3 * Per-process memory cache for storing items.
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License as published by
7 * the Free Software Foundation; either version 2 of the License, or
8 * (at your option) any later version.
10 * This program is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 * GNU General Public License for more details.
15 * You should have received a copy of the GNU General Public License along
16 * with this program; if not, write to the Free Software Foundation, Inc.,
17 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
18 * http://www.gnu.org/copyleft/gpl.html
23 use Wikimedia\Assert\Assert
;
26 * Handles a simple LRU key/value map with a maximum number of entries
28 * The last-modification timestamp of entries is internally tracked so that callers can
29 * specify the maximum acceptable age of entries in calls to the has() method. As a convenience,
30 * the hasField(), getField(), and setField() methods can be used for entries that are field/value
31 * maps themselves; such fields will have their own internally tracked last-modification timestamp.
33 * @see ProcessCacheLRU
37 class MapCacheLRU
implements IExpiringStore
, Serializable
{
38 /** @var array Map of (key => value) */
40 /** @var array Map of (key => (UNIX timestamp, (field => UNIX timestamp))) */
41 private $timestamps = [];
42 /** @var float Default entry timestamp if not specified */
45 /** @var int Max number of entries */
46 private $maxCacheKeys;
48 /** @var float|null */
49 private $wallClockOverride;
53 /** @var int Array key that holds the entry's main timestamp (flat key use) */
55 /** @var int Array key that holds the entry's field timestamps (nested key use) */
59 * @param int $maxKeys Maximum number of entries allowed (min 1)
60 * @throws Exception When $maxKeys is not an int or not above zero
62 public function __construct( $maxKeys ) {
63 Assert
::parameterType( 'integer', $maxKeys, '$maxKeys' );
64 Assert
::parameter( $maxKeys > 0, '$maxKeys', 'must be above zero' );
66 $this->maxCacheKeys
= $maxKeys;
67 // Use the current time as the default "as of" timesamp of entries
68 $this->epoch
= $this->getCurrentTime();
72 * @param array $values Key/value map in order of increasingly recent access
77 public static function newFromArray( array $values, $maxKeys ) {
78 $mapCache = new self( $maxKeys );
79 $mapCache->cache
= ( count( $values ) > $maxKeys )
80 ?
array_slice( $values, -$maxKeys, null, true )
87 * @return array Key/value map in order of increasingly recent access
90 public function toArray() {
95 * Set a key/value pair.
96 * This will prune the cache if it gets too large based on LRU.
97 * If the item is already set, it will be pushed to the top of the cache.
99 * To reduce evictions due to one-off use of many new keys, $rank can be
100 * set to have keys start at the top of a bottom fraction of the list. A value
101 * of 3/8 means values start at the top of the bottom 3/8s of the list and are
102 * moved to the top of the list when accessed a second time.
105 * @param mixed $value
106 * @param float $rank Bottom fraction of the list where keys start off [Default: 1.0]
109 public function set( $key, $value, $rank = self
::RANK_TOP
) {
110 if ( $this->has( $key ) ) {
112 } elseif ( count( $this->cache
) >= $this->maxCacheKeys
) {
113 reset( $this->cache
);
114 $evictKey = key( $this->cache
);
115 unset( $this->cache
[$evictKey] );
116 unset( $this->timestamps
[$evictKey] );
119 if ( $rank < 1.0 && $rank > 0 ) {
120 $offset = intval( $rank * count( $this->cache
) );
121 $this->cache
= array_slice( $this->cache
, 0, $offset, true )
123 +
array_slice( $this->cache
, $offset, null, true );
125 $this->cache
[$key] = $value;
128 $this->timestamps
[$key] = [
129 self
::SIMPLE
=> $this->getCurrentTime(),
135 * Check if a key exists
138 * @param float $maxAge Ignore items older than this many seconds (since 1.32)
141 public function has( $key, $maxAge = 0.0 ) {
142 if ( !is_int( $key ) && !is_string( $key ) ) {
143 throw new UnexpectedValueException(
144 __METHOD__
. ' called with invalid key. Must be string or integer.' );
147 if ( !array_key_exists( $key, $this->cache
) ) {
151 return ( $maxAge <= 0 ||
$this->getAge( $key ) <= $maxAge );
155 * Get the value for a key.
156 * This returns null if the key is not set.
157 * If the item is already set, it will be pushed to the top of the cache.
160 * @return mixed Returns null if the key was not found
162 public function get( $key ) {
163 if ( !$this->has( $key ) ) {
169 return $this->cache
[$key];
173 * @param string|int $key
174 * @param string|int $field
175 * @param mixed $value
176 * @param float $initRank
178 public function setField( $key, $field, $value, $initRank = self
::RANK_TOP
) {
179 if ( $this->has( $key ) ) {
182 $this->set( $key, [], $initRank );
185 if ( !is_array( $this->cache
[$key] ) ) {
186 throw new UnexpectedValueException( "The value of '$key' is not an array." );
189 $this->cache
[$key][$field] = $value;
190 $this->timestamps
[$key][self
::FIELDS
][$field] = $this->getCurrentTime();
194 * @param string|int $key
195 * @param string|int $field
196 * @param float $maxAge
199 public function hasField( $key, $field, $maxAge = 0.0 ) {
200 $value = $this->get( $key );
201 if ( !is_array( $value ) ||
!array_key_exists( $field, $value ) ) {
205 return ( $maxAge <= 0 ||
$this->getAge( $key, $field ) <= $maxAge );
208 public function getField( $key, $field ) {
209 return $this->get( $key )[$field] ??
null;
216 public function getAllKeys() {
217 return array_keys( $this->cache
);
221 * Get an item with the given key, producing and setting it if not found.
223 * If the callback returns false, then nothing is stored.
227 * @param callable $callback Callback that will produce the value
228 * @param float $rank Bottom fraction of the list where keys start off [Default: 1.0]
229 * @param float $maxAge Ignore items older than this many seconds [Default: 0.0] (since 1.32)
230 * @return mixed The cached value if found or the result of $callback otherwise
232 public function getWithSetCallback(
233 $key, callable
$callback, $rank = self
::RANK_TOP
, $maxAge = 0.0
235 if ( $this->has( $key, $maxAge ) ) {
236 $value = $this->get( $key );
238 $value = call_user_func( $callback );
239 if ( $value !== false ) {
240 $this->set( $key, $value, $rank );
248 * Clear one or several cache entries, or all cache entries
250 * @param string|array|null $keys
253 public function clear( $keys = null ) {
254 if ( func_num_args() == 0 ) {
256 $this->timestamps
= [];
258 foreach ( (array)$keys as $key ) {
259 unset( $this->cache
[$key] );
260 unset( $this->timestamps
[$key] );
266 * Get the maximum number of keys allowed
271 public function getMaxSize() {
272 return $this->maxCacheKeys
;
276 * Resize the maximum number of cache entries, removing older entries as needed
278 * @param int $maxKeys Maximum number of entries allowed (min 1)
280 * @throws Exception When $maxKeys is not an int or not above zero
283 public function setMaxSize( $maxKeys ) {
284 Assert
::parameterType( 'integer', $maxKeys, '$maxKeys' );
285 Assert
::parameter( $maxKeys > 0, '$maxKeys', 'must be above zero' );
287 $this->maxCacheKeys
= $maxKeys;
288 while ( count( $this->cache
) > $this->maxCacheKeys
) {
289 reset( $this->cache
);
290 $evictKey = key( $this->cache
);
291 unset( $this->cache
[$evictKey] );
292 unset( $this->timestamps
[$evictKey] );
297 * Push an entry to the top of the cache
301 private function ping( $key ) {
302 $item = $this->cache
[$key];
303 unset( $this->cache
[$key] );
304 $this->cache
[$key] = $item;
308 * @param string|int $key
309 * @param string|int|null $field [optional]
310 * @return float UNIX timestamp; the age of the given entry or entry field
312 private function getAge( $key, $field = null ) {
313 if ( $field !== null ) {
314 $mtime = $this->timestamps
[$key][self
::FIELDS
][$field] ??
$this->epoch
;
316 $mtime = $this->timestamps
[$key][self
::SIMPLE
] ??
$this->epoch
;
319 return ( $this->getCurrentTime() - $mtime );
322 public function serialize() {
324 'entries' => $this->cache
,
325 'timestamps' => $this->timestamps
329 public function unserialize( $serialized ) {
330 $data = unserialize( $serialized );
331 $this->cache
= $data['entries'] ??
[];
332 $this->timestamps
= $data['timestamps'] ??
[];
333 $this->epoch
= $this->getCurrentTime();
337 * @return float UNIX timestamp
338 * @codeCoverageIgnore
340 protected function getCurrentTime() {
341 return $this->wallClockOverride ?
: microtime( true );
345 * @param float|null &$time Mock UNIX timestamp for testing
346 * @codeCoverageIgnore
348 public function setMockTime( &$time ) {
349 $this->wallClockOverride
=& $time;