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  * @phan-file-suppress PhanUndeclaredConstant Phan doesn't read constants in LockManager
  11  *   when accessed via self::
  12  */
  13 class PostgreSqlLockManager extends DBLockManager {
  14         /** @var array Mapping of lock types to the type actually used */
  15         protected $lockTypeMap = [
  16                 self::LOCK_SH => self::LOCK_SH,
  17                 self::LOCK_UW => self::LOCK_SH,
  18                 self::LOCK_EX => self::LOCK_EX
  19         ];
  20
  21         protected function doGetLocksOnServer( $lockSrv, array $paths, $type ) {
  22                 $status = StatusValue::newGood();
  23                 if ( $paths === [] ) {
  24                         return $status; // nothing to lock
  25                 }
  26
  27                 $db = $this->getConnection( $lockSrv ); // checked in isServerUp()
  28                 $bigints = array_unique( array_map(
  29                         function ( $key ) {
  30                                 return Wikimedia\base_convert( substr( $key, 0, 15 ), 16, 10 );
  31                         },
  32                         array_map( [ $this, 'sha1Base16Absolute' ], $paths )
  33                 ) );
  34
  35                 // Try to acquire all the locks...
  36                 $fields = [];
  37                 foreach ( $bigints as $bigint ) {
  38                         $fields[] = ( $type == self::LOCK_SH )
  39                                 ? "pg_try_advisory_lock_shared({$db->addQuotes( $bigint )}) AS K$bigint"
  40                                 : "pg_try_advisory_lock({$db->addQuotes( $bigint )}) AS K$bigint";
  41                 }
  42                 $res = $db->query( 'SELECT ' . implode( ', ', $fields ), __METHOD__ );
  43                 $row = $res->fetchRow();
  44
  45                 if ( in_array( 'f', $row ) ) {
  46                         // Release any acquired locks if some could not be acquired...
  47                         $fields = [];
  48                         foreach ( $row as $kbigint => $ok ) {
  49                                 if ( $ok === 't' ) { // locked
  50                                         $bigint = substr( $kbigint, 1 ); // strip off the "K"
  51                                         $fields[] = ( $type == self::LOCK_SH )
  52                                                 ? "pg_advisory_unlock_shared({$db->addQuotes( $bigint )})"
  53                                                 : "pg_advisory_unlock({$db->addQuotes( $bigint )})";
  54                                 }
  55                         }
  56                         if ( count( $fields ) ) {
  57                                 $db->query( 'SELECT ' . implode( ', ', $fields ), __METHOD__ );
  58                         }
  59                         foreach ( $paths as $path ) {
  60                                 $status->fatal( 'lockmanager-fail-acquirelock', $path );
  61                         }
  62                 }
  63
  64                 return $status;
  65         }
  66
  67         /**
  68          * @see QuorumLockManager::releaseAllLocks()
  69          * @return StatusValue
  70          */
  71         protected function releaseAllLocks() {
  72                 $status = StatusValue::newGood();
  73
  74                 foreach ( $this->conns as $lockDb => $db ) {
  75                         try {
  76                                 $db->query( "SELECT pg_advisory_unlock_all()", __METHOD__ );
  77                         } catch ( DBError $e ) {
  78                                 $status->fatal( 'lockmanager-fail-db-release', $lockDb );
  79                         }
  80                 }
  81
  82                 return $status;
  83         }
  84 }