Master Nginx: From Basics to Advanced Load Balancing and High‑Concurrency Techniques

What is Nginx?

Nginx is a lightweight, high‑performance reverse‑proxy web server supporting HTTP, HTTPS, SMTP, POP3 and IMAP, capable of handling tens of thousands of concurrent connections.

Key Advantages

Cross‑platform, simple configuration

Non‑blocking, high concurrency (2‑3 万 connections, up to 5 万 measured)

Low memory consumption (10 workers ≈150 MB)

Open‑source and low cost

High stability

Built‑in health‑check

Typical Use Cases

Standalone HTTP server for static files

Virtual hosting

Reverse proxy and load balancing

API gateway and security management

How Nginx Handles Requests

server {
    listen 80;
    server_name localhost;
    location / {
        root   html;
        index  index.html index.htm;
    }
}

The master process creates listening sockets, forks worker processes, workers accept connections, register read/write events, and close connections when finished.

High‑Concurrency Model

Nginx uses an asynchronous, non‑blocking event model (epoll) so a few worker processes can serve many requests, unlike a one‑process‑per‑request model.

Forward and Reverse Proxy

Forward proxy fetches resources on behalf of a client; reverse proxy receives client requests and forwards them to backend servers, hiding the origin.

Directory Structure

/usr/local/nginx/
├── conf/
│   ├── nginx.conf
│   └── mime.types
├── html/
│   └── index.html
├── logs/
│   ├── access.log
│   └── error.log
├── sbin/nginx
...

nginx.conf Modules

worker_processes 1;
events {
    worker_connections 1024;
}
http {
    include mime.types;
    default_type application/octet-stream;
    sendfile on;
    keepalive_timeout 65;
    server {
        listen 80;
        server_name localhost;
        location / {
            root html;
            index index.html index.htm;
        }
        error_page 500 502 503 504 /50x.html;
        location = /50x.html {
            root html;
        }
    }
}

Cookie vs Session

Cookies are stored in the client browser; sessions are stored on the server (file, DB, Redis) and hold sensitive data.

Nginx vs Apache

Nginx is lightweight, event‑driven and handles many connections with few resources, while Apache uses a process‑oriented model that consumes more memory and CPU per connection.

Static‑Dynamic Separation and CDN

Separate static resources (HTML, JS, CSS, images) from dynamic content, serve static files via Nginx or a CDN to improve performance and reduce backend load.

Load‑Balancing Algorithms

Round‑robin (default)

Weight

IP‑hash

Fair (third‑party)

URL‑hash (third‑party)

upstream backserver {
    server 1112;
    server 1113 weight=2;
    ip_hash;
}

Rate Limiting

Implemented with limit_req_zone (leaky‑bucket) and limit_conn_zone (concurrent connections).

limit_req_zone $binary_remote_addr zone=one:10m rate=1r/m;
limit_conn_zone $binary_remote_addr zone=myip:10m;

Health Checks

Use ngx_http_proxy_module and ngx_http_upstream_module or the third‑party nginx_upstream_check_module to monitor backend servers.

Compression

http {
    gzip on;
    gzip_min_length 1k;
    gzip_comp_level 2;
    gzip_types text/plain application/javascript text/css;
    gzip_vary on;
}

Worker Processes

Set worker_processes to the number of CPU cores; each worker handles many connections without costly context switches.

Status Codes

Examples: 499 (client closed), 502 (bad gateway) – often caused by upstream timeouts, buffer limits, or long‑running scripts.