Nginx Introduction, Installation, Load‑Balancing Configuration and Tomcat Setup on CentOS 7

Nginx Overview – Nginx is a free, open‑source, high‑performance HTTP server and reverse proxy used by major Chinese internet companies. A reverse proxy receives external requests, forwards them to internal servers, and returns the responses to clients.

Load‑Balancing Algorithms

Weight (round‑robin) – distributes requests sequentially; servers can be weighted to receive more traffic.

ip_hash – hashes the client IP so the same client always reaches the same backend, helping with session sharing.

fair – dynamically balances based on response time (requires the upstream_fair module).

url_hash – hashes the request URL to a fixed backend (requires the hash module).

Installing Nginx on CentOS 7

Download the tarball (e.g., wget -c https://nginx.org/download/nginx-1.6.3.tar.gz ), install prerequisites, extract, configure and compile:

yum install gcc-c++
yum install -y pcre pcre-devel
yum install -y zlib zlib-devel
yum install -y openssl openssl-devel

tar -zxvf nginx-1.6.3.tar.gz
cd nginx-1.6.3
./configure
make install
whereis nginx
cd /usr/local/nginx/sbin
./nginx   # start
./nginx -s stop   # stop
./nginx -s quit   # graceful stop
./nginx -s reload # reload config

Modify nginx.conf (e.g., change listen 80 to listen 83 ) and reload.

Installing Tomcat

Download and extract the tarball, rename directories, and adjust ports in server.xml :

wget http://apache.mirrors.tds.net/tomcat/tomcat-8/v8.5.40/bin/apache-tomcat-8.5.40.tar.gz
tar -zxvf apache-tomcat-8.5.40.tar.gz
mv apache-tomcat-8.5.40 tomcat-1
mv apache-tomcat-8.5.40 tomcat-2
# edit server.xml to set ports 8080 and 8081, adjust shutdown, AJP, etc.
cd tomcat-1/bin
sh startup.sh
cd tomcat-2/bin
sh startup.sh
ps -ef|grep tomcat

Create simple index.html files in each webapps/ROOT to verify access via http:// ip :8080 and http:// ip :8081 .

Nginx Load‑Balancing Configuration

Edit /usr/local/nginx/conf/nginx.conf and add an upstream block pointing to the two Tomcat instances:

upstream test.com {
    server 127.0.0.1:8080 weight=1;
    server 127.0.0.1:8081 weight=2;
}
server {
    listen 83;
    server_name localhost;
    location / {
        proxy_pass http://test.com;
        proxy_redirect default;
    }
    error_page 500 502 503 504 /50x.html;
    location = /50x.html { root html; }
}

Key parameters explained:

worker_processes – number of worker processes (usually equals CPU cores).

worker_connections – max connections per worker.

sendfile – enables efficient file transmission.

keepalive_timeout – timeout for persistent connections.

upstream – defines the backend server pool.

After editing, reload Nginx with ./nginx -s reload and test by repeatedly refreshing http:// ip :83 . The load‑balancing effect can be observed.

Common Failure Reason

Many users cannot reach the Nginx page because the firewall blocks incoming traffic; ensure the appropriate ports are open.