Package org.apache.derby.impl.services.locks

Interface LockTable

  • All Known Implementing Classes:
    ConcurrentLockSet
    interface LockTable
    Interface which must be implemented by lock table classes.

    • Method Detail

      • lockObject

        Lock lockObject​(CompatibilitySpace compatibilitySpace,
                Lockable ref,
                java.lang.Object qualifier,
                int timeout)
         throws StandardException
        Lock an object.
        Parameters:
        compatibilitySpace - the compatibility space
        ref - the object to lock
        qualifier - qualifier of the lock
        timeout - maximum time to wait in milliseconds (C_LockFactory.NO_WAIT means don't wait)
        Returns:
        a reference to the lock, or null if the lock couldn't be obtained immediately and the timeout was NO_WAIT or LockOwner had the noWait flag set
        Throws:
        StandardException - if the lock could not be obtained

      • unlock

        void unlock​(Latch item,
            int unlockCount)
        Unlock an object previously locked by lockObject().
        Parameters:
        item - the lock to unlock
        unlockCount - the number of times to unlock the item; or zero, meaning take the unlock count from the item

      • unlockReference

        Lock unlockReference​(CompatibilitySpace space,
                     Lockable ref,
                     java.lang.Object qualifier,
                     java.util.Map group)
        Unlock an object once if it is present in the specified group. Also remove the object from the group.
        Parameters:
        space - the compatibility space
        ref - a reference to the locked object
        qualifier - qualifier of the lock
        group - a map representing the locks in a group
        Returns:
        the corresponding lock in the group map, or null if the object was not unlocked

      • oneMoreWaiter

        void oneMoreWaiter()
        Notify the lock table that it has one more waiter.

      • oneLessWaiter

        void oneLessWaiter()
        Notify the lock table that it has one less waiter.

      • anyoneBlocked

        boolean anyoneBlocked()
        Check whether there are anyone blocked in the lock table.
        Returns:
        true if someone is blocked, false otherwise

      • zeroDurationLockObject

        boolean zeroDurationLockObject​(CompatibilitySpace space,
                               Lockable ref,
                               java.lang.Object qualifier,
                               int timeout)
                        throws StandardException
        Lock an object and release the lock immediately. Equivalent to 
         Lock lock = lockTable.lockObject(space, ref, qualifier, timeout);
 lockTable.unlock(lock, 1);
        except that the implementation might be more efficient.
        Parameters:
        space - the compatibility space
        ref - a reference to the locked object
        qualifier - qualifier of the lock
        timeout - maximum time to wait in milliseconds (C_LockFactory.NO_WAIT means don't wait)
        Returns:
        true if the object was locked, or false if the object couldn't be locked immediately and timeout was NO_WAIT or LockOwner had the noWait flag set
        Throws:
        StandardException - if the lock could not be obtained

      • shallowClone

        java.util.Map shallowClone()
        Create a map containing a snapshot of all the (Lockable, LockControl) pairs in the lock table.
        Returns:
        a shallow clone of the lock table

      • setDeadlockTimeout

        void setDeadlockTimeout​(int timeout)
        Set the deadlock timeout.
        Parameters:
        timeout - deadlock timeout in milliseconds

      • setWaitTimeout

        void setWaitTimeout​(int timeout)
        Set the wait timeout.
        Parameters:
        timeout - wait timeout in milliseconds

      • getWaitTimeout

        int getWaitTimeout()
        Get the wait timeout in milliseconds.

      • setDeadlockTrace

        void setDeadlockTrace​(boolean flag)
        Enable or disable tracing of deadlocks.
        Parameters:
        flag - true enables tracing, false disables tracing