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  * @endcode
  44  *
  45  * @ingroup Cache
  46  */
  47 abstract class BagOStuff implements LoggerAwareInterface {
  48         private $debugMode = false;
  49
  50         /** @var integer */
  51         protected $lastError = self::ERR_NONE;
  52
  53         /**
  54          * @var LoggerInterface
  55          */
  56         protected $logger;
  57
  58         /** Possible values for getLastError() */
  59         const ERR_NONE = 0; // no error
  60         const ERR_NO_RESPONSE = 1; // no response
  61         const ERR_UNREACHABLE = 2; // can't connect
  62         const ERR_UNEXPECTED = 3; // response gave some error
  63
  64         public function __construct( array $params = array() ) {
  65                 if ( isset( $params['logger'] ) ) {
  66                         $this->setLogger( $params['logger'] );
  67                 } else {
  68                         $this->setLogger( new NullLogger() );
  69                 }
  70         }
  71
  72         /**
  73          * @param LoggerInterface $logger
  74          * @return null
  75          */
  76         public function setLogger( LoggerInterface $logger ) {
  77                 $this->logger = $logger;
  78         }
  79
  80         /**
  81          * @param bool $bool
  82          */
  83         public function setDebug( $bool ) {
  84                 $this->debugMode = $bool;
  85         }
  86
  87         /**
  88          * Get an item with the given key. Returns false if it does not exist.
  89          * @param string $key
  90          * @param mixed $casToken [optional]
  91          * @return mixed Returns false on failure
  92          */
  93         abstract public function get( $key, &$casToken = null );
  94
  95         /**
  96          * Set an item.
  97          * @param string $key
  98          * @param mixed $value
  99          * @param int $exptime Either an interval in seconds or a unix timestamp for expiry
 100          * @return bool Success
 101          */
 102         abstract public function set( $key, $value, $exptime = 0 );
 103
 104         /**
 105          * Delete an item.
 106          * @param string $key
 107          * @return bool True if the item was deleted or not found, false on failure
 108          */
 109         abstract public function delete( $key );
 110
 111         /**
 112          * Merge changes into the existing cache value (possibly creating a new one).
 113          * The callback function returns the new value given the current value
 114          * (which will be false if not present), and takes the arguments:
 115          * (this BagOStuff, cache key, current value).
 116          *
 117          * @param string $key
 118          * @param callable $callback Callback method to be executed
 119          * @param int $exptime Either an interval in seconds or a unix timestamp for expiry
 120          * @param int $attempts The amount of times to attempt a merge in case of failure
 121          * @return bool Success
 122          * @throws InvalidArgumentException
 123          */
 124         public function merge( $key, $callback, $exptime = 0, $attempts = 10 ) {
 125                 if ( !is_callable( $callback ) ) {
 126                         throw new InvalidArgumentException( "Got invalid callback." );
 127                 }
 128
 129                 return $this->mergeViaLock( $key, $callback, $exptime, $attempts );
 130         }
 131
 132         /**
 133          * @see BagOStuff::merge()
 134          *
 135          * @param string $key
 136          * @param callable $callback Callback method to be executed
 137          * @param int $exptime Either an interval in seconds or a unix timestamp for expiry
 138          * @param int $attempts The amount of times to attempt a merge in case of failure
 139          * @return bool Success
 140          */
 141         protected function mergeViaCas( $key, $callback, $exptime = 0, $attempts = 10 ) {
 142                 do {
 143                         $casToken = null; // passed by reference
 144                         $currentValue = $this->get( $key, $casToken );
 145                         // Derive the new value from the old value
 146                         $value = call_user_func( $callback, $this, $key, $currentValue );
 147
 148                         if ( $value === false ) {
 149                                 $success = true; // do nothing
 150                         } elseif ( $currentValue === false ) {
 151                                 // Try to create the key, failing if it gets created in the meantime
 152                                 $success = $this->add( $key, $value, $exptime );
 153                         } else {
 154                                 // Try to update the key, failing if it gets changed in the meantime
 155                                 $success = $this->cas( $casToken, $key, $value, $exptime );
 156                         }
 157                 } while ( !$success && --$attempts );
 158
 159                 return $success;
 160         }
 161
 162         /**
 163          * Check and set an item
 164          *
 165          * @param mixed $casToken
 166          * @param string $key
 167          * @param mixed $value
 168          * @param int $exptime Either an interval in seconds or a unix timestamp for expiry
 169          * @return bool Success
 170          * @throws Exception
 171          */
 172         protected function cas( $casToken, $key, $value, $exptime = 0 ) {
 173                 throw new Exception( "CAS is not implemented in " . __CLASS__ );
 174         }
 175
 176         /**
 177          * @see BagOStuff::merge()
 178          *
 179          * @param string $key
 180          * @param callable $callback Callback method to be executed
 181          * @param int $exptime Either an interval in seconds or a unix timestamp for expiry
 182          * @param int $attempts The amount of times to attempt a merge in case of failure
 183          * @return bool Success
 184          */
 185         protected function mergeViaLock( $key, $callback, $exptime = 0, $attempts = 10 ) {
 186                 if ( !$this->lock( $key, 6 ) ) {
 187                         return false;
 188                 }
 189
 190                 $currentValue = $this->get( $key );
 191                 // Derive the new value from the old value
 192                 $value = call_user_func( $callback, $this, $key, $currentValue );
 193
 194                 if ( $value === false ) {
 195                         $success = true; // do nothing
 196                 } else {
 197                         $success = $this->set( $key, $value, $exptime ); // set the new value
 198                 }
 199
 200                 if ( !$this->unlock( $key ) ) {
 201                         // this should never happen
 202                         trigger_error( "Could not release lock for key '$key'." );
 203                 }
 204
 205                 return $success;
 206         }
 207
 208         /**
 209          * @param string $key
 210          * @param int $timeout Lock wait timeout; 0 for non-blocking [optional]
 211          * @param int $expiry Lock expiry [optional]
 212          * @return bool Success
 213          */
 214         public function lock( $key, $timeout = 6, $expiry = 6 ) {
 215                 $this->clearLastError();
 216                 $timestamp = microtime( true ); // starting UNIX timestamp
 217                 if ( $this->add( "{$key}:lock", 1, $expiry ) ) {
 218                         return true;
 219                 } elseif ( $this->getLastError() ) {
 220                         return false;
 221                 }
 222
 223                 $uRTT = ceil( 1e6 * ( microtime( true ) - $timestamp ) ); // estimate RTT (us)
 224                 $sleep = 2 * $uRTT; // rough time to do get()+set()
 225
 226                 $locked = false; // lock acquired
 227                 $attempts = 0; // failed attempts
 228                 do {
 229                         if ( ++$attempts >= 3 && $sleep <= 5e5 ) {
 230                                 // Exponentially back off after failed attempts to avoid network spam.
 231                                 // About 2*$uRTT*(2^n-1) us of "sleep" happen for the next n attempts.
 232                                 $sleep *= 2;
 233                         }
 234                         usleep( $sleep ); // back off
 235                         $this->clearLastError();
 236                         $locked = $this->add( "{$key}:lock", 1, $expiry );
 237                         if ( $this->getLastError() ) {
 238                                 return false;
 239                         }
 240                 } while ( !$locked && ( microtime( true ) - $timestamp ) < $timeout );
 241
 242                 return $locked;
 243         }
 244
 245         /**
 246          * @param string $key
 247          * @return bool Success
 248          */
 249         public function unlock( $key ) {
 250                 return $this->delete( "{$key}:lock" );
 251         }
 252
 253         /**
 254          * Delete all objects expiring before a certain date.
 255          * @param string $date The reference date in MW format
 256          * @param callable|bool $progressCallback Optional, a function which will be called
 257          *     regularly during long-running operations with the percentage progress
 258          *     as the first parameter.
 259          *
 260          * @return bool Success, false if unimplemented
 261          */
 262         public function deleteObjectsExpiringBefore( $date, $progressCallback = false ) {
 263                 // stub
 264                 return false;
 265         }
 266
 267         /* *** Emulated functions *** */
 268
 269         /**
 270          * Get an associative array containing the item for each of the keys that have items.
 271          * @param array $keys List of strings
 272          * @return array
 273          */
 274         public function getMulti( array $keys ) {
 275                 $res = array();
 276                 foreach ( $keys as $key ) {
 277                         $val = $this->get( $key );
 278                         if ( $val !== false ) {
 279                                 $res[$key] = $val;
 280                         }
 281                 }
 282                 return $res;
 283         }
 284
 285         /**
 286          * Batch insertion
 287          * @param array $data $key => $value assoc array
 288          * @param int $exptime Either an interval in seconds or a unix timestamp for expiry
 289          * @return bool Success
 290          * @since 1.24
 291          */
 292         public function setMulti( array $data, $exptime = 0 ) {
 293                 $res = true;
 294                 foreach ( $data as $key => $value ) {
 295                         if ( !$this->set( $key, $value, $exptime ) ) {
 296                                 $res = false;
 297                         }
 298                 }
 299                 return $res;
 300         }
 301
 302         /**
 303          * @param string $key
 304          * @param mixed $value
 305          * @param int $exptime
 306          * @return bool Success
 307          */
 308         public function add( $key, $value, $exptime = 0 ) {
 309                 if ( $this->get( $key ) === false ) {
 310                         return $this->set( $key, $value, $exptime );
 311                 }
 312                 return false; // key already set
 313         }
 314
 315         /**
 316          * Increase stored value of $key by $value while preserving its TTL
 317          * @param string $key Key to increase
 318          * @param int $value Value to add to $key (Default 1)
 319          * @return int|bool New value or false on failure
 320          */
 321         public function incr( $key, $value = 1 ) {
 322                 if ( !$this->lock( $key ) ) {
 323                         return false;
 324                 }
 325                 $n = $this->get( $key );
 326                 if ( $this->isInteger( $n ) ) { // key exists?
 327                         $n += intval( $value );
 328                         $this->set( $key, max( 0, $n ) ); // exptime?
 329                 } else {
 330                         $n = false;
 331                 }
 332                 $this->unlock( $key );
 333
 334                 return $n;
 335         }
 336
 337         /**
 338          * Decrease stored value of $key by $value while preserving its TTL
 339          * @param string $key
 340          * @param int $value
 341          * @return int|bool New value or false on failure
 342          */
 343         public function decr( $key, $value = 1 ) {
 344                 return $this->incr( $key, - $value );
 345         }
 346
 347         /**
 348          * Increase stored value of $key by $value while preserving its TTL
 349          *
 350          * This will create the key with value $init and TTL $ttl if not present
 351          *
 352          * @param string $key
 353          * @param int $ttl
 354          * @param int $value
 355          * @param int $init
 356          * @return bool
 357          * @since 1.24
 358          */
 359         public function incrWithInit( $key, $ttl, $value = 1, $init = 1 ) {
 360                 return $this->incr( $key, $value ) ||
 361                         $this->add( $key, (int)$init, $ttl ) || $this->incr( $key, $value );
 362         }
 363
 364         /**
 365          * Get the "last error" registered; clearLastError() should be called manually
 366          * @return int ERR_* constant for the "last error" registry
 367          * @since 1.23
 368          */
 369         public function getLastError() {
 370                 return $this->lastError;
 371         }
 372
 373         /**
 374          * Clear the "last error" registry
 375          * @since 1.23
 376          */
 377         public function clearLastError() {
 378                 $this->lastError = self::ERR_NONE;
 379         }
 380
 381         /**
 382          * Set the "last error" registry
 383          * @param int $err ERR_* constant
 384          * @since 1.23
 385          */
 386         protected function setLastError( $err ) {
 387                 $this->lastError = $err;
 388         }
 389
 390         /**
 391          * Modify a cache update operation array for EventRelayer::notify()
 392          *
 393          * This is used for relayed writes, e.g. for broadcasting a change
 394          * to multiple data-centers. If the array contains a 'val' field
 395          * then the command involves setting a key to that value. Note that
 396          * for simplicity, 'val' is always a simple scalar value. This method
 397          * is used to possibly serialize the value and add any cache-specific
 398          * key/values needed for the relayer daemon (e.g. memcached flags).
 399          *
 400          * @param array $event
 401          * @return array
 402          * @since 1.26
 403          */
 404         public function modifySimpleRelayEvent( array $event ) {
 405                 return $event;
 406         }
 407
 408         /**
 409          * @param string $text
 410          */
 411         protected function debug( $text ) {
 412                 if ( $this->debugMode ) {
 413                         $this->logger->debug( "{class} debug: $text", array(
 414                                 'class' => get_class( $this ),
 415                         ) );
 416                 }
 417         }
 418
 419         /**
 420          * Convert an optionally relative time to an absolute time
 421          * @param int $exptime
 422          * @return int
 423          */
 424         protected function convertExpiry( $exptime ) {
 425                 if ( ( $exptime != 0 ) && ( $exptime < 86400 * 3650 /* 10 years */ ) ) {
 426                         return time() + $exptime;
 427                 } else {
 428                         return $exptime;
 429                 }
 430         }
 431
 432         /**
 433          * Convert an optionally absolute expiry time to a relative time. If an
 434          * absolute time is specified which is in the past, use a short expiry time.
 435          *
 436          * @param int $exptime
 437          * @return int
 438          */
 439         protected function convertToRelative( $exptime ) {
 440                 if ( $exptime >= 86400 * 3650 /* 10 years */ ) {
 441                         $exptime -= time();
 442                         if ( $exptime <= 0 ) {
 443                                 $exptime = 1;
 444                         }
 445                         return $exptime;
 446                 } else {
 447                         return $exptime;
 448                 }
 449         }
 450
 451         /**
 452          * Check if a value is an integer
 453          *
 454          * @param mixed $value
 455          * @return bool
 456          */
 457         protected function isInteger( $value ) {
 458                 return ( is_int( $value ) || ctype_digit( $value ) );
 459         }
 460 }