includes/objectcache/RedisBagOStuff.php

   1 <?php
   2
   3 class RedisBagOStuff extends BagOStuff {
   4         protected $connectTimeout, $persistent, $password, $automaticFailover;
   5
   6         /**
   7          * A list of server names, from $params['servers']
   8          */
   9         protected $servers;
  10
  11         /**
  12          * A cache of Redis objects, representing connections to Redis servers.
  13          * The key is the server name.
  14          */
  15         protected $conns = array();
  16
  17         /**
  18          * An array listing "dead" servers which have had a connection error in
  19          * the past. Servers are marked dead for a limited period of time, to
  20          * avoid excessive overhead from repeated connection timeouts. The key in
  21          * the array is the server name, the value is the UNIX timestamp at which
  22          * the server is resurrected.
  23          */
  24         protected $deadServers = array();
  25
  26         /**
  27          * Construct a RedisBagOStuff object. Parameters are:
  28          *
  29          *   - servers: An array of server names. A server name may be a hostname,
  30          *     a hostname/port combination or the absolute path of a UNIX socket.
  31          *     If a hostname is specified but no port, the standard port number
  32          *     6379 will be used. Required.
  33          *
  34          *   - connectTimeout: The timeout for new connections, in seconds. Optional,
  35          *     default is 1 second.
  36          *
  37          *   - persistent: Set this to true to allow connections to persist across
  38          *     multiple web requests. False by default.
  39          *
  40          *   - password: The authentication password, will be sent to Redis in
  41          *     clear text. Optional, if it is unspecified, no AUTH command will be
  42          *     sent.
  43          *
  44          *   - automaticFailover: If this is false, then each key will be mapped to
  45          *     a single server, and if that server is down, any requests for that key
  46          *     will fail. If this is true, a connection failure will cause the client
  47          *     to immediately try the next server in the list (as determined by a
  48          *     consistent hashing algorithm). True by default. This has the
  49          *     potential to create consistency issues if a server is slow enough to
  50          *     flap, for example if it is in swap death.
  51          */
  52         function __construct( $params ) {
  53                 if ( !extension_loaded( 'redis' ) ) {
  54                         throw new MWException( __CLASS__. ' requires the phpredis extension: ' .
  55                                 'https://github.com/nicolasff/phpredis' );
  56                 }
  57
  58                 $this->servers = $params['servers'];
  59                 $this->connectTimeout = isset( $params['connectTimeout'] )
  60                         ? $params['connectTimeout'] : 1;
  61                 $this->persistent = !empty( $params['persistent'] );
  62                 if ( isset( $params['password'] ) ) {
  63                         $this->password = $params['password'];
  64                 }
  65                 if ( isset( $params['automaticFailover'] ) ) {
  66                         $this->automaticFailover = $params['automaticFailover'];
  67                 } else {
  68                         $this->automaticFailover = true;
  69                 }
  70         }
  71
  72         public function get( $key ) {
  73                 wfProfileIn( __METHOD__ );
  74                 list( $server, $conn ) = $this->getConnection( $key );
  75                 if ( !$conn ) {
  76                         wfProfileOut( __METHOD__ );
  77                         return false;
  78                 }
  79                 try {
  80                         $result = $conn->get( $key );
  81                 } catch ( RedisException $e ) {
  82                         $result = false;
  83                         $this->handleException( $server, $e );
  84                 }
  85                 $this->logRequest( 'get', $key, $server, $result );
  86                 wfProfileOut( __METHOD__ );
  87                 return $result;
  88         }
  89
  90         public function set( $key, $value, $expiry = 0 ) {
  91                 wfProfileIn( __METHOD__ );
  92                 list( $server, $conn ) = $this->getConnection( $key );
  93                 if ( !$conn ) {
  94                         wfProfileOut( __METHOD__ );
  95                         return false;
  96                 }
  97                 $expiry = $this->convertToRelative( $expiry );
  98                 try {
  99                         if ( !$expiry ) {
 100                                 // No expiry, that is very different from zero expiry in Redis
 101                                 $result = $conn->set( $key, $value );
 102                         } else {
 103                                 $result = $conn->setex( $key, $expiry, $value );
 104                         }
 105                 } catch ( RedisException $e ) {
 106                         $result = false;
 107                         $this->handleException( $server, $e );
 108                 }
 109
 110                 $this->logRequest( 'set', $key, $server, $result );
 111                 wfProfileOut( __METHOD__ );
 112                 return $result;
 113         }
 114
 115         public function delete( $key, $time = 0 ) {
 116                 wfProfileIn( __METHOD__ );
 117                 list( $server, $conn ) = $this->getConnection( $key );
 118                 if ( !$conn ) {
 119                         wfProfileOut( __METHOD__ );
 120                         return false;
 121                 }
 122                 try {
 123                         $conn->delete( $key );
 124                         // Return true even if the key didn't exist
 125                         $result = true;
 126                 } catch ( RedisException $e ) {
 127                         $result = false;
 128                         $this->handleException( $server, $e );
 129                 }
 130                 $this->logRequest( 'delete', $key, $server, $result );
 131                 wfProfileOut( __METHOD__ );
 132                 return $result;
 133         }
 134
 135         public function getMulti( array $keys ) {
 136                 wfProfileIn( __METHOD__ );
 137                 $batches = array();
 138                 $conns = array();
 139                 foreach ( $keys as $key ) {
 140                         list( $server, $conn ) = $this->getConnection( $key );
 141                         if ( !$conn ) {
 142                                 continue;
 143                         }
 144                         $conns[$server] = $conn;
 145                         $batches[$server][] = $key;
 146                 }
 147                 $result = array();
 148                 foreach ( $batches as $server => $batchKeys ) {
 149                         $conn = $conns[$server];
 150                         try {
 151                                 $conn->multi( Redis::PIPELINE );
 152                                 foreach ( $batchKeys as $key ) {
 153                                         $conn->get( $key );
 154                                 }
 155                                 $batchResult = $conn->exec();
 156                                 if ( $batchResult === false ) {
 157                                         $this->debug( "multi request to $server failed" );
 158                                         continue;
 159                                 }
 160                                 foreach ( $batchResult as $i => $value ) {
 161                                         if ( $value !== false ) {
 162                                                 $result[$batchKeys[$i]] = $value;
 163                                         }
 164                                 }
 165                         } catch ( RedisException $e ) {
 166                                 $this->handleException( $server, $e );
 167                         }
 168                 }
 169
 170                 $this->debug( "getMulti for " . count( $keys ) . " keys " .
 171                         "returned " . count( $result ) . " results" );
 172                 wfProfileOut( __METHOD__ );
 173                 return $result;
 174         }
 175
 176         public function add( $key, $value, $expiry = 0 ) {
 177                 wfProfileIn( __METHOD__ );
 178                 list( $server, $conn ) = $this->getConnection( $key );
 179                 if ( !$conn ) {
 180                         wfProfileOut( __METHOD__ );
 181                         return false;
 182                 }
 183                 $expiry = $this->convertToRelative( $expiry );
 184                 try {
 185                         $result = $conn->setnx( $key, $value );
 186                         if ( $result && $expiry ) {
 187                                 $conn->expire( $key, $expiry );
 188                         }
 189                 } catch ( RedisException $e ) {
 190                         $result = false;
 191                         $this->handleException( $server, $e );
 192                 }
 193                 $this->logRequest( 'add', $key, $server, $result );
 194                 wfProfileOut( __METHOD__ );
 195                 return $result;
 196         }
 197
 198         /**
 199          * Non-atomic implementation of replace(). Could perhaps be done atomically
 200          * with WATCH or scripting, but this function is rarely used.
 201          */
 202         public function replace( $key, $value, $expiry = 0 ) {
 203                 wfProfileIn( __METHOD__ );
 204                 list( $server, $conn ) = $this->getConnection( $key );
 205                 if ( !$conn ) {
 206                         wfProfileOut( __METHOD__ );
 207                         return false;
 208                 }
 209                 if ( !$conn->exists( $key ) ) {
 210                         wfProfileOut( __METHOD__ );
 211                         return false;
 212                 }
 213
 214                 $expiry = $this->convertToRelative( $expiry );
 215                 try {
 216                         if ( !$expiry ) {
 217                                 $result = $conn->set( $key, $value );
 218                         } else {
 219                                 $result = $conn->setex( $key, $expiry, $value );
 220                         }
 221                 } catch ( RedisException $e ) {
 222                         $result = false;
 223                         $this->handleException( $server, $e );
 224                 }
 225
 226                 $this->logRequest( 'replace', $key, $server, $result );
 227                 wfProfileOut( __METHOD__ );
 228                 return $result;
 229         }
 230
 231         /**
 232          * Non-atomic implementation of incr().
 233          *
 234          * Probably all callers actually want incr() to atomically initialise
 235          * values to zero if they don't exist, as provided by the Redis INCR
 236          * command. But we are constrained by the memcached-like interface to
 237          * return null in that case. Once the key exists, further increments are
 238          * atomic.
 239          */
 240         public function incr( $key, $value = 1 ) {
 241                 wfProfileIn( __METHOD__ );
 242                 list( $server, $conn ) = $this->getConnection( $key );
 243                 if ( !$conn ) {
 244                         wfProfileOut( __METHOD__ );
 245                         return false;
 246                 }
 247                 if ( !$conn->exists( $key ) ) {
 248                         wfProfileOut( __METHOD__ );
 249                         return null;
 250                 }
 251                 try {
 252                         $result = $conn->incrBy( $key, $value );
 253                 } catch ( RedisException $e ) {
 254                         $result = false;
 255                         $this->handleException( $server, $e );
 256                 }
 257
 258                 $this->logRequest( 'incr', $key, $server, $result );
 259                 wfProfileOut( __METHOD__ );
 260                 return $result;
 261         }
 262
 263         /**
 264          * Get a Redis object with a connection suitable for fetching the specified key
 265          */
 266         protected function getConnection( $key ) {
 267                 if ( count( $this->servers ) === 1 ) {
 268                         $candidates = $this->servers;
 269                 } else {
 270                         // Use consistent hashing
 271                         $hashes = array();
 272                         foreach ( $this->servers as $server ) {
 273                                 $hashes[$server] = md5( $server . '/' . $key );
 274                         }
 275                         asort( $hashes );
 276                         if ( !$this->automaticFailover ) {
 277                                 reset( $hashes );
 278                                 $candidates = array( key( $hashes ) );
 279                         } else {
 280                                 $candidates = array_keys( $hashes );
 281                         }
 282                 }
 283
 284                 foreach ( $candidates as $server ) {
 285                         $conn = $this->getConnectionToServer( $server );
 286                         if ( $conn ) {
 287                                 return array( $server, $conn );
 288                         }
 289                 }
 290                 return array( false, false );
 291         }
 292
 293         /**
 294          * Get a connection to the server with the specified name. Connections
 295          * are cached, and failures are persistent to avoid multiple timeouts.
 296          *
 297          * @return Redis object, or false on failure
 298          */
 299         protected function getConnectionToServer( $server ) {
 300                 if ( isset( $this->deadServers[$server] ) ) {
 301                         $now = time();
 302                         if ( $now > $this->deadServers[$server] ) {
 303                                 // Dead time expired
 304                                 unset( $this->deadServers[$server] );
 305                         } else {
 306                                 // Server is dead
 307                                 $this->debug( "server $server is marked down for another " .
 308                                         ($this->deadServers[$server] - $now ) .
 309                                         " seconds, can't get connection" );
 310                                 return false;
 311                         }
 312                 }
 313
 314                 if ( isset( $this->conns[$server] ) ) {
 315                         return $this->conns[$server];
 316                 }
 317
 318                 if ( substr( $server, 0, 1 ) === '/' ) {
 319                         // UNIX domain socket
 320                         // These are required by the redis extension to start with a slash, but
 321                         // we still need to set the port to a special value to make it work.
 322                         $host = $server;
 323                         $port = 0;
 324                 } else {
 325                         // TCP connection
 326                         $hostPort = IP::splitHostAndPort( $server );
 327                         if ( !$hostPort ) {
 328                                 throw new MWException( __CLASS__.": invalid configured server \"$server\"" );
 329                         }
 330                         list( $host, $port ) = $hostPort;
 331                         if ( $port === false ) {
 332                                 $port = 6379;
 333                         }
 334                 }
 335                 $conn = new Redis;
 336                 try {
 337                         if ( $this->persistent ) {
 338                                 $this->debug( "opening persistent connection to $host:$port" );
 339                                 $result = $conn->pconnect( $host, $port, $this->connectTimeout );
 340                         } else {
 341                                 $this->debug( "opening non-persistent connection to $host:$port" );
 342                                 $result = $conn->connect( $host, $port, $this->connectTimeout );
 343                         }
 344                         if ( !$result ) {
 345                                 $this->logError( "could not connect to server $server" );
 346                                 // Mark server down for 30s to avoid further timeouts
 347                                 $this->deadServers[$server] = time() + 30;
 348                                 return false;
 349                         }
 350                         if ( $this->password !== null ) {
 351                                 if ( !$conn->auth( $this->password ) ) {
 352                                         $this->logError( "authentication error connecting to $server" );
 353                                 }
 354                         }
 355                 } catch ( RedisException $e ) {
 356                         $this->deadServers[$server] = time() + 30;
 357                         wfDebugLog( 'redis', "Redis exception: " . $e->getMessage() . "\n" );
 358                         return false;
 359                 }
 360
 361                 $conn->setOption( Redis::OPT_SERIALIZER, Redis::SERIALIZER_PHP );
 362                 $this->conns[$server] = $conn;
 363                 return $conn;
 364         }
 365
 366         /**
 367          * Log a fatal error
 368          */
 369         protected function logError( $msg ) {
 370                 wfDebugLog( 'redis', "Redis error: $msg\n" );
 371         }
 372
 373         /**
 374          * The redis extension throws an exception in response to various read, write
 375          * and protocol errors. Sometimes it also closes the connection, sometimes
 376          * not. The safest response for us is to explicitly destroy the connection
 377          * object and let it be reopened during the next request.
 378          */
 379         protected function handleException( $server, $e ) {
 380                 wfDebugLog( 'redis', "Redis exception on server $server: " . $e->getMessage() . "\n" );
 381                 unset( $this->conns[$server] );
 382         }
 383
 384         /**
 385          * Send information about a single request to the debug log
 386          */
 387         public function logRequest( $method, $key, $server, $result ) {
 388                 $this->debug( "$method $key on $server: " .
 389                         ( $result === false ? "failure" : "success" ) );
 390         }
 391 }
 392