org.apache.samza.storage

Interface StorageEngine

public interface StorageEngine

A storage engine for managing state maintained by a stream processor.

This interface does not specify any query capabilities, which, of course, would be query engine specific. Instead it just specifies the minimum functionality required to reload a storage engine from its changelog as well as basic lifecycle management.

Method Summary

Modifier and Type	Method and Description
java.util.Optional<java.nio.file.Path>	checkpoint(CheckpointId id) Checkpoint store snapshots.
void	flush() Flush any cached messages
StoreProperties	getStoreProperties() Get store properties
void	restore(ChangelogSSPIterator envelopes) Restore the content of this StorageEngine from the changelog.
void	stop() Close the storage engine

Method Detail

restore

void restore(ChangelogSSPIterator envelopes)
      throws java.lang.InterruptedException

Restore the content of this StorageEngine from the changelog. Messages are provided in one Iterator and not deserialized for efficiency, allowing the implementation to optimize replay, if possible. The implementers are expected to handle interrupt signals to the restoration thread and rethrow the exception to upstream so that TaskRestoreManager can accordingly notify the container.

Parameters:

envelopes - An iterator of envelopes that the storage engine can read from to restore its state on startup.

Throws:

java.lang.InterruptedException - when received interrupts during restoration

flush

void flush()

Flush any cached messages

checkpoint

@InterfaceStability.Unstable
java.util.Optional<java.nio.file.Path> checkpoint(CheckpointId id)

Checkpoint store snapshots.

stop

void stop()

Close the storage engine

getStoreProperties

StoreProperties getStoreProperties()

Get store properties

Returns:

store properties