includes/filerepo/backend/lockmanager/LSLockManager.php

   1 <?php
   2 /**
   3  * Version of LockManager based on using lock daemon servers.
   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  * @ingroup LockManager
  22  */
  23
  24 /**
  25  * Manage locks using a lock daemon server.
  26  *
  27  * Version of LockManager based on using lock daemon servers.
  28  * This is meant for multi-wiki systems that may share files.
  29  * All locks are non-blocking, which avoids deadlocks.
  30  *
  31  * All lock requests for a resource, identified by a hash string, will map
  32  * to one bucket. Each bucket maps to one or several peer servers, each
  33  * running LockServerDaemon.php, listening on a designated TCP port.
  34  * A majority of peers must agree for a lock to be acquired.
  35  *
  36  * @ingroup LockManager
  37  * @since 1.19
  38  */
  39 class LSLockManager extends LockManager {
  40         /** @var Array Mapping of lock types to the type actually used */
  41         protected $lockTypeMap = array(
  42                 self::LOCK_SH => self::LOCK_SH,
  43                 self::LOCK_UW => self::LOCK_SH,
  44                 self::LOCK_EX => self::LOCK_EX
  45         );
  46
  47         /** @var Array Map of server names to server config */
  48         protected $lockServers; // (server name => server config array)
  49         /** @var Array Map of bucket indexes to peer server lists */
  50         protected $srvsByBucket; // (bucket index => (lsrv1, lsrv2, ...))
  51
  52         /** @var Array Map Server connections (server name => resource) */
  53         protected $conns = array();
  54
  55         protected $connTimeout; // float number of seconds
  56         protected $session = ''; // random SHA-1 string
  57
  58         /**
  59          * Construct a new instance from configuration.
  60          *
  61          * $config paramaters include:
  62          *     'lockServers'  : Associative array of server names to configuration.
  63          *                      Configuration is an associative array that includes:
  64          *                      'host'    - IP address/hostname
  65          *                      'port'    - TCP port
  66          *                      'authKey' - Secret string the lock server uses
  67          *     'srvsByBucket' : Array of 1-16 consecutive integer keys, starting from 0,
  68          *                      each having an odd-numbered list of server names (peers) as values.
  69          *     'connTimeout'  : Lock server connection attempt timeout. [optional]
  70          *
  71          * @param Array $config
  72          */
  73         public function __construct( array $config ) {
  74                 parent::__construct( $config );
  75
  76                 $this->lockServers = $config['lockServers'];
  77                 // Sanitize srvsByBucket config to prevent PHP errors
  78                 $this->srvsByBucket = array_filter( $config['srvsByBucket'], 'is_array' );
  79                 $this->srvsByBucket = array_values( $this->srvsByBucket ); // consecutive
  80
  81                 if ( isset( $config['connTimeout'] ) ) {
  82                         $this->connTimeout = $config['connTimeout'];
  83                 } else {
  84                         $this->connTimeout = 3; // use some sane amount
  85                 }
  86
  87                 $this->session = '';
  88                 for ( $i = 0; $i < 5; $i++ ) {
  89                         $this->session .= mt_rand( 0, 2147483647 );
  90                 }
  91                 $this->session = wfBaseConvert( sha1( $this->session ), 16, 36, 31 );
  92         }
  93
  94         /**
  95          * @see LockManager::doLock()
  96          * @return Status
  97          */
  98         protected function doLock( array $paths, $type ) {
  99                 $status = Status::newGood();
 100
 101                 $pathsToLock = array();
 102                 // Get locks that need to be acquired (buckets => locks)...
 103                 foreach ( $paths as $path ) {
 104                         if ( isset( $this->locksHeld[$path][$type] ) ) {
 105                                 ++$this->locksHeld[$path][$type];
 106                         } elseif ( isset( $this->locksHeld[$path][self::LOCK_EX] ) ) {
 107                                 $this->locksHeld[$path][$type] = 1;
 108                         } else {
 109                                 $bucket = $this->getBucketFromKey( $path );
 110                                 $pathsToLock[$bucket][] = $path;
 111                         }
 112                 }
 113
 114                 $lockedPaths = array(); // files locked in this attempt
 115                 // Attempt to acquire these locks...
 116                 foreach ( $pathsToLock as $bucket => $paths ) {
 117                         // Try to acquire the locks for this bucket
 118                         $res = $this->doLockingRequestAll( $bucket, $paths, $type );
 119                         if ( $res === 'cantacquire' ) {
 120                                 // Resources already locked by another process.
 121                                 // Abort and unlock everything we just locked.
 122                                 foreach ( $paths as $path ) {
 123                                         $status->fatal( 'lockmanager-fail-acquirelock', $path );
 124                                 }
 125                                 $status->merge( $this->doUnlock( $lockedPaths, $type ) );
 126                                 return $status;
 127                         } elseif ( $res !== true ) {
 128                                 // Couldn't contact any servers for this bucket.
 129                                 // Abort and unlock everything we just locked.
 130                                 foreach ( $paths as $path ) {
 131                                         $status->fatal( 'lockmanager-fail-acquirelock', $path );
 132                                 }
 133                                 $status->merge( $this->doUnlock( $lockedPaths, $type ) );
 134                                 return $status;
 135                         }
 136                         // Record these locks as active
 137                         foreach ( $paths as $path ) {
 138                                 $this->locksHeld[$path][$type] = 1; // locked
 139                         }
 140                         // Keep track of what locks were made in this attempt
 141                         $lockedPaths = array_merge( $lockedPaths, $paths );
 142                 }
 143
 144                 return $status;
 145         }
 146
 147         /**
 148          * @see LockManager::doUnlock()
 149          * @return Status
 150          */
 151         protected function doUnlock( array $paths, $type ) {
 152                 $status = Status::newGood();
 153
 154                 foreach ( $paths as $path ) {
 155                         if ( !isset( $this->locksHeld[$path] ) ) {
 156                                 $status->warning( 'lockmanager-notlocked', $path );
 157                         } elseif ( !isset( $this->locksHeld[$path][$type] ) ) {
 158                                 $status->warning( 'lockmanager-notlocked', $path );
 159                         } else {
 160                                 --$this->locksHeld[$path][$type];
 161                                 if ( $this->locksHeld[$path][$type] <= 0 ) {
 162                                         unset( $this->locksHeld[$path][$type] );
 163                                 }
 164                                 if ( !count( $this->locksHeld[$path] ) ) {
 165                                         unset( $this->locksHeld[$path] ); // no SH or EX locks left for key
 166                                 }
 167                         }
 168                 }
 169
 170                 // Reference count the locks held and release locks when zero
 171                 if ( !count( $this->locksHeld ) ) {
 172                         $status->merge( $this->releaseLocks() );
 173                 }
 174
 175                 return $status;
 176         }
 177
 178         /**
 179          * Get a connection to a lock server and acquire locks on $paths
 180          *
 181          * @param $lockSrv string
 182          * @param $paths Array
 183          * @param $type integer LockManager::LOCK_EX or LockManager::LOCK_SH
 184          * @return bool Resources able to be locked
 185          */
 186         protected function doLockingRequest( $lockSrv, array $paths, $type ) {
 187                 if ( $type == self::LOCK_SH ) { // reader locks
 188                         $type = 'SH';
 189                 } elseif ( $type == self::LOCK_EX ) { // writer locks
 190                         $type = 'EX';
 191                 } else {
 192                         return true; // ok...
 193                 }
 194
 195                 // Send out the command and get the response...
 196                 $keys = array_unique( array_map( 'LockManager::sha1Base36', $paths ) );
 197                 $response = $this->sendCommand( $lockSrv, 'ACQUIRE', $type, $keys );
 198
 199                 return ( $response === 'ACQUIRED' );
 200         }
 201
 202         /**
 203          * Send a command and get back the response
 204          *
 205          * @param $lockSrv string
 206          * @param $action string
 207          * @param $type string
 208          * @param $values Array
 209          * @return string|bool
 210          */
 211         protected function sendCommand( $lockSrv, $action, $type, $values ) {
 212                 $conn = $this->getConnection( $lockSrv );
 213                 if ( !$conn ) {
 214                         return false; // no connection
 215                 }
 216                 $authKey = $this->lockServers[$lockSrv]['authKey'];
 217                 // Build of the command as a flat string...
 218                 $values = implode( '|', $values );
 219                 $key = sha1( $this->session . $action . $type . $values . $authKey );
 220                 // Send out the command...
 221                 if ( fwrite( $conn, "{$this->session}:$key:$action:$type:$values\n" ) === false ) {
 222                         return false;
 223                 }
 224                 // Get the response...
 225                 $response = fgets( $conn );
 226                 if ( $response === false ) {
 227                         return false;
 228                 }
 229                 return trim( $response );
 230         }
 231
 232         /**
 233          * Attempt to acquire locks with the peers for a bucket
 234          *
 235          * @param $bucket integer
 236          * @param $paths Array List of resource keys to lock
 237          * @param $type integer LockManager::LOCK_EX or LockManager::LOCK_SH
 238          * @return bool|string One of (true, 'cantacquire', 'srverrors')
 239          */
 240         protected function doLockingRequestAll( $bucket, array $paths, $type ) {
 241                 $yesVotes = 0; // locks made on trustable servers
 242                 $votesLeft = count( $this->srvsByBucket[$bucket] ); // remaining peers
 243                 $quorum = floor( $votesLeft/2 + 1 ); // simple majority
 244                 // Get votes for each peer, in order, until we have enough...
 245                 foreach ( $this->srvsByBucket[$bucket] as $lockSrv ) {
 246                         // Attempt to acquire the lock on this peer
 247                         if ( !$this->doLockingRequest( $lockSrv, $paths, $type ) ) {
 248                                 return 'cantacquire'; // vetoed; resource locked
 249                         }
 250                         ++$yesVotes; // success for this peer
 251                         if ( $yesVotes >= $quorum ) {
 252                                 return true; // lock obtained
 253                         }
 254                         --$votesLeft;
 255                         $votesNeeded = $quorum - $yesVotes;
 256                         if ( $votesNeeded > $votesLeft ) {
 257                                 // In "trust cache" mode we don't have to meet the quorum
 258                                 break; // short-circuit
 259                         }
 260                 }
 261                 // At this point, we must not have meet the quorum
 262                 return 'srverrors'; // not enough votes to ensure correctness
 263         }
 264
 265         /**
 266          * Get (or reuse) a connection to a lock server
 267          *
 268          * @param $lockSrv string
 269          * @return resource
 270          */
 271         protected function getConnection( $lockSrv ) {
 272                 if ( !isset( $this->conns[$lockSrv] ) ) {
 273                         $cfg = $this->lockServers[$lockSrv];
 274                         wfSuppressWarnings();
 275                         $errno = $errstr = '';
 276                         $conn = fsockopen( $cfg['host'], $cfg['port'], $errno, $errstr, $this->connTimeout );
 277                         wfRestoreWarnings();
 278                         if ( $conn === false ) {
 279                                 return null;
 280                         }
 281                         $sec = floor( $this->connTimeout );
 282                         $usec = floor( ( $this->connTimeout - floor( $this->connTimeout ) ) * 1e6 );
 283                         stream_set_timeout( $conn, $sec, $usec );
 284                         $this->conns[$lockSrv] = $conn;
 285                 }
 286                 return $this->conns[$lockSrv];
 287         }
 288
 289         /**
 290          * Release all locks that this session is holding
 291          *
 292          * @return Status
 293          */
 294         protected function releaseLocks() {
 295                 $status = Status::newGood();
 296                 foreach ( $this->conns as $lockSrv => $conn ) {
 297                         $response = $this->sendCommand( $lockSrv, 'RELEASE_ALL', '', array() );
 298                         if ( $response !== 'RELEASED_ALL' ) {
 299                                 $status->fatal( 'lockmanager-fail-svr-release', $lockSrv );
 300                         }
 301                 }
 302                 return $status;
 303         }
 304
 305         /**
 306          * Get the bucket for resource path.
 307          * This should avoid throwing any exceptions.
 308          *
 309          * @param $path string
 310          * @return integer
 311          */
 312         protected function getBucketFromKey( $path ) {
 313                 $prefix = substr( sha1( $path ), 0, 2 ); // first 2 hex chars (8 bits)
 314                 return intval( base_convert( $prefix, 16, 10 ) ) % count( $this->srvsByBucket );
 315         }
 316
 317         /**
 318          * Make sure remaining locks get cleared for sanity
 319          */
 320         function __destruct() {
 321                 $this->releaseLocks();
 322                 foreach ( $this->conns as $conn ) {
 323                         fclose( $conn );
 324                 }
 325         }
 326 }