notifier / libraries / action-scheduler / classes / ActionScheduler_OptionLock.php

ActionScheduler_OptionLock.php in WANotifier for Forms and Actions 3.1.1, at libraries/action-scheduler/classes/ActionScheduler_OptionLock.php

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1	<?php
2
3	/**
4	* Provide a way to set simple transient locks to block behaviour
5	* for up-to a given duration.
6	*
7	* Class ActionScheduler_OptionLock
8	*
9	* @since 3.0.0
10	*/
11	class ActionScheduler_OptionLock extends ActionScheduler_Lock {
12
13	/**
14	* Set a lock using options for a given amount of time (60 seconds by default).
15	*
16	* Using an autoloaded option avoids running database queries or other resource intensive tasks
17	* on frequently triggered hooks, like 'init' or 'shutdown'.
18	*
19	* For example, ActionScheduler_QueueRunner->maybe_dispatch_async_request() uses a lock to avoid
20	* calling ActionScheduler_QueueRunner->has_maximum_concurrent_batches() every time the 'shutdown',
21	* hook is triggered, because that method calls ActionScheduler_QueueRunner->store->get_claim_count()
22	* to find the current number of claims in the database.
23	*
24	* @param string $lock_type A string to identify different lock types.
25	* @bool True if lock value has changed, false if not or if set failed.
26	*/
27	public function set( $lock_type ) {
28	global $wpdb;
29
30	$now = time();
31	$lock_key = $this->get_key( $lock_type );
32	$existing_lock_value = $this->get_existing_lock( $lock_type, $now );
33	$new_lock_value = $this->new_lock_value( $lock_type, $now );
34
35	// The lock may not exist yet, or may have been deleted.
36	if ( null === $existing_lock_value ) {
37	$inserted = (bool) $wpdb->insert(
38	$wpdb->options,
39	array(
40	'option_name' => $lock_key,
41	'option_value' => $new_lock_value,
42	'autoload' => 'no',
43	)
44	);
45
46	// Sync cache as necessary.
47	if ( $inserted ) {
48	$ttl = $this->get_expiration_from( $new_lock_value ) - $now;
49	if ( $ttl > 0 ) {
50	wp_cache_set( $lock_key, $new_lock_value, 'action_scheduler_locks', $ttl );
51	}
52	}
53
54	return $inserted;
55	}
56
57	if ( $this->get_expiration_from( $existing_lock_value ) >= $now ) {
58	return false;
59	}
60
61	// Otherwise, try to obtain the lock.
62	$updated = (bool) $wpdb->update(
63	$wpdb->options,
64	array( 'option_value' => $new_lock_value ),
65	array(
66	'option_name' => $lock_key,
67	'option_value' => $existing_lock_value,
68	)
69	);
70
71	// Sync cache as necessary.
72	if ( $updated ) {
73	$ttl = $this->get_expiration_from( $new_lock_value ) - $now;
74	if ( $ttl > 0 ) {
75	wp_cache_set( $lock_key, $new_lock_value, 'action_scheduler_locks', $ttl );
76	}
77	} else {
78	// Compare-and-swap failed — another process acquired the lock between our read and write.
79	// Invalidate cache: the expired value may still be live in WP object cache (TTL=1 edge case) before the winner's wp_cache_set executes.
80	wp_cache_delete( $lock_key, 'action_scheduler_locks' );
81	}
82
83	return $updated;
84	}
85
86	/**
87	* If a lock is set, return the timestamp it was set to expiry.
88	*
89	* @param string $lock_type A string to identify different lock types.
90	* @return bool\|int False if no lock is set, otherwise the timestamp for when the lock is set to expire.
91	*/
92	public function get_expiration( $lock_type ) {
93	return $this->get_expiration_from( (string) $this->get_existing_lock( $lock_type, time() ) );
94	}
95
96	/**
97	* Given the lock string, derives the lock expiration timestamp (or false if it cannot be determined).
98	*
99	* @param string $lock_value String containing a timestamp, or pipe-separated combination of unique value and timestamp.
100	*
101	* @return false\|int
102	*/
103	private function get_expiration_from( $lock_value ) {
104	$lock_string = explode( '\|', $lock_value );
105	$count = count( $lock_string );
106
107	// Old style lock?
108	if ( 1 === $count && is_numeric( $lock_string[0] ) ) {
109	return (int) $lock_string[0];
110	}
111
112	// New style lock?
113	if ( 2 === $count && is_numeric( $lock_string[1] ) ) {
114	return (int) $lock_string[1];
115	}
116
117	return false;
118	}
119
120	/**
121	* Get the key to use for storing the lock in the transient
122	*
123	* @param string $lock_type A string to identify different lock types.
124	* @return string
125	*/
126	protected function get_key( $lock_type ) {
127	return sprintf( 'action_scheduler_lock_%s', $lock_type );
128	}
129
130	/**
131	* Supplies the existing lock value, or null if not set.
132	*
133	* @param string $lock_type A string to identify different lock types.
134	* @param int $now The timestamp to use.
135	*
136	* @return string\|null
137	*/
138	private function get_existing_lock( $lock_type, int $now ) {
139	global $wpdb;
140
141	$lock_key = $this->get_key( $lock_type );
142	$cached = wp_cache_get( $lock_key, 'action_scheduler_locks' );
143	if ( false !== $cached ) {
144	return (string) $cached;
145	}
146
147	$value = null;
148	// Now grab the existing lock value, if there is one.
149	// get_var() returns null for the empty string ('') so we must use get_row().
150	$row = $wpdb->get_row(
151	$wpdb->prepare(
152	"SELECT option_value FROM $wpdb->options WHERE option_name = %s",
153	$lock_key
154	)
155	);
156
157	if ( $row ) {
158	$value = $row->option_value;
159	// Sync cache as necessary.
160	$ttl = $this->get_expiration_from( $value ) - $now;
161	if ( $ttl > 0 ) {
162	wp_cache_set( $lock_key, $value, 'action_scheduler_locks', $ttl );
163	}
164	}
165
166	return $value;
167	}
168
169	/**
170	* Supplies a lock value consisting of a unique value and the current timestamp, which are separated by a pipe
171	* character.
172	*
173	* Example: (string) "649de012e6b262.09774912\|1688068114"
174	*
175	* @param string $lock_type A string to identify different lock types.
176	* @param int $now The timestamp to use.
177	*
178	* @return string
179	*/
180	private function new_lock_value( $lock_type, int $now ): string {
181	return uniqid( '', true ) . '\|' . ( $now + $this->get_duration( $lock_type ) );
182	}
183	}
184