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