Unable to open some URL with ROOT TFile

[Mark_C_Hodgkinson]

Hello,

I am trying to access this file from ROOT:

https://atlas-opendata.web.cern.ch:443/Legacy13TeV/2lep/MC/mc_364100.Zmumu_PTV0_70_CVetoBVeto.2lep.root

I verified I can download it from a web browser.

But in ROOT I cannot open it:

python
Python 3.12.5 (main, Aug 6 2024, 19:08:49) [Clang 15.0.0 (clang-1500.3.9.4)] on darwin
Type “help”, “copyright”, “credits” or “license” for more information.

from ROOT import TFile
TFile.Open(“https://atlas-opendata.web.cern.ch/Legacy13TeV/2lep/MC/mc_364100.Zmumu_PTV0_70_CVetoBVeto.2lep.root”)
Error in TWebFile::TWebFile: https://atlas-opendata.web.cern.ch:443/Legacy13TeV/2lep/MC/mc_364100.Zmumu_PTV0_70_CVetoBVeto.2lep.root? does not exist
Traceback (most recent call last):
File “”, line 1, in
File “/opt/hep/root/6.30.06/lib/ROOT/_pythonization/_tfile.py”, line 103, in _TFileOpen
raise OSError(‘Failed to open file {}’.format(str(args[0])))
OSError: Failed to open file https://atlas-opendata.web.cern.ch/Legacy13TeV/2lep/MC/mc_364100.Zmumu_PTV0_70_CVetoBVeto.2lep.root

whilst uproot is able to open it:

import uproot

miniTreeZmumu = uproot.open(“https://atlas-opendata.web.cern.ch/Legacy13TeV/2lep/MC/mc_364100.Zmumu_PTV0_70_CVetoBVeto.2lep.root")["mini”]

I also verified that ROOT TFile can open URL in general:

TFile.Open(“https://root.cern/files/na49.root”)
<cppyy.gbl.TWebFile object at 0x12300d000>

So there seems to be some specific problem with TFile and the CERN open access data URLs? Do you have an idea what could be the problem?

I am on a Mac (14.6.1) and have compiled ROOT from source (6.30/06)

Cheers,

Mark

[yus]

Hi,

works for me on lxplus9 with ROOT 6.30.02-x86_64-el9-gcc13-opt and python 3.9.12:

$ setupATLAS -q; lsetup "root 6.30.02-x86_64-el9-gcc13-opt"
...
$ python
Python 3.9.12 (main, Jul 11 2023, 14:40:15)
[GCC 13.1.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> from ROOT import TFile
>>> TFile.Open("https://atlas-opendata.web.cern.ch/Legacy13TeV/2lep/MC/mc_364100.Zmumu_PTV0_70_CVetoBVeto.2lep.root")
<cppyy.gbl.TDavixFile object at 0x5c95980>

[linev]

Do you have davix installed on your system. Plain TWebFile may not support some special http features.

[Mark_C_Hodgkinson]

I don’t know. Do I need Davix for this to work?

[linev]

Most probably - yes.

[Mark_C_Hodgkinson]

Installing Davix does not help. Homebrew installed davix–0.8.7.arm64_sonoma, but the problem persists.

[pcanal]

Does you build of ROOT has the support for Davix enabled? (see result of root-config --features)

[Mark_C_Hodgkinson]

I’m not sure on that - I don’t have my build area by now, but I can try rebuilding. It might be Davix was not found and so that was disabled?

However I also see the same problem if I use ROOT via:

source /cvmfs/sft.cern.ch/lcg/views/LCG_106/arm64-mac12-clang140-opt/setup.sh

and it seems surprising to me an official install misses Davix support if this is a requirement?

Cheers,

Mark

[pcanal]

root-config should work from the installed version to tell you which features is enabled.

[Mark_C_Hodgkinson]

aha yes just realised that

root-config --features | grep -i davix

shows no result for either my install or the LCG install.

So this seems to mean I have to build root locally and enable davix, whilst from cvmfs its not possible to use this feature of ROOT due to the choices made when LCG built ROOT?

[Mark_C_Hodgkinson]

Just to confirm rebuilding ROOT on my laptop with Davix enabled solves the problem for me.

Thanks,

Mark