Package com.apple.foundationdb.record.provider.foundationdb

Interface MetaDataCache

@API(EXPERIMENTAL)
public interface MetaDataCache

A caching hook for FDBMetaDataStore. A cache implementation can implement any subset of object, serialized and version cached. The caller is responsible for calling all of the relevant the set methods when something changes.

Note that this interface is currently undergoing active development. Work on evolving this API is currently being tracked as part of Issue #280. Users are advised to avoid implementing or using this interface until work on that issue has been completed.

Method Summary

Modifier and Type	Method	Description
default RecordMetaData	getCachedMetaData()	Get cached RecordMetaData object.
default byte[]	getCachedSerialized()	Get cached serialized meta-data.
default CompletableFuture<Integer>	getCurrentVersionAsync(FDBRecordContext context)	Get a version to use for cache validation of -1 to skip validation.
default void	setCachedMetaData(RecordMetaData metaData)	Cache meta-data object.
default void	setCachedSerialized(byte[] serialized)	Cache serialized meta-data.
default void	setCurrentVersion(FDBRecordContext context, int version)	Update the version used for cache validation.

Method Detail

getCurrentVersionAsync

default CompletableFuture<Integer> getCurrentVersionAsync(FDBRecordContext context)

Get a version to use for cache validation of -1 to skip validation.

Parameters:

context - the transaction to use to access the database

Returns:

a future that completes with the current version

getCachedMetaData

@Nullable
default RecordMetaData getCachedMetaData()

Get cached RecordMetaData object. For instance, from a Guava cache.

Returns:

any cached meta-data

getCachedSerialized

@Nullable
default byte[] getCachedSerialized()

Get cached serialized meta-data. For instance, from Memcache.

Returns:

any cached serialized form

setCurrentVersion

default void setCurrentVersion(FDBRecordContext context,
                               int version)

Update the version used for cache validation.

If maintained, the version should be stored in a way that is transactionally consistent with the given context. For instance, in one or more key-value pairs.

Parameters:

context - the transaction to use to access the database

version - the new current version

See Also:

getCurrentVersionAsync(FDBRecordContext)

setCachedMetaData

default void setCachedMetaData(@Nonnull
                               RecordMetaData metaData)

Cache meta-data object.

This cache can be kept in memory. If setCurrentVersion(com.apple.foundationdb.record.provider.foundationdb.FDBRecordContext, int) is supported, it is still possible to determine when it is out-of-date, even if changed by some other client.

Parameters:

metaData - the new cached meta-data

See Also:

getCachedMetaData()

setCachedSerialized

default void setCachedSerialized(@Nonnull
                                 byte[] serialized)

Cache serialized meta-data.

This cache is normally maintained some place that is not transationally consistent. In which case, if multiple clients can change the meta-data, setCurrentVersion(com.apple.foundationdb.record.provider.foundationdb.FDBRecordContext, int) should also be supported.

Parameters:

serialized - the new cached serialized meta-data

See Also:

getCachedSerialized()