Common Grading Failures & Recovery¶

Most grading failures have one of about six causes. This page is arranged by symptom.

Validation & Metadata Errors¶

Symptom. A student cannot validate; the notebook reports that the source of the following cell has changed; a submission cannot be autograded because its metadata is corrupt; or validation fails with a message about a required field.

Cause. A read-only cell or an autograded cell was copied, edited or deleted. nbgrader restores read-only cells from the original, and copies of them break the mapping between the notebook and the assignment. This is an upstream nbgrader behaviour, not a platform fault, and there is no fix on our side.

Recovery, done by the student:

1. Rename the existing notebook, adding -corrupted to the filename, and download a copy as a fallback.
2. Re-fetch the assignment from the assignment list. Both copies are now in their files.
3. Open both, and copy the answers across into the fresh notebook.
4. Re-submit.

Then, as grader: re-collect the assignment in Formgrader.

Prevention. Please do not ask students to copy cells the course provided, and state plainly in the assignment that adding cells is fine but duplicating the given ones is not. → The Notebook Grading Workflow

Export Failures¶

Symptom. nbgrader export fails, typically at the end of the term.

Two known causes, both about how an assignment was named or removed:

• A space in the assignment title. Name assignments without spaces.
• An assignment deleted through the filesystem rather than with nbgrader db assignment remove, leaving the database and the directories disagreeing.

Recovery. Delete the assignment properly and run the export again. → Exporting the Grades

The Grader Environment Itself¶

"Database locked". From a terminal in the course environment:

rm ~/.local/share/jupyter/nbsignatures.db

Close the terminal, stop the server with File → Hub Control Panel → Stop My Server, and start it again.

Old courses cluttering the assignment list. nbgrader caches previously used courses:

cd ~/.local/share/jupyter/nbgrader_cache
ls -al
rm -r <old_course_directory>

A broken grader environment after a package install. Clearing .local and running the manual resetter are the standard fixes for an individual account, but the shared grader account holds the course's nbgrader state, and clearing it by hand can take grading with it. Raise it in the course support ticket instead. → Customizing an Environment

Missing Submissions & Missing Students¶

A student is not in Manage Students. Students appear only once they have submitted something, and then by username alone. Names have to be imported separately. → The Notebook Grading Workflow

A student says they submitted and nothing was collected. Three things to confirm with them: that they clicked Submit rather than only saving; that the assignment appears in their list of submitted assignments; and that they are looking at the same assignment that was collected. Repeat submissions are fine — only the most recent one is available to course staff, including a late one.

An assignment cannot be manually graded. It has not been autograded yet. Every assignment must go through the autograder first, including one with no autograded cells in it at all.

Large files did not come through. There is a default cap on assignment file size. Raising it means changing the nbgrader configuration in the course environment — please ask us rather than editing it blind.

Nothing Is Where the Documentation Says¶

No Formgrader menu. Two causes, in order of likelihood:

• The wrong account. nbgrader works only from the shared course grader account, never from an instructor's or TA's own account.
• The wrong interface. NBClassic does not carry the nbgrader extension. → Which Interface Supports Grading

A distribution link does nothing. A git-pull link clicked before signing in fails silently. Sign in at datahub.ucsd.edu first, then click the link again. → Datahub in the Browser

An assignment name is rejected as a duplicate. nbgrader requires assignment names to be unique across every assignment the grader account has created, not just within one course.

When to Open a Ticket¶

Instructors and TAs: anything touching the shared grader account, the course database, or a deadline. Incidents at a critical point in the term are handled with more urgency than routine requests — please say so in the ticket. → Getting Help

Students: please go to the course instructor or TA first. They can reproduce the problem and escalate it to us with the course context attached.

If you still have questions or need additional assistance, email us at datahub@ucsd.edu or submit a ticket to the ITS Service Desk.

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