Master Nginx: Installation, Configuration, Load Balancing & Caching

Environment Preparation

Server: CentOS 7.2. Ensure network connectivity, yum availability, firewalld stopped, and SELinux set to permissive.

# Check firewalld status
systemctl status firewalld.service
# Stop firewalld temporarily
systemctl stop firewalld.service

# Check SELinux status
getenforce
# Set SELinux to permissive temporarily
setenforce 0

# Install required tools
yum -y install gcc gcc-c++ autoconf pcre pcre-devel make automake wget httpd-tools vim

What is Nginx?

Nginx is an open‑source, high‑performance HTTP server and reverse‑proxy middleware. It uses an event‑driven architecture (epoll) and supports modular extensions.

Key Advantages

Event‑driven I/O (epoll) – efficiently handles many concurrent connections.

Lightweight core – only essential HTTP modules are built‑in; additional features are added as dynamic modules.

CPU affinity – worker processes can be bound to specific CPU cores to reduce cache misses.

Installation (LNMP package)

The LNMP one‑click package installs Nginx, PHP and MySQL.

wget -c http://soft.vpser.net/lnmp/lnmp1.4.tar.gz && \
    tar zxf lnmp1.4.tar.gz && cd lnmp1.4 && \
    ./install.sh lnmp
# Default installation prefix
/usr/local

Basic nginx.conf

user  nginx;
worker_processes  auto;
error_log  /var/log/nginx/error.log;
pid        /var/run/nginx.pid;

events {
    worker_connections  1024;
    use                epoll;
}

http {
    sendfile        on;
    keepalive_timeout  65;
    log_format  main  '$remote_addr - $remote_user [$time_local] "$request" '
                      '$status $body_bytes_sent "$http_referer" '
                      '"$http_user_agent"';
    access_log  /usr/local/access.log  main;

    server {
        listen       80;
        server_name  localhost;

        location / {
            root   /path/to/your/site;
            index  index.html index.htm;
        }

        error_page 500 504 /50x.html;
        location = /50x.html {
            root /path/to/error/pages;
        }
    }
}

Multiple server blocks can be defined inside the http block to host virtual hosts.

Static Asset Service

Serve HTML, CSS, JS, images, video, and generic files directly.

location ~ \.(html|htm)$ {
    expires 12h;
}

Browser Caching

Use expires or Cache‑Control headers. Nginx automatically adds ETag and Last‑Modified. Subsequent requests with If-Modified-Since or If-None-Match may receive 304 Not Modified.

Cross‑Origin Resource Sharing (CORS)

location ~ \.(html|htm)$ {
    add_header Access-Control-Allow-Origin "*";
    add_header Access-Control-Allow-Methods "GET,POST,PUT,DELETE,OPTIONS";
    # add_header Access-Control-Allow-Credentials "true";  # use specific origin when enabled
}

Anti‑Hotlinking

location ~ \.(jpg|gif|png)$ {
    valid_referers none blocked 127.0.0.1;
    if ($invalid_referer) {
        return 403;
    }
}

Reverse Proxy

server {
    listen 80;
    location / {
        proxy_pass http://127.0.0.1:8080/;
        proxy_set_header Host $http_host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_connect_timeout 30;
        proxy_send_timeout 60;
        proxy_read_timeout 60;
        proxy_buffering on;
        proxy_buffers 4 128k;
        proxy_busy_buffers_size 256k;
        proxy_max_temp_file_size 256k;
    }
}

Load Balancing

upstream backend {
    server 127.0.0.2;
    server 127.0.0.3;
    # optional parameters: weight=5, max_fails=3, fail_timeout=30s, backup, down
}

server {
    listen 80;
    server_name localhost;
    location / {
        proxy_pass http://backend;
        include proxy.conf;
    }
}

Supported scheduling algorithms: round‑robin (default), weighted round‑robin, ip_hash, least_conn, hash $request_uri (url_hash).

Proxy Caching

http {
    proxy_cache_path /var/www/cache levels=1:2 keys_zone=test_cache:10m \
                     max_size=10g inactive=60m use_temp_path=off;

    server {
        location / {
            proxy_cache test_cache;
            proxy_cache_valid 200 304 12h;
            proxy_cache_valid any 10m;
            proxy_cache_key $host$uri$is_args$args;
            add_header X-Cache-Status $upstream_cache_status;
        }
    }
}

To bypass caching for login or registration URLs:

if ($request_uri ~ ^/(login|register)) { set $nocache 1; }
location / {
    proxy_no_cache $nocache $arg_nocache $arg_comment $http_pragma $http_authorization;
}

Slice Module (large file chunking)

Available from Nginx 1.9. Use the slice directive to split large files into smaller chunks.

slice 1m;   # each chunk 1 MiB

Common Configuration Questions

Duplicate server_name

If multiple server blocks define the same server_name, Nginx uses the configuration that is read last (order of include files matters).

Location Matching Priority

=   # exact match
^~  # prefix match, stop further search
~   # case‑sensitive regex
~*  # case‑insensitive regex

Using try_files

location / {
    try_files $uri $uri/ /index.php;
}

alias vs root

# root example
location /request_path/image/ {
    root /local_path/image/;   # maps to /request_path/image/local_path/image/...
}

# alias example
location /request_path/image/ {
    alias /local_path/image/;  # maps directly to /local_path/image/...
}

Preserving Real Client IP

# First proxy
set $x_real_ip $remote_addr;

# Last proxy
real_ip $x_real_ip;

Typical Error Codes

413 – Request Entity Too Large (adjust client_max_body_size)

503 – Bad Gateway (backend not responding)

504 – Gateway Timeout (backend timed out)