Wednesday Exercise 2.3: Using Docker¶

In this exercise, you will run the same Python script as the previous exercises, but using a Docker container.

Setup¶

For this exercise, you will need to be logged into learn.chtc.wisc.edu, not training.osgconnect.net.

Make a copy of your submit file from the previous Python exercise.
Add the following lines to the submit file or modify existing lines to match the lines below:
```
universe = docker
docker_image = python:3.7.0-stretch
```
Here we are requesting HTCondor's Docker universe and using a pre-built python image that, by default, will be pulled from a public website of Docker images called DockerHub. The requirements line will ensure that we run on computers whose operating system can support Docker.
Adjust the executable and arguments lines. The executable can now be the Python script itself, with the appropriate arguments:
```
executable = fib.py
arguments = 90
```
Finally, we no longer need to transfer a Python tarball (whether source code or pre-built) or our Python script. You can remove both from the transfer_input_files line of the submit file.

Open the Python script and add the following line at the top:
```
#!/usr/bin/env python3
```
This will ensure that the script uses the version of Python that comes in the Docker container.

Once these steps are done, submit the job.