VO specific software on the Grid

Accessing software distributed via CVMFS

For most VOs the software is now being distributed via CVMFS. The only detail a user (client) has to know is how the repository(-ries) are mapped on Worker Nodes. In this article we will use the gridpp VO repository, which is mapped to /cvmfs/gridpp.egi.eu/ . A VO software administrator uploaded a following example python script and saved it as testing/hello.py :

#!/usr/bin/env python
import sys

print "----------------------"
print "Hello, I'm a snake !  /\/\/o"
print "----------------------"

print " More info:\n"

print (sys.version)

#
 

It normally takes a few hours before uploaded software becomes available to clients. Now we need to create a job wrapper (run_hello_cvmfs.sh) which will be submitted as a Dirac executable:

#!/bin/bash
#
# Run the Python script.
export GRIDPP_VO_CVMFS_ROOT=/cvmfs/gridpp.egi.eu/testing/HelloWorld
if [ -d "$GRIDPP_VO_CVMFS_ROOT" ]; then
   $GRIDPP_VO_CVMFS_ROOT/hello.py
else
   echo "Requester CVMFS directory does not exist $GRIDPP_VO_CVMFS_ROOT  "
   exit 1
fi
#

The last step is to created a Dirac jdl file (hello_cvmfs.jdl):

[
JobName = "Snake_Job_CVMFS";
Executable = "run_hello_cvmfs.sh";
Arguments = "";
StdOutput = "StdOut";
StdError = "StdErr";
InputSandbox = {"run_hello_cvmfs.sh"};
OutputSandbox = {"StdOut","StdErr"};
]

In the jdl we define the executable (run_hello_cvmfs.sh) which is shipped with the job in the input sandbox. Now we can submit our first CVMFS job:

dirac-wms-job-submit -f logfile hello_cvmfs.jdl

Check its status, which in our case returned:

dirac-wms-job-status -f logfile
JobID=5213546 Status=Running; MinorStatus=Job Initialization; Site=VAC.UKI-LT2-RHUL.uk;
<nowiki>

When job finishes, we can grab the output (<code>dirac-wms-job-get-output -f logfile</code>), which reads:

 <nowiki>
----------------------
Hello, I'm a snake !  /\/\/o
----------------------
 More info:

2.7.12 (default, Dec 17 2016, 21:07:48) 
[GCC 4.4.7 20120313 (Red Hat 4.4.7-17)]