Re: Manage a ROOT file from a streaming of the ROOT file content

From: Massimiliano Fasi <Massimiliano.Fasi_at_pg.infn.it>
Date: Mon, 23 Apr 2012 11:06:58 +0200

Thank you, it exactly answered my question about URL pattern. I changed it (and moved the ROOT file I wanted to read in hdfs' root directory), but still things went wrong, and I got the same error:

SysError in <THDFSFile::THDFSFile>: Unable to open file hdfs:///mySearchTreeFile_68_2_Ewz.root in HDFS (No such file or directory)
SysError in <THDFSFile::THDFSFile>: file hdfs:///mySearchTreeFile_68_2_Ewz.root can not be opened for reading (No such file or directory)

• Break *** segmentation violation Generating stack trace... [ stack trace follows ]

Cluster seems to be well configured, and I'm sure the file exists: I can check its existence by hadoop applications and open it by FUSE. Any guess?

Cheers,

Massimiliano

Fons Rademakers <Fons.Rademakers_at_cern.ch> ha scritto:

> [added Brian the author of this plugin in cc]
>
> Have a look at the doc here:
>
> http://root.cern.ch/lxr/source/io/hdfs/src/THDFSFile.cxx
>
> Cheers, Fons.
>
>
> On 23/04/2012 10:15, Massimiliano Fasi wrote:
>> Hi Fons,
>>
>> you were right. I re-built ROOT library with HDFS plugin, and now ROOT is
>> able to find HDFS library, but application still doesn't work. I get this
>> error:
>>
>> SysError in <THDFSFile::THDFSFile>: Unable to open file
>> hdfs://hydra1:54310/user/fasi/testROOT/mySearchTreeFile_68_2_Ewz.root in
>> HDFS (No such file or directory)
>> SysError in <THDFSFile::THDFSFile>: file
>> hdfs://hydra1:54310/user/fasi/testROOT/mySearchTreeFile_68_2_Ewz.root can
>> not be opened for reading (No such file or directory)
>>
>> *** Break *** segmentation violation
>> Generating stack trace...
>> [ stack trace follows ]
>>
>> But I'm sure the file /user/fasi/testROOT/mySearchTreeFile_68_2_Ewz.root
>> exists in HDFS. Is there in your opinion any mistake in path string or
>> somewhere else?
>>
>> Thank you,
>>
>> Massimiliano
>>
>> Fons Rademakers <Fons.Rademakers_at_cern.ch> ha scritto:
>>
>>> Of course you've to make sure the HDFS plugin is build. It is not part of
>>> the standard binary version. Get the source and make sure all
>>> prerequisite libs for HDFS support are installed and do
>>>
>>> ./configure
>>> make
>>>
>>> Cheers, Fons.
>>>
>>> On 22 Apr 2012, at 09:28, Massimiliano Fasi
>>> <Massimiliano.Fasi_at_pg.infn.it> wrote:
>>>
>>>> Hi Fons,
>>>>
>>>> and thank you for your explanation. I tried to use TFile::Open(),
>>>> getting a different behaviour of the application. Indeed, now I get this
>>>> error:
>>>>
>>>> Error in <TUnixSystem::DynamicPathName>: HDFS[.so | .dll | .dylib | .sl
>>>> | .dl | .a] does not exist in
>>>> :/storage/root/root/lib/root:/storage/root/root/lib/root:/storage/root/root/lib/root:/storage/root/root/lib/root:/storage/root/root/lib/root:/storage/root/root/lib/root:/storage/root/root/lib/root:/storage/root/root/lib/root:/storage/root/root/lib/root:/storage/root/root/lib/root:/storage/root/root/lib/root:/storage/root/root/lib/root:/storage/root/root/lib/root:/storage/root/root/lib/root:/storage/root/root/lib/root:/storage/root/root/lib/root:/storage/root/root/lib/root:.:/storage/root/root/lib/root::/storage/root/root/lib/root/cint/cint/stl
>>>>
>>>>
>>>> [where /storage/root/root is ROOT installation directory ]
>>>>
>>>> It seems that now the program knows that it has to open a file stored in
>>>> HDFS, even though it can't do it succesfully. Any hint on how to fix
>>>> that new issue?
>>>>
>>>> Cheers,
>>>> Massimiliano
>>>>
>>>> Fons Rademakers <Fons.Rademakers_at_cern.ch> ha scritto:
>>>>
>>>>> Hi,
>>>>>
>>>>> to any I/O plugin work you have to open the files via TFile::Open(), like
>>>>>
>>>>> TFile* fileInput = TFile::Open(line.c_str());
>>>>>
>>>>> this static method will load the HDFS plugin triggered by hdfs:// an
>>>>> will return a TFile derived THDFSFile object. The way you were doing it
>>>>> you were getting a standard local TFile object that was trying to open
>>>>> a local file.
>>>>>
>>>>> Let me know if you've more success with TFile::Open().
>>>>>
>>>>> Cheers, Fons.
>>>>>
>>>>
>>>>
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>>>>
>>>>
>>>
>>
>>
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>>
>
> --
> Org: CERN, European Laboratory for Particle Physics.
> Mail: 1211 Geneve 23, Switzerland
> E-Mail: Fons.Rademakers_at_cern.ch Phone: +41 22 7679248
> WWW: http://fons.rademakers.org Fax: +41 22 7669640
>
>

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This message was sent using IMP, the INFN Perugia Internet Messaging Program. Received on Mon Apr 23 2012 - 11:07:10 CEST