includes/filerepo/backend/lockmanager/LSLockManager.php

   1 <?php
   2
   3 /**
   4  * Manage locks using a lock daemon server.
   5  *
   6  * Version of LockManager based on using lock daemon servers.
   7  * This is meant for multi-wiki systems that may share files.
   8  * All locks are non-blocking, which avoids deadlocks.
   9  *
  10  * All lock requests for a resource, identified by a hash string, will map
  11  * to one bucket. Each bucket maps to one or several peer servers, each
  12  * running LockServerDaemon.php, listening on a designated TCP port.
  13  * A majority of peers must agree for a lock to be acquired.
  14  *
  15  * @ingroup LockManager
  16  * @since 1.19
  17  */
  18 class LSLockManager extends LockManager {
  19         /** @var Array Mapping of lock types to the type actually used */
  20         protected $lockTypeMap = array(
  21                 self::LOCK_SH => self::LOCK_SH,
  22                 self::LOCK_UW => self::LOCK_SH,
  23                 self::LOCK_EX => self::LOCK_EX
  24         );
  25
  26         /** @var Array Map of server names to server config */
  27         protected $lockServers; // (server name => server config array)
  28         /** @var Array Map of bucket indexes to peer server lists */
  29         protected $srvsByBucket; // (bucket index => (lsrv1, lsrv2, ...))
  30
  31         /** @var Array Map Server connections (server name => resource) */
  32         protected $conns = array();
  33
  34         protected $connTimeout; // float number of seconds
  35         protected $session = ''; // random SHA-1 string
  36
  37         /**
  38          * Construct a new instance from configuration.
  39          *
  40          * $config paramaters include:
  41          *     'lockServers'  : Associative array of server names to configuration.
  42          *                      Configuration is an associative array that includes:
  43          *                      'host'    - IP address/hostname
  44          *                      'port'    - TCP port
  45          *                      'authKey' - Secret string the lock server uses
  46          *     'srvsByBucket' : Array of 1-16 consecutive integer keys, starting from 0,
  47          *                      each having an odd-numbered list of server names (peers) as values.
  48          *     'connTimeout'  : Lock server connection attempt timeout. [optional]
  49          *
  50          * @param Array $config
  51          */
  52         public function __construct( array $config ) {
  53                 parent::__construct( $config );
  54
  55                 $this->lockServers = $config['lockServers'];
  56                 // Sanitize srvsByBucket config to prevent PHP errors
  57                 $this->srvsByBucket = array_filter( $config['srvsByBucket'], 'is_array' );
  58                 $this->srvsByBucket = array_values( $this->srvsByBucket ); // consecutive
  59
  60                 if ( isset( $config['connTimeout'] ) ) {
  61                         $this->connTimeout = $config['connTimeout'];
  62                 } else {
  63                         $this->connTimeout = 3; // use some sane amount
  64                 }
  65
  66                 $this->session = '';
  67                 for ( $i = 0; $i < 5; $i++ ) {
  68                         $this->session .= mt_rand( 0, 2147483647 );
  69                 }
  70                 $this->session = wfBaseConvert( sha1( $this->session ), 16, 36, 31 );
  71         }
  72
  73         /**
  74          * @see LockManager::doLock()
  75          * @return Status
  76          */
  77         protected function doLock( array $paths, $type ) {
  78                 $status = Status::newGood();
  79
  80                 $pathsToLock = array();
  81                 // Get locks that need to be acquired (buckets => locks)...
  82                 foreach ( $paths as $path ) {
  83                         if ( isset( $this->locksHeld[$path][$type] ) ) {
  84                                 ++$this->locksHeld[$path][$type];
  85                         } elseif ( isset( $this->locksHeld[$path][self::LOCK_EX] ) ) {
  86                                 $this->locksHeld[$path][$type] = 1;
  87                         } else {
  88                                 $bucket = $this->getBucketFromKey( $path );
  89                                 $pathsToLock[$bucket][] = $path;
  90                         }
  91                 }
  92
  93                 $lockedPaths = array(); // files locked in this attempt
  94                 // Attempt to acquire these locks...
  95                 foreach ( $pathsToLock as $bucket => $paths ) {
  96                         // Try to acquire the locks for this bucket
  97                         $res = $this->doLockingRequestAll( $bucket, $paths, $type );
  98                         if ( $res === 'cantacquire' ) {
  99                                 // Resources already locked by another process.
 100                                 // Abort and unlock everything we just locked.
 101                                 foreach ( $paths as $path ) {
 102                                         $status->fatal( 'lockmanager-fail-acquirelock', $path );
 103                                 }
 104                                 $status->merge( $this->doUnlock( $lockedPaths, $type ) );
 105                                 return $status;
 106                         } elseif ( $res !== true ) {
 107                                 // Couldn't contact any servers for this bucket.
 108                                 // Abort and unlock everything we just locked.
 109                                 foreach ( $paths as $path ) {
 110                                         $status->fatal( 'lockmanager-fail-acquirelock', $path );
 111                                 }
 112                                 $status->merge( $this->doUnlock( $lockedPaths, $type ) );
 113                                 return $status;
 114                         }
 115                         // Record these locks as active
 116                         foreach ( $paths as $path ) {
 117                                 $this->locksHeld[$path][$type] = 1; // locked
 118                         }
 119                         // Keep track of what locks were made in this attempt
 120                         $lockedPaths = array_merge( $lockedPaths, $paths );
 121                 }
 122
 123                 return $status;
 124         }
 125
 126         /**
 127          * @see LockManager::doUnlock()
 128          * @return Status
 129          */
 130         protected function doUnlock( array $paths, $type ) {
 131                 $status = Status::newGood();
 132
 133                 foreach ( $paths as $path ) {
 134                         if ( !isset( $this->locksHeld[$path] ) ) {
 135                                 $status->warning( 'lockmanager-notlocked', $path );
 136                         } elseif ( !isset( $this->locksHeld[$path][$type] ) ) {
 137                                 $status->warning( 'lockmanager-notlocked', $path );
 138                         } else {
 139                                 --$this->locksHeld[$path][$type];
 140                                 if ( $this->locksHeld[$path][$type] <= 0 ) {
 141                                         unset( $this->locksHeld[$path][$type] );
 142                                 }
 143                                 if ( !count( $this->locksHeld[$path] ) ) {
 144                                         unset( $this->locksHeld[$path] ); // no SH or EX locks left for key
 145                                 }
 146                         }
 147                 }
 148
 149                 // Reference count the locks held and release locks when zero
 150                 if ( !count( $this->locksHeld ) ) {
 151                         $status->merge( $this->releaseLocks() );
 152                 }
 153
 154                 return $status;
 155         }
 156
 157         /**
 158          * Get a connection to a lock server and acquire locks on $paths
 159          *
 160          * @param $lockSrv string
 161          * @param $paths Array
 162          * @param $type integer LockManager::LOCK_EX or LockManager::LOCK_SH
 163          * @return bool Resources able to be locked
 164          */
 165         protected function doLockingRequest( $lockSrv, array $paths, $type ) {
 166                 if ( $type == self::LOCK_SH ) { // reader locks
 167                         $type = 'SH';
 168                 } elseif ( $type == self::LOCK_EX ) { // writer locks
 169                         $type = 'EX';
 170                 } else {
 171                         return true; // ok...
 172                 }
 173
 174                 // Send out the command and get the response...
 175                 $keys = array_unique( array_map( 'LockManager::sha1Base36', $paths ) );
 176                 $response = $this->sendCommand( $lockSrv, 'ACQUIRE', $type, $keys );
 177
 178                 return ( $response === 'ACQUIRED' );
 179         }
 180
 181         /**
 182          * Send a command and get back the response
 183          *
 184          * @param $lockSrv string
 185          * @param $action string
 186          * @param $type string
 187          * @param $values Array
 188          * @return string|bool
 189          */
 190         protected function sendCommand( $lockSrv, $action, $type, $values ) {
 191                 $conn = $this->getConnection( $lockSrv );
 192                 if ( !$conn ) {
 193                         return false; // no connection
 194                 }
 195                 $authKey = $this->lockServers[$lockSrv]['authKey'];
 196                 // Build of the command as a flat string...
 197                 $values = implode( '|', $values );
 198                 $key = sha1( $this->session . $action . $type . $values . $authKey );
 199                 // Send out the command...
 200                 if ( fwrite( $conn, "{$this->session}:$key:$action:$type:$values\n" ) === false ) {
 201                         return false;
 202                 }
 203                 // Get the response...
 204                 $response = fgets( $conn );
 205                 if ( $response === false ) {
 206                         return false;
 207                 }
 208                 return trim( $response );
 209         }
 210
 211         /**
 212          * Attempt to acquire locks with the peers for a bucket
 213          *
 214          * @param $bucket integer
 215          * @param $paths Array List of resource keys to lock
 216          * @param $type integer LockManager::LOCK_EX or LockManager::LOCK_SH
 217          * @return bool|string One of (true, 'cantacquire', 'srverrors')
 218          */
 219         protected function doLockingRequestAll( $bucket, array $paths, $type ) {
 220                 $yesVotes = 0; // locks made on trustable servers
 221                 $votesLeft = count( $this->srvsByBucket[$bucket] ); // remaining peers
 222                 $quorum = floor( $votesLeft/2 + 1 ); // simple majority
 223                 // Get votes for each peer, in order, until we have enough...
 224                 foreach ( $this->srvsByBucket[$bucket] as $lockSrv ) {
 225                         // Attempt to acquire the lock on this peer
 226                         if ( !$this->doLockingRequest( $lockSrv, $paths, $type ) ) {
 227                                 return 'cantacquire'; // vetoed; resource locked
 228                         }
 229                         ++$yesVotes; // success for this peer
 230                         if ( $yesVotes >= $quorum ) {
 231                                 return true; // lock obtained
 232                         }
 233                         --$votesLeft;
 234                         $votesNeeded = $quorum - $yesVotes;
 235                         if ( $votesNeeded > $votesLeft ) {
 236                                 // In "trust cache" mode we don't have to meet the quorum
 237                                 break; // short-circuit
 238                         }
 239                 }
 240                 // At this point, we must not have meet the quorum
 241                 return 'srverrors'; // not enough votes to ensure correctness
 242         }
 243
 244         /**
 245          * Get (or reuse) a connection to a lock server
 246          *
 247          * @param $lockSrv string
 248          * @return resource
 249          */
 250         protected function getConnection( $lockSrv ) {
 251                 if ( !isset( $this->conns[$lockSrv] ) ) {
 252                         $cfg = $this->lockServers[$lockSrv];
 253                         wfSuppressWarnings();
 254                         $errno = $errstr = '';
 255                         $conn = fsockopen( $cfg['host'], $cfg['port'], $errno, $errstr, $this->connTimeout );
 256                         wfRestoreWarnings();
 257                         if ( $conn === false ) {
 258                                 return null;
 259                         }
 260                         $sec = floor( $this->connTimeout );
 261                         $usec = floor( ( $this->connTimeout - floor( $this->connTimeout ) ) * 1e6 );
 262                         stream_set_timeout( $conn, $sec, $usec );
 263                         $this->conns[$lockSrv] = $conn;
 264                 }
 265                 return $this->conns[$lockSrv];
 266         }
 267
 268         /**
 269          * Release all locks that this session is holding
 270          *
 271          * @return Status
 272          */
 273         protected function releaseLocks() {
 274                 $status = Status::newGood();
 275                 foreach ( $this->conns as $lockSrv => $conn ) {
 276                         $response = $this->sendCommand( $lockSrv, 'RELEASE_ALL', '', array() );
 277                         if ( $response !== 'RELEASED_ALL' ) {
 278                                 $status->fatal( 'lockmanager-fail-svr-release', $lockSrv );
 279                         }
 280                 }
 281                 return $status;
 282         }
 283
 284         /**
 285          * Get the bucket for resource path.
 286          * This should avoid throwing any exceptions.
 287          *
 288          * @param $path string
 289          * @return integer
 290          */
 291         protected function getBucketFromKey( $path ) {
 292                 $prefix = substr( sha1( $path ), 0, 2 ); // first 2 hex chars (8 bits)
 293                 return intval( base_convert( $prefix, 16, 10 ) ) % count( $this->srvsByBucket );
 294         }
 295
 296         /**
 297          * Make sure remaining locks get cleared for sanity
 298          */
 299         function __destruct() {
 300                 $this->releaseLocks();
 301                 foreach ( $this->conns as $conn ) {
 302                         fclose( $conn );
 303                 }
 304         }
 305 }