includes/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->mergeViaCas( $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          * @param mixed $casToken
 162          * @param string $key
 163          * @param mixed $value
 164          * @param int $exptime Either an interval in seconds or a unix timestamp for expiry
 165          * @return bool Success
 166          */
 167         abstract protected function cas( $casToken, $key, $value, $exptime = 0 );
 168
 169         /**
 170          * @see BagOStuff::merge()
 171          *
 172          * @param string $key
 173          * @param callable $callback Callback method to be executed
 174          * @param int $exptime Either an interval in seconds or a unix timestamp for expiry
 175          * @param int $attempts The amount of times to attempt a merge in case of failure
 176          * @return bool Success
 177          */
 178         protected function mergeViaLock( $key, $callback, $exptime = 0, $attempts = 10 ) {
 179                 if ( !$this->lock( $key, 6 ) ) {
 180                         return false;
 181                 }
 182
 183                 $currentValue = $this->get( $key );
 184                 // Derive the new value from the old value
 185                 $value = call_user_func( $callback, $this, $key, $currentValue );
 186
 187                 if ( $value === false ) {
 188                         $success = true; // do nothing
 189                 } else {
 190                         $success = $this->set( $key, $value, $exptime ); // set the new value
 191                 }
 192
 193                 if ( !$this->unlock( $key ) ) {
 194                         // this should never happen
 195                         trigger_error( "Could not release lock for key '$key'." );
 196                 }
 197
 198                 return $success;
 199         }
 200
 201         /**
 202          * @param string $key
 203          * @param int $timeout Lock wait timeout [optional]
 204          * @param int $expiry Lock expiry [optional]
 205          * @return bool Success
 206          */
 207         public function lock( $key, $timeout = 6, $expiry = 6 ) {
 208                 $this->clearLastError();
 209                 $timestamp = microtime( true ); // starting UNIX timestamp
 210                 if ( $this->add( "{$key}:lock", 1, $expiry ) ) {
 211                         return true;
 212                 } elseif ( $this->getLastError() ) {
 213                         return false;
 214                 }
 215
 216                 $uRTT = ceil( 1e6 * ( microtime( true ) - $timestamp ) ); // estimate RTT (us)
 217                 $sleep = 2 * $uRTT; // rough time to do get()+set()
 218
 219                 $locked = false; // lock acquired
 220                 $attempts = 0; // failed attempts
 221                 do {
 222                         if ( ++$attempts >= 3 && $sleep <= 5e5 ) {
 223                                 // Exponentially back off after failed attempts to avoid network spam.
 224                                 // About 2*$uRTT*(2^n-1) us of "sleep" happen for the next n attempts.
 225                                 $sleep *= 2;
 226                         }
 227                         usleep( $sleep ); // back off
 228                         $this->clearLastError();
 229                         $locked = $this->add( "{$key}:lock", 1, $expiry );
 230                         if ( $this->getLastError() ) {
 231                                 return false;
 232                         }
 233                 } while ( !$locked && ( microtime( true ) - $timestamp ) < $timeout );
 234
 235                 return $locked;
 236         }
 237
 238         /**
 239          * @param string $key
 240          * @return bool Success
 241          */
 242         public function unlock( $key ) {
 243                 return $this->delete( "{$key}:lock" );
 244         }
 245
 246         /**
 247          * Delete all objects expiring before a certain date.
 248          * @param string $date The reference date in MW format
 249          * @param callable|bool $progressCallback Optional, a function which will be called
 250          *     regularly during long-running operations with the percentage progress
 251          *     as the first parameter.
 252          *
 253          * @return bool Success, false if unimplemented
 254          */
 255         public function deleteObjectsExpiringBefore( $date, $progressCallback = false ) {
 256                 // stub
 257                 return false;
 258         }
 259
 260         /* *** Emulated functions *** */
 261
 262         /**
 263          * Get an associative array containing the item for each of the keys that have items.
 264          * @param array $keys List of strings
 265          * @return array
 266          */
 267         public function getMulti( array $keys ) {
 268                 $res = array();
 269                 foreach ( $keys as $key ) {
 270                         $val = $this->get( $key );
 271                         if ( $val !== false ) {
 272                                 $res[$key] = $val;
 273                         }
 274                 }
 275                 return $res;
 276         }
 277
 278         /**
 279          * Batch insertion
 280          * @param array $data $key => $value assoc array
 281          * @param int $exptime Either an interval in seconds or a unix timestamp for expiry
 282          * @return bool Success
 283          * @since 1.24
 284          */
 285         public function setMulti( array $data, $exptime = 0 ) {
 286                 $res = true;
 287                 foreach ( $data as $key => $value ) {
 288                         if ( !$this->set( $key, $value, $exptime ) ) {
 289                                 $res = false;
 290                         }
 291                 }
 292                 return $res;
 293         }
 294
 295         /**
 296          * @param string $key
 297          * @param mixed $value
 298          * @param int $exptime
 299          * @return bool Success
 300          */
 301         public function add( $key, $value, $exptime = 0 ) {
 302                 if ( $this->get( $key ) === false ) {
 303                         return $this->set( $key, $value, $exptime );
 304                 }
 305                 return false; // key already set
 306         }
 307
 308         /**
 309          * Increase stored value of $key by $value while preserving its TTL
 310          * @param string $key Key to increase
 311          * @param int $value Value to add to $key (Default 1)
 312          * @return int|bool New value or false on failure
 313          */
 314         public function incr( $key, $value = 1 ) {
 315                 if ( !$this->lock( $key ) ) {
 316                         return false;
 317                 }
 318                 $n = $this->get( $key );
 319                 if ( $this->isInteger( $n ) ) { // key exists?
 320                         $n += intval( $value );
 321                         $this->set( $key, max( 0, $n ) ); // exptime?
 322                 } else {
 323                         $n = false;
 324                 }
 325                 $this->unlock( $key );
 326
 327                 return $n;
 328         }
 329
 330         /**
 331          * Decrease stored value of $key by $value while preserving its TTL
 332          * @param string $key
 333          * @param int $value
 334          * @return int
 335          */
 336         public function decr( $key, $value = 1 ) {
 337                 return $this->incr( $key, - $value );
 338         }
 339
 340         /**
 341          * Increase stored value of $key by $value while preserving its TTL
 342          *
 343          * This will create the key with value $init and TTL $ttl if not present
 344          *
 345          * @param string $key
 346          * @param int $ttl
 347          * @param int $value
 348          * @param int $init
 349          * @return bool
 350          * @since 1.24
 351          */
 352         public function incrWithInit( $key, $ttl, $value = 1, $init = 1 ) {
 353                 return $this->incr( $key, $value ) ||
 354                         $this->add( $key, (int)$init, $ttl ) || $this->incr( $key, $value );
 355         }
 356
 357         /**
 358          * Get the "last error" registered; clearLastError() should be called manually
 359          * @return int ERR_* constant for the "last error" registry
 360          * @since 1.23
 361          */
 362         public function getLastError() {
 363                 return $this->lastError;
 364         }
 365
 366         /**
 367          * Clear the "last error" registry
 368          * @since 1.23
 369          */
 370         public function clearLastError() {
 371                 $this->lastError = self::ERR_NONE;
 372         }
 373
 374         /**
 375          * Set the "last error" registry
 376          * @param int $err ERR_* constant
 377          * @since 1.23
 378          */
 379         protected function setLastError( $err ) {
 380                 $this->lastError = $err;
 381         }
 382
 383         /**
 384          * @param string $text
 385          */
 386         protected function debug( $text ) {
 387                 if ( $this->debugMode ) {
 388                         $this->logger->debug( "{class} debug: $text", array(
 389                                 'class' => get_class( $this ),
 390                         ) );
 391                 }
 392         }
 393
 394         /**
 395          * Convert an optionally relative time to an absolute time
 396          * @param int $exptime
 397          * @return int
 398          */
 399         protected function convertExpiry( $exptime ) {
 400                 if ( ( $exptime != 0 ) && ( $exptime < 86400 * 3650 /* 10 years */ ) ) {
 401                         return time() + $exptime;
 402                 } else {
 403                         return $exptime;
 404                 }
 405         }
 406
 407         /**
 408          * Convert an optionally absolute expiry time to a relative time. If an
 409          * absolute time is specified which is in the past, use a short expiry time.
 410          *
 411          * @param int $exptime
 412          * @return int
 413          */
 414         protected function convertToRelative( $exptime ) {
 415                 if ( $exptime >= 86400 * 3650 /* 10 years */ ) {
 416                         $exptime -= time();
 417                         if ( $exptime <= 0 ) {
 418                                 $exptime = 1;
 419                         }
 420                         return $exptime;
 421                 } else {
 422                         return $exptime;
 423                 }
 424         }
 425
 426         /**
 427          * Check if a value is an integer
 428          *
 429          * @param mixed $value
 430          * @return bool
 431          */
 432         protected function isInteger( $value ) {
 433                 return ( is_int( $value ) || ctype_digit( $value ) );
 434         }
 435 }