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 class RedisBagOStuff extends BagOStuff {
  29         /** @var RedisConnectionPool */
  30         protected $redisPool;
  31         /** @var array List of server names */
  32         protected $servers;
  33         /** @var array Map of (tag => server name) */
  34         protected $serverTagMap;
  35         /** @var bool */
  36         protected $automaticFailover;
  37
  38         /**
  39          * Construct a RedisBagOStuff object. Parameters are:
  40          *
  41          *   - servers: An array of server names. A server name may be a hostname,
  42          *     a hostname/port combination or the absolute path of a UNIX socket.
  43          *     If a hostname is specified but no port, the standard port number
  44          *     6379 will be used. Arrays keys can be used to specify the tag to
  45          *     hash on in place of the host/port. Required.
  46          *
  47          *   - connectTimeout: The timeout for new connections, in seconds. Optional,
  48          *     default is 1 second.
  49          *
  50          *   - persistent: Set this to true to allow connections to persist across
  51          *     multiple web requests. False by default.
  52          *
  53          *   - password: The authentication password, will be sent to Redis in
  54          *     clear text. Optional, if it is unspecified, no AUTH command will be
  55          *     sent.
  56          *
  57          *   - automaticFailover: If this is false, then each key will be mapped to
  58          *     a single server, and if that server is down, any requests for that key
  59          *     will fail. If this is true, a connection failure will cause the client
  60          *     to immediately try the next server in the list (as determined by a
  61          *     consistent hashing algorithm). True by default. This has the
  62          *     potential to create consistency issues if a server is slow enough to
  63          *     flap, for example if it is in swap death.
  64          * @param array $params
  65          */
  66         function __construct( $params ) {
  67                 parent::__construct( $params );
  68                 $redisConf = [ 'serializer' => 'none' ]; // manage that in this class
  69                 foreach ( [ 'connectTimeout', 'persistent', 'password' ] as $opt ) {
  70                         if ( isset( $params[$opt] ) ) {
  71                                 $redisConf[$opt] = $params[$opt];
  72                         }
  73                 }
  74                 $this->redisPool = RedisConnectionPool::singleton( $redisConf );
  75
  76                 $this->servers = $params['servers'];
  77                 foreach ( $this->servers as $key => $server ) {
  78                         $this->serverTagMap[is_int( $key ) ? $server : $key] = $server;
  79                 }
  80
  81                 if ( isset( $params['automaticFailover'] ) ) {
  82                         $this->automaticFailover = $params['automaticFailover'];
  83                 } else {
  84                         $this->automaticFailover = true;
  85                 }
  86
  87                 $this->attrMap[self::ATTR_SYNCWRITES] = self::QOS_SYNCWRITES_NONE;
  88         }
  89
  90         protected function doGet( $key, $flags = 0 ) {
  91                 list( $server, $conn ) = $this->getConnection( $key );
  92                 if ( !$conn ) {
  93                         return false;
  94                 }
  95                 try {
  96                         $value = $conn->get( $key );
  97                         $result = $this->unserialize( $value );
  98                 } catch ( RedisException $e ) {
  99                         $result = false;
 100                         $this->handleException( $conn, $e );
 101                 }
 102
 103                 $this->logRequest( 'get', $key, $server, $result );
 104                 return $result;
 105         }
 106
 107         public function set( $key, $value, $expiry = 0, $flags = 0 ) {
 108                 list( $server, $conn ) = $this->getConnection( $key );
 109                 if ( !$conn ) {
 110                         return false;
 111                 }
 112                 $expiry = $this->convertToRelative( $expiry );
 113                 try {
 114                         if ( $expiry ) {
 115                                 $result = $conn->setex( $key, $expiry, $this->serialize( $value ) );
 116                         } else {
 117                                 // No expiry, that is very different from zero expiry in Redis
 118                                 $result = $conn->set( $key, $this->serialize( $value ) );
 119                         }
 120                 } catch ( RedisException $e ) {
 121                         $result = false;
 122                         $this->handleException( $conn, $e );
 123                 }
 124
 125                 $this->logRequest( 'set', $key, $server, $result );
 126                 return $result;
 127         }
 128
 129         public function delete( $key ) {
 130                 list( $server, $conn ) = $this->getConnection( $key );
 131                 if ( !$conn ) {
 132                         return false;
 133                 }
 134                 try {
 135                         $conn->delete( $key );
 136                         // Return true even if the key didn't exist
 137                         $result = true;
 138                 } catch ( RedisException $e ) {
 139                         $result = false;
 140                         $this->handleException( $conn, $e );
 141                 }
 142
 143                 $this->logRequest( 'delete', $key, $server, $result );
 144                 return $result;
 145         }
 146
 147         public function getMulti( array $keys, $flags = 0 ) {
 148                 $batches = [];
 149                 $conns = [];
 150                 foreach ( $keys as $key ) {
 151                         list( $server, $conn ) = $this->getConnection( $key );
 152                         if ( !$conn ) {
 153                                 continue;
 154                         }
 155                         $conns[$server] = $conn;
 156                         $batches[$server][] = $key;
 157                 }
 158                 $result = [];
 159                 foreach ( $batches as $server => $batchKeys ) {
 160                         $conn = $conns[$server];
 161                         try {
 162                                 $conn->multi( Redis::PIPELINE );
 163                                 foreach ( $batchKeys as $key ) {
 164                                         $conn->get( $key );
 165                                 }
 166                                 $batchResult = $conn->exec();
 167                                 if ( $batchResult === false ) {
 168                                         $this->debug( "multi request to $server failed" );
 169                                         continue;
 170                                 }
 171                                 foreach ( $batchResult as $i => $value ) {
 172                                         if ( $value !== false ) {
 173                                                 $result[$batchKeys[$i]] = $this->unserialize( $value );
 174                                         }
 175                                 }
 176                         } catch ( RedisException $e ) {
 177                                 $this->handleException( $conn, $e );
 178                         }
 179                 }
 180
 181                 $this->debug( "getMulti for " . count( $keys ) . " keys " .
 182                         "returned " . count( $result ) . " results" );
 183                 return $result;
 184         }
 185
 186         /**
 187          * @param array $data
 188          * @param int $expiry
 189          * @return bool
 190          */
 191         public function setMulti( array $data, $expiry = 0 ) {
 192                 $batches = [];
 193                 $conns = [];
 194                 foreach ( $data as $key => $value ) {
 195                         list( $server, $conn ) = $this->getConnection( $key );
 196                         if ( !$conn ) {
 197                                 continue;
 198                         }
 199                         $conns[$server] = $conn;
 200                         $batches[$server][] = $key;
 201                 }
 202
 203                 $expiry = $this->convertToRelative( $expiry );
 204                 $result = true;
 205                 foreach ( $batches as $server => $batchKeys ) {
 206                         $conn = $conns[$server];
 207                         try {
 208                                 $conn->multi( Redis::PIPELINE );
 209                                 foreach ( $batchKeys as $key ) {
 210                                         if ( $expiry ) {
 211                                                 $conn->setex( $key, $expiry, $this->serialize( $data[$key] ) );
 212                                         } else {
 213                                                 $conn->set( $key, $this->serialize( $data[$key] ) );
 214                                         }
 215                                 }
 216                                 $batchResult = $conn->exec();
 217                                 if ( $batchResult === false ) {
 218                                         $this->debug( "setMulti request to $server failed" );
 219                                         continue;
 220                                 }
 221                                 foreach ( $batchResult as $value ) {
 222                                         if ( $value === false ) {
 223                                                 $result = false;
 224                                         }
 225                                 }
 226                         } catch ( RedisException $e ) {
 227                                 $this->handleException( $server, $conn, $e );
 228                                 $result = false;
 229                         }
 230                 }
 231
 232                 return $result;
 233         }
 234
 235         public function add( $key, $value, $expiry = 0 ) {
 236                 list( $server, $conn ) = $this->getConnection( $key );
 237                 if ( !$conn ) {
 238                         return false;
 239                 }
 240                 $expiry = $this->convertToRelative( $expiry );
 241                 try {
 242                         if ( $expiry ) {
 243                                 $result = $conn->set(
 244                                         $key,
 245                                         $this->serialize( $value ),
 246                                         [ 'nx', 'ex' => $expiry ]
 247                                 );
 248                         } else {
 249                                 $result = $conn->setnx( $key, $this->serialize( $value ) );
 250                         }
 251                 } catch ( RedisException $e ) {
 252                         $result = false;
 253                         $this->handleException( $conn, $e );
 254                 }
 255
 256                 $this->logRequest( 'add', $key, $server, $result );
 257                 return $result;
 258         }
 259
 260         /**
 261          * Non-atomic implementation of incr().
 262          *
 263          * Probably all callers actually want incr() to atomically initialise
 264          * values to zero if they don't exist, as provided by the Redis INCR
 265          * command. But we are constrained by the memcached-like interface to
 266          * return null in that case. Once the key exists, further increments are
 267          * atomic.
 268          * @param string $key Key to increase
 269          * @param int $value Value to add to $key (Default 1)
 270          * @return int|bool New value or false on failure
 271          */
 272         public function incr( $key, $value = 1 ) {
 273                 list( $server, $conn ) = $this->getConnection( $key );
 274                 if ( !$conn ) {
 275                         return false;
 276                 }
 277                 try {
 278                         if ( !$conn->exists( $key ) ) {
 279                                 return null;
 280                         }
 281                         // @FIXME: on races, the key may have a 0 TTL
 282                         $result = $conn->incrBy( $key, $value );
 283                 } catch ( RedisException $e ) {
 284                         $result = false;
 285                         $this->handleException( $conn, $e );
 286                 }
 287
 288                 $this->logRequest( 'incr', $key, $server, $result );
 289                 return $result;
 290         }
 291
 292         public function changeTTL( $key, $expiry = 0 ) {
 293                 list( $server, $conn ) = $this->getConnection( $key );
 294                 if ( !$conn ) {
 295                         return false;
 296                 }
 297
 298                 $expiry = $this->convertToRelative( $expiry );
 299                 try {
 300                         $result = $conn->expire( $key, $expiry );
 301                 } catch ( RedisException $e ) {
 302                         $result = false;
 303                         $this->handleException( $conn, $e );
 304                 }
 305
 306                 $this->logRequest( 'expire', $key, $server, $result );
 307                 return $result;
 308         }
 309
 310         public function modifySimpleRelayEvent( array $event ) {
 311                 if ( array_key_exists( 'val', $event ) ) {
 312                         $event['val'] = serialize( $event['val'] ); // this class uses PHP serialization
 313                 }
 314
 315                 return $event;
 316         }
 317
 318         /**
 319          * @param mixed $data
 320          * @return string
 321          */
 322         protected function serialize( $data ) {
 323                 // Serialize anything but integers so INCR/DECR work
 324                 // Do not store integer-like strings as integers to avoid type confusion (bug 60563)
 325                 return is_int( $data ) ? $data : serialize( $data );
 326         }
 327
 328         /**
 329          * @param string $data
 330          * @return mixed
 331          */
 332         protected function unserialize( $data ) {
 333                 $int = intval( $data );
 334                 return $data === (string)$int ? $int : unserialize( $data );
 335         }
 336
 337         /**
 338          * Get a Redis object with a connection suitable for fetching the specified key
 339          * @param string $key
 340          * @return array (server, RedisConnRef) or (false, false)
 341          */
 342         protected function getConnection( $key ) {
 343                 $candidates = array_keys( $this->serverTagMap );
 344
 345                 if ( count( $this->servers ) > 1 ) {
 346                         ArrayUtils::consistentHashSort( $candidates, $key, '/' );
 347                         if ( !$this->automaticFailover ) {
 348                                 $candidates = array_slice( $candidates, 0, 1 );
 349                         }
 350                 }
 351
 352                 while ( ( $tag = array_shift( $candidates ) ) !== null ) {
 353                         $server = $this->serverTagMap[$tag];
 354                         $conn = $this->redisPool->getConnection( $server, $this->logger );
 355                         if ( !$conn ) {
 356                                 continue;
 357                         }
 358
 359                         // If automatic failover is enabled, check that the server's link
 360                         // to its master (if any) is up -- but only if there are other
 361                         // viable candidates left to consider. Also, getMasterLinkStatus()
 362                         // does not work with twemproxy, though $candidates will be empty
 363                         // by now in such cases.
 364                         if ( $this->automaticFailover && $candidates ) {
 365                                 try {
 366                                         if ( $this->getMasterLinkStatus( $conn ) === 'down' ) {
 367                                                 // If the master cannot be reached, fail-over to the next server.
 368                                                 // If masters are in data-center A, and replica DBs in data-center B,
 369                                                 // this helps avoid the case were fail-over happens in A but not
 370                                                 // to the corresponding server in B (e.g. read/write mismatch).
 371                                                 continue;
 372                                         }
 373                                 } catch ( RedisException $e ) {
 374                                         // Server is not accepting commands
 375                                         $this->handleException( $conn, $e );
 376                                         continue;
 377                                 }
 378                         }
 379
 380                         return [ $server, $conn ];
 381                 }
 382
 383                 $this->setLastError( BagOStuff::ERR_UNREACHABLE );
 384
 385                 return [ false, false ];
 386         }
 387
 388         /**
 389          * Check the master link status of a Redis server that is configured as a replica DB.
 390          * @param RedisConnRef $conn
 391          * @return string|null Master link status (either 'up' or 'down'), or null
 392          *  if the server is not a replica DB.
 393          */
 394         protected function getMasterLinkStatus( RedisConnRef $conn ) {
 395                 $info = $conn->info();
 396                 return isset( $info['master_link_status'] )
 397                         ? $info['master_link_status']
 398                         : null;
 399         }
 400
 401         /**
 402          * Log a fatal error
 403          * @param string $msg
 404          */
 405         protected function logError( $msg ) {
 406                 $this->logger->error( "Redis error: $msg" );
 407         }
 408
 409         /**
 410          * The redis extension throws an exception in response to various read, write
 411          * and protocol errors. Sometimes it also closes the connection, sometimes
 412          * not. The safest response for us is to explicitly destroy the connection
 413          * object and let it be reopened during the next request.
 414          * @param RedisConnRef $conn
 415          * @param Exception $e
 416          */
 417         protected function handleException( RedisConnRef $conn, $e ) {
 418                 $this->setLastError( BagOStuff::ERR_UNEXPECTED );
 419                 $this->redisPool->handleError( $conn, $e );
 420         }
 421
 422         /**
 423          * Send information about a single request to the debug log
 424          * @param string $method
 425          * @param string $key
 426          * @param string $server
 427          * @param bool $result
 428          */
 429         public function logRequest( $method, $key, $server, $result ) {
 430                 $this->debug( "$method $key on $server: " .
 431                         ( $result === false ? "failure" : "success" ) );
 432         }
 433 }