includes/libs/objectcache/BagOStuff.php

   1 <?php
   2 /**
   3  * Copyright © 2003-2004 Brion Vibber <brion@pobox.com>
   4  * https://www.mediawiki.org/
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 2 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License along
  17  * with this program; if not, write to the Free Software Foundation, Inc.,
  18  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  19  * http://www.gnu.org/copyleft/gpl.html
  20  *
  21  * @file
  22  * @ingroup Cache
  23  */
  24
  25 /**
  26  * @defgroup Cache Cache
  27  */
  28
  29 use Psr\Log\LoggerAwareInterface;
  30 use Psr\Log\LoggerInterface;
  31 use Psr\Log\NullLogger;
  32
  33 /**
  34  * interface is intended to be more or less compatible with
  35  * the PHP memcached client.
  36  *
  37  * backends for local hash array and SQL table included:
  38  * @code
  39  *   $bag = new HashBagOStuff();
  40  *   $bag = new SqlBagOStuff(); # connect to db first
  41  * @endcode
  42  *
  43  * @ingroup Cache
  44  */
  45 abstract class BagOStuff implements LoggerAwareInterface {
  46         private $debugMode = false;
  47
  48         /** @var integer */
  49         protected $lastError = self::ERR_NONE;
  50
  51         /**
  52          * @var LoggerInterface
  53          */
  54         protected $logger;
  55
  56         /** Possible values for getLastError() */
  57         const ERR_NONE = 0; // no error
  58         const ERR_NO_RESPONSE = 1; // no response
  59         const ERR_UNREACHABLE = 2; // can't connect
  60         const ERR_UNEXPECTED = 3; // response gave some error
  61
  62         /** Bitfield constants for get()/getMulti() */
  63         const READ_LATEST = 1; // use latest data for replicated stores
  64
  65         public function __construct( array $params = array() ) {
  66                 if ( isset( $params['logger'] ) ) {
  67                         $this->setLogger( $params['logger'] );
  68                 } else {
  69                         $this->setLogger( new NullLogger() );
  70                 }
  71         }
  72
  73         /**
  74          * @param LoggerInterface $logger
  75          * @return null
  76          */
  77         public function setLogger( LoggerInterface $logger ) {
  78                 $this->logger = $logger;
  79         }
  80
  81         /**
  82          * @param bool $bool
  83          */
  84         public function setDebug( $bool ) {
  85                 $this->debugMode = $bool;
  86         }
  87
  88         /**
  89          * Get an item with the given key. Returns false if it does not exist.
  90          * @param string $key
  91          * @param mixed $casToken [optional]
  92          * @param integer $flags Bitfield; supports READ_LATEST [optional]
  93          * @return mixed Returns false on failure
  94          */
  95         abstract public function get( $key, &$casToken = null, $flags = 0 );
  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          * Delete an item.
 108          * @param string $key
 109          * @return bool True if the item was deleted or not found, false on failure
 110          */
 111         abstract public function delete( $key );
 112
 113         /**
 114          * Merge changes into the existing cache value (possibly creating a new one).
 115          * The callback function returns the new value given the current value
 116          * (which will be false if not present), and takes the arguments:
 117          * (this BagOStuff, cache key, current value).
 118          *
 119          * @param string $key
 120          * @param callable $callback Callback method to be executed
 121          * @param int $exptime Either an interval in seconds or a unix timestamp for expiry
 122          * @param int $attempts The amount of times to attempt a merge in case of failure
 123          * @return bool Success
 124          * @throws InvalidArgumentException
 125          */
 126         public function merge( $key, $callback, $exptime = 0, $attempts = 10 ) {
 127                 if ( !is_callable( $callback ) ) {
 128                         throw new InvalidArgumentException( "Got invalid callback." );
 129                 }
 130
 131                 return $this->mergeViaLock( $key, $callback, $exptime, $attempts );
 132         }
 133
 134         /**
 135          * @see BagOStuff::merge()
 136          *
 137          * @param string $key
 138          * @param callable $callback Callback method to be executed
 139          * @param int $exptime Either an interval in seconds or a unix timestamp for expiry
 140          * @param int $attempts The amount of times to attempt a merge in case of failure
 141          * @return bool Success
 142          */
 143         protected function mergeViaCas( $key, $callback, $exptime = 0, $attempts = 10 ) {
 144                 do {
 145                         $casToken = null; // passed by reference
 146                         $currentValue = $this->get( $key, $casToken );
 147                         // Derive the new value from the old value
 148                         $value = call_user_func( $callback, $this, $key, $currentValue );
 149
 150                         if ( $value === false ) {
 151                                 $success = true; // do nothing
 152                         } elseif ( $currentValue === false ) {
 153                                 // Try to create the key, failing if it gets created in the meantime
 154                                 $success = $this->add( $key, $value, $exptime );
 155                         } else {
 156                                 // Try to update the key, failing if it gets changed in the meantime
 157                                 $success = $this->cas( $casToken, $key, $value, $exptime );
 158                         }
 159                 } while ( !$success && --$attempts );
 160
 161                 return $success;
 162         }
 163
 164         /**
 165          * Check and set an item
 166          *
 167          * @param mixed $casToken
 168          * @param string $key
 169          * @param mixed $value
 170          * @param int $exptime Either an interval in seconds or a unix timestamp for expiry
 171          * @return bool Success
 172          * @throws Exception
 173          */
 174         protected function cas( $casToken, $key, $value, $exptime = 0 ) {
 175                 throw new Exception( "CAS is not implemented in " . __CLASS__ );
 176         }
 177
 178         /**
 179          * @see BagOStuff::merge()
 180          *
 181          * @param string $key
 182          * @param callable $callback Callback method to be executed
 183          * @param int $exptime Either an interval in seconds or a unix timestamp for expiry
 184          * @param int $attempts The amount of times to attempt a merge in case of failure
 185          * @return bool Success
 186          */
 187         protected function mergeViaLock( $key, $callback, $exptime = 0, $attempts = 10 ) {
 188                 if ( !$this->lock( $key, 6 ) ) {
 189                         return false;
 190                 }
 191
 192                 $currentValue = $this->get( $key );
 193                 // Derive the new value from the old value
 194                 $value = call_user_func( $callback, $this, $key, $currentValue );
 195
 196                 if ( $value === false ) {
 197                         $success = true; // do nothing
 198                 } else {
 199                         $success = $this->set( $key, $value, $exptime ); // set the new value
 200                 }
 201
 202                 if ( !$this->unlock( $key ) ) {
 203                         // this should never happen
 204                         trigger_error( "Could not release lock for key '$key'." );
 205                 }
 206
 207                 return $success;
 208         }
 209
 210         /**
 211          * @param string $key
 212          * @param int $timeout Lock wait timeout; 0 for non-blocking [optional]
 213          * @param int $expiry Lock expiry [optional]
 214          * @return bool Success
 215          */
 216         public function lock( $key, $timeout = 6, $expiry = 6 ) {
 217                 $this->clearLastError();
 218                 $timestamp = microtime( true ); // starting UNIX timestamp
 219                 if ( $this->add( "{$key}:lock", 1, $expiry ) ) {
 220                         return true;
 221                 } elseif ( $this->getLastError() ) {
 222                         return false;
 223                 }
 224
 225                 $uRTT = ceil( 1e6 * ( microtime( true ) - $timestamp ) ); // estimate RTT (us)
 226                 $sleep = 2 * $uRTT; // rough time to do get()+set()
 227
 228                 $locked = false; // lock acquired
 229                 $attempts = 0; // failed attempts
 230                 do {
 231                         if ( ++$attempts >= 3 && $sleep <= 5e5 ) {
 232                                 // Exponentially back off after failed attempts to avoid network spam.
 233                                 // About 2*$uRTT*(2^n-1) us of "sleep" happen for the next n attempts.
 234                                 $sleep *= 2;
 235                         }
 236                         usleep( $sleep ); // back off
 237                         $this->clearLastError();
 238                         $locked = $this->add( "{$key}:lock", 1, $expiry );
 239                         if ( $this->getLastError() ) {
 240                                 return false;
 241                         }
 242                 } while ( !$locked && ( microtime( true ) - $timestamp ) < $timeout );
 243
 244                 return $locked;
 245         }
 246
 247         /**
 248          * @param string $key
 249          * @return bool Success
 250          */
 251         public function unlock( $key ) {
 252                 return $this->delete( "{$key}:lock" );
 253         }
 254
 255         /**
 256          * Delete all objects expiring before a certain date.
 257          * @param string $date The reference date in MW format
 258          * @param callable|bool $progressCallback Optional, a function which will be called
 259          *     regularly during long-running operations with the percentage progress
 260          *     as the first parameter.
 261          *
 262          * @return bool Success, false if unimplemented
 263          */
 264         public function deleteObjectsExpiringBefore( $date, $progressCallback = false ) {
 265                 // stub
 266                 return false;
 267         }
 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          * @param integer $flags Bitfield; supports READ_LATEST [optional]
 273          * @return array
 274          */
 275         public function getMulti( array $keys, $flags = 0 ) {
 276                 $res = array();
 277                 foreach ( $keys as $key ) {
 278                         $val = $this->get( $key );
 279                         if ( $val !== false ) {
 280                                 $res[$key] = $val;
 281                         }
 282                 }
 283                 return $res;
 284         }
 285
 286         /**
 287          * Batch insertion
 288          * @param array $data $key => $value assoc array
 289          * @param int $exptime Either an interval in seconds or a unix timestamp for expiry
 290          * @return bool Success
 291          * @since 1.24
 292          */
 293         public function setMulti( array $data, $exptime = 0 ) {
 294                 $res = true;
 295                 foreach ( $data as $key => $value ) {
 296                         if ( !$this->set( $key, $value, $exptime ) ) {
 297                                 $res = false;
 298                         }
 299                 }
 300                 return $res;
 301         }
 302
 303         /**
 304          * @param string $key
 305          * @param mixed $value
 306          * @param int $exptime
 307          * @return bool Success
 308          */
 309         public function add( $key, $value, $exptime = 0 ) {
 310                 if ( $this->get( $key ) === false ) {
 311                         return $this->set( $key, $value, $exptime );
 312                 }
 313                 return false; // key already set
 314         }
 315
 316         /**
 317          * Increase stored value of $key by $value while preserving its TTL
 318          * @param string $key Key to increase
 319          * @param int $value Value to add to $key (Default 1)
 320          * @return int|bool New value or false on failure
 321          */
 322         public function incr( $key, $value = 1 ) {
 323                 if ( !$this->lock( $key ) ) {
 324                         return false;
 325                 }
 326                 $n = $this->get( $key );
 327                 if ( $this->isInteger( $n ) ) { // key exists?
 328                         $n += intval( $value );
 329                         $this->set( $key, max( 0, $n ) ); // exptime?
 330                 } else {
 331                         $n = false;
 332                 }
 333                 $this->unlock( $key );
 334
 335                 return $n;
 336         }
 337
 338         /**
 339          * Decrease stored value of $key by $value while preserving its TTL
 340          * @param string $key
 341          * @param int $value
 342          * @return int|bool New value or false on failure
 343          */
 344         public function decr( $key, $value = 1 ) {
 345                 return $this->incr( $key, - $value );
 346         }
 347
 348         /**
 349          * Increase stored value of $key by $value while preserving its TTL
 350          *
 351          * This will create the key with value $init and TTL $ttl if not present
 352          *
 353          * @param string $key
 354          * @param int $ttl
 355          * @param int $value
 356          * @param int $init
 357          * @return bool
 358          * @since 1.24
 359          */
 360         public function incrWithInit( $key, $ttl, $value = 1, $init = 1 ) {
 361                 return $this->incr( $key, $value ) ||
 362                         $this->add( $key, (int)$init, $ttl ) || $this->incr( $key, $value );
 363         }
 364
 365         /**
 366          * Get the "last error" registered; clearLastError() should be called manually
 367          * @return int ERR_* constant for the "last error" registry
 368          * @since 1.23
 369          */
 370         public function getLastError() {
 371                 return $this->lastError;
 372         }
 373
 374         /**
 375          * Clear the "last error" registry
 376          * @since 1.23
 377          */
 378         public function clearLastError() {
 379                 $this->lastError = self::ERR_NONE;
 380         }
 381
 382         /**
 383          * Set the "last error" registry
 384          * @param int $err ERR_* constant
 385          * @since 1.23
 386          */
 387         protected function setLastError( $err ) {
 388                 $this->lastError = $err;
 389         }
 390
 391         /**
 392          * Modify a cache update operation array for EventRelayer::notify()
 393          *
 394          * This is used for relayed writes, e.g. for broadcasting a change
 395          * to multiple data-centers. If the array contains a 'val' field
 396          * then the command involves setting a key to that value. Note that
 397          * for simplicity, 'val' is always a simple scalar value. This method
 398          * is used to possibly serialize the value and add any cache-specific
 399          * key/values needed for the relayer daemon (e.g. memcached flags).
 400          *
 401          * @param array $event
 402          * @return array
 403          * @since 1.26
 404          */
 405         public function modifySimpleRelayEvent( array $event ) {
 406                 return $event;
 407         }
 408
 409         /**
 410          * @param string $text
 411          */
 412         protected function debug( $text ) {
 413                 if ( $this->debugMode ) {
 414                         $this->logger->debug( "{class} debug: $text", array(
 415                                 'class' => get_class( $this ),
 416                         ) );
 417                 }
 418         }
 419
 420         /**
 421          * Convert an optionally relative time to an absolute time
 422          * @param int $exptime
 423          * @return int
 424          */
 425         protected function convertExpiry( $exptime ) {
 426                 if ( ( $exptime != 0 ) && ( $exptime < 86400 * 3650 /* 10 years */ ) ) {
 427                         return time() + $exptime;
 428                 } else {
 429                         return $exptime;
 430                 }
 431         }
 432
 433         /**
 434          * Convert an optionally absolute expiry time to a relative time. If an
 435          * absolute time is specified which is in the past, use a short expiry time.
 436          *
 437          * @param int $exptime
 438          * @return int
 439          */
 440         protected function convertToRelative( $exptime ) {
 441                 if ( $exptime >= 86400 * 3650 /* 10 years */ ) {
 442                         $exptime -= time();
 443                         if ( $exptime <= 0 ) {
 444                                 $exptime = 1;
 445                         }
 446                         return $exptime;
 447                 } else {
 448                         return $exptime;
 449                 }
 450         }
 451
 452         /**
 453          * Check if a value is an integer
 454          *
 455          * @param mixed $value
 456          * @return bool
 457          */
 458         protected function isInteger( $value ) {
 459                 return ( is_int( $value ) || ctype_digit( $value ) );
 460         }
 461 }