Examples of org.apache.derby.iapi.services.locks.Lockable

Package org.apache.derby.iapi.services.locks

Examples of org.apache.derby.iapi.services.locks.Lockable

org.apache.derby.iapi.services.locks.Lockable
Any object that needs to be locked must implement Lockable. This allows a generic lock manager that can have locking policies defined on a per-object basis. A request to lock the object takes a qualifier, this qualifier may be used the object to implement a complex locking policy, e.g. traditional database shared, update and exclusive locks.
The lock manager uses this ordered protocol to determine if a lock request on a Lockable L with qualifier Q1 in compatibility space CS1 can be granted:
1. If no locks are held on L in any compatability space then the request is granted.
2. If L.requestCompatible(Q1) returns true then the lock is granted.
3. Otherwise the request is granted if the following expression evaluates to true for every other lock { CSn, Qn} held on L
  - ```
      ( ( CSn == CS1 ) && L.lockerAlwaysCompatible() ) 
```
- ```
 || (L.reqestCompatible(Q1, Qn)) 
```
If the request is granted then a call is made to L.lockEvent(CS1, Q1) .
When the lock is released a call is made to L.unlockEvent(CS1, Q1) .
The lock manager uses equals() and hashCode() to identify unique Lockables.
If the class implementing Lockable requires that each instance of class correspond to a different locked object then the equals() method must test equality via the reference equality test (==), this is the default behaviour for equality.
If the class implementing Lockable require that each instance of the class that has the same value (as defined by the class) corresponds to a locked object then its equals() method must reflect that, e.g. by testing equality of its fields. In this case the first Lockable to be locked will be kept by lock manager as the key for the lock. Thus even after the first caller unlocks the object, its reference will still be kept by the lock manager. Thus Lockable's that per value equality must be designed so that they are never re-used for different lockable concepts.
In either case the equals() method must accept a reference to an object of a different type.
As per standard hashtable rules the value returned by hashCode() must be in sync with the equals() method.
MT - Mutable - : single thread required, synchronization is provided by the lock manager. If the class implementing Lockable uses value equality then it must have an immutable identity.

    if (isUnlocked())
      return true;


        boolean grantLock    = false;


    Lockable lref = ref;
    List lgranted = granted;


        {
            // Check to see if the only locks on the granted queue that
            // we are incompatible with are locks we own.
            boolean selfCompatible = lref.lockerAlwaysCompatible();


      int index = 0;
      int endIndex = firstGrant == null ? lgranted.size() : 0;
      do {


        Lock gl = firstGrant == null ? (Lock) lgranted.get(index) : firstGrant;


                boolean sameSpace = 
                    (gl.getCompatabilitySpace().equals(compatabilitySpace));


                if (sameSpace && selfCompatible) 
                {
                    // if it's one of our locks and we are always compatible 
                    // with our own locks then yes, we can be granted.
                    
                    grantLock = true;
                    continue;
                }
                else if (!lref.requestCompatible(qualifier, gl.getQualifier())) 
                {
                    // If we are not compatible with some already granted lock
                    // then we can't be granted, give up right away.
                    
                    grantLock = false;

View Full Code Here

    // jump past it.
    boolean grantLock = false;    
    boolean otherWaiters = (firstWaiter() != null);


    Lock lockItem = null;
    Lockable lref = ref;


    // If we haven't been able to grant the lock yet then see if we hold a 
        // lock already that we are compatible with and there are no granted 
        // incompatible locks. If the object appears unlocked (due to a just 
        // released lock, but the first waiter hasn't woken yet)
    // then we obviously don't hold a lock, so just join the wait queue.
    boolean spaceHasALock = false;
    boolean noGrantAtAll = false;
    if (!grantLock && !isUnlocked()) {


      boolean selfCompatible = lref.lockerAlwaysCompatible();
      
      int index = 0;
      int endIndex = firstGrant == null ? granted.size() : 0;
      do {


        Lock gl = firstGrant == null ? (Lock) granted.get(index) : firstGrant;




        boolean sameSpace = (gl.getCompatabilitySpace().equals(compatabilitySpace));


        // if it's one of our locks and we are always compatible with 
                // our own locks then yes, we can be granted.
        if (sameSpace && selfCompatible) {


          spaceHasALock = true;


          if (noGrantAtAll)
            break;


          if (qualifier == gl.getQualifier())
            lockItem = gl;


          grantLock = true;
          continue;
        }
        
        // If we are not compatible with some already granted lock
                // then we can't be granted, give up right away.
        if (!lref.requestCompatible(qualifier, gl.getQualifier())) {
          grantLock = false;
          lockItem = null;


          // we can't give up rightaway if spaceHasALock is false
          // because we need to ensure that canSkip is set correctly

View Full Code Here

    {
        Hashtable attributes = new Hashtable(17);
        Object lock_type = currentLock.getQualifier();


        // want containerId, segmentId, pageNum, recId from locktable
        Lockable lockable = currentLock.getLockable();


        // See if the lockable object wants to participate
        if( !lockable.lockAttributes(ALL, attributes) )
        {
            currentRow = null;
            return;
        }

View Full Code Here

    {
        Hashtable attributes = new Hashtable(17);
        Object lock_type = currentLock.getQualifier();


        // want containerId, segmentId, pageNum, recId from locktable
        Lockable lockable = currentLock.getLockable();


        // See if the lockable object wants to participate
        if( !lockable.lockAttributes(ALL, attributes) )
        {
            currentRow = null;
            return;
        }

View Full Code Here

  {
    HashMap clone = new HashMap();


    for (Iterator it = locks.keySet().iterator(); it.hasNext(); )
    {
      Lockable lockable = (Lockable) it.next();
      Control control = getControl(lockable);


      clone.put(lockable, control.shallowClone());
    }

View Full Code Here

    if (isUnlocked())
      return true;


        boolean grantLock    = false;


    Lockable lref = ref;
    List lgranted = granted;


        {
            // Check to see if the only locks on the granted queue that
            // we are incompatible with are locks we own.
            boolean selfCompatible = lref.lockerAlwaysCompatible();


      int index = 0;
      int endIndex = firstGrant == null ? lgranted.size() : 0;
      do {


        Lock gl = firstGrant == null ? (Lock) lgranted.get(index) : firstGrant;


                boolean sameSpace = 
                    (gl.getCompatabilitySpace() == compatibilitySpace);


                if (sameSpace && selfCompatible) 
                {
                    // if it's one of our locks and we are always compatible 
                    // with our own locks then yes, we can be granted.
                    
                    grantLock = true;
                    continue;
                }
                else if (!lref.requestCompatible(qualifier, gl.getQualifier())) 
                {
                    // If we are not compatible with some already granted lock
                    // then we can't be granted, give up right away.
                    
                    grantLock = false;

View Full Code Here

    // jump past it.
    boolean grantLock = false;    
    boolean otherWaiters = (firstWaiter() != null);


    Lock lockItem = null;
    Lockable lref = ref;


    // If we haven't been able to grant the lock yet then see if we hold a 
        // lock already that we are compatible with and there are no granted 
        // incompatible locks. If the object appears unlocked (due to a just 
        // released lock, but the first waiter hasn't woken yet)
    // then we obviously don't hold a lock, so just join the wait queue.
    boolean spaceHasALock = false;
    boolean noGrantAtAll = false;
    if (!isUnlocked()) {


      boolean selfCompatible = lref.lockerAlwaysCompatible();
      
      int index = 0;
      int endIndex = firstGrant == null ? granted.size() : 0;
      do {


        Lock gl = firstGrant == null ? (Lock) granted.get(index) : firstGrant;




        boolean sameSpace =
          (gl.getCompatabilitySpace() == compatibilitySpace);


        // if it's one of our locks and we are always compatible with 
                // our own locks then yes, we can be granted.
        if (sameSpace && selfCompatible) {


          spaceHasALock = true;


          if (noGrantAtAll)
            break;


          if (qualifier == gl.getQualifier())
            lockItem = gl;


          grantLock = true;
          continue;
        }
        
        // If we are not compatible with some already granted lock
                // then we can't be granted, give up right away.
        if (!lref.requestCompatible(qualifier, gl.getQualifier())) {
          grantLock = false;
          lockItem = null;


          // we can't give up rightaway if spaceHasALock is false
          // because we need to ensure that canSkip is set correctly

View Full Code Here




    // 4 things we are interested in from the lockable:
    // containerId, segmentId, pageNum, recId


    Lockable lockable = lock.getLockable();


    // see if this lockable object wants to participate
    if (!lockable.lockAttributes(flag, attributes))
      return null;        


    // if it does, the lockable object must have filled in the following
    // fields
    if (SanityManager.DEBUG)

View Full Code Here




    // 4 things we are interested in from the lockable:
    // containerId, segmentId, pageNum, recId


    Lockable lockable = lock.getLockable();


    // see if this lockable object wants to participate
    if (!lockable.lockAttributes(flag, attributes))
      return null;        


    // if it does, the lockable object must have filled in the following
    // fields
    if (SanityManager.DEBUG)

View Full Code Here

  {
    LockSet clone = new LockSet(factory);


    for (Enumeration e = keys(); e.hasMoreElements(); )
    {
      Lockable lockable = (Lockable)e.nextElement();
      Control control = getControl(lockable);


      clone.put(lockable, control.shallowClone());
    }

View Full Code Here

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Related Classes of org.apache.derby.iapi.services.locks.Lockable

org.apache.derby.diag.LockTable

org.apache.derby.impl.services.locks.LockControl

org.apache.derby.impl.services.locks.LockSet

org.apache.derby.impl.services.locks.Timeout

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