/*
|
* CDDL HEADER START
|
*
|
* The contents of this file are subject to the terms of the
|
* Common Development and Distribution License, Version 1.0 only
|
* (the "License"). You may not use this file except in compliance
|
* with the License.
|
*
|
* You can obtain a copy of the license at
|
* trunk/opends/resource/legal-notices/OpenDS.LICENSE
|
* or https://OpenDS.dev.java.net/OpenDS.LICENSE.
|
* See the License for the specific language governing permissions
|
* and limitations under the License.
|
*
|
* When distributing Covered Code, include this CDDL HEADER in each
|
* file and include the License file at
|
* trunk/opends/resource/legal-notices/OpenDS.LICENSE. If applicable,
|
* add the following below this CDDL HEADER, with the fields enclosed
|
* by brackets "[]" replaced with your own identifying information:
|
* Portions Copyright [yyyy] [name of copyright owner]
|
*
|
* CDDL HEADER END
|
*
|
*
|
* Portions Copyright 2006-2007 Sun Microsystems, Inc.
|
*/
|
package org.opends.server.api;
|
|
|
|
import java.util.List;
|
import java.util.concurrent.locks.Lock;
|
|
import org.opends.server.config.ConfigException;
|
import org.opends.server.types.DN;
|
import org.opends.server.types.Entry;
|
import org.opends.server.types.InitializationException;
|
import org.opends.server.types.LockType;
|
import org.opends.server.types.LockManager;
|
import org.opends.server.types.DebugLogLevel;
|
import org.opends.server.admin.std.server.EntryCacheCfg;
|
import org.opends.server.loggers.debug.DebugTracer;
|
import static org.opends.server.loggers.debug.DebugLogger.*;
|
|
|
|
/**
|
* This class defines the set of methods that must be implemented by a
|
* Directory Server entry cache. Note that components accessing the
|
* entry cache must not depend on any particular behavior. For
|
* example, if a call is made to <CODE>putEntry</CODE> to store an
|
* entry in the cache, there is no guarantee that immediately calling
|
* <CODE>getEntry</CODE> will be able to retrieve it. There are
|
* several potential reasons for this, including:
|
* <UL>
|
* <LI>The entry may have been deleted or replaced by another thread
|
* between the <CODE>putEntry</CODE> and <CODE>getEntry</CODE>
|
* calls.</LI>
|
* <LI>The entry cache may implement a purging mechanism and the
|
* entry added may have been purged between the
|
* <CODE>putEntry</CODE> and <CODE>getEntry</CODE> calls.</LI>
|
* <LI>The entry cache may implement some kind of filtering
|
* mechanism to determine which entries to store, and entries
|
* not matching the appropriate criteria may not be stored.</LI>
|
* <LI>The entry cache may not actually store any entries (this is
|
* the behavior of the default cache that will be used if none
|
* is configured).</LI>
|
* </UL>
|
*
|
* @param <T> The type of configuration handled by this entry
|
* cache.
|
*/
|
public abstract class EntryCache
|
<T extends EntryCacheCfg>
|
{
|
/**
|
* The tracer object for the debug logger.
|
*/
|
private static final DebugTracer TRACER = getTracer();
|
|
|
|
/**
|
* The maximum length of time to try to obtain a lock
|
* before giving up.
|
*/
|
protected long lockTimeout;
|
|
|
|
/**
|
* Initializes this entry cache implementation so that it will be
|
* available for storing and retrieving entries.
|
*
|
* @param configuration The configuration to use to initialize
|
* the entry cache.
|
*
|
* @throws ConfigException If there is a problem with the provided
|
* configuration entry that would prevent
|
* this entry cache from being used.
|
*
|
* @throws InitializationException If a problem occurs during the
|
* initialization process that is
|
* not related to the
|
* configuration.
|
*/
|
public abstract void initializeEntryCache(T configuration)
|
throws ConfigException, InitializationException;
|
|
|
|
/**
|
* Indicates whether the provided configuration is acceptable for
|
* this entry cache. It should be possible to call this method on
|
* an uninitialized entry cache instance in order to determine
|
* whether the entry cache would be able to use the provided
|
* configuration.
|
* <BR><BR>
|
* Note that implementations which use a subclass of the provided
|
* configuration class will likely need to cast the configuration
|
* to the appropriate subclass type.
|
*
|
* @param configuration The entry cache configuration for
|
* which to make the determination.
|
* @param unacceptableReasons A list that may be used to hold the
|
* reasons that the provided
|
* configuration is not acceptable.
|
*
|
* @return {@code true} if the provided configuration is acceptable
|
* for this entry cache, or {@code false} if not.
|
*/
|
public boolean isConfigurationAcceptable(
|
EntryCacheCfg configuration,
|
List<String> unacceptableReasons)
|
{
|
// This default implementation does not perform any special
|
// validation. It should be overridden by entry cache
|
// implementations that wish to perform more detailed validation.
|
return true;
|
}
|
|
|
|
/**
|
* Performs any necessary cleanup work (e.g., flushing all cached
|
* entries and releasing any other held resources) that should be
|
* performed when the server is to be shut down or the entry cache
|
* destroyed or replaced.
|
*/
|
public abstract void finalizeEntryCache();
|
|
|
|
/**
|
* Indicates whether the entry cache currently contains the entry
|
* with the specified DN. This method may be called without holding
|
* any locks if a point-in-time check is all that is required.
|
* Note that this method is called from @see #getEntry(DN entryDN,
|
* LockType lockType, List lockList)
|
*
|
* @param entryDN The DN for which to make the determination.
|
*
|
* @return <CODE>true</CODE> if the entry cache currently contains
|
* the entry with the specified DN, or <CODE>false</CODE>
|
* if not.
|
*/
|
public abstract boolean containsEntry(DN entryDN);
|
|
|
|
/**
|
* Retrieves the entry with the specified DN from the cache. The
|
* caller should have already acquired a read or write lock for the
|
* entry if such protection is needed.
|
* Note that this method is called from @see #getEntry(DN entryDN,
|
* LockType lockType, List lockList)
|
*
|
* @param entryDN The DN of the entry to retrieve.
|
*
|
* @return The requested entry if it is present in the cache, or
|
* <CODE>null</CODE> if it is not present.
|
*/
|
public abstract Entry getEntry(DN entryDN);
|
|
|
|
/**
|
* Retrieves the entry with the specified DN from the cache,
|
* obtaining a lock on the entry before it is returned. If the
|
* entry is present in the cache, then a lock will be obtained for
|
* that entry and appended to the provided list before the entry is
|
* returned. If the entry is not present, then no lock will be
|
* obtained. Note that although this method is declared non-final
|
* it is not recommended for subclasses to implement this method.
|
*
|
* @param entryDN The DN of the entry to retrieve.
|
* @param lockType The type of lock to obtain (it may be
|
* <CODE>NONE</CODE>).
|
* @param lockList The list to which the obtained lock will be
|
* added (note that no lock will be added if the
|
* lock type was <CODE>NONE</CODE>).
|
*
|
* @return The requested entry if it is present in the cache, or
|
* <CODE>null</CODE> if it is not present.
|
*/
|
public Entry getEntry(DN entryDN,
|
LockType lockType,
|
List<Lock> lockList) {
|
|
if (!containsEntry(entryDN)) {
|
return null;
|
}
|
|
// Obtain a lock for the entry before actually retrieving the
|
// entry itself thus preventing any stale entries being returned,
|
// see Issue #1589 for more details. If an error occurs, then
|
// make sure no lock is held and return null. Otherwise, return
|
// the entry.
|
switch (lockType)
|
{
|
case READ:
|
// Try to obtain a read lock for the entry.
|
Lock readLock = LockManager.lockRead(entryDN, lockTimeout);
|
if (readLock == null)
|
{
|
// We couldn't get the lock, so we have to return null.
|
return null;
|
}
|
else
|
{
|
try
|
{
|
lockList.add(readLock);
|
// and load.
|
Entry entry = getEntry(entryDN);
|
if (entry == null)
|
{
|
lockList.remove(readLock);
|
LockManager.unlock(entryDN, readLock);
|
return null;
|
}
|
return entry;
|
}
|
catch (Exception e)
|
{
|
if (debugEnabled())
|
{
|
TRACER.debugCaught(DebugLogLevel.ERROR, e);
|
}
|
|
// The attempt to add the lock to the list failed,
|
// so we need to release the lock and return null.
|
try
|
{
|
LockManager.unlock(entryDN, readLock);
|
}
|
catch (Exception e2)
|
{
|
if (debugEnabled())
|
{
|
TRACER.debugCaught(DebugLogLevel.ERROR, e2);
|
}
|
}
|
|
return null;
|
}
|
}
|
|
case WRITE:
|
// Try to obtain a write lock for the entry.
|
Lock writeLock = LockManager.lockWrite(entryDN, lockTimeout);
|
if (writeLock == null)
|
{
|
// We couldn't get the lock, so we have to return null.
|
return null;
|
}
|
else
|
{
|
try
|
{
|
lockList.add(writeLock);
|
// and load.
|
Entry entry = getEntry(entryDN);
|
if (entry == null)
|
{
|
lockList.remove(writeLock);
|
LockManager.unlock(entryDN, writeLock);
|
return null;
|
}
|
return entry;
|
}
|
catch (Exception e)
|
{
|
if (debugEnabled())
|
{
|
TRACER.debugCaught(DebugLogLevel.ERROR, e);
|
}
|
|
// The attempt to add the lock to the list failed,
|
// so we need to release the lock and return null.
|
try
|
{
|
LockManager.unlock(entryDN, writeLock);
|
}
|
catch (Exception e2)
|
{
|
if (debugEnabled())
|
{
|
TRACER.debugCaught(DebugLogLevel.ERROR, e2);
|
}
|
}
|
|
return null;
|
}
|
}
|
|
case NONE:
|
// We don't need to obtain a lock, so just return the entry.
|
Entry entry = getEntry(entryDN);
|
if (entry == null)
|
{
|
return null;
|
}
|
return entry;
|
|
default:
|
// This is an unknown type of lock, so we'll return null.
|
return null;
|
}
|
}
|
|
|
|
/**
|
* Retrieves the requested entry if it is present in the cache,
|
* obtaining a lock on the entry before it is returned. If the
|
* entry is present in the cache, then a lock will be obtained for
|
* that entry and appended to the provided list before the entry is
|
* returned. If the entry is not present, then no lock will be
|
* obtained. Note that although this method is declared non-final
|
* it is not recommended for subclasses to implement this method.
|
*
|
* @param backend The backend associated with the entry to
|
* retrieve.
|
* @param entryID The entry ID within the provided backend for
|
* the specified entry.
|
* @param lockType The type of lock to obtain (it may be
|
* <CODE>NONE</CODE>).
|
* @param lockList The list to which the obtained lock will be
|
* added (note that no lock will be added if the
|
* lock type was <CODE>NONE</CODE>).
|
*
|
* @return The requested entry if it is present in the cache, or
|
* <CODE>null</CODE> if it is not present.
|
*/
|
public Entry getEntry(Backend backend, long entryID,
|
LockType lockType,
|
List<Lock> lockList) {
|
|
// Translate given backend/entryID pair to entryDN.
|
DN entryDN = getEntryDN(backend, entryID);
|
if (entryDN == null) {
|
return null;
|
}
|
|
// Delegate to by DN lock and load method.
|
return getEntry(entryDN, lockType, lockList);
|
}
|
|
|
|
/**
|
* Retrieves the entry ID for the entry with the specified DN from
|
* the cache. The caller should have already acquired a read or
|
* write lock for the entry if such protection is needed.
|
*
|
* @param entryDN The DN of the entry for which to retrieve the
|
* entry ID.
|
*
|
* @return The entry ID for the requested entry, or -1 if it is
|
* not present in the cache.
|
*/
|
public abstract long getEntryID(DN entryDN);
|
|
|
|
/**
|
* Retrieves the entry DN for the entry with the specified ID on
|
* the specific backend from the cache. The caller should have
|
* already acquired a read or write lock for the entry if such
|
* protection is needed.
|
* Note that this method is called from @see #getEntry(Backend
|
* backend, long entryID, LockType lockType, List lockList)
|
*
|
* @param backend The backend associated with the entry for
|
* which to retrieve the entry DN.
|
* @param entryID The entry ID within the provided backend
|
* for which to retrieve the entry DN.
|
*
|
* @return The entry DN for the requested entry, or
|
* <CODE>null</CODE> if it is not present in the cache.
|
*/
|
protected abstract DN getEntryDN(Backend backend, long entryID);
|
|
|
|
/**
|
* Stores the provided entry in the cache. Note that the mechanism
|
* that it uses to achieve this is implementation-dependent, and it
|
* is acceptable for the entry to not actually be stored in any
|
* cache.
|
*
|
* @param entry The entry to store in the cache.
|
* @param backend The backend with which the entry is associated.
|
* @param entryID The entry ID within the provided backend that
|
* uniquely identifies the specified entry.
|
*/
|
public abstract void putEntry(Entry entry, Backend backend,
|
long entryID);
|
|
|
|
/**
|
* Stores the provided entry in the cache only if it does not
|
* conflict with an entry that already exists. Note that the
|
* mechanism that it uses to achieve this is
|
* implementation-dependent, and it is acceptable for the entry to
|
* not actually be stored in any cache. However, this method must
|
* not overwrite an existing version of the entry.
|
*
|
* @param entry The entry to store in the cache.
|
* @param backend The backend with which the entry is associated.
|
* @param entryID The entry ID within the provided backend that
|
* uniquely identifies the specified entry.
|
*
|
* @return <CODE>false</CODE> if an existing entry or some other
|
* problem prevented the method from completing
|
* successfully, or <CODE>true</CODE> if there was no
|
* conflict and the entry was either stored or the cache
|
* determined that this entry should never be cached for
|
* some reason.
|
*/
|
public abstract boolean putEntryIfAbsent(Entry entry,
|
Backend backend,
|
long entryID);
|
|
|
|
/**
|
* Removes the specified entry from the cache.
|
*
|
* @param entryDN The DN of the entry to remove from the cache.
|
*/
|
public abstract void removeEntry(DN entryDN);
|
|
|
|
/**
|
* Removes all entries from the cache. The cache should still be
|
* available for future use.
|
*/
|
public abstract void clear();
|
|
|
|
/**
|
* Removes all entries from the cache that are associated with the
|
* provided backend.
|
*
|
* @param backend The backend for which to flush the associated
|
* entries.
|
*/
|
public abstract void clearBackend(Backend backend);
|
|
|
|
/**
|
* Removes all entries from the cache that are below the provided
|
* DN.
|
*
|
* @param baseDN The base DN below which all entries should be
|
* flushed.
|
*/
|
public abstract void clearSubtree(DN baseDN);
|
|
|
|
/**
|
* Attempts to react to a scenario in which it is determined that
|
* the system is running low on available memory. In this case, the
|
* entry cache should attempt to free some memory if possible to try
|
* to avoid out of memory errors.
|
*/
|
public abstract void handleLowMemory();
|
}
|
