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                 $casToken = null;
  95
  96                 return $this->getWithToken( $key, $casToken, $flags );
  97         }
  98
  99         protected function getWithToken( $key, &$casToken, $flags = 0 ) {
 100                 list( $server, $conn ) = $this->getConnection( $key );
 101                 if ( !$conn ) {
 102                         return false;
 103                 }
 104                 try {
 105                         $value = $conn->get( $key );
 106                         $casToken = $value;
 107                         $result = $this->unserialize( $value );
 108                 } catch ( RedisException $e ) {
 109                         $result = false;
 110                         $this->handleException( $conn, $e );
 111                 }
 112
 113                 $this->logRequest( 'get', $key, $server, $result );
 114                 return $result;
 115         }
 116
 117         public function set( $key, $value, $expiry = 0, $flags = 0 ) {
 118                 list( $server, $conn ) = $this->getConnection( $key );
 119                 if ( !$conn ) {
 120                         return false;
 121                 }
 122                 $expiry = $this->convertToRelative( $expiry );
 123                 try {
 124                         if ( $expiry ) {
 125                                 $result = $conn->setex( $key, $expiry, $this->serialize( $value ) );
 126                         } else {
 127                                 // No expiry, that is very different from zero expiry in Redis
 128                                 $result = $conn->set( $key, $this->serialize( $value ) );
 129                         }
 130                 } catch ( RedisException $e ) {
 131                         $result = false;
 132                         $this->handleException( $conn, $e );
 133                 }
 134
 135                 $this->logRequest( 'set', $key, $server, $result );
 136                 return $result;
 137         }
 138
 139         public function delete( $key ) {
 140                 list( $server, $conn ) = $this->getConnection( $key );
 141                 if ( !$conn ) {
 142                         return false;
 143                 }
 144                 try {
 145                         $conn->delete( $key );
 146                         // Return true even if the key didn't exist
 147                         $result = true;
 148                 } catch ( RedisException $e ) {
 149                         $result = false;
 150                         $this->handleException( $conn, $e );
 151                 }
 152
 153                 $this->logRequest( 'delete', $key, $server, $result );
 154                 return $result;
 155         }
 156
 157         public function getMulti( array $keys, $flags = 0 ) {
 158                 $batches = [];
 159                 $conns = [];
 160                 foreach ( $keys as $key ) {
 161                         list( $server, $conn ) = $this->getConnection( $key );
 162                         if ( !$conn ) {
 163                                 continue;
 164                         }
 165                         $conns[$server] = $conn;
 166                         $batches[$server][] = $key;
 167                 }
 168                 $result = [];
 169                 foreach ( $batches as $server => $batchKeys ) {
 170                         $conn = $conns[$server];
 171                         try {
 172                                 $conn->multi( Redis::PIPELINE );
 173                                 foreach ( $batchKeys as $key ) {
 174                                         $conn->get( $key );
 175                                 }
 176                                 $batchResult = $conn->exec();
 177                                 if ( $batchResult === false ) {
 178                                         $this->debug( "multi request to $server failed" );
 179                                         continue;
 180                                 }
 181                                 foreach ( $batchResult as $i => $value ) {
 182                                         if ( $value !== false ) {
 183                                                 $result[$batchKeys[$i]] = $this->unserialize( $value );
 184                                         }
 185                                 }
 186                         } catch ( RedisException $e ) {
 187                                 $this->handleException( $conn, $e );
 188                         }
 189                 }
 190
 191                 $this->debug( "getMulti for " . count( $keys ) . " keys " .
 192                         "returned " . count( $result ) . " results" );
 193                 return $result;
 194         }
 195
 196         /**
 197          * @param array $data
 198          * @param int $expiry
 199          * @return bool
 200          */
 201         public function setMulti( array $data, $expiry = 0 ) {
 202                 $batches = [];
 203                 $conns = [];
 204                 foreach ( $data as $key => $value ) {
 205                         list( $server, $conn ) = $this->getConnection( $key );
 206                         if ( !$conn ) {
 207                                 continue;
 208                         }
 209                         $conns[$server] = $conn;
 210                         $batches[$server][] = $key;
 211                 }
 212
 213                 $expiry = $this->convertToRelative( $expiry );
 214                 $result = true;
 215                 foreach ( $batches as $server => $batchKeys ) {
 216                         $conn = $conns[$server];
 217                         try {
 218                                 $conn->multi( Redis::PIPELINE );
 219                                 foreach ( $batchKeys as $key ) {
 220                                         if ( $expiry ) {
 221                                                 $conn->setex( $key, $expiry, $this->serialize( $data[$key] ) );
 222                                         } else {
 223                                                 $conn->set( $key, $this->serialize( $data[$key] ) );
 224                                         }
 225                                 }
 226                                 $batchResult = $conn->exec();
 227                                 if ( $batchResult === false ) {
 228                                         $this->debug( "setMulti request to $server failed" );
 229                                         continue;
 230                                 }
 231                                 foreach ( $batchResult as $value ) {
 232                                         if ( $value === false ) {
 233                                                 $result = false;
 234                                         }
 235                                 }
 236                         } catch ( RedisException $e ) {
 237                                 $this->handleException( $server, $conn, $e );
 238                                 $result = false;
 239                         }
 240                 }
 241
 242                 return $result;
 243         }
 244
 245         public function add( $key, $value, $expiry = 0 ) {
 246                 list( $server, $conn ) = $this->getConnection( $key );
 247                 if ( !$conn ) {
 248                         return false;
 249                 }
 250                 $expiry = $this->convertToRelative( $expiry );
 251                 try {
 252                         if ( $expiry ) {
 253                                 $result = $conn->set(
 254                                         $key,
 255                                         $this->serialize( $value ),
 256                                         [ 'nx', 'ex' => $expiry ]
 257                                 );
 258                         } else {
 259                                 $result = $conn->setnx( $key, $this->serialize( $value ) );
 260                         }
 261                 } catch ( RedisException $e ) {
 262                         $result = false;
 263                         $this->handleException( $conn, $e );
 264                 }
 265
 266                 $this->logRequest( 'add', $key, $server, $result );
 267                 return $result;
 268         }
 269
 270         public function merge( $key, callable $callback, $exptime = 0, $attempts = 10, $flags = 0 ) {
 271                 return $this->mergeViaCas( $key, $callback, $exptime, $attempts );
 272         }
 273
 274         /**
 275          * Non-atomic implementation of incr().
 276          *
 277          * Probably all callers actually want incr() to atomically initialise
 278          * values to zero if they don't exist, as provided by the Redis INCR
 279          * command. But we are constrained by the memcached-like interface to
 280          * return null in that case. Once the key exists, further increments are
 281          * atomic.
 282          * @param string $key Key to increase
 283          * @param int $value Value to add to $key (Default 1)
 284          * @return int|bool New value or false on failure
 285          */
 286         public function incr( $key, $value = 1 ) {
 287                 list( $server, $conn ) = $this->getConnection( $key );
 288                 if ( !$conn ) {
 289                         return false;
 290                 }
 291                 try {
 292                         if ( !$conn->exists( $key ) ) {
 293                                 return false;
 294                         }
 295                         // @FIXME: on races, the key may have a 0 TTL
 296                         $result = $conn->incrBy( $key, $value );
 297                 } catch ( RedisException $e ) {
 298                         $result = false;
 299                         $this->handleException( $conn, $e );
 300                 }
 301
 302                 $this->logRequest( 'incr', $key, $server, $result );
 303                 return $result;
 304         }
 305
 306         public function changeTTL( $key, $expiry = 0 ) {
 307                 list( $server, $conn ) = $this->getConnection( $key );
 308                 if ( !$conn ) {
 309                         return false;
 310                 }
 311
 312                 $expiry = $this->convertToRelative( $expiry );
 313                 try {
 314                         $result = $conn->expire( $key, $expiry );
 315                 } catch ( RedisException $e ) {
 316                         $result = false;
 317                         $this->handleException( $conn, $e );
 318                 }
 319
 320                 $this->logRequest( 'expire', $key, $server, $result );
 321                 return $result;
 322         }
 323
 324         public function modifySimpleRelayEvent( array $event ) {
 325                 if ( array_key_exists( 'val', $event ) ) {
 326                         $event['val'] = serialize( $event['val'] ); // this class uses PHP serialization
 327                 }
 328
 329                 return $event;
 330         }
 331
 332         /**
 333          * @param mixed $data
 334          * @return string
 335          */
 336         protected function serialize( $data ) {
 337                 // Serialize anything but integers so INCR/DECR work
 338                 // Do not store integer-like strings as integers to avoid type confusion (T62563)
 339                 return is_int( $data ) ? $data : serialize( $data );
 340         }
 341
 342         /**
 343          * @param string $data
 344          * @return mixed
 345          */
 346         protected function unserialize( $data ) {
 347                 $int = intval( $data );
 348                 return $data === (string)$int ? $int : unserialize( $data );
 349         }
 350
 351         /**
 352          * Get a Redis object with a connection suitable for fetching the specified key
 353          * @param string $key
 354          * @return array (server, RedisConnRef) or (false, false)
 355          */
 356         protected function getConnection( $key ) {
 357                 $candidates = array_keys( $this->serverTagMap );
 358
 359                 if ( count( $this->servers ) > 1 ) {
 360                         ArrayUtils::consistentHashSort( $candidates, $key, '/' );
 361                         if ( !$this->automaticFailover ) {
 362                                 $candidates = array_slice( $candidates, 0, 1 );
 363                         }
 364                 }
 365
 366                 while ( ( $tag = array_shift( $candidates ) ) !== null ) {
 367                         $server = $this->serverTagMap[$tag];
 368                         $conn = $this->redisPool->getConnection( $server, $this->logger );
 369                         if ( !$conn ) {
 370                                 continue;
 371                         }
 372
 373                         // If automatic failover is enabled, check that the server's link
 374                         // to its master (if any) is up -- but only if there are other
 375                         // viable candidates left to consider. Also, getMasterLinkStatus()
 376                         // does not work with twemproxy, though $candidates will be empty
 377                         // by now in such cases.
 378                         if ( $this->automaticFailover && $candidates ) {
 379                                 try {
 380                                         if ( $this->getMasterLinkStatus( $conn ) === 'down' ) {
 381                                                 // If the master cannot be reached, fail-over to the next server.
 382                                                 // If masters are in data-center A, and replica DBs in data-center B,
 383                                                 // this helps avoid the case were fail-over happens in A but not
 384                                                 // to the corresponding server in B (e.g. read/write mismatch).
 385                                                 continue;
 386                                         }
 387                                 } catch ( RedisException $e ) {
 388                                         // Server is not accepting commands
 389                                         $this->handleException( $conn, $e );
 390                                         continue;
 391                                 }
 392                         }
 393
 394                         return [ $server, $conn ];
 395                 }
 396
 397                 $this->setLastError( BagOStuff::ERR_UNREACHABLE );
 398
 399                 return [ false, false ];
 400         }
 401
 402         /**
 403          * Check the master link status of a Redis server that is configured as a replica DB.
 404          * @param RedisConnRef $conn
 405          * @return string|null Master link status (either 'up' or 'down'), or null
 406          *  if the server is not a replica DB.
 407          */
 408         protected function getMasterLinkStatus( RedisConnRef $conn ) {
 409                 $info = $conn->info();
 410                 return $info['master_link_status'] ?? null;
 411         }
 412
 413         /**
 414          * Log a fatal error
 415          * @param string $msg
 416          */
 417         protected function logError( $msg ) {
 418                 $this->logger->error( "Redis error: $msg" );
 419         }
 420
 421         /**
 422          * The redis extension throws an exception in response to various read, write
 423          * and protocol errors. Sometimes it also closes the connection, sometimes
 424          * not. The safest response for us is to explicitly destroy the connection
 425          * object and let it be reopened during the next request.
 426          * @param RedisConnRef $conn
 427          * @param Exception $e
 428          */
 429         protected function handleException( RedisConnRef $conn, $e ) {
 430                 $this->setLastError( BagOStuff::ERR_UNEXPECTED );
 431                 $this->redisPool->handleError( $conn, $e );
 432         }
 433
 434         /**
 435          * Send information about a single request to the debug log
 436          * @param string $method
 437          * @param string $key
 438          * @param string $server
 439          * @param bool $result
 440          */
 441         public function logRequest( $method, $key, $server, $result ) {
 442                 $this->debug( "$method $key on $server: " .
 443                         ( $result === false ? "failure" : "success" ) );
 444         }
 445 }