Proxy Pass Configuration Examples

When configuring Nginx as a reverse proxy, the behavior of the proxy_pass directive can vary depending on the presence of a trailing slash in the URL.

Example 1: Proxy Pass with Trailing Slash

location ^~ /abc/ {
    proxy_pass http://192.168.1.1:8080/;
}

• A request to http://www.a.com/abc/a.html will be forwarded to http://192.168.1.1:8080/a.html
• The trailing slash in proxy_pass removes the /abc prefix from the request URI

Example 2: Proxy Pass without Trailing Slash

location ^~ /abc/ {
    proxy_pass http://192.168.1.1:8080;
}

• A request to http://www.a.com/abc/a.html will be forwarded to http://192.168.1.1:8080/abc/a.html
• The original request URI is appended to the proxy URL

HTTP Request Headers Overview

HTTP headers are key-value pairs sent in the request and response messages of the HTTP protocol. These headers provide metadata about the request or response and help control the behavior of web servers and clients.

Common Request Headers

• Accept - Specifies the content types the client can handle
• Accept-Charset - Indicates supported character sets
• Accept-Encoding - Lists supported content encodings (e.g., gzip)
• Accept-Language - Preferred languages for the response
• Authorization - Credentials for HTTP authentication
• Cache-Control - Directives for caching mechanisms
• Connection - Controls network connection behavior (e.g., keep-alive)
• Cookie - Client-side stored session data
• Content-Length - Size of the request body in bytes
• Content-Type - Media type of the request body
• Date - Timestamp of request
• Host - Target domain name or IP address

Custom Headers in Reverse Proxy Configurations

When using Nginx as a reverse proxy, you can set custom headers using the proxy_set_header directive:

location / {
    proxy_pass http://backend;
    proxy_set_header X-Real-IP $remote_addr;
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    proxy_set_header Host $host;
}

Common Proxy Headers

• X-Forwarded-For - Identifies the originating IP address of a client
• X-Forwarded-Proto - Informs the backend about the original protocol (http/https)
• X-Real-IP - Passes the client's real IP address to the backend

Common Pitfall: Missing X-Forwarded-Proto Header

When terminating SSL at the Nginx layer and forwarding requests to backend servers, it's crucial to set the X-Forwarded-Proto header:

location / {
    proxy_pass http://backend;
    proxy_set_header Host $host;
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    proxy_set_header X-Forwarded-Proto https;
}

• Failing to set this header can cause issues with applications that enforce HTTPS connections
• In some cases, this can lead to infinite redirect loops or unexpected behavier

Advanced Proxy Configuration Example

Multiple upstream servers with different routing rules:

upstream static_servers {
    server 192.168.10.173:80;
    server 192.168.10.174:80;
}

upstream app_servers {
    server 192.168.10.173:8080;
    server 192.168.10.174:8080;
}

server {
    listen 80;
    server_name grace.kevin.com;

    location / {
        proxy_pass http://static_servers;
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    }

    location ^~ /leasecore/ {
        proxy_pass http://app_servers;
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    }

    location ^~ /cms/api/ {
        proxy_pass http://app_servers;
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    }
}