io.druid.server.lookup.namespace.cache

Class CacheScheduler

java.lang.Object

io.druid.server.lookup.namespace.cache.CacheScheduler

public final class CacheScheduler
extends Object

Usage:

 CacheScheduler.Entry entry = cacheScheduler.schedule(namespace); // or scheduleAndWait(namespace, timeout)
 CacheState cacheState = entry.getCacheState();
 // cacheState could be either NoCache or VersionedCache.
 if (cacheState instanceof NoCache) {
   // the cache is not yet created, or already closed
 } else if (cacheState instanceof VersionedCache) {
   Map<String, String> cache = ((VersionedCache) cacheState).getCache(); // use the cache
   // Although VersionedCache implements AutoCloseable, versionedCache shouldn't be manually closed
   // when obtained from entry.getCacheState(). If the namespace updates should be ceased completely,
   // entry.close() (see below) should be called, it will close the last VersionedCache itself.
   // On scheduled updates, outdated VersionedCaches are also closed automatically.
 }
 ...
 entry.close(); // close the last VersionedCache and unschedule future updates
 

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static interface	CacheScheduler.CacheState
class	CacheScheduler.Entry<T extends ExtractionNamespace>
class	CacheScheduler.EntryImpl<T extends ExtractionNamespace> This class effectively contains the whole state and most of the logic of CacheScheduler.Entry, need to be a separate class because the Entry must not be referenced from the runnable executed in cacheManager's ExecutorService, that would be a leak preventing the Entry to be collected by GC, and therefore CacheScheduler.EntryImpl.entryCleaner to be run by the JVM.
static class	CacheScheduler.NoCache
class	CacheScheduler.VersionedCache

Constructor Summary

Constructors

Constructor and Description
CacheScheduler(ServiceEmitter serviceEmitter, Map<Class<? extends ExtractionNamespace>,CacheGenerator<?>> namespaceGeneratorMap, NamespaceExtractionCacheManager cacheManager)

Method Summary

Modifier and Type	Method and Description
CacheScheduler.VersionedCache	createVersionedCache(CacheScheduler.EntryImpl<? extends ExtractionNamespace> entryId, String version) This method should be used from CacheGenerator.generateCache(T, io.druid.server.lookup.namespace.cache.CacheScheduler.EntryImpl<T>, java.lang.String, io.druid.server.lookup.namespace.cache.CacheScheduler) implementations, to obtain a CacheScheduler.VersionedCache to be returned.
long	getActiveEntries()
<T extends ExtractionNamespace> CacheScheduler.Entry	schedule(T namespace)
CacheScheduler.Entry	scheduleAndWait(ExtractionNamespace namespace, long waitForFirstRunMs)

Methods inherited from class java.lang.Object

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

Constructor Detail

CacheScheduler

@Inject
public CacheScheduler(ServiceEmitter serviceEmitter,
                              Map<Class<? extends ExtractionNamespace>,CacheGenerator<?>> namespaceGeneratorMap,
                              NamespaceExtractionCacheManager cacheManager)

Method Detail

createVersionedCache

public CacheScheduler.VersionedCache createVersionedCache(@Nullable
                                                          CacheScheduler.EntryImpl<? extends ExtractionNamespace> entryId,
                                                          String version)

This method should be used from CacheGenerator.generateCache(T, io.druid.server.lookup.namespace.cache.CacheScheduler.EntryImpl<T>, java.lang.String, io.druid.server.lookup.namespace.cache.CacheScheduler) implementations, to obtain a CacheScheduler.VersionedCache to be returned.

Parameters:

entryId - an object uniquely corresponding to the CacheScheduler.Entry, for which VersionedCache is created

version - version, associated with the cache

getActiveEntries

public long getActiveEntries()

scheduleAndWait

@Nullable
public CacheScheduler.Entry scheduleAndWait(ExtractionNamespace namespace,
                                                      long waitForFirstRunMs)
                                               throws InterruptedException

Throws:

InterruptedException

schedule

public <T extends ExtractionNamespace> CacheScheduler.Entry schedule(T namespace)