTTPS services, static resource serving, and integration with IDEs for development and debugging.

Installation and Deployment

Environment Information

IP

Hostname

Linux System

Specs

10.0.0.21

tomcat

Ubuntu22.04

2c4g

Before installing Tomcat, install JDK 8 (or OpenJDK 8) because Tomcat runs on Java.

mkdir -p /app/tools && cd /app/tools
wget https://download.java.net/openjdk/jdk8u44/ri/openjdk-8u44-linux-x64.tar.gz
tar -xf openjdk-8u44-linux-x64.tar.gz
ln -s /app/tools/java-se-8u44-ri/ /app/tools/jdk
cat >> /etc/profile <<EOF
export JAVA_HOME=/app/tools/jdk
export PATH=$JAVA_HOME/bin:$PATH
EOF
source /etc/profile
java -version

Download and extract Tomcat 9.0.50:

wget https://archive.apache.org/dist/tomcat/tomcat-9/v9.0.50/bin/apache-tomcat-9.0.50.tar.gz
tar -xf apache-tomcat-9.0.50.tar.gz
ln -s $(pwd)/apache-tomcat-9.0.50 tomcat

Start Tomcat:

cd tomcat/bin
./startup.sh
# Verify process and port 8080
ps -ef | grep java
ss -lntup | grep 8080

Tomcat Directory Structure

The main directories after installation are:

bin : executable scripts such as startup.sh, shutdown.sh, catalina.sh.

conf : configuration files like server.xml, web.xml, catalina.properties.

logs : log files ( catalina.out, daily logs, access logs).

webapps : default web applications and deployment directory for WAR files.

bin Directory

startup.sh

– start Tomcat on Linux. shutdown.sh – stop Tomcat on Linux. catalina.sh – core script handling start, stop, and JVM options.

conf Directory

server.xml

– defines ports, connectors, virtual hosts, and logging. web.xml – auxiliary configuration.

<?xml version="1.0" encoding="UTF-8"?>
<!-- 8005 shutdown port -->
<Server port="8005" shutdown="SHUTDOWN">
  <Listener className="org.apache.catalina.startup.VersionLoggerListener"/>
  <Service name="Catalina">
    <!-- HTTP connector -->
    <Connector port="8080" protocol="HTTP/1.1" connectionTimeout="20000" redirectPort="8443"/>
    <Engine name="Catalina" defaultHost="localhost">
      <Realm className="org.apache.catalina.realm.LockOutRealm"/>
      <Realm className="org.apache.catalina.realm.UserDatabaseRealm" resourceName="UserDatabase"/>
      <Host name="localhost" appBase="webapps" unpackWARs="true" autoDeploy="true">
        <Valve className="org.apache.catalina.valves.AccessLogValve" directory="logs" prefix="localhost_access_log" suffix=".txt" pattern="%h %l %u %t \"%r\" %s %b"/>
      </Host>
    </Engine>
  </Service>
</Server>

Log Format

%h – client IP address

%l – remote logical username (usually empty)

%u – authenticated user

%t – request time

%r – request line (method and URI)

%s – HTTP status code

%b – bytes sent

" – double quote

logs Directory

catalina.out

– Tomcat application log. catalina.YYYY‑MM‑DD.log – daily rotated log. localhost_access_log.YYYY‑MM‑DD.txt – access log.

Example: Deploying zrlog Application

Download the zrlog WAR package and deploy it as the ROOT application:

mkdir -p /app/war && cd /app/war
wget https://dl.zrlog.com/release/zrlog.war
mv /app/tools/tomcat/webapps /app/tools/tomcat/webapps_bak_$(date +%Y%m%d)
mkdir /app/tools/tomcat/webapps
mv zrlog.war /app/tools/tomcat/webapps/ROOT.war
ls -l /app/tools/tomcat/webapps

Access the application at http://10.0.0.21:8080 and configure the database connection.

Start a MySQL 5.7 container for the database:

docker run -d --name mysql_5.7 -p 3306:3306 --restart always -v /data/mysql:/var/lib/mysql -e MYSQL_ROOT_PASSWORD=1 mysql:5.7
docker exec -it mysql_5.7 bash -c "mysql -uroot -p1 -e 'create database zrlog;'"

Tomcat Multi‑Instance Deployment

Background

When a server has abundant resources, you can run multiple Tomcat instances to better utilize CPU and memory.

Deployment Steps

Prepare Multiple Tomcat Directories

cd /app/tools
tar -xf apache-tomcat-9.0.50.tar.gz
cp -r apache-tomcat-9.0.50 tomcat_8081
cp -r apache-tomcat-9.0.50 tomcat_8082

Modify Ports

Each instance must use unique ports (shutdown, HTTP, HTTPS). Example for the first instance:

sed -i 's/8005/8006/g' tomcat_8081/conf/server.xml
sed -i 's/8080/8081/g' tomcat_8081/conf/server.xml
sed -i 's/8443/8444/g' tomcat_8081/conf/server.xml

And for the second instance:

sed -i 's/8005/8007/g' tomcat_8082/conf/server.xml
sed -i 's/8080/8082/g' tomcat_8082/conf/server.xml
sed -i 's/8443/8445/g' tomcat_8082/conf/server.xml

Start Instances

/app/tools/tomcat_8081/bin/startup.sh
/app/tools/tomcat_8082/bin/startup.sh

Verify that ports 8081 and 8082 are listening:

ss -lntup | grep 8081
ss -lntup | grep 8082

Test Access

Open http://10.0.0.21:8081 and http://10.0.0.21:8082 in a browser to confirm both instances are running.