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 = [ '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
  88         protected function doGet( $key, $flags = 0 ) {
  89                 list( $server, $conn ) = $this->getConnection( $key );
  90                 if ( !$conn ) {
  91                         return false;
  92                 }
  93                 try {
  94                         $value = $conn->get( $key );
  95                         $result = $this->unserialize( $value );
  96                 } catch ( RedisException $e ) {
  97                         $result = false;
  98                         $this->handleException( $conn, $e );
  99                 }
 100
 101                 $this->logRequest( 'get', $key, $server, $result );
 102                 return $result;
 103         }
 104
 105         public function set( $key, $value, $expiry = 0, $flags = 0 ) {
 106                 list( $server, $conn ) = $this->getConnection( $key );
 107                 if ( !$conn ) {
 108                         return false;
 109                 }
 110                 $expiry = $this->convertToRelative( $expiry );
 111                 try {
 112                         if ( $expiry ) {
 113                                 $result = $conn->setex( $key, $expiry, $this->serialize( $value ) );
 114                         } else {
 115                                 // No expiry, that is very different from zero expiry in Redis
 116                                 $result = $conn->set( $key, $this->serialize( $value ) );
 117                         }
 118                 } catch ( RedisException $e ) {
 119                         $result = false;
 120                         $this->handleException( $conn, $e );
 121                 }
 122
 123                 $this->logRequest( 'set', $key, $server, $result );
 124                 return $result;
 125         }
 126
 127         public function delete( $key ) {
 128                 list( $server, $conn ) = $this->getConnection( $key );
 129                 if ( !$conn ) {
 130                         return false;
 131                 }
 132                 try {
 133                         $conn->delete( $key );
 134                         // Return true even if the key didn't exist
 135                         $result = true;
 136                 } catch ( RedisException $e ) {
 137                         $result = false;
 138                         $this->handleException( $conn, $e );
 139                 }
 140
 141                 $this->logRequest( 'delete', $key, $server, $result );
 142                 return $result;
 143         }
 144
 145         public function getMulti( array $keys, $flags = 0 ) {
 146                 $batches = [];
 147                 $conns = [];
 148                 foreach ( $keys as $key ) {
 149                         list( $server, $conn ) = $this->getConnection( $key );
 150                         if ( !$conn ) {
 151                                 continue;
 152                         }
 153                         $conns[$server] = $conn;
 154                         $batches[$server][] = $key;
 155                 }
 156                 $result = [];
 157                 foreach ( $batches as $server => $batchKeys ) {
 158                         $conn = $conns[$server];
 159                         try {
 160                                 $conn->multi( Redis::PIPELINE );
 161                                 foreach ( $batchKeys as $key ) {
 162                                         $conn->get( $key );
 163                                 }
 164                                 $batchResult = $conn->exec();
 165                                 if ( $batchResult === false ) {
 166                                         $this->debug( "multi request to $server failed" );
 167                                         continue;
 168                                 }
 169                                 foreach ( $batchResult as $i => $value ) {
 170                                         if ( $value !== false ) {
 171                                                 $result[$batchKeys[$i]] = $this->unserialize( $value );
 172                                         }
 173                                 }
 174                         } catch ( RedisException $e ) {
 175                                 $this->handleException( $conn, $e );
 176                         }
 177                 }
 178
 179                 $this->debug( "getMulti for " . count( $keys ) . " keys " .
 180                         "returned " . count( $result ) . " results" );
 181                 return $result;
 182         }
 183
 184         /**
 185          * @param array $data
 186          * @param int $expiry
 187          * @return bool
 188          */
 189         public function setMulti( array $data, $expiry = 0 ) {
 190                 $batches = [];
 191                 $conns = [];
 192                 foreach ( $data as $key => $value ) {
 193                         list( $server, $conn ) = $this->getConnection( $key );
 194                         if ( !$conn ) {
 195                                 continue;
 196                         }
 197                         $conns[$server] = $conn;
 198                         $batches[$server][] = $key;
 199                 }
 200
 201                 $expiry = $this->convertToRelative( $expiry );
 202                 $result = true;
 203                 foreach ( $batches as $server => $batchKeys ) {
 204                         $conn = $conns[$server];
 205                         try {
 206                                 $conn->multi( Redis::PIPELINE );
 207                                 foreach ( $batchKeys as $key ) {
 208                                         if ( $expiry ) {
 209                                                 $conn->setex( $key, $expiry, $this->serialize( $data[$key] ) );
 210                                         } else {
 211                                                 $conn->set( $key, $this->serialize( $data[$key] ) );
 212                                         }
 213                                 }
 214                                 $batchResult = $conn->exec();
 215                                 if ( $batchResult === false ) {
 216                                         $this->debug( "setMulti request to $server failed" );
 217                                         continue;
 218                                 }
 219                                 foreach ( $batchResult as $value ) {
 220                                         if ( $value === false ) {
 221                                                 $result = false;
 222                                         }
 223                                 }
 224                         } catch ( RedisException $e ) {
 225                                 $this->handleException( $server, $conn, $e );
 226                                 $result = false;
 227                         }
 228                 }
 229
 230                 return $result;
 231         }
 232
 233         public function add( $key, $value, $expiry = 0 ) {
 234                 list( $server, $conn ) = $this->getConnection( $key );
 235                 if ( !$conn ) {
 236                         return false;
 237                 }
 238                 $expiry = $this->convertToRelative( $expiry );
 239                 try {
 240                         if ( $expiry ) {
 241                                 $result = $conn->set(
 242                                         $key,
 243                                         $this->serialize( $value ),
 244                                         [ 'nx', 'ex' => $expiry ]
 245                                 );
 246                         } else {
 247                                 $result = $conn->setnx( $key, $this->serialize( $value ) );
 248                         }
 249                 } catch ( RedisException $e ) {
 250                         $result = false;
 251                         $this->handleException( $conn, $e );
 252                 }
 253
 254                 $this->logRequest( 'add', $key, $server, $result );
 255                 return $result;
 256         }
 257
 258         /**
 259          * Non-atomic implementation of incr().
 260          *
 261          * Probably all callers actually want incr() to atomically initialise
 262          * values to zero if they don't exist, as provided by the Redis INCR
 263          * command. But we are constrained by the memcached-like interface to
 264          * return null in that case. Once the key exists, further increments are
 265          * atomic.
 266          * @param string $key Key to increase
 267          * @param int $value Value to add to $key (Default 1)
 268          * @return int|bool New value or false on failure
 269          */
 270         public function incr( $key, $value = 1 ) {
 271                 list( $server, $conn ) = $this->getConnection( $key );
 272                 if ( !$conn ) {
 273                         return false;
 274                 }
 275                 if ( !$conn->exists( $key ) ) {
 276                         return null;
 277                 }
 278                 try {
 279                         // @FIXME: on races, the key may have a 0 TTL
 280                         $result = $conn->incrBy( $key, $value );
 281                 } catch ( RedisException $e ) {
 282                         $result = false;
 283                         $this->handleException( $conn, $e );
 284                 }
 285
 286                 $this->logRequest( 'incr', $key, $server, $result );
 287                 return $result;
 288         }
 289
 290         public function modifySimpleRelayEvent( array $event ) {
 291                 if ( array_key_exists( 'val', $event ) ) {
 292                         $event['val'] = serialize( $event['val'] ); // this class uses PHP serialization
 293                 }
 294
 295                 return $event;
 296         }
 297
 298         /**
 299          * @param mixed $data
 300          * @return string
 301          */
 302         protected function serialize( $data ) {
 303                 // Serialize anything but integers so INCR/DECR work
 304                 // Do not store integer-like strings as integers to avoid type confusion (bug 60563)
 305                 return is_int( $data ) ? $data : serialize( $data );
 306         }
 307
 308         /**
 309          * @param string $data
 310          * @return mixed
 311          */
 312         protected function unserialize( $data ) {
 313                 $int = intval( $data );
 314                 return $data === (string)$int ? $int : 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 [ $server, $conn ];
 361                 }
 362
 363                 $this->setLastError( BagOStuff::ERR_UNREACHABLE );
 364
 365                 return [ 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 }