Master Nginx: From Static Server to Load Balancing and Reverse Proxy

1. HTTP Server

Nginx can serve static resources directly. When a site consists only of static pages, you can deploy it by placing files under the document root and configuring a simple server block.

1. Create an html directory under the document root ( /usr/local/var/www) and add test.html.

2. Configure nginx.conf with a server block:

user mengday staff;

http {
    server {
        listen       80;
        server_name  localhost;
        client_max_body_size 1024M;

        # default location
        location / {
            root   /usr/local/var/www/html;
            index  index.html index.htm;
        }
    }
}

3. Test access:

http://localhost/ → /usr/local/var/www/index.html (default Nginx page)

http://localhost/test.html → /usr/local/var/www/html/test.html

Note: If you encounter a 403 Forbidden when accessing images, adjust the user directive in nginx.conf (e.g., user root on Linux or user $(who am i) on macOS) and reload the configuration.

2. Static Server

In many companies a static server provides an upload function for other applications to fetch static resources.

1. Under /usr/local/var/www create images and img directories and place a test.jpg in each.

http {
    server {
        listen       80;
        server_name  localhost;

        set $doc_root /usr/local/var/www;

        # default location
        location / {
            root   /usr/local/var/www/html;
            index  index.html index.htm;
        }

        location ^~ /images/ {
            root $doc_root;
        }

        location ~* \.(gif|jpg|jpeg|png|bmp|ico|swf|css|js)$ {
            root $doc_root/img;
        }
    }
}

Custom variables are defined with the set directive. Static location mapping can use path prefixes (e.g., /images/) or file‑extension patterns.

Accessing http://localhost/test.jpg maps to $doc_root/img. When multiple locations match, ^~ has higher priority than ~, so the /images/ block is chosen.

Common location matching types and their priority (high to low): = exact match ^~ prefix match (stop search) ~ case‑sensitive regex ~* case‑insensitive regex

regular string prefix / generic match

3. Reverse Proxy

Reverse proxy is a major Nginx feature. It receives external requests and forwards them to internal servers, returning the response to the client.

Example: a Java web application running on port 8081.

server {
    listen       80;
    server_name  localhost;

    location / {
        proxy_pass http://localhost:8081;
        proxy_set_header Host $host:$server_port;
        # set client IP
        proxy_set_header X-Forwarded-For $remote_addr;
        proxy_next_upstream error timeout invalid_header http_500 http_502 http_503;
    }
}

Visiting http://localhost/ proxies the request to localhost:8081.

4. Load Balancing

Load balancing distributes requests across multiple backend servers. Nginx uses the upstream directive. The default strategy is round‑robin.

upstream web_servers {
    server localhost:8081;
    server localhost:8082;
}

server {
    listen       80;
    server_name  localhost;

    location / {
        proxy_pass http://web_servers;
        proxy_set_header Host $host:$server_port;
    }
}

Other strategies include weight‑based, ip_hash, fair (third‑party), and url_hash (third‑party).

# weight example
upstream test {
    server localhost:8081 weight=1;
    server localhost:8082 weight=3;
    server localhost:8083 weight=4 backup;
}

# ip_hash example
upstream test {
    ip_hash;
    server localhost:8080;
    server localhost:8081;
}

# fair (third‑party)
upstream backend {
    fair;
    server localhost:8080;
    server localhost:8081;
}

# url_hash (third‑party)
upstream backend {
    hash $request_uri;
    hash_method crc32;
    server localhost:8080;
    server localhost:8081;
}

5. Dynamic‑Static Separation

Separating dynamic and static resources allows caching of static assets. A typical configuration combines an upstream for dynamic requests and location blocks for static files.

upstream web_servers {
    server localhost:8081;
    server localhost:8082;
}

server {
    listen       80;
    server_name  localhost;

    set $doc_root /usr/local/var/www;

    location ~* \.(gif|jpg|jpeg|png|bmp|ico|swf|css|js)$ {
        root $doc_root/img;
    }

    location / {
        proxy_pass http://web_servers;
        proxy_set_header Host $host:$server_port;
    }

    error_page 500 502 503 504  /50x.html;
    location = /50x.html {
        root $doc_root;
    }
}

6. Other Useful Directives

return

– returns an HTTP status code or redirects. rewrite – rewrites the request URI using regular expressions. error_page – defines custom error pages. log_format and access_log – configure request logging. deny – blocks access to matched resources.

Built‑in variables such as $args, $content_length, $host, $remote_addr, etc., can be used in configurations.