class ActionScheduler_OptionLock extends ActionScheduler_Lock {
/**
* Set a lock using options for a given amount of time (60 seconds by default).
*
* Using an autoloaded option avoids running database queries or other resource intensive tasks
* on frequently triggered hooks, like 'init' or 'shutdown'.
*
* For example, ActionScheduler_QueueRunner->maybe_dispatch_async_request() uses a lock to avoid
* calling ActionScheduler_QueueRunner->has_maximum_concurrent_batches() every time the 'shutdown',
* hook is triggered, because that method calls ActionScheduler_QueueRunner->store->get_claim_count()
* to find the current number of claims in the database.
*
* @param string $lock_type A string to identify different lock types.
* @bool True if lock value has changed, false if not or if set failed.
*/
public function set( $lock_type ) {
global $wpdb;
$lock_key = $this->get_key( $lock_type );
$existing_lock_value = $this->get_existing_lock( $lock_type );
$new_lock_value = $this->new_lock_value( $lock_type );
// The lock may not exist yet, or may have been deleted.
if ( empty( $existing_lock_value ) ) {
return (bool) $wpdb->insert(
$wpdb->options,
array(
'option_name' => $lock_key,
'option_value' => $new_lock_value,
'autoload' => 'no',
)
);
}
if ( $this->get_expiration_from( $existing_lock_value ) >= time() ) {
return false;
}
// Otherwise, try to obtain the lock.
return (bool) $wpdb->update(
$wpdb->options,
array( 'option_value' => $new_lock_value ),
array(
'option_name' => $lock_key,
'option_value' => $existing_lock_value,
)
);
}
/**
* If a lock is set, return the timestamp it was set to expiry.
*
* @param string $lock_type A string to identify different lock types.
* @return bool|int False if no lock is set, otherwise the timestamp for when the lock is set to expire.
*/
public function get_expiration( $lock_type ) {
return $this->get_expiration_from( $this->get_existing_lock( $lock_type ) );
}
/**
* Given the lock string, derives the lock expiration timestamp (or false if it cannot be determined).
*
* @param string $lock_value String containing a timestamp, or pipe-separated combination of unique value and timestamp.
*
* @return false|int
*/
private function get_expiration_from( $lock_value ) {
$lock_string = explode( '|', $lock_value );
// Old style lock?
if ( count( $lock_string ) === 1 && is_numeric( $lock_string[0] ) ) {
return (int) $lock_string[0];
}
// New style lock?
if ( count( $lock_string ) === 2 && is_numeric( $lock_string[1] ) ) {
return (int) $lock_string[1];
}
return false;
}
/**
* Get the key to use for storing the lock in the transient
*
* @param string $lock_type A string to identify different lock types.
* @return string
*/
protected function get_key( $lock_type ) {
return sprintf( 'action_scheduler_lock_%s', $lock_type );
}
/**
* Supplies the existing lock value, or an empty string if not set.
*
* @param string $lock_type A string to identify different lock types.
*
* @return string
*/
private function get_existing_lock( $lock_type ) {
global $wpdb;
// Now grab the existing lock value, if there is one.
return (string) $wpdb->get_var(
$wpdb->prepare(
"SELECT option_value FROM $wpdb->options WHERE option_name = %s",
$this->get_key( $lock_type )
)
);
}
/**
* Supplies a lock value consisting of a unique value and the current timestamp, which are separated by a pipe
* character.
*
* Example: (string) "649de012e6b262.09774912|1688068114"
*
* @param string $lock_type A string to identify different lock types.
*
* @return string
*/
private function new_lock_value( $lock_type ) {
return uniqid( '', true ) . '|' . ( time() + $this->get_duration( $lock_type ) );
}
}