fastcgi_cache_background_update
The `fastcgi_cache_background_update` directive allows updates to the cache in the background while the current response is served.
Description
The fastcgi_cache_background_update directive is a Boolean flag that controls whether NGINX will update the cached FastCGI content in the background if the content is stale when accessed. When set to on, it allows simultaneous serving of the existing cached response while a new request is made to fetch the updated content, which is particularly useful in high traffic situations where waiting for a cache refresh can lead to delays and increased load times. This means that users will continue to receive the cached version while a potentially time-consuming back-end request is handled behind the scenes.
In contrast, if this directive is set to off (the default), users requesting stale cached responses will experience the overhead of waiting for a fresh request before receiving an updated version. This is less efficient in terms of user experience and resource utilization. This directive can be applied in the http, server, or location contexts, enabling flexibility in controlling cache behaviors depending on the needs of the application or specific routes.
Setting this directive correctly can greatly enhance the responsiveness and speed of web applications that rely heavily on FastCGI caching, as it minimizes the load and waiting times for cached content updates. However, care must be taken to handle cache invalidation to prevent serving outdated content for too long, particularly in dynamic applications where data changes frequently.
Config Example
location /api {
fastcgi_pass backend;
fastcgi_cache my_cache;
fastcgi_cache_background_update on;
}Ensure the backend can handle concurrent requests efficiently to avoid performance issues.
Be cautious with cache timing settings to prevent stale data being served indefinitely.