I'm using Apache as a reverse proxy. The request contain important information
that can not be passed in clear text between machines. I tried to use the
connect to the backend server using https.

<virtualHost _default:443>

SSLProxyEngine on
ProxyPass /proxy-s/ https://realserver/app/ max=5
</virtual>

We benchmarked the performance, and found noticable slowness on the proxy-s
path, compared with accessing the "realserver" app over HTTPS. The delay is ~0.1
seconds/request. It turned out that regardless of any setting, Apache does not
use KeepAlive connections to connect to https backends. Each request require an
HTTPS connection setup.

When using HTTP to connect to the real server, the cost of running the requests
through the proxy was < 0.01 second/request, and significantly less with
Keep-Alive & connection pooling.

For my application, direct https connection (with Keep-Alive) takes ~1.5
seconds/per 100 requests (including ~0.1 seconds for the inital SSL setup). The
10 seconds delay (0.1*100) prevent high-load applications from using Apache, if
the proxied connection must be secured.

The code in mod_proxy_http.c (2.2.4) states:

    /*
     * TODO: Currently we cannot handle persistent SSL backend connections,
     * because we recreate backend->connection for each request and thus
     * try to initialize an already existing SSL connection. This does
     * not work.
     */
    if (is_ssl)
        backend->close_on_recycle = 1;


IS IT POSSIBLE TO REMOVE THIS LIMIT ?