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From Marcos Ortiz <mlor...@uci.cu>
Subject Re: Error while using libhdfs C API
Date Fri, 09 Mar 2012 14:12:41 GMT


On 03/09/2012 07:34 AM, Amritanshu Shekhar wrote:
>
> Hi Marcos,
>
> Figured out the compilation issue. It was due to error.h header file 
> which was not used and not present in the distribution.  There is one 
> small issue however I was trying to test hdfs read. I copied an input 
> file to /user/inputData(this can be listed using bin/hadoop dfs  -ls 
>  /user/inputData).  hdfsExists call  fails for this directory however 
> it works when I copy my file  to /tmp.  Is it because hdfs only 
> recognizes /tmp as a valid dir?  Thus I was wondering  what directory 
> structure does hdfs recognize by default and if we can override it 
> through a conf variable what would that variable be and where to set it?
>
> Thanks,
>
> Amritanshu
>
Awesome, Amritanshu. CC to hdfs-user@hadoop.apache.org
Please, give some logs about your work with the compilation.
How did you solve this? To have it on the mailing list archives.

About your another issue,
1- Did you check that the $HADOOP_USER has access to /user/inputData?

HDFS:
           It recognize the directory that you entered on the 
hdfs-site.xml on the dfs.name.dir(NN) property and on the dfs.data.dir 
(DN), but by default, it works with /tmp directory (not recommended in 
production). Look on the Eugene Ciurana´s Refcard called "Deploying 
Hadoop", where he did a amazing work explaining in a few pages some 
tricky configurations tips.

Regards

> *From:*Marcos Ortiz [mailto:mlortiz@uci.cu]
> *Sent:* Wednesday, March 07, 2012 7:36 PM
> *To:* Amritanshu Shekhar
> *Subject:* Re: Error while using libhdfs C API
>
>
>
> On 03/07/2012 01:15 AM, Amritanshu Shekhar wrote:
>
> Hi Marcos,
>
> Thanks for the quick reply. Actually I am using a gmake build system 
> where the library is being linked as a static library(.a ) rather than 
> a shared object.  It seems strange since stderr is a standard symbol 
> which should be resolved.  Currently I am using the version that came 
> with the distribution($HOME/c++/Linux-amd64-64/lib/libhdfs.a) . I 
> tried building the library from the source but there were build 
> dependencies that could not be resolved. I tried building 
> $HOME/hadoop/hdfs/src/c++/libhdfs by running:
>
> ./configure
>
> ./make
>
> I got a lot of dependency errors so gave up the effort.  If you happen 
> to have a working application that make suse of libhdfs please let me 
> know. Any inputs would be welcome as I have hit a roadblock as far as 
> libhdfs is concerned.
>
> Thanks,
>
> Amritanshu
>
> No, Amritansu. I don't have any examples of the use of libhdfs API, 
> but I remembered that some folks were using it. Search on the mailing 
> list archives (http://www.search-hadoop.com).
> Can you put the errors that you had in your system when you tried to 
> compile the library?
> Regards and best wishes
>
> *From:*Marcos Ortiz [mailto:mlortiz@uci.cu]
> *Sent:* Monday, March 05, 2012 6:51 PM
> *To:* hdfs-user@hadoop.apache.org <mailto:hdfs-user@hadoop.apache.org>
> *Cc:* Amritanshu Shekhar
> *Subject:* Re: Error while using libhdfs C API
>
> Which platform are you using?
> Did you update the dynamic linker runtime bindings (ldconfig)?
>
> ldconfig $HOME/hadoop/c++/Linux-amd64/lib
> Regards
>
> On 03/06/2012 02:38 AM, Amritanshu Shekhar wrote:
>
> Hi,
>
> I was trying to link  64 bit libhdfs in my application program but it 
> seems there is an issue with this library.  Get the following error:
>
> Undefined                       first referenced
>
> symbol                             in file
>
> stderr                              libhdfs.a(hdfs.o)
>
> __errno_location                   libhdfs.a(hdfs.o)
>
> ld: fatal: Symbol referencing errors. No output written to 
> ../../bin/sun86/mapreduce
>
> collect2: ld returned 1 exit status
>
> Now I was wondering  if  this a common error and is there an actual 
> issue with the library or am I getting an error because of  an 
> incorrect configuration? I am using the following library: 
> $HOME/hadoop/c++/Linux-amd64-64/lib/libhdfs.a
>
> Thanks,
>
> Amritanshu
>
>
> Image removed by sender.
> <http://www.antiterroristas.cu/>
>
>
>
>
> -- 
> Marcos Luis Ortíz Valmaseda
>   Sr. Software Engineer (UCI)
>   http://marcosluis2186.posterous.com
>   http://postgresql.uci.cu/blog/38   
>
> Image removed by sender. <http://www.antiterroristas.cu/>
>
>
>
> <http://www.antiterroristas.cu/>
>
>
>
> -- 
> Marcos Luis Ortíz Valmaseda
>   Sr. Software Engineer (UCI)
>   http://marcosluis2186.posterous.com
>   http://postgresql.uci.cu/blog/38   
>
> <http://www.antiterroristas.cu/>
>
>
>
> <http://www.antiterroristas.cu/>

-- 
Marcos Luis Ortíz Valmaseda
  Sr. Software Engineer (UCI)
  http://marcosluis2186.posterous.com
  http://postgresql.uci.cu/blog/38




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