Tuesday Exercise 1.1: Refresher – Submitting Multiple Jobs

The goal of this exercise is to map the physical locations of some worker nodes in our local cluster. To do this, you will write a simple submit file that will queue multiple jobs and then manually collate the results.

Where in the world are my jobs?

To find the physical location of the computers your jobs our running on, you will use a method called geolocation. Geolocation uses a registry to match a computer’s network address to an approximate latitude and longitude.

Geolocation code

Below is a Python script that geolocates the machine that it is running on, returning latitude and longitude coordinates. It is not important to understand how the internals of the script works.

#!/bin/env python

import sys
import socket
import urllib2
import json
import time

hostnames = set()
if len(sys.argv) == 1:
    for filename in sys.argv[1:]:
            with open(filename, 'r') as f:
                hostnames.update(set([x.strip() for x in f.readlines()]))
        except IOError:

for host in hostnames:
        ipaddr = socket.gethostbyname(host)
        for i in range(1,4):
                response = urllib2.urlopen('http://www.freegeoip.net/json/' + ipaddr).read()
                json_response = json.loads(response)
                lat = json_response['latitude']
                lon = json_response['longitude']

                if int(lat) is 0 and int(lon) is 0:
                    exit("www.freegeoip.net could not find associated lat/lon coordinates.")
                print "%s,%s" % (lat, lon)
            except urllib2.HTTPError:
    except socket.gaierror:

When called without any arguments, the above script will return the latitude and longitude coordinates of the machine that it is run on.

Geolocating several machines

Now, let’s try to use this Python script and remember some basic HTCondor ideas from yesterday!

  1. Log on to learn.chtc.wisc.edu
  2. Create and change into a new folder for this exercise, for example tuesday-1.1
  3. Save the Python script above as a file named location.py
  4. As always, ensure that your script has the proper permissions (hint: try running it from the command line)
  5. Create a submit file that generates ten jobs that run location.py and uses the $(Process) macro to write different output and error files. Try to do this step without looking at materials from yesterday. But if you are stuck, see yesterday’s exercise 2.4.
  6. Submit your jobs and wait for the results

Collating your results

Now that you have your results, it's time to summarize them. Rather than inspecting each output file individually, you can use the cat command to print the results from all of your output files at once. If all of your output files have the format location-#.out (e.g., location-10.out), your command will look something like this:

%UCL_PROMPT_SHORT% <strong>cat location-*.out</strong>

The * is a wildcard so the above cat command runs on all files that start with location- and end in .out. Additionally, you can use cat in tandem with the sort and uniq commands to print only the unique results:

%UCL_PROMPT_SHORT% <strong>cat location-*.out | sort | uniq</strong>

Mapping your results

To visualize the locations of the machines that your jobs ran on, you will be using http://www.mapcustomizer.com/. Copy and paste the collated results into the text box that pops up when clicking on the 'Bulk Entry' button on the right-hand side. Are the results what you expected?

Next exercise

Once completed, move onto the next exercise: Logging in to the OSG Submit Machine