org.apache.druid.query.lookup.namespace

Interface CacheGenerator<T extends ExtractionNamespace>

All Known Implementing Classes:

JdbcCacheGenerator, StaticMapCacheGenerator, UriCacheGenerator

public interface CacheGenerator<T extends ExtractionNamespace>

Method Summary

Modifier and Type

Method and Description

CacheScheduler.VersionedCache

generateCache(T namespace, CacheScheduler.EntryImpl<T> id, String lastVersion, CacheScheduler scheduler) If the lookup source, encapsulated by this CacheGenerator, has data newer than identified by the given lastVersion (which is null at the first run of this method, or the version from the previous run), this method creates a new CacheScheduler.VersionedCache with CacheScheduler.createVersionedCache(org.apache.druid.server.lookup.namespace.cache.CacheScheduler.EntryImpl<? extends org.apache.druid.query.lookup.namespace.ExtractionNamespace>, java.lang.String), called on the given scheduler, with the version string identifying the current version of lookup source, populates the created VersionedCache and returns it.

Method Detail

generateCache

@Nullable
CacheScheduler.VersionedCache generateCache(T namespace,
                                                      CacheScheduler.EntryImpl<T> id,
                                                      String lastVersion,
                                                      CacheScheduler scheduler)
                                               throws Exception

If the lookup source, encapsulated by this CacheGenerator, has data newer than identified by the given lastVersion (which is null at the first run of this method, or the version from the previous run), this method creates a new CacheScheduler.VersionedCache with CacheScheduler.createVersionedCache(org.apache.druid.server.lookup.namespace.cache.CacheScheduler.EntryImpl<? extends org.apache.druid.query.lookup.namespace.ExtractionNamespace>, java.lang.String), called on the given scheduler, with the version string identifying the current version of lookup source, populates the created VersionedCache and returns it. If the lookup source is up-to-date, this methods returns null.

Parameters:

namespace - The ExtractionNamespace for which to generate cache.

id - An object uniquely corresponding to the CacheScheduler.Entry, for which this generateCache() method is called. Also it has the same toString() representation, that is useful for logging

lastVersion - The version which was last cached

scheduler - Should be used only to call CacheScheduler.createVersionedCache(org.apache.druid.server.lookup.namespace.cache.CacheScheduler.EntryImpl<? extends org.apache.druid.query.lookup.namespace.ExtractionNamespace>, java.lang.String).

Returns:

the new cache along with the new version, or null if the last version is up-to-date.

Throws:

Exception