mod_proxy_http2
HTTP/2 support module for mod_proxy
Experimental
mod_proxy_http2.c
proxy_http2_module
Available in httpd 2.4.19 and later

mod_proxy_http2 supports HTTP/2 only, it does not provide any downgrades to HTTP/1.1. This means that the backend needs to support HTTP/2 because HTTP/1.1 will not be used instead.

This module requires the service of mod_proxy, so in order to get the ability of handling HTTP/2 proxy requests, mod_proxy and mod_proxy_http2 need to be both loaded by the server.

mod_proxy_http2 works with incoming fronted requests using HTTP/1.1 or HTTP/2. In both cases, requests proxied to the same backend are sent over a single TCP connection whenever possible (namely when the connection can be re-used).

Caveat: there will be no attempt to consolidate multiple HTTP/1.1 frontend requests (configured to be proxied to the same backend) into HTTP/2 streams belonging to the same HTTP/2 request. Each HTTP/1.1 frontend request will be proxied to the backend using a separate HTTP/2 request (trying to re-use the same TCP connection if possible).

This module relies on libnghttp2 to provide the core http/2 engine.

# Warning

This module is experimental. Its behaviors, directives, and defaults are subject to more change from release to release relative to other standard modules. Users are encouraged to consult the "CHANGES" file for potential updates.

# Warning

Do not enable proxying until you have secured your server. Open proxy servers are dangerous both to your network and to the Internet at large.

mod_http2
mod_proxy
mod_proxy_connect

# Basic Examples

The examples below demonstrate how to configure HTTP/2 for backend connections for a reverse proxy.

## HTTP/2 (TLS)

ProxyPass "/app" "h2://app.example.com" ProxyPassReverse "/app" "https://app.example.com"

## HTTP/2 (cleartext)

ProxyPass "/app" "h2c://app.example.com" ProxyPassReverse "/app" "http://app.example.com"

The schemes to configure above in ProxyPassReverse for reverse proxying `h2` (or `h2c`) protocols are the usual `https` (resp. `http`) as expected/used by the user agent.

# Request notes

mod_proxy_http creates the following request notes for logging using the `%{VARNAME}n` format in LogFormat or ErrorLogFormat:

proxy-source-port
  The local port used for the connection to the backend server.
proxy-status
  The HTTP/2 status received from the backend server.

# HTTP/2 PUSH

The module does not support the HTTP/2 feature PUSH. Backend servers that would like to advertise preload resources should send the appropriate `Link` headers.

If available, they may do so using the `"103 Early Hints"` intermediate responses as specified in RFC 8297. This will give the best performance. If the client is talking HTTP/2 as well, this may then result in a PUSH from Apache to the client or just in forwarding the 103 response.