Stop fetching full quiz attempt review just to read the grade - #177
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VATUSAMoodle::getQuizAttempts() called Moodle's mod_quiz_get_attempt_review
web service once per attempt to read a single field (grade), but that
endpoint returns the entire rendered attempt review — every question, every
response, ~2.17 MB — per call. Driven by scheduled jobs in the api repo
(moodle:competency every 10 min, moodle:sendexamemails every 5 min) that
share this identical class, this amounted to ~33,000 calls/day and ~2
TB/month of outbound traffic from academy.vatusa.net, ~98.6% of that
droplet's total egress (see the migration cost analysis that surfaced this).
The review's grade is just quiz_rescale_grade(sumgrades, quiz) =
round(sumgrades / quiz.sumgrades * quiz.grade), and both sumgrades (per
attempt) and quiz.sumgrades/quiz.grade (per quiz) already live in the
Moodle database this class already queries via DB::connection('moodle')
for other fields. Compute the grade from there instead, batched per call
and memoized per quiz for the life of the instance — no behavior change
for any consumer, just no more multi-megabyte HTTP round-trips.
Mirrors the same fix landing in vatusa/api (VATUSAMoodle.php is duplicated
across both repos). Verified in Docker against a fixture 'moodle' database
using api's identical class: grades match the old review-derived formula
exactly for both 1:1 and scaled quizzes, fail-closed behavior on missing
data is preserved, and no calls to mod_quiz_get_attempt_review occur.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
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Summary
VATUSAMoodle::getQuizAttempts()(duplicated identically invatusa/api) called Moodle'smod_quiz_get_attempt_reviewweb service once per attempt to read a single field (grade) — but that endpoint returns the entire rendered attempt review (every question, every response, ~2.17 MB) per call.api(moodle:competencyevery 10 min,moodle:sendexamemailsevery 5 min) that share this class, this amounted to ~33,000 calls/day and ~2 TB/month of outbound traffic fromacademy.vatusa.net— ~98.6% of that droplet's total egress. This was surfaced while costing out an Azure migration: the bill for that traffic alone (~$193/mo on metered Azure egress) would exceed the entire nonprofit grant.gradeis justquiz_rescale_grade(sumgrades, quiz)=round(sumgrades / quiz.sumgrades * quiz.grade). Bothsumgrades(per attempt, inmdl_quiz_attempts) andquiz.sumgrades/quiz.grade(per quiz, inmdl_quiz) already live in the Moodle database this class already queries viaDB::connection('moodle')for other fields — no need to go over HTTP at all.getQuizMeta()helper (memoized per quiz id for the life of the instance) plus a single batchedwhereInquery for attemptsumgrades, replacing the per-attempt review call ingetQuizAttempts().[]on missing/unresolvable data.vatusa/api, which also fixes a second, independent call site there and has a note on a Docker dev-environment quirk found along the way: Stop fetching full quiz attempt review just to read the grade api#118Test plan
moodledatabase usingapi's identical class (this repo has no local Docker dev harness of its own —current's only compose file is the production build, per itsCLAUDE.md): grades match the old review-derived formula exactly for both 1:1 and non-trivially-scaled quizzes,getQuizMeta()memoization confirmed, fail-closed behavior preserved for a missing attempt and an unknown quiz id. The change here is identical to the verifiedapichange.php -lsyntax check passes. (current's Composer deps aren't installed in this environment, sophpunitcouldn't be run locally here —api's identical suite passed 18/18.)mod_quiz_get_attempt_reviewcall volume inacademy.vatusa.net's Apache access log drops to ~0, and outbound bandwidth drops toward the ~300 GB/month baseline of genuine site traffic.🤖 Generated with Claude Code