Incorrect link in the homework result email

[alexeygrigorev]

Hey Alexey pretty cool the auto email saying the results. 🙂
[11:26 PM]However the links are wrong.
Luis Oliveira  [11:13 AM]
It is sending to -> http:///llm-zoomcamp-2026/leaderboard instead of https://courses.datatalks.club/llm-zoomcamp-2026/leaderboard

[alexeygrigorev]

Root cause found + code fix shipped

The broken link (http:///llm-zoomcamp-2026/leaderboard — a URL with a scheme but no host) was traced to how notification emails build links.

Score/peer-review/project notification emails are built without an HTTP request, so public_url() relied entirely on PUBLIC_BASE_URL. When that setting was empty or hostless, it emitted a hostless link (/path or http:///path), and Datamailer correctly left it untouched because its click-tracking skips URLs with no host — so the broken link reached the inbox verbatim. (In-app confirmation emails were unaffected because they have a request and fall back to the request host.)

Fixed in code (commit 19b82f2): public_url() now guarantees an absolute URL with a real host, falling back to a concrete ALLOWED_HOSTS entry (or https://courses.datatalks.club) and logging a warning if PUBLIC_BASE_URL is unset/hostless. PUBLIC_BASE_URL is also now whitespace-stripped at settings load. Added courses/tests/test_datamailer_public_url.py reproducing the exact http:///… symptom.

What should happen next (infra)

The code fix is a safety net so emails can never again contain a hostless link — but the underlying cause is an environment misconfiguration: the environment that sends these notifications had PUBLIC_BASE_URL unset or malformed.

• Verify PUBLIC_BASE_URL is set to https://courses.datatalks.club in the prod sending environment (and https://dev.courses.datatalks.club on dev), with no trailing whitespace/newline.
• Confirm the value is present in whatever process actually sends score notifications (web task and/or the scheduled deadline-reminder ECS task).
• After correcting the env, links will use the real host directly instead of the fallback; watch logs for the PUBLIC_BASE_URL … has no scheme/host warning to confirm the fallback is no longer being hit.

Tagging infra because the remaining action is an environment/deploy config change, not app code.