3 use Wikimedia\Rdbms\IDatabase
;
4 use Wikimedia\Rdbms\DBError
;
7 * MySQL version of DBLockManager that supports shared locks.
9 * Do NOT use this on connection handles that are also being used for anything
10 * else as the transaction isolation will be wrong and all the other changes will
11 * get rolled back when the locks release!
13 * All lock servers must have the innodb table defined in maintenance/locking/filelocks.sql.
14 * All locks are non-blocking, which avoids deadlocks.
16 * @ingroup LockManager
18 class MySqlLockManager
extends DBLockManager
{
19 /** @var array Mapping of lock types to the type actually used */
20 protected $lockTypeMap = [
21 self
::LOCK_SH
=> self
::LOCK_SH
,
22 self
::LOCK_UW
=> self
::LOCK_SH
,
23 self
::LOCK_EX
=> self
::LOCK_EX
26 public function __construct( array $config ) {
27 parent
::__construct( $config );
29 $this->session
= substr( $this->session
, 0, 31 ); // fit to field
32 protected function initConnection( $lockDb, IDatabase
$db ) {
33 # Let this transaction see lock rows from other transactions
34 $db->query( "SET SESSION TRANSACTION ISOLATION LEVEL READ UNCOMMITTED;" );
35 # Do everything in a transaction as it all gets rolled back eventually
36 $db->startAtomic( __CLASS__
);
40 * Get a connection to a lock DB and acquire locks on $paths.
41 * This does not use GET_LOCK() per https://bugs.mysql.com/bug.php?id=1118.
43 * @see DBLockManager::getLocksOnServer()
44 * @param string $lockSrv
49 protected function doGetLocksOnServer( $lockSrv, array $paths, $type ) {
50 $status = StatusValue
::newGood();
52 $db = $this->getConnection( $lockSrv ); // checked in isServerUp()
54 $keys = []; // list of hash keys for the paths
55 $data = []; // list of rows to insert
56 $checkEXKeys = []; // list of hash keys that this has no EX lock on
57 # Build up values for INSERT clause
58 foreach ( $paths as $path ) {
59 $key = $this->sha1Base36Absolute( $path );
61 $data[] = [ 'fls_key' => $key, 'fls_session' => $this->session
];
62 if ( !isset( $this->locksHeld
[$path][self
::LOCK_EX
] ) ) {
63 $checkEXKeys[] = $key; // this has no EX lock on $key itself
67 # Block new writers (both EX and SH locks leave entries here)...
68 $db->insert( 'filelocks_shared', $data, __METHOD__
, [ 'IGNORE' ] );
69 # Actually do the locking queries...
70 if ( $type == self
::LOCK_SH
) { // reader locks
71 # Bail if there are any existing writers...
72 if ( count( $checkEXKeys ) ) {
73 $blocked = $db->selectField(
74 'filelocks_exclusive',
76 [ 'fle_key' => $checkEXKeys ],
82 # Other prospective writers that haven't yet updated filelocks_exclusive
83 # will recheck filelocks_shared after doing so and bail due to this entry.
84 } else { // writer locks
85 $encSession = $db->addQuotes( $this->session
);
86 # Bail if there are any existing writers...
87 # This may detect readers, but the safe check for them is below.
88 # Note: if two writers come at the same time, both bail :)
89 $blocked = $db->selectField(
92 [ 'fls_key' => $keys, "fls_session != $encSession" ],
96 # Build up values for INSERT clause
98 foreach ( $keys as $key ) {
99 $data[] = [ 'fle_key' => $key ];
101 # Block new readers/writers...
102 $db->insert( 'filelocks_exclusive', $data, __METHOD__
);
103 # Bail if there are any existing readers...
104 $blocked = $db->selectField(
107 [ 'fls_key' => $keys, "fls_session != $encSession" ],
114 foreach ( $paths as $path ) {
115 $status->fatal( 'lockmanager-fail-acquirelock', $path );
123 * @see QuorumLockManager::releaseAllLocks()
124 * @return StatusValue
126 protected function releaseAllLocks() {
127 $status = StatusValue
::newGood();
129 foreach ( $this->conns
as $lockDb => $db ) {
130 if ( $db->trxLevel() ) { // in transaction
132 $db->rollback( __METHOD__
); // finish transaction and kill any rows
133 } catch ( DBError
$e ) {
134 $status->fatal( 'lockmanager-fail-db-release', $lockDb );