diff options
Diffstat (limited to 'plugins/jetpack/sync/class.jetpack-sync-queue.php')
| -rw-r--r-- | plugins/jetpack/sync/class.jetpack-sync-queue.php | 478 |
1 files changed, 478 insertions, 0 deletions
diff --git a/plugins/jetpack/sync/class.jetpack-sync-queue.php b/plugins/jetpack/sync/class.jetpack-sync-queue.php new file mode 100644 index 00000000..ae40a597 --- /dev/null +++ b/plugins/jetpack/sync/class.jetpack-sync-queue.php @@ -0,0 +1,478 @@ +<?php + +/** + * A buffer of items from the queue that can be checked out + */ +class Jetpack_Sync_Queue_Buffer { + public $id; + public $items_with_ids; + + public function __construct( $id, $items_with_ids ) { + $this->id = $id; + $this->items_with_ids = $items_with_ids; + } + + public function get_items() { + return array_combine( $this->get_item_ids(), $this->get_item_values() ); + } + + public function get_item_values() { + return Jetpack_Sync_Utils::get_item_values( $this->items_with_ids ); + } + + public function get_item_ids() { + return Jetpack_Sync_Utils::get_item_ids( $this->items_with_ids ); + } +} + +/** + * A persistent queue that can be flushed in increments of N items, + * and which blocks reads until checked-out buffers are checked in or + * closed. This uses raw SQL for two reasons: speed, and not triggering + * tons of added_option callbacks. + */ +class Jetpack_Sync_Queue { + public $id; + private $row_iterator; + + function __construct( $id ) { + $this->id = str_replace( '-', '_', $id ); // necessary to ensure we don't have ID collisions in the SQL + $this->row_iterator = 0; + $this->random_int = mt_rand( 1, 1000000 ); + } + + function add( $item ) { + global $wpdb; + $added = false; + // this basically tries to add the option until enough time has elapsed that + // it has a unique (microtime-based) option key + while ( ! $added ) { + $rows_added = $wpdb->query( + $wpdb->prepare( + "INSERT INTO $wpdb->options (option_name, option_value, autoload) VALUES (%s, %s,%s)", + $this->get_next_data_row_option_name(), + serialize( $item ), + 'no' + ) + ); + $added = ( 0 !== $rows_added ); + } + } + + // Attempts to insert all the items in a single SQL query. May be subject to query size limits! + function add_all( $items ) { + global $wpdb; + $base_option_name = $this->get_next_data_row_option_name(); + + $query = "INSERT INTO $wpdb->options (option_name, option_value, autoload) VALUES "; + + $rows = array(); + + for ( $i = 0; $i < count( $items ); $i += 1 ) { + $option_name = esc_sql( $base_option_name . '-' . $i ); + $option_value = esc_sql( serialize( $items[ $i ] ) ); + $rows[] = "('$option_name', '$option_value', 'no')"; + } + + $rows_added = $wpdb->query( $query . join( ',', $rows ) ); + + if ( count( $items ) === $rows_added ) { + return new WP_Error( 'row_count_mismatch', "The number of rows inserted didn't match the size of the input array" ); + } + } + + // Peek at the front-most item on the queue without checking it out + function peek( $count = 1 ) { + $items = $this->fetch_items( $count ); + if ( $items ) { + return Jetpack_Sync_Utils::get_item_values( $items ); + } + + return array(); + } + + // lag is the difference in time between the age of the oldest item + // (aka first or frontmost item) and the current time + function lag( $now = null ) { + global $wpdb; + + $first_item_name = $wpdb->get_var( + $wpdb->prepare( + "SELECT option_name FROM $wpdb->options WHERE option_name LIKE %s ORDER BY option_name ASC LIMIT 1", + "jpsq_{$this->id}-%" + ) + ); + + if ( ! $first_item_name ) { + return 0; + } + + if ( null === $now ) { + $now = microtime( true ); + } + + // break apart the item name to get the timestamp + $matches = null; + if ( preg_match( '/^jpsq_' . $this->id . '-(\d+\.\d+)-/', $first_item_name, $matches ) ) { + return $now - floatval( $matches[1] ); + } else { + return 0; + } + } + + function reset() { + global $wpdb; + $this->delete_checkout_id(); + $wpdb->query( + $wpdb->prepare( + "DELETE FROM $wpdb->options WHERE option_name LIKE %s", + "jpsq_{$this->id}-%" + ) + ); + } + + function size() { + global $wpdb; + + return (int) $wpdb->get_var( + $wpdb->prepare( + "SELECT count(*) FROM $wpdb->options WHERE option_name LIKE %s", + "jpsq_{$this->id}-%" + ) + ); + } + + // we use this peculiar implementation because it's much faster than count(*) + function has_any_items() { + global $wpdb; + $value = $wpdb->get_var( + $wpdb->prepare( + "SELECT exists( SELECT option_name FROM $wpdb->options WHERE option_name LIKE %s )", + "jpsq_{$this->id}-%" + ) + ); + + return ( $value === '1' ); + } + + function checkout( $buffer_size ) { + if ( $this->get_checkout_id() ) { + return new WP_Error( 'unclosed_buffer', 'There is an unclosed buffer' ); + } + + $buffer_id = uniqid(); + + $result = $this->set_checkout_id( $buffer_id ); + + if ( ! $result || is_wp_error( $result ) ) { + return $result; + } + + $items = $this->fetch_items( $buffer_size ); + + if ( count( $items ) === 0 ) { + return false; + } + + $buffer = new Jetpack_Sync_Queue_Buffer( $buffer_id, array_slice( $items, 0, $buffer_size ) ); + + return $buffer; + } + + // this checks out rows until it either empties the queue or hits a certain memory limit + // it loads the sizes from the DB first so that it doesn't accidentally + // load more data into memory than it needs to. + // The only way it will load more items than $max_size is if a single queue item + // exceeds the memory limit, but in that case it will send that item by itself. + function checkout_with_memory_limit( $max_memory, $max_buffer_size = 500 ) { + if ( $this->get_checkout_id() ) { + return new WP_Error( 'unclosed_buffer', 'There is an unclosed buffer' ); + } + + $buffer_id = uniqid(); + + $result = $this->set_checkout_id( $buffer_id ); + + if ( ! $result || is_wp_error( $result ) ) { + return $result; + } + + // get the map of buffer_id -> memory_size + global $wpdb; + + $items_with_size = $wpdb->get_results( + $wpdb->prepare( + "SELECT option_name AS id, LENGTH(option_value) AS value_size FROM $wpdb->options WHERE option_name LIKE %s ORDER BY option_name ASC LIMIT %d", + "jpsq_{$this->id}-%", + $max_buffer_size + ), + OBJECT + ); + + if ( count( $items_with_size ) === 0 ) { + return false; + } + + $total_memory = 0; + + $min_item_id = $max_item_id = $items_with_size[0]->id; + + foreach ( $items_with_size as $id => $item_with_size ) { + $total_memory += $item_with_size->value_size; + + // if this is the first item and it exceeds memory, allow loop to continue + // we will exit on the next iteration instead + if ( $total_memory > $max_memory && $id > 0 ) { + break; + } + + $max_item_id = $item_with_size->id; + } + + $query = $wpdb->prepare( + "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", + $min_item_id, + $max_item_id + ); + + $items = $wpdb->get_results( $query, OBJECT ); + foreach ( $items as $item ) { + $item->value = maybe_unserialize( $item->value ); + } + + if ( count( $items ) === 0 ) { + $this->delete_checkout_id(); + + return false; + } + + $buffer = new Jetpack_Sync_Queue_Buffer( $buffer_id, $items ); + + return $buffer; + } + + function checkin( $buffer ) { + $is_valid = $this->validate_checkout( $buffer ); + + if ( is_wp_error( $is_valid ) ) { + return $is_valid; + } + + $this->delete_checkout_id(); + + return true; + } + + function close( $buffer, $ids_to_remove = null ) { + $is_valid = $this->validate_checkout( $buffer ); + + if ( is_wp_error( $is_valid ) ) { + return $is_valid; + } + + $this->delete_checkout_id(); + + // by default clear all items in the buffer + if ( is_null( $ids_to_remove ) ) { + $ids_to_remove = $buffer->get_item_ids(); + } + + global $wpdb; + + if ( count( $ids_to_remove ) > 0 ) { + $sql = "DELETE FROM $wpdb->options WHERE option_name IN (" . implode( ', ', array_fill( 0, count( $ids_to_remove ), '%s' ) ) . ')'; + $query = call_user_func_array( array( $wpdb, 'prepare' ), array_merge( array( $sql ), $ids_to_remove ) ); + $wpdb->query( $query ); + } + + return true; + } + + function flush_all() { + $items = Jetpack_Sync_Utils::get_item_values( $this->fetch_items() ); + $this->reset(); + + return $items; + } + + function get_all() { + return $this->fetch_items(); + } + + // use with caution, this could allow multiple processes to delete + // and send from the queue at the same time + function force_checkin() { + $this->delete_checkout_id(); + } + + // used to lock checkouts from the queue. + // tries to wait up to $timeout seconds for the queue to be empty + function lock( $timeout = 30 ) { + $tries = 0; + + while ( $this->has_any_items() && $tries < $timeout ) { + sleep( 1 ); + $tries += 1; + } + + if ( $tries === 30 ) { + return new WP_Error( 'lock_timeout', 'Timeout waiting for sync queue to empty' ); + } + + if ( $this->get_checkout_id() ) { + return new WP_Error( 'unclosed_buffer', 'There is an unclosed buffer' ); + } + + // hopefully this means we can acquire a checkout? + $result = $this->set_checkout_id( 'lock' ); + + if ( ! $result || is_wp_error( $result ) ) { + return $result; + } + + return true; + } + + function unlock() { + return $this->delete_checkout_id(); + } + + /** + * This option is specifically chosen to, as much as possible, preserve time order + * and minimise the possibility of collisions between multiple processes working + * at the same time. + * + * @return string + */ + protected function generate_option_name_timestamp() { + return sprintf( '%.6f', microtime( true ) ); + } + + private function get_checkout_id() { + global $wpdb; + $checkout_value = $wpdb->get_var( + $wpdb->prepare( + "SELECT option_value FROM $wpdb->options WHERE option_name = %s", + $this->get_lock_option_name() + ) + ); + + if ( $checkout_value ) { + list( $checkout_id, $timestamp ) = explode( ':', $checkout_value ); + if ( intval( $timestamp ) > time() ) { + return $checkout_id; + } + } + + return false; + } + + private function set_checkout_id( $checkout_id ) { + global $wpdb; + + $expires = time() + Jetpack_Sync_Defaults::$default_sync_queue_lock_timeout; + $updated_num = $wpdb->query( + $wpdb->prepare( + "UPDATE $wpdb->options SET option_value = %s WHERE option_name = %s", + "$checkout_id:$expires", + $this->get_lock_option_name() + ) + ); + + if ( ! $updated_num ) { + $updated_num = $wpdb->query( + $wpdb->prepare( + "INSERT INTO $wpdb->options ( option_name, option_value, autoload ) VALUES ( %s, %s, 'no' )", + $this->get_lock_option_name(), + "$checkout_id:$expires" + ) + ); + } + + return $updated_num; + } + + private function delete_checkout_id() { + global $wpdb; + // rather than delete, which causes fragmentation, we update in place + return $wpdb->query( + $wpdb->prepare( + "UPDATE $wpdb->options SET option_value = %s WHERE option_name = %s", + '0:0', + $this->get_lock_option_name() + ) + ); + + } + + private function get_lock_option_name() { + return "jpsq_{$this->id}_checkout"; + } + + private function get_next_data_row_option_name() { + $timestamp = $this->generate_option_name_timestamp(); + + // row iterator is used to avoid collisions where we're writing data waaay fast in a single process + if ( $this->row_iterator === PHP_INT_MAX ) { + $this->row_iterator = 0; + } else { + $this->row_iterator += 1; + } + + return 'jpsq_' . $this->id . '-' . $timestamp . '-' . $this->random_int . '-' . $this->row_iterator; + } + + private function fetch_items( $limit = null ) { + global $wpdb; + + if ( $limit ) { + $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 ); + } else { + $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}-%" ); + } + + $items = $wpdb->get_results( $query_sql, OBJECT ); + foreach ( $items as $item ) { + $item->value = maybe_unserialize( $item->value ); + } + + return $items; + } + + private function validate_checkout( $buffer ) { + if ( ! $buffer instanceof Jetpack_Sync_Queue_Buffer ) { + return new WP_Error( 'not_a_buffer', 'You must checkin an instance of Jetpack_Sync_Queue_Buffer' ); + } + + $checkout_id = $this->get_checkout_id(); + + if ( ! $checkout_id ) { + return new WP_Error( 'buffer_not_checked_out', 'There are no checked out buffers' ); + } + + if ( $checkout_id != $buffer->id ) { + return new WP_Error( 'buffer_mismatch', 'The buffer you checked in was not checked out' ); + } + + return true; + } +} + +class Jetpack_Sync_Utils { + + static function get_item_values( $items ) { + return array_map( array( __CLASS__, 'get_item_value' ), $items ); + } + + static function get_item_ids( $items ) { + return array_map( array( __CLASS__, 'get_item_id' ), $items ); + } + + private static function get_item_value( $item ) { + return $item->value; + } + + private static function get_item_id( $item ) { + return $item->id; + } +} |