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 /**
  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 = array( 'serializer' => 'none' ); // manage that in this class
  69                 foreach ( array( '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
  88         public function get( $key, &$casToken = null, $flags = 0 ) {
  89                 list( $server, $conn ) = $this->getConnection( $key );
  90                 if ( !$conn ) {
  91                         return false;
  92                 }
  93                 try {
  94                         $value = $conn->get( $key );
  95                         $casToken = $value;
  96                         $result = $this->unserialize( $value );
  97                 } catch ( RedisException $e ) {
  98                         $result = false;
  99                         $this->handleException( $conn, $e );
 100                 }
 101
 102                 $this->logRequest( 'get', $key, $server, $result );
 103                 return $result;
 104         }
 105
 106         public function set( $key, $value, $expiry = 0 ) {
 107                 list( $server, $conn ) = $this->getConnection( $key );
 108                 if ( !$conn ) {
 109                         return false;
 110                 }
 111                 $expiry = $this->convertToRelative( $expiry );
 112                 try {
 113                         if ( $expiry ) {
 114                                 $result = $conn->setex( $key, $expiry, $this->serialize( $value ) );
 115                         } else {
 116                                 // No expiry, that is very different from zero expiry in Redis
 117                                 $result = $conn->set( $key, $this->serialize( $value ) );
 118                         }
 119                 } catch ( RedisException $e ) {
 120                         $result = false;
 121                         $this->handleException( $conn, $e );
 122                 }
 123
 124                 $this->logRequest( 'set', $key, $server, $result );
 125                 return $result;
 126         }
 127
 128         public function delete( $key ) {
 129                 list( $server, $conn ) = $this->getConnection( $key );
 130                 if ( !$conn ) {
 131                         return false;
 132                 }
 133                 try {
 134                         $conn->delete( $key );
 135                         // Return true even if the key didn't exist
 136                         $result = true;
 137                 } catch ( RedisException $e ) {
 138                         $result = false;
 139                         $this->handleException( $conn, $e );
 140                 }
 141
 142                 $this->logRequest( 'delete', $key, $server, $result );
 143                 return $result;
 144         }
 145
 146         public function getMulti( array $keys, $flags = 0 ) {
 147                 $batches = array();
 148                 $conns = array();
 149                 foreach ( $keys as $key ) {
 150                         list( $server, $conn ) = $this->getConnection( $key );
 151                         if ( !$conn ) {
 152                                 continue;
 153                         }
 154                         $conns[$server] = $conn;
 155                         $batches[$server][] = $key;
 156                 }
 157                 $result = array();
 158                 foreach ( $batches as $server => $batchKeys ) {
 159                         $conn = $conns[$server];
 160                         try {
 161                                 $conn->multi( Redis::PIPELINE );
 162                                 foreach ( $batchKeys as $key ) {
 163                                         $conn->get( $key );
 164                                 }
 165                                 $batchResult = $conn->exec();
 166                                 if ( $batchResult === false ) {
 167                                         $this->debug( "multi request to $server failed" );
 168                                         continue;
 169                                 }
 170                                 foreach ( $batchResult as $i => $value ) {
 171                                         if ( $value !== false ) {
 172                                                 $result[$batchKeys[$i]] = $this->unserialize( $value );
 173                                         }
 174                                 }
 175                         } catch ( RedisException $e ) {
 176                                 $this->handleException( $conn, $e );
 177                         }
 178                 }
 179
 180                 $this->debug( "getMulti for " . count( $keys ) . " keys " .
 181                         "returned " . count( $result ) . " results" );
 182                 return $result;
 183         }
 184
 185         /**
 186          * @param array $data
 187          * @param int $expiry
 188          * @return bool
 189          */
 190         public function setMulti( array $data, $expiry = 0 ) {
 191                 $batches = array();
 192                 $conns = array();
 193                 foreach ( $data as $key => $value ) {
 194                         list( $server, $conn ) = $this->getConnection( $key );
 195                         if ( !$conn ) {
 196                                 continue;
 197                         }
 198                         $conns[$server] = $conn;
 199                         $batches[$server][] = $key;
 200                 }
 201
 202                 $expiry = $this->convertToRelative( $expiry );
 203                 $result = true;
 204                 foreach ( $batches as $server => $batchKeys ) {
 205                         $conn = $conns[$server];
 206                         try {
 207                                 $conn->multi( Redis::PIPELINE );
 208                                 foreach ( $batchKeys as $key ) {
 209                                         if ( $expiry ) {
 210                                                 $conn->setex( $key, $expiry, $this->serialize( $data[$key] ) );
 211                                         } else {
 212                                                 $conn->set( $key, $this->serialize( $data[$key] ) );
 213                                         }
 214                                 }
 215                                 $batchResult = $conn->exec();
 216                                 if ( $batchResult === false ) {
 217                                         $this->debug( "setMulti request to $server failed" );
 218                                         continue;
 219                                 }
 220                                 foreach ( $batchResult as $value ) {
 221                                         if ( $value === false ) {
 222                                                 $result = false;
 223                                         }
 224                                 }
 225                         } catch ( RedisException $e ) {
 226                                 $this->handleException( $server, $conn, $e );
 227                                 $result = false;
 228                         }
 229                 }
 230
 231                 return $result;
 232         }
 233
 234         public function add( $key, $value, $expiry = 0 ) {
 235                 list( $server, $conn ) = $this->getConnection( $key );
 236                 if ( !$conn ) {
 237                         return false;
 238                 }
 239                 $expiry = $this->convertToRelative( $expiry );
 240                 try {
 241                         if ( $expiry ) {
 242                                 $result = $conn->set(
 243                                         $key,
 244                                         $this->serialize( $value ),
 245                                         array( 'nx', 'ex' => $expiry )
 246                                 );
 247                         } else {
 248                                 $result = $conn->setnx( $key, $this->serialize( $value ) );
 249                         }
 250                 } catch ( RedisException $e ) {
 251                         $result = false;
 252                         $this->handleException( $conn, $e );
 253                 }
 254
 255                 $this->logRequest( 'add', $key, $server, $result );
 256                 return $result;
 257         }
 258
 259         /**
 260          * Non-atomic implementation of incr().
 261          *
 262          * Probably all callers actually want incr() to atomically initialise
 263          * values to zero if they don't exist, as provided by the Redis INCR
 264          * command. But we are constrained by the memcached-like interface to
 265          * return null in that case. Once the key exists, further increments are
 266          * atomic.
 267          * @param string $key Key to increase
 268          * @param int $value Value to add to $key (Default 1)
 269          * @return int|bool New value or false on failure
 270          */
 271         public function incr( $key, $value = 1 ) {
 272                 list( $server, $conn ) = $this->getConnection( $key );
 273                 if ( !$conn ) {
 274                         return false;
 275                 }
 276                 if ( !$conn->exists( $key ) ) {
 277                         return null;
 278                 }
 279                 try {
 280                         // @FIXME: on races, the key may have a 0 TTL
 281                         $result = $conn->incrBy( $key, $value );
 282                 } catch ( RedisException $e ) {
 283                         $result = false;
 284                         $this->handleException( $conn, $e );
 285                 }
 286
 287                 $this->logRequest( 'incr', $key, $server, $result );
 288                 return $result;
 289         }
 290
 291         public function modifySimpleRelayEvent( array $event ) {
 292                 if ( array_key_exists( 'val', $event ) ) {
 293                         $event['val'] = serialize( $event['val'] ); // this class uses PHP serialization
 294                 }
 295
 296                 return $event;
 297         }
 298
 299         /**
 300          * @param mixed $data
 301          * @return string
 302          */
 303         protected function serialize( $data ) {
 304                 // Serialize anything but integers so INCR/DECR work
 305                 // Do not store integer-like strings as integers to avoid type confusion (bug 60563)
 306                 return is_int( $data ) ? $data : serialize( $data );
 307         }
 308
 309         /**
 310          * @param string $data
 311          * @return mixed
 312          */
 313         protected function unserialize( $data ) {
 314                 return ctype_digit( $data ) ? intval( $data ) : unserialize( $data );
 315         }
 316
 317         /**
 318          * Get a Redis object with a connection suitable for fetching the specified key
 319          * @param string $key
 320          * @return array (server, RedisConnRef) or (false, false)
 321          */
 322         protected function getConnection( $key ) {
 323                 $candidates = array_keys( $this->serverTagMap );
 324
 325                 if ( count( $this->servers ) > 1 ) {
 326                         ArrayUtils::consistentHashSort( $candidates, $key, '/' );
 327                         if ( !$this->automaticFailover ) {
 328                                 $candidates = array_slice( $candidates, 0, 1 );
 329                         }
 330                 }
 331
 332                 while ( ( $tag = array_shift( $candidates ) ) !== null ) {
 333                         $server = $this->serverTagMap[$tag];
 334                         $conn = $this->redisPool->getConnection( $server );
 335                         if ( !$conn ) {
 336                                 continue;
 337                         }
 338
 339                         // If automatic failover is enabled, check that the server's link
 340                         // to its master (if any) is up -- but only if there are other
 341                         // viable candidates left to consider. Also, getMasterLinkStatus()
 342                         // does not work with twemproxy, though $candidates will be empty
 343                         // by now in such cases.
 344                         if ( $this->automaticFailover && $candidates ) {
 345                                 try {
 346                                         if ( $this->getMasterLinkStatus( $conn ) === 'down' ) {
 347                                                 // If the master cannot be reached, fail-over to the next server.
 348                                                 // If masters are in data-center A, and slaves in data-center B,
 349                                                 // this helps avoid the case were fail-over happens in A but not
 350                                                 // to the corresponding server in B (e.g. read/write mismatch).
 351                                                 continue;
 352                                         }
 353                                 } catch ( RedisException $e ) {
 354                                         // Server is not accepting commands
 355                                         $this->handleException( $conn, $e );
 356                                         continue;
 357                                 }
 358                         }
 359
 360                         return array( $server, $conn );
 361                 }
 362
 363                 $this->setLastError( BagOStuff::ERR_UNREACHABLE );
 364
 365                 return array( false, false );
 366         }
 367
 368         /**
 369          * Check the master link status of a Redis server that is configured as a slave.
 370          * @param RedisConnRef $conn
 371          * @return string|null Master link status (either 'up' or 'down'), or null
 372          *  if the server is not a slave.
 373          */
 374         protected function getMasterLinkStatus( RedisConnRef $conn ) {
 375                 $info = $conn->info();
 376                 return isset( $info['master_link_status'] )
 377                         ? $info['master_link_status']
 378                         : null;
 379         }
 380
 381         /**
 382          * Log a fatal error
 383          * @param string $msg
 384          */
 385         protected function logError( $msg ) {
 386                 $this->logger->error( "Redis error: $msg" );
 387         }
 388
 389         /**
 390          * The redis extension throws an exception in response to various read, write
 391          * and protocol errors. Sometimes it also closes the connection, sometimes
 392          * not. The safest response for us is to explicitly destroy the connection
 393          * object and let it be reopened during the next request.
 394          * @param RedisConnRef $conn
 395          * @param Exception $e
 396          */
 397         protected function handleException( RedisConnRef $conn, $e ) {
 398                 $this->setLastError( BagOStuff::ERR_UNEXPECTED );
 399                 $this->redisPool->handleError( $conn, $e );
 400         }
 401
 402         /**
 403          * Send information about a single request to the debug log
 404          * @param string $method
 405          * @param string $key
 406          * @param string $server
 407          * @param bool $result
 408          */
 409         public function logRequest( $method, $key, $server, $result ) {
 410                 $this->debug( "$method $key on $server: " .
 411                         ( $result === false ? "failure" : "success" ) );
 412         }
 413 }