School of Computing Web Grader Interface

Chris Bourke
[email protected]

Webgrader is a web-based front end that allows you to expose grading scripts for assignments handed in through the School of Computing's webhandin https://cse.unl.edu/handin) system. It allows students and graders to execute scripts (that you write) using their Canvas (Active Directory, AD) login credentials.

A short tutorial video has been made available: https://www.youtube.com/watch?v=CRvXsOfp1Vo

Note: the tutorial video uses CSE login credentials, you will instead use your AD credentials

Setup & Installation

These setup instructions assume that you are using the handin and grader system using a class account on the cse-linux-01.unl.edu server. Class accounts begin with a c- prefix to your faculty MyRed login (ex: c-cbourke3) and will have a different password not managed by Active Directory. To request an account contact the SoC System Admins. Alternatively, you can host the grader on your own (MyRed/AD) account, but it will require extra configuration changes that are not documented here.

1. Change the permissions on your root directory to enable apache to read it:
   chmod 711 ~

2. Edit your ~/.profile file to set the default umask to 0022 by adding the following line:
   umask 0022

3. Setup the public_html directory. Since multiple courses may be hosted at once, you'll need to do this for each course and distinguish them using the CLASS directory name (which can be any valid directory name, example: CSCE156). Execute the following commands.

   Create the public_html directory and move into it:

   mkdir public_html
   cd public_html

   Create the directory for your CLASS and move into it:

   mkdir CLASS
   cd CLASS

   Clone the grader app:

   git clone https://github.com/cbourke/grade/

Configuration

1. Be sure to setup all assignments and TAs (graders) in the SoC handin system and sync these with the grader. This will automatically create the following files in the handin directory (~handin/CLASS).

   • homework - a formatted list of assignments and due dates
   • mail.list - a full roster (instructors, graders, students)
   • gta-mail.list a list of instructors and graders

2. Edit the grade/include/Config.php file and specify the 3 required items as indicated in the file.

3. Setup your grading scripts. By default, the grader app expects that there is a grading script called grade.php in each CLASS/ASSIGNMENT subdirectory. For example, for and assignment with a label of 3, it would expect there to be an executable script in ~/handin/CLASS/3/grade.php.
   If such a file does not exist, the page will work but users will not be able to select that assignment to be graded. Additionally:

   • The grader interface expects a different executable named grade.team.php (so you can run a different script if you want through the grader interface).
   • The scripts must be executable (chmod 700)
   • The script can be any shell executable, but it will be execute without the user's environment setup. Therefore, you may need to write the script to establish environmental variables if you need them (examples: source an rc file, or use absolute paths for external programs such as compilers, etc.).
   • All output, (stdout and stderr) is output to the user, so beware, it is recommended that the script produce well-formatted HTML.
   • The name of the grade script is configurable in the includes/Config.php file. This is particularly useful if you use a different language (grade.py)

Usage

1. Inform your students that they can submit files through the handin system:
   https://cse-apps.unl.edu/handin
   And that they can grade through the grader app:
   https://cse-linux-01.unl.edu/~classAcct/CLASS/grade/
   A concrete example:
   https://cse-linux-01.unl.edu/~c-cbourke3/CSCE155E/grade/

2. Inform your graders that they can grade students through the grader interface:
   https://cse-linux-01.unl.edu/~c-cbourke3/CSCE155E/grade/grader.php
   They can also turn in files and grade themselves to troubleshoot code and grading scripts.

Other Items

• The webhandin will automatically sync files that students submit to the cse-linux-01.unl.edu file system where webgrader is running. These are copies and the originals are stored in the webhandin's database. You can modify these files but take care as doing so will leave them out of sync with the originals stored by webhandin.

• Because limits have been placed on processes launched through apache, when grading Java programs, you may need to throttle the JVM to use no more than 2GB of memory when launched. To do this, instead of the usual java command, you would use:
  java -Xmx2048m ...
  The same limitation would need to be there for the Java compiler:
  javac -J-Xmx2048m ...

• An example grading script written in PHP has been provided (see /examples) that can be used to design a testing suite including pre- and post- test commands.