package org.hibernate.testing.cache;
import java.io.Serializable;
import java.util.Comparator;
import java.util.UUID;
import java.util.concurrent.atomic.AtomicLong;
import java.util.concurrent.locks.ReentrantReadWriteLock;
import org.jboss.logging.Logger;
import org.hibernate.cache.CacheException;
import org.hibernate.cache.spi.access.SoftLock;
import org.hibernate.internal.CoreMessageLogger;
/**
* @author Strong Liu
*/
abstract class AbstractReadWriteAccessStrategy extends BaseRegionAccessStrategy {
private static final CoreMessageLogger LOG = Logger.getMessageLogger(
CoreMessageLogger.class, AbstractReadWriteAccessStrategy.class.getName()
);
private final UUID uuid = UUID.randomUUID();
private final AtomicLong nextLockId = new AtomicLong();
private ReentrantReadWriteLock reentrantReadWriteLock = new ReentrantReadWriteLock();
protected java.util.concurrent.locks.Lock readLock = reentrantReadWriteLock.readLock();
protected java.util.concurrent.locks.Lock writeLock = reentrantReadWriteLock.writeLock();
/**
* Returns <code>null</code> if the item is not readable. Locked items are not readable, nor are items created
* after the start of this transaction.
*/
@Override
public final Object get(Object key, long txTimestamp) throws CacheException {
try {
readLock.lock();
Lockable item = (Lockable) getInternalRegion().get( key );
boolean readable = item != null && item.isReadable( txTimestamp );
if ( readable ) {
return item.getValue();
}
else {
return null;
}
}
finally {
readLock.unlock();
}
}
abstract Comparator getVersionComparator();
/**
* Returns <code>false</code> and fails to put the value if there is an existing un-writeable item mapped to this
* key.
*/
@Override
public final boolean putFromLoad(Object key, Object value, long txTimestamp, Object version, boolean minimalPutOverride)
throws CacheException {
try {
writeLock.lock();
Lockable item = (Lockable) getInternalRegion().get( key );
boolean writeable = item == null || item.isWriteable( txTimestamp, version, getVersionComparator() );
if ( writeable ) {
getInternalRegion().put( key, new Item( value, version, getInternalRegion().nextTimestamp() ) );
return true;
}
else {
return false;
}
}
finally {
writeLock.unlock();
}
}
/**
* Soft-lock a cache item.
*/
public final SoftLock lockItem(Object key, Object version) throws CacheException {
try {
writeLock.lock();
Lockable item = (Lockable) getInternalRegion().get( key );
long timeout = getInternalRegion().nextTimestamp() + getInternalRegion().getTimeout();
final Lock lock = ( item == null ) ? new Lock( timeout, uuid, nextLockId(), version ) : item.lock(
timeout,
uuid,
nextLockId()
);
getInternalRegion().put( key, lock );
return lock;
}
finally {
writeLock.unlock();
}
}
/**
* Soft-unlock a cache item.
*/
public final void unlockItem(Object key, SoftLock lock) throws CacheException {
try {
writeLock.lock();
Lockable item = (Lockable) getInternalRegion().get( key );
if ( ( item != null ) && item.isUnlockable( lock ) ) {
decrementLock( key, (Lock) item );
}
else {
handleLockExpiry( key, item );
}
}
finally {
writeLock.unlock();
}
}
private long nextLockId() {
return nextLockId.getAndIncrement();
}
/**
* Unlock and re-put the given key, lock combination.
*/
protected void decrementLock(Object key, Lock lock) {
lock.unlock( getInternalRegion().nextTimestamp() );
getInternalRegion().put( key, lock );
}
/**
* Handle the timeout of a previous lock mapped to this key
*/
protected void handleLockExpiry(Object key, Lockable lock) {
LOG.expired(key);
long ts = getInternalRegion().nextTimestamp() + getInternalRegion().getTimeout();
// create new lock that times out immediately
Lock newLock = new Lock( ts, uuid, nextLockId.getAndIncrement(), null );
newLock.unlock( ts );
getInternalRegion().put( key, newLock );
}
/**
* Interface type implemented by all wrapper objects in the cache.
*/
protected static interface Lockable {
/**
* Returns <code>true</code> if the enclosed value can be read by a transaction started at the given time.
*/
public boolean isReadable(long txTimestamp);
/**
* Returns <code>true</code> if the enclosed value can be replaced with one of the given version by a
* transaction started at the given time.
*/
public boolean isWriteable(long txTimestamp, Object version, Comparator versionComparator);
/**
* Returns the enclosed value.
*/
public Object getValue();
/**
* Returns <code>true</code> if the given lock can be unlocked using the given SoftLock instance as a handle.
*/
public boolean isUnlockable(SoftLock lock);
/**
* Locks this entry, stamping it with the UUID and lockId given, with the lock timeout occuring at the specified
* time. The returned Lock object can be used to unlock the entry in the future.
*/
public Lock lock(long timeout, UUID uuid, long lockId);
}
/**
* Wrapper type representing unlocked items.
*/
protected final static class Item implements Serializable, Lockable {
private static final long serialVersionUID = 1L;
private final Object value;
private final Object version;
private final long timestamp;
/**
* Creates an unlocked item wrapping the given value with a version and creation timestamp.
*/
Item(Object value, Object version, long timestamp) {
this.value = value;
this.version = version;
this.timestamp = timestamp;
}
/**
* {@inheritDoc}
*/
public boolean isReadable(long txTimestamp) {
return txTimestamp > timestamp;
}
/**
* {@inheritDoc}
*/
public boolean isWriteable(long txTimestamp, Object newVersion, Comparator versionComparator) {
return version != null && versionComparator.compare( version, newVersion ) < 0;
}
/**
* {@inheritDoc}
*/
public Object getValue() {
return value;
}
/**
* {@inheritDoc}
*/
public boolean isUnlockable(SoftLock lock) {
return false;
}
/**
* {@inheritDoc}
*/
public Lock lock(long timeout, UUID uuid, long lockId) {
return new Lock( timeout, uuid, lockId, version );
}
}
/**
* Wrapper type representing locked items.
*/
protected final static class Lock implements Serializable, Lockable, SoftLock {
private static final long serialVersionUID = 2L;
private final UUID sourceUuid;
private final long lockId;
private final Object version;
private long timeout;
private boolean concurrent;
private int multiplicity = 1;
private long unlockTimestamp;
/**
* Creates a locked item with the given identifiers and object version.
*/
Lock(long timeout, UUID sourceUuid, long lockId, Object version) {
this.timeout = timeout;
this.lockId = lockId;
this.version = version;
this.sourceUuid = sourceUuid;
}
/**
* {@inheritDoc}
*/
public boolean isReadable(long txTimestamp) {
return false;
}
/**
* {@inheritDoc}
*/
public boolean isWriteable(long txTimestamp, Object newVersion, Comparator versionComparator) {
if ( txTimestamp > timeout ) {
// if timedout then allow write
return true;
}
if ( multiplicity > 0 ) {
// if still locked then disallow write
return false;
}
return version == null ? txTimestamp > unlockTimestamp : versionComparator.compare(
version,
newVersion
) < 0;
}
/**
* {@inheritDoc}
*/
public Object getValue() {
return null;
}
/**
* {@inheritDoc}
*/
public boolean isUnlockable(SoftLock lock) {
return equals( lock );
}
/**
* {@inheritDoc}
*/
@Override
public boolean equals(Object o) {
if ( o == this ) {
return true;
}
else if ( o instanceof Lock ) {
return ( lockId == ( (Lock) o ).lockId ) && sourceUuid.equals( ( (Lock) o ).sourceUuid );
}
else {
return false;
}
}
/**
* {@inheritDoc}
*/
@Override
public int hashCode() {
int hash = ( sourceUuid != null ? sourceUuid.hashCode() : 0 );
int temp = (int) lockId;
for ( int i = 1; i < Long.SIZE / Integer.SIZE; i++ ) {
temp ^= ( lockId >>> ( i * Integer.SIZE ) );
}
return hash + temp;
}
/**
* Returns true if this Lock has been concurrently locked by more than one transaction.
*/
public boolean wasLockedConcurrently() {
return concurrent;
}
/**
* {@inheritDoc}
*/
public Lock lock(long timeout, UUID uuid, long lockId) {
concurrent = true;
multiplicity++;
this.timeout = timeout;
return this;
}
/**
* Unlocks this Lock, and timestamps the unlock event.
*/
public void unlock(long timestamp) {
if ( --multiplicity == 0 ) {
unlockTimestamp = timestamp;
}
}
/**
* {@inheritDoc}
*/
public String toString() {
StringBuilder sb = new StringBuilder( "Lock Source-UUID:" + sourceUuid + " Lock-ID:" + lockId );
return sb.toString();
}
}
}