need a way to measure delays at all the endpoints of the xrootd federation

[ivukotic]

Now that there are rather large tree-like federations of the xrootd endpoints it becomes important to have optimal delays set at each of the redirectors. When I say "delay" I mean - time that a redirector will wait for an answer from the underlying endpoints/redirectors.
If we make it too short we risk returning "file not found" even if the file is actually there. If we make it too long, we are slowing down things unnecessarily.
So plan is to measure the times each endpoint takes to return an answer (both yes and no), and after a sufficient statistics has been collected analyze the data and set the delays on the redirectors appropriately.
To do this we need a way to measure response times. I've tried several proposed methods but non worked for all of our endpoints (full list is here: https://twiki.cern.ch/twiki/bin/view/AtlasComputing/FaxRedirectors).
Anyhow Andy promised to find and test the way to do this, and this issue has been created to remind him of that promise.

[abh3]

I'm closing this issue. Seems that the current measurements are sufficient for most people.