Package 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.

    • Method Detail

      • startTracking

        void startTracking​(org.apache.flink.runtime.state.StreamStateHandle handle,
                   long refCount)
        Start tracking the state uploaded. The refCount is the number of StateChangeSets.

      • stopTracking

        void stopTracking​(org.apache.flink.runtime.state.StreamStateHandle handle)
        Stop tracking the state, so that it's not tracked (some other component is doing that).

      • release

        void release​(org.apache.flink.runtime.state.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)