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DrydockSlotLock.php
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Mon, Jul 15, 15:24

DrydockSlotLock.php
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<?php
/**
* Simple optimistic locks for Drydock resources and leases.
*
* Most blueprints only need very simple locks: for example, a host blueprint
* might not want to create multiple resources representing the same physical
* machine. These optimistic "slot locks" provide a flexible way to do this
* sort of simple locking.
*
* @task info Getting Lock Information
* @task lock Acquiring and Releasing Locks
*/
final class DrydockSlotLock extends DrydockDAO {
protected $ownerPHID;
protected $lockIndex;
protected $lockKey;
protected function getConfiguration() {
return array(
self::CONFIG_TIMESTAMPS => false,
self::CONFIG_COLUMN_SCHEMA => array(
'lockIndex' => 'bytes12',
'lockKey' => 'text',
),
self::CONFIG_KEY_SCHEMA => array(
'key_lock' => array(
'columns' => array('lockIndex'),
'unique' => true,
),
'key_owner' => array(
'columns' => array('ownerPHID'),
),
),
) + parent::getConfiguration();
}
/* -( Getting Lock Information )------------------------------------------- */
/**
* Load all locks held by a particular owner.
*
* @param phid Owner PHID.
* @return list<DrydockSlotLock> All held locks.
* @task info
*/
public static function loadLocks($owner_phid) {
return id(new DrydockSlotLock())->loadAllWhere(
'ownerPHID = %s',
$owner_phid);
}
/**
* Test if a lock is currently free.
*
* @param string Lock key to test.
* @return bool True if the lock is currently free.
* @task info
*/
public static function isLockFree($lock) {
return self::areLocksFree(array($lock));
}
/**
* Test if a list of locks are all currently free.
*
* @param list<string> List of lock keys to test.
* @return bool True if all locks are currently free.
* @task info
*/
public static function areLocksFree(array $locks) {
$lock_map = self::loadHeldLocks($locks);
return !$lock_map;
}
/**
* Load named locks.
*
* @param list<string> List of lock keys to load.
* @return list<DrydockSlotLock> List of held locks.
* @task info
*/
public static function loadHeldLocks(array $locks) {
if (!$locks) {
return array();
}
$table = new DrydockSlotLock();
$conn_r = $table->establishConnection('r');
$indexes = array();
foreach ($locks as $lock) {
$indexes[] = PhabricatorHash::digestForIndex($lock);
}
return id(new DrydockSlotLock())->loadAllWhere(
'lockIndex IN (%Ls)',
$indexes);
}
/* -( Acquiring and Releasing Locks )-------------------------------------- */
/**
* Acquire a set of slot locks.
*
* This method either acquires all the locks or throws an exception (usually
* because one or more locks are held).
*
* @param phid Lock owner PHID.
* @param list<string> List of locks to acquire.
* @return void
* @task locks
*/
public static function acquireLocks($owner_phid, array $locks) {
if (!$locks) {
return;
}
$table = new DrydockSlotLock();
$conn_w = $table->establishConnection('w');
$sql = array();
foreach ($locks as $lock) {
$sql[] = qsprintf(
$conn_w,
'(%s, %s, %s)',
$owner_phid,
PhabricatorHash::digestForIndex($lock),
$lock);
}
try {
queryfx(
$conn_w,
'INSERT INTO %T (ownerPHID, lockIndex, lockKey) VALUES %Q',
$table->getTableName(),
implode(', ', $sql));
} catch (AphrontDuplicateKeyQueryException $ex) {
// Try to improve the readability of the exception. We might miss on
// this query if the lock has already been released, but most of the
// time we should be able to figure out which locks are already held.
$held = self::loadHeldLocks($locks);
$held = mpull($held, 'getOwnerPHID', 'getLockKey');
throw new DrydockSlotLockException($held);
}
}
/**
* Release all locks held by an owner.
*
* @param phid Lock owner PHID.
* @return void
* @task locks
*/
public static function releaseLocks($owner_phid) {
$table = new DrydockSlotLock();
$conn_w = $table->establishConnection('w');
queryfx(
$conn_w,
'DELETE FROM %T WHERE ownerPHID = %s',
$table->getTableName(),
$owner_phid);
}
}

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