class.jetpack-sync-queue.php
| 1 | <?php |
| 2 | |
| 3 | /** |
| 4 | * A buffer of items from the queue that can be checked out |
| 5 | */ |
| 6 | class Jetpack_Sync_Queue_Buffer { |
| 7 | public $id; |
| 8 | public $items_with_ids; |
| 9 | |
| 10 | public function __construct( $id, $items_with_ids ) { |
| 11 | $this->id = $id; |
| 12 | $this->items_with_ids = $items_with_ids; |
| 13 | } |
| 14 | |
| 15 | public function get_items() { |
| 16 | return array_combine( $this->get_item_ids(), $this->get_item_values() ); |
| 17 | } |
| 18 | |
| 19 | public function get_item_values() { |
| 20 | return Jetpack_Sync_Utils::get_item_values( $this->items_with_ids ); |
| 21 | } |
| 22 | |
| 23 | public function get_item_ids() { |
| 24 | return Jetpack_Sync_Utils::get_item_ids( $this->items_with_ids ); |
| 25 | } |
| 26 | } |
| 27 | |
| 28 | /** |
| 29 | * A persistent queue that can be flushed in increments of N items, |
| 30 | * and which blocks reads until checked-out buffers are checked in or |
| 31 | * closed. This uses raw SQL for two reasons: speed, and not triggering |
| 32 | * tons of added_option callbacks. |
| 33 | */ |
| 34 | class Jetpack_Sync_Queue { |
| 35 | public $id; |
| 36 | private $row_iterator; |
| 37 | |
| 38 | function __construct( $id ) { |
| 39 | $this->id = str_replace( '-', '_', $id ); // necessary to ensure we don't have ID collisions in the SQL |
| 40 | $this->row_iterator = 0; |
| 41 | $this->random_int = mt_rand( 1, 1000000 ); |
| 42 | } |
| 43 | |
| 44 | function add( $item ) { |
| 45 | global $wpdb; |
| 46 | $added = false; |
| 47 | // this basically tries to add the option until enough time has elapsed that |
| 48 | // it has a unique (microtime-based) option key |
| 49 | while ( ! $added ) { |
| 50 | $rows_added = $wpdb->query( $wpdb->prepare( |
| 51 | "INSERT INTO $wpdb->options (option_name, option_value, autoload) VALUES (%s, %s,%s)", |
| 52 | $this->get_next_data_row_option_name(), |
| 53 | serialize( $item ), |
| 54 | 'no' |
| 55 | ) ); |
| 56 | $added = ( 0 !== $rows_added ); |
| 57 | } |
| 58 | } |
| 59 | |
| 60 | // Attempts to insert all the items in a single SQL query. May be subject to query size limits! |
| 61 | function add_all( $items ) { |
| 62 | global $wpdb; |
| 63 | $base_option_name = $this->get_next_data_row_option_name(); |
| 64 | |
| 65 | $query = "INSERT INTO $wpdb->options (option_name, option_value, autoload) VALUES "; |
| 66 | |
| 67 | $rows = array(); |
| 68 | |
| 69 | for ( $i = 0; $i < count( $items ); $i += 1 ) { |
| 70 | $option_name = esc_sql( $base_option_name . '-' . $i ); |
| 71 | $option_value = esc_sql( serialize( $items[ $i ] ) ); |
| 72 | $rows[] = "('$option_name', '$option_value', 'no')"; |
| 73 | } |
| 74 | |
| 75 | $rows_added = $wpdb->query( $query . join( ',', $rows ) ); |
| 76 | |
| 77 | if ( count( $items ) === $rows_added ) { |
| 78 | return new WP_Error( 'row_count_mismatch', "The number of rows inserted didn't match the size of the input array" ); |
| 79 | } |
| 80 | } |
| 81 | |
| 82 | // Peek at the front-most item on the queue without checking it out |
| 83 | function peek( $count = 1 ) { |
| 84 | $items = $this->fetch_items( $count ); |
| 85 | if ( $items ) { |
| 86 | return Jetpack_Sync_Utils::get_item_values( $items ); |
| 87 | } |
| 88 | |
| 89 | return array(); |
| 90 | } |
| 91 | |
| 92 | // lag is the difference in time between the age of the oldest item |
| 93 | // (aka first or frontmost item) and the current time |
| 94 | function lag() { |
| 95 | global $wpdb; |
| 96 | |
| 97 | $first_item_name = $wpdb->get_var( $wpdb->prepare( |
| 98 | "SELECT option_name FROM $wpdb->options WHERE option_name LIKE %s ORDER BY option_name ASC LIMIT 1", |
| 99 | "jpsq_{$this->id}-%" |
| 100 | ) ); |
| 101 | |
| 102 | if ( ! $first_item_name ) { |
| 103 | return 0; |
| 104 | } |
| 105 | |
| 106 | // break apart the item name to get the timestamp |
| 107 | $matches = null; |
| 108 | if ( preg_match( '/^jpsq_' . $this->id . '-(\d+\.\d+)-/', $first_item_name, $matches ) ) { |
| 109 | return microtime( true ) - floatval( $matches[1] ); |
| 110 | } else { |
| 111 | return 0; |
| 112 | } |
| 113 | } |
| 114 | |
| 115 | function reset() { |
| 116 | global $wpdb; |
| 117 | $this->delete_checkout_id(); |
| 118 | $wpdb->query( $wpdb->prepare( |
| 119 | "DELETE FROM $wpdb->options WHERE option_name LIKE %s", "jpsq_{$this->id}-%" |
| 120 | ) ); |
| 121 | } |
| 122 | |
| 123 | function size() { |
| 124 | global $wpdb; |
| 125 | |
| 126 | return (int) $wpdb->get_var( $wpdb->prepare( |
| 127 | "SELECT count(*) FROM $wpdb->options WHERE option_name LIKE %s", "jpsq_{$this->id}-%" |
| 128 | ) ); |
| 129 | } |
| 130 | |
| 131 | // we use this peculiar implementation because it's much faster than count(*) |
| 132 | function has_any_items() { |
| 133 | global $wpdb; |
| 134 | $value = $wpdb->get_var( $wpdb->prepare( |
| 135 | "SELECT exists( SELECT option_name FROM $wpdb->options WHERE option_name LIKE %s )", "jpsq_{$this->id}-%" |
| 136 | ) ); |
| 137 | |
| 138 | return ( $value === '1' ); |
| 139 | } |
| 140 | |
| 141 | function checkout( $buffer_size ) { |
| 142 | if ( $this->get_checkout_id() ) { |
| 143 | return new WP_Error( 'unclosed_buffer', 'There is an unclosed buffer' ); |
| 144 | } |
| 145 | |
| 146 | $buffer_id = uniqid(); |
| 147 | |
| 148 | $result = $this->set_checkout_id( $buffer_id ); |
| 149 | |
| 150 | if ( ! $result || is_wp_error( $result ) ) { |
| 151 | return $result; |
| 152 | } |
| 153 | |
| 154 | $items = $this->fetch_items( $buffer_size ); |
| 155 | |
| 156 | if ( count( $items ) === 0 ) { |
| 157 | return false; |
| 158 | } |
| 159 | |
| 160 | $buffer = new Jetpack_Sync_Queue_Buffer( $buffer_id, array_slice( $items, 0, $buffer_size ) ); |
| 161 | |
| 162 | return $buffer; |
| 163 | } |
| 164 | |
| 165 | // this checks out rows until it either empties the queue or hits a certain memory limit |
| 166 | // it loads the sizes from the DB first so that it doesn't accidentally |
| 167 | // load more data into memory than it needs to. |
| 168 | // The only way it will load more items than $max_size is if a single queue item |
| 169 | // exceeds the memory limit, but in that case it will send that item by itself. |
| 170 | function checkout_with_memory_limit( $max_memory, $max_buffer_size = 500 ) { |
| 171 | if ( $this->get_checkout_id() ) { |
| 172 | return new WP_Error( 'unclosed_buffer', 'There is an unclosed buffer' ); |
| 173 | } |
| 174 | |
| 175 | $buffer_id = uniqid(); |
| 176 | |
| 177 | $result = $this->set_checkout_id( $buffer_id ); |
| 178 | |
| 179 | if ( ! $result || is_wp_error( $result ) ) { |
| 180 | return $result; |
| 181 | } |
| 182 | |
| 183 | // get the map of buffer_id -> memory_size |
| 184 | global $wpdb; |
| 185 | |
| 186 | $items_with_size = $wpdb->get_results( |
| 187 | $wpdb->prepare( |
| 188 | "SELECT option_name AS id, LENGTH(option_value) AS value_size FROM $wpdb->options WHERE option_name LIKE %s ORDER BY option_name ASC LIMIT %d", |
| 189 | "jpsq_{$this->id}-%", |
| 190 | $max_buffer_size |
| 191 | ), |
| 192 | OBJECT |
| 193 | ); |
| 194 | |
| 195 | if ( count( $items_with_size ) === 0 ) { |
| 196 | return false; |
| 197 | } |
| 198 | |
| 199 | $total_memory = 0; |
| 200 | |
| 201 | $min_item_id = $max_item_id = $items_with_size[0]->id; |
| 202 | |
| 203 | foreach ( $items_with_size as $id => $item_with_size ) { |
| 204 | $total_memory += $item_with_size->value_size; |
| 205 | |
| 206 | // if this is the first item and it exceeds memory, allow loop to continue |
| 207 | // we will exit on the next iteration instead |
| 208 | if ( $total_memory > $max_memory && $id > 0 ) { |
| 209 | break; |
| 210 | } |
| 211 | |
| 212 | $max_item_id = $item_with_size->id; |
| 213 | } |
| 214 | |
| 215 | $query = $wpdb->prepare( |
| 216 | "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", |
| 217 | $min_item_id, |
| 218 | $max_item_id |
| 219 | ); |
| 220 | |
| 221 | $items = $wpdb->get_results( $query, OBJECT ); |
| 222 | foreach ( $items as $item ) { |
| 223 | $item->value = maybe_unserialize( $item->value ); |
| 224 | } |
| 225 | |
| 226 | if ( count( $items ) === 0 ) { |
| 227 | $this->delete_checkout_id(); |
| 228 | |
| 229 | return false; |
| 230 | } |
| 231 | |
| 232 | $buffer = new Jetpack_Sync_Queue_Buffer( $buffer_id, $items ); |
| 233 | |
| 234 | return $buffer; |
| 235 | } |
| 236 | |
| 237 | function checkin( $buffer ) { |
| 238 | $is_valid = $this->validate_checkout( $buffer ); |
| 239 | |
| 240 | if ( is_wp_error( $is_valid ) ) { |
| 241 | return $is_valid; |
| 242 | } |
| 243 | |
| 244 | $this->delete_checkout_id(); |
| 245 | |
| 246 | return true; |
| 247 | } |
| 248 | |
| 249 | function close( $buffer, $ids_to_remove = null ) { |
| 250 | $is_valid = $this->validate_checkout( $buffer ); |
| 251 | |
| 252 | if ( is_wp_error( $is_valid ) ) { |
| 253 | return $is_valid; |
| 254 | } |
| 255 | |
| 256 | $this->delete_checkout_id(); |
| 257 | |
| 258 | // by default clear all items in the buffer |
| 259 | if ( is_null( $ids_to_remove ) ) { |
| 260 | $ids_to_remove = $buffer->get_item_ids(); |
| 261 | } |
| 262 | |
| 263 | global $wpdb; |
| 264 | |
| 265 | if ( count( $ids_to_remove ) > 0 ) { |
| 266 | $sql = "DELETE FROM $wpdb->options WHERE option_name IN (" . implode( ', ', array_fill( 0, count( $ids_to_remove ), '%s' ) ) . ')'; |
| 267 | $query = call_user_func_array( array( $wpdb, 'prepare' ), array_merge( array( $sql ), $ids_to_remove ) ); |
| 268 | $wpdb->query( $query ); |
| 269 | } |
| 270 | |
| 271 | return true; |
| 272 | } |
| 273 | |
| 274 | function flush_all() { |
| 275 | $items = Jetpack_Sync_Utils::get_item_values( $this->fetch_items() ); |
| 276 | $this->reset(); |
| 277 | |
| 278 | return $items; |
| 279 | } |
| 280 | |
| 281 | function get_all() { |
| 282 | return $this->fetch_items(); |
| 283 | } |
| 284 | |
| 285 | // use with caution, this could allow multiple processes to delete |
| 286 | // and send from the queue at the same time |
| 287 | function force_checkin() { |
| 288 | $this->delete_checkout_id(); |
| 289 | } |
| 290 | |
| 291 | // used to lock checkouts from the queue. |
| 292 | // tries to wait up to $timeout seconds for the queue to be empty |
| 293 | function lock( $timeout = 30 ) { |
| 294 | $tries = 0; |
| 295 | |
| 296 | while ( $this->has_any_items() && $tries < $timeout ) { |
| 297 | sleep( 1 ); |
| 298 | $tries += 1; |
| 299 | } |
| 300 | |
| 301 | if ( $tries === 30 ) { |
| 302 | return new WP_Error( 'lock_timeout', 'Timeout waiting for sync queue to empty' ); |
| 303 | } |
| 304 | |
| 305 | if ( $this->get_checkout_id() ) { |
| 306 | return new WP_Error( 'unclosed_buffer', 'There is an unclosed buffer' ); |
| 307 | } |
| 308 | |
| 309 | // hopefully this means we can acquire a checkout? |
| 310 | $result = $this->set_checkout_id( 'lock' ); |
| 311 | |
| 312 | if ( ! $result || is_wp_error( $result ) ) { |
| 313 | return $result; |
| 314 | } |
| 315 | |
| 316 | return true; |
| 317 | } |
| 318 | |
| 319 | function unlock() { |
| 320 | return $this->delete_checkout_id(); |
| 321 | } |
| 322 | |
| 323 | private function get_checkout_id() { |
| 324 | global $wpdb; |
| 325 | $checkout_value = $wpdb->get_var( |
| 326 | $wpdb->prepare( |
| 327 | "SELECT option_value FROM $wpdb->options WHERE option_name = %s", |
| 328 | $this->get_lock_option_name() |
| 329 | ) |
| 330 | ); |
| 331 | |
| 332 | if ( $checkout_value ) { |
| 333 | list( $checkout_id, $timestamp ) = explode( ':', $checkout_value ); |
| 334 | if ( intval( $timestamp ) > time() ) { |
| 335 | return $checkout_id; |
| 336 | } |
| 337 | } |
| 338 | |
| 339 | return false; |
| 340 | } |
| 341 | |
| 342 | private function set_checkout_id( $checkout_id ) { |
| 343 | global $wpdb; |
| 344 | |
| 345 | $expires = time() + Jetpack_Sync_Defaults::$default_sync_queue_lock_timeout; |
| 346 | $updated_num = $wpdb->query( |
| 347 | $wpdb->prepare( |
| 348 | "UPDATE $wpdb->options SET option_value = %s WHERE option_name = %s", |
| 349 | "$checkout_id:$expires", |
| 350 | $this->get_lock_option_name() |
| 351 | ) |
| 352 | ); |
| 353 | |
| 354 | if ( ! $updated_num ) { |
| 355 | $updated_num = $wpdb->query( |
| 356 | $wpdb->prepare( |
| 357 | "INSERT INTO $wpdb->options ( option_name, option_value, autoload ) VALUES ( %s, %s, 'no' )", |
| 358 | $this->get_lock_option_name(), |
| 359 | "$checkout_id:$expires" |
| 360 | ) |
| 361 | ); |
| 362 | } |
| 363 | |
| 364 | return $updated_num; |
| 365 | } |
| 366 | |
| 367 | private function delete_checkout_id() { |
| 368 | global $wpdb; |
| 369 | // rather than delete, which causes fragmentation, we update in place |
| 370 | return $wpdb->query( |
| 371 | $wpdb->prepare( |
| 372 | "UPDATE $wpdb->options SET option_value = %s WHERE option_name = %s", |
| 373 | "0:0", |
| 374 | $this->get_lock_option_name() |
| 375 | ) |
| 376 | ); |
| 377 | |
| 378 | } |
| 379 | |
| 380 | private function get_lock_option_name() { |
| 381 | return "jpsq_{$this->id}_checkout"; |
| 382 | } |
| 383 | |
| 384 | private function get_next_data_row_option_name() { |
| 385 | // this option is specifically chosen to, as much as possible, preserve time order |
| 386 | // and minimise the possibility of collisions between multiple processes working |
| 387 | // at the same time |
| 388 | // TODO: confirm we only need to support PHP 5.05+ (otherwise we'll need to emulate microtime as float, and avoid PHP_INT_MAX) |
| 389 | // @see: http://php.net/manual/en/function.microtime.php |
| 390 | $timestamp = sprintf( '%.6f', microtime( true ) ); |
| 391 | |
| 392 | // row iterator is used to avoid collisions where we're writing data waaay fast in a single process |
| 393 | if ( $this->row_iterator === PHP_INT_MAX ) { |
| 394 | $this->row_iterator = 0; |
| 395 | } else { |
| 396 | $this->row_iterator += 1; |
| 397 | } |
| 398 | |
| 399 | return 'jpsq_' . $this->id . '-' . $timestamp . '-' . $this->random_int . '-' . $this->row_iterator; |
| 400 | } |
| 401 | |
| 402 | private function fetch_items( $limit = null ) { |
| 403 | global $wpdb; |
| 404 | |
| 405 | if ( $limit ) { |
| 406 | $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 ); |
| 407 | } else { |
| 408 | $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}-%" ); |
| 409 | } |
| 410 | |
| 411 | $items = $wpdb->get_results( $query_sql, OBJECT ); |
| 412 | foreach ( $items as $item ) { |
| 413 | $item->value = maybe_unserialize( $item->value ); |
| 414 | } |
| 415 | |
| 416 | return $items; |
| 417 | } |
| 418 | |
| 419 | private function validate_checkout( $buffer ) { |
| 420 | if ( ! $buffer instanceof Jetpack_Sync_Queue_Buffer ) { |
| 421 | return new WP_Error( 'not_a_buffer', 'You must checkin an instance of Jetpack_Sync_Queue_Buffer' ); |
| 422 | } |
| 423 | |
| 424 | $checkout_id = $this->get_checkout_id(); |
| 425 | |
| 426 | if ( ! $checkout_id ) { |
| 427 | return new WP_Error( 'buffer_not_checked_out', 'There are no checked out buffers' ); |
| 428 | } |
| 429 | |
| 430 | if ( $checkout_id != $buffer->id ) { |
| 431 | return new WP_Error( 'buffer_mismatch', 'The buffer you checked in was not checked out' ); |
| 432 | } |
| 433 | |
| 434 | return true; |
| 435 | } |
| 436 | } |
| 437 | |
| 438 | class Jetpack_Sync_Utils { |
| 439 | |
| 440 | static function get_item_values( $items ) { |
| 441 | return array_map( array( __CLASS__, 'get_item_value' ), $items ); |
| 442 | } |
| 443 | |
| 444 | static function get_item_ids( $items ) { |
| 445 | return array_map( array( __CLASS__, 'get_item_id' ), $items ); |
| 446 | } |
| 447 | |
| 448 | static private function get_item_value( $item ) { |
| 449 | return $item->value; |
| 450 | } |
| 451 | |
| 452 | static private function get_item_id( $item ) { |
| 453 | return $item->id; |
| 454 | } |
| 455 | } |
| 456 |