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          */
  57         function __construct( $params ) {
  58                 $redisConf = array( 'serializer' => 'none' ); // manage that in this class
  59                 foreach ( array( 'connectTimeout', 'persistent', 'password' ) as $opt ) {
  60                         if ( isset( $params[$opt] ) ) {
  61                                 $redisConf[$opt] = $params[$opt];
  62                         }
  63                 }
  64                 $this->redisPool = RedisConnectionPool::singleton( $redisConf );
  65
  66                 $this->servers = $params['servers'];
  67                 if ( isset( $params['automaticFailover'] ) ) {
  68                         $this->automaticFailover = $params['automaticFailover'];
  69                 } else {
  70                         $this->automaticFailover = true;
  71                 }
  72         }
  73
  74         public function get( $key, &$casToken = null ) {
  75                 $section = new ProfileSection( __METHOD__ );
  76
  77                 list( $server, $conn ) = $this->getConnection( $key );
  78                 if ( !$conn ) {
  79                         return false;
  80                 }
  81                 try {
  82                         $value = $conn->get( $key );
  83                         $casToken = $value;
  84                         $result = $this->unserialize( $value );
  85                 } catch ( RedisException $e ) {
  86                         $result = false;
  87                         $this->handleException( $conn, $e );
  88                 }
  89
  90                 $this->logRequest( 'get', $key, $server, $result );
  91                 return $result;
  92         }
  93
  94         public function set( $key, $value, $expiry = 0 ) {
  95                 $section = new ProfileSection( __METHOD__ );
  96
  97                 list( $server, $conn ) = $this->getConnection( $key );
  98                 if ( !$conn ) {
  99                         return false;
 100                 }
 101                 $expiry = $this->convertToRelative( $expiry );
 102                 try {
 103                         if ( $expiry ) {
 104                                 $result = $conn->setex( $key, $expiry, $this->serialize( $value ) );
 105                         } else {
 106                                 // No expiry, that is very different from zero expiry in Redis
 107                                 $result = $conn->set( $key, $this->serialize( $value ) );
 108                         }
 109                 } catch ( RedisException $e ) {
 110                         $result = false;
 111                         $this->handleException( $conn, $e );
 112                 }
 113
 114                 $this->logRequest( 'set', $key, $server, $result );
 115                 return $result;
 116         }
 117
 118         public function cas( $casToken, $key, $value, $expiry = 0 ) {
 119                 $section = new ProfileSection( __METHOD__ );
 120
 121                 list( $server, $conn ) = $this->getConnection( $key );
 122                 if ( !$conn ) {
 123                         return false;
 124                 }
 125                 $expiry = $this->convertToRelative( $expiry );
 126                 try {
 127                         $conn->watch( $key );
 128
 129                         if ( $this->serialize( $this->get( $key ) ) !== $casToken ) {
 130                                 $conn->unwatch();
 131                                 return false;
 132                         }
 133
 134                         // multi()/exec() will fail atomically if the key changed since watch()
 135                         $conn->multi();
 136                         if ( $expiry ) {
 137                                 $conn->setex( $key, $expiry, $this->serialize( $value ) );
 138                         } else {
 139                                 // No expiry, that is very different from zero expiry in Redis
 140                                 $conn->set( $key, $this->serialize( $value ) );
 141                         }
 142                         $result = ( $conn->exec() == array( true ) );
 143                 } catch ( RedisException $e ) {
 144                         $result = false;
 145                         $this->handleException( $conn, $e );
 146                 }
 147
 148                 $this->logRequest( 'cas', $key, $server, $result );
 149                 return $result;
 150         }
 151
 152         public function delete( $key, $time = 0 ) {
 153                 $section = new ProfileSection( __METHOD__ );
 154
 155                 list( $server, $conn ) = $this->getConnection( $key );
 156                 if ( !$conn ) {
 157                         return false;
 158                 }
 159                 try {
 160                         $conn->delete( $key );
 161                         // Return true even if the key didn't exist
 162                         $result = true;
 163                 } catch ( RedisException $e ) {
 164                         $result = false;
 165                         $this->handleException( $conn, $e );
 166                 }
 167
 168                 $this->logRequest( 'delete', $key, $server, $result );
 169                 return $result;
 170         }
 171
 172         public function getMulti( array $keys ) {
 173                 $section = new ProfileSection( __METHOD__ );
 174
 175                 $batches = array();
 176                 $conns = array();
 177                 foreach ( $keys as $key ) {
 178                         list( $server, $conn ) = $this->getConnection( $key );
 179                         if ( !$conn ) {
 180                                 continue;
 181                         }
 182                         $conns[$server] = $conn;
 183                         $batches[$server][] = $key;
 184                 }
 185                 $result = array();
 186                 foreach ( $batches as $server => $batchKeys ) {
 187                         $conn = $conns[$server];
 188                         try {
 189                                 $conn->multi( Redis::PIPELINE );
 190                                 foreach ( $batchKeys as $key ) {
 191                                         $conn->get( $key );
 192                                 }
 193                                 $batchResult = $conn->exec();
 194                                 if ( $batchResult === false ) {
 195                                         $this->debug( "multi request to $server failed" );
 196                                         continue;
 197                                 }
 198                                 foreach ( $batchResult as $i => $value ) {
 199                                         if ( $value !== false ) {
 200                                                 $result[$batchKeys[$i]] = $this->unserialize( $value );
 201                                         }
 202                                 }
 203                         } catch ( RedisException $e ) {
 204                                 $this->handleException( $conn, $e );
 205                         }
 206                 }
 207
 208                 $this->debug( "getMulti for " . count( $keys ) . " keys " .
 209                         "returned " . count( $result ) . " results" );
 210                 return $result;
 211         }
 212
 213         public function add( $key, $value, $expiry = 0 ) {
 214                 $section = new ProfileSection( __METHOD__ );
 215
 216                 list( $server, $conn ) = $this->getConnection( $key );
 217                 if ( !$conn ) {
 218                         return false;
 219                 }
 220                 $expiry = $this->convertToRelative( $expiry );
 221                 try {
 222                         if ( $expiry ) {
 223                                 $conn->multi();
 224                                 $conn->setnx( $key, $this->serialize( $value ) );
 225                                 $conn->expire( $key, $expiry );
 226                                 $result = ( $conn->exec() == array( true, true ) );
 227                         } else {
 228                                 $result = $conn->setnx( $key, $this->serialize( $value ) );
 229                         }
 230                 } catch ( RedisException $e ) {
 231                         $result = false;
 232                         $this->handleException( $conn, $e );
 233                 }
 234
 235                 $this->logRequest( 'add', $key, $server, $result );
 236                 return $result;
 237         }
 238
 239         /**
 240          * Non-atomic implementation of incr().
 241          *
 242          * Probably all callers actually want incr() to atomically initialise
 243          * values to zero if they don't exist, as provided by the Redis INCR
 244          * command. But we are constrained by the memcached-like interface to
 245          * return null in that case. Once the key exists, further increments are
 246          * atomic.
 247          */
 248         public function incr( $key, $value = 1 ) {
 249                 $section = new ProfileSection( __METHOD__ );
 250
 251                 list( $server, $conn ) = $this->getConnection( $key );
 252                 if ( !$conn ) {
 253                         return false;
 254                 }
 255                 if ( !$conn->exists( $key ) ) {
 256                         return null;
 257                 }
 258                 try {
 259                         $result = $this->unserialize( $conn->incrBy( $key, $value ) );
 260                 } catch ( RedisException $e ) {
 261                         $result = false;
 262                         $this->handleException( $conn, $e );
 263                 }
 264
 265                 $this->logRequest( 'incr', $key, $server, $result );
 266                 return $result;
 267         }
 268
 269         /**
 270          * @param mixed $data
 271          * @return string
 272          */
 273         protected function serialize( $data ) {
 274                 // Ignore digit strings and ints so INCR/DECR work
 275                 return ( is_int( $data ) || ctype_digit( $data ) ) ? $data : serialize( $data );
 276         }
 277
 278         /**
 279          * @param string $data
 280          * @return mixed
 281          */
 282         protected function unserialize( $data ) {
 283                 // Ignore digit strings and ints so INCR/DECR work
 284                 return ( is_int( $data ) || ctype_digit( $data ) ) ? $data : unserialize( $data );
 285         }
 286
 287         /**
 288          * Get a Redis object with a connection suitable for fetching the specified key
 289          * @return Array (server, RedisConnRef) or (false, false)
 290          */
 291         protected function getConnection( $key ) {
 292                 if ( count( $this->servers ) === 1 ) {
 293                         $candidates = $this->servers;
 294                 } else {
 295                         $candidates = $this->servers;
 296                         ArrayUtils::consistentHashSort( $candidates, $key, '/' );
 297                         if ( !$this->automaticFailover ) {
 298                                 $candidates = array_slice( $candidates, 0, 1 );
 299                         }
 300                 }
 301
 302                 foreach ( $candidates as $server ) {
 303                         $conn = $this->redisPool->getConnection( $server );
 304                         if ( $conn ) {
 305                                 return array( $server, $conn );
 306                         }
 307                 }
 308                 $this->setLastError( BagOStuff::ERR_UNREACHABLE );
 309                 return array( false, false );
 310         }
 311
 312         /**
 313          * Log a fatal error
 314          */
 315         protected function logError( $msg ) {
 316                 wfDebugLog( 'redis', "Redis error: $msg" );
 317         }
 318
 319         /**
 320          * The redis extension throws an exception in response to various read, write
 321          * and protocol errors. Sometimes it also closes the connection, sometimes
 322          * not. The safest response for us is to explicitly destroy the connection
 323          * object and let it be reopened during the next request.
 324          */
 325         protected function handleException( RedisConnRef $conn, $e ) {
 326                 $this->setLastError( BagOStuff::ERR_UNEXPECTED );
 327                 $this->redisPool->handleError( $conn, $e );
 328         }
 329
 330         /**
 331          * Send information about a single request to the debug log
 332          */
 333         public function logRequest( $method, $key, $server, $result ) {
 334                 $this->debug( "$method $key on $server: " .
 335                         ( $result === false ? "failure" : "success" ) );
 336         }
 337 }