10. Cache

HAProxy provides a cache, which was designed to perform cache on small objects
(favicon, css...). This is a minimalist low-maintenance cache which runs in
RAM.
 
The cache is based on a memory which is shared between processes and threads,
this memory is split in blocks of 1k.
 
If an object is not used anymore, it can be deleted to store a new object
independently of its expiration date. The oldest objects are deleted first
when we try to allocate a new one.
 
The cache uses a hash of the host header and the URI as the key.
 
It's possible to view the status of a cache using the Unix socket command
"show cache" consult section 9.3 "Unix Socket commands" of Management Guide
for more details.
 
When an object is delivered from the cache, the server name in the log is
replaced by "<CACHE>".