includes/libs/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 /**
  24  * Redis-based caching module for redis server >= 2.6.12
  25  *
  26  * @note Avoid use of Redis::MULTI transactions for twemproxy support
  27  *
  28  * @ingroup Cache
  29  * @ingroup Redis
  30  */
  31 class RedisBagOStuff extends BagOStuff {
  32         /** @var RedisConnectionPool */
  33         protected $redisPool;
  34         /** @var array List of server names */
  35         protected $servers;
  36         /** @var array Map of (tag => server name) */
  37         protected $serverTagMap;
  38         /** @var bool */
  39         protected $automaticFailover;
  40
  41         /**
  42          * Construct a RedisBagOStuff object. Parameters are:
  43          *
  44          *   - servers: An array of server names. A server name may be a hostname,
  45          *     a hostname/port combination or the absolute path of a UNIX socket.
  46          *     If a hostname is specified but no port, the standard port number
  47          *     6379 will be used. Arrays keys can be used to specify the tag to
  48          *     hash on in place of the host/port. Required.
  49          *
  50          *   - connectTimeout: The timeout for new connections, in seconds. Optional,
  51          *     default is 1 second.
  52          *
  53          *   - persistent: Set this to true to allow connections to persist across
  54          *     multiple web requests. False by default.
  55          *
  56          *   - password: The authentication password, will be sent to Redis in
  57          *     clear text. Optional, if it is unspecified, no AUTH command will be
  58          *     sent.
  59          *
  60          *   - automaticFailover: If this is false, then each key will be mapped to
  61          *     a single server, and if that server is down, any requests for that key
  62          *     will fail. If this is true, a connection failure will cause the client
  63          *     to immediately try the next server in the list (as determined by a
  64          *     consistent hashing algorithm). True by default. This has the
  65          *     potential to create consistency issues if a server is slow enough to
  66          *     flap, for example if it is in swap death.
  67          * @param array $params
  68          */
  69         function __construct( $params ) {
  70                 parent::__construct( $params );
  71                 $redisConf = [ 'serializer' => 'none' ]; // manage that in this class
  72                 foreach ( [ 'connectTimeout', 'persistent', 'password' ] as $opt ) {
  73                         if ( isset( $params[$opt] ) ) {
  74                                 $redisConf[$opt] = $params[$opt];
  75                         }
  76                 }
  77                 $this->redisPool = RedisConnectionPool::singleton( $redisConf );
  78
  79                 $this->servers = $params['servers'];
  80                 foreach ( $this->servers as $key => $server ) {
  81                         $this->serverTagMap[is_int( $key ) ? $server : $key] = $server;
  82                 }
  83
  84                 if ( isset( $params['automaticFailover'] ) ) {
  85                         $this->automaticFailover = $params['automaticFailover'];
  86                 } else {
  87                         $this->automaticFailover = true;
  88                 }
  89
  90                 $this->attrMap[self::ATTR_SYNCWRITES] = self::QOS_SYNCWRITES_NONE;
  91         }
  92
  93         protected function doGet( $key, $flags = 0 ) {
  94                 list( $server, $conn ) = $this->getConnection( $key );
  95                 if ( !$conn ) {
  96                         return false;
  97                 }
  98                 try {
  99                         $value = $conn->get( $key );
 100                         $result = $this->unserialize( $value );
 101                 } catch ( RedisException $e ) {
 102                         $result = false;
 103                         $this->handleException( $conn, $e );
 104                 }
 105
 106                 $this->logRequest( 'get', $key, $server, $result );
 107                 return $result;
 108         }
 109
 110         public function set( $key, $value, $expiry = 0, $flags = 0 ) {
 111                 list( $server, $conn ) = $this->getConnection( $key );
 112                 if ( !$conn ) {
 113                         return false;
 114                 }
 115                 $expiry = $this->convertToRelative( $expiry );
 116                 try {
 117                         if ( $expiry ) {
 118                                 $result = $conn->setex( $key, $expiry, $this->serialize( $value ) );
 119                         } else {
 120                                 // No expiry, that is very different from zero expiry in Redis
 121                                 $result = $conn->set( $key, $this->serialize( $value ) );
 122                         }
 123                 } catch ( RedisException $e ) {
 124                         $result = false;
 125                         $this->handleException( $conn, $e );
 126                 }
 127
 128                 $this->logRequest( 'set', $key, $server, $result );
 129                 return $result;
 130         }
 131
 132         public function delete( $key ) {
 133                 list( $server, $conn ) = $this->getConnection( $key );
 134                 if ( !$conn ) {
 135                         return false;
 136                 }
 137                 try {
 138                         $conn->delete( $key );
 139                         // Return true even if the key didn't exist
 140                         $result = true;
 141                 } catch ( RedisException $e ) {
 142                         $result = false;
 143                         $this->handleException( $conn, $e );
 144                 }
 145
 146                 $this->logRequest( 'delete', $key, $server, $result );
 147                 return $result;
 148         }
 149
 150         public function getMulti( array $keys, $flags = 0 ) {
 151                 $batches = [];
 152                 $conns = [];
 153                 foreach ( $keys as $key ) {
 154                         list( $server, $conn ) = $this->getConnection( $key );
 155                         if ( !$conn ) {
 156                                 continue;
 157                         }
 158                         $conns[$server] = $conn;
 159                         $batches[$server][] = $key;
 160                 }
 161                 $result = [];
 162                 foreach ( $batches as $server => $batchKeys ) {
 163                         $conn = $conns[$server];
 164                         try {
 165                                 $conn->multi( Redis::PIPELINE );
 166                                 foreach ( $batchKeys as $key ) {
 167                                         $conn->get( $key );
 168                                 }
 169                                 $batchResult = $conn->exec();
 170                                 if ( $batchResult === false ) {
 171                                         $this->debug( "multi request to $server failed" );
 172                                         continue;
 173                                 }
 174                                 foreach ( $batchResult as $i => $value ) {
 175                                         if ( $value !== false ) {
 176                                                 $result[$batchKeys[$i]] = $this->unserialize( $value );
 177                                         }
 178                                 }
 179                         } catch ( RedisException $e ) {
 180                                 $this->handleException( $conn, $e );
 181                         }
 182                 }
 183
 184                 $this->debug( "getMulti for " . count( $keys ) . " keys " .
 185                         "returned " . count( $result ) . " results" );
 186                 return $result;
 187         }
 188
 189         /**
 190          * @param array $data
 191          * @param int $expiry
 192          * @return bool
 193          */
 194         public function setMulti( array $data, $expiry = 0 ) {
 195                 $batches = [];
 196                 $conns = [];
 197                 foreach ( $data as $key => $value ) {
 198                         list( $server, $conn ) = $this->getConnection( $key );
 199                         if ( !$conn ) {
 200                                 continue;
 201                         }
 202                         $conns[$server] = $conn;
 203                         $batches[$server][] = $key;
 204                 }
 205
 206                 $expiry = $this->convertToRelative( $expiry );
 207                 $result = true;
 208                 foreach ( $batches as $server => $batchKeys ) {
 209                         $conn = $conns[$server];
 210                         try {
 211                                 $conn->multi( Redis::PIPELINE );
 212                                 foreach ( $batchKeys as $key ) {
 213                                         if ( $expiry ) {
 214                                                 $conn->setex( $key, $expiry, $this->serialize( $data[$key] ) );
 215                                         } else {
 216                                                 $conn->set( $key, $this->serialize( $data[$key] ) );
 217                                         }
 218                                 }
 219                                 $batchResult = $conn->exec();
 220                                 if ( $batchResult === false ) {
 221                                         $this->debug( "setMulti request to $server failed" );
 222                                         continue;
 223                                 }
 224                                 foreach ( $batchResult as $value ) {
 225                                         if ( $value === false ) {
 226                                                 $result = false;
 227                                         }
 228                                 }
 229                         } catch ( RedisException $e ) {
 230                                 $this->handleException( $server, $conn, $e );
 231                                 $result = false;
 232                         }
 233                 }
 234
 235                 return $result;
 236         }
 237
 238         public function add( $key, $value, $expiry = 0 ) {
 239                 list( $server, $conn ) = $this->getConnection( $key );
 240                 if ( !$conn ) {
 241                         return false;
 242                 }
 243                 $expiry = $this->convertToRelative( $expiry );
 244                 try {
 245                         if ( $expiry ) {
 246                                 $result = $conn->set(
 247                                         $key,
 248                                         $this->serialize( $value ),
 249                                         [ 'nx', 'ex' => $expiry ]
 250                                 );
 251                         } else {
 252                                 $result = $conn->setnx( $key, $this->serialize( $value ) );
 253                         }
 254                 } catch ( RedisException $e ) {
 255                         $result = false;
 256                         $this->handleException( $conn, $e );
 257                 }
 258
 259                 $this->logRequest( 'add', $key, $server, $result );
 260                 return $result;
 261         }
 262
 263         /**
 264          * Non-atomic implementation of incr().
 265          *
 266          * Probably all callers actually want incr() to atomically initialise
 267          * values to zero if they don't exist, as provided by the Redis INCR
 268          * command. But we are constrained by the memcached-like interface to
 269          * return null in that case. Once the key exists, further increments are
 270          * atomic.
 271          * @param string $key Key to increase
 272          * @param int $value Value to add to $key (Default 1)
 273          * @return int|bool New value or false on failure
 274          */
 275         public function incr( $key, $value = 1 ) {
 276                 list( $server, $conn ) = $this->getConnection( $key );
 277                 if ( !$conn ) {
 278                         return false;
 279                 }
 280                 try {
 281                         if ( !$conn->exists( $key ) ) {
 282                                 return null;
 283                         }
 284                         // @FIXME: on races, the key may have a 0 TTL
 285                         $result = $conn->incrBy( $key, $value );
 286                 } catch ( RedisException $e ) {
 287                         $result = false;
 288                         $this->handleException( $conn, $e );
 289                 }
 290
 291                 $this->logRequest( 'incr', $key, $server, $result );
 292                 return $result;
 293         }
 294
 295         public function changeTTL( $key, $expiry = 0 ) {
 296                 list( $server, $conn ) = $this->getConnection( $key );
 297                 if ( !$conn ) {
 298                         return false;
 299                 }
 300
 301                 $expiry = $this->convertToRelative( $expiry );
 302                 try {
 303                         $result = $conn->expire( $key, $expiry );
 304                 } catch ( RedisException $e ) {
 305                         $result = false;
 306                         $this->handleException( $conn, $e );
 307                 }
 308
 309                 $this->logRequest( 'expire', $key, $server, $result );
 310                 return $result;
 311         }
 312
 313         public function modifySimpleRelayEvent( array $event ) {
 314                 if ( array_key_exists( 'val', $event ) ) {
 315                         $event['val'] = serialize( $event['val'] ); // this class uses PHP serialization
 316                 }
 317
 318                 return $event;
 319         }
 320
 321         /**
 322          * @param mixed $data
 323          * @return string
 324          */
 325         protected function serialize( $data ) {
 326                 // Serialize anything but integers so INCR/DECR work
 327                 // Do not store integer-like strings as integers to avoid type confusion (T62563)
 328                 return is_int( $data ) ? $data : serialize( $data );
 329         }
 330
 331         /**
 332          * @param string $data
 333          * @return mixed
 334          */
 335         protected function unserialize( $data ) {
 336                 $int = intval( $data );
 337                 return $data === (string)$int ? $int : unserialize( $data );
 338         }
 339
 340         /**
 341          * Get a Redis object with a connection suitable for fetching the specified key
 342          * @param string $key
 343          * @return array (server, RedisConnRef) or (false, false)
 344          */
 345         protected function getConnection( $key ) {
 346                 $candidates = array_keys( $this->serverTagMap );
 347
 348                 if ( count( $this->servers ) > 1 ) {
 349                         ArrayUtils::consistentHashSort( $candidates, $key, '/' );
 350                         if ( !$this->automaticFailover ) {
 351                                 $candidates = array_slice( $candidates, 0, 1 );
 352                         }
 353                 }
 354
 355                 while ( ( $tag = array_shift( $candidates ) ) !== null ) {
 356                         $server = $this->serverTagMap[$tag];
 357                         $conn = $this->redisPool->getConnection( $server, $this->logger );
 358                         if ( !$conn ) {
 359                                 continue;
 360                         }
 361
 362                         // If automatic failover is enabled, check that the server's link
 363                         // to its master (if any) is up -- but only if there are other
 364                         // viable candidates left to consider. Also, getMasterLinkStatus()
 365                         // does not work with twemproxy, though $candidates will be empty
 366                         // by now in such cases.
 367                         if ( $this->automaticFailover && $candidates ) {
 368                                 try {
 369                                         if ( $this->getMasterLinkStatus( $conn ) === 'down' ) {
 370                                                 // If the master cannot be reached, fail-over to the next server.
 371                                                 // If masters are in data-center A, and replica DBs in data-center B,
 372                                                 // this helps avoid the case were fail-over happens in A but not
 373                                                 // to the corresponding server in B (e.g. read/write mismatch).
 374                                                 continue;
 375                                         }
 376                                 } catch ( RedisException $e ) {
 377                                         // Server is not accepting commands
 378                                         $this->handleException( $conn, $e );
 379                                         continue;
 380                                 }
 381                         }
 382
 383                         return [ $server, $conn ];
 384                 }
 385
 386                 $this->setLastError( BagOStuff::ERR_UNREACHABLE );
 387
 388                 return [ false, false ];
 389         }
 390
 391         /**
 392          * Check the master link status of a Redis server that is configured as a replica DB.
 393          * @param RedisConnRef $conn
 394          * @return string|null Master link status (either 'up' or 'down'), or null
 395          *  if the server is not a replica DB.
 396          */
 397         protected function getMasterLinkStatus( RedisConnRef $conn ) {
 398                 $info = $conn->info();
 399                 return isset( $info['master_link_status'] )
 400                         ? $info['master_link_status']
 401                         : null;
 402         }
 403
 404         /**
 405          * Log a fatal error
 406          * @param string $msg
 407          */
 408         protected function logError( $msg ) {
 409                 $this->logger->error( "Redis error: $msg" );
 410         }
 411
 412         /**
 413          * The redis extension throws an exception in response to various read, write
 414          * and protocol errors. Sometimes it also closes the connection, sometimes
 415          * not. The safest response for us is to explicitly destroy the connection
 416          * object and let it be reopened during the next request.
 417          * @param RedisConnRef $conn
 418          * @param Exception $e
 419          */
 420         protected function handleException( RedisConnRef $conn, $e ) {
 421                 $this->setLastError( BagOStuff::ERR_UNEXPECTED );
 422                 $this->redisPool->handleError( $conn, $e );
 423         }
 424
 425         /**
 426          * Send information about a single request to the debug log
 427          * @param string $method
 428          * @param string $key
 429          * @param string $server
 430          * @param bool $result
 431          */
 432         public function logRequest( $method, $key, $server, $result ) {
 433                 $this->debug( "$method $key on $server: " .
 434                         ( $result === false ? "failure" : "success" ) );
 435         }
 436 }