Enforce transient deletion and creation in options table when using external object cache. by Hug0-Drelon · Pull Request #1653 · polylang/polylang

Hug0-Drelon · 2025-04-08T17:57:47Z

What?

Partially fixes #2125.

How?

Ensure pll_languages_list transient is deleted from options table even if external object cache is used.
- In usual process thanks to delete_transient_pll_languages_list hook with new method in Languages model.
- In upgrade or uninstallation by calling related core functions.
Add a PHPUnit test to cover the issue, introducing wpsyntex/object-cache-annihilator as dev dependency.

Note

Similar work must be done in Polylang Pro for pll_translated_slugs transient.

…_languages_list transient.

…ll_languages_list transient with PHPUnit tests.

…aches().

include/Model/Languages.php

tests/phpunit/data/object-cache-annihilator.php

tests/phpunit/tests/test-object-cache.php

…need to call it then.

…and prod code.

… the same instance of PLL_Model to avoid breaking global scope for other tests, do not clean cache to hard between actions, and call languages->set_ready() to allow Polylang to cache languages.

Co-authored-by: Grégory Viguier <[email protected]>

tests/phpunit/tests/test-object-cache.php

Co-authored-by: Grégory Viguier <[email protected]>

include/Model/Languages.php

Chouby · 2025-04-14T12:19:55Z

include/Model/Languages.php

+	public function set_transient_to_options_table( $value ): void {
+		if ( wp_using_ext_object_cache() || wp_installing() ) {
+			add_option( '_transient_' . self::TRANSIENT_NAME, $value, '', true );
+		}
+	}


Is it useful? I we previously deleted the transient and at some point the external is not used, the option will be automatically re-created. Am I wrong?

~~As discussed during our meeting, this is safer to avoid race conditions between cache and DB.~~

We eventually chose to relay only on transient deletion to keep the DB up to date.

So I removed set_transient_to_options_table() in 9d28161.

I also ensure the test fails correctly with this change (if the fix is removed), see ad16085.

Then I took the opportunity to create a dedicated testcase in 9e46188, indeed I'm currently working on the same issue in Polylang Pro and I could use a testcase for it.

Chouby · 2025-04-14T12:20:46Z

include/model.php

+		add_action( 'delete_transient_pll_languages_list', array( $this->languages, 'delete_transient_from_options_table' ) );
+		add_action( 'set_transient_pll_languages_list', array( $this->languages, 'set_transient_to_options_table' ) );


Since you are using the constant in Languages, it would be better to use it here the action name too.

Done in a0e5313.

Chouby · 2025-04-14T12:22:07Z

install/upgrade.php

 		}

 		delete_transient( 'pll_languages_list' );
+		delete_option( '_transient_pll_languages_list' ); // Force deletion of the transient from the options table in case external object cache is used.


Why is it necessary? I suppose that the action added above will do its job. Am I wrong?

For the added hooks to be effective, we must delay the deletion. Done in b01def5.

Chouby · 2025-04-14T12:25:32Z

tests/phpunit/data/object-cache-annihilator.php

@@ -0,0 +1,523 @@
+<?php
+/**
+ * Object Cache Annihilator.


I guess the source of this file is coming from https://github.com/polylang/object-cache-annihilator.
I suggest to maintain only the plugin and "require-dev" it with composer to re-use it.

Done in e789585.

Chouby · 2025-04-14T12:27:19Z

uninstall.php

 		delete_transient( 'pll_languages_list' );
+		delete_option( '_transient_pll_languages_list' ); // Force deletion of the transient from the options table in case external object cache is used.


Suggested change

delete_transient( 'pll_languages_list' );

delete_option( '_transient_pll_languages_list' ); // Force deletion of the transient from the options table in case external object cache is used.

delete_option( '_transient_pll_languages_list' ); // Force deletion of the transient from the options table in case external object cache is used.

We don't need to delete the external cache in case of clean uninstall. Do we?

Done in 3e66676.

…it in Test_Object_Cache, also ensure to not do anything until the cahce is dropped in in Test_Object_Cache::set_up().

…ght away.

…o_3_4().

Chouby · 2025-04-17T14:37:23Z

composer.json

+	"repositories": [
+		{
+			"name": "wpsyntex/object-cache-annihilator",
+			"type": "vcs",
+			"url":  "[email protected]:polylang/object-cache-annihilator.git"
+		}
+	],


I've added the package to Packagist: https://packagist.org/packages/wpsyntex/object-cache-annihilator
SO you shouldn't need this.

Nice 👍
Done in 1fd4beb.

uninstall.php

Co-authored-by: Chouby <[email protected]>

…ister_shutdown_function to remove Object Cache Annihilator properly in case of fatal error.

…o activate the cache, - ensure database contains the transient - assert the transient from database does not exist in the end.

…ect_cache global with it.

…oot_dir() new method.

…se COmposer API to get the path to the drop-in.

Chrystll · 2026-02-04T10:41:54Z

I have successfully tested the fix in an environment using Redis (via the Redis Object Cache plugin) to ensure that transients are correctly purged from the external cache.

Test :

Preparation (SQL): With Redis disabled, I identified the ghost entries _transient_pll_languages_list and _transient_pll_translated_slugs in the wp_options table. I manually deleted them to ensure no stale data remained in SQL.
Activation: Enabled Redis Object Cache. I verified that the status was "Enabled" and that WordPress was no longer writing transients to the SQL database (confirmed by the absence of new entries in wp_options).
Execution:

Modified the language order in Languages > Languages.
Added a new language.
(Pro version) Translated some slugs to trigger _transient_pll_translated_slugs.

Observation:

Front-end: All changes were reflected instantly on the live site.
Persistence: No manual "Flush Cache" was required. This confirms that delete_transient() successfully sent the purge command to Redis instead of trying to delete a row in the (now unused) SQL table.
SQL Check: Confirmed that the wp_options table remained empty for these keys, proving that the fix correctly targets the active cache layer.

Hug0-Drelon added 3 commits April 8, 2025 19:41

Enforce deletion/creation in options table when deleting/creating pll…

0bf3411

…_languages_list transient.

Ensure uninstall and upgrade process benefit from it.

efc3191

Ensure external object cache and options table data consistency for p…

b08ef22

…ll_languages_list transient with PHPUnit tests.

Hug0-Drelon self-assigned this Apr 8, 2025

Hug0-Drelon added the bug label Apr 8, 2025

Hug0-Drelon added this to the 3.8 milestone Apr 8, 2025

Hug0-Drelon added 2 commits April 8, 2025 19:58

Typo.

c383f5e

Add a backward compatibility with WordPress 6.4 and wp_prime_option_c…

1b159ed

…aches().

Screenfeed self-requested a review April 11, 2025 09:05

Screenfeed requested changes Apr 11, 2025

View reviewed changes

Hug0-Drelon and others added 4 commits April 12, 2025 00:20

wp_prime_option_caches() is to prime several options all at once, no …

d6e9238

…need to call it then.

Clean Object_Cache_Annihilator, remove core function implementations …

a75944e

…and prod code.

Make Test_Object_Cache when the fix is disabled: ensure to always use…

dda9d27

… the same instance of PLL_Model to avoid breaking global scope for other tests, do not clean cache to hard between actions, and call languages->set_ready() to allow Polylang to cache languages.

Update tests/phpunit/data/object-cache-annihilator.php

ffa1e42

Co-authored-by: Grégory Viguier <[email protected]>

Hug0-Drelon requested a review from Screenfeed April 14, 2025 07:47

Screenfeed requested changes Apr 14, 2025

View reviewed changes

tests/phpunit/tests/test-object-cache.php Outdated Show resolved Hide resolved

Update test-object-cache.php

89f382e

Co-authored-by: Grégory Viguier <[email protected]>

Screenfeed approved these changes Apr 14, 2025

View reviewed changes

Chouby requested changes Apr 14, 2025

View reviewed changes

Hug0-Drelon added 6 commits April 16, 2025 23:50

Use wpsyntex/object-cache-annihilator repo as dev dependency and use …

6faddcd

…it in Test_Object_Cache, also ensure to not do anything until the cahce is dropped in in Test_Object_Cache::set_up().

Require drop-in.php so Object_Cache_Annihilator class is available ri…

e789585

…ght away.

use Model\Languages::TRANSIENT_NAME in hooks handles.

a0e5313

Only cleanup DB in uninstall.php.

3e66676

Delete pll_languages_list transient during upgrade once PLL is loaded.

b01def5

Adpat expectation in Upgrade_Test::test_delete_transient_at_upgrade_t…

cb06115

…o_3_4().

Hug0-Drelon requested a review from Chouby April 17, 2025 11:15

Chouby requested changes Apr 17, 2025

View reviewed changes

Hug0-Drelon and others added 3 commits April 17, 2025 22:09

Typo in uninstall.php

1d228ed

Co-authored-by: Chouby <[email protected]>

Use wpsyntex/object-cache-annihilator from Packagist.

1fd4beb

Improve Test_Object_Cache: - use static setup and tear down - use reg…

5887a7e

…ister_shutdown_function to remove Object Cache Annihilator properly in case of fatal error.

Hug0-Drelon added 3 commits April 18, 2025 11:29

Remove set_transient_to_options_table().

9d28161

Ensure test fails when the fix is removed: - create languages prior t…

ad16085

…o activate the cache, - ensure database contains the transient - assert the transient from database does not exist in the end.

Create PLL_Object_Cache_TestCase.

9e46188

Hug0-Drelon requested a review from Chouby April 18, 2025 09:45

Hug0-Drelon added 3 commits April 18, 2025 12:05

Drop-in the annihilator during set_up() to prevent backing up $wp_obj…

1e0bf7c

…ect_cache global with it.

Dynamically retrieve root dir in PLL_Object_Cache_TestCase with get_r…

ec6a463

…oot_dir() new method.

Install and remove external object cache only in static methods and u…

126cfa5

…se COmposer API to get the path to the drop-in.

Chouby merged commit 01572b1 into master Apr 22, 2025
8 checks passed

Chouby deleted the enforce-transient-deletion branch April 22, 2025 08:05

sebastienserre added the validated label Feb 3, 2026

		add_action( 'delete_transient_pll_languages_list', array( $this->languages, 'delete_transient_from_options_table' ) );
		add_action( 'set_transient_pll_languages_list', array( $this->languages, 'set_transient_to_options_table' ) );

		delete_transient( 'pll_languages_list' );
		delete_option( '_transient_pll_languages_list' ); // Force deletion of the transient from the options table in case external object cache is used.

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Chrystll commented Feb 4, 2026

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