[users@httpd] mod_rewrite external RewriteMap in high-load setup

[Matthias Wermund <ma...@wermund.de>]

Hello to all,

 

I have a question regarding the use of an external RewriteMap (prg) on a
high-traffic website.

 

My goal is to implement a redirection at the root of the site, depending on
some request attributes (User-Agent and more) sent to an external HTTP
service.

So I implemented a perl script which acts as a RewriteMap. It works like
expected and performs the server-side HTTP call to the external service.

The script is small and quite fast, however, because it involves calling an
external server, it will at any time take about 50ms and more to complete.

 

As under heavy load I can expect up to 100 calls per second, this is will
lead to concurrent calls for sure. I know that I can prevent concurrent
calls to the script by using RewriteLock. But for my understanding this will
queue up the calls, which would introduce a major bottleneck to the
application in this situation.

 

So I would rather prefer to use a multi-threaded approach of the RewriteMap
instead of the lock. Is anything like this possible?

If not: Do you see any alternative approaches to the problem? For example
writing a custom apache module?

 

Thanks in advance for any hints.

 

Matthias