org.apache.flink.changelog.fs

Interface TaskChangelogRegistry

@Internal
public interface TaskChangelogRegistry

TM-side registry of StateObjects, each representing one or more changelog segments. Changelog segments are uploaded by StateChangelogWriters of a StateChangelogStorage.

Initially, when starting the tracking, the ownership of a changelog segments is not clear, and it is assumed that JM might be the owner. The refCount of the StateObject refers to the number of changelog segments contains in the StateObject. release(StreamStateHandle) should be called when every changelog segment become not used, and it will count down the refCount by one. Once the refCount reaches zero, JM can not become an owner anymore, the state is discarded.

However, if at any point it becomes known that JM is the owner, tracking is stopped and the state will not be discarded.

It is the client responsibility to call release(StreamStateHandle) when every corresponding changelog segment becomes not used.

Field Summary

Fields

Modifier and Type	Field and Description
static TaskChangelogRegistry	NO_OP

Method Summary

Modifier and Type	Method and Description
static TaskChangelogRegistry	defaultChangelogRegistry(Executor executor)
static TaskChangelogRegistry	defaultChangelogRegistry(int numAsyncDiscardThreads)
void	release(StreamStateHandle handle) Decrease the reference count of the state by one, e.g.
void	startTracking(StreamStateHandle handle, long refCount) Start tracking the state uploaded.
void	stopTracking(StreamStateHandle handle) Stop tracking the state, so that it's not tracked (some other component is doing that).

Field Detail

NO_OP

static final TaskChangelogRegistry NO_OP

Method Detail

startTracking

void startTracking(StreamStateHandle handle,
                   long refCount)

Start tracking the state uploaded. The refCount is the number of StateChangeSets.

stopTracking

void stopTracking(StreamStateHandle handle)

Stop tracking the state, so that it's not tracked (some other component is doing that).

release

void release(StreamStateHandle handle)

Decrease the reference count of the state by one, e.g. if it was pre-emptively uploaded and materialized. Once the reference count reaches zero, it is discarded (unless it was unregistered earlier).

defaultChangelogRegistry

static TaskChangelogRegistry defaultChangelogRegistry(int numAsyncDiscardThreads)

defaultChangelogRegistry

@VisibleForTesting
static TaskChangelogRegistry defaultChangelogRegistry(Executor executor)