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fix(locks): make cron admission atomic #522

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a510c48
fix(locks): make cron admission atomic
sjinks Aug 27, 2026
be8b1fa
fix(locks): avoid entropy errors during generation
sjinks Aug 27, 2026
74e1448
fix(locks): call WordPress random generator globally
sjinks Aug 27, 2026
6c92881
fix(locks): support generation before WordPress bootstrap
sjinks Aug 27, 2026
1094377
fix(locks): make release failures retryable
sjinks Aug 27, 2026
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179 changes: 179 additions & 0 deletions __tests__/unit-tests/test-lock.php
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Original file line number Diff line number Diff line change
@@ -0,0 +1,179 @@
<?php

namespace Automattic\WP\Cron_Control\Tests;

use Automattic\WP\Cron_Control\Lock;

class Lock_Tests extends \WP_UnitTestCase {
private $locks = array(
'concurrent-acquisition',
'rejected-admission',
'stale-lock',
'old-generation-cleanup',
'recreated-lock',
'reset-lock',
);

public function setUp(): void {
parent::setUp();

foreach ( $this->locks as $lock ) {
Lock::reset_lock( $lock );
}
}

public function tearDown(): void {
foreach ( $this->locks as $lock ) {
Lock::reset_lock( $lock );
}

parent::tearDown();
}

public function test_concurrent_acquisition_with_limit_one_admits_one_worker() {
$lock = 'concurrent-acquisition';

$this->assertTrue( Lock::check_lock( $lock, 1 ) );
$this->assertFalse( Lock::check_lock( $lock, 1 ) );
$this->assertSame( 1, Lock::get_lock_value( $lock ) );
}

public function test_rejected_admission_does_not_change_lock_value() {
$lock = 'rejected-admission';

$this->assertTrue( Lock::check_lock( $lock, 1 ) );
$this->assertFalse( Lock::check_lock( $lock, 1 ) );
$this->assertSame( 1, Lock::get_lock_value( $lock ) );
}

public function test_failed_lock_release_can_be_retried() {
global $wpdb;

$lock = 'failed-release';
$reflection = new \ReflectionProperty( Lock::class, 'acquired_locks' );
$reflection->setAccessible( true );
$original_locks = $reflection->getValue();
$original_wpdb = $wpdb;
$reflection->setValue(
array(
$lock => array( 1 ),
)
);
$wpdb = new class() {
public $options = 'wp_options';
public $queries = 0;

public function prepare( $query, ...$args ) {
return $query;
}

public function query( $query ) {
++$this->queries;

return 1 === $this->queries ? false : 0;
}
};

try {
$this->assertFalse( Lock::free_lock( $lock ) );
$this->assertSame( array( 1 ), $reflection->getValue()[ $lock ] );
$this->assertTrue( Lock::free_lock( $lock ) );
$this->assertSame( array(), $reflection->getValue()[ $lock ] );
} finally {
$wpdb = $original_wpdb;
$reflection->setValue( $original_locks );
}
}

public function test_stale_lock_recovery_records_the_new_admission() {
global $wpdb;

$lock = 'stale-lock';
$wpdb->update(
$wpdb->options,
array( 'option_value' => '1:' . ( time() - MINUTE_IN_SECONDS ) . ':1' ),
array( 'option_name' => 'a8ccc_lock_stale-lock' )
);

$this->assertTrue( Lock::check_lock( $lock, 1, 1 ) );
$this->assertSame( 1, Lock::get_lock_value( $lock ) );
$this->assertGreaterThan( time() - 2, Lock::get_lock_timestamp( $lock ) );
}

public function test_old_generation_cleanup_does_not_release_recovered_lock() {
global $wpdb;

$lock = 'old-generation-cleanup';
$this->assertTrue( Lock::check_lock( $lock, 1 ) );
$wpdb->update(
$wpdb->options,
array( 'option_value' => '1:' . ( time() - MINUTE_IN_SECONDS ) . ':1' ),
array( 'option_name' => 'a8ccc_lock_old-generation-cleanup' )
);
$this->assertTrue( Lock::check_lock( $lock, 1, 1 ) );
$state = explode( ':', $wpdb->get_var( "SELECT `option_value` FROM `$wpdb->options` WHERE `option_name` = 'a8ccc_lock_old-generation-cleanup'" ) );

$reflection = new \ReflectionProperty( Lock::class, 'acquired_locks' );
$reflection->setAccessible( true );
$reflection->setValue(
array(
$lock => array( (int) $state[2], 1 ),
)
);

$this->assertTrue( Lock::free_lock( $lock ) );
$this->assertSame( 1, Lock::get_lock_value( $lock ) );
}

public function test_old_generation_cleanup_does_not_release_a_recreated_lock() {
global $wpdb;

$lock = 'recreated-lock';
$this->assertTrue( Lock::check_lock( $lock, 1 ) );
$state = explode( ':', $wpdb->get_var( "SELECT `option_value` FROM `$wpdb->options` WHERE `option_name` = 'a8ccc_lock_recreated-lock'" ) );
$old_generation = (int) $state[2];
$this->assertTrue( Lock::free_lock( $lock ) );
$this->assertNull( $wpdb->get_var( "SELECT `option_value` FROM `$wpdb->options` WHERE `option_name` = 'a8ccc_lock_recreated-lock'" ) );

$this->assertTrue( Lock::check_lock( $lock, 1 ) );
$state = explode( ':', $wpdb->get_var( "SELECT `option_value` FROM `$wpdb->options` WHERE `option_name` = 'a8ccc_lock_recreated-lock'" ) );
$replacement_state = implode( ':', $state );
$replacement_generation = (int) $state[2];

$reflection = new \ReflectionProperty( Lock::class, 'acquired_locks' );
$reflection->setAccessible( true );
$reflection->setValue(
array(
$lock => array( $replacement_generation, $old_generation ),
)
);

$this->assertTrue( Lock::free_lock( $lock ) );
$this->assertSame( $replacement_state, $wpdb->get_var( "SELECT `option_value` FROM `$wpdb->options` WHERE `option_name` = 'a8ccc_lock_recreated-lock'" ) );
}

public function test_old_generation_cleanup_does_not_release_a_reset_lock() {
global $wpdb;

$lock = 'reset-lock';
$this->assertTrue( Lock::check_lock( $lock, 1 ) );
$state = explode( ':', $wpdb->get_var( "SELECT `option_value` FROM `$wpdb->options` WHERE `option_name` = 'a8ccc_lock_reset-lock'" ) );
$old_generation = (int) $state[2];
$this->assertTrue( Lock::reset_lock( $lock ) );
$this->assertTrue( Lock::check_lock( $lock, 1 ) );
$state = explode( ':', $wpdb->get_var( "SELECT `option_value` FROM `$wpdb->options` WHERE `option_name` = 'a8ccc_lock_reset-lock'" ) );
$replacement_state = implode( ':', $state );
$replacement_generation = (int) $state[2];

$reflection = new \ReflectionProperty( Lock::class, 'acquired_locks' );
$reflection->setAccessible( true );
$reflection->setValue(
array(
$lock => array( $replacement_generation, $old_generation ),
)
);

$this->assertTrue( Lock::free_lock( $lock ) );
$this->assertSame( $replacement_state, $wpdb->get_var( "SELECT `option_value` FROM `$wpdb->options` WHERE `option_name` = 'a8ccc_lock_reset-lock'" ) );
}
}
16 changes: 1 addition & 15 deletions includes/class-events.php
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Original file line number Diff line number Diff line change
Expand Up @@ -42,9 +42,6 @@ class Events extends Singleton {
* Register hooks
*/
protected function class_init() {
// Prime lock cache if not present.
Lock::prime_lock( self::LOCK );

// Prepare environment as early as possible.
$earliest_action = did_action( 'muplugins_loaded' ) ? 'plugins_loaded' : 'muplugins_loaded';
add_action( $earliest_action, array( $this, 'prepare_environment' ) );
Expand Down Expand Up @@ -241,9 +238,6 @@ public function run_event( $timestamp, $action, $instance, $force = false ) {

// Limit how many events are processed concurrently, unless explicitly bypassed.
if ( ! $force ) {
// Prepare event-level lock.
$this->prime_event_action_lock( $event );

if ( ! $this->can_run_event( $event ) ) {
/* translators: 1: Event action, 2: Event arguments */
$error_message = sprintf( __( 'No resources available to run the job with action `%1$s` and arguments `%2$s`.', 'automattic-cron-control' ), $event->get_action(), maybe_serialize( $event->get_args() ) );
Expand Down Expand Up @@ -300,10 +294,6 @@ public function run_event( $timestamp, $action, $instance, $force = false ) {
return $return;
}

private function prime_event_action_lock( Event $event ): void {
Lock::prime_lock( $this->get_lock_key_for_event_action( $event ), JOB_LOCK_EXPIRY_IN_MINUTES * \MINUTE_IN_SECONDS );
}

// Checks concurrency locks, deciding if the event can be run at this moment.
private function can_run_event( Event $event ): bool {
// Limit to one concurrent execution of a specific action by default.
Expand Down Expand Up @@ -348,11 +338,7 @@ private function reset_event_lock( Event $event ): bool {
$lock_key = $this->get_lock_key_for_event_action( $event );
$expires = JOB_LOCK_EXPIRY_IN_MINUTES * \MINUTE_IN_SECONDS;

if ( isset( $this->concurrent_action_whitelist[ $event->get_action() ] ) ) {
return Lock::free_lock( $lock_key, $expires );
} else {
return Lock::reset_lock( $lock_key, $expires );
}
return Lock::free_lock( $lock_key, $expires );
}

/**
Expand Down
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