HAProxy http-reuse condition

I have a setup of HAProxy 2.2 with connection reuse.

From a single external IP I’m sending many non-keepalive requests to the proxy but I’m getting reuse hits only when http-reuse is set to always. If I’m sending keep-alive connections, it works also with the http-reuse safe option.

So I’m wondering, what are the conditions for a connection to be considered to be reused in HAProxy?

The documentation states:

By default, a connection established between haproxy and the backend server which is considered safe for reuse is moved back to the server’s idle connections pool so that any other request can make use of it. This is the “safe” strategy below.