includes/objectcache/RedisBagOStuff.php

   1 <?php
   2 /**
   3  * Object caching using Redis (http://redis.io/).
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License along
  16  * with this program; if not, write to the Free Software Foundation, Inc.,
  17  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  18  * http://www.gnu.org/copyleft/gpl.html
  19  *
  20  * @file
  21  */
  22
  23 class RedisBagOStuff extends BagOStuff {
  24         /** @var RedisConnectionPool */
  25         protected $redisPool;
  26         /** @var array List of server names */
  27         protected $servers;
  28         /** @var bool */
  29         protected $automaticFailover;
  30
  31         /**
  32          * Construct a RedisBagOStuff object. Parameters are:
  33          *
  34          *   - servers: An array of server names. A server name may be a hostname,
  35          *     a hostname/port combination or the absolute path of a UNIX socket.
  36          *     If a hostname is specified but no port, the standard port number
  37          *     6379 will be used. Required.
  38          *
  39          *   - connectTimeout: The timeout for new connections, in seconds. Optional,
  40          *     default is 1 second.
  41          *
  42          *   - persistent: Set this to true to allow connections to persist across
  43          *     multiple web requests. False by default.
  44          *
  45          *   - password: The authentication password, will be sent to Redis in
  46          *     clear text. Optional, if it is unspecified, no AUTH command will be
  47          *     sent.
  48          *
  49          *   - automaticFailover: If this is false, then each key will be mapped to
  50          *     a single server, and if that server is down, any requests for that key
  51          *     will fail. If this is true, a connection failure will cause the client
  52          *     to immediately try the next server in the list (as determined by a
  53          *     consistent hashing algorithm). True by default. This has the
  54          *     potential to create consistency issues if a server is slow enough to
  55          *     flap, for example if it is in swap death.
  56          * @param array $params
  57          */
  58         function __construct( $params ) {
  59                 $redisConf = array( 'serializer' => 'none' ); // manage that in this class
  60                 foreach ( array( 'connectTimeout', 'persistent', 'password' ) as $opt ) {
  61                         if ( isset( $params[$opt] ) ) {
  62                                 $redisConf[$opt] = $params[$opt];
  63                         }
  64                 }
  65                 $this->redisPool = RedisConnectionPool::singleton( $redisConf );
  66
  67                 $this->servers = $params['servers'];
  68                 if ( isset( $params['automaticFailover'] ) ) {
  69                         $this->automaticFailover = $params['automaticFailover'];
  70                 } else {
  71                         $this->automaticFailover = true;
  72                 }
  73         }
  74
  75         public function get( $key, &$casToken = null ) {
  76                 $section = new ProfileSection( __METHOD__ );
  77
  78                 list( $server, $conn ) = $this->getConnection( $key );
  79                 if ( !$conn ) {
  80                         return false;
  81                 }
  82                 try {
  83                         $value = $conn->get( $key );
  84                         $casToken = $value;
  85                         $result = $this->unserialize( $value );
  86                 } catch ( RedisException $e ) {
  87                         $result = false;
  88                         $this->handleException( $conn, $e );
  89                 }
  90
  91                 $this->logRequest( 'get', $key, $server, $result );
  92                 return $result;
  93         }
  94
  95         public function set( $key, $value, $expiry = 0 ) {
  96                 $section = new ProfileSection( __METHOD__ );
  97
  98                 list( $server, $conn ) = $this->getConnection( $key );
  99                 if ( !$conn ) {
 100                         return false;
 101                 }
 102                 $expiry = $this->convertToRelative( $expiry );
 103                 try {
 104                         if ( $expiry ) {
 105                                 $result = $conn->setex( $key, $expiry, $this->serialize( $value ) );
 106                         } else {
 107                                 // No expiry, that is very different from zero expiry in Redis
 108                                 $result = $conn->set( $key, $this->serialize( $value ) );
 109                         }
 110                 } catch ( RedisException $e ) {
 111                         $result = false;
 112                         $this->handleException( $conn, $e );
 113                 }
 114
 115                 $this->logRequest( 'set', $key, $server, $result );
 116                 return $result;
 117         }
 118
 119         public function cas( $casToken, $key, $value, $expiry = 0 ) {
 120                 $section = new ProfileSection( __METHOD__ );
 121
 122                 list( $server, $conn ) = $this->getConnection( $key );
 123                 if ( !$conn ) {
 124                         return false;
 125                 }
 126                 $expiry = $this->convertToRelative( $expiry );
 127                 try {
 128                         $conn->watch( $key );
 129
 130                         if ( $this->serialize( $this->get( $key ) ) !== $casToken ) {
 131                                 $conn->unwatch();
 132                                 return false;
 133                         }
 134
 135                         // multi()/exec() will fail atomically if the key changed since watch()
 136                         $conn->multi();
 137                         if ( $expiry ) {
 138                                 $conn->setex( $key, $expiry, $this->serialize( $value ) );
 139                         } else {
 140                                 // No expiry, that is very different from zero expiry in Redis
 141                                 $conn->set( $key, $this->serialize( $value ) );
 142                         }
 143                         $result = ( $conn->exec() == array( true ) );
 144                 } catch ( RedisException $e ) {
 145                         $result = false;
 146                         $this->handleException( $conn, $e );
 147                 }
 148
 149                 $this->logRequest( 'cas', $key, $server, $result );
 150                 return $result;
 151         }
 152
 153         public function delete( $key, $time = 0 ) {
 154                 $section = new ProfileSection( __METHOD__ );
 155
 156                 list( $server, $conn ) = $this->getConnection( $key );
 157                 if ( !$conn ) {
 158                         return false;
 159                 }
 160                 try {
 161                         $conn->delete( $key );
 162                         // Return true even if the key didn't exist
 163                         $result = true;
 164                 } catch ( RedisException $e ) {
 165                         $result = false;
 166                         $this->handleException( $conn, $e );
 167                 }
 168
 169                 $this->logRequest( 'delete', $key, $server, $result );
 170                 return $result;
 171         }
 172
 173         public function getMulti( array $keys ) {
 174                 $section = new ProfileSection( __METHOD__ );
 175
 176                 $batches = array();
 177                 $conns = array();
 178                 foreach ( $keys as $key ) {
 179                         list( $server, $conn ) = $this->getConnection( $key );
 180                         if ( !$conn ) {
 181                                 continue;
 182                         }
 183                         $conns[$server] = $conn;
 184                         $batches[$server][] = $key;
 185                 }
 186                 $result = array();
 187                 foreach ( $batches as $server => $batchKeys ) {
 188                         $conn = $conns[$server];
 189                         try {
 190                                 $conn->multi( Redis::PIPELINE );
 191                                 foreach ( $batchKeys as $key ) {
 192                                         $conn->get( $key );
 193                                 }
 194                                 $batchResult = $conn->exec();
 195                                 if ( $batchResult === false ) {
 196                                         $this->debug( "multi request to $server failed" );
 197                                         continue;
 198                                 }
 199                                 foreach ( $batchResult as $i => $value ) {
 200                                         if ( $value !== false ) {
 201                                                 $result[$batchKeys[$i]] = $this->unserialize( $value );
 202                                         }
 203                                 }
 204                         } catch ( RedisException $e ) {
 205                                 $this->handleException( $conn, $e );
 206                         }
 207                 }
 208
 209                 $this->debug( "getMulti for " . count( $keys ) . " keys " .
 210                         "returned " . count( $result ) . " results" );
 211                 return $result;
 212         }
 213
 214         public function add( $key, $value, $expiry = 0 ) {
 215                 $section = new ProfileSection( __METHOD__ );
 216
 217                 list( $server, $conn ) = $this->getConnection( $key );
 218                 if ( !$conn ) {
 219                         return false;
 220                 }
 221                 $expiry = $this->convertToRelative( $expiry );
 222                 try {
 223                         if ( $expiry ) {
 224                                 $conn->multi();
 225                                 $conn->setnx( $key, $this->serialize( $value ) );
 226                                 $conn->expire( $key, $expiry );
 227                                 $result = ( $conn->exec() == array( true, true ) );
 228                         } else {
 229                                 $result = $conn->setnx( $key, $this->serialize( $value ) );
 230                         }
 231                 } catch ( RedisException $e ) {
 232                         $result = false;
 233                         $this->handleException( $conn, $e );
 234                 }
 235
 236                 $this->logRequest( 'add', $key, $server, $result );
 237                 return $result;
 238         }
 239
 240         /**
 241          * Non-atomic implementation of incr().
 242          *
 243          * Probably all callers actually want incr() to atomically initialise
 244          * values to zero if they don't exist, as provided by the Redis INCR
 245          * command. But we are constrained by the memcached-like interface to
 246          * return null in that case. Once the key exists, further increments are
 247          * atomic.
 248          * @param string $key
 249          * @param int $value
 250          * @param bool|mixed
 251          */
 252         public function incr( $key, $value = 1 ) {
 253                 $section = new ProfileSection( __METHOD__ );
 254
 255                 list( $server, $conn ) = $this->getConnection( $key );
 256                 if ( !$conn ) {
 257                         return false;
 258                 }
 259                 if ( !$conn->exists( $key ) ) {
 260                         return null;
 261                 }
 262                 try {
 263                         $result = $this->unserialize( $conn->incrBy( $key, $value ) );
 264                 } catch ( RedisException $e ) {
 265                         $result = false;
 266                         $this->handleException( $conn, $e );
 267                 }
 268
 269                 $this->logRequest( 'incr', $key, $server, $result );
 270                 return $result;
 271         }
 272
 273         /**
 274          * @param mixed $data
 275          * @return string
 276          */
 277         protected function serialize( $data ) {
 278                 // Ignore digit strings and ints so INCR/DECR work
 279                 return ( is_int( $data ) || ctype_digit( $data ) ) ? $data : serialize( $data );
 280         }
 281
 282         /**
 283          * @param string $data
 284          * @return mixed
 285          */
 286         protected function unserialize( $data ) {
 287                 // Ignore digit strings and ints so INCR/DECR work
 288                 return ( is_int( $data ) || ctype_digit( $data ) ) ? $data : unserialize( $data );
 289         }
 290
 291         /**
 292          * Get a Redis object with a connection suitable for fetching the specified key
 293          * @return array (server, RedisConnRef) or (false, false)
 294          */
 295         protected function getConnection( $key ) {
 296                 if ( count( $this->servers ) === 1 ) {
 297                         $candidates = $this->servers;
 298                 } else {
 299                         $candidates = $this->servers;
 300                         ArrayUtils::consistentHashSort( $candidates, $key, '/' );
 301                         if ( !$this->automaticFailover ) {
 302                                 $candidates = array_slice( $candidates, 0, 1 );
 303                         }
 304                 }
 305
 306                 foreach ( $candidates as $server ) {
 307                         $conn = $this->redisPool->getConnection( $server );
 308                         if ( $conn ) {
 309                                 return array( $server, $conn );
 310                         }
 311                 }
 312                 $this->setLastError( BagOStuff::ERR_UNREACHABLE );
 313                 return array( false, false );
 314         }
 315
 316         /**
 317          * Log a fatal error
 318          * @param string $msg
 319          */
 320         protected function logError( $msg ) {
 321                 wfDebugLog( 'redis', "Redis error: $msg" );
 322         }
 323
 324         /**
 325          * The redis extension throws an exception in response to various read, write
 326          * and protocol errors. Sometimes it also closes the connection, sometimes
 327          * not. The safest response for us is to explicitly destroy the connection
 328          * object and let it be reopened during the next request.
 329          * @param RedisConnRef $conn
 330          * @param Exception $e
 331          */
 332         protected function handleException( RedisConnRef $conn, $e ) {
 333                 $this->setLastError( BagOStuff::ERR_UNEXPECTED );
 334                 $this->redisPool->handleError( $conn, $e );
 335         }
 336
 337         /**
 338          * Send information about a single request to the debug log
 339          * @param string $method
 340          * @param string $key
 341          * @param string $server
 342          * @param bool $result
 343          */
 344         public function logRequest( $method, $key, $server, $result ) {
 345                 $this->debug( "$method $key on $server: " .
 346                         ( $result === false ? "failure" : "success" ) );
 347         }
 348 }