Package org.opends.server.extensions

Class NullEntryCache

java.lang.Object

org.opends.server.api.MonitorProvider

org.opends.server.api.EntryCache<EntryCacheCfg>

org.opends.server.extensions.NullEntryCache

All Implemented Interfaces:

MeterBinder

public final class NullEntryCache
extends EntryCache<EntryCacheCfg>

Implementation of the EntryCache following the null object pattern.

Field Summary

Fields inherited from class org.opends.server.api.MonitorProvider

registry

Constructor Summary

Constructors

Constructor	Description
NullEntryCache()

Method Summary

Modifier and Type	Method	Description
void	clear()	Removes all entries from the cache.
void	clearBackend(String backendID)	Removes all entries from the cache that are associated with the provided backend.
boolean	containsEntry(Dn entryDN)	Indicates whether the entry cache currently contains the entry with the specified DN.
void	finalizeEntryCache()	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.
SizedEntry	getEntry(Dn entryDN)	Retrieves the entry with its size, with the specified DN from the cache.
long	getEntryCount()	Retrieves the current number of entries stored within the cache.
Dn	getEntryDN(String backendID, long entryID)	Retrieves the entry DN for the entry with the specified ID on the specific backend from the cache.
static EntryCache<?>	getInstance()	Returns the null entry cache instance.
void	handleLowMemory()	Attempts to react to a scenario in which it is determined that the system is running low on available memory.
void	putEntry(SizedEntry entry, String backendID, long entryID)	Stores the provided entry in the cache.
boolean	putEntryIfAbsent(SizedEntry entry, String backendID, long entryID)	Stores the provided entry in the cache only if it does not conflict with an entry that already exists.
void	removeEntry(Dn entryDN)	Removes the specified entry from the cache.
String	toVerboseString()	Return a verbose string representation of the current cache maps.

Methods inherited from class org.opends.server.api.EntryCache

addMonitorObjectClassNames, bindTo, computeMonitorInstanceDn, filtersAllowCaching, getEntry, getServerContext, initializeEntryCache, isConfigurationAcceptable, newMeterRegistryHolder, recordMiss, recordTry, setIncludeExcludeFilters

Methods inherited from class org.opends.server.api.MonitorProvider

configurationDnToMonitorDn, deregisterAll, getMonitorEntry, getMonitorInstanceDn, toString

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

NullEntryCache

public NullEntryCache()

Method Detail

getInstance

public static EntryCache<?> getInstance()

Returns the null entry cache instance.

Returns:

the null entry cache instance.

clear

public void clear()

Description copied from class: EntryCache

Removes all entries from the cache. The cache should still be available for future use.

Specified by:

clear in class EntryCache<EntryCacheCfg>

clearBackend

public void clearBackend(String backendID)

Description copied from class: EntryCache

Removes all entries from the cache that are associated with the provided backend.

Specified by:

clearBackend in class EntryCache<EntryCacheCfg>

Parameters:

backendID - ID of the backend for which to flush the associated entries.

containsEntry

public boolean containsEntry(Dn entryDN)

Description copied from class: EntryCache

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)

Specified by:

containsEntry in class EntryCache<EntryCacheCfg>

Parameters:

entryDN - The DN for which to make the determination.

Returns:

true if the entry cache currently contains the entry with the specified DN, or false if not.

finalizeEntryCache

public void finalizeEntryCache()

Description copied from class: EntryCache

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.

Specified by:

finalizeEntryCache in class EntryCache<EntryCacheCfg>

getEntry

public SizedEntry getEntry(Dn entryDN)

Description copied from class: EntryCache

Retrieves the entry with its size, with the specified DN from the cache.

Specified by:

getEntry in class EntryCache<EntryCacheCfg>

Parameters:

entryDN - The DN of the entry to retrieve.

Returns:

The requested entry with its size if it is present in the cache, or null if it is not present.

getEntryCount

public long getEntryCount()

Description copied from class: EntryCache

Retrieves the current number of entries stored within the cache.

Specified by:

getEntryCount in class EntryCache<EntryCacheCfg>

Returns:

The current number of entries stored within the cache.

getEntryDN

public Dn getEntryDN(String backendID,
                     long entryID)

Description copied from class: EntryCache

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)

Specified by:

getEntryDN in class EntryCache<EntryCacheCfg>

Parameters:

backendID - ID of the backend associated with the entry for which to retrieve the entry DN.

entryID - The entry ID within the provided backend for which to retrieve the entry DN.

Returns:

The entry DN for the requested entry, or null if it is not present in the cache.

handleLowMemory

public void handleLowMemory()

Description copied from class: EntryCache

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.

Specified by:

handleLowMemory in class EntryCache<EntryCacheCfg>

putEntry

public void putEntry(SizedEntry entry,
                     String backendID,
                     long entryID)

Description copied from class: EntryCache

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.

Specified by:

putEntry in class EntryCache<EntryCacheCfg>

Parameters:

entry - The entry to store in the cache.

backendID - ID of the backend with which the entry is associated.

entryID - The entry ID within the provided backend that uniquely identifies the specified entry.

putEntryIfAbsent

public boolean putEntryIfAbsent(SizedEntry entry,
                                String backendID,
                                long entryID)

Description copied from class: EntryCache

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.

Specified by:

putEntryIfAbsent in class EntryCache<EntryCacheCfg>

Parameters:

entry - The entry to store in the cache.

backendID - ID of the backend with which the entry is associated.

entryID - The entry ID within the provided backend that uniquely identifies the specified entry.

Returns:

false if an existing entry or some other problem prevented the method from completing successfully, or true 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.

removeEntry

public void removeEntry(Dn entryDN)

Description copied from class: EntryCache

Removes the specified entry from the cache.

Specified by:

removeEntry in class EntryCache<EntryCacheCfg>

Parameters:

entryDN - The DN of the entry to remove from the cache.

toVerboseString

public String toVerboseString()

Description copied from class: EntryCache

Return a verbose string representation of the current cache maps. This is useful primary for debugging and diagnostic purposes such as in the entry cache unit tests.

This method is invoked by unit tests for debugging.

Specified by:

toVerboseString in class EntryCache<EntryCacheCfg>

Returns:

String verbose string representation of the current cache maps in the following format: dn:id:backend one cache entry map representation per line or null if all maps are empty.