Package org.apache.flink.runtime.checkpoint

Class CompletedCheckpoint

  • All Implemented Interfaces:
    Serializable, Checkpoint
    @NotThreadSafe
public class CompletedCheckpoint
extends Object
implements Serializable, Checkpoint
    A CompletedCheckpoint describes a checkpoint after all required tasks acknowledged it (with their state) and that is considered successful. The CompletedCheckpoint class contains all the metadata of the checkpoint, i.e., checkpoint ID, timestamps, and the handles to all states that are part of the checkpoint.

    Size the CompletedCheckpoint Instances

    In most cases, the CompletedCheckpoint objects are very small, because the handles to the checkpoint states are only pointers (such as file paths). However, the some state backend implementations may choose to store some payload data directly with the metadata (for example to avoid many small files). If those thresholds are increased to large values, the memory consumption of the CompletedCheckpoint objects can be significant.

    Metadata Persistence

    The metadata of the CompletedCheckpoint is also persisted in an external storage system. Checkpoints have an external pointer, which points to the metadata. For example when storing a checkpoint in a file system, that pointer is the file path to the checkpoint's folder or the metadata file. For a state backend that stores metadata in database tables, the pointer could be the table name and row key. The pointer is encoded as a String.

    See Also:
    Serialized Form