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 class RedisBagOStuff extends BagOStuff {
  23         /** @var RedisConnectionPool */
  24         protected $redisPool;
  25         /** @var Array List of server names */
  26         protected $servers;
  27         /** @var bool */
  28         protected $automaticFailover;
  29
  30         /**
  31          * Construct a RedisBagOStuff object. Parameters are:
  32          *
  33          *   - servers: An array of server names. A server name may be a hostname,
  34          *     a hostname/port combination or the absolute path of a UNIX socket.
  35          *     If a hostname is specified but no port, the standard port number
  36          *     6379 will be used. Required.
  37          *
  38          *   - connectTimeout: The timeout for new connections, in seconds. Optional,
  39          *     default is 1 second.
  40          *
  41          *   - persistent: Set this to true to allow connections to persist across
  42          *     multiple web requests. False by default.
  43          *
  44          *   - password: The authentication password, will be sent to Redis in
  45          *     clear text. Optional, if it is unspecified, no AUTH command will be
  46          *     sent.
  47          *
  48          *   - automaticFailover: If this is false, then each key will be mapped to
  49          *     a single server, and if that server is down, any requests for that key
  50          *     will fail. If this is true, a connection failure will cause the client
  51          *     to immediately try the next server in the list (as determined by a
  52          *     consistent hashing algorithm). True by default. This has the
  53          *     potential to create consistency issues if a server is slow enough to
  54          *     flap, for example if it is in swap death.
  55          */
  56         function __construct( $params ) {
  57                 $redisConf = array( 'serializer' => 'php' );
  58                 foreach ( array( 'connectTimeout', 'persistent', 'password' ) as $opt ) {
  59                         if ( isset( $params[$opt] ) ) {
  60                                 $redisConf[$opt] = $params[$opt];
  61                         }
  62                 }
  63                 $this->redisPool = RedisConnectionPool::singleton( $redisConf );
  64
  65                 $this->servers = $params['servers'];
  66                 if ( isset( $params['automaticFailover'] ) ) {
  67                         $this->automaticFailover = $params['automaticFailover'];
  68                 } else {
  69                         $this->automaticFailover = true;
  70                 }
  71         }
  72
  73         public function get( $key, &$casToken = null ) {
  74                 wfProfileIn( __METHOD__ );
  75                 list( $server, $conn ) = $this->getConnection( $key );
  76                 if ( !$conn ) {
  77                         wfProfileOut( __METHOD__ );
  78                         return false;
  79                 }
  80                 try {
  81                         $result = $conn->get( $key );
  82                 } catch ( RedisException $e ) {
  83                         $result = false;
  84                         $this->handleException( $server, $conn, $e );
  85                 }
  86                 $casToken = $result;
  87                 $this->logRequest( 'get', $key, $server, $result );
  88                 wfProfileOut( __METHOD__ );
  89                 return $result;
  90         }
  91
  92         public function set( $key, $value, $expiry = 0 ) {
  93                 wfProfileIn( __METHOD__ );
  94                 list( $server, $conn ) = $this->getConnection( $key );
  95                 if ( !$conn ) {
  96                         wfProfileOut( __METHOD__ );
  97                         return false;
  98                 }
  99                 $expiry = $this->convertToRelative( $expiry );
 100                 try {
 101                         if ( !$expiry ) {
 102                                 // No expiry, that is very different from zero expiry in Redis
 103                                 $result = $conn->set( $key, $value );
 104                         } else {
 105                                 $result = $conn->setex( $key, $expiry, $value );
 106                         }
 107                 } catch ( RedisException $e ) {
 108                         $result = false;
 109                         $this->handleException( $server, $conn, $e );
 110                 }
 111
 112                 $this->logRequest( 'set', $key, $server, $result );
 113                 wfProfileOut( __METHOD__ );
 114                 return $result;
 115         }
 116
 117         public function cas( $casToken, $key, $value, $expiry = 0 ) {
 118                 wfProfileIn( __METHOD__ );
 119                 list( $server, $conn ) = $this->getConnection( $key );
 120                 if ( !$conn ) {
 121                         wfProfileOut( __METHOD__ );
 122                         return false;
 123                 }
 124                 $expiry = $this->convertToRelative( $expiry );
 125                 try {
 126                         $conn->watch( $key );
 127
 128                         if ( $this->get( $key ) !== $casToken ) {
 129                                 wfProfileOut( __METHOD__ );
 130                                 return false;
 131                         }
 132
 133                         $conn->multi();
 134
 135                         if ( !$expiry ) {
 136                                 // No expiry, that is very different from zero expiry in Redis
 137                                 $conn->set( $key, $value );
 138                         } else {
 139                                 $conn->setex( $key, $expiry, $value );
 140                         }
 141
 142                         $result = $conn->exec();
 143                 } catch ( RedisException $e ) {
 144                         $result = false;
 145                         $this->handleException( $server, $conn, $e );
 146                 }
 147
 148                 $this->logRequest( 'cas', $key, $server, $result );
 149                 wfProfileOut( __METHOD__ );
 150                 return $result;
 151         }
 152
 153         public function delete( $key, $time = 0 ) {
 154                 wfProfileIn( __METHOD__ );
 155                 list( $server, $conn ) = $this->getConnection( $key );
 156                 if ( !$conn ) {
 157                         wfProfileOut( __METHOD__ );
 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( $server, $conn, $e );
 167                 }
 168                 $this->logRequest( 'delete', $key, $server, $result );
 169                 wfProfileOut( __METHOD__ );
 170                 return $result;
 171         }
 172
 173         public function getMulti( array $keys ) {
 174                 wfProfileIn( __METHOD__ );
 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]] = $value;
 201                                         }
 202                                 }
 203                         } catch ( RedisException $e ) {
 204                                 $this->handleException( $server, $conn, $e );
 205                         }
 206                 }
 207
 208                 $this->debug( "getMulti for " . count( $keys ) . " keys " .
 209                         "returned " . count( $result ) . " results" );
 210                 wfProfileOut( __METHOD__ );
 211                 return $result;
 212         }
 213
 214         public function add( $key, $value, $expiry = 0 ) {
 215                 wfProfileIn( __METHOD__ );
 216                 list( $server, $conn ) = $this->getConnection( $key );
 217                 if ( !$conn ) {
 218                         wfProfileOut( __METHOD__ );
 219                         return false;
 220                 }
 221                 $expiry = $this->convertToRelative( $expiry );
 222                 try {
 223                         $result = $conn->setnx( $key, $value );
 224                         if ( $result && $expiry ) {
 225                                 $conn->expire( $key, $expiry );
 226                         }
 227                 } catch ( RedisException $e ) {
 228                         $result = false;
 229                         $this->handleException( $server, $conn, $e );
 230                 }
 231                 $this->logRequest( 'add', $key, $server, $result );
 232                 wfProfileOut( __METHOD__ );
 233                 return $result;
 234         }
 235
 236         /**
 237          * Non-atomic implementation of replace(). Could perhaps be done atomically
 238          * with WATCH or scripting, but this function is rarely used.
 239          */
 240         public function replace( $key, $value, $expiry = 0 ) {
 241                 wfProfileIn( __METHOD__ );
 242                 list( $server, $conn ) = $this->getConnection( $key );
 243                 if ( !$conn ) {
 244                         wfProfileOut( __METHOD__ );
 245                         return false;
 246                 }
 247                 if ( !$conn->exists( $key ) ) {
 248                         wfProfileOut( __METHOD__ );
 249                         return false;
 250                 }
 251
 252                 $expiry = $this->convertToRelative( $expiry );
 253                 try {
 254                         if ( !$expiry ) {
 255                                 $result = $conn->set( $key, $value );
 256                         } else {
 257                                 $result = $conn->setex( $key, $expiry, $value );
 258                         }
 259                 } catch ( RedisException $e ) {
 260                         $result = false;
 261                         $this->handleException( $server, $conn, $e );
 262                 }
 263
 264                 $this->logRequest( 'replace', $key, $server, $result );
 265                 wfProfileOut( __METHOD__ );
 266                 return $result;
 267         }
 268
 269         /**
 270          * Non-atomic implementation of incr().
 271          *
 272          * Probably all callers actually want incr() to atomically initialise
 273          * values to zero if they don't exist, as provided by the Redis INCR
 274          * command. But we are constrained by the memcached-like interface to
 275          * return null in that case. Once the key exists, further increments are
 276          * atomic.
 277          */
 278         public function incr( $key, $value = 1 ) {
 279                 wfProfileIn( __METHOD__ );
 280                 list( $server, $conn ) = $this->getConnection( $key );
 281                 if ( !$conn ) {
 282                         wfProfileOut( __METHOD__ );
 283                         return false;
 284                 }
 285                 if ( !$conn->exists( $key ) ) {
 286                         wfProfileOut( __METHOD__ );
 287                         return null;
 288                 }
 289                 try {
 290                         $result = $conn->incrBy( $key, $value );
 291                 } catch ( RedisException $e ) {
 292                         $result = false;
 293                         $this->handleException( $server, $conn, $e );
 294                 }
 295
 296                 $this->logRequest( 'incr', $key, $server, $result );
 297                 wfProfileOut( __METHOD__ );
 298                 return $result;
 299         }
 300
 301         /**
 302          * Get a Redis object with a connection suitable for fetching the specified key
 303          * @return Array (server, RedisConnRef) or (false, false)
 304          */
 305         protected function getConnection( $key ) {
 306                 if ( count( $this->servers ) === 1 ) {
 307                         $candidates = $this->servers;
 308                 } else {
 309                         $candidates = $this->servers;
 310                         ArrayUtils::consistentHashSort( $candidates, $key, '/' );
 311                         if ( !$this->automaticFailover ) {
 312                                 $candidates = array_slice( $candidates, 0, 1 );
 313                         }
 314                 }
 315
 316                 foreach ( $candidates as $server ) {
 317                         $conn = $this->redisPool->getConnection( $server );
 318                         if ( $conn ) {
 319                                 return array( $server, $conn );
 320                         }
 321                 }
 322                 return array( false, false );
 323         }
 324
 325         /**
 326          * Log a fatal error
 327          */
 328         protected function logError( $msg ) {
 329                 wfDebugLog( 'redis', "Redis error: $msg\n" );
 330         }
 331
 332         /**
 333          * The redis extension throws an exception in response to various read, write
 334          * and protocol errors. Sometimes it also closes the connection, sometimes
 335          * not. The safest response for us is to explicitly destroy the connection
 336          * object and let it be reopened during the next request.
 337          */
 338         protected function handleException( $server, RedisConnRef $conn, $e ) {
 339                 $this->redisPool->handleException( $server, $conn, $e );
 340         }
 341
 342         /**
 343          * Send information about a single request to the debug log
 344          */
 345         public function logRequest( $method, $key, $server, $result ) {
 346                 $this->debug( "$method $key on $server: " .
 347                         ( $result === false ? "failure" : "success" ) );
 348         }
 349 }