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                 $this->lockServers = $config['lockServers'];
  54                 // Sanitize srvsByBucket config to prevent PHP errors
  55                 $this->srvsByBucket = array_filter( $config['srvsByBucket'], 'is_array' );
  56                 $this->srvsByBucket = array_values( $this->srvsByBucket ); // consecutive
  57
  58                 if ( isset( $config['connTimeout'] ) ) {
  59                         $this->connTimeout = $config['connTimeout'];
  60                 } else {
  61                         $this->connTimeout = 3; // use some sane amount
  62                 }
  63
  64                 $this->session = '';
  65                 for ( $i = 0; $i < 5; $i++ ) {
  66                         $this->session .= mt_rand( 0, 2147483647 );
  67                 }
  68                 $this->session = wfBaseConvert( sha1( $this->session ), 16, 36, 31 );
  69         }
  70
  71         protected function doLock( array $paths, $type ) {
  72                 $status = Status::newGood();
  73
  74                 $pathsToLock = array();
  75                 // Get locks that need to be acquired (buckets => locks)...
  76                 foreach ( $paths as $path ) {
  77                         if ( isset( $this->locksHeld[$path][$type] ) ) {
  78                                 ++$this->locksHeld[$path][$type];
  79                         } elseif ( isset( $this->locksHeld[$path][self::LOCK_EX] ) ) {
  80                                 $this->locksHeld[$path][$type] = 1;
  81                         } else {
  82                                 $bucket = $this->getBucketFromKey( $path );
  83                                 $pathsToLock[$bucket][] = $path;
  84                         }
  85                 }
  86
  87                 $lockedPaths = array(); // files locked in this attempt
  88                 // Attempt to acquire these locks...
  89                 foreach ( $pathsToLock as $bucket => $paths ) {
  90                         // Try to acquire the locks for this bucket
  91                         $res = $this->doLockingRequestAll( $bucket, $paths, $type );
  92                         if ( $res === 'cantacquire' ) {
  93                                 // Resources already locked by another process.
  94                                 // Abort and unlock everything we just locked.
  95                                 foreach ( $paths as $path ) {
  96                                         $status->fatal( 'lockmanager-fail-acquirelock', $path );
  97                                 }
  98                                 $status->merge( $this->doUnlock( $lockedPaths, $type ) );
  99                                 return $status;
 100                         } elseif ( $res !== true ) {
 101                                 // Couldn't contact any servers for this bucket.
 102                                 // Abort and unlock everything we just locked.
 103                                 foreach ( $paths as $path ) {
 104                                         $status->fatal( 'lockmanager-fail-acquirelock', $path );
 105                                 }
 106                                 $status->merge( $this->doUnlock( $lockedPaths, $type ) );
 107                                 return $status;
 108                         }
 109                         // Record these locks as active
 110                         foreach ( $paths as $path ) {
 111                                 $this->locksHeld[$path][$type] = 1; // locked
 112                         }
 113                         // Keep track of what locks were made in this attempt
 114                         $lockedPaths = array_merge( $lockedPaths, $paths );
 115                 }
 116
 117                 return $status;
 118         }
 119
 120         protected function doUnlock( array $paths, $type ) {
 121                 $status = Status::newGood();
 122
 123                 foreach ( $paths as $path ) {
 124                         if ( !isset( $this->locksHeld[$path] ) ) {
 125                                 $status->warning( 'lockmanager-notlocked', $path );
 126                         } elseif ( !isset( $this->locksHeld[$path][$type] ) ) {
 127                                 $status->warning( 'lockmanager-notlocked', $path );
 128                         } else {
 129                                 --$this->locksHeld[$path][$type];
 130                                 if ( $this->locksHeld[$path][$type] <= 0 ) {
 131                                         unset( $this->locksHeld[$path][$type] );
 132                                 }
 133                                 if ( !count( $this->locksHeld[$path] ) ) {
 134                                         unset( $this->locksHeld[$path] ); // no SH or EX locks left for key
 135                                 }
 136                         }
 137                 }
 138
 139                 // Reference count the locks held and release locks when zero
 140                 if ( !count( $this->locksHeld ) ) {
 141                         $status->merge( $this->releaseLocks() );
 142                 }
 143
 144                 return $status;
 145         }
 146
 147         /**
 148          * Get a connection to a lock server and acquire locks on $paths
 149          *
 150          * @param $lockSrv string
 151          * @param $paths Array
 152          * @param $type integer LockManager::LOCK_EX or LockManager::LOCK_SH
 153          * @return bool Resources able to be locked
 154          */
 155         protected function doLockingRequest( $lockSrv, array $paths, $type ) {
 156                 if ( $type == self::LOCK_SH ) { // reader locks
 157                         $type = 'SH';
 158                 } elseif ( $type == self::LOCK_EX ) { // writer locks
 159                         $type = 'EX';
 160                 } else {
 161                         return true; // ok...
 162                 }
 163
 164                 // Send out the command and get the response...
 165                 $keys = array_unique( array_map( 'LockManager::sha1Base36', $paths ) );
 166                 $response = $this->sendCommand( $lockSrv, 'ACQUIRE', $type, $keys );
 167
 168                 return ( $response === 'ACQUIRED' );
 169         }
 170
 171         /**
 172          * Send a command and get back the response
 173          *
 174          * @param $lockSrv string
 175          * @param $action string
 176          * @param $type string
 177          * @param $values Array
 178          * @return string|false
 179          */
 180         protected function sendCommand( $lockSrv, $action, $type, $values ) {
 181                 $conn = $this->getConnection( $lockSrv );
 182                 if ( !$conn ) {
 183                         return false; // no connection
 184                 }
 185                 $authKey = $this->lockServers[$lockSrv]['authKey'];
 186                 // Build of the command as a flat string...
 187                 $values = implode( '|', $values );
 188                 $key = sha1( $this->session . $action . $type . $values . $authKey );
 189                 // Send out the command...
 190                 if ( fwrite( $conn, "{$this->session}:$key:$action:$type:$values\n" ) === false ) {
 191                         return false;
 192                 }
 193                 // Get the response...
 194                 $response = fgets( $conn );
 195                 if ( $response === false ) {
 196                         return false;
 197                 }
 198                 return trim( $response );
 199         }
 200
 201         /**
 202          * Attempt to acquire locks with the peers for a bucket
 203          *
 204          * @param $bucket integer
 205          * @param $paths Array List of resource keys to lock
 206          * @param $type integer LockManager::LOCK_EX or LockManager::LOCK_SH
 207          * @return bool|string One of (true, 'cantacquire', 'srverrors')
 208          */
 209         protected function doLockingRequestAll( $bucket, array $paths, $type ) {
 210                 $yesVotes = 0; // locks made on trustable servers
 211                 $votesLeft = count( $this->srvsByBucket[$bucket] ); // remaining peers
 212                 $quorum = floor( $votesLeft/2 + 1 ); // simple majority
 213                 // Get votes for each peer, in order, until we have enough...
 214                 foreach ( $this->srvsByBucket[$bucket] as $lockSrv ) {
 215                         // Attempt to acquire the lock on this peer
 216                         if ( !$this->doLockingRequest( $lockSrv, $paths, $type ) ) {
 217                                 return 'cantacquire'; // vetoed; resource locked
 218                         }
 219                         ++$yesVotes; // success for this peer
 220                         if ( $yesVotes >= $quorum ) {
 221                                 return true; // lock obtained
 222                         }
 223                         --$votesLeft;
 224                         $votesNeeded = $quorum - $yesVotes;
 225                         if ( $votesNeeded > $votesLeft ) {
 226                                 // In "trust cache" mode we don't have to meet the quorum
 227                                 break; // short-circuit
 228                         }
 229                 }
 230                 // At this point, we must not have meet the quorum
 231                 return 'srverrors'; // not enough votes to ensure correctness
 232         }
 233
 234         /**
 235          * Get (or reuse) a connection to a lock server
 236          *
 237          * @param $lockSrv string
 238          * @return resource
 239          */
 240         protected function getConnection( $lockSrv ) {
 241                 if ( !isset( $this->conns[$lockSrv] ) ) {
 242                         $cfg = $this->lockServers[$lockSrv];
 243                         wfSuppressWarnings();
 244                         $errno = $errstr = '';
 245                         $conn = fsockopen( $cfg['host'], $cfg['port'], $errno, $errstr, $this->connTimeout );
 246                         wfRestoreWarnings();
 247                         if ( $conn === false ) {
 248                                 return null;
 249                         }
 250                         $sec = floor( $this->connTimeout );
 251                         $usec = floor( ( $this->connTimeout - floor( $this->connTimeout ) ) * 1e6 );
 252                         stream_set_timeout( $conn, $sec, $usec );
 253                         $this->conns[$lockSrv] = $conn;
 254                 }
 255                 return $this->conns[$lockSrv];
 256         }
 257
 258         /**
 259          * Release all locks that this session is holding
 260          *
 261          * @return Status
 262          */
 263         protected function releaseLocks() {
 264                 $status = Status::newGood();
 265                 foreach ( $this->conns as $lockSrv => $conn ) {
 266                         $response = $this->sendCommand( $lockSrv, 'RELEASE_ALL', '', array() );
 267                         if ( $response !== 'RELEASED_ALL' ) {
 268                                 $status->fatal( 'lockmanager-fail-svr-release', $lockSrv );
 269                         }
 270                 }
 271                 return $status;
 272         }
 273
 274         /**
 275          * Get the bucket for resource path.
 276          * This should avoid throwing any exceptions.
 277          *
 278          * @param $path string
 279          * @return integer
 280          */
 281         protected function getBucketFromKey( $path ) {
 282                 $prefix = substr( sha1( $path ), 0, 2 ); // first 2 hex chars (8 bits)
 283                 return intval( base_convert( $prefix, 16, 10 ) ) % count( $this->srvsByBucket );
 284         }
 285
 286         /**
 287          * Make sure remaining locks get cleared for sanity
 288          */
 289         function __destruct() {
 290                 $this->releaseLocks();
 291                 foreach ( $this->conns as $conn ) {
 292                         fclose( $conn );
 293                 }
 294         }
 295 }