Re: [ROOT] rootd io

From: Fons Rademakers (Fons.Rademakers@cern.ch)
Date: Mon Apr 09 2001 - 12:24:12 MEST


Hi Ulrich,

Ulrich Fricke wrote:
> 
> Hi there,
> 
> I am thinking of using the TNetFile to access remote files.
> The files will be distributed between different serves and the user
> should not need to know the exact location. We already have a system
> which can access files this way, but the request and the data transfer
> are different than for rootd:
> 
> The client contacts a central server. Then the server determines which of
> the data pool has the file and this pool contact the client back.
> 
> Is there a way to tell the rootd daemon to receive requests
> on one port (like the default one 1094) and sent/receive the
> data via another one?
>
Not for the time being.

As I see there are two possibilities to solve this problem you describe:

- the user app, the one that opens files via TNetFile, talks to the
  disk pool manager or file catalogue to obtain the mapping between logical
  file name and physical filename and then call TNetFile with the physical
  filename

- extend rootd to allow for some plugin module which will be able to
  contact the file catalogue (maybe depending on the filename, or just
  always when the file is not found locally) to obtain the physical
  filename.

The first solution you can implement now, for the second I need to extend
rootd and you will have to write the plugin that comminucates with your
file catalogue (and you case could be a good first "use case" for such
a plugin).

Cheers, Fons.


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