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                         $this->clearLastError();
 146                         $casToken = null; // passed by reference
 147                         $currentValue = $this->get( $key, $casToken );
 148                         if ( $this->getLastError() ) {
 149                                 return false; // don't spam retries (retry only on races)
 150                         }
 151
 152                         // Derive the new value from the old value
 153                         $value = call_user_func( $callback, $this, $key, $currentValue );
 154
 155                         $this->clearLastError();
 156                         if ( $value === false ) {
 157                                 $success = true; // do nothing
 158                         } elseif ( $currentValue === false ) {
 159                                 // Try to create the key, failing if it gets created in the meantime
 160                                 $success = $this->add( $key, $value, $exptime );
 161                         } else {
 162                                 // Try to update the key, failing if it gets changed in the meantime
 163                                 $success = $this->cas( $casToken, $key, $value, $exptime );
 164                         }
 165                         if ( $this->getLastError() ) {
 166                                 return false; // IO error; don't spam retries
 167                         }
 168                 } while ( !$success && --$attempts );
 169
 170                 return $success;
 171         }
 172
 173         /**
 174          * Check and set an item
 175          *
 176          * @param mixed $casToken
 177          * @param string $key
 178          * @param mixed $value
 179          * @param int $exptime Either an interval in seconds or a unix timestamp for expiry
 180          * @return bool Success
 181          * @throws Exception
 182          */
 183         protected function cas( $casToken, $key, $value, $exptime = 0 ) {
 184                 throw new Exception( "CAS is not implemented in " . __CLASS__ );
 185         }
 186
 187         /**
 188          * @see BagOStuff::merge()
 189          *
 190          * @param string $key
 191          * @param callable $callback Callback method to be executed
 192          * @param int $exptime Either an interval in seconds or a unix timestamp for expiry
 193          * @param int $attempts The amount of times to attempt a merge in case of failure
 194          * @return bool Success
 195          */
 196         protected function mergeViaLock( $key, $callback, $exptime = 0, $attempts = 10 ) {
 197                 if ( !$this->lock( $key, 6 ) ) {
 198                         return false;
 199                 }
 200
 201                 $this->clearLastError();
 202                 $currentValue = $this->get( $key );
 203                 if ( !$this->getLastError() ) {
 204                         // Derive the new value from the old value
 205                         $value = call_user_func( $callback, $this, $key, $currentValue );
 206
 207                         if ( $value === false ) {
 208                                 $success = true; // do nothing
 209                         } else {
 210                                 $success = $this->set( $key, $value, $exptime ); // set the new value
 211                         }
 212                 }
 213
 214                 if ( !$this->unlock( $key ) ) {
 215                         // this should never happen
 216                         trigger_error( "Could not release lock for key '$key'." );
 217                 }
 218
 219                 return $success;
 220         }
 221
 222         /**
 223          * @param string $key
 224          * @param int $timeout Lock wait timeout; 0 for non-blocking [optional]
 225          * @param int $expiry Lock expiry [optional]
 226          * @return bool Success
 227          */
 228         public function lock( $key, $timeout = 6, $expiry = 6 ) {
 229                 $this->clearLastError();
 230                 $timestamp = microtime( true ); // starting UNIX timestamp
 231                 if ( $this->add( "{$key}:lock", 1, $expiry ) ) {
 232                         return true;
 233                 } elseif ( $this->getLastError() ) {
 234                         return false;
 235                 }
 236
 237                 $uRTT = ceil( 1e6 * ( microtime( true ) - $timestamp ) ); // estimate RTT (us)
 238                 $sleep = 2 * $uRTT; // rough time to do get()+set()
 239
 240                 $locked = false; // lock acquired
 241                 $attempts = 0; // failed attempts
 242                 do {
 243                         if ( ++$attempts >= 3 && $sleep <= 5e5 ) {
 244                                 // Exponentially back off after failed attempts to avoid network spam.
 245                                 // About 2*$uRTT*(2^n-1) us of "sleep" happen for the next n attempts.
 246                                 $sleep *= 2;
 247                         }
 248                         usleep( $sleep ); // back off
 249                         $this->clearLastError();
 250                         $locked = $this->add( "{$key}:lock", 1, $expiry );
 251                         if ( $this->getLastError() ) {
 252                                 return false;
 253                         }
 254                 } while ( !$locked && ( microtime( true ) - $timestamp ) < $timeout );
 255
 256                 return $locked;
 257         }
 258
 259         /**
 260          * @param string $key
 261          * @return bool Success
 262          */
 263         public function unlock( $key ) {
 264                 return $this->delete( "{$key}:lock" );
 265         }
 266
 267         /**
 268          * Delete all objects expiring before a certain date.
 269          * @param string $date The reference date in MW format
 270          * @param callable|bool $progressCallback Optional, a function which will be called
 271          *     regularly during long-running operations with the percentage progress
 272          *     as the first parameter.
 273          *
 274          * @return bool Success, false if unimplemented
 275          */
 276         public function deleteObjectsExpiringBefore( $date, $progressCallback = false ) {
 277                 // stub
 278                 return false;
 279         }
 280
 281         /**
 282          * Get an associative array containing the item for each of the keys that have items.
 283          * @param array $keys List of strings
 284          * @param integer $flags Bitfield; supports READ_LATEST [optional]
 285          * @return array
 286          */
 287         public function getMulti( array $keys, $flags = 0 ) {
 288                 $res = array();
 289                 foreach ( $keys as $key ) {
 290                         $val = $this->get( $key );
 291                         if ( $val !== false ) {
 292                                 $res[$key] = $val;
 293                         }
 294                 }
 295                 return $res;
 296         }
 297
 298         /**
 299          * Batch insertion
 300          * @param array $data $key => $value assoc array
 301          * @param int $exptime Either an interval in seconds or a unix timestamp for expiry
 302          * @return bool Success
 303          * @since 1.24
 304          */
 305         public function setMulti( array $data, $exptime = 0 ) {
 306                 $res = true;
 307                 foreach ( $data as $key => $value ) {
 308                         if ( !$this->set( $key, $value, $exptime ) ) {
 309                                 $res = false;
 310                         }
 311                 }
 312                 return $res;
 313         }
 314
 315         /**
 316          * @param string $key
 317          * @param mixed $value
 318          * @param int $exptime
 319          * @return bool Success
 320          */
 321         public function add( $key, $value, $exptime = 0 ) {
 322                 if ( $this->get( $key ) === false ) {
 323                         return $this->set( $key, $value, $exptime );
 324                 }
 325                 return false; // key already set
 326         }
 327
 328         /**
 329          * Increase stored value of $key by $value while preserving its TTL
 330          * @param string $key Key to increase
 331          * @param int $value Value to add to $key (Default 1)
 332          * @return int|bool New value or false on failure
 333          */
 334         public function incr( $key, $value = 1 ) {
 335                 if ( !$this->lock( $key ) ) {
 336                         return false;
 337                 }
 338                 $n = $this->get( $key );
 339                 if ( $this->isInteger( $n ) ) { // key exists?
 340                         $n += intval( $value );
 341                         $this->set( $key, max( 0, $n ) ); // exptime?
 342                 } else {
 343                         $n = false;
 344                 }
 345                 $this->unlock( $key );
 346
 347                 return $n;
 348         }
 349
 350         /**
 351          * Decrease stored value of $key by $value while preserving its TTL
 352          * @param string $key
 353          * @param int $value
 354          * @return int|bool New value or false on failure
 355          */
 356         public function decr( $key, $value = 1 ) {
 357                 return $this->incr( $key, - $value );
 358         }
 359
 360         /**
 361          * Increase stored value of $key by $value while preserving its TTL
 362          *
 363          * This will create the key with value $init and TTL $ttl if not present
 364          *
 365          * @param string $key
 366          * @param int $ttl
 367          * @param int $value
 368          * @param int $init
 369          * @return bool
 370          * @since 1.24
 371          */
 372         public function incrWithInit( $key, $ttl, $value = 1, $init = 1 ) {
 373                 return $this->incr( $key, $value ) ||
 374                         $this->add( $key, (int)$init, $ttl ) || $this->incr( $key, $value );
 375         }
 376
 377         /**
 378          * Get the "last error" registered; clearLastError() should be called manually
 379          * @return int ERR_* constant for the "last error" registry
 380          * @since 1.23
 381          */
 382         public function getLastError() {
 383                 return $this->lastError;
 384         }
 385
 386         /**
 387          * Clear the "last error" registry
 388          * @since 1.23
 389          */
 390         public function clearLastError() {
 391                 $this->lastError = self::ERR_NONE;
 392         }
 393
 394         /**
 395          * Set the "last error" registry
 396          * @param int $err ERR_* constant
 397          * @since 1.23
 398          */
 399         protected function setLastError( $err ) {
 400                 $this->lastError = $err;
 401         }
 402
 403         /**
 404          * Modify a cache update operation array for EventRelayer::notify()
 405          *
 406          * This is used for relayed writes, e.g. for broadcasting a change
 407          * to multiple data-centers. If the array contains a 'val' field
 408          * then the command involves setting a key to that value. Note that
 409          * for simplicity, 'val' is always a simple scalar value. This method
 410          * is used to possibly serialize the value and add any cache-specific
 411          * key/values needed for the relayer daemon (e.g. memcached flags).
 412          *
 413          * @param array $event
 414          * @return array
 415          * @since 1.26
 416          */
 417         public function modifySimpleRelayEvent( array $event ) {
 418                 return $event;
 419         }
 420
 421         /**
 422          * @param string $text
 423          */
 424         protected function debug( $text ) {
 425                 if ( $this->debugMode ) {
 426                         $this->logger->debug( "{class} debug: $text", array(
 427                                 'class' => get_class( $this ),
 428                         ) );
 429                 }
 430         }
 431
 432         /**
 433          * Convert an optionally relative time to an absolute time
 434          * @param int $exptime
 435          * @return int
 436          */
 437         protected function convertExpiry( $exptime ) {
 438                 if ( ( $exptime != 0 ) && ( $exptime < 86400 * 3650 /* 10 years */ ) ) {
 439                         return time() + $exptime;
 440                 } else {
 441                         return $exptime;
 442                 }
 443         }
 444
 445         /**
 446          * Convert an optionally absolute expiry time to a relative time. If an
 447          * absolute time is specified which is in the past, use a short expiry time.
 448          *
 449          * @param int $exptime
 450          * @return int
 451          */
 452         protected function convertToRelative( $exptime ) {
 453                 if ( $exptime >= 86400 * 3650 /* 10 years */ ) {
 454                         $exptime -= time();
 455                         if ( $exptime <= 0 ) {
 456                                 $exptime = 1;
 457                         }
 458                         return $exptime;
 459                 } else {
 460                         return $exptime;
 461                 }
 462         }
 463
 464         /**
 465          * Check if a value is an integer
 466          *
 467          * @param mixed $value
 468          * @return bool
 469          */
 470         protected function isInteger( $value ) {
 471                 return ( is_int( $value ) || ctype_digit( $value ) );
 472         }
 473 }