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trait CheckpointFileManager extends AnyRef

An interface to abstract out all operation related to streaming checkpoints. Most importantly, the key operation this interface provides is createAtomic(path, overwrite) which returns a CancellableFSDataOutputStream. This method is used by HDFSMetadataLog and StateStore implementations to write a complete checkpoint file atomically (i.e. no partial file will be visible), with or without overwrite.

This higher-level interface above the Hadoop FileSystem is necessary because different implementation of FileSystem/FileContext may have different combination of operations to provide the desired atomic guarantees (e.g. write-to-temp-file-and-rename, direct-write-and-cancel-on-failure) and this abstraction allow different implementations while keeping the usage simple (createAtomic -> close or cancel).

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FileContextBasedCheckpointFileManager, FileSystemBasedCheckpointFileManager
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Abstract Value Members

  1. abstract def createAtomic(path: Path, overwriteIfPossible: Boolean): CancellableFSDataOutputStream

    Create a file and make its contents available atomically after the output stream is closed.

    Create a file and make its contents available atomically after the output stream is closed.

    path

    Path to create

    overwriteIfPossible

    If true, then the implementations must do a best-effort attempt to overwrite the file if it already exists. It should not throw any exception if the file exists. However, if false, then the implementation must not overwrite if the file already exists and must throw FileAlreadyExistsException in that case.

  2. abstract def delete(path: Path): Unit

    Recursively delete a path if it exists.

    Recursively delete a path if it exists. Should not throw exception if file doesn't exist.

  3. abstract def exists(path: Path): Boolean

    Whether path exists

  4. abstract def isLocal: Boolean

    Is the default file system this implementation is operating on the local file system.

  5. abstract def list(path: Path, filter: PathFilter): Array[FileStatus]

    List the files in a path that match a filter.

  6. abstract def mkdirs(path: Path): Unit

    Make directory at the give path and all its parent directories as needed.

  7. abstract def open(path: Path): FSDataInputStream

    Open a file for reading, or throw exception if it does not exist.

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  12. def list(path: Path): Array[FileStatus]

    List all the files in a path.

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