includes/libs/lockmanager/PostgreSqlLockManager.php

   1 <?php
   2
   3 use Wikimedia\Rdbms\DBError;
   4
   5 /**
   6  * PostgreSQL version of DBLockManager that supports shared locks.
   7  * All locks are non-blocking, which avoids deadlocks.
   8  *
   9  * @ingroup LockManager
  10  */
  11 class PostgreSqlLockManager extends DBLockManager {
  12         /** @var array Mapping of lock types to the type actually used */
  13         protected $lockTypeMap = [
  14                 self::LOCK_SH => self::LOCK_SH,
  15                 self::LOCK_UW => self::LOCK_SH,
  16                 self::LOCK_EX => self::LOCK_EX
  17         ];
  18
  19         protected function doGetLocksOnServer( $lockSrv, array $paths, $type ) {
  20                 $status = StatusValue::newGood();
  21                 if ( !count( $paths ) ) {
  22                         return $status; // nothing to lock
  23                 }
  24
  25                 $db = $this->getConnection( $lockSrv ); // checked in isServerUp()
  26                 $bigints = array_unique( array_map(
  27                         function ( $key ) {
  28                                 return Wikimedia\base_convert( substr( $key, 0, 15 ), 16, 10 );
  29                         },
  30                         array_map( [ $this, 'sha1Base16Absolute' ], $paths )
  31                 ) );
  32
  33                 // Try to acquire all the locks...
  34                 $fields = [];
  35                 foreach ( $bigints as $bigint ) {
  36                         $fields[] = ( $type == self::LOCK_SH )
  37                                 ? "pg_try_advisory_lock_shared({$db->addQuotes( $bigint )}) AS K$bigint"
  38                                 : "pg_try_advisory_lock({$db->addQuotes( $bigint )}) AS K$bigint";
  39                 }
  40                 $res = $db->query( 'SELECT ' . implode( ', ', $fields ), __METHOD__ );
  41                 $row = $res->fetchRow();
  42
  43                 if ( in_array( 'f', $row ) ) {
  44                         // Release any acquired locks if some could not be acquired...
  45                         $fields = [];
  46                         foreach ( $row as $kbigint => $ok ) {
  47                                 if ( $ok === 't' ) { // locked
  48                                         $bigint = substr( $kbigint, 1 ); // strip off the "K"
  49                                         $fields[] = ( $type == self::LOCK_SH )
  50                                                 ? "pg_advisory_unlock_shared({$db->addQuotes( $bigint )})"
  51                                                 : "pg_advisory_unlock({$db->addQuotes( $bigint )})";
  52                                 }
  53                         }
  54                         if ( count( $fields ) ) {
  55                                 $db->query( 'SELECT ' . implode( ', ', $fields ), __METHOD__ );
  56                         }
  57                         foreach ( $paths as $path ) {
  58                                 $status->fatal( 'lockmanager-fail-acquirelock', $path );
  59                         }
  60                 }
  61
  62                 return $status;
  63         }
  64
  65         /**
  66          * @see QuorumLockManager::releaseAllLocks()
  67          * @return StatusValue
  68          */
  69         protected function releaseAllLocks() {
  70                 $status = StatusValue::newGood();
  71
  72                 foreach ( $this->conns as $lockDb => $db ) {
  73                         try {
  74                                 $db->query( "SELECT pg_advisory_unlock_all()", __METHOD__ );
  75                         } catch ( DBError $e ) {
  76                                 $status->fatal( 'lockmanager-fail-db-release', $lockDb );
  77                         }
  78                 }
  79
  80                 return $status;
  81         }
  82 }