nginx querystring

Introduction

Nginx is a powerful web server and reverse proxy that has the ability to handle high traffic websites. One of the key features in Nginx is query string handling. Query strings are the part of a Uniform Resource Locator (URL) that contains data to be passed to the server. In this article, we will delve deeper into the query string feature of Nginx and how it can help optimize web pages.

passing Query Strings in Nginx

Nginx provides a flexible way of passing query strings to server-side scripts. One of the ways of passing query strings to the scripts is through the use of the $args variable. The $args variable captures everything after the ? in the URL. For example, if the URL is http://example.com/post.php?id=23&user=John, the $args variable will be equal to "id=23&user=John". This variable can then be passed as a parameter to server-side scripts or can be used to form a new URL.

Modifying Query Strings

Nginx provides a way of modifying query strings before they are passed to the server. The ngx_http_rewrite_module module can be used to perform these modifications. The rewrite directive instructs Nginx to rewrite the URL. For example, suppose we want to append a query string to a URL. We can do this by adding the following directive in the Nginx configuration file: ```location / { rewrite ^/account/(.*)$ /account.php?user=$1 last;}```With this configuration, when the URL http://example.com/account/John is requested, Nginx will rewrite it to http://example.com/account.php?user=John. The $1 variable captures the user value in the query string, and it is passed to the server-side script.

Caching Query Strings

Caching query strings can help improve the performance of web pages by reducing the load on the server. Nginx provides a way of caching query strings using the proxy_cache_key directive. The proxy_cache_key directive specifies the key that is used to store the cached content. For example, suppose we want to cache the response to a request to the page http://example.com/page.php?id=23&user=John. We can do this by adding the following configuration in the Nginx configuration file:```location /page.php { proxy_cache_key "$scheme$request_method$host$request_uri$args"; proxy_cache my_cache; proxy_pass http://backend;}```With this configuration, Nginx will cache the content of the page based on the query string. The $args variable captures the query string, and it is used as part of the cache key. The cached content is then served whenever a request with the same query string is made.

Invalidating Cached Queries

Nginx provides a way of invalidating cached queries using the proxy_cache_bypass directive. The proxy_cache_bypass directive specifies conditions under which the cached content should be bypassed. For example, suppose we want to bypass the cache for requests that have the query string parameter debug=true. We can do this by adding the following configuration in the Nginx configuration file:```location / { proxy_cache my_cache; proxy_cache_bypass $http_pragma; proxy_cache_bypass $http_authorization; proxy_cache_bypass $cookie_nocache; proxy_cache_bypass $arg_debug; proxy_pass http://backend;}```With this configuration, Nginx will bypass the cache when the query string parameter debug=true is present, and it will instead fetch the content from the backend.