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 class RedisBagOStuff extends BagOStuff {
  25         protected $connectTimeout, $persistent, $password, $automaticFailover;
  26
  27         /**
  28          * A list of server names, from $params['servers']
  29          */
  30         protected $servers;
  31
  32         /**
  33          * A cache of Redis objects, representing connections to Redis servers.
  34          * The key is the server name.
  35          */
  36         protected $conns = array();
  37
  38         /**
  39          * An array listing "dead" servers which have had a connection error in
  40          * the past. Servers are marked dead for a limited period of time, to
  41          * avoid excessive overhead from repeated connection timeouts. The key in
  42          * the array is the server name, the value is the UNIX timestamp at which
  43          * the server is resurrected.
  44          */
  45         protected $deadServers = array();
  46
  47         /**
  48          * Construct a RedisBagOStuff object. Parameters are:
  49          *
  50          *   - servers: An array of server names. A server name may be a hostname,
  51          *     a hostname/port combination or the absolute path of a UNIX socket.
  52          *     If a hostname is specified but no port, the standard port number
  53          *     6379 will be used. Required.
  54          *
  55          *   - connectTimeout: The timeout for new connections, in seconds. Optional,
  56          *     default is 1 second.
  57          *
  58          *   - persistent: Set this to true to allow connections to persist across
  59          *     multiple web requests. False by default.
  60          *
  61          *   - password: The authentication password, will be sent to Redis in
  62          *     clear text. Optional, if it is unspecified, no AUTH command will be
  63          *     sent.
  64          *
  65          *   - automaticFailover: If this is false, then each key will be mapped to
  66          *     a single server, and if that server is down, any requests for that key
  67          *     will fail. If this is true, a connection failure will cause the client
  68          *     to immediately try the next server in the list (as determined by a
  69          *     consistent hashing algorithm). True by default. This has the
  70          *     potential to create consistency issues if a server is slow enough to
  71          *     flap, for example if it is in swap death.
  72          */
  73         function __construct( $params ) {
  74                 if ( !extension_loaded( 'redis' ) ) {
  75                         throw new MWException( __CLASS__. ' requires the phpredis extension: ' .
  76                                 'https://github.com/nicolasff/phpredis' );
  77                 }
  78
  79                 $this->servers = $params['servers'];
  80                 $this->connectTimeout = isset( $params['connectTimeout'] )
  81                         ? $params['connectTimeout'] : 1;
  82                 $this->persistent = !empty( $params['persistent'] );
  83                 if ( isset( $params['password'] ) ) {
  84                         $this->password = $params['password'];
  85                 }
  86                 if ( isset( $params['automaticFailover'] ) ) {
  87                         $this->automaticFailover = $params['automaticFailover'];
  88                 } else {
  89                         $this->automaticFailover = true;
  90                 }
  91         }
  92
  93         public function get( $key, &$casToken = null ) {
  94                 wfProfileIn( __METHOD__ );
  95                 list( $server, $conn ) = $this->getConnection( $key );
  96                 if ( !$conn ) {
  97                         wfProfileOut( __METHOD__ );
  98                         return false;
  99                 }
 100                 try {
 101                         $result = $conn->get( $key );
 102                 } catch ( RedisException $e ) {
 103                         $result = false;
 104                         $this->handleException( $server, $e );
 105                 }
 106                 $casToken = $result;
 107                 $this->logRequest( 'get', $key, $server, $result );
 108                 wfProfileOut( __METHOD__ );
 109                 return $result;
 110         }
 111
 112         public function set( $key, $value, $expiry = 0 ) {
 113                 wfProfileIn( __METHOD__ );
 114                 list( $server, $conn ) = $this->getConnection( $key );
 115                 if ( !$conn ) {
 116                         wfProfileOut( __METHOD__ );
 117                         return false;
 118                 }
 119                 $expiry = $this->convertToRelative( $expiry );
 120                 try {
 121                         if ( !$expiry ) {
 122                                 // No expiry, that is very different from zero expiry in Redis
 123                                 $result = $conn->set( $key, $value );
 124                         } else {
 125                                 $result = $conn->setex( $key, $expiry, $value );
 126                         }
 127                 } catch ( RedisException $e ) {
 128                         $result = false;
 129                         $this->handleException( $server, $e );
 130                 }
 131
 132                 $this->logRequest( 'set', $key, $server, $result );
 133                 wfProfileOut( __METHOD__ );
 134                 return $result;
 135         }
 136
 137         /**
 138          * @param $casToken mixed
 139          * @param $key string
 140          * @param $value mixed
 141          * @param $exptime int
 142          * @return bool
 143          */
 144         public function cas( $casToken, $key, $value, $expiry = 0 ) {
 145                 wfProfileIn( __METHOD__ );
 146                 list( $server, $conn ) = $this->getConnection( $key );
 147                 if ( !$conn ) {
 148                         wfProfileOut( __METHOD__ );
 149                         return false;
 150                 }
 151                 $expiry = $this->convertToRelative( $expiry );
 152                 try {
 153                         $conn->watch( $key );
 154
 155                         if ( $this->get( $key ) !== $casToken ) {
 156                                 wfProfileOut( __METHOD__ );
 157                                 return false;
 158                         }
 159
 160                         $conn->multi();
 161
 162                         if ( !$expiry ) {
 163                                 // No expiry, that is very different from zero expiry in Redis
 164                                 $conn->set( $key, $value );
 165                         } else {
 166                                 $conn->setex( $key, $expiry, $value );
 167                         }
 168
 169                         $result = $conn->exec();
 170                 } catch ( RedisException $e ) {
 171                         $result = false;
 172                         $this->handleException( $server, $e );
 173                 }
 174
 175                 $this->logRequest( 'cas', $key, $server, $result );
 176                 wfProfileOut( __METHOD__ );
 177                 return $result;
 178         }
 179
 180         public function delete( $key, $time = 0 ) {
 181                 wfProfileIn( __METHOD__ );
 182                 list( $server, $conn ) = $this->getConnection( $key );
 183                 if ( !$conn ) {
 184                         wfProfileOut( __METHOD__ );
 185                         return false;
 186                 }
 187                 try {
 188                         $conn->delete( $key );
 189                         // Return true even if the key didn't exist
 190                         $result = true;
 191                 } catch ( RedisException $e ) {
 192                         $result = false;
 193                         $this->handleException( $server, $e );
 194                 }
 195                 $this->logRequest( 'delete', $key, $server, $result );
 196                 wfProfileOut( __METHOD__ );
 197                 return $result;
 198         }
 199
 200         public function getMulti( array $keys ) {
 201                 wfProfileIn( __METHOD__ );
 202                 $batches = array();
 203                 $conns = array();
 204                 foreach ( $keys as $key ) {
 205                         list( $server, $conn ) = $this->getConnection( $key );
 206                         if ( !$conn ) {
 207                                 continue;
 208                         }
 209                         $conns[$server] = $conn;
 210                         $batches[$server][] = $key;
 211                 }
 212                 $result = array();
 213                 foreach ( $batches as $server => $batchKeys ) {
 214                         $conn = $conns[$server];
 215                         try {
 216                                 $conn->multi( Redis::PIPELINE );
 217                                 foreach ( $batchKeys as $key ) {
 218                                         $conn->get( $key );
 219                                 }
 220                                 $batchResult = $conn->exec();
 221                                 if ( $batchResult === false ) {
 222                                         $this->debug( "multi request to $server failed" );
 223                                         continue;
 224                                 }
 225                                 foreach ( $batchResult as $i => $value ) {
 226                                         if ( $value !== false ) {
 227                                                 $result[$batchKeys[$i]] = $value;
 228                                         }
 229                                 }
 230                         } catch ( RedisException $e ) {
 231                                 $this->handleException( $server, $e );
 232                         }
 233                 }
 234
 235                 $this->debug( "getMulti for " . count( $keys ) . " keys " .
 236                         "returned " . count( $result ) . " results" );
 237                 wfProfileOut( __METHOD__ );
 238                 return $result;
 239         }
 240
 241         public function add( $key, $value, $expiry = 0 ) {
 242                 wfProfileIn( __METHOD__ );
 243                 list( $server, $conn ) = $this->getConnection( $key );
 244                 if ( !$conn ) {
 245                         wfProfileOut( __METHOD__ );
 246                         return false;
 247                 }
 248                 $expiry = $this->convertToRelative( $expiry );
 249                 try {
 250                         $result = $conn->setnx( $key, $value );
 251                         if ( $result && $expiry ) {
 252                                 $conn->expire( $key, $expiry );
 253                         }
 254                 } catch ( RedisException $e ) {
 255                         $result = false;
 256                         $this->handleException( $server, $e );
 257                 }
 258                 $this->logRequest( 'add', $key, $server, $result );
 259                 wfProfileOut( __METHOD__ );
 260                 return $result;
 261         }
 262
 263         /**
 264          * Non-atomic implementation of replace(). Could perhaps be done atomically
 265          * with WATCH or scripting, but this function is rarely used.
 266          */
 267         public function replace( $key, $value, $expiry = 0 ) {
 268                 wfProfileIn( __METHOD__ );
 269                 list( $server, $conn ) = $this->getConnection( $key );
 270                 if ( !$conn ) {
 271                         wfProfileOut( __METHOD__ );
 272                         return false;
 273                 }
 274                 if ( !$conn->exists( $key ) ) {
 275                         wfProfileOut( __METHOD__ );
 276                         return false;
 277                 }
 278
 279                 $expiry = $this->convertToRelative( $expiry );
 280                 try {
 281                         if ( !$expiry ) {
 282                                 $result = $conn->set( $key, $value );
 283                         } else {
 284                                 $result = $conn->setex( $key, $expiry, $value );
 285                         }
 286                 } catch ( RedisException $e ) {
 287                         $result = false;
 288                         $this->handleException( $server, $e );
 289                 }
 290
 291                 $this->logRequest( 'replace', $key, $server, $result );
 292                 wfProfileOut( __METHOD__ );
 293                 return $result;
 294         }
 295
 296         /**
 297          * Non-atomic implementation of incr().
 298          *
 299          * Probably all callers actually want incr() to atomically initialise
 300          * values to zero if they don't exist, as provided by the Redis INCR
 301          * command. But we are constrained by the memcached-like interface to
 302          * return null in that case. Once the key exists, further increments are
 303          * atomic.
 304          */
 305         public function incr( $key, $value = 1 ) {
 306                 wfProfileIn( __METHOD__ );
 307                 list( $server, $conn ) = $this->getConnection( $key );
 308                 if ( !$conn ) {
 309                         wfProfileOut( __METHOD__ );
 310                         return false;
 311                 }
 312                 if ( !$conn->exists( $key ) ) {
 313                         wfProfileOut( __METHOD__ );
 314                         return null;
 315                 }
 316                 try {
 317                         $result = $conn->incrBy( $key, $value );
 318                 } catch ( RedisException $e ) {
 319                         $result = false;
 320                         $this->handleException( $server, $e );
 321                 }
 322
 323                 $this->logRequest( 'incr', $key, $server, $result );
 324                 wfProfileOut( __METHOD__ );
 325                 return $result;
 326         }
 327
 328         /**
 329          * Get a Redis object with a connection suitable for fetching the specified key
 330          */
 331         protected function getConnection( $key ) {
 332                 if ( count( $this->servers ) === 1 ) {
 333                         $candidates = $this->servers;
 334                 } else {
 335                         $candidates = $this->servers;
 336                         ArrayUtils::consistentHashSort( $candidates, $key, '/' );
 337                         if ( !$this->automaticFailover ) {
 338                                 $candidates = array_slice( $candidates, 0, 1 );
 339                         }
 340                 }
 341
 342                 foreach ( $candidates as $server ) {
 343                         $conn = $this->getConnectionToServer( $server );
 344                         if ( $conn ) {
 345                                 return array( $server, $conn );
 346                         }
 347                 }
 348                 return array( false, false );
 349         }
 350
 351         /**
 352          * Get a connection to the server with the specified name. Connections
 353          * are cached, and failures are persistent to avoid multiple timeouts.
 354          *
 355          * @param $server
 356          * @throws MWException
 357          * @return Redis object, or false on failure
 358          */
 359         protected function getConnectionToServer( $server ) {
 360                 if ( isset( $this->deadServers[$server] ) ) {
 361                         $now = time();
 362                         if ( $now > $this->deadServers[$server] ) {
 363                                 // Dead time expired
 364                                 unset( $this->deadServers[$server] );
 365                         } else {
 366                                 // Server is dead
 367                                 $this->debug( "server $server is marked down for another " .
 368                                         ($this->deadServers[$server] - $now ) .
 369                                         " seconds, can't get connection" );
 370                                 return false;
 371                         }
 372                 }
 373
 374                 if ( isset( $this->conns[$server] ) ) {
 375                         return $this->conns[$server];
 376                 }
 377
 378                 if ( substr( $server, 0, 1 ) === '/' ) {
 379                         // UNIX domain socket
 380                         // These are required by the redis extension to start with a slash, but
 381                         // we still need to set the port to a special value to make it work.
 382                         $host = $server;
 383                         $port = 0;
 384                 } else {
 385                         // TCP connection
 386                         $hostPort = IP::splitHostAndPort( $server );
 387                         if ( !$hostPort ) {
 388                                 throw new MWException( __CLASS__.": invalid configured server \"$server\"" );
 389                         }
 390                         list( $host, $port ) = $hostPort;
 391                         if ( $port === false ) {
 392                                 $port = 6379;
 393                         }
 394                 }
 395                 $conn = new Redis;
 396                 try {
 397                         if ( $this->persistent ) {
 398                                 $this->debug( "opening persistent connection to $host:$port" );
 399                                 $result = $conn->pconnect( $host, $port, $this->connectTimeout );
 400                         } else {
 401                                 $this->debug( "opening non-persistent connection to $host:$port" );
 402                                 $result = $conn->connect( $host, $port, $this->connectTimeout );
 403                         }
 404                         if ( !$result ) {
 405                                 $this->logError( "could not connect to server $server" );
 406                                 // Mark server down for 30s to avoid further timeouts
 407                                 $this->deadServers[$server] = time() + 30;
 408                                 return false;
 409                         }
 410                         if ( $this->password !== null ) {
 411                                 if ( !$conn->auth( $this->password ) ) {
 412                                         $this->logError( "authentication error connecting to $server" );
 413                                 }
 414                         }
 415                 } catch ( RedisException $e ) {
 416                         $this->deadServers[$server] = time() + 30;
 417                         wfDebugLog( 'redis', "Redis exception: " . $e->getMessage() . "\n" );
 418                         return false;
 419                 }
 420
 421                 $conn->setOption( Redis::OPT_SERIALIZER, Redis::SERIALIZER_PHP );
 422                 $this->conns[$server] = $conn;
 423                 return $conn;
 424         }
 425
 426         /**
 427          * Log a fatal error
 428          */
 429         protected function logError( $msg ) {
 430                 wfDebugLog( 'redis', "Redis error: $msg\n" );
 431         }
 432
 433         /**
 434          * The redis extension throws an exception in response to various read, write
 435          * and protocol errors. Sometimes it also closes the connection, sometimes
 436          * not. The safest response for us is to explicitly destroy the connection
 437          * object and let it be reopened during the next request.
 438          */
 439         protected function handleException( $server, $e ) {
 440                 wfDebugLog( 'redis', "Redis exception on server $server: " . $e->getMessage() . "\n" );
 441                 unset( $this->conns[$server] );
 442         }
 443
 444         /**
 445          * Send information about a single request to the debug log
 446          */
 447         public function logRequest( $method, $key, $server, $result ) {
 448                 $this->debug( "$method $key on $server: " .
 449                         ( $result === false ? "failure" : "success" ) );
 450         }
 451 }
 452