Apache Module mod_proxy_express

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Description:	Dynamic mass reverse proxy extension for `mod_proxy`
Status:	Extension
Module Identifier:	proxy_express_module
Source File:	mod_proxy_express.c
Compatibility:	Available in Apache 2.3.13 and later

Summary

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.

Bugfix checklist

ProxyExpressDBMFile Directive

Description:	Pathname to DBM file.
Syntax:	`ProxyExpressDBMFile pathname`
Context:	server config, virtual host
Status:	Extension
Module:	mod_proxy_express

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 Directive

Description:	DBM type of file.
Syntax:	`ProxyExpressDBMType type`
Default:	`ProxyExpressDBMType default`
Context:	server config, virtual host
Status:	Extension
Module:	mod_proxy_express

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

ProxyExpressEnable Directive

Description:	Enable the module functionality.
Syntax:	`ProxyExpressEnable on\|off`
Default:	`ProxyExpressEnable off`
Context:	server config, virtual host
Status:	Extension
Module:	mod_proxy_express

The ProxyExpressEnable directive controls whether the module will be active.