Does httpd ProxyPass buffer http POST payload before sending it to backend server?

Question

I'm looking to assert whether, in the case of httpd used as a reverse proxy (mod_proxy_http & ProxyPass) and with a POST request (not chunked), if httpd buffers (memory and/or disk) complete request (POST payload included) BEFORE initiating/starting to send the request to the origin/backend server.

If you don't have the answer, would you recommend an approach to verify this assumption?

Answer 1

Unless you wish to dive into the httpd code or a developer who happens to know answers, probably the easiest way to answer this is with network dumps looking at incoming and outgoing traffic to and from your web servers.

If the proxied service is on the same system as Apache, then you could use the mod_dumpio module to determine it instead.