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   // On scheduled updates, outdated VersionedCaches are also closed automatically.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(com.metamx.emitter.service.ServiceEmitter serviceEmitter, Map<Class<? extends ExtractionNamespace>,ExtractionNamespaceCacheFactory<?>> namespacePopulatorMap, 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 ExtractionNamespaceCacheFactory.populateCache(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(com.metamx.emitter.service.ServiceEmitter serviceEmitter,
                              Map<Class<? extends ExtractionNamespace>,ExtractionNamespaceCacheFactory<?>> namespacePopulatorMap,
                              NamespaceExtractionCacheManager cacheManager)

Method Detail

createVersionedCache

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

This method should be used from ExtractionNamespaceCacheFactory.populateCache(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)