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         public function __construct( array $params = array() ) {
  63                 if ( isset( $params['logger'] ) ) {
  64                         $this->setLogger( $params['logger'] );
  65                 } else {
  66                         $this->setLogger( new NullLogger() );
  67                 }
  68         }
  69
  70         /**
  71          * @param LoggerInterface $logger
  72          * @return null
  73          */
  74         public function setLogger( LoggerInterface $logger ) {
  75                 $this->logger = $logger;
  76         }
  77
  78         /**
  79          * @param bool $bool
  80          */
  81         public function setDebug( $bool ) {
  82                 $this->debugMode = $bool;
  83         }
  84
  85         /**
  86          * Get an item with the given key. Returns false if it does not exist.
  87          * @param string $key
  88          * @param mixed $casToken [optional]
  89          * @return mixed Returns false on failure
  90          */
  91         abstract public function get( $key, &$casToken = null );
  92
  93         /**
  94          * Set an item.
  95          * @param string $key
  96          * @param mixed $value
  97          * @param int $exptime Either an interval in seconds or a unix timestamp for expiry
  98          * @return bool Success
  99          */
 100         abstract public function set( $key, $value, $exptime = 0 );
 101
 102         /**
 103          * Delete an item.
 104          * @param string $key
 105          * @return bool True if the item was deleted or not found, false on failure
 106          */
 107         abstract public function delete( $key );
 108
 109         /**
 110          * Merge changes into the existing cache value (possibly creating a new one).
 111          * The callback function returns the new value given the current value
 112          * (which will be false if not present), and takes the arguments:
 113          * (this BagOStuff, cache key, current value).
 114          *
 115          * @param string $key
 116          * @param callable $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          * @throws InvalidArgumentException
 121          */
 122         public function merge( $key, $callback, $exptime = 0, $attempts = 10 ) {
 123                 if ( !is_callable( $callback ) ) {
 124                         throw new InvalidArgumentException( "Got invalid callback." );
 125                 }
 126
 127                 return $this->mergeViaLock( $key, $callback, $exptime, $attempts );
 128         }
 129
 130         /**
 131          * @see BagOStuff::merge()
 132          *
 133          * @param string $key
 134          * @param callable $callback Callback method to be executed
 135          * @param int $exptime Either an interval in seconds or a unix timestamp for expiry
 136          * @param int $attempts The amount of times to attempt a merge in case of failure
 137          * @return bool Success
 138          */
 139         protected function mergeViaCas( $key, $callback, $exptime = 0, $attempts = 10 ) {
 140                 do {
 141                         $casToken = null; // passed by reference
 142                         $currentValue = $this->get( $key, $casToken );
 143                         // Derive the new value from the old value
 144                         $value = call_user_func( $callback, $this, $key, $currentValue );
 145
 146                         if ( $value === false ) {
 147                                 $success = true; // do nothing
 148                         } elseif ( $currentValue === false ) {
 149                                 // Try to create the key, failing if it gets created in the meantime
 150                                 $success = $this->add( $key, $value, $exptime );
 151                         } else {
 152                                 // Try to update the key, failing if it gets changed in the meantime
 153                                 $success = $this->cas( $casToken, $key, $value, $exptime );
 154                         }
 155                 } while ( !$success && --$attempts );
 156
 157                 return $success;
 158         }
 159
 160         /**
 161          * Check and set an item
 162          *
 163          * @param mixed $casToken
 164          * @param string $key
 165          * @param mixed $value
 166          * @param int $exptime Either an interval in seconds or a unix timestamp for expiry
 167          * @return bool Success
 168          * @throws Exception
 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 }