mod_proxy_express
Dynamic mass reverse proxy extension for mod_proxy
Extension
mod_proxy_express.c
proxy_express_module
Available in Apache 2.3.13 and later

This module creates dynamically configured mass reverse proxies, by mapping the `Host:` header of the HTTP request to a server name and backend URL stored in a DBM file. This allows for easy use of a huge number of reverse proxies with no configuration changes. It is much less feature-full than mod_proxy_balancer, which also provides dynamic growth, but is intended to handle much, much larger numbers of backends. It is ideally suited as a front-end HTTP switch and for micro-services architectures.

This module requires the service of mod_proxy.

# 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.

# Limitations

- This module is not intended to replace the dynamic capability of mod_proxy_balancer. Instead, it is intended to be mostly a lightweight and fast alternative to using mod_rewrite with RewriteMap and the `[P]` flag for mapped reverse proxying.
- It does not support regex or pattern matching at all.
- It emulates: <VirtualHost *:80> ServerName front.end.server ProxyPass "/" "back.end.server:port" ProxyPassReverse "/" "back.end.server:port" </VirtualHost> That is, the entire URL is appended to the mapped backend URL. This is in keeping with the intent of being a simple but fast reverse proxy switch.

mod_proxy
BalancerMember
BalancerGrowth
BalancerPersist
BalancerInherit
ProxyExpressEnable
Enable the module functionality.
ProxyExpressEnable on|off
ProxyExpressEnable off
server config
virtual host

The ProxyExpressEnable directive controls whether the module will be active.

ProxyExpressDBMFile
Pathname to DBM file.
ProxyExpressDBMFile pathname
server config
virtual host

The ProxyExpressDBMFile directive points to the location of the Express map DBM file. This file serves to map the incoming server name, obtained from the `Host:` header, to a backend URL.

# Note

The file is constructed from a plain text file format using the `httxt2dbm` utility.

# ProxyExpress map file

##
##express-map.txt:
##
www1.example.com http://192.168.211.2:8080
www2.example.com http://192.168.211.12:8088
www3.example.com http://192.168.212.10

# Create DBM file

httxt2dbm -i express-map.txt -o emap

# Configuration

ProxyExpressEnable on ProxyExpressDBMFile emap
ProxyExpressDBMType
DBM type of file.
ProxyExpressDBMType type
ProxyExpressDBMType default
server config
virtual host

The ProxyExpressDBMType directive controls the DBM type expected by the module. The default is the default DBM type created with `httxt2dbm`.

Possible values are (not all may be available at run time):

Value | Description
--- | ---
`db` | Berkeley DB files
`gdbm` | GDBM files
`ndbm` | NDBM files
`sdbm` | SDBM files (always available)
`default` | default DBM type