QTY-18984: Fix NoMethodError in touch_courses when Redis returns nil #494
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Add defensive coding to handle cases where redis.smembers() returns nil instead of an empty array, which was causing NoMethodError in production (cdcr.strongmind.com only). Changes: - Add nil coalescing (|| []) to handle nil from smembers - Add nil check for Course.find_by_id to handle deleted courses - Wrap Redis operations in begin/rescue for Redis::BaseError - Log warnings for stale course references - Log errors and report to Sentry for Redis connection issues Fixes CANVAS-LMS-2WJ Co-authored-by: Cursor <cursoragent@cursor.com>
Redis gem is not available in canvas_shim test environment since it's provided by the host Canvas application. Add stub classes to allow tests to run in CI. Co-authored-by: Cursor <cursoragent@cursor.com>
- Extract process_course_touch method for pure logic testing - Separate Redis dependency from business logic - Add unit tests without Rails dependency
Lendolan
approved these changes
Jan 30, 2026
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Link to Jira ticket
Purpose
Fix
NoMethodError: undefined method 'each' for nil:NilClassthat occurs whenredis.smembers()returnsnilinstead of an empty array in thetouch_coursesmethod.This error has been occurring every 10 minutes since 2026-01-29T17:42 on
cdcr.strongmind.comonly, with 36+ occurrences. The periodic job "Ten minute course touch" fails when Redis connectivity issues causesmembersto return nil.Related Sentry issue: CANVAS-LMS-2WJ
Approach
Add defensive coding to handle Redis edge cases:
redis.smembers(key) || []to handle nil responsesCourse.find_by_id(member)with nil guard to handle deleted coursesrescue Redis::BaseErrorto catch connection errors gracefullyTesting
Added comprehensive unit tests covering:
redis.smembersreturnsnil(the bug scenario)redis.smembersreturns empty arrayRun tests:
bundle exec rspec spec/decorators/models/course_decorator_spec.rbInfrastructure Note
The error only affects
cdcr.strongmind.comand no cdcr-specific Redis cluster was found in AWS ElastiCache monitoring. Please verify:REDIS_SERVERenv var value for cdcr?Screenshots/Video
N/A - Backend fix, no UI changes.