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 Closure $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, Closure $callback, $exptime = 0, $attempts = 10 ) {
 122                 return $this->mergeViaCas( $key, $callback, $exptime, $attempts );
 123         }
 124
 125         /**
 126          * @see BagOStuff::merge()
 127          *
 128          * @param string $key
 129          * @param Closure $callback Callback method to be executed
 130          * @param int $exptime Either an interval in seconds or a unix timestamp for expiry
 131          * @param int $attempts The amount of times to attempt a merge in case of failure
 132          * @return bool Success
 133          */
 134         protected function mergeViaCas( $key, Closure $callback, $exptime = 0, $attempts = 10 ) {
 135                 do {
 136                         $casToken = null; // passed by reference
 137                         $currentValue = $this->get( $key, $casToken ); // get the old value
 138                         $value = $callback( $this, $key, $currentValue ); // derive the new value
 139
 140                         if ( $value === false ) {
 141                                 $success = true; // do nothing
 142                         } elseif ( $currentValue === false ) {
 143                                 // Try to create the key, failing if it gets created in the meantime
 144                                 $success = $this->add( $key, $value, $exptime );
 145                         } else {
 146                                 // Try to update the key, failing if it gets changed in the meantime
 147                                 $success = $this->cas( $casToken, $key, $value, $exptime );
 148                         }
 149                 } while ( !$success && --$attempts );
 150
 151                 return $success;
 152         }
 153
 154         /**
 155          * Check and set an item.
 156          * @param mixed $casToken
 157          * @param string $key
 158          * @param mixed $value
 159          * @param int $exptime Either an interval in seconds or a unix timestamp for expiry
 160          * @return bool Success
 161          */
 162         abstract protected function cas( $casToken, $key, $value, $exptime = 0 );
 163
 164         /**
 165          * @see BagOStuff::merge()
 166          *
 167          * @param string $key
 168          * @param Closure $callback Callback method to be executed
 169          * @param int $exptime Either an interval in seconds or a unix timestamp for expiry
 170          * @param int $attempts The amount of times to attempt a merge in case of failure
 171          * @return bool Success
 172          */
 173         protected function mergeViaLock( $key, Closure $callback, $exptime = 0, $attempts = 10 ) {
 174                 if ( !$this->lock( $key, 6 ) ) {
 175                         return false;
 176                 }
 177
 178                 $currentValue = $this->get( $key ); // get the old value
 179                 $value = $callback( $this, $key, $currentValue ); // derive the new value
 180
 181                 if ( $value === false ) {
 182                         $success = true; // do nothing
 183                 } else {
 184                         $success = $this->set( $key, $value, $exptime ); // set the new value
 185                 }
 186
 187                 if ( !$this->unlock( $key ) ) {
 188                         // this should never happen
 189                         trigger_error( "Could not release lock for key '$key'." );
 190                 }
 191
 192                 return $success;
 193         }
 194
 195         /**
 196          * @param string $key
 197          * @param int $timeout Lock wait timeout [optional]
 198          * @param int $expiry Lock expiry [optional]
 199          * @return bool Success
 200          */
 201         public function lock( $key, $timeout = 6, $expiry = 6 ) {
 202                 $this->clearLastError();
 203                 $timestamp = microtime( true ); // starting UNIX timestamp
 204                 if ( $this->add( "{$key}:lock", 1, $expiry ) ) {
 205                         return true;
 206                 } elseif ( $this->getLastError() ) {
 207                         return false;
 208                 }
 209
 210                 $uRTT = ceil( 1e6 * ( microtime( true ) - $timestamp ) ); // estimate RTT (us)
 211                 $sleep = 2 * $uRTT; // rough time to do get()+set()
 212
 213                 $locked = false; // lock acquired
 214                 $attempts = 0; // failed attempts
 215                 do {
 216                         if ( ++$attempts >= 3 && $sleep <= 5e5 ) {
 217                                 // Exponentially back off after failed attempts to avoid network spam.
 218                                 // About 2*$uRTT*(2^n-1) us of "sleep" happen for the next n attempts.
 219                                 $sleep *= 2;
 220                         }
 221                         usleep( $sleep ); // back off
 222                         $this->clearLastError();
 223                         $locked = $this->add( "{$key}:lock", 1, $expiry );
 224                         if ( $this->getLastError() ) {
 225                                 return false;
 226                         }
 227                 } while ( !$locked && ( microtime( true ) - $timestamp ) < $timeout );
 228
 229                 return $locked;
 230         }
 231
 232         /**
 233          * @param string $key
 234          * @return bool Success
 235          */
 236         public function unlock( $key ) {
 237                 return $this->delete( "{$key}:lock" );
 238         }
 239
 240         /**
 241          * Delete all objects expiring before a certain date.
 242          * @param string $date The reference date in MW format
 243          * @param callable|bool $progressCallback Optional, a function which will be called
 244          *     regularly during long-running operations with the percentage progress
 245          *     as the first parameter.
 246          *
 247          * @return bool Success, false if unimplemented
 248          */
 249         public function deleteObjectsExpiringBefore( $date, $progressCallback = false ) {
 250                 // stub
 251                 return false;
 252         }
 253
 254         /* *** Emulated functions *** */
 255
 256         /**
 257          * Get an associative array containing the item for each of the keys that have items.
 258          * @param array $keys List of strings
 259          * @return array
 260          */
 261         public function getMulti( array $keys ) {
 262                 $res = array();
 263                 foreach ( $keys as $key ) {
 264                         $val = $this->get( $key );
 265                         if ( $val !== false ) {
 266                                 $res[$key] = $val;
 267                         }
 268                 }
 269                 return $res;
 270         }
 271
 272         /**
 273          * Batch insertion
 274          * @param array $data $key => $value assoc array
 275          * @param int $exptime Either an interval in seconds or a unix timestamp for expiry
 276          * @return bool Success
 277          * @since 1.24
 278          */
 279         public function setMulti( array $data, $exptime = 0 ) {
 280                 $res = true;
 281                 foreach ( $data as $key => $value ) {
 282                         if ( !$this->set( $key, $value, $exptime ) ) {
 283                                 $res = false;
 284                         }
 285                 }
 286                 return $res;
 287         }
 288
 289         /**
 290          * @param string $key
 291          * @param mixed $value
 292          * @param int $exptime
 293          * @return bool Success
 294          */
 295         public function add( $key, $value, $exptime = 0 ) {
 296                 if ( $this->get( $key ) === false ) {
 297                         return $this->set( $key, $value, $exptime );
 298                 }
 299                 return false; // key already set
 300         }
 301
 302         /**
 303          * Increase stored value of $key by $value while preserving its TTL
 304          * @param string $key Key to increase
 305          * @param int $value Value to add to $key (Default 1)
 306          * @return int|bool New value or false on failure
 307          */
 308         public function incr( $key, $value = 1 ) {
 309                 if ( !$this->lock( $key ) ) {
 310                         return false;
 311                 }
 312                 $n = $this->get( $key );
 313                 if ( $this->isInteger( $n ) ) { // key exists?
 314                         $n += intval( $value );
 315                         $this->set( $key, max( 0, $n ) ); // exptime?
 316                 } else {
 317                         $n = false;
 318                 }
 319                 $this->unlock( $key );
 320
 321                 return $n;
 322         }
 323
 324         /**
 325          * Decrease stored value of $key by $value while preserving its TTL
 326          * @param string $key
 327          * @param int $value
 328          * @return int
 329          */
 330         public function decr( $key, $value = 1 ) {
 331                 return $this->incr( $key, - $value );
 332         }
 333
 334         /**
 335          * Increase stored value of $key by $value while preserving its TTL
 336          *
 337          * This will create the key with value $init and TTL $ttl if not present
 338          *
 339          * @param string $key
 340          * @param int $ttl
 341          * @param int $value
 342          * @param int $init
 343          * @return bool
 344          * @since 1.24
 345          */
 346         public function incrWithInit( $key, $ttl, $value = 1, $init = 1 ) {
 347                 return $this->incr( $key, $value ) ||
 348                         $this->add( $key, (int)$init, $ttl ) || $this->incr( $key, $value );
 349         }
 350
 351         /**
 352          * Get the "last error" registered; clearLastError() should be called manually
 353          * @return int ERR_* constant for the "last error" registry
 354          * @since 1.23
 355          */
 356         public function getLastError() {
 357                 return $this->lastError;
 358         }
 359
 360         /**
 361          * Clear the "last error" registry
 362          * @since 1.23
 363          */
 364         public function clearLastError() {
 365                 $this->lastError = self::ERR_NONE;
 366         }
 367
 368         /**
 369          * Set the "last error" registry
 370          * @param int $err ERR_* constant
 371          * @since 1.23
 372          */
 373         protected function setLastError( $err ) {
 374                 $this->lastError = $err;
 375         }
 376
 377         /**
 378          * @param string $text
 379          */
 380         public function debug( $text ) {
 381                 if ( $this->debugMode ) {
 382                         $this->logger->debug( "{class} debug: $text", array(
 383                                 'class' => get_class( $this ),
 384                         ) );
 385                 }
 386         }
 387
 388         /**
 389          * Convert an optionally relative time to an absolute time
 390          * @param int $exptime
 391          * @return int
 392          */
 393         protected function convertExpiry( $exptime ) {
 394                 if ( ( $exptime != 0 ) && ( $exptime < 86400 * 3650 /* 10 years */ ) ) {
 395                         return time() + $exptime;
 396                 } else {
 397                         return $exptime;
 398                 }
 399         }
 400
 401         /**
 402          * Convert an optionally absolute expiry time to a relative time. If an
 403          * absolute time is specified which is in the past, use a short expiry time.
 404          *
 405          * @param int $exptime
 406          * @return int
 407          */
 408         protected function convertToRelative( $exptime ) {
 409                 if ( $exptime >= 86400 * 3650 /* 10 years */ ) {
 410                         $exptime -= time();
 411                         if ( $exptime <= 0 ) {
 412                                 $exptime = 1;
 413                         }
 414                         return $exptime;
 415                 } else {
 416                         return $exptime;
 417                 }
 418         }
 419
 420         /**
 421          * Check if a value is an integer
 422          *
 423          * @param mixed $value
 424          * @return bool
 425          */
 426         protected function isInteger( $value ) {
 427                 return ( is_int( $value ) || ctype_digit( $value ) );
 428         }
 429 }