* Lookup cache refactoring (the main part of druid-io/druid#3667)
* Use PowerMock's static methods in NamespaceLookupExtractorFactoryTest
* Fix KafkaLookupExtractorFactoryTest
* Use VisibleForTesting annotation instead of Javadoc comment
* Create a NamespaceExtractionCacheManager separately for each test in NamespaceExtractionCacheManagersTest
* Rename CacheScheduler.NoCache.ENTRY_DISPOSED to ENTRY_CLOSED
* Reduce visibility of NamespaceExtractionCacheManager.cacheCount() and monitor() implementations, and don't run NamespaceExtractionCacheManagerExecutorsTest with off-heap cache (it didn't before)
* In NamespaceLookupExtractorFactory, use safer idiom to check if CacheState is NoCache or VersionedCache
* More logging in CacheHandler constructor and close(), VersionedCache.close()
* PR comments addressed
* Make CacheScheduler.EntryImpl AutoCloseable, avoid 'dispose' verb in comments, logging and naming in CacheScheduler in favor of 'close'
* More Javadoc comments to CacheScheduler
* Fix NPE
* Remove logging in OnHeapNamespaceExtractionCacheManager.expungeCollectedCaches()
* Make NamespaceExtractionCacheManagersTest.testRacyCreation() to have similar load to what it be before the refactoring
* Unwrap NamespaceExtractionCacheManager.scheduledExecutorService from unneeded MoreExecutors.listeningDecorator() and specify that this is ScheduledThreadPoolExecutor, which ensures happens-before between periodic runs of the tasks
* More comments on MapDbCacheDisposer.disposed
* Replace concat with Long.toString()
* Comment on why NamespaceExtractionCacheManager.scheduledExecutorService() returns ScheduledThreadPoolExecutor
* Place logging statements in VersionedCache.close() and CacheHandler.close() after actual closing logic, because logging may fail
* Make JDBCExtractionNamespaceCacheFactory and StaticMapExtractionNamespaceCacheFactory to try to close newly created VersionedCache if population has failed, as it is done already in URIExtractionNamespaceCacheFactory
* Don't close the whole CacheScheduler.Entry, if the cache update task failed
* Replace AtomicLong updateCounter and firstRunLatch with Phaser-based UpdateCounter in CacheScheduler.EntryImpl
* support LookupReferencesManager registration of namespaced lookup and eliminate static configurations for lookup from namespecd lookup extensions
- druid-namespace-lookup and druid-kafka-extraction-namespace are modified
- However, druid-namespace-lookup still has configuration about ON/OFF
HEAP cache manager selection, which is not namespace wide
configuration but node wide configuration as multiple namespace shares
the same cache manager
* update KafkaExtractionNamespaceTest to reflect argument signature changes
* Add more synchronization functionality to NamespaceLookupExtractorFactory
* Remove old way of using extraction namespaces
* resolve compile error by supporting LookupIntrospectHandler
* Remove kafka lookups
* Remove unused stuff
* Fix start and stop behavior to be consistent with new javadocs
* Remove unused strings
* Add timeout option
* Address comments on configurations and improve docs
* Add more options and update hash key and replaces
* Move monitoring to the overriding classes
* Add better start/stop logging
* Remove old docs about namespace names
* Fix bad comma
* Add `@JsonIgnore` to lookup factory
* Address code review comments
* Remove ExtractionNamespace from module json registration
* Fix problems with naming and initialization. Add tests
* Optimize imports / reformat
* Fix future not being properly cancelled on failed initial scheduling
* Fix delete returns
* Add more docs about whole introspection
* Add `/version` introspection point for lookups
* Add more tests and address comments
* Add StaticMap extraction namespace for testing. Also add a bunch of tests
* Move cache system property to `druid.lookup.namespace.cache.type`
* Make VERSION lower case
* Change poll period to 0ms for StaticMap
* Move cache key to bytebuffer
* Change hashCode and equals on static map extraction fn
* Add more comments on StaticMap
* Address comments
* Make scheduleAndWait use a latch
* Sanity renames and fix imports
* Remove extra info in docs
* Fix review comments
* Strengthen failure on start from warn to error
* Address comments
* Rename namespace-lookup to lookups-cached-global
* Fix injective mis-naming
* Also add serde test
Roman Leventov
Gian Merlino
Charles Allen