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