10.2. Setup

To setup a cache, you must define a cache section and use it in a proxy with
the corresponding http-request and response actions.

10.2.1. Cache section

cache

Declare a cache section, allocate a shared cache memory named <name>, the
size of cache is mandatory.

total-max-size

Define the size in RAM of the cache in megabytes. This size is split in
blocks of 1kB which are used by the cache entries. Its maximum value is 4095.

max-object-size

Define the maximum size of the objects to be cached. Must not be greater than
an half of "total-max-size". If not set, it equals to a 256th of the cache size.
All objects with sizes larger than "max-object-size" will not be cached.

max-age

Define the maximum expiration duration. The expiration is set has the lowest
value between the s-maxage or max-age (in this order) directive in the
Cache-Control response header and this value. The default value is 60
seconds, which means that you can't cache an object more than 60 seconds by
default.

10.2.2. Proxy section

http-request cache-use [ { if | unless } ]

Try to deliver a cached object from the cache <name>. This directive is also
mandatory to store the cache as it calculates the cache hash. If you want to
use a condition for both storage and delivering that's a good idea to put it
after this one.

http-response cache-store [ { if | unless } ]

Store an http-response within the cache. The storage of the response headers
is done at this step, which means you can use others http-response actions
to modify headers before or after the storage of the response. This action
is responsible for the setup of the cache storage filter.

Example:

backend bck1
  mode http
  http-request cache-use foobar
  http-response cache-store foobar
  server srv1 127.0.0.1:80
cache foobar
  total-max-size 4
  max-age 240

HAProxy 2.0.14 – Configuration Manual
2020/04/02, willy tarreau