Grid Exercise 1: Refresher – Submitting Multiple Jobs

The goal of this exercise is to map the physical locations of some worker servers 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.

Geolocating several servers

Now, let’s try to remember some basic HTCondor ideas from the HTC exercises:

  1. Log in to learn.chtc.wisc.edu
  2. Create and change into a new folder for this exercise, for example grid-ex1

  3. Download the geolocation code:

    user@learn $ wget http://proxy.chtc.wisc.edu/SQUID/osgschool20/location-wrapper.sh \
             http://proxy.chtc.wisc.edu/SQUID/osgschool20/wn-geoip.tar.gz

    You will be using location-wrapper.sh as your executable and wn-geoip.tar.gz as an input file.

  4. Create a submit file that generates fifty jobs that run location-wrapper.sh, transfers wn-geoip.tar.gz as an input file, and uses the $(Process) macro to write different output and error files. Also, add the following requirement to the submit file (it's not important to know what it does):

    Requirements = (HAS_CVMFS_oasis_opensciencegrid_org =?= TRUE)

    Try to do this step without looking at materials from the earlier exercises. But if you are stuck, see HTC Exercise 2.2.

  5. 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:

user@learn $ cat location-*.out

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 combination with the sort and uniq commands using "pipes" (|) to print only the unique results:

user@learn $ cat location-*.out | sort | uniq

Mapping your results

To visualize the locations of the servers 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. Where did your jobs run?

Next exercise

Once completed, move onto the next exercise: Logging in to the OSG submit server