Package org.apache.druid.metadata.segment.cache

Class NoopSegmentMetadataCache

java.lang.Object

org.apache.druid.metadata.segment.cache.NoopSegmentMetadataCache

All Implemented Interfaces:

SegmentMetadataCache

public class NoopSegmentMetadataCache
extends Object
implements SegmentMetadataCache

Nested Class Summary

Nested classes/interfaces inherited from interface org.apache.druid.metadata.segment.cache.SegmentMetadataCache

SegmentMetadataCache.Action<T>, SegmentMetadataCache.UsageMode

Constructor Summary

Constructors

Constructor	Description
NoopSegmentMetadataCache()

Method Summary

Modifier and Type	Method	Description
void	awaitNextSync(long timeoutMillis)	Waits until the cache finishes the next sync with the metadata store or until the timeout elapses, whichever is sooner.
void	becomeLeader()	Refreshes the cache once the service is elected leader.
DataSourcesSnapshot	getDataSourcesSnapshot()
static NoopSegmentMetadataCache	instance()
boolean	isEnabled()
boolean	isSyncedForRead()
<T> T	readCacheForDataSource(String dataSource, SegmentMetadataCache.Action<T> readAction)	Performs a thread-safe read action on the cache for the given datasource.
void	start()	Starts the cache on service start.
void	stop()	Stops the cache on service stop.
void	stopBeingLeader()	Notifies the cache that the service has lost leadership.
<T> T	writeCacheForDataSource(String dataSource, SegmentMetadataCache.Action<T> writeAction)	Performs a thread-safe write action on the cache for the given datasource.

Methods inherited from class java.lang.Object

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

Constructor Details

NoopSegmentMetadataCache

public NoopSegmentMetadataCache()

Method Details

instance

public static NoopSegmentMetadataCache instance()

start

public void start()

Description copied from interface: SegmentMetadataCache

Starts the cache on service start.

Specified by:

start in interface SegmentMetadataCache

stop

public void stop()

Description copied from interface: SegmentMetadataCache

Stops the cache on service stop.

Specified by:

stop in interface SegmentMetadataCache

becomeLeader

public void becomeLeader()

Description copied from interface: SegmentMetadataCache

Refreshes the cache once the service is elected leader.

Specified by:

becomeLeader in interface SegmentMetadataCache

stopBeingLeader

public void stopBeingLeader()

Description copied from interface: SegmentMetadataCache

Notifies the cache that the service has lost leadership.

Specified by:

stopBeingLeader in interface SegmentMetadataCache

isEnabled

public boolean isEnabled()

Specified by:

isEnabled in interface SegmentMetadataCache

Returns:

true if the cache is enabled

isSyncedForRead

public boolean isSyncedForRead()

Specified by:

isSyncedForRead in interface SegmentMetadataCache

Returns:

true if the cache is enabled and synced with the metadata store. Reads can be done from the cache only if it is synced but writes can happen even before the sync has finished.

awaitNextSync

public void awaitNextSync(long timeoutMillis)

Description copied from interface: SegmentMetadataCache

Waits until the cache finishes the next sync with the metadata store or until the timeout elapses, whichever is sooner.

Specified by:

awaitNextSync in interface SegmentMetadataCache

getDataSourcesSnapshot

public DataSourcesSnapshot getDataSourcesSnapshot()

Specified by:

getDataSourcesSnapshot in interface SegmentMetadataCache

Returns:

Latest snapshot of the datasources with all their used segments.

readCacheForDataSource

public <T> T readCacheForDataSource(String dataSource,
 SegmentMetadataCache.Action<T> readAction)

Description copied from interface: SegmentMetadataCache

Performs a thread-safe read action on the cache for the given datasource. Read actions can be concurrent with other reads but are mutually exclusive from other write actions on the same datasource.

Specified by:

readCacheForDataSource in interface SegmentMetadataCache

writeCacheForDataSource

public <T> T writeCacheForDataSource(String dataSource,
 SegmentMetadataCache.Action<T> writeAction)

Description copied from interface: SegmentMetadataCache

Performs a thread-safe write action on the cache for the given datasource. Write actions are mutually exclusive from other writes or reads on the same datasource.

Specified by:

writeCacheForDataSource in interface SegmentMetadataCache