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| 1 | <?php |
| 2 | /** |
| 3 | * This program is free software; you can redistribute it and/or modify |
| 4 | * it under the terms of the GNU General Public License as published by |
| 5 | * the Free Software Foundation; either version 2 of the License, or |
| 6 | * (at your option) any later version. |
| 7 | * |
| 8 | * This program is distributed in the hope that it will be useful, |
| 9 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 10 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 11 | * GNU General Public License for more details. |
| 12 | * |
| 13 | * You should have received a copy of the GNU General Public License along |
| 14 | * with this program; if not, write to the Free Software Foundation, Inc., |
| 15 | * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. |
| 16 | * http://www.gnu.org/copyleft/gpl.html |
| 17 | * |
| 18 | * @file |
| 19 | * @ingroup Cache |
| 20 | */ |
| 21 | use Wikimedia\LightweightObjectStore\ExpirationAwareness; |
| 22 | |
| 23 | /** |
| 24 | * Store key-value entries in a size-limited in-memory LRU cache. |
| 25 | * |
| 26 | * The last-modification timestamp of entries is internally tracked so that callers can |
| 27 | * specify the maximum acceptable age of entries in calls to the has() method. As a convenience, |
| 28 | * the hasField(), getField(), and setField() methods can be used for entries that are field/value |
| 29 | * maps themselves; such fields will have their own internally tracked last-modification timestamp. |
| 30 | * |
| 31 | * @ingroup Cache |
| 32 | * @since 1.23 |
| 33 | */ |
| 34 | class MapCacheLRU implements ExpirationAwareness { |
| 35 | /** @var array Map of (key => value) */ |
| 36 | private $cache = []; |
| 37 | /** @var array Map of (key => (UNIX timestamp, (field => UNIX timestamp))) */ |
| 38 | private $timestamps = []; |
| 39 | /** @var float Default entry timestamp if not specified */ |
| 40 | private $epoch; |
| 41 | |
| 42 | /** @var int Max number of entries */ |
| 43 | private $maxCacheKeys; |
| 44 | |
| 45 | /** @var float|null */ |
| 46 | private $wallClockOverride; |
| 47 | |
| 48 | /** @var float */ |
| 49 | private const RANK_TOP = 1.0; |
| 50 | |
| 51 | /** @var int Array key that holds the entry's main timestamp (flat key use) */ |
| 52 | private const SIMPLE = 0; |
| 53 | /** @var int Array key that holds the entry's field timestamps (nested key use) */ |
| 54 | private const FIELDS = 1; |
| 55 | |
| 56 | /** |
| 57 | * @param int $maxKeys Maximum number of entries allowed (min 1) |
| 58 | */ |
| 59 | public function __construct( int $maxKeys ) { |
| 60 | if ( $maxKeys <= 0 ) { |
| 61 | throw new InvalidArgumentException( '$maxKeys must be above zero' ); |
| 62 | } |
| 63 | |
| 64 | $this->maxCacheKeys = $maxKeys; |
| 65 | // Use the current time as the default "as of" timestamp of entries |
| 66 | $this->epoch = $this->getCurrentTime(); |
| 67 | } |
| 68 | |
| 69 | /** |
| 70 | * @param array $values Key/value map in order of increasingly recent access |
| 71 | * @param int $maxKeys |
| 72 | * @return MapCacheLRU |
| 73 | * @since 1.30 |
| 74 | */ |
| 75 | public static function newFromArray( array $values, $maxKeys ) { |
| 76 | $mapCache = new self( $maxKeys ); |
| 77 | $mapCache->cache = ( count( $values ) > $maxKeys ) |
| 78 | ? array_slice( $values, -$maxKeys, null, true ) |
| 79 | : $values; |
| 80 | |
| 81 | return $mapCache; |
| 82 | } |
| 83 | |
| 84 | /** |
| 85 | * @return array Key/value map in order of increasingly recent access |
| 86 | * @since 1.30 |
| 87 | */ |
| 88 | public function toArray() { |
| 89 | return $this->cache; |
| 90 | } |
| 91 | |
| 92 | /** |
| 93 | * Set a key/value pair. |
| 94 | * This will prune the cache if it gets too large based on LRU. |
| 95 | * If the item is already set, it will be pushed to the top of the cache. |
| 96 | * |
| 97 | * To reduce evictions due to one-off use of many new keys, $rank can be |
| 98 | * set to have keys start at the top of a bottom fraction of the list. A value |
| 99 | * of 3/8 means values start at the top of the bottom 3/8s of the list and are |
| 100 | * moved to the top of the list when accessed a second time. |
| 101 | * |
| 102 | * @param string $key |
| 103 | * @param mixed $value |
| 104 | * @param float $rank Bottom fraction of the list where keys start off [default: 1.0] |
| 105 | * @return void |
| 106 | */ |
| 107 | public function set( $key, $value, $rank = self::RANK_TOP ) { |
| 108 | if ( $this->has( $key ) ) { |
| 109 | $this->ping( $key ); |
| 110 | } elseif ( count( $this->cache ) >= $this->maxCacheKeys ) { |
| 111 | $evictKey = array_key_first( $this->cache ); |
| 112 | unset( $this->cache[$evictKey] ); |
| 113 | unset( $this->timestamps[$evictKey] ); |
| 114 | } |
| 115 | |
| 116 | if ( $rank < 1.0 && $rank > 0 ) { |
| 117 | $offset = intval( $rank * count( $this->cache ) ); |
| 118 | $this->cache = array_slice( $this->cache, 0, $offset, true ) |
| 119 | + [ $key => $value ] |
| 120 | + array_slice( $this->cache, $offset, null, true ); |
| 121 | } else { |
| 122 | $this->cache[$key] = $value; |
| 123 | } |
| 124 | |
| 125 | $this->timestamps[$key] = [ |
| 126 | self::SIMPLE => $this->getCurrentTime(), |
| 127 | self::FIELDS => [] |
| 128 | ]; |
| 129 | } |
| 130 | |
| 131 | /** |
| 132 | * Check if a key exists |
| 133 | * |
| 134 | * @param string|int $key |
| 135 | * @param float $maxAge Ignore items older than this many seconds [default: INF] |
| 136 | * @return bool |
| 137 | * @since 1.32 Added $maxAge |
| 138 | */ |
| 139 | public function has( $key, $maxAge = INF ) { |
| 140 | if ( !is_int( $key ) && !is_string( $key ) ) { |
| 141 | throw new UnexpectedValueException( |
| 142 | __METHOD__ . ': invalid key; must be string or integer.' ); |
| 143 | } |
| 144 | return array_key_exists( $key, $this->cache ) |
| 145 | && ( |
| 146 | // Optimization: Avoid expensive getAge/getCurrentTime for common case (T275673) |
| 147 | $maxAge === INF |
| 148 | || $maxAge <= 0 |
| 149 | || $this->getKeyAge( $key ) <= $maxAge |
| 150 | ); |
| 151 | } |
| 152 | |
| 153 | /** |
| 154 | * Get the value for a key. |
| 155 | * This returns null if the key is not set. |
| 156 | * If the item is already set, it will be pushed to the top of the cache. |
| 157 | * |
| 158 | * @param string $key |
| 159 | * @param float $maxAge Ignore items older than this many seconds [default: INF] |
| 160 | * @param mixed|null $default Value to return if no key is found [default: null] |
| 161 | * @return mixed Returns $default if the key was not found or is older than $maxAge |
| 162 | * @since 1.32 Added $maxAge |
| 163 | * @since 1.34 Added $default |
| 164 | * |
| 165 | * Although sometimes this can be tainted, taint-check doesn't distinguish separate instances |
| 166 | * of MapCacheLRU, so assume untainted to cut down on false positives. See T272134. |
| 167 | * @return-taint none |
| 168 | */ |
| 169 | public function get( $key, $maxAge = INF, $default = null ) { |
| 170 | if ( !$this->has( $key, $maxAge ) ) { |
| 171 | return $default; |
| 172 | } |
| 173 | |
| 174 | $this->ping( $key ); |
| 175 | |
| 176 | return $this->cache[$key]; |
| 177 | } |
| 178 | |
| 179 | /** |
| 180 | * @param string|int $key |
| 181 | * @param string|int $field |
| 182 | * @param mixed $value |
| 183 | * @param float $initRank |
| 184 | */ |
| 185 | public function setField( $key, $field, $value, $initRank = self::RANK_TOP ) { |
| 186 | if ( $this->has( $key ) ) { |
| 187 | $this->ping( $key ); |
| 188 | |
| 189 | if ( !is_array( $this->cache[$key] ) ) { |
| 190 | $type = gettype( $this->cache[$key] ); |
| 191 | throw new UnexpectedValueException( "Cannot add field to non-array value ('$key' is $type)" ); |
| 192 | } |
| 193 | } else { |
| 194 | $this->set( $key, [], $initRank ); |
| 195 | } |
| 196 | |
| 197 | if ( !is_string( $field ) && !is_int( $field ) ) { |
| 198 | throw new UnexpectedValueException( |
| 199 | __METHOD__ . ": invalid field for '$key'; must be string or integer." ); |
| 200 | } |
| 201 | |
| 202 | $this->cache[$key][$field] = $value; |
| 203 | $this->timestamps[$key][self::FIELDS][$field] = $this->getCurrentTime(); |
| 204 | } |
| 205 | |
| 206 | /** |
| 207 | * @param string|int $key |
| 208 | * @param string|int $field |
| 209 | * @param float $maxAge Ignore items older than this many seconds [default: INF] |
| 210 | * @return bool |
| 211 | * @since 1.32 Added $maxAge |
| 212 | */ |
| 213 | public function hasField( $key, $field, $maxAge = INF ) { |
| 214 | $value = $this->get( $key ); |
| 215 | |
| 216 | if ( !is_int( $field ) && !is_string( $field ) ) { |
| 217 | throw new UnexpectedValueException( |
| 218 | __METHOD__ . ": invalid field for '$key'; must be string or integer." ); |
| 219 | } |
| 220 | return is_array( $value ) |
| 221 | && array_key_exists( $field, $value ) |
| 222 | && ( |
| 223 | $maxAge === INF |
| 224 | || $maxAge <= 0 |
| 225 | || $this->getKeyFieldAge( $key, $field ) <= $maxAge |
| 226 | ); |
| 227 | } |
| 228 | |
| 229 | /** |
| 230 | * @param string|int $key |
| 231 | * @param string|int $field |
| 232 | * @param float $maxAge Ignore items older than this many seconds [default: INF] |
| 233 | * @return mixed Returns null if the key was not found or is older than $maxAge |
| 234 | * @since 1.32 Added $maxAge |
| 235 | */ |
| 236 | public function getField( $key, $field, $maxAge = INF ) { |
| 237 | if ( !$this->hasField( $key, $field, $maxAge ) ) { |
| 238 | return null; |
| 239 | } |
| 240 | |
| 241 | return $this->cache[$key][$field]; |
| 242 | } |
| 243 | |
| 244 | /** |
| 245 | * @return array |
| 246 | * @since 1.25 |
| 247 | */ |
| 248 | public function getAllKeys() { |
| 249 | return array_keys( $this->cache ); |
| 250 | } |
| 251 | |
| 252 | /** |
| 253 | * Get an item with the given key, producing and setting it if not found. |
| 254 | * |
| 255 | * If the callback returns false, then nothing is stored. |
| 256 | * |
| 257 | * @since 1.28 |
| 258 | * @param string $key |
| 259 | * @param callable $callback Callback that will produce the value |
| 260 | * @param float $rank Bottom fraction of the list where keys start off [default: 1.0] |
| 261 | * @param float $maxAge Ignore items older than this many seconds [default: INF] |
| 262 | * @return mixed The cached value if found or the result of $callback otherwise |
| 263 | * @since 1.32 Added $maxAge |
| 264 | */ |
| 265 | public function getWithSetCallback( |
| 266 | $key, callable $callback, $rank = self::RANK_TOP, $maxAge = INF |
| 267 | ) { |
| 268 | if ( $this->has( $key, $maxAge ) ) { |
| 269 | $value = $this->get( $key ); |
| 270 | } else { |
| 271 | $value = $callback(); |
| 272 | if ( $value !== false ) { |
| 273 | $this->set( $key, $value, $rank ); |
| 274 | } |
| 275 | } |
| 276 | |
| 277 | return $value; |
| 278 | } |
| 279 | |
| 280 | /** |
| 281 | * Format a cache key string |
| 282 | * |
| 283 | * @since 1.41 |
| 284 | * @param string|int ...$components Key components |
| 285 | * @return string |
| 286 | */ |
| 287 | public function makeKey( ...$components ) { |
| 288 | // Based on BagOStuff::makeKeyInternal, except without a required |
| 289 | // $keygroup prefix. While MapCacheLRU can and is used as cache for |
| 290 | // multiple groups of keys, it is equally common for the instance itself |
| 291 | // to represent a single group, and thus have keys where the first component |
| 292 | // can directly be a user-controlled variable. |
| 293 | $key = ''; |
| 294 | foreach ( $components as $i => $component ) { |
| 295 | if ( $i > 0 ) { |
| 296 | $key .= ':'; |
| 297 | } |
| 298 | $key .= strtr( $component, [ '%' => '%25', ':' => '%3A' ] ); |
| 299 | } |
| 300 | return $key; |
| 301 | } |
| 302 | |
| 303 | /** |
| 304 | * Clear one or several cache entries, or all cache entries |
| 305 | * |
| 306 | * @param string|int|array|null $keys |
| 307 | * @return void |
| 308 | */ |
| 309 | public function clear( $keys = null ) { |
| 310 | if ( func_num_args() == 0 ) { |
| 311 | $this->cache = []; |
| 312 | $this->timestamps = []; |
| 313 | } else { |
| 314 | foreach ( (array)$keys as $key ) { |
| 315 | unset( $this->cache[$key] ); |
| 316 | unset( $this->timestamps[$key] ); |
| 317 | } |
| 318 | } |
| 319 | } |
| 320 | |
| 321 | /** |
| 322 | * Get the maximum number of keys allowed |
| 323 | * |
| 324 | * @return int |
| 325 | * @since 1.32 |
| 326 | */ |
| 327 | public function getMaxSize() { |
| 328 | return $this->maxCacheKeys; |
| 329 | } |
| 330 | |
| 331 | /** |
| 332 | * Resize the maximum number of cache entries, removing older entries as needed |
| 333 | * |
| 334 | * @param int $maxKeys Maximum number of entries allowed (min 1) |
| 335 | * @return void |
| 336 | * @since 1.32 |
| 337 | */ |
| 338 | public function setMaxSize( int $maxKeys ) { |
| 339 | if ( $maxKeys <= 0 ) { |
| 340 | throw new InvalidArgumentException( '$maxKeys must be above zero' ); |
| 341 | } |
| 342 | |
| 343 | $this->maxCacheKeys = $maxKeys; |
| 344 | while ( count( $this->cache ) > $this->maxCacheKeys ) { |
| 345 | $evictKey = array_key_first( $this->cache ); |
| 346 | unset( $this->cache[$evictKey] ); |
| 347 | unset( $this->timestamps[$evictKey] ); |
| 348 | } |
| 349 | } |
| 350 | |
| 351 | /** |
| 352 | * Push an entry to the top of the cache |
| 353 | * |
| 354 | * @param string $key |
| 355 | */ |
| 356 | private function ping( $key ) { |
| 357 | $item = $this->cache[$key]; |
| 358 | unset( $this->cache[$key] ); |
| 359 | $this->cache[$key] = $item; |
| 360 | } |
| 361 | |
| 362 | /** |
| 363 | * @param string|int $key |
| 364 | * @return float UNIX timestamp; the age of the given entry |
| 365 | */ |
| 366 | private function getKeyAge( $key ) { |
| 367 | $mtime = $this->timestamps[$key][self::SIMPLE] ?? $this->epoch; |
| 368 | |
| 369 | return ( $this->getCurrentTime() - $mtime ); |
| 370 | } |
| 371 | |
| 372 | /** |
| 373 | * @param string|int $key |
| 374 | * @param string|int|null $field |
| 375 | * @return float UNIX timestamp; the age of the given entry field |
| 376 | */ |
| 377 | private function getKeyFieldAge( $key, $field ) { |
| 378 | $mtime = $this->timestamps[$key][self::FIELDS][$field] ?? $this->epoch; |
| 379 | |
| 380 | return ( $this->getCurrentTime() - $mtime ); |
| 381 | } |
| 382 | |
| 383 | public function __serialize() { |
| 384 | return [ |
| 385 | 'entries' => $this->cache, |
| 386 | 'timestamps' => $this->timestamps, |
| 387 | 'maxCacheKeys' => $this->maxCacheKeys, |
| 388 | ]; |
| 389 | } |
| 390 | |
| 391 | public function __unserialize( $data ) { |
| 392 | $this->cache = $data['entries'] ?? []; |
| 393 | $this->timestamps = $data['timestamps'] ?? []; |
| 394 | // Fallback needed for serializations prior to T218511 |
| 395 | $this->maxCacheKeys = $data['maxCacheKeys'] ?? ( count( $this->cache ) + 1 ); |
| 396 | $this->epoch = $this->getCurrentTime(); |
| 397 | } |
| 398 | |
| 399 | /** |
| 400 | * @return float UNIX timestamp |
| 401 | * @codeCoverageIgnore |
| 402 | */ |
| 403 | protected function getCurrentTime() { |
| 404 | return $this->wallClockOverride ?: microtime( true ); |
| 405 | } |
| 406 | |
| 407 | /** |
| 408 | * @param float|null &$time Mock UNIX timestamp for testing |
| 409 | * @codeCoverageIgnore |
| 410 | */ |
| 411 | public function setMockTime( &$time ) { |
| 412 | $this->wallClockOverride =& $time; |
| 413 | } |
| 414 | } |