Theo Schlossnagle originally
donated the DTrace support to Apache HTTP Server in this post:
[PATCH] DTrace probes patch..
Since then, much of that original patch has been committed to trunk, the APR-Util hook probe support has been reworked to be more general, and updates have been made to accommodate trunk changes. Still, noone has spent the time to find an acceptable solution to the naughtier build changes.