Just for completeness, xrdfs is the follow-on replacement for xrd. The xrdfs 
command is based on the new client and is generally more user-friendly.

Andy

-----Original Message----- 
From: Daniel L. Wang
Sent: Thursday, April 23, 2015 4:56 PM
To: qserv-l
Subject: [QSERV-L] Diagnosing and debugging xrootd-related problems (xrd)

Hello,

I would like to draw your attention to an xrootd utility that can be
helpful in testing/diagnosing xrootd-related problems in qserv.

Have a look at "xrd". You can think of it as a command-line tool that
speaks the xrootd protocol. It supports several commands and using it is
generally far easier than writing code that links to xrootd client
libraries and wondering whether you're doing it right.

Example:
----------
[danielw@lsst-dbdev2 xrdbuild]$ src/xrd
(C) 2004-2010 by the Xrootd group. Xrootd version: v20150319-d2df123
Welcome to the xrootd command line interface.
Type 'help' for a list of available commands.
> locateall /chk/qservTest_case01_qserv
Not connected to any server.

> connect lsst-dbdev2:1094
root://lsst-dbdev2.ncsa.illinois.edu:1094//> locateall
/chk/qservTest_case01_qserv
No matching files were found.

root://lsst-dbdev2.ncsa.illinois.edu:1094//> locateall
/chk/qservTest_case01_qserv/6630


------------- Location #1
InfoType: kXrdcLocDataServer
CanWrite: true
Location: '141.142.237.34:1099'

root://lsst-dbdev2.ncsa.illinois.edu:1094//> locateall
/chk/qservTest_case01_qserv/6639123
No matching files were found.

root://lsst-dbdev2.ncsa.illinois.edu:1094//> Goodbye.

[danielw@lsst-dbdev2 xrdbuild]$
----------

Note that when you connect, you should always connect to the xrootd
daemon, because there is no client protocol for the cmsd.  Still, you
can use this to connect to xrootd daemons to see what they know. I think
you can use it to perform the sort of cold-start precaching that would
speed up the first queries on a cluster whose redirector has just been
restarted. We could probably use a similar command-line tool that, say,
could issue queries as a sort of one-shot czar without bringing the czar
up and down.

So, when you get chunk missing errors, or weird error messages, point
this at the cluster and see what happens. Unfortunately, there isn't any
such command-line tool for XrdSsi (though I think a simple one could be
made: push a stream of bytes to a server addressed by a path, and dump
everything that comes back).

Good luck,
-Daniel

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