Apache HTTP Server Version 2.4

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# Apache Module mod_proxy_http2

Description: | HTTP/2 support module for `mod_proxy`
Status: | Extension
Module Identifier: | proxy_http2_module
Source File: | mod_proxy_http2.c
Compatibility: | Available in httpd 2.4.19 and later

### Summary

`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.

### Topics

- Basic Examples
- Request notes

### Directives

This module provides no directives.

### Bugfix checklist

- httpd changelog
- Known issues
- Report a bug

### See also

- `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.