FIT 14.6.5 & Web Accelerator with improved caching
Doing nothing at all is better than doing something fast. That’s what caching is all about. This release has a lot of features to avoid unnecessary work. FIT has had a HTTP Cache for a long time. But when the time-to-live of a cached resource has passed, the content had to be requested again. While it is mandatory to contact the origin server again, it is not necessary to actually download an unchanged resource. HTTP provides conditional requests and the status code 304 for an intermediary cache to check whether the local copy a file is still valid. In many cases this check is much faster than a fresh download. Especially for short-lived resources this can greatly reduce bandwidth use and network traffic for origin servers.
There is also CPU time to save. FIT carries out CPU intensive work on image files. System operators now have better control how the disk cache is managed. The new option
CACHE_DISK_MIN_FREE_PERCENT avoids premature cache cleanups. As long as the regular automatic check finds enough free disk space, no files are deleted. Only if the configured threshold is exceeded, files are deleted. If you have enough disk space, this can reduce CPU usage significantly by eliminating repeated calculations.
Sometimes it is necessary to manually purge a cache. For example, if a resource changes but its URL stays the same. The
fitadmin maintenance clearcache command now offers to delete only parts of the cache. For example
--http clears the request cache but leaves the precious Image Compression cache untouched.