includes/libs/objectcache/BagOStuff.php

   1 <?php
   2 /**
   3  * Classes to cache objects in PHP accelerators, SQL database or DBA files
   4  *
   5  * Copyright © 2003-2004 Brion Vibber <brion@pobox.com>
   6  * https://www.mediawiki.org/
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License as published by
  10  * the Free Software Foundation; either version 2 of the License, or
  11  * (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License along
  19  * with this program; if not, write to the Free Software Foundation, Inc.,
  20  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  21  * http://www.gnu.org/copyleft/gpl.html
  22  *
  23  * @file
  24  * @ingroup Cache
  25  */
  26
  27 /**
  28  * @defgroup Cache Cache
  29  */
  30
  31 use Psr\Log\LoggerAwareInterface;
  32 use Psr\Log\LoggerInterface;
  33 use Psr\Log\NullLogger;
  34
  35 /**
  36  * interface is intended to be more or less compatible with
  37  * the PHP memcached client.
  38  *
  39  * backends for local hash array and SQL table included:
  40  * <code>
  41  *   $bag = new HashBagOStuff();
  42  *   $bag = new SqlBagOStuff(); # connect to db first
  43  * </code>
  44  *
  45  * @ingroup Cache
  46  */
  47 abstract class BagOStuff implements LoggerAwareInterface {
  48         private $debugMode = false;
  49
  50         protected $lastError = self::ERR_NONE;
  51
  52         /**
  53          * @var LoggerInterface
  54          */
  55         protected $logger;
  56
  57         /** Possible values for getLastError() */
  58         const ERR_NONE = 0; // no error
  59         const ERR_NO_RESPONSE = 1; // no response
  60         const ERR_UNREACHABLE = 2; // can't connect
  61         const ERR_UNEXPECTED = 3; // response gave some error
  62
  63         public function __construct( array $params = array() ) {
  64                 if ( isset( $params['logger'] ) ) {
  65                         $this->setLogger( $params['logger'] );
  66                 } else {
  67                         $this->setLogger( new NullLogger() );
  68                 }
  69         }
  70
  71         /**
  72          * @param LoggerInterface $logger
  73          * @return null
  74          */
  75         public function setLogger( LoggerInterface $logger ) {
  76                 $this->logger = $logger;
  77         }
  78
  79         /**
  80          * @param bool $bool
  81          */
  82         public function setDebug( $bool ) {
  83                 $this->debugMode = $bool;
  84         }
  85
  86         /**
  87          * Get an item with the given key. Returns false if it does not exist.
  88          * @param string $key
  89          * @param mixed $casToken [optional]
  90          * @return mixed Returns false on failure
  91          */
  92         abstract public function get( $key, &$casToken = null );
  93
  94         /**
  95          * Set an item.
  96          * @param string $key
  97          * @param mixed $value
  98          * @param int $exptime Either an interval in seconds or a unix timestamp for expiry
  99          * @return bool Success
 100          */
 101         abstract public function set( $key, $value, $exptime = 0 );
 102
 103         /**
 104          * Delete an item.
 105          * @param string $key
 106          * @return bool True if the item was deleted or not found, false on failure
 107          */
 108         abstract public function delete( $key );
 109
 110         /**
 111          * Merge changes into the existing cache value (possibly creating a new one).
 112          * The callback function returns the new value given the current value (possibly false),
 113          * and takes the arguments: (this BagOStuff object, cache key, current value).
 114          *
 115          * @param string $key
 116          * @param callable $callback Callback method to be executed
 117          * @param int $exptime Either an interval in seconds or a unix timestamp for expiry
 118          * @param int $attempts The amount of times to attempt a merge in case of failure
 119          * @return bool Success
 120          */
 121         public function merge( $key, $callback, $exptime = 0, $attempts = 10 ) {
 122                 if ( !is_callable( $callback ) ) {
 123                         throw new Exception( "Got invalid callback." );
 124                 }
 125
 126                 return $this->mergeViaLock( $key, $callback, $exptime, $attempts );
 127         }
 128
 129         /**
 130          * @see BagOStuff::merge()
 131          *
 132          * @param string $key
 133          * @param callable $callback Callback method to be executed
 134          * @param int $exptime Either an interval in seconds or a unix timestamp for expiry
 135          * @param int $attempts The amount of times to attempt a merge in case of failure
 136          * @return bool Success
 137          */
 138         protected function mergeViaCas( $key, $callback, $exptime = 0, $attempts = 10 ) {
 139                 do {
 140                         $casToken = null; // passed by reference
 141                         $currentValue = $this->get( $key, $casToken );
 142                         // Derive the new value from the old value
 143                         $value = call_user_func( $callback, $this, $key, $currentValue );
 144
 145                         if ( $value === false ) {
 146                                 $success = true; // do nothing
 147                         } elseif ( $currentValue === false ) {
 148                                 // Try to create the key, failing if it gets created in the meantime
 149                                 $success = $this->add( $key, $value, $exptime );
 150                         } else {
 151                                 // Try to update the key, failing if it gets changed in the meantime
 152                                 $success = $this->cas( $casToken, $key, $value, $exptime );
 153                         }
 154                 } while ( !$success && --$attempts );
 155
 156                 return $success;
 157         }
 158
 159         /**
 160          * Check and set an item
 161          *
 162          * @param mixed $casToken
 163          * @param string $key
 164          * @param mixed $value
 165          * @param int $exptime Either an interval in seconds or a unix timestamp for expiry
 166          * @return bool Success
 167          */
 168         protected function cas( $casToken, $key, $value, $exptime = 0 ) {
 169                 throw new Exception( "CAS is not implemented in " . __CLASS__ );
 170         }
 171
 172         /**
 173          * @see BagOStuff::merge()
 174          *
 175          * @param string $key
 176          * @param callable $callback Callback method to be executed
 177          * @param int $exptime Either an interval in seconds or a unix timestamp for expiry
 178          * @param int $attempts The amount of times to attempt a merge in case of failure
 179          * @return bool Success
 180          */
 181         protected function mergeViaLock( $key, $callback, $exptime = 0, $attempts = 10 ) {
 182                 if ( !$this->lock( $key, 6 ) ) {
 183                         return false;
 184                 }
 185
 186                 $currentValue = $this->get( $key );
 187                 // Derive the new value from the old value
 188                 $value = call_user_func( $callback, $this, $key, $currentValue );
 189
 190                 if ( $value === false ) {
 191                         $success = true; // do nothing
 192                 } else {
 193                         $success = $this->set( $key, $value, $exptime ); // set the new value
 194                 }
 195
 196                 if ( !$this->unlock( $key ) ) {
 197                         // this should never happen
 198                         trigger_error( "Could not release lock for key '$key'." );
 199                 }
 200
 201                 return $success;
 202         }
 203
 204         /**
 205          * @param string $key
 206          * @param int $timeout Lock wait timeout [optional]
 207          * @param int $expiry Lock expiry [optional]
 208          * @return bool Success
 209          */
 210         public function lock( $key, $timeout = 6, $expiry = 6 ) {
 211                 $this->clearLastError();
 212                 $timestamp = microtime( true ); // starting UNIX timestamp
 213                 if ( $this->add( "{$key}:lock", 1, $expiry ) ) {
 214                         return true;
 215                 } elseif ( $this->getLastError() ) {
 216                         return false;
 217                 }
 218
 219                 $uRTT = ceil( 1e6 * ( microtime( true ) - $timestamp ) ); // estimate RTT (us)
 220                 $sleep = 2 * $uRTT; // rough time to do get()+set()
 221
 222                 $locked = false; // lock acquired
 223                 $attempts = 0; // failed attempts
 224                 do {
 225                         if ( ++$attempts >= 3 && $sleep <= 5e5 ) {
 226                                 // Exponentially back off after failed attempts to avoid network spam.
 227                                 // About 2*$uRTT*(2^n-1) us of "sleep" happen for the next n attempts.
 228                                 $sleep *= 2;
 229                         }
 230                         usleep( $sleep ); // back off
 231                         $this->clearLastError();
 232                         $locked = $this->add( "{$key}:lock", 1, $expiry );
 233                         if ( $this->getLastError() ) {
 234                                 return false;
 235                         }
 236                 } while ( !$locked && ( microtime( true ) - $timestamp ) < $timeout );
 237
 238                 return $locked;
 239         }
 240
 241         /**
 242          * @param string $key
 243          * @return bool Success
 244          */
 245         public function unlock( $key ) {
 246                 return $this->delete( "{$key}:lock" );
 247         }
 248
 249         /**
 250          * Delete all objects expiring before a certain date.
 251          * @param string $date The reference date in MW format
 252          * @param callable|bool $progressCallback Optional, a function which will be called
 253          *     regularly during long-running operations with the percentage progress
 254          *     as the first parameter.
 255          *
 256          * @return bool Success, false if unimplemented
 257          */
 258         public function deleteObjectsExpiringBefore( $date, $progressCallback = false ) {
 259                 // stub
 260                 return false;
 261         }
 262
 263         /* *** Emulated functions *** */
 264
 265         /**
 266          * Get an associative array containing the item for each of the keys that have items.
 267          * @param array $keys List of strings
 268          * @return array
 269          */
 270         public function getMulti( array $keys ) {
 271                 $res = array();
 272                 foreach ( $keys as $key ) {
 273                         $val = $this->get( $key );
 274                         if ( $val !== false ) {
 275                                 $res[$key] = $val;
 276                         }
 277                 }
 278                 return $res;
 279         }
 280
 281         /**
 282          * Batch insertion
 283          * @param array $data $key => $value assoc array
 284          * @param int $exptime Either an interval in seconds or a unix timestamp for expiry
 285          * @return bool Success
 286          * @since 1.24
 287          */
 288         public function setMulti( array $data, $exptime = 0 ) {
 289                 $res = true;
 290                 foreach ( $data as $key => $value ) {
 291                         if ( !$this->set( $key, $value, $exptime ) ) {
 292                                 $res = false;
 293                         }
 294                 }
 295                 return $res;
 296         }
 297
 298         /**
 299          * @param string $key
 300          * @param mixed $value
 301          * @param int $exptime
 302          * @return bool Success
 303          */
 304         public function add( $key, $value, $exptime = 0 ) {
 305                 if ( $this->get( $key ) === false ) {
 306                         return $this->set( $key, $value, $exptime );
 307                 }
 308                 return false; // key already set
 309         }
 310
 311         /**
 312          * Increase stored value of $key by $value while preserving its TTL
 313          * @param string $key Key to increase
 314          * @param int $value Value to add to $key (Default 1)
 315          * @return int|bool New value or false on failure
 316          */
 317         public function incr( $key, $value = 1 ) {
 318                 if ( !$this->lock( $key ) ) {
 319                         return false;
 320                 }
 321                 $n = $this->get( $key );
 322                 if ( $this->isInteger( $n ) ) { // key exists?
 323                         $n += intval( $value );
 324                         $this->set( $key, max( 0, $n ) ); // exptime?
 325                 } else {
 326                         $n = false;
 327                 }
 328                 $this->unlock( $key );
 329
 330                 return $n;
 331         }
 332
 333         /**
 334          * Decrease stored value of $key by $value while preserving its TTL
 335          * @param string $key
 336          * @param int $value
 337          * @return int
 338          */
 339         public function decr( $key, $value = 1 ) {
 340                 return $this->incr( $key, - $value );
 341         }
 342
 343         /**
 344          * Increase stored value of $key by $value while preserving its TTL
 345          *
 346          * This will create the key with value $init and TTL $ttl if not present
 347          *
 348          * @param string $key
 349          * @param int $ttl
 350          * @param int $value
 351          * @param int $init
 352          * @return bool
 353          * @since 1.24
 354          */
 355         public function incrWithInit( $key, $ttl, $value = 1, $init = 1 ) {
 356                 return $this->incr( $key, $value ) ||
 357                         $this->add( $key, (int)$init, $ttl ) || $this->incr( $key, $value );
 358         }
 359
 360         /**
 361          * Get the "last error" registered; clearLastError() should be called manually
 362          * @return int ERR_* constant for the "last error" registry
 363          * @since 1.23
 364          */
 365         public function getLastError() {
 366                 return $this->lastError;
 367         }
 368
 369         /**
 370          * Clear the "last error" registry
 371          * @since 1.23
 372          */
 373         public function clearLastError() {
 374                 $this->lastError = self::ERR_NONE;
 375         }
 376
 377         /**
 378          * Set the "last error" registry
 379          * @param int $err ERR_* constant
 380          * @since 1.23
 381          */
 382         protected function setLastError( $err ) {
 383                 $this->lastError = $err;
 384         }
 385
 386         /**
 387          * @param string $text
 388          */
 389         protected function debug( $text ) {
 390                 if ( $this->debugMode ) {
 391                         $this->logger->debug( "{class} debug: $text", array(
 392                                 'class' => get_class( $this ),
 393                         ) );
 394                 }
 395         }
 396
 397         /**
 398          * Convert an optionally relative time to an absolute time
 399          * @param int $exptime
 400          * @return int
 401          */
 402         protected function convertExpiry( $exptime ) {
 403                 if ( ( $exptime != 0 ) && ( $exptime < 86400 * 3650 /* 10 years */ ) ) {
 404                         return time() + $exptime;
 405                 } else {
 406                         return $exptime;
 407                 }
 408         }
 409
 410         /**
 411          * Convert an optionally absolute expiry time to a relative time. If an
 412          * absolute time is specified which is in the past, use a short expiry time.
 413          *
 414          * @param int $exptime
 415          * @return int
 416          */
 417         protected function convertToRelative( $exptime ) {
 418                 if ( $exptime >= 86400 * 3650 /* 10 years */ ) {
 419                         $exptime -= time();
 420                         if ( $exptime <= 0 ) {
 421                                 $exptime = 1;
 422                         }
 423                         return $exptime;
 424                 } else {
 425                         return $exptime;
 426                 }
 427         }
 428
 429         /**
 430          * Check if a value is an integer
 431          *
 432          * @param mixed $value
 433          * @return bool
 434          */
 435         protected function isInteger( $value ) {
 436                 return ( is_int( $value ) || ctype_digit( $value ) );
 437         }
 438 }