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                 $this->automaticFailover = $params['automaticFailover'] ?? true;
  85
  86                 $this->attrMap[self::ATTR_SYNCWRITES] = self::QOS_SYNCWRITES_NONE;
  87         }
  88
  89         protected function doGet( $key, $flags = 0 ) {
  90                 $casToken = null;
  91
  92                 return $this->getWithToken( $key, $casToken, $flags );
  93         }
  94
  95         protected function getWithToken( $key, &$casToken, $flags = 0 ) {
  96                 list( $server, $conn ) = $this->getConnection( $key );
  97                 if ( !$conn ) {
  98                         return false;
  99                 }
 100                 try {
 101                         $value = $conn->get( $key );
 102                         $casToken = $value;
 103                         $result = $this->unserialize( $value );
 104                 } catch ( RedisException $e ) {
 105                         $result = false;
 106                         $this->handleException( $conn, $e );
 107                 }
 108
 109                 $this->logRequest( 'get', $key, $server, $result );
 110                 return $result;
 111         }
 112
 113         public function set( $key, $value, $expiry = 0, $flags = 0 ) {
 114                 list( $server, $conn ) = $this->getConnection( $key );
 115                 if ( !$conn ) {
 116                         return false;
 117                 }
 118                 $expiry = $this->convertToRelative( $expiry );
 119                 try {
 120                         if ( $expiry ) {
 121                                 $result = $conn->setex( $key, $expiry, $this->serialize( $value ) );
 122                         } else {
 123                                 // No expiry, that is very different from zero expiry in Redis
 124                                 $result = $conn->set( $key, $this->serialize( $value ) );
 125                         }
 126                 } catch ( RedisException $e ) {
 127                         $result = false;
 128                         $this->handleException( $conn, $e );
 129                 }
 130
 131                 $this->logRequest( 'set', $key, $server, $result );
 132                 return $result;
 133         }
 134
 135         public function delete( $key, $flags = 0 ) {
 136                 list( $server, $conn ) = $this->getConnection( $key );
 137                 if ( !$conn ) {
 138                         return false;
 139                 }
 140                 try {
 141                         $conn->delete( $key );
 142                         // Return true even if the key didn't exist
 143                         $result = true;
 144                 } catch ( RedisException $e ) {
 145                         $result = false;
 146                         $this->handleException( $conn, $e );
 147                 }
 148
 149                 $this->logRequest( 'delete', $key, $server, $result );
 150                 return $result;
 151         }
 152
 153         public function getMulti( array $keys, $flags = 0 ) {
 154                 $batches = [];
 155                 $conns = [];
 156                 foreach ( $keys as $key ) {
 157                         list( $server, $conn ) = $this->getConnection( $key );
 158                         if ( !$conn ) {
 159                                 continue;
 160                         }
 161                         $conns[$server] = $conn;
 162                         $batches[$server][] = $key;
 163                 }
 164                 $result = [];
 165                 foreach ( $batches as $server => $batchKeys ) {
 166                         $conn = $conns[$server];
 167                         try {
 168                                 $conn->multi( Redis::PIPELINE );
 169                                 foreach ( $batchKeys as $key ) {
 170                                         $conn->get( $key );
 171                                 }
 172                                 $batchResult = $conn->exec();
 173                                 if ( $batchResult === false ) {
 174                                         $this->debug( "multi request to $server failed" );
 175                                         continue;
 176                                 }
 177                                 foreach ( $batchResult as $i => $value ) {
 178                                         if ( $value !== false ) {
 179                                                 $result[$batchKeys[$i]] = $this->unserialize( $value );
 180                                         }
 181                                 }
 182                         } catch ( RedisException $e ) {
 183                                 $this->handleException( $conn, $e );
 184                         }
 185                 }
 186
 187                 $this->debug( "getMulti for " . count( $keys ) . " keys " .
 188                         "returned " . count( $result ) . " results" );
 189                 return $result;
 190         }
 191
 192         public function setMulti( array $data, $expiry = 0, $flags = 0 ) {
 193                 $batches = [];
 194                 $conns = [];
 195                 foreach ( $data as $key => $value ) {
 196                         list( $server, $conn ) = $this->getConnection( $key );
 197                         if ( !$conn ) {
 198                                 continue;
 199                         }
 200                         $conns[$server] = $conn;
 201                         $batches[$server][] = $key;
 202                 }
 203
 204                 $expiry = $this->convertToRelative( $expiry );
 205                 $result = true;
 206                 foreach ( $batches as $server => $batchKeys ) {
 207                         $conn = $conns[$server];
 208                         try {
 209                                 $conn->multi( Redis::PIPELINE );
 210                                 foreach ( $batchKeys as $key ) {
 211                                         if ( $expiry ) {
 212                                                 $conn->setex( $key, $expiry, $this->serialize( $data[$key] ) );
 213                                         } else {
 214                                                 $conn->set( $key, $this->serialize( $data[$key] ) );
 215                                         }
 216                                 }
 217                                 $batchResult = $conn->exec();
 218                                 if ( $batchResult === false ) {
 219                                         $this->debug( "setMulti request to $server failed" );
 220                                         continue;
 221                                 }
 222                                 foreach ( $batchResult as $value ) {
 223                                         if ( $value === false ) {
 224                                                 $result = false;
 225                                         }
 226                                 }
 227                         } catch ( RedisException $e ) {
 228                                 $this->handleException( $conn, $e );
 229                                 $result = false;
 230                         }
 231                 }
 232
 233                 return $result;
 234         }
 235
 236         public function add( $key, $value, $expiry = 0, $flags = 0 ) {
 237                 list( $server, $conn ) = $this->getConnection( $key );
 238                 if ( !$conn ) {
 239                         return false;
 240                 }
 241                 $expiry = $this->convertToRelative( $expiry );
 242                 try {
 243                         if ( $expiry ) {
 244                                 $result = $conn->set(
 245                                         $key,
 246                                         $this->serialize( $value ),
 247                                         [ 'nx', 'ex' => $expiry ]
 248                                 );
 249                         } else {
 250                                 $result = $conn->setnx( $key, $this->serialize( $value ) );
 251                         }
 252                 } catch ( RedisException $e ) {
 253                         $result = false;
 254                         $this->handleException( $conn, $e );
 255                 }
 256
 257                 $this->logRequest( 'add', $key, $server, $result );
 258                 return $result;
 259         }
 260
 261         public function merge( $key, callable $callback, $exptime = 0, $attempts = 10, $flags = 0 ) {
 262                 return $this->mergeViaCas( $key, $callback, $exptime, $attempts );
 263         }
 264
 265         /**
 266          * Non-atomic implementation of incr().
 267          *
 268          * Probably all callers actually want incr() to atomically initialise
 269          * values to zero if they don't exist, as provided by the Redis INCR
 270          * command. But we are constrained by the memcached-like interface to
 271          * return null in that case. Once the key exists, further increments are
 272          * atomic.
 273          * @param string $key Key to increase
 274          * @param int $value Value to add to $key (Default 1)
 275          * @return int|bool New value or false on failure
 276          */
 277         public function incr( $key, $value = 1 ) {
 278                 list( $server, $conn ) = $this->getConnection( $key );
 279                 if ( !$conn ) {
 280                         return false;
 281                 }
 282                 try {
 283                         if ( !$conn->exists( $key ) ) {
 284                                 return false;
 285                         }
 286                         // @FIXME: on races, the key may have a 0 TTL
 287                         $result = $conn->incrBy( $key, $value );
 288                 } catch ( RedisException $e ) {
 289                         $result = false;
 290                         $this->handleException( $conn, $e );
 291                 }
 292
 293                 $this->logRequest( 'incr', $key, $server, $result );
 294                 return $result;
 295         }
 296
 297         public function changeTTL( $key, $expiry = 0, $flags = 0 ) {
 298                 list( $server, $conn ) = $this->getConnection( $key );
 299                 if ( !$conn ) {
 300                         return false;
 301                 }
 302
 303                 $expiry = $this->convertToRelative( $expiry );
 304                 try {
 305                         $result = $conn->expire( $key, $expiry );
 306                 } catch ( RedisException $e ) {
 307                         $result = false;
 308                         $this->handleException( $conn, $e );
 309                 }
 310
 311                 $this->logRequest( 'expire', $key, $server, $result );
 312                 return $result;
 313         }
 314
 315         /**
 316          * @param mixed $data
 317          * @return string
 318          */
 319         protected function serialize( $data ) {
 320                 // Serialize anything but integers so INCR/DECR work
 321                 // Do not store integer-like strings as integers to avoid type confusion (T62563)
 322                 return is_int( $data ) ? $data : serialize( $data );
 323         }
 324
 325         /**
 326          * @param string $data
 327          * @return mixed
 328          */
 329         protected function unserialize( $data ) {
 330                 $int = intval( $data );
 331                 return $data === (string)$int ? $int : unserialize( $data );
 332         }
 333
 334         /**
 335          * Get a Redis object with a connection suitable for fetching the specified key
 336          * @param string $key
 337          * @return array (server, RedisConnRef) or (false, false)
 338          */
 339         protected function getConnection( $key ) {
 340                 $candidates = array_keys( $this->serverTagMap );
 341
 342                 if ( count( $this->servers ) > 1 ) {
 343                         ArrayUtils::consistentHashSort( $candidates, $key, '/' );
 344                         if ( !$this->automaticFailover ) {
 345                                 $candidates = array_slice( $candidates, 0, 1 );
 346                         }
 347                 }
 348
 349                 while ( ( $tag = array_shift( $candidates ) ) !== null ) {
 350                         $server = $this->serverTagMap[$tag];
 351                         $conn = $this->redisPool->getConnection( $server, $this->logger );
 352                         if ( !$conn ) {
 353                                 continue;
 354                         }
 355
 356                         // If automatic failover is enabled, check that the server's link
 357                         // to its master (if any) is up -- but only if there are other
 358                         // viable candidates left to consider. Also, getMasterLinkStatus()
 359                         // does not work with twemproxy, though $candidates will be empty
 360                         // by now in such cases.
 361                         if ( $this->automaticFailover && $candidates ) {
 362                                 try {
 363                                         if ( $this->getMasterLinkStatus( $conn ) === 'down' ) {
 364                                                 // If the master cannot be reached, fail-over to the next server.
 365                                                 // If masters are in data-center A, and replica DBs in data-center B,
 366                                                 // this helps avoid the case were fail-over happens in A but not
 367                                                 // to the corresponding server in B (e.g. read/write mismatch).
 368                                                 continue;
 369                                         }
 370                                 } catch ( RedisException $e ) {
 371                                         // Server is not accepting commands
 372                                         $this->handleException( $conn, $e );
 373                                         continue;
 374                                 }
 375                         }
 376
 377                         return [ $server, $conn ];
 378                 }
 379
 380                 $this->setLastError( BagOStuff::ERR_UNREACHABLE );
 381
 382                 return [ false, false ];
 383         }
 384
 385         /**
 386          * Check the master link status of a Redis server that is configured as a replica DB.
 387          * @param RedisConnRef $conn
 388          * @return string|null Master link status (either 'up' or 'down'), or null
 389          *  if the server is not a replica DB.
 390          */
 391         protected function getMasterLinkStatus( RedisConnRef $conn ) {
 392                 $info = $conn->info();
 393                 return $info['master_link_status'] ?? null;
 394         }
 395
 396         /**
 397          * Log a fatal error
 398          * @param string $msg
 399          */
 400         protected function logError( $msg ) {
 401                 $this->logger->error( "Redis error: $msg" );
 402         }
 403
 404         /**
 405          * The redis extension throws an exception in response to various read, write
 406          * and protocol errors. Sometimes it also closes the connection, sometimes
 407          * not. The safest response for us is to explicitly destroy the connection
 408          * object and let it be reopened during the next request.
 409          * @param RedisConnRef $conn
 410          * @param Exception $e
 411          */
 412         protected function handleException( RedisConnRef $conn, $e ) {
 413                 $this->setLastError( BagOStuff::ERR_UNEXPECTED );
 414                 $this->redisPool->handleError( $conn, $e );
 415         }
 416
 417         /**
 418          * Send information about a single request to the debug log
 419          * @param string $method
 420          * @param string $key
 421          * @param string $server
 422          * @param bool $result
 423          */
 424         public function logRequest( $method, $key, $server, $result ) {
 425                 $this->debug( "$method $key on $server: " .
 426                         ( $result === false ? "failure" : "success" ) );
 427         }
 428 }