includes/filerepo/backend/lockmanager/LSLockManager.php

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