Apache2 nice to know

Tracking Requests Over Multiple Systems With Unique ID

The UNIQUE_ID enviroment variable will be forwarded in the header to subsequent systems. This part can be configured in global section.

RequestHeader set X-RP-UNIQUE_ID %{UNIQUE_ID}e

On the next hop system the Header Variable must be read and logged. (see http.conf for details)

RewriteEngine   On
RewriteCond     %{HTTP:X-RP-UNIQUE_ID} (.*)
RewriteRule     .* - [E=UNIQUE_ID:%1]