includes/libs/objectcache/ReplicatedBagOStuff.php

   1 <?php
   2 /**
   3  * This program is free software; you can redistribute it and/or modify
   4  * it under the terms of the GNU General Public License as published by
   5  * the Free Software Foundation; either version 2 of the License, or
   6  * (at your option) any later version.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  11  * GNU General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU General Public License along
  14  * with this program; if not, write to the Free Software Foundation, Inc.,
  15  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  16  * http://www.gnu.org/copyleft/gpl.html
  17  *
  18  * @file
  19  * @ingroup Cache
  20  */
  21 use Wikimedia\ObjectFactory;
  22
  23 /**
  24  * A cache class that directs writes to one set of servers and reads to
  25  * another. This assumes that the servers used for reads are setup to replica DB
  26  * those that writes go to. This can easily be used with redis for example.
  27  *
  28  * In the WAN scenario (e.g. multi-datacenter case), this is useful when
  29  * writes are rare or they usually take place in the primary datacenter.
  30  *
  31  * @ingroup Cache
  32  * @since 1.26
  33  */
  34 class ReplicatedBagOStuff extends BagOStuff {
  35         /** @var BagOStuff */
  36         private $writeStore;
  37         /** @var BagOStuff */
  38         private $readStore;
  39
  40         /** @var int Seconds to read from the master source for a key after writing to it */
  41         private $consistencyWindow;
  42         /** @var float[] Map of (key => UNIX timestamp) */
  43         private $lastKeyWrites = [];
  44
  45         /** @var int Max expected delay (in seconds) for writes to reach replicas */
  46         const MAX_WRITE_DELAY = 5;
  47
  48         /**
  49          * Constructor. Parameters are:
  50          *   - writeFactory: ObjectFactory::getObjectFromSpec array yeilding BagOStuff.
  51          *      This object will be used for writes (e.g. the master DB).
  52          *   - readFactory: ObjectFactory::getObjectFromSpec array yeilding BagOStuff.
  53          *      This object will be used for reads (e.g. a replica DB).
  54          *   - sessionConsistencyWindow: Seconds to read from the master source for a key
  55          *      after writing to it. [Default: ReplicatedBagOStuff::MAX_WRITE_DELAY]
  56          *
  57          * @param array $params
  58          * @throws InvalidArgumentException
  59          */
  60         public function __construct( $params ) {
  61                 parent::__construct( $params );
  62
  63                 if ( !isset( $params['writeFactory'] ) ) {
  64                         throw new InvalidArgumentException(
  65                                 __METHOD__ . ': the "writeFactory" parameter is required' );
  66                 } elseif ( !isset( $params['readFactory'] ) ) {
  67                         throw new InvalidArgumentException(
  68                                 __METHOD__ . ': the "readFactory" parameter is required' );
  69                 }
  70
  71                 $this->consistencyWindow = $params['sessionConsistencyWindow'] ?? self::MAX_WRITE_DELAY;
  72                 $this->writeStore = ( $params['writeFactory'] instanceof BagOStuff )
  73                         ? $params['writeFactory']
  74                         : ObjectFactory::getObjectFromSpec( $params['writeFactory'] );
  75                 $this->readStore = ( $params['readFactory'] instanceof BagOStuff )
  76                         ? $params['readFactory']
  77                         : ObjectFactory::getObjectFromSpec( $params['readFactory'] );
  78                 $this->attrMap = $this->mergeFlagMaps( [ $this->readStore, $this->writeStore ] );
  79         }
  80
  81         public function setDebug( $enabled ) {
  82                 parent::setDebug( $enabled );
  83                 $this->writeStore->setDebug( $enabled );
  84                 $this->readStore->setDebug( $enabled );
  85         }
  86
  87         public function get( $key, $flags = 0 ) {
  88                 return (
  89                         $this->hadRecentSessionWrite( [ $key ] ) ||
  90                         $this->fieldHasFlags( $flags, self::READ_LATEST )
  91                 )
  92                         ? $this->writeStore->get( $key, $flags )
  93                         : $this->readStore->get( $key, $flags );
  94         }
  95
  96         public function set( $key, $value, $exptime = 0, $flags = 0 ) {
  97                 $this->remarkRecentSessionWrite( [ $key ] );
  98
  99                 return $this->writeStore->set( $key, $value, $exptime, $flags );
 100         }
 101
 102         public function delete( $key, $flags = 0 ) {
 103                 $this->remarkRecentSessionWrite( [ $key ] );
 104
 105                 return $this->writeStore->delete( $key, $flags );
 106         }
 107
 108         public function add( $key, $value, $exptime = 0, $flags = 0 ) {
 109                 $this->remarkRecentSessionWrite( [ $key ] );
 110
 111                 return $this->writeStore->add( $key, $value, $exptime, $flags );
 112         }
 113
 114         public function merge( $key, callable $callback, $exptime = 0, $attempts = 10, $flags = 0 ) {
 115                 $this->remarkRecentSessionWrite( [ $key ] );
 116
 117                 return $this->writeStore->merge( $key, $callback, $exptime, $attempts, $flags );
 118         }
 119
 120         public function changeTTL( $key, $exptime = 0, $flags = 0 ) {
 121                 $this->remarkRecentSessionWrite( [ $key ] );
 122
 123                 return $this->writeStore->changeTTL( $key, $exptime, $flags );
 124         }
 125
 126         public function lock( $key, $timeout = 6, $expiry = 6, $rclass = '' ) {
 127                 return $this->writeStore->lock( $key, $timeout, $expiry, $rclass );
 128         }
 129
 130         public function unlock( $key ) {
 131                 return $this->writeStore->unlock( $key );
 132         }
 133
 134         public function deleteObjectsExpiringBefore(
 135                 $timestamp,
 136                 callable $progress = null,
 137                 $limit = INF
 138         ) {
 139                 return $this->writeStore->deleteObjectsExpiringBefore( $timestamp, $progress, $limit );
 140         }
 141
 142         public function getMulti( array $keys, $flags = 0 ) {
 143                 return (
 144                         $this->hadRecentSessionWrite( $keys ) ||
 145                         $this->fieldHasFlags( $flags, self::READ_LATEST )
 146                 )
 147                         ? $this->writeStore->getMulti( $keys, $flags )
 148                         : $this->readStore->getMulti( $keys, $flags );
 149         }
 150
 151         public function setMulti( array $data, $exptime = 0, $flags = 0 ) {
 152                 $this->remarkRecentSessionWrite( array_keys( $data ) );
 153
 154                 return $this->writeStore->setMulti( $data, $exptime, $flags );
 155         }
 156
 157         public function deleteMulti( array $keys, $flags = 0 ) {
 158                 $this->remarkRecentSessionWrite( $keys );
 159
 160                 return $this->writeStore->deleteMulti( $keys, $flags );
 161         }
 162
 163         public function changeTTLMulti( array $keys, $exptime, $flags = 0 ) {
 164                 $this->remarkRecentSessionWrite( $keys );
 165
 166                 return $this->writeStore->changeTTLMulti( $keys, $exptime, $flags );
 167         }
 168
 169         public function incr( $key, $value = 1, $flags = 0 ) {
 170                 $this->remarkRecentSessionWrite( [ $key ] );
 171
 172                 return $this->writeStore->incr( $key, $value, $flags );
 173         }
 174
 175         public function decr( $key, $value = 1, $flags = 0 ) {
 176                 $this->remarkRecentSessionWrite( [ $key ] );
 177
 178                 return $this->writeStore->decr( $key, $value, $flags );
 179         }
 180
 181         public function incrWithInit( $key, $exptime, $value = 1, $init = null, $flags = 0 ) {
 182                 $this->remarkRecentSessionWrite( [ $key ] );
 183
 184                 return $this->writeStore->incrWithInit( $key, $exptime, $value, $init, $flags );
 185         }
 186
 187         public function getLastError() {
 188                 return ( $this->writeStore->getLastError() !== self::ERR_NONE )
 189                         ? $this->writeStore->getLastError()
 190                         : $this->readStore->getLastError();
 191         }
 192
 193         public function clearLastError() {
 194                 $this->writeStore->clearLastError();
 195                 $this->readStore->clearLastError();
 196         }
 197
 198         public function makeKeyInternal( $keyspace, $args ) {
 199                 return $this->writeStore->makeKeyInternal( ...func_get_args() );
 200         }
 201
 202         public function makeKey( $class, ...$components ) {
 203                 return $this->writeStore->makeKey( ...func_get_args() );
 204         }
 205
 206         public function makeGlobalKey( $class, ...$components ) {
 207                 return $this->writeStore->makeGlobalKey( ...func_get_args() );
 208         }
 209
 210         public function addBusyCallback( callable $workCallback ) {
 211                 $this->writeStore->addBusyCallback( $workCallback );
 212         }
 213
 214         public function setMockTime( &$time ) {
 215                 parent::setMockTime( $time );
 216                 $this->writeStore->setMockTime( $time );
 217                 $this->readStore->setMockTime( $time );
 218         }
 219
 220         /**
 221          * @param string[] $keys
 222          * @return bool
 223          */
 224         private function hadRecentSessionWrite( array $keys ) {
 225                 $now = $this->getCurrentTime();
 226                 foreach ( $keys as $key ) {
 227                         $ts = $this->lastKeyWrites[$key] ?? 0;
 228                         if ( $ts && ( $now - $ts ) <= $this->consistencyWindow ) {
 229                                 return true;
 230                         }
 231                 }
 232
 233                 return false;
 234         }
 235
 236         /**
 237          * @param string[] $keys
 238          */
 239         private function remarkRecentSessionWrite( array $keys ) {
 240                 $now = $this->getCurrentTime();
 241                 foreach ( $keys as $key ) {
 242                         unset( $this->lastKeyWrites[$key] ); // move to the end
 243                         $this->lastKeyWrites[$key] = $now;
 244                 }
 245                 // Prune out the map if the first key is obsolete
 246                 if ( ( $now - reset( $this->lastKeyWrites ) ) > $this->consistencyWindow ) {
 247                         $this->lastKeyWrites = array_filter(
 248                                 $this->lastKeyWrites,
 249                                 function ( $timestamp ) use ( $now ) {
 250                                         return ( ( $now - $timestamp ) <= $this->consistencyWindow );
 251                                 }
 252                         );
 253                 }
 254         }
 255 }