Class AbstractPool

java.lang.Object
org.apache.derby.impl.services.locks.AbstractPool
All Implemented Interfaces:
LockFactory, PropertySetCallback
Direct Known Subclasses:
ConcurrentPool

abstract class AbstractPool extends Object implements LockFactory
An abstract implementation of LockFactory that allows different implementations of the lock table to be plugged in. All the methods of LockFactory are implemented. Subclasses must implement the createLockTable() method and make it return the desired LockTable object.
MT - Mutable - Container Object : Thread Aware
  • Field Details

    • lockTable

      protected final LockTable lockTable
      The complete set of locks in the system
      MT - immutable - content dynamic : LockSet is ThreadSafe
    • deadlockMonitor

      int deadlockMonitor
      True if all deadlocks errors should be logged.
  • Constructor Details

    • AbstractPool

      protected AbstractPool()
  • Method Details

    • createLockTable

      protected abstract LockTable createLockTable()
      Create the lock table that contains the mapping from Lockables to locks.
      Returns:
      an object implementing the LockTable interface
    • lockObject

      public boolean lockObject(CompatibilitySpace compatibilitySpace, Object group, Lockable ref, Object qualifier, int timeout) throws StandardException
      Lock a specific object with a timeout.
      MT - thread safe
      Specified by:
      lockObject in interface LockFactory
      Parameters:
      compatibilitySpace - object defining compatibility space
      group - handle of group, must be private to a thread.
      ref - reference to object to be locked
      qualifier - A qualification of the request.
      timeout - the maximum time to wait in milliseconds, LockFactory.NO_WAIT means don't wait.
      Returns:
      true if the lock was obtained, false if timeout is equal to LockFactory.NO_WAIT and the lock could not be granted.
      Throws:
      StandardException - Standard Derby error policy
      See Also:
    • createCompatibilitySpace

      public CompatibilitySpace createCompatibilitySpace(LockOwner owner)
      Create an object which can be used as a compatibility space within this lock manager.
      Specified by:
      createCompatibilitySpace in interface LockFactory
      Parameters:
      owner - the owner of the compatibility space
      Returns:
      an object which represents a compatibility space
    • unlock

      public int unlock(CompatibilitySpace compatibilitySpace, Object group, Lockable ref, Object qualifier)
      Unlock a specific object
      MT - thread safe
      Specified by:
      unlock in interface LockFactory
      Parameters:
      compatibilitySpace - object defining compatibility space
      group - handle of group.
      ref - Reference to object to be unlocked.
      qualifier - qualifier of lock to be unlocked
      Returns:
      number of locks released (one or zero).
      See Also:
    • unlockGroup

      public void unlockGroup(CompatibilitySpace compatibilitySpace, Object group)
      Unlock a group of objects.
      MT - thread safe
      Specified by:
      unlockGroup in interface LockFactory
      Parameters:
      compatibilitySpace - object defining compatibility space
      group - handle of group that objects were locked with. If group is null then this call is equivilent to unlockAll().
      See Also:
    • unlockGroup

      public void unlockGroup(CompatibilitySpace compatibilitySpace, Object group, Matchable key)
      Description copied from interface: LockFactory
      Unlock all locks on a group that match the passed in value.
      Specified by:
      unlockGroup in interface LockFactory
    • transfer

      public void transfer(CompatibilitySpace compatibilitySpace, Object oldGroup, Object newGroup)
      Transfer a set of locks from one group to another.
      MT - thread safe
      Specified by:
      transfer in interface LockFactory
      See Also:
    • anyoneBlocked

      public boolean anyoneBlocked()
      Returns true if locks by anyone are blocking anyone else
      Specified by:
      anyoneBlocked in interface LockFactory
    • areLocksHeld

      public boolean areLocksHeld(CompatibilitySpace compatibilitySpace, Object group)
      Return true if locks are held in this group and this space.
      MT - thread safe
      Specified by:
      areLocksHeld in interface LockFactory
      Parameters:
      group - handle of group that objects were locked with.
      See Also:
    • areLocksHeld

      public boolean areLocksHeld(CompatibilitySpace compatibilitySpace)
      Return true if locks are held in this space
      MT - thread safe
      Specified by:
      areLocksHeld in interface LockFactory
      See Also:
    • zeroDurationlockObject

      public boolean zeroDurationlockObject(CompatibilitySpace compatibilitySpace, Lockable ref, Object qualifier, int timeout) throws StandardException
      Description copied from interface: LockFactory
      Lock an object with zero duration within a compatibility space, waits up to timeout milli-seconds for the object to become unlocked. A timeout of 0 means do not wait for the lock to be unlocked. Note the actual time waited is approximate.

      Zero duration means the lock is released as soon as it is obtained.

      A compatibility space in an space where lock requests are assumed to be compatible and granted by the lock manager if the trio {compatibilitySpace, ref, qualifier} are equal (i.e. reference equality for qualifier and compatibilitySpace, equals() method for ref). Granted by the lock manager means that the Lockable object may or may not be queried to see if the request is compatible.
      A compatibility space is not assumed to be owned by a single thread.

      Specified by:
      zeroDurationlockObject in interface LockFactory
      Parameters:
      compatibilitySpace - object defining compatibility space
      ref - reference to object to be locked
      qualifier - A qualification of the request.
      timeout - the maximum time to wait in milliseconds, LockFactory.NO_WAIT means don't wait.
      Returns:
      true if the lock was obtained, false if timeout is equal to LockFactory.NO_WAIT and the lock could not be granted.
      Throws:
      StandardException - if a deadlock has occurred (message id will be LockFactory.Deadlock), or if the wait for the lock timed out (message id will be LockFactory.TimeOut), or if another thread interrupted this thread while it was waiting for the lock (this will be a StandardException with a nested InterruptedException, and the message id will be LockFactory.InterruptedExceptionId), or if any other error occurs when locking the object
    • isLockHeld

      public boolean isLockHeld(CompatibilitySpace compatibilitySpace, Object group, Lockable ref, Object qualifier)
      Description copied from interface: LockFactory
      Check to see if a specific lock is held.
      Specified by:
      isLockHeld in interface LockFactory
    • getWaitTimeout

      public int getWaitTimeout()
      Get the lock timeout in milliseconds. A negative number means that there is no timeout.
      Specified by:
      getWaitTimeout in interface LockFactory
    • setLimit

      public void setLimit(CompatibilitySpace compatibilitySpace, Object group, int limit, Limit callback)
      Description copied from interface: LockFactory
      Install a limit that is called when the size of the group exceeds the required limit.
      It is not guaranteed that the callback method (Limit.reached) is called as soon as the group size exceeds the given limit. If the callback method does not result in a decrease in the number of locks held then the lock factory implementation may delay calling the method again. E.g. with a limit of 500 and a reached() method that does nothing, may result in the call back method only being called when the group size reaches 550.
      Only one limit may be in place for a group at any time.
      Specified by:
      setLimit in interface LockFactory
      See Also:
    • clearLimit

      public void clearLimit(CompatibilitySpace compatibilitySpace, Object group)
      Clear a limit set by setLimit.
      Specified by:
      clearLimit in interface LockFactory
    • noLockWait

      static boolean noLockWait(int timeout, CompatibilitySpace compat)
      Check if we should not wait for locks, given the specified timeout and compatibility space. If the timeout is C_LockFactory.NO_WAIT or the LockOwner has the noWait flag set, we shouldn't wait for locks.
      Parameters:
      timeout - the specified timeout
      compat - the compatibility space
      Returns:
      true if we shouldn't wait for locks, false otherwise
    • makeVirtualLockTable

      public Enumeration makeVirtualLockTable()
      Routines to support lock diagnostics VTIs for the benefit of VirtualLockTable
      Specified by:
      makeVirtualLockTable in interface LockFactory
    • init

      public void init(boolean dbOnly, Dictionary p)
      Description copied from interface: PropertySetCallback
      Initialize the properties for this callback. Called when addPropertySetNotification() is called with a non-null transaction controller. This allows code to set read its initial property values at boot time.

      Code within an init() method should use the 3 argument PropertyUtil method getPropertyFromSet() to obtain a property's value.

      Specified by:
      init in interface PropertySetCallback
      Parameters:
      dbOnly - true if only per-database properties are to be looked at
      p - the complete set of per-database properties.
    • getAndApply

      private void getAndApply(boolean dbOnly, Dictionary p, String key)
    • validate

      public boolean validate(String key, Serializable value, Dictionary p) throws StandardException
      Description copied from interface: PropertySetCallback
      Validate a property change.
      Specified by:
      validate in interface PropertySetCallback
      Parameters:
      key - Property key for the property being set
      value - proposed new value for the property being set or null if the property is being dropped.
      p - Property set before the change. SettingProperty may read but must never change p.
      Returns:
      true if this object was interested in this property, false otherwise.
      Throws:
      StandardException - Oh well.
    • apply

      public Serviceable apply(String key, Serializable value, Dictionary p) throws StandardException
      Description copied from interface: PropertySetCallback
      Apply a property change. Will only be called after validate has been called and only if validate returned true. If this method is called then the new value is the value to be used, ie. the property is not set in the overriding JVM system set.
      Specified by:
      apply in interface PropertySetCallback
      Parameters:
      key - Property key for the property being set
      value - proposed new value for the property being set or null if the property is being dropped.
      p - Property set before the change. SettingProperty may read but must never change p.
      Returns:
      post commit work for the property change.
      Throws:
      StandardException - Oh well.
    • map

      public Serializable map(String key, Serializable value, Dictionary p)
      Description copied from interface: PropertySetCallback
      Map a proposed new value for a property to an official value. Will only be called after apply() has been called.
      Specified by:
      map in interface PropertySetCallback
      Parameters:
      key - Property key for the property being set
      value - proposed new value for the property being set or null if the property is being dropped.
      p - Property set before the change. SettingProperty may read but must never change p.
      Returns:
      new value for the change
    • getWaitValue

      private static int getWaitValue(String value, int defaultValue)