fix: fixed rerun operation when the course is too large

[Asespinel]

Description

This PR implements retry logic with exponential backoff to handle course re-run operations for large courses. When a course is re-run, the backend needs time to process and create the new course structure, which can result in temporary 404 or 202 responses. This change ensures the frontend waits appropriately instead of immediately showing "Not Found" errors.

Problem

When performing a re-run operation on large courses, the following issues occurred:

1. Immediate 404 errors: The frontend would immediately show "Not Found" after a re-run, even though the course was being processed
2. Inconsistent state: fetchCourseDetail would succeed but fetchCourseOutlineIndex would fail, leading to undefined properties (e.g., isEnabled)
3. Poor user experience: Users had to manually refresh the page multiple times or wait with the page open until the course was ready

Solution

Implemented a retryOnNotReady helper function with exponential backoff that:

• Retries API calls when receiving 202 (Accepted) status codes (course still processing)
• Retries when receiving course_does_not_exist errors during the initial attempts
• Uses exponential backoff (2s → 3s → 4.5s → 6.75s → ...)
• Maximum of 10 retry attempts over approximately 60 seconds

Technical Details

Retry Logic

async function retryOnNotReady(
  apiCall: () => Promise,
  maxRetries: number = 10,
  initialDelay: number = 2000,
  backoffMultiplier: number = 1.5
): Promise

Parameters:

• maxRetries: Maximum number of retry attempts (default: 10)
• initialDelay: Initial delay in milliseconds (default: 2000ms)
• backoffMultiplier: Multiplier for exponential backoff (default: 1.5)

Retry Conditions:

• HTTP 202 (Accepted) - Backend explicitly indicates processing
• course_does_not_exist error during first 5 attempts
• Any other error immediately throws without retry

Why Exponential Backoff?

Large courses can take 30-60 seconds to process. Exponential backoff:

• Reduces server load by spacing out requests
• Adapts to different course sizes automatically
• Provides better user experience than fixed intervals

Testing

Manual Testing Steps

1. Create or select a large course (100+ units)
2. Perform a re-run operation
3. Verify the course loads successfully without "Not Found" errors

[openedx-webhooks]

Thanks for the pull request, @Asespinel!

This repository is currently maintained by @bradenmacdonald.

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[codecov]

Codecov Report

❌ Patch coverage is 90.00000% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 94.77%. Comparing base (5ce61fa) to head (5d64fb2).
⚠️ Report is 10 commits behind head on master.

Files with missing lines	Patch %	Lines
src/course-outline/data/thunk.ts	78.57%	3 Missing ⚠️
src/data/thunks.ts	96.15%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2581      +/-   ##
==========================================
+ Coverage   94.74%   94.77%   +0.02%     
==========================================
  Files        1218     1225       +7     
  Lines       27299    27432     +133     
  Branches     5983     6184     +201     
==========================================
+ Hits        25865    25998     +133     
+ Misses       1376     1363      -13     
- Partials       58       71      +13     

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[bradenmacdonald]

Thanks for this contribution. Let me know when it's ready for review.

I see you implemented custom retry logic; in the long term, we'd like to migrate all data loading to React Query, which provides retry logic already. Did/could you consider updating this to use React Query, so we can use its retry logic?

Does this code to retry with backoff only when the course is new/rerun / seems to exist but has no outline yet, or does it always retry the outline no matter what?

Also, did you use any AI tools when creating this code? If so, please mention that in the PR description.