feat: auto-detect unreachable base URL at onboarding and persist working variant as overrideBaseURL

[tkotthakota-adobe]

https://jira.corp.adobe.com/browse/SITES-46284

Problem and Fix:

When a site like dupont.com is onboarded with an unreachable base URL, the platform had no way to detect this at registration time. Every subsequent audit would silently fail trying to reach an unreachable domain. The fix adds a reachability probe at site creation — if the registered base URL fails but the www-toggled variant responds, it automatically saves the working URL as overrideBaseURL in the site config so all future audits use the correct domain from
the start.

[codecov]

Codecov Report

❌ Patch coverage is 98.94737% with 1 line in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/support/base-url-detection.js	98.88%	1 Missing ⚠️

📢 Thoughts on this report? Let us know!

[MysticatBot]

Hey @tkotthakota-adobe,

Verdict: Request changes - concurrent fire-and-forget saves create a race condition that can silently drop config mutations.
Changes: adds a reachability probe at site creation to auto-detect and persist a working www-toggled overrideBaseURL when the registered base URL is unreachable (3 files).

Must fix before merge

1. [Important] Race condition between concurrent fire-and-forget saves - src/controllers/sites.js:406 (details inline)

Non-blocking (3): minor issues and suggestions

• nit: isUrlReachable returns true for any HTTP response including 4xx/5xx - the intent is to detect "no listener", so this is arguably correct, but checking response.ok would avoid setting overrideBaseURL on domains that respond with parking pages or blanket 403s - src/support/rum-config-service.js:82
• suggestion: Extract protocol from original baseURL instead of hardcoding https:// when constructing toggledURL, so the probe works correctly for sites registered with http:// - src/support/rum-config-service.js:118
• suggestion: autoDetectOverrideBaseURL has no relationship to RUM configuration - consider moving to its own module (e.g., src/support/base-url-detection.js) for discoverability - src/support/rum-config-service.js:92

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_{Skill: pr-review | Model: us.anthropic.claude-opus-4-6-v1[1m] | Duration: 1m 24s | Cost: $3.88 | Commit: fb8f043a3ee3af29f38c6d9982f43a21be1b28fa
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[github-actions]

This PR will trigger no release when merged.

[MysticatBot]

Hey @tkotthakota-adobe,

Verdict: Comment - all prior findings addressed, no blocking issues remain.
Changes: adds a reachability probe at site creation to auto-detect and persist a working www-toggled overrideBaseURL when the registered base URL is unreachable (4 files).

Non-blocking (3): minor issues and suggestions

• nit: Missing test for malformed baseURL path (the 1 line codecov flags) - a test passing e.g. 'not-a-url' as baseURL would cover the catch at line 61 trivially - src/support/base-url-detection.js:61
• nit: Test "no-ops when baseURL returns non-ok response" asserts calledTwice but does not assert site.save was NOT called - worth adding for parity with the other no-op tests - test/support/base-url-detection.test.js:223
• suggestion: toggledURL is constructed as ${protocol}//${toggledHostname}, dropping any path from the original baseURL - if a site is registered with a path (e.g. https://www.example.com/site), the probe tests bare domain instead - likely intentional given the domain-level nature of the check, but worth a one-line comment confirming the design choice - src/support/base-url-detection.js:76

Previously flagged, now resolved

• Race condition between concurrent fire-and-forget saves - now chained sequentially via .then()
• isUrlReachable accepted any HTTP response as reachable - now gates on response.ok
• Hardcoded https:// when constructing toggled URL - now extracts protocol from original baseURL
• Auto-detect logic co-located in rum-config-service - extracted to dedicated base-url-detection.js module

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_{Skill: pr-review | Model: us.anthropic.claude-opus-4-6-v1[1m] | Duration: 0m 53s | Cost: $2.63 | Commit: 6ee2c66b3ec0e7b6e7d3ba62a49fbc5b69a7cc4c
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