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         /**
 193          * @param array $data
 194          * @param int $expiry
 195          * @return bool
 196          */
 197         public function setMulti( array $data, $expiry = 0 ) {
 198                 $batches = [];
 199                 $conns = [];
 200                 foreach ( $data as $key => $value ) {
 201                         list( $server, $conn ) = $this->getConnection( $key );
 202                         if ( !$conn ) {
 203                                 continue;
 204                         }
 205                         $conns[$server] = $conn;
 206                         $batches[$server][] = $key;
 207                 }
 208
 209                 $expiry = $this->convertToRelative( $expiry );
 210                 $result = true;
 211                 foreach ( $batches as $server => $batchKeys ) {
 212                         $conn = $conns[$server];
 213                         try {
 214                                 $conn->multi( Redis::PIPELINE );
 215                                 foreach ( $batchKeys as $key ) {
 216                                         if ( $expiry ) {
 217                                                 $conn->setex( $key, $expiry, $this->serialize( $data[$key] ) );
 218                                         } else {
 219                                                 $conn->set( $key, $this->serialize( $data[$key] ) );
 220                                         }
 221                                 }
 222                                 $batchResult = $conn->exec();
 223                                 if ( $batchResult === false ) {
 224                                         $this->debug( "setMulti request to $server failed" );
 225                                         continue;
 226                                 }
 227                                 foreach ( $batchResult as $value ) {
 228                                         if ( $value === false ) {
 229                                                 $result = false;
 230                                         }
 231                                 }
 232                         } catch ( RedisException $e ) {
 233                                 $this->handleException( $conn, $e );
 234                                 $result = false;
 235                         }
 236                 }
 237
 238                 return $result;
 239         }
 240
 241         public function add( $key, $value, $expiry = 0 ) {
 242                 list( $server, $conn ) = $this->getConnection( $key );
 243                 if ( !$conn ) {
 244                         return false;
 245                 }
 246                 $expiry = $this->convertToRelative( $expiry );
 247                 try {
 248                         if ( $expiry ) {
 249                                 $result = $conn->set(
 250                                         $key,
 251                                         $this->serialize( $value ),
 252                                         [ 'nx', 'ex' => $expiry ]
 253                                 );
 254                         } else {
 255                                 $result = $conn->setnx( $key, $this->serialize( $value ) );
 256                         }
 257                 } catch ( RedisException $e ) {
 258                         $result = false;
 259                         $this->handleException( $conn, $e );
 260                 }
 261
 262                 $this->logRequest( 'add', $key, $server, $result );
 263                 return $result;
 264         }
 265
 266         public function merge( $key, callable $callback, $exptime = 0, $attempts = 10, $flags = 0 ) {
 267                 return $this->mergeViaCas( $key, $callback, $exptime, $attempts );
 268         }
 269
 270         /**
 271          * Non-atomic implementation of incr().
 272          *
 273          * Probably all callers actually want incr() to atomically initialise
 274          * values to zero if they don't exist, as provided by the Redis INCR
 275          * command. But we are constrained by the memcached-like interface to
 276          * return null in that case. Once the key exists, further increments are
 277          * atomic.
 278          * @param string $key Key to increase
 279          * @param int $value Value to add to $key (Default 1)
 280          * @return int|bool New value or false on failure
 281          */
 282         public function incr( $key, $value = 1 ) {
 283                 list( $server, $conn ) = $this->getConnection( $key );
 284                 if ( !$conn ) {
 285                         return false;
 286                 }
 287                 try {
 288                         if ( !$conn->exists( $key ) ) {
 289                                 return false;
 290                         }
 291                         // @FIXME: on races, the key may have a 0 TTL
 292                         $result = $conn->incrBy( $key, $value );
 293                 } catch ( RedisException $e ) {
 294                         $result = false;
 295                         $this->handleException( $conn, $e );
 296                 }
 297
 298                 $this->logRequest( 'incr', $key, $server, $result );
 299                 return $result;
 300         }
 301
 302         public function changeTTL( $key, $expiry = 0 ) {
 303                 list( $server, $conn ) = $this->getConnection( $key );
 304                 if ( !$conn ) {
 305                         return false;
 306                 }
 307
 308                 $expiry = $this->convertToRelative( $expiry );
 309                 try {
 310                         $result = $conn->expire( $key, $expiry );
 311                 } catch ( RedisException $e ) {
 312                         $result = false;
 313                         $this->handleException( $conn, $e );
 314                 }
 315
 316                 $this->logRequest( 'expire', $key, $server, $result );
 317                 return $result;
 318         }
 319
 320         /**
 321          * @param mixed $data
 322          * @return string
 323          */
 324         protected function serialize( $data ) {
 325                 // Serialize anything but integers so INCR/DECR work
 326                 // Do not store integer-like strings as integers to avoid type confusion (T62563)
 327                 return is_int( $data ) ? $data : serialize( $data );
 328         }
 329
 330         /**
 331          * @param string $data
 332          * @return mixed
 333          */
 334         protected function unserialize( $data ) {
 335                 $int = intval( $data );
 336                 return $data === (string)$int ? $int : unserialize( $data );
 337         }
 338
 339         /**
 340          * Get a Redis object with a connection suitable for fetching the specified key
 341          * @param string $key
 342          * @return array (server, RedisConnRef) or (false, false)
 343          */
 344         protected function getConnection( $key ) {
 345                 $candidates = array_keys( $this->serverTagMap );
 346
 347                 if ( count( $this->servers ) > 1 ) {
 348                         ArrayUtils::consistentHashSort( $candidates, $key, '/' );
 349                         if ( !$this->automaticFailover ) {
 350                                 $candidates = array_slice( $candidates, 0, 1 );
 351                         }
 352                 }
 353
 354                 while ( ( $tag = array_shift( $candidates ) ) !== null ) {
 355                         $server = $this->serverTagMap[$tag];
 356                         $conn = $this->redisPool->getConnection( $server, $this->logger );
 357                         if ( !$conn ) {
 358                                 continue;
 359                         }
 360
 361                         // If automatic failover is enabled, check that the server's link
 362                         // to its master (if any) is up -- but only if there are other
 363                         // viable candidates left to consider. Also, getMasterLinkStatus()
 364                         // does not work with twemproxy, though $candidates will be empty
 365                         // by now in such cases.
 366                         if ( $this->automaticFailover && $candidates ) {
 367                                 try {
 368                                         if ( $this->getMasterLinkStatus( $conn ) === 'down' ) {
 369                                                 // If the master cannot be reached, fail-over to the next server.
 370                                                 // If masters are in data-center A, and replica DBs in data-center B,
 371                                                 // this helps avoid the case were fail-over happens in A but not
 372                                                 // to the corresponding server in B (e.g. read/write mismatch).
 373                                                 continue;
 374                                         }
 375                                 } catch ( RedisException $e ) {
 376                                         // Server is not accepting commands
 377                                         $this->handleException( $conn, $e );
 378                                         continue;
 379                                 }
 380                         }
 381
 382                         return [ $server, $conn ];
 383                 }
 384
 385                 $this->setLastError( BagOStuff::ERR_UNREACHABLE );
 386
 387                 return [ false, false ];
 388         }
 389
 390         /**
 391          * Check the master link status of a Redis server that is configured as a replica DB.
 392          * @param RedisConnRef $conn
 393          * @return string|null Master link status (either 'up' or 'down'), or null
 394          *  if the server is not a replica DB.
 395          */
 396         protected function getMasterLinkStatus( RedisConnRef $conn ) {
 397                 $info = $conn->info();
 398                 return $info['master_link_status'] ?? 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 }