Using "relative" path names

ROOT
1

Hi,

For the first time I’m trying to configure a simple PROOF installation with a basic FS setup. I just followed the basic instructions, and now I can nicely upload and access files like this:

[code]xrdcp my_file root://UserName@myServer//full/path/my_file.root

f = TFile::Open( “root://UserName@myServer//full/path/my_file.root”, “READ” );[/code]

However I would find it way more elegant if I wouldn’t have to know the full path name on the server to be able to upload files to it. I’d just like to write things like:

xrdcp my_file.root root://UserName@myServer/my_file.root

But when I try to do this, I get the message:

I tried reading through the documentation to find out how to do this (like setting an alias that if I don’t specify a full path name starting with “/” then ROOT should assume that I want to write to “/full/path”), but didn’t find it yet. I’m certain that this functionality exists. Could someone advise me how to do it?

Cheers,
Attila

2

Hi Attila,

This is an xrootd issue which should be solvable using the ofs.localroot directive described at

xrootd.slac.stanford.edu/doc/prod/ofs_config.htm

Basically the directive defines a prefix always added to the path that the client sends over. In your example you should try with

ofs.localroot /full/path/

Cheers, Gerri

3

Hi Gerri,

Finally, after a lot of trial-and-error, I managed to do it. There are just too many degrees of freedom in such a configuration file, especially if somebody (like me) has little idea of how xrootd works…

In any case, thanks for the hint, it would’ve taken way longer without it.

Cheers,
Attila

4

Hi again,

Unfortunately I did find another problem.

So now when I try to open files remotely on the file server, everything works great. However when I send a PROOF job to the server itself (which is also the PROOF master) and it tries to open its output file as

TFile::GetType gets a bit “too smart” and recognises that since its running on myMachine, the specified url is a local url to it. So it tries to open a local file called /pool/temp.root. But the file should be called /full/path/pool/temp.root, so the operation fails.

So I guess I’ll have to give up on exporting a folder with the nice name /pool, and use the real /scratch/xrootd/pool directory for now… (As you can guess, /scratch is the place where I have most of my free space…)

Of course if I would have a dedicated file server to spare that is not part of the PROOF cluster then this would not surface, but I have a fairly small cluster just for testing at the moment.

Cheers,
Attila

5

Hi Attila,

Sorry for the late reply.

Please try by adding

xpd.putrc Path.Localroot /full/path

in the xrootd config file.

This will be used by GetType inside PROOF to localize correctly the local file.

I should automatize this, i.e. when an ofs.localroot directive is found I should generate automatically the relevant Path.Localroot env.
But for the moment this is not done.

Cheers, Gerri