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 ) {
  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                 $this->logRequest( 'get', $key, $server, $result );
 107                 wfProfileOut( __METHOD__ );
 108                 return $result;
 109         }
 110
 111         public function set( $key, $value, $expiry = 0 ) {
 112                 wfProfileIn( __METHOD__ );
 113                 list( $server, $conn ) = $this->getConnection( $key );
 114                 if ( !$conn ) {
 115                         wfProfileOut( __METHOD__ );
 116                         return false;
 117                 }
 118                 $expiry = $this->convertToRelative( $expiry );
 119                 try {
 120                         if ( !$expiry ) {
 121                                 // No expiry, that is very different from zero expiry in Redis
 122                                 $result = $conn->set( $key, $value );
 123                         } else {
 124                                 $result = $conn->setex( $key, $expiry, $value );
 125                         }
 126                 } catch ( RedisException $e ) {
 127                         $result = false;
 128                         $this->handleException( $server, $e );
 129                 }
 130
 131                 $this->logRequest( 'set', $key, $server, $result );
 132                 wfProfileOut( __METHOD__ );
 133                 return $result;
 134         }
 135
 136         public function delete( $key, $time = 0 ) {
 137                 wfProfileIn( __METHOD__ );
 138                 list( $server, $conn ) = $this->getConnection( $key );
 139                 if ( !$conn ) {
 140                         wfProfileOut( __METHOD__ );
 141                         return false;
 142                 }
 143                 try {
 144                         $conn->delete( $key );
 145                         // Return true even if the key didn't exist
 146                         $result = true;
 147                 } catch ( RedisException $e ) {
 148                         $result = false;
 149                         $this->handleException( $server, $e );
 150                 }
 151                 $this->logRequest( 'delete', $key, $server, $result );
 152                 wfProfileOut( __METHOD__ );
 153                 return $result;
 154         }
 155
 156         public function getMulti( array $keys ) {
 157                 wfProfileIn( __METHOD__ );
 158                 $batches = array();
 159                 $conns = array();
 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 = array();
 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]] = $value;
 184                                         }
 185                                 }
 186                         } catch ( RedisException $e ) {
 187                                 $this->handleException( $server, $e );
 188                         }
 189                 }
 190
 191                 $this->debug( "getMulti for " . count( $keys ) . " keys " .
 192                         "returned " . count( $result ) . " results" );
 193                 wfProfileOut( __METHOD__ );
 194                 return $result;
 195         }
 196
 197         public function add( $key, $value, $expiry = 0 ) {
 198                 wfProfileIn( __METHOD__ );
 199                 list( $server, $conn ) = $this->getConnection( $key );
 200                 if ( !$conn ) {
 201                         wfProfileOut( __METHOD__ );
 202                         return false;
 203                 }
 204                 $expiry = $this->convertToRelative( $expiry );
 205                 try {
 206                         $result = $conn->setnx( $key, $value );
 207                         if ( $result && $expiry ) {
 208                                 $conn->expire( $key, $expiry );
 209                         }
 210                 } catch ( RedisException $e ) {
 211                         $result = false;
 212                         $this->handleException( $server, $e );
 213                 }
 214                 $this->logRequest( 'add', $key, $server, $result );
 215                 wfProfileOut( __METHOD__ );
 216                 return $result;
 217         }
 218
 219         /**
 220          * Non-atomic implementation of replace(). Could perhaps be done atomically
 221          * with WATCH or scripting, but this function is rarely used.
 222          */
 223         public function replace( $key, $value, $expiry = 0 ) {
 224                 wfProfileIn( __METHOD__ );
 225                 list( $server, $conn ) = $this->getConnection( $key );
 226                 if ( !$conn ) {
 227                         wfProfileOut( __METHOD__ );
 228                         return false;
 229                 }
 230                 if ( !$conn->exists( $key ) ) {
 231                         wfProfileOut( __METHOD__ );
 232                         return false;
 233                 }
 234
 235                 $expiry = $this->convertToRelative( $expiry );
 236                 try {
 237                         if ( !$expiry ) {
 238                                 $result = $conn->set( $key, $value );
 239                         } else {
 240                                 $result = $conn->setex( $key, $expiry, $value );
 241                         }
 242                 } catch ( RedisException $e ) {
 243                         $result = false;
 244                         $this->handleException( $server, $e );
 245                 }
 246
 247                 $this->logRequest( 'replace', $key, $server, $result );
 248                 wfProfileOut( __METHOD__ );
 249                 return $result;
 250         }
 251
 252         /**
 253          * Non-atomic implementation of incr().
 254          *
 255          * Probably all callers actually want incr() to atomically initialise
 256          * values to zero if they don't exist, as provided by the Redis INCR
 257          * command. But we are constrained by the memcached-like interface to
 258          * return null in that case. Once the key exists, further increments are
 259          * atomic.
 260          */
 261         public function incr( $key, $value = 1 ) {
 262                 wfProfileIn( __METHOD__ );
 263                 list( $server, $conn ) = $this->getConnection( $key );
 264                 if ( !$conn ) {
 265                         wfProfileOut( __METHOD__ );
 266                         return false;
 267                 }
 268                 if ( !$conn->exists( $key ) ) {
 269                         wfProfileOut( __METHOD__ );
 270                         return null;
 271                 }
 272                 try {
 273                         $result = $conn->incrBy( $key, $value );
 274                 } catch ( RedisException $e ) {
 275                         $result = false;
 276                         $this->handleException( $server, $e );
 277                 }
 278
 279                 $this->logRequest( 'incr', $key, $server, $result );
 280                 wfProfileOut( __METHOD__ );
 281                 return $result;
 282         }
 283
 284         /**
 285          * Get a Redis object with a connection suitable for fetching the specified key
 286          */
 287         protected function getConnection( $key ) {
 288                 if ( count( $this->servers ) === 1 ) {
 289                         $candidates = $this->servers;
 290                 } else {
 291                         // Use consistent hashing
 292                         //
 293                         // Note: Benchmarking on PHP 5.3 and 5.4 indicates that for small
 294                         // strings, md5() is only 10% slower than hash('joaat',...) etc.,
 295                         // since the function call overhead dominates. So there's not much
 296                         // justification for breaking compatibility with installations
 297                         // compiled with ./configure --disable-hash.
 298                         $hashes = array();
 299                         foreach ( $this->servers as $server ) {
 300                                 $hashes[$server] = md5( $server . '/' . $key );
 301                         }
 302                         asort( $hashes );
 303                         if ( !$this->automaticFailover ) {
 304                                 reset( $hashes );
 305                                 $candidates = array( key( $hashes ) );
 306                         } else {
 307                                 $candidates = array_keys( $hashes );
 308                         }
 309                 }
 310
 311                 foreach ( $candidates as $server ) {
 312                         $conn = $this->getConnectionToServer( $server );
 313                         if ( $conn ) {
 314                                 return array( $server, $conn );
 315                         }
 316                 }
 317                 return array( false, false );
 318         }
 319
 320         /**
 321          * Get a connection to the server with the specified name. Connections
 322          * are cached, and failures are persistent to avoid multiple timeouts.
 323          *
 324          * @return Redis object, or false on failure
 325          */
 326         protected function getConnectionToServer( $server ) {
 327                 if ( isset( $this->deadServers[$server] ) ) {
 328                         $now = time();
 329                         if ( $now > $this->deadServers[$server] ) {
 330                                 // Dead time expired
 331                                 unset( $this->deadServers[$server] );
 332                         } else {
 333                                 // Server is dead
 334                                 $this->debug( "server $server is marked down for another " .
 335                                         ($this->deadServers[$server] - $now ) .
 336                                         " seconds, can't get connection" );
 337                                 return false;
 338                         }
 339                 }
 340
 341                 if ( isset( $this->conns[$server] ) ) {
 342                         return $this->conns[$server];
 343                 }
 344
 345                 if ( substr( $server, 0, 1 ) === '/' ) {
 346                         // UNIX domain socket
 347                         // These are required by the redis extension to start with a slash, but
 348                         // we still need to set the port to a special value to make it work.
 349                         $host = $server;
 350                         $port = 0;
 351                 } else {
 352                         // TCP connection
 353                         $hostPort = IP::splitHostAndPort( $server );
 354                         if ( !$hostPort ) {
 355                                 throw new MWException( __CLASS__.": invalid configured server \"$server\"" );
 356                         }
 357                         list( $host, $port ) = $hostPort;
 358                         if ( $port === false ) {
 359                                 $port = 6379;
 360                         }
 361                 }
 362                 $conn = new Redis;
 363                 try {
 364                         if ( $this->persistent ) {
 365                                 $this->debug( "opening persistent connection to $host:$port" );
 366                                 $result = $conn->pconnect( $host, $port, $this->connectTimeout );
 367                         } else {
 368                                 $this->debug( "opening non-persistent connection to $host:$port" );
 369                                 $result = $conn->connect( $host, $port, $this->connectTimeout );
 370                         }
 371                         if ( !$result ) {
 372                                 $this->logError( "could not connect to server $server" );
 373                                 // Mark server down for 30s to avoid further timeouts
 374                                 $this->deadServers[$server] = time() + 30;
 375                                 return false;
 376                         }
 377                         if ( $this->password !== null ) {
 378                                 if ( !$conn->auth( $this->password ) ) {
 379                                         $this->logError( "authentication error connecting to $server" );
 380                                 }
 381                         }
 382                 } catch ( RedisException $e ) {
 383                         $this->deadServers[$server] = time() + 30;
 384                         wfDebugLog( 'redis', "Redis exception: " . $e->getMessage() . "\n" );
 385                         return false;
 386                 }
 387
 388                 $conn->setOption( Redis::OPT_SERIALIZER, Redis::SERIALIZER_PHP );
 389                 $this->conns[$server] = $conn;
 390                 return $conn;
 391         }
 392
 393         /**
 394          * Log a fatal error
 395          */
 396         protected function logError( $msg ) {
 397                 wfDebugLog( 'redis', "Redis error: $msg\n" );
 398         }
 399
 400         /**
 401          * The redis extension throws an exception in response to various read, write
 402          * and protocol errors. Sometimes it also closes the connection, sometimes
 403          * not. The safest response for us is to explicitly destroy the connection
 404          * object and let it be reopened during the next request.
 405          */
 406         protected function handleException( $server, $e ) {
 407                 wfDebugLog( 'redis', "Redis exception on server $server: " . $e->getMessage() . "\n" );
 408                 unset( $this->conns[$server] );
 409         }
 410
 411         /**
 412          * Send information about a single request to the debug log
 413          */
 414         public function logRequest( $method, $key, $server, $result ) {
 415                 $this->debug( "$method $key on $server: " .
 416                         ( $result === false ? "failure" : "success" ) );
 417         }
 418 }
 419