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<?php |
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/** |
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* A buffer of items from the queue that can be checked out |
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*/ |
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class Jetpack_Sync_Queue_Buffer { |
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public $id; |
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public $items_with_ids; |
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public function __construct( $id, $items_with_ids ) { |
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$this->id = $id; |
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$this->items_with_ids = $items_with_ids; |
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} |
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public function get_items() { |
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return array_combine( $this->get_item_ids(), $this->get_item_values() ); |
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} |
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public function get_item_values() { |
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return Jetpack_Sync_Utils::get_item_values( $this->items_with_ids ); |
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} |
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public function get_item_ids() { |
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return Jetpack_Sync_Utils::get_item_ids( $this->items_with_ids ); |
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} |
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} |
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/** |
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* A persistent queue that can be flushed in increments of N items, |
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* and which blocks reads until checked-out buffers are checked in or |
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* closed. This uses raw SQL for two reasons: speed, and not triggering |
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* tons of added_option callbacks. |
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*/ |
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class Jetpack_Sync_Queue { |
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public $id; |
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private $row_iterator; |
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function __construct( $id ) { |
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$this->id = str_replace( '-', '_', $id ); // necessary to ensure we don't have ID collisions in the SQL |
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$this->row_iterator = 0; |
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$this->random_int = mt_rand( 1, 1000000 ); |
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} |
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function add( $item ) { |
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global $wpdb; |
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$added = false; |
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// this basically tries to add the option until enough time has elapsed that |
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// it has a unique (microtime-based) option key |
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while ( ! $added ) { |
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$rows_added = $wpdb->query( $wpdb->prepare( |
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"INSERT INTO $wpdb->options (option_name, option_value, autoload) VALUES (%s, %s,%s)", |
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$this->get_next_data_row_option_name(), |
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serialize( $item ), |
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'no' |
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) ); |
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$added = ( 0 !== $rows_added ); |
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} |
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} |
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// Attempts to insert all the items in a single SQL query. May be subject to query size limits! |
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function add_all( $items ) { |
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global $wpdb; |
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$base_option_name = $this->get_next_data_row_option_name(); |
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$query = "INSERT INTO $wpdb->options (option_name, option_value, autoload) VALUES "; |
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$rows = array(); |
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for ( $i = 0; $i < count( $items ); $i += 1 ) { |
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$option_name = esc_sql( $base_option_name . '-' . $i ); |
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$option_value = esc_sql( serialize( $items[ $i ] ) ); |
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$rows[] = "('$option_name', '$option_value', 'no')"; |
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} |
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$rows_added = $wpdb->query( $query . join( ',', $rows ) ); |
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if ( count( $items ) === $rows_added ) { |
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return new WP_Error( 'row_count_mismatch', "The number of rows inserted didn't match the size of the input array" ); |
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} |
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} |
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// Peek at the front-most item on the queue without checking it out |
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function peek( $count = 1 ) { |
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$items = $this->fetch_items( $count ); |
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if ( $items ) { |
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return Jetpack_Sync_Utils::get_item_values( $items ); |
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} |
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return array(); |
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} |
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// lag is the difference in time between the age of the oldest item |
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// (aka first or frontmost item) and the current time |
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function lag( $now = null ) { |
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global $wpdb; |
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$first_item_name = $wpdb->get_var( $wpdb->prepare( |
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"SELECT option_name FROM $wpdb->options WHERE option_name LIKE %s ORDER BY option_name ASC LIMIT 1", |
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"jpsq_{$this->id}-%" |
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) ); |
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if ( ! $first_item_name ) { |
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return 0; |
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} |
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if ( null === $now ) { |
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$now = microtime( true ); |
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} |
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// break apart the item name to get the timestamp |
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$matches = null; |
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if ( preg_match( '/^jpsq_' . $this->id . '-(\d+\.\d+)-/', $first_item_name, $matches ) ) { |
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return $now - floatval( $matches[1] ); |
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} else { |
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return 0; |
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} |
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} |
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function reset() { |
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global $wpdb; |
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$this->delete_checkout_id(); |
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$wpdb->query( $wpdb->prepare( |
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"DELETE FROM $wpdb->options WHERE option_name LIKE %s", "jpsq_{$this->id}-%" |
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) ); |
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} |
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function size() { |
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global $wpdb; |
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return (int) $wpdb->get_var( $wpdb->prepare( |
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"SELECT count(*) FROM $wpdb->options WHERE option_name LIKE %s", "jpsq_{$this->id}-%" |
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) ); |
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} |
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// we use this peculiar implementation because it's much faster than count(*) |
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function has_any_items() { |
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global $wpdb; |
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$value = $wpdb->get_var( $wpdb->prepare( |
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"SELECT exists( SELECT option_name FROM $wpdb->options WHERE option_name LIKE %s )", "jpsq_{$this->id}-%" |
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) ); |
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return ( $value === '1' ); |
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} |
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function checkout( $buffer_size ) { |
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if ( $this->get_checkout_id() ) { |
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return new WP_Error( 'unclosed_buffer', 'There is an unclosed buffer' ); |
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} |
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$buffer_id = uniqid(); |
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$result = $this->set_checkout_id( $buffer_id ); |
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if ( ! $result || is_wp_error( $result ) ) { |
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return $result; |
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} |
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$items = $this->fetch_items( $buffer_size ); |
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if ( count( $items ) === 0 ) { |
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return false; |
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} |
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$buffer = new Jetpack_Sync_Queue_Buffer( $buffer_id, array_slice( $items, 0, $buffer_size ) ); |
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return $buffer; |
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} |
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// this checks out rows until it either empties the queue or hits a certain memory limit |
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// it loads the sizes from the DB first so that it doesn't accidentally |
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// load more data into memory than it needs to. |
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// The only way it will load more items than $max_size is if a single queue item |
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// exceeds the memory limit, but in that case it will send that item by itself. |
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function checkout_with_memory_limit( $max_memory, $max_buffer_size = 500 ) { |
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if ( $this->get_checkout_id() ) { |
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return new WP_Error( 'unclosed_buffer', 'There is an unclosed buffer' ); |
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} |
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$buffer_id = uniqid(); |
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$result = $this->set_checkout_id( $buffer_id ); |
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if ( ! $result || is_wp_error( $result ) ) { |
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return $result; |
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} |
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// get the map of buffer_id -> memory_size |
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global $wpdb; |
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$items_with_size = $wpdb->get_results( |
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$wpdb->prepare( |
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"SELECT option_name AS id, LENGTH(option_value) AS value_size FROM $wpdb->options WHERE option_name LIKE %s ORDER BY option_name ASC LIMIT %d", |
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"jpsq_{$this->id}-%", |
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$max_buffer_size |
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), |
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OBJECT |
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); |
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if ( count( $items_with_size ) === 0 ) { |
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return false; |
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} |
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$total_memory = 0; |
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$min_item_id = $max_item_id = $items_with_size[0]->id; |
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foreach ( $items_with_size as $id => $item_with_size ) { |
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$total_memory += $item_with_size->value_size; |
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// if this is the first item and it exceeds memory, allow loop to continue |
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// we will exit on the next iteration instead |
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if ( $total_memory > $max_memory && $id > 0 ) { |
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break; |
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} |
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$max_item_id = $item_with_size->id; |
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} |
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$query = $wpdb->prepare( |
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"SELECT option_name AS id, option_value AS value FROM $wpdb->options WHERE option_name >= %s and option_name <= %s ORDER BY option_name ASC", |
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$min_item_id, |
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$max_item_id |
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); |
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$items = $wpdb->get_results( $query, OBJECT ); |
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foreach ( $items as $item ) { |
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$item->value = maybe_unserialize( $item->value ); |
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} |
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if ( count( $items ) === 0 ) { |
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$this->delete_checkout_id(); |
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return false; |
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} |
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$buffer = new Jetpack_Sync_Queue_Buffer( $buffer_id, $items ); |
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return $buffer; |
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} |
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function checkin( $buffer ) { |
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$is_valid = $this->validate_checkout( $buffer ); |
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if ( is_wp_error( $is_valid ) ) { |
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return $is_valid; |
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} |
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$this->delete_checkout_id(); |
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return true; |
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} |
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function close( $buffer, $ids_to_remove = null ) { |
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$is_valid = $this->validate_checkout( $buffer ); |
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if ( is_wp_error( $is_valid ) ) { |
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return $is_valid; |
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} |
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$this->delete_checkout_id(); |
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// by default clear all items in the buffer |
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if ( is_null( $ids_to_remove ) ) { |
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$ids_to_remove = $buffer->get_item_ids(); |
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} |
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global $wpdb; |
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if ( count( $ids_to_remove ) > 0 ) { |
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$sql = "DELETE FROM $wpdb->options WHERE option_name IN (" . implode( ', ', array_fill( 0, count( $ids_to_remove ), '%s' ) ) . ')'; |
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$query = call_user_func_array( array( $wpdb, 'prepare' ), array_merge( array( $sql ), $ids_to_remove ) ); |
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$wpdb->query( $query ); |
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} |
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return true; |
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} |
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function flush_all() { |
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$items = Jetpack_Sync_Utils::get_item_values( $this->fetch_items() ); |
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$this->reset(); |
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return $items; |
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} |
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function get_all() { |
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return $this->fetch_items(); |
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} |
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// use with caution, this could allow multiple processes to delete |
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// and send from the queue at the same time |
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function force_checkin() { |
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$this->delete_checkout_id(); |
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} |
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// used to lock checkouts from the queue. |
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// tries to wait up to $timeout seconds for the queue to be empty |
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function lock( $timeout = 30 ) { |
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$tries = 0; |
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while ( $this->has_any_items() && $tries < $timeout ) { |
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sleep( 1 ); |
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$tries += 1; |
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} |
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if ( $tries === 30 ) { |
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return new WP_Error( 'lock_timeout', 'Timeout waiting for sync queue to empty' ); |
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} |
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if ( $this->get_checkout_id() ) { |
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return new WP_Error( 'unclosed_buffer', 'There is an unclosed buffer' ); |
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} |
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// hopefully this means we can acquire a checkout? |
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$result = $this->set_checkout_id( 'lock' ); |
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if ( ! $result || is_wp_error( $result ) ) { |
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return $result; |
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} |
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return true; |
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} |
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function unlock() { |
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return $this->delete_checkout_id(); |
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} |
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/** |
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* This option is specifically chosen to, as much as possible, preserve time order |
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* and minimise the possibility of collisions between multiple processes working |
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* at the same time. |
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* |
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* @return string |
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*/ |
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protected function generate_option_name_timestamp() { |
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return sprintf( '%.6f', microtime( true ) ); |
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} |
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private function get_checkout_id() { |
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global $wpdb; |
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$checkout_value = $wpdb->get_var( |
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$wpdb->prepare( |
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"SELECT option_value FROM $wpdb->options WHERE option_name = %s", |
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$this->get_lock_option_name() |
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) |
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); |
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347
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if ( $checkout_value ) { |
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list( $checkout_id, $timestamp ) = explode( ':', $checkout_value ); |
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if ( intval( $timestamp ) > time() ) { |
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return $checkout_id; |
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} |
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} |
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return false; |
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} |
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private function set_checkout_id( $checkout_id ) { |
358
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global $wpdb; |
359
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360
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$expires = time() + Jetpack_Sync_Defaults::$default_sync_queue_lock_timeout; |
|
|
|
|
361
|
|
|
$updated_num = $wpdb->query( |
362
|
|
|
$wpdb->prepare( |
363
|
|
|
"UPDATE $wpdb->options SET option_value = %s WHERE option_name = %s", |
364
|
|
|
"$checkout_id:$expires", |
365
|
|
|
$this->get_lock_option_name() |
366
|
|
|
) |
367
|
|
|
); |
368
|
|
|
|
369
|
|
|
if ( ! $updated_num ) { |
370
|
|
|
$updated_num = $wpdb->query( |
371
|
|
|
$wpdb->prepare( |
372
|
|
|
"INSERT INTO $wpdb->options ( option_name, option_value, autoload ) VALUES ( %s, %s, 'no' )", |
373
|
|
|
$this->get_lock_option_name(), |
374
|
|
|
"$checkout_id:$expires" |
375
|
|
|
) |
376
|
|
|
); |
377
|
|
|
} |
378
|
|
|
|
379
|
|
|
return $updated_num; |
380
|
|
|
} |
381
|
|
|
|
382
|
|
|
private function delete_checkout_id() { |
383
|
|
|
global $wpdb; |
384
|
|
|
// rather than delete, which causes fragmentation, we update in place |
385
|
|
|
return $wpdb->query( |
386
|
|
|
$wpdb->prepare( |
387
|
|
|
"UPDATE $wpdb->options SET option_value = %s WHERE option_name = %s", |
388
|
|
|
"0:0", |
389
|
|
|
$this->get_lock_option_name() |
390
|
|
|
) |
391
|
|
|
); |
392
|
|
|
|
393
|
|
|
} |
394
|
|
|
|
395
|
|
|
private function get_lock_option_name() { |
396
|
|
|
return "jpsq_{$this->id}_checkout"; |
397
|
|
|
} |
398
|
|
|
|
399
|
|
|
private function get_next_data_row_option_name() { |
400
|
|
|
$timestamp = $this->generate_option_name_timestamp(); |
401
|
|
|
|
402
|
|
|
// row iterator is used to avoid collisions where we're writing data waaay fast in a single process |
403
|
|
|
if ( $this->row_iterator === PHP_INT_MAX ) { |
404
|
|
|
$this->row_iterator = 0; |
405
|
|
|
} else { |
406
|
|
|
$this->row_iterator += 1; |
407
|
|
|
} |
408
|
|
|
|
409
|
|
|
return 'jpsq_' . $this->id . '-' . $timestamp . '-' . $this->random_int . '-' . $this->row_iterator; |
410
|
|
|
} |
411
|
|
|
|
412
|
|
|
private function fetch_items( $limit = null ) { |
413
|
|
|
global $wpdb; |
414
|
|
|
|
415
|
|
|
if ( $limit ) { |
416
|
|
|
$query_sql = $wpdb->prepare( "SELECT option_name AS id, option_value AS value FROM $wpdb->options WHERE option_name LIKE %s ORDER BY option_name ASC LIMIT %d", "jpsq_{$this->id}-%", $limit ); |
417
|
|
|
} else { |
418
|
|
|
$query_sql = $wpdb->prepare( "SELECT option_name AS id, option_value AS value FROM $wpdb->options WHERE option_name LIKE %s ORDER BY option_name ASC", "jpsq_{$this->id}-%" ); |
419
|
|
|
} |
420
|
|
|
|
421
|
|
|
$items = $wpdb->get_results( $query_sql, OBJECT ); |
422
|
|
|
foreach ( $items as $item ) { |
423
|
|
|
$item->value = maybe_unserialize( $item->value ); |
424
|
|
|
} |
425
|
|
|
|
426
|
|
|
return $items; |
427
|
|
|
} |
428
|
|
|
|
429
|
|
|
private function validate_checkout( $buffer ) { |
430
|
|
|
if ( ! $buffer instanceof Jetpack_Sync_Queue_Buffer ) { |
431
|
|
|
return new WP_Error( 'not_a_buffer', 'You must checkin an instance of Jetpack_Sync_Queue_Buffer' ); |
432
|
|
|
} |
433
|
|
|
|
434
|
|
|
$checkout_id = $this->get_checkout_id(); |
435
|
|
|
|
436
|
|
|
if ( ! $checkout_id ) { |
437
|
|
|
return new WP_Error( 'buffer_not_checked_out', 'There are no checked out buffers' ); |
438
|
|
|
} |
439
|
|
|
|
440
|
|
|
if ( $checkout_id != $buffer->id ) { |
441
|
|
|
return new WP_Error( 'buffer_mismatch', 'The buffer you checked in was not checked out' ); |
442
|
|
|
} |
443
|
|
|
|
444
|
|
|
return true; |
445
|
|
|
} |
446
|
|
|
} |
447
|
|
|
|
448
|
|
|
class Jetpack_Sync_Utils { |
|
|
|
|
449
|
|
|
|
450
|
|
|
static function get_item_values( $items ) { |
451
|
|
|
return array_map( array( __CLASS__, 'get_item_value' ), $items ); |
452
|
|
|
} |
453
|
|
|
|
454
|
|
|
static function get_item_ids( $items ) { |
455
|
|
|
return array_map( array( __CLASS__, 'get_item_id' ), $items ); |
456
|
|
|
} |
457
|
|
|
|
458
|
|
|
static private function get_item_value( $item ) { |
|
|
|
|
459
|
|
|
return $item->value; |
460
|
|
|
} |
461
|
|
|
|
462
|
|
|
static private function get_item_id( $item ) { |
|
|
|
|
463
|
|
|
return $item->id; |
464
|
|
|
} |
465
|
|
|
} |
466
|
|
|
|
Having each class in a dedicated file usually plays nice with PSR autoloaders and is therefore a well established practice. If you use other autoloaders, you might not want to follow this rule.