fix(theme): serialize Polylang group linking in AI media translation#150
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The "Translate All" button on the media/post edit screen fans out one concurrent AJAX request per language (Promise.all), and each request did a non-atomic read-modify-write of the shared Polylang post_translations term (read source group -> add this language -> save). Served by parallel PHP-FPM workers, the requests lost-update each other's group term, leaving one or two languages orphaned in a stale term — the translation-group asymmetry seen on imported team-member photos (IT/FR for one author, IT for another; the orphaned language varied by timing). Wrap only the linking critical section in a MySQL GET_LOCK advisory lock keyed on the source group id. The concurrent requests now queue for the ~millisecond link, then run their expensive OpenAI translations fully in parallel — so the speedup that motivated concurrency is preserved (unlike a client-side sequential fix, which would serialize the slow OpenAI calls too). Lock acquisition is best-effort: if $wpdb is unavailable or the lock times out, linking still proceeds rather than failing the translation. The MCP/queue create-* handlers were never affected: they build the full translations array and save it once, sequentially, in a single request. Tests: assert the lock is acquired+released keyed on the source id and the group is saved with source+target merged; plus a degraded-path test (no $wpdb) confirming linking still completes. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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📝 WalkthroughWalkthroughThe PR adds MySQL advisory lock serialization to Polylang translation-group linking in the AJAX autocreate flow. A new ChangesPolylang translation linking serialization
Sequence DiagramsequenceDiagram
participant Handler as cdcf_ajax_ai_translate
participant Locker as cdcf_ai_translate_link_under_lock
participant MySQL as Database (wpdb)
participant Polylang as Polylang API
Handler->>Locker: cdcf_ai_translate_link_under_lock(source_id, target_lang, post_id)
Locker->>MySQL: GET_LOCK(cdcf_pll_link_*source_id, timeout)
alt Lock acquired
MySQL-->>Locker: lock_acquired = true
Locker->>Polylang: pll_set_post_language(post_id, target_lang)
Locker->>Polylang: read post_translations
Locker->>Polylang: merge new translation into group
Locker->>Polylang: pll_save_post_translations(merged_translations)
Locker->>MySQL: RELEASE_LOCK(cdcf_pll_link_*source_id)
MySQL-->>Locker: released
else Lock unavailable
MySQL-->>Locker: lock_acquired = false
Locker->>Polylang: pll_set_post_language(post_id, target_lang)
Locker->>Polylang: read post_translations
Locker->>Polylang: merge new translation into group
Locker->>Polylang: pll_save_post_translations(merged_translations)
end
Locker-->>Handler: void
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✅ Passed checks (4 passed)
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Up to standards ✅🟢 Issues
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| Metric | Results |
|---|---|
| Complexity | 6 |
| Duplication | 0 |
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Actionable comments posted: 1
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Verify each finding against current code. Fix only still-valid issues, skip the
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Inline comments:
In `@wordpress/themes/cdcf-headless/includes/admin/ai-translate.php`:
- Around line 44-50: The Polylang save/link result is ignored: after calling
pll_save_post_translations (and the surrounding
pll_set_post_language/pll_get_post_translations logic) you must check whether
the translation group was successfully saved and, if not, abort the AJAX flow;
replace the unconditional success path with a call to
cdcf_ai_translate_link_under_lock($source_id, $target_lang, (int)$post_id) (or
otherwise check the boolean return of pll_save_post_translations) and call
wp_send_json_error('Failed to link translation group.') when linking fails so
the new post is not left orphaned.
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Fix all unresolved CodeRabbit comments on this PR:
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📒 Files selected for processing (2)
wordpress/themes/cdcf-headless/includes/admin/ai-translate.phpwordpress/themes/cdcf-headless/tests/AjaxAiTranslateTest.php
Review follow-up on the linking helper: pll_save_post_translations' result
was ignored, so a real persistence failure would leave the freshly-created
translation post orphaned (created but not in any translation group) while
the AJAX flow still reported success.
cdcf_ai_translate_link_under_lock() now returns bool (false when
pll_save_post_translations returns false — the same contract used in
handlers/link-translations.php). The handler aborts on a failed link,
deleting the just-created post first so a failed attempt leaves nothing
behind, and responds wp_send_json_error('Failed to link translation group.').
Added a test for the failure path (link returns false -> orphan force-deleted
+ error). Theme suite 371 green; patch coverage 100% (the 4 uncovered lines in
the file are pre-existing and outside this diff).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
2 participants
Root cause
The translation-group asymmetry we hit on imported team-member photos (Karačić: IT+FR orphaned; Bersano Calot: IT orphaned) is a lost-update race, not an MCP issue.
Media translations run through the theme's "AI Translation" feature (edit media → Translate). The "Translate All" button fires one concurrent AJAX request per language (
functions.php,Promise.all), and the handler linked the Polylang group with a non-atomic read-modify-write of the single sharedpost_translationsterm:Served by parallel PHP-FPM workers, each request reads the group before its siblings commit, adds only its own language, and overwrites the shared term — so the later writers clobber the earlier ones and one or two languages end up split into a stale term. Timing-dependent, which is why the orphaned language differed between authors.
The MCP/queue
create-*handlers are immune: they build the full translations array and save it once, sequentially, in a single request.Fix
Wrap only the linking critical section in a MySQL
GET_LOCK()advisory lock keyed on the source group id (cdcf_pll_link_<source_id>). The concurrent requests now queue for the ~millisecond link, then run their expensive OpenAI translations fully in parallel.This deliberately keeps the concurrency: a client-side sequential fix would also serialize the slow OpenAI calls, losing the speedup that the parallel design (and the Redis workers) exist to provide. Only the cheap group-linking is serialized.
Lock acquisition is best-effort — if
$wpdbis unavailable or the lock times out (10s; the section is sub-millisecond), linking still proceeds rather than failing the translation.Tests
test_autocreate_links_group_under_a_source_keyed_lock— fake$wpdbassertsGET_LOCK/RELEASE_LOCKare called keyed on the source id, and the group is saved with source+target merged.test_autocreate_still_links_when_no_wpdb_available— degraded path still links.Note
This fixes future translations. The two already-imported authors were repaired manually (their groups are now symmetric).
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Summary by CodeRabbit
Bug Fixes
Tests